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© 2005 HART Communication Foundation
Copyright © 1999-2005 HART Communication Foundation. All rights reserved. HART® is a registered trademark of the HART Communication Foundation. Any use of the word “HART” hereafter in this document implies the registered trademark. All other trademarks used in this document are acknowledged to be trademarks of their respective companies.
For additional information contact: HART Communication Foundation 9390 Research Boulevard Suite I-350 Austin, Texas 78759 USA Tel: 512-794-0369 Fax: 512-794-3904
HART APPLICATION GUIDE
Preface In today’s competitive environment, all companies seek to reduce operation costs, deliver products rapidly, and improve product quality. The HART® (highway addressable remote transducer) protocol directly contributes to these business goals by providing cost savings in: T Commissioning and installation T Plant operations and improved quality T Maintenance The HART Application Guide has been created by the HART Communication Foundation (HCF) to provide users of HART products with the information necessary to obtain the full benefits of HART digital instrumentation. The HART communication protocol is an open standard owned by the more than 100 member companies in the HCF. Products that use the HART protocol to provide both analog 4–20 mA and digital signals provide flexibility not available with any other communication technology. The following four sections provide you with an understanding of how the HART technology works, insight on how to apply various features of the technology, and specific examples of applications implemented by HART protocol users around the world: T Theory of Operation3 T Benefits of HART Communications T Getting the Most out of HART Systems T Industry Applications
© 2003 HART Communication Foundation
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THEORY OF OPERATION
Theory of Operation The following sections explain the basic principles behind the operation of HART instruments and networks: T Communication Modes T Frequency Shift Keying T HART Networks T HART Commands
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THEORY OF OPERATION
Communication Modes MASTER-SLAVE MODE
HART is a master-slave communication protocol, which means that during normal operation, each slave (field device) communication is initiated by a master communication device. Two masters can connect to each HART loop. The primary master is generally a distributed control system (DCS), programmable logic controller (PLC), or a personal computer (PC). The secondary master can be a handheld terminal or another PC. Slave devices include transmitters, actuators, and controllers that respond to commands from the primary or secondary master.
BURST MODE
Some HART devices support the optional burst communication mode. Burst mode enables faster communication (3–4 data updates per second). In burst mode, the master instructs the slave device to continuously broadcast a standard HART reply message (e.g., the value of the process variable). The master receives the message at the higher rate until it instructs the slave to stop bursting. Use burst mode to enable more than one passive HART device to listen to communications on the HART loop.
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THEORY OF OPERATION
Frequency Shift Keying The HART communication protocol is based on the Bell 202 telephone communication standard and operates using the frequency shift keying (FSK) principle. The digital signal is made up of two frequencies— 1,200 Hz and 2,200 Hz representing bits 1 and 0, respectively. Sine waves of these two frequencies are superimposed on the direct current (dc) analog signal cables to provide simultaneous analog and digital communications (Figure 1). Because the average value of the FSK signal is always zero, the 4–20 mA analog signal is not affected. The digital communication signal has a response time of approximately 2–3 data updates per second without interrupting the analog signal. A minimum loop impedance of 230 Ω is required for communication.
20 mA Digital Signal
“1”
“0”
“0”
“1”
“1”
“0”
“1”
“1”
“0”
Analog Signal
4 mA
Time Note: Drawing not to scale.
Figure 1: Simultaneous Analog and Digital Communication
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THEORY OF OPERATION
HART Networks HART devices can operate in one of two network configurations—point to point or multidrop.
POINT-TO-POINT
In point-to-point mode, the traditional 4–20 mA signal is used to communicate one process variable, while additional process variables, configuration parameters, and other device data are transferred digitally using the HART protocol (Figure 2). The 4–20 mA analog signal is not affected by the HART signal and can be used for control in the normal way. The HART communication digital signal gives access to secondary variables and other data that can be used for operations, commissioning, maintenance, and diagnostic purposes.
Multiplexer
Control System or Other Host Application
Barrier
Handheld Terminal
Field Device
Note: Instrument power is provided by an interface or external power source that is not shown.
Figure 2: Point-to-Point Mode of Operation
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THEORY OF OPERATION
HART Networks MULTIDROP
The multidrop mode of operation requires only a single pair of wires and, if applicable, safety barriers and an auxiliary power supply for up to 15 field devices (Figure 3). All process values are transmitted digitally. In multidrop mode, all field device polling addresses are >0, and the current through each device is fixed to a minimum value (typically 4 mA). Use multidrop connection for supervisory control installations that are widely spaced, such as pipelines, custody transfer stations, and tank farms.
Control System or Other Host Application Handheld Terminal
Input/Output (I/O) System
Field Devices Note: Instrument power is provided by an interface or external power source that is not shown.
Figure 3: Multidrop Mode of Operation
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THEORY OF OPERATION
HART Commands The HART command set provides uniform and consistent communication for all field devices. The command set includes three classes: universal, common practice, and device specific (Table 1). Host applications may implement any of the necessary commands for a particular application.
UNIVERSAL
All devices using the HART protocol must recognize and support the universal commands. Universal commands provide access to information useful in normal operations (e.g., read primary variable and units).
COMMON PRACTICE
Common practice commands provide functions implemented by many, but not necessarily all, HART communication devices.
DEVICE SPECIFIC
Device-specific commands represent functions that are unique to each field device. These commands access setup and calibration information, as well as information about the construction of the device. Information on device-specific commands is available from device manufacturers.
SUMMARY TABLE Universal Commands
Common Practice Commands
Device-Specific Commands
• Read manufacturer and device type
• Read selection of up to four dynamic variables
• Read or write low-flow cut-off
• Read primary variable (PV) and units
• Write damping time constant
• Read or write density calibration factor
• Read current output and percent of range
• Calibrate (set zero, set span)
• Read up to four predefined dynamic variables
• Perform self-test
• Write device range values • Set fixed output current
• Perform master reset • Read or write eight-character tag, 16-character descriptor, • Trim PV zero • Write PV unit date • Trim DAC zero and gain • Read or write 32-character message • Write transfer function (square root/linear) • Read device range values, units, and damping time • Write sensor serial number constant • Read or write dynamic variable • Read or write final assembly assignments number
• Start, stop, or clear totalizer
• Choose PV (mass, flow, or density) • Read or write materials or construction information • Trim sensor calibration • PID enable • Write PID setpoint • Valve characterization • Valve setpoint • Travel limits • User units • Local display information
• Write polling address
Table 1: HART Commands
Note: Table 1 is a partial list of HART commands. See Appendices B, C, and D for more detailed information.
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THEORY OF OPERATION
HART Commands ESTABLISHING COMMUNICATION WITH A HART DEVICE
Each HART device has a 38-bit address that consists of the manufacturer ID code, device type code, and device-unique identifier. A unique address is encoded in each device at the time of manufacture. A HART master must know the address of a field device in order to communicate successfully with it. A master can learn the address of a slave device by issuing one of two commands that cause the slave device to respond with its address: T Command 0, Read Unique Identifier—Command 0 is the preferred method for initiating communication with a slave device because it enables a master to learn the address of each slave device without user interaction. Each polling address (0–15) is probed to learn the unique address for each device. T Command 11, Read Unique Identifier by Tag - Command 11 is useful if there are more than 15 devices in the network or if the network devices were not configured with unique polling addresses. (Multidropping more than 15 devices is possible when the devices are individually powered and isolated.) Command 11 requires the user to specify the tag numbers to be polled.
DEVICE DESCRIPTION
Some HART host applications use device descriptions (DD) to obtain information about the variables and functions contained in a HART field device. The DD includes all of the information needed by a host application to fully communicate with the field device. HART Device Description Language (DDL) is used to write the DD, that combines all of the information needed by the host application into a single structured file. The DD identifies which common practice commands are supported as well as the format and structure of all device-specific commands. A DD for a HART field device is roughly equivalent to a printer driver for a computer. DDs eliminate the need for host suppliers to develop and support custom interfaces and drivers. A DD provides a picture of all parameters and functions of a device in a standardized language. HART suppliers have the option of supplying a DD for their HART field product. If they choose to supply one, the DD will provide information for a DD-enabled host application to read and write data according to each device’s procedures. DD source files for HART devices resemble files written in the C programming language. DD files are submitted to the HCF for registration in the HCF DD Library. Quality checks are performed on each DD submitted to ensure specification compliance, to verify that there are no conflicts with DDs already registered, and to verify operation with standard HART hosts. The HCF DD Library is the central location for management and distribution of all HART DDs to facilitate use in host applications such as PCs and handheld terminals. Additional information, not provided by the DD, may be required by some host applications for screen formatting and other uses.
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BENEFITS OF HART COMMUNICATIONS
Benefits of HART Communications The HART protocol is a powerful communication technology used to exploit the full potential of digital field devices. Preserving the traditional 4–20 mA signal, the HART protocol extends system capabilities for two-way digital communication with smart field instruments. The HART protocol offers the best solution for smart field device communications and has the widest base of support of any field device protocol worldwide. More instruments are available with the HART protocol than any other digital communications technology. Almost any process application can be addressed by one of the products offered by HART instrument suppliers. Unlike other digital communication technologies, the HART protocol provides a unique communication solution that is backward compatible with the installed base of instrumentation in use today. This backward compatibility ensures that investments in existing cabling and current control strategies will remain secure well into the future. Benefits outlined in this section include: T Improved plant operations T Operational flexibility T Instrumentation investment protection T Digital communication
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BENEFITS OF HART COMMUNICATIONS
Improved Plant Operations The HART protocol improves plant performance and increases efficiencies in : T Commissioning and installation T Plant operations T Maintenance
COST SAVINGS IN COMMISSIONING
HART-based field devices can be installed and commissioned in a fraction of the time required for a traditional analog-only system. Operators who use HART digital communications can easily identify a field device by its tag and verify that operational parameters are correct. Configurations of similar devices can be copied to streamline the commissioning process. A loop integrity check is readily accomplished by commanding the field transmitter to set the analog output to a preset value.
COST SAVINGS IN INSTALLATION
The HART protocol supports the networking of several devices on a single twisted wire pair. This configuration can provide significant savings in wiring, especially for applications such as tank monitoring. Use HART multidrop mode to connect multiple instruments to a single cable and reduce installation costs.
Multivariable devices reduce the number of instruments, wiring, spare parts, and terminations required. Some HART field instruments embed PID control, which eliminates the need for a separate controller, and results in significant wiring and equipment cost savings.
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BENEFITS OF HART COMMUNICATIONS
Improved Plant Operations IMPROVED MEASUREMENT QUALITY
HART-communicating devices provide accurate information that helps improve the efficiency of plant operations. During normal operation, device operational values can be easily monitored or modified remotely. If uploaded to a software application, these data can be used to automate record keeping for regulatory compliance (e.g., environmental, validation, ISO9000, and safety standards). Numerous device parameters are available from HART-compatible instruments that can be communicated to the control room and used for control, maintenance, and record keeping (Figure 4). Field Device
Control Room
Figure 4: Examples of Device Parameters Sent to Control Room
Some HART devices perform complex calculations, such as PID control algorithms or compensated flow rate. Multivariable HART-capable instruments take measurements and perform calculations at the source, which eliminates time bias and results in more accurate calculations than are possible when performed in a centralized host. The HART protocol provides access to all information in multivariable devices. In addition to the analog output (primary variable), the HART protocol provides access to all measurement data that can be used for verification or calculation of plant mass and energy balances.
Some HART field devices store historical information in the form of trend logs and summary data. These logs and statistical calculations (e.g., high and low values and averages) can be uploaded into a software application for further processing or record keeping.
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BENEFITS OF HART COMMUNICATIONS
Improved Plant Operations COST SAVINGS IN MAINTENANCE
The diagnostic capabilities of HART-communicating field devices can eliminate substantial costs by reducing downtime. The HART protocol communicates diagnostic information to the control room, which minimizes the time required to identify the source of any problem and take corrective action. Trips into the field or hazardous areas are eliminated or reduced. When a replacement device is put into service, HART communication allows the correct operational parameters and settings to be quickly and accurately uploaded into the device from a central database. Efficient and rapid uploading reduces the time that the device is out of service. Some software applications provide a historical record of configuration and operational status for each instrument. This information can be used for predictive, preventive, and proactive maintenance.
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BENEFITS OF HART COMMUNICATIONS
Operational Flexibility The HART protocol allows two masters (primary and secondary) to communicate with slave devices and provide additional operational flexibility. A permanently connected host system can be used simultaneously, while a handheld terminal or PC controller is communicating with a field device (Figure 5). HART Interface
Analog Digital Data (2–3 updates per second)
Primary Master: Control System or Other Host Application
Power Supply Transmitter Secondary Master
Figure 5: Multimaster System
The HART protocol ensures interoperablility among devices through universal commands that enable hosts to easily access and communicate the most common parameters used in field devices. The HART DDL extends interoperability to include information that may be specific to a particular device. DDL enables a single handheld configurator or PC host application to configure and maintain HART-communicating devices from any manufacturer. The use of common tools for products of different vendors minimizes the amount of equipment and training needed to maintain a plant. HART extends the capability of field devices beyond the single-variable limitations of 4–20 mA in hosts with HART capability.
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BENEFITS OF HART COMMUNICATIONS
Instrumentation Investment Protection Existing plants and processes have considerable investments in wiring, analog controllers, junction boxes, barriers, marshalling panels, and analog or smart instrumentation. The people, procedures, and equipment already exist for the support and maintenance of the installed equipment. HART field instruments protect this investment by providing compatible products with enhanced digital capabilities. These enhanced capabilities can be used incrementally. The HART communication protocol enables you to retain your previous investments in existing hardware and personnel.
At the basic level, HART devices communicate with a handheld terminal for setup and maintenance. As needs grow, more sophisticated, on-line, PC-based systems can provide continuous monitoring of device status and configuration parameters. Advanced installations can also use control systems with HART I/O capability. The status information can be used directly by control schemes to trigger remedial actions and allow on-line reranging based on operating conditions and direct reading of multivariable instrument data.
COMPATIBILITY OF HART REVISIONS
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As HART field devices are upgraded, new functions may be added. A basic premise of the HART Protocol is that new HART instruments must behave in precisely the same manner as older versions when interfaced with an earlier revision host system.
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BENEFITS OF HART COMMUNICATIONS
Digital Communication A digital instrument that uses a microprocessor provides many benefits. These benefits are found in all smart devices regardless of the type of communication used. A digital device provides advantages such as improved accuracy and stability. The HART protocol enhances the capabilities of digital instruments by providing communication access and networking (Table 2). Benefits Accuracy and stability Reliability Multivariable Computations Diagnostics Multiple sensor inputs Ease of commissioning Tag ID Remote configuration Loop checks Adjustable operational parameters Access to historical data Multidrop networking Access by multiple host devices Extended communication distances Field-based control Interoperability
HART Instruments
Digital Instruments
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
✓ ✓ ✓ ✓ ✓ ✓
Table 2: Digital Instruments Versus HART Instruments
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GETTING THE MOST OUT OF HART SYSTEMS
Getting the Most out of HART Systems To take full advantage of the benefits offered by the HART communication protocol, it is important that you install and implement the system correctly. The following sections contain information that can help you to get the most from your HART system: T Wiring and Installation T Intrinsic safety T HART multidrop networks T Control system interfaces T Multiplexers T Reading HART data into nonHART systems T Universal handheld communicator T PC configuration software T Commissioning HART networks T Device status and diagnostics T Connecting a PC to a HART device or network T PC application development tools T Control in field devices
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GETTING THE MOST OUT OF HART SYSTEMS
Wiring and Installation In general, the installation practice for HART communicating devices is the same as conventional 4-20mA instrumentation. Individually shielded twisted pair cable, either in single-pair or multi-pair varieties, is the recommended wiring practice. Unshielded cables may be used for short distances if ambient noise and cross-talk will not affect communication. The minimum conductor size is 0.51 mm diameter (#24 AWG) for cable runs less than 1,524 m (5,000 ft) and 0.81 mm diameter (#20 AWG) for longer distances.
CABLE LENGTH
Most installations are well within the 3,000 meter (10,000 ft) theoretical limit for HART communication. However, the electrical characteristics of the cable (mostly capacitance) and the combination of connected devices can affect the maximum allowable cable length of a HART network. Table 3 shows the affect of cable capacitance and the number of network devices on cable length. The table is based on typical installations of HART devices in non-IS environments, i.e. no miscellaneous series impedance. Detailed information for determining the maximum cable length for any HART network configuration can be found in the HART Physical Layer Specifications.
Cable Capacitance – pf/ft (pf/m) Cable Length – feet (meters) No. Network Devices
20 pf/ft (65 pf/m)
30 pf/ft (95 pf/m)
50 pf/ft (160 pf/m)
70 pf/ft (225 pf/m)
1
9,000 ft (2,769 m)
6,500 ft (2,000 m)
4,200 ft (1,292 m)
3,200 ft (985 m)
5
8,000 ft (2,462 m)
5,900 ft (1,815 m)
3,700 ft (1,138 m)
2,900 ft (892 m)
10
7,000 ft (2,154 m)
5,200 ft (1,600 m)
3,300 ft (1,015 m)
2,500 ft (769 m)
15
6,000 ft (1,846 m)
4,600 ft (1,415 m)
2,900 ft (892 m)
2,300 ft (708 m)
Table 3: Allowable cable lengths for 1.02 mm (#18 AWG) shield twisted pair
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GETTING THE MOST OUT OF HART SYSTEMS
Intrinsic Safety Intrinsic safety (IS) is a method of providing safe operation of electronic process-control instrumentation in hazardous areas. IS systems keep the available electrical energy in the system low enough that ignition of the hazardous atmosphere cannot occur. No single field device or wiring is intrinsically safe by itself (except for battery-operated, self-contained devices), but is intrinsically safe only when employed in a properly designed IS system.
INTRINSIC SAFETY DEVICES
HART-communicating devices work well in applications that require IS operation. IS devices (e.g., barriers) are often used with traditional two-wire 4–20 mA instruments to ensure an IS system in hazardous areas. With traditional analog instrumentation, energy to the field can be limited with or without a ground connection by installing one of the following IS devices: T Shunt-diode (zener) barriers that use a high-quality safety ground connection to bypass excess energy (Figure 6) T Isolators, which do not require a ground connection, that repeat the analog measurement signal across an isolated interface in the safe-side load circuit (Figure 7 on page 19) Both zener barriers and isolators can be used to ensure an IS system with HART-communicating devices, but some additional issues must be considered when engineering the HART loop. HAZARDOUS SIDE
SAFE SIDE
Zener Barrier Power Supply
1–5 V Output Signal
Transmitter 250 Ω Load Resistor
Figure 6: 4–20 mA Loop with a Zener Barrier
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GETTING THE MOST OUT OF HART SYSTEMS
Intrinsic Safety HAZARDOUS SIDE
SAFE SIDE
Power Supply
Isolator
1–5 V Output Signal
4–20 mA Transmitter
250 Ω Load Resistor
Figure 7: 4–20 mA Loop with Isolator
DESIGNING AN IS SYSTEM USING SHUNT-DIODE BARRIERS
Designing an IS direct-current loop simply requires ensuring that a field device has sufficient voltage to operate, taking into account zener barrier resistance, the load resistor, and any cable resistance. When designing an IS loop using shunt-diode barriers, two additional requirements must be considered: T The power supply must be reduced by an additional 0.7 V to allow headroom for the HART communication signal and yet not approach the zener barrier conduction voltage. T The load resistor must be at least 230 Ω (typically 250 Ω). Depending on the lift-off voltage of the transmitter (typically 10–12 V), these two requirements can be difficult to achieve. The loop must be designed to work up to 22 mA (not just 20 mA) to communicate with a field device that is reporting failure by an upscale, over-range current. The series resistance for the same zener barrier may be as high as 340 Ω. To calculate the available voltage needed to power a transmitter, use the following equation: Power Supply Voltage – (Zener Barrier Resistance + Sense Resistance) × Operating Current (mA) = Available Voltage Example: 26.0 V – (340 Ω + 250 Ω) × 22 mA = 13.0 V Any cable resistance can be added as a series resistance and will reduce the voltage even further. In addition, the power supply to the zener barrier must also be set lower than the zener barrier conduction voltage. For example, a 28 V, 300 Ω zener barrier would typically be used with a 26 V power supply.
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GETTING THE MOST OUT OF HART SYSTEMS
Intrinsic Safety While it is difficult to meet the two requirements noted above for a network using shunt-diode barriers, it can be done. Following are two possible solutions to the problem: 1. Shunt the load resistor with a large inductor so that the load resistor impedance is still high (and mainly resistive) at HART signal frequencies, but much lower at direct current. This solution, while it does work, is physically somewhat inconvenient. 2. Use an IS isolator rather than a shunt-diode barrier. The output voltage on the hazardous side is usually specified as greater than X Vdc at 20 mA (typically 14–17 V). This value already includes the voltage drop due to the internal safety resistor, so the only extra voltage drop is that due to cable resistance. System operation at 22 mA requires reducing the 20 mA voltage by 0.7 V (340 Ω × 2 mA).
DESIGNING AN IS SYSTEM USING ISOLATORS
The implementation of HART loops in an IS system with isolators requires more planning. An isolator is designed to recreate the 4–20 mA signal from the field device in the safe-side load circuit. Most older isolator designs will not carry the high frequencies of HART current signals across to the safe side, nor will they convey HART voltage signals from the safe side to the field. For this reason, HART communication through the isolator is not possible with these older designs. (It is still possible to work with a handheld communicator or PC with an IS modem on the hazardous side of the isolator.) When retrofitting HART instruments into an existing installation, inspect the system for isolators that may have to be replaced (any isolators that will not support HART signals). Major suppliers of IS isolators have introduced designs that are fully HART compatible. Modern IS isolators provide trouble-free design and operation and transparent communication in both directions.
IS device suppliers can assist with certification and performance specifications for their HART-compatible products. Field device manufacturers will also supply certification details for their specific products.
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GETTING THE MOST OUT OF HART SYSTEMS
Intrinsic Safety MULTIDROP IS NETWORKS
HART multidrop networks are particularly suitable for intrinsically safe installations. With a multidrop configuration, fewer barriers or isolators are required. In addition, because each field device takes only 4 mA (for a total of 16 mA in a four-device loop), plain zener barriers can be used. With a 250 Ω load, 25 V – (340 + 250 Ω) × 16 mA = 15.5 V, which is well above the transmitter lift-off voltage and leaves a margin for cable resistance.
IS OUTPUT LOOPS
For output devices such as valve positioners, direct-current voltage considerations will vary depending on the drive requirements of the device. Zener barriers may be possible. If not, modern HART-compatible output isolators are appropriate.
IS CERTIFICATION CONSIDERATIONS
If the HART loop contains an IS-approved handheld communicator or modem, slight changes may be needed to meet IS installation certification rules. Handheld communicators and modems add the HART signal voltage to the voltage level coming from the zener barrier or isolator. For example, a handheld communicator typically adds a maximum of 2 V to the loop. Therefore, when used with a 28 V zener barrier, a total of 30 V may theoretically be present in the loop. The allowable capacitance must be reduced by about 15% to account for this increase in voltage.
IS NETWORK CABLE LENGTH CALCULATIONS
The cable length calculation must include the resistance of both the zener barrier and the load resistor.
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GETTING THE MOST OUT OF HART SYSTEMS
HART Multidrop Networks The HART communication protocol enables several instruments to be connected on the same pair of wires in a multidrop network configuration (Figure 8). The current through each field device is fixed at a minimum value (typically 4 mA) sufficient for device operation. The analog loop current does not change in relation to the process and thus does not reflect the primary variable. Communications in multidrop mode are entirely digital. Master Device Modem
Auxiliary Power Supply Transmitters
Figure 8: Multidrop Configuration
Standard HART commands are used to communicate with field instruments to determine process variables or device parameter information (see HART Commands on page 7). The typical cycle time needed to read information on a single variable from a HART device is approximately 500 milliseconds (ms). For a network of 15 devices, a total of approximately 7.5 seconds is needed to scan and read the primary variables from all devices. Reading information from multivariable instruments may take longer, as the data field will typically contain values for four variables rather than just one. The typical multidrop network enables two-wire measurement devices to be connected in parallel. Two-wire loop-powered and four-wire active-source devices can be connected in the same network. If both twoand four-wire devices are used in the same network, three wires must be used to properly connect the devices (see Water Treatment Facility Upgrade on page 45).
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HART Multidrop Networks MULTIDROP WITH HART FIELD CONTROLLERS
HART field controllers can also be wired in a multidrop network (Figure 9). Each analog output signal from the transmitter/controllers is isolated from every other output signal, which provides a cost-effective HART network configuration. In this case, the analog signals are not fixed and are used for the output signal to the controlled device. Handheld Terminal Power Supply
Computer or DCS
HART Interface
Power Supply Impedance
4–20 mA
+
–
+
–
+
–
+
–
+
–
+
–
HART Transmitter
Control Valve
Figure 9: HART Controllers with Multidrop
APPLICATION CONSIDERATIONS
Connecting HART field devices in a multidrop network can provide significant installation savings. The total cable length in a multidrop network is typically less than the maximum cable length in point-to-point connections because the capacitance of the additional devices reduces the distance that the HART signal can be carried (see Wiring and Installation on page 17). To save on installation costs, use HART multidrop networks for remote monitoring stations, tank farms, pipeline distribution systems, and other monitoring applications in which fast update rates are not required.
CONFIGURING DEVICES FOR MULTIDROP OPERATION
Using the polling address structure of the HART protocol, up to 15 devices can be connected in a multidrop network. The analog current of a HART device can be fixed by setting its polling address to a number other than zero. With the HART protocol, each field instrument should be configured with different polling addresses or tag numbers before being connected to a multidrop network—otherwise, the master will not be able to establish communication with the slave devices.
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GETTING THE MOST OUT OF HART SYSTEMS
Control System Interfaces When you change your existing control system by adding a HART interface, it is important to understand the complete functionality offered by the HART interface. While several control-system suppliers offer HART interfaces, not all interfaces provide the same functionality. Control systems such as a DCS, PLC, or SCADA/RTU (remote terminal unit) implement only the functionality required for a given application. For example, a flow-control system may only read the primary variable of a device and provide no additional support for viewing or changing configuration information. Other control-system interfaces provide comprehensive HART support, maintaining complete configuration records for all connected devices. Contact your system supplier for specific details on their HART interface(s). Use the form in Appendix A to obtain information from control-system suppliers to identify specific characteristics of their products.
HART I/O SUBSYSTEMS
Many HART-compatible I/O subsystems have multiple analog channels on each I/O card. Suppliers choose whether to provide one HART interface per channel or to share one HART interface among several channels. The number of shared channels per HART interface impacts the frequency of data updates from a HART field device and the HART functionality that is supported.
HART I/O FOR MULTIDROP SUPPORT
For the best performance and flexibility, one HART interface should be dedicated to each I/O channel. Systems that share only one HART interface among several I/O channels may not support multidrop networks. The effective update rate of a multiplexed interface is slow enough that the performance of multiplexed multidrop networks would not be practical. Some suppliers enable multidrop support by fixing the HART interface to one specific I/O channel. However, the other channels on that card may then not be available for HART communications.
HART I/O FOR BURST MODE SUPPORT
Burst mode is an optional implementation in a field device. Receiving burst mode messages is optional in a host as well. To take full advantage of burst mode, the I/O system should have one HART interface for each channel. If the HART interface is shared by more than one channel, messages sent by the field device may not be detected by the control system. If the system does not have the ability to configure burst mode in the field device, a handheld terminal or other configuration tool is required.
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Control System Interfaces DATA HANDLING
All HART-compatible control systems can read the digital primary variable from a slave device. However, some system architectures may not be able to accommodate textual data (e.g., tag and descriptor fields). In these cases, the controller is able to read the process variable, but may not have direct access to all other data in the HART device.
PASSTHROUGH FEATURE
Some control systems are integrated with a configuration or instrumentmanagement application. In these systems, the control system passes a HART command, issued by the management application, to the field device via its I/O interface. When the control system receives the reply from the field device, it sends the reply to the management application. This function is referred to as a passthrough feature of the control system.
GATEWAYS
Gateways can be used to bring HART digital data into control systems that do not support HART-capable I/O. Some systems support HART gateways with communication protocols such as Modbus, PROFIBUS DP, or TCP/IP Ethernet. The typical HART gateway supports all universal commands and a subset of the common practice commands. Support varies depending on the gateway supplier. Some gateways support access to device-specific information.
SCADA/RTU SYSTEMS
RTUs used in SCADA systems use a special telemetry to communicate with the control system. RTUs have the same considerations regarding multidrop and burst mode support as other systems. However, implementation is made more complex because RTUs often communicate to an upper-level host using a communication protocol other than HART (e.g., Modbus). While there are many benefits to implementing HART in an RTU (support of multidrop, burst mode, and multivariable instruments), HART data are only available to the central host system if the telemetry protocol supports the transfer of HART commands or specific HART data (see Multidrop for Tank Farm Monitoring on page 40).
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GETTING THE MOST OUT OF HART SYSTEMS
Multiplexers HART-compatible multiplexers are ideal for users who want to interface with a large number of HART devices. Multiplexers can be modular and are capable of supporting both point-to-point and all-digital (multidrop) HART communication modes. Communication between a multiplexer and a host application depends on the multiplexer capabilities (e.g., RS232C, RS485, Modbus, and TCP/IP Ethernet). When installing HART multiplexer systems, the following capabilities should be considered: T Number of HART channels supported T Number of HART channels that share a HART modem T Burst mode support T Multidrop support T Method of communication with the host computer or control system
MULTIPLEXER AS THE PRIMARY I/O SYSTEM
HART multiplexers can be used as the primary I/O front end for a HART-based control or monitoring system (Figure 10). Typically, a PC acts as the host, providing the human-machine interface and performing other high-level functions. The multiplexer continuously monitors the field devices, reports the current readings and instrument status to the host, and passes HART commands from the host computer to the field devices. Multiplexer
Field Devices
SCADA
Field Device
Figure 10: HART Multiplexer as the Primary I/O System
PARALLEL MONITORING WITH A MULTIPLEXER
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When a traditional 4–20 mA control system is using the analog signals for measurement and control outputs, a HART multiplexer can be added to the network to gain access to the digital HART signal. Using a multiplexer enables a supervisory computer to monitor diagnostics and device status, access configuration information, and read any additional process inputs or calculations not provided by the 4–20 mA signal.
© 2003 HART Communication Foundation
GETTING THE MOST OUT OF HART SYSTEMS
Multiplexers Use a HART multiplexer to gain access to the digital HART signal.
Two types of multiplexers are used in conjunction with a control system. A multiplexer wired in parallel with the field wiring is commonly used when the control system wiring is already in place (Figure 11). Automation and Display System
Supervisory Computer
Controllers
I/O Multiplexer
Transmitter
Control Valves
Figure 11: HART Multiplexer with Existing I/O
A multiplexer can also be an integral part of the control system as a third-party I/O (Figure 12). As an I/O system, the multiplexer can include IS barriers and other filtering capabilities and provide services to the field device, such as galvanic isolation or power. For this type of installation, no additional terminations or space are required. The multiplexer can also act as a gateway to convert the HART messages to another protocol such as Modbus, PROFIBUS, or Ethernet. .
Automation and Display System
Supervisory Computer
Controller I/O
Transmitter
Control Valve
Figure 12: HART Multiplexer Integrated with I/O
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GETTING THE MOST OUT OF HART SYSTEMS
Reading HART Data into NonHART Systems Many HART products are able to perform more than one measurement or output function (e.g., make multiple process measurements, calculate process information, and provide positioner feedback information). All of this information can be easily accessed digitally. However, existing controllers or interface equipment may not have the ability to read digital HART data. Products are available that can read HART digital signals and convert them to analog or contact information, which enables any traditional analog/digital I/O to take full advantage of the benefits of HART-communicating devices. The Rosemount Inc. Tri-Loop module and the Moore Industries Site Programmable Alarm (SPA) are two such products.
HART DATA-CONVERSION PRODUCTS
The Tri-Loop module monitors a HART loop for a bursting message and converts three of the four possible variables in HART command number three to analog outputs (Figure 13). The conversion enables the field device to provide a total of four analog signals over a single pair of wires run from the field. .
Channel 1
4–20 mA Signals for Secondary Variables
Channel 2 Channel 3
Field Terminals Rail-Mounted Tri-Loop Module
Control System
Figure 13: Tri-Loop Module
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GETTING THE MOST OUT OF HART SYSTEMS
Reading HART Data into NonHART Systems The SPA module continuously communicates with any HART-capable device and provides contact closure outputs (alarm trips) based on the information received (Figure 14). For example, the SPA can be configured to monitor the device-status information inherent in the HART communication protocol and trigger events such as local on/off applications or alarms. The SPA can also initiate emergency shutdown action if problems are detected with a field device in critical loop applications. HART Transmitter
4–20 mA and HART Digital Signals
HART Communicator
Control System Process and Diagnostic Data
Annunciator
HART Master
Shutdown Controls Event Recorder
Figure 14: SPA Module
Both HART Tri-Loop and SPA provide multivariable product support on a loop-by-loop basis.
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GETTING THE MOST OUT OF HART SYSTEMS
Universal Handheld Communicator The 275 Universal HART Communicator is available from major instrumentation suppliers around the globe and is supported by all member companies in the HCF. Using HART DDL, the communicator can fully communicate with and configure any HART device for which it has a DD installed. If the communicator does not have the DD for a particular network device installed, it can still communicate with that device using the universal and common practice commands (see HART Commands on page 7). The HCF provides centralized control and registration for all DDs that can be loaded into the communicator. An index of registered DDs can be found on the world wide web at
. Use the 275 Universal HART Communicator to communicate with and configure any HART-communicating device.
Figure 15: 275 Universal Handheld Communicator
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PC Configuration Software Many instrument manufacturers, as well as some independent software developers, offer HART communication software for PCs with capabilities similar to and beyond those offered by a HART handheld communicator. Use special software applications to continuously monitor the status of connected field devices and log status changes as they occur, which may help reduce the costs of regulatory compliance.
The software packages listed in Table 4 are used for configuration management, parameter tuning, and data acquisition with a HART device. The list is not comprehensive, and all software applications are not functionally equivalent. A number of product-specific software applications are also available for diagnostics. An RS232 HART interface or other interface device connects the PC running the HART application software to the field devices.
SUMMARY TABLE OF HART SOFTWARE
Software
Application
Manufacturer
Asset Management Solutions (AMS)
Configuration and calibration Fisher-Rosemount management
CONF301 HART Configurator
Configuration management
Smar International
CONFIG
Configuration management
Krohne
Cornerstone Base Station
Configuration and calibration Applied System management Technologies
Cornerstone Configurator
Instrument configuration
Applied System Technologies
H-View
Configuration management and data acquisition
Arcom Control Systems
IBIS
Configuration management
EB Hartmann & Braun
IBIS
Configuration management
Samson
K-S Series
Configuration management
ABB
Mobrey H-View
Configuration management
KDG Mobrey
Pacemaker
Configuration management
UTSI International Corporation
SIMATIC PDM
Configuration management
Siemens
Smart Vision
Configuration management
EB Hartmann & Braun/ Bailey Fischer & Porter
XTC Configuration Software
Configuration management
Moore Products Co.
Table 4: HART Software © 2003 HART Communication Foundation
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GETTING THE MOST OUT OF HART SYSTEMS
Commissioning HART Networks HART-based instruments have several features that significantly reduce the time required to fully commission a HART network (loop). When less time is required for commissioning, substantial cost savings are achieved.
DEVICE VERIFICATION
Before installation, manufacturers usually enter device tags and other identification and configuration data into each field instrument. After installation, the instrument identification (tag and descriptor) can be verified in the control room using a configurator (handheld terminal or PC). Some field devices provide information on their physical configuration (e.g., wetted materials)—these and other configuration data can also be verified in the control room. The verification process can be important in conforming to governmental regulations and ISO quality requirements. The commissioning process can be further streamlined by connecting a PC configurator to each HART loop online, either by integration with the control system or by using one of the many available HART multiplexing I/O systems (see Multiplexers on page 26). With this centralized approach, there is no need to move the configuration device from one termination point to the next while commissioning all devices on the network.
LOOP INTEGRITY CHECK
Once a field instrument has been identified and its configuration data confirmed, the analog loop integrity can be checked using the loop test feature, which is supported by many HART devices. The loop test feature enables the analog signal from a HART transmitter to be fixed at a specific value to verify loop integrity and ensure proper connection to support devices such as indicators, recorders, and DCS displays. Use the HART protocol loop test feature to check analog loop integrity and ensure a proper physical connection among all network devices.
AS-INSTALLED RECORD KEEPING
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A HART configurator also facilitates record keeping. As-installed device configuration data can be stored in memory or on a disk for later archiving or printing.
© 2003 HART Communication Foundation
APPENDICESAPPENDICESAPPENDICES GETTING THE MOST OUT OF HART SYSTEMS
Device Status and Diagnostics Most HART field instruments provide both status information and diagnostic information. The HART protocol defines basic status information as information that is included with every message from a field device. Basic status information enables the host application to immediately identify warning or error conditions detected by the field device. Status messages also enable the user to differentiate between measurements that are outside sensor or range limits and actual hardware malfunctions. Examples of status messages are: T Field device malfunction T Configuration changed T Cold start T More status available T Analog output current fixed T Analog output saturated T Nonprimary variable out of limits T Primary variable out of limits HART instruments can implement extensive, device-specific diagnostics. The amount and type of diagnostic information is determined by the manufacturer and varies with product and application. Diagnostic information can be accessed using the HART communication protocol. Host applications using DD files can interpret and display diagnostic information. Applications not using DD technology may require productspecific software modules to interpret diagnostic information. Many manufacturers offer special software applications for their own products. Some modules allow you to customize for specific products. Manufacturers of valve actuators have made extensive use of this capability to provide preventative and predictive diagnostic information that greatly enhances the value of their products as compared to conventional actuators. Several software applications are available that provide continuous communication with field devices using a HART-compatible multiplexer and HART I/O (see Multiplexers on page 26). These applications provide real-time monitoring of status and diagnostic information.
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GETTING THE MOST OUT OF HART SYSTEMS
Connecting a PC to a HART Device or Network PCs are commonly used for HART host applications for configuration and data acquisition. A specially designed device (Table 5) allows the HART network to be connected to the RS232C serial port or PCMCIA slot of a PC (Figure 16). Product Name
Manufacturer
Commubox
Endress + Hauser
FSK-Modem
EB Hartmann & Braun
HT311 RS232 Interface
Smar International
VIATOR PCMCIA HART Interface
MACTek
VIATOR RS232 HART Interface
MACTek
Table 5: HART Interfaces
PC/Host Application
RS232 HART Interface
Handheld Terminal
Field Device Power Supply
Figure 16: RS232 HART Interface
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GETTING THE MOST OUT OF HART SYSTEMS
PC Application Development Tools Software drivers are available to assist in the development and integration of PC applications with HART networks. Table 6 shows a partial list of products available. Product Name
Description
Manufacturer
Hview
Provides DDE server
Arcom Control Systems
HRT VBX
16-bit Visual Basic driver
Borst Automation
HRT OCX
32-bit ActiveX Control
Borst Automation
HART OPC Server
OPC Server
HCF (via member companies)
HL-LinkPro
HART driver for LabVIEW
Cardiac Systems Solutions
Table 6: PC Development Tools
© 2003 HART Communication Foundation
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GETTING THE MOST OUT OF HART SYSTEMS
Control in Field Devices Microprocessor-based smart instrumentation enables control algorithms to be calculated in the field devices, close to the process (Figure 17). Some HART transmitters and actuators support control functionality in the device, which eliminates the need for a separate controller and reduces hardware, installation, and start-up costs. Accurate, closed-loop control becomes possible in areas where it was not economically feasible before. While the control algorithm uses the analog signal, HART communication provides the means to monitor the loop and change control setpoint and parameters. PC-Based Operator Interface
Modbus Link (RS232)
Muiltiplexer (HART Master) 4–20 mA to Position Valve
HART Transmitter with PID Slave
Control Valve
Figure 17: Transmitter with PID (HART Slave)
Placing control in the field enhances control functionality. Measurement accuracy is maintained because there is no need to transmit data to a separate controller. Control processing takes place at the high update rate of the sensor and provides enhanced dynamic performance.
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Control in Field Devices HART FIELD CONTROLLER IMPLEMENTATION
A HART field controller takes advantage of the HART protocol’s simultaneous analog and digital signaling by converting the transmitter’s traditional analog measurement output into a control output. The analog signal from the smart transmitter (controller) is used to manipulate the field device (Figure 18). The analog output signal also carries the HART digital signal, which is used for monitoring the process measurement, making setpoint changes, and tuning the controller. Bypass Capacitor
+ Power Supply
Resistor
Smart Transmitter
Control Valve
Figure 18: Smart Transmitter with PID
The communication rate of the HART protocol (2–3 updates per second) is generally perceived as too slow to support closed-loop control in the central host. With control in the field, the control function no longer depends on the HART protocol’s communication rate. Instead, the control signal is an analog output that is updated at a rate that is much faster than can typically be processed in a conventional control system. Processing rates vary from 2–20 updates per second, depending on the product. The HART digital communication rate remains sufficient for monitoring the control variable and changing setpoint values.
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INDUSTRY APPLICATIONS
Industry Applications Many companies in a wide variety of industries have already realized the advantages of using the HART communication protocol. This section describes some applications in detail and outlines the tangible benefits that result. The applications have been grouped into the following sections: T Inventory-management applications T Cost-saving applications T Remote-operation applications T Open-architecture applications
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INDUSTRY APPLICATIONS
Inventory-Management Applications Accurate measurements for inventory management are essential in all industries. The HART communication protocol enables companies to make sure inventory management is as efficient, accurate, and low cost as possible.
HART MULTIDROP NETWORK FOR TANK LEVEL AND INVENTORY MANAGEMENT
Tank level and inventory management is an ideal application for a HART multidrop network (Figure 19). The HART network digital update rate of two PVs per second is sufficient for many tank-level applications. A multidrop network provides significant installation savings by reducing the amount of wiring from the field to the control room as well as the number of I/O channels required. In addition, many inexpensive process-monitoring applications are commercially available to further cut costs. Transmitters Storage Tanks
HART Field Multiplexer
Figure 19: Inventory Management with Multidrop
One company uses a HART multiplexer to digitally scan field devices for level-measurement and status information. The information is forwarded to the host application using the Modbus communication standard. Multivariable instruments further reduce costs by providing multiple process measurements, such as level and temperature, which reduces the wiring and number of process penetrations required.
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INDUSTRY APPLICATIONS
Inventory-Management Applications MULTIDROP FOR TANK FARM MONITORING
In one tank farm application, 84 settlement tanks and filter beds on a very large site (over 300,000 m2) are monitored using HART multidrop networks and HART RTUs (see SCADA/RTU Systems on page 25). The HART architecture required just eight cable runs for 84 tanks, with 10–11 devices per run (Figure 20). Over 70 individual runs of over 500 m each were eliminated. Cable savings were estimated at over $40,000 when compared to a conventional installation. RTU I/O was also reduced, which resulted in additional hardware and installation savings. The total installed cost was approximately 50% of a traditional 4–20 mA installation. HART Multiplexer
Storage Tanks
Control Room
Storage Tanks
Figure 20: Tank Farm Monitoring with Multidrop
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INDUSTRY APPLICATIONS
Inventory-Management Applications UNDERGROUND PETROLEUM STORAGE WITH HART COMMUNICATION FOR ACCURACY
Underground salt caverns are frequently used for crude oil storage. One customer pumps oil from barges into the storage caverns. An ultrasonic flowmeter records the total flow. To get the oil out of the caverns, a brine solution is pumped into the cavern through a magnetic flowmeter. Brine and crude oil flowing in both directions are measured and reported to the DCS using the HART communication protocol for accuracy. The DCS tracks flow rate and total quantity to maintain a certain pressure inside the caverns (Figure 21). HART Transmitter Interface HART Transmitter Interface
Oil Caverns
Field Instruments
Note: Digital accuracy for flow accuracy and flow totals
Figure 21: Underground Petroleum Storage
© 2003 HART Communication Foundation
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INDUSTRY APPLICATIONS
Cost-Saving Applications Use HART multidrop networking to reduce installation and maintenance costs.
WASTEWATER TREATMENT PLANT UPGRADE
A Texas wastewater treatment plant replaced stand-alone flowmeters and chart recorder outstations that required daily visits for totalization with a HART system. HART-based magnetic flowmeters were multidropped into HART RTUs to create a cost-effective SCADA network. The use of HART technology reduced system and cable costs, enhanced measurement accuracy, and eliminated time-consuming analog calibration procedures. A system of 11 HART multidrop networks was used to connect 45 magnetic flowmeters from different plant areas. Each flowmeter communicated flow rate and a totalized value over the HART network. Multidrop networks eliminated the need for additional hardware and PLC programming while providing a more accurate totalized value. Complex and costly system integration issues were also avoided—for example, there was no need for synchronization of totals between the host and field PLCs. Multidrop networking further reduced the installation cost by reducing the required number of input cards from the traditional 45 (for point-to-point installations) to 11. Maintenance was simplified because of access to instrument diagnostic and status data.
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INDUSTRY APPLICATIONS
Cost-Saving Applications APPLIANCE MANUFACTURING WITH MULTIDROP
A consumer appliance manufacturer used the networking capability of the HART protocol to measure level, flow, and pressure. HART multidrop provided substantial wiring and installation savings as well as digital accuracy with the elimination of the analog to digital (A/D) and digital to analog (D/A) conversions of the instrument and PLC I/O. Figure 22 shows pressure transmitters connected to a PLC via smart transmitter interface multiplexers. Storage Tanks
Highway
PLC
Communication Module Smart Transmitter Interface
Terminal Block Module
Figure 22: Multidrop Network Example
© 2003 HART Communication Foundation
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INDUSTRY APPLICATIONS
Cost-Saving Applications REMOTE REZEROING IN A BREWERY
The benefits of remote monitoring and rezeroing of smart transmitters using the HART protocol are dramatically illustrated in this example of two smart transmitters that control the fluid level in lauter tubs in a brewhouse application. Similar benefits would be realized in any application involving a closed vessel. Two smart transmitters are installed on each lauter tub—one on the bottom of the tank and the other about nine inches from the bottom. The bottom transmitter is ranged ±40 inH2O; the upper transmitter is ranged 0–30 inH2O. As the lauter tub is filled, the bottom transmitter senses level based on pressure. When the level reaches the upper transmitter, that point is marked as the new zero-level point, and the upper transmitter becomes the primary sensing instrument for the lauter-tub level. The nine-inch zero-level offset from the bottom of the tank is necessary to accommodate loose grain that settles in the bottom of the tank. Transmitters that are coordinated and working together control fluid level in each lauter tub to within a few barrels. However, the upper transmitter requires periodic maintenance or replacement and rezeroing. An undetected false upper-transmitter level reading can cause a tank level error of up to 40 gallons. The usual procedure for transmitter rezeroing takes about 95 minutes and has been required as frequently as twice a day. Rezeroing a transmitter using configuration software and PLC interface modules eliminates the need to locate and identify the problem at the site as well as the need for verification by control-room personnel and greatly reduces the chance for inadvertent errors. Estimated total time to rezero each transmitter is reduced to 15 minutes. Through the configuration software’s instrument-status and diagnostic capabilities, a false level indication can be automatically detected while a lauter tub fill is in progress. The affected transmitter can then be automatically rezeroed by programming logic in the programmable controller to issue the appropriate command to the instrument.
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INDUSTRY APPLICATIONS
Cost-Saving Applications WATER TREATMENT FACILITY UPGRADE
HART transmitters and a control system with HART capability were chosen to upgrade a water treatment facility. The completed installation reduced capital, engineering, and installation costs. The process dynamics of the water treatment facility allowed the HART instruments to be used in all-digital mode without compromising plant performance. The water treatment plant is divided into two areas, each with 14 filters. Each area is controlled by a separate control system for complete autonomy. A HART network monitors each filter for filter level, filter bed differential, and filter outlet flow. The multidrop installation used a three-wire system in order to accommodate both the two-wire and the four-wire devices (magnetic flowmeters) in use (Figure 23) (see Multidrop on page 6). Pressure Transmitters
4 mA
12 mA
Main Power
4 mA
Magnetic Flowmeter
Figure 23: Multidrop Networks with 2-Wire and 4-Wire Devices
Because the water treatment facility had a modular design, the use of HART instruments allowed the configuration from the one filter network to be copied to the others, which reduced the implementation time. Engineering, system configuration, drafting, commissioning, maintenance, and documentation were simplified. A reduced I/O card count also saved money.
© 2003 HART Communication Foundation
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INDUSTRY APPLICATIONS
Cost-Saving Applications IMPROVED DIAGNOSTICS
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A cleaning materials supplier required periodic checkup of the instrument condition and configuration information as compared to the initial installation. The field transmitters provided a historical record of status changes along with current configuration information. Periodic download of this information was made possible using PLC ladder logic developed for HART instruments.
© 2003 HART Communication Foundation
INDUSTRY APPLICATIONS
Remote-Operation Applications UNMANNED OFFSHORE GAS PRODUCTION WITH HART NETWORKS
Choosing the HART communication protocol for all-digital communication in a wide-area network enabled one company to have real-time monitoring and control, access to diagnostics, and maintenance capabilities—all from a remote location. Over half of the 500 transmitters on 15 platforms could be multidropped with update rates of three seconds (six devices), which resulted in substantial savings in wiring, I/O, and installation. The remaining devices (flowmeters) required a faster response and were wired point to point using digital HART communications to transmit the process data. The flowmeters used the optional burst mode, which provided an update rate of 3.7 times per second. All-digital communications provided maximum accuracy and eliminated potential errors from input scaling, conversion, and drift (see Multidrop on page 6). Radio Antennae
Standby RTU
Primary RTU
Modbus Link
HART Multiplexers Transmitters
Transmitters
Figure 24: RTU Application
Each platform’s RTU provided a link to approximately 50 temperature, pressure, and flow transmitters (Figure 24). The RTU used the multimaster capability of the HART protocol to enable the second RTU to act as a hot standby, which monitored activity and was able to take over if a failure occurred. The RTUs provided links with the emergency and safety systems and a local interface for maintenance personnel. The Modbus protocol was used for communication to the central SCADA system.
© 2003 HART Communication Foundation
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INDUSTRY APPLICATIONS
Remote-Operation Applications VENEZUELA GAS-LIFT PROJECT
In a Venezuela gas-lift project, HART multidrop technology was used for remote operation of offshore gas-lift production wells at considerable savings (Figure 25): T 30% decrease in installation costs T 16:1 reduction of input modules T Reduced cost of I/O cards in the RTU T Remote reranging T Remote access to the transmitter status for improved process uptime Radio Antennae
Microwave Towers
Configuration and Maintenance Tools
Electric Valve
Control Room HART Transmitters
Figure 25: Offshore Gas-Lift Project
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INDUSTRY APPLICATIONS
Open-Architecture Applications OIL REFINERY EXPANSION
The best way to judge the openness of a communication protocol is by the number of products supported. By this standard, the HART protocol is perhaps the most open of any field-communication protocol available today. In a major refinery expansion, an oil company weighed the advantages of using either a proprietary system or a HART-based system. The results indicated that the company could use HART digital instruments in 92% of their applications, compared to only 33% with the proprietary system. Choosing HART products resulted in an incremental $23,000 in savings due to commissioning efficiencies and ongoing maintenance and diagnostic capabilities. The oil company used a traditional control system with analog I/O and supplemented the control capability with an online maintenance and monitoring system. All of the HART field devices were monitored from a central location (Figure 26). Ethernet Link
Maintenance Station
Control Display System Controller
HART Multiplexer
I/O
I/O
HART Transmitter
Control Valve Fisher
Fisher
Figure 26: Online Implementation
© 2003 HART Communication Foundation
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INDUSTRY APPLICATIONS
Open-Architecture Applications HART WITHIN A PROFIBUS NETWORK
HART field devices can be seamlessly integrated with PROFIBUS DP networks using the HART/DP Link, which enables the connection of four HART devices and facilitates the passthrough of HART commands to host applications on the DP network (Figure 27). The HART/DP Link supports IS installations. PCs with HART Applications
PLC
PROFIBUS DP
Remote I/O HART/DP Link
DP/PA Link
DP/ASI Link
Profibus PA HART Instruments
Figure 27: HART Within a PROFIBUS Network
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INDUSTRY APPLICATIONS
Open-Architecture Applications HART/DDE SERVER
Cost-effective level- and temperature-monitoring systems can be designed using HART multidrop networks and commercially available HART/DDE interface software. HART/DDE interface software allows any compliant application (e.g., spreadsheet) to directly read the process data and status information available in HART field devices. A HART interface module connected to the PC’s serial port is needed for this HART monitoring application (Figure 28). Spreadsheet Data Logging
RS232 HART Interface
Power Supply
Transmitter
Figure 28: Multidrop Network
© 2003 HART Communication Foundation
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WHERE TO GET MORE INFORMATION
Where To Get More Information WHAT INFORMATION IS AVAILABLE?
To serve the growing interest in HART-related products, the HCF publishes a library of additional documents, articles, and overviews. The following information is currently available: T HART specifications T Technical overview T Application notes T Technical assistance T Training classes
WHERE TO FIND INFORMATION
By Mail HART Communication Foundation 9390 Research Blvd, Suite I-350 Austin, TX 78759 USA By Phone Call 512-794-0369. By Fax Send correspondence to 512-794-3904. By E-mail Send correspondence to . Online Visit the HCF website at .
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GLOSSARY
Glossary 275 HART Communicator
A handheld master device that uses the HART communication protocol and DDL to configure or communicate with any HART smart device
Bell 202
A U.S. telephone standard that uses 1,200 Hz and 2,200 Hz as 1 and 0, respectively, at 1,200 baud; a full duplex communication standard using a different pair of frequencies for its reverse channel; HART uses Bell 202 signals but is a half-duplex system, so the reverse channel frequencies are not used
Burst (Broadcast) Mode
A HART communication mode in which a master device instructs a slave device to continuously broadcast a standard HART reply message (e.g., value of a process variable) until the master instructs it to stop bursting
Cable Capacitance Per Unit of Length
The capacitance from one conductor to all other conductors (including the shield if present) in the network; measured in feet or meters
Cable Resistance Per Unit of Length
The resistance for a single wire; meausred in feet or meters
Closed-Loop Control
A system in which no operator intervention is necessary for process control
Communication Rate
The rate at which data are sent from a slave device to a master device; usually expressed in data updates per second
DCS
See Distributed Control System.
DD
See Device Description.
DDL
See Device Description Language.
Device Description
A program file written in the HART Device Description Language (DDL) that contains an electronic description of all of a device’s parameters and functions needed by a host application to communicate with the device
Device Description Language
A standardized programming language used to write DDs for HART-compatible field devices
Distributed Control System
Instrumentation (input/output devices, control devices, and operator interface devices) that permits transmission of control, measurement, and operating information to and from user-specified locations, connected by a communication link
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GLOSSARY
Glossary Field
The area of a process plant outside the control room where measurements are made, and to and from which communication is provided; a part of a message devoted to a particular function (e.g., the address field or the command field)
Field Device
A device generally not found in the control room; field devices may generate or receive an analog signal in addition to the HART digital communication signal
Frequency Shift Keying
Method of modulating digital information for transmission over paths with poor propagation characteristics; can be transmitted successfully over telephone systems
FSK
See Frequency Shift Keying.
Gateway
A network device that enables other devices on the network to communicate with a second network using a different protocol
HART Command Set
A series of commands that provide uniform and consistent communication for all master and slave devices; includes universal, common practice, and device-specific commands
HART Communication Protocol
Highway Addressable Remote Transducer communication protocol; the industry standard protocol for digitally enhanced 4–20 mA communication with smart field devices
HART Loop
A communication network in which the master and slave devices are HART smart or HART compatible
Host Application
A software program used by the control center to translate information received from field devices into a format that can be used by the operator
Interoperability
The ability to operate multiple devices, independent of manufacturer in the same system, without loss of functionality
Intrinsic Safety
A certification method for use of electrical equipment in hazardous (e.g., flammable) environments; a type of protection in which a portion of an electrical system contains only intrinsically safe equipment that is incapable of causing ignition in the surrounding environment
Intrinsic Safety Barrier
A network or device designed to limit the amount of energy available to the protected circuit in a hazardous location
IS
See Intrinsic Safety.
© 2003HART Communication Foundation
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GLOSSARY
Glossary Master Device
A device in a master-slave system that initiates all transactions and commands (e.g., central controller)
Master-Slave Protocol
Communication system in which all transactions are initiated by a master device and are received and responded to by a slave device
Miscellaneous Series Impedance
The summation of the maximum impedance (500 Hz–10 kHz) of all devices connected in series between two communicating devices; a typical nonintrinsically safe loop will have no miscellaneous series impedance
Modem
Modulator/demodulator used to convert HART signals to RS232 signals
Multidrop Network
HART communication system that allows more than two devices to be connected together on a single cable; usually refers to a network with more than one slave device
Multimaster
Multimaster refers to a communication system that has more than one master device. The HART protocol is a simple multimaster system allowing two masters; after receiving a message from a slave device, the master waits for a short time before beginning another transmission, which gives the second master time to initiate a message
Multiplexer
A device that connects to several HART loops and allows communication to and from a host application
Multivariable Instrument
A field device that can measure or calculate more than one process parameter (e.g., flow and temperature)
Network
A series of field and control devices connected together through a communication medium
Parallel Device Capacitance
The summation of the capacitance values of all connected devices in a network
Parallel Device Resistance
The parallel combination of the resistance values of all connected devices in the network; typically, there is only one low-impedance device in the network, which dominates the parallel device-resistance value
Passthrough
A feature of some systems that allows HART protocol send-and-receive messages to be communicated through the system interface
PID
Proportional-integral-derivative
PID Control
Proportional-plus-integral-plus-derivative control; used in processes where the controlled variable is affected by long lag times
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© 2003 HART Communication Foundation
GLOSSARY
Glossary Point to Point
A HART protocol communication mode that uses the conventional 4–20 mA signal for analog transmission, while measurement, adjustment, and equipment data are transferred digitally; only two communicating devices are connected together
Polling
A method of sequentially observing each field device on a network to determine if the device is ready to send data
Polling Address
Every HART device has a polling address; address 0 is used for point-to-point networks; addresses 1–15 are used in multidrop networks
Process Variable
A process parameter that is being measured or controlled (e.g., level, flow, temperature, mass, density, etc.)
Protocol
A set of rules to be used in generating or receiving a message
PV
See Process Variable.
Remote Terminal Unit
A self-contained control unit that is part of a SCADA system
RTU
See Remote Terminal Unit.
SCADA
See Supervisory Control and Data Acquisition.
Slave Device
A device (e.g., transmitter or valve) in a master-slave system that receives commands from a master device; a slave device cannot initiate a transaction
Smart Instrumentation
Microprocessor-based instrumentation that can be programmed, has memory, is capable of performing calculations and self-diagnostics and reporting faults, and can be communicated with from a remote location
Supervisory Control and Data Acquisition
A control system using communications such as phone lines, microwaves, radios, or satellites to link RTUs with a central control system
Zener
Type of shunt-diode barrier that uses a high-quality safety ground connection to bypass excess energy
© 2003 HART Communication Foundation
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tale of two plants
Two HART Projects Keep Plants Competitive A tale of two different projects in two different industries that achieve similarly impressive results
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hen end-users deploy devices enabled by the HART Communication Protocol, they quickly discover the technology’s reliability, ease of use, flexibility, robustness, and cost-effectiveness. They also learn how HART has proven itself in the field, whether it’s in process control or power plant applications. Kevin Kerls, of biotechnology manufacturer Genentech Inc. in South San Francisco, and Jerry Lowery, of the Ohio State University in Columbus, also attest to the essential value of HART in industrial automation applications. “You can use HART to implement all the highvalue functions of other bus technologies—Foundation fieldbus, Profibus and DeviceNet—but at a fraction of their cost by using infrastructure that you probably already have in your plant today,” explains Kerls, a senior automation engineer in Genentech’s automation group. Kerls is helping automate Genentech’s CCP2 facility in Vacaville, Calif. which is currently under construction and is expected to produce 200,000 liters of oncology pharmaceuticals by 2009. “In a regulated industry, it’s critical to manage device configurations,” says Kerls. “Integrating HART Communication with our distributed control system (DCS) allows us to mitigate both of these risks.” Meanwhile, on Ohio State’s main campus, Lowery also extols the virtues of HART. Most technicians are familiar with HART-enabled communicators. “The technicians love them. They’re superior for the technicians,” says Lowery, a control systems engineer at OSU’s McCracken Power Plant. Another important feature is that HART is an open standard. “It gives everyone a common thing to S- Advertising supplement to CONTROL
photo courtesy of the Ohio State University
work toward,” he explains. “HART is the way to go. It makes life so much easier.”
Ivy Towers, Hot and Cold HART Operating continuously, the McCracken plant provides 85% of the Buckeyes’ steam-based energy needs. The steam is used for heating, humidifica-
tale of two plants tion, sterilization, chilled-water, compressed air and He used the valve positioner digital PV to validate domestic hot-water production. The plant has five the valve’s position. If the valve didn’t reach proper industrial boilers. Presently, the oldest is a Babcock position in 30 seconds, an alarm would sound and & Wilcox (B&W) D-Style, 600-psi, 220,000 lbs/hr a warning would be displayed on the HMI screen. unit. Two new 200-psi Nebraska D-style units that The DigPV, which proved that the valve was not produce 220,000 lb/hr of steam were installed in seating properly, and the digital secondary vari2004-05. Two more Nebraska Ds are now being able (DigSV), in this case positioner temperature, installed, and the 200-psi, 150,000-lb/hr units are ex- indicated that a temperature “exceedance” had ocpected to be online by January 2007. Co-located at curred. “The HART secondary value or device temthe plant are seven York chillers, and three Caterpilperature on the original positioner was trended and lar emergency diesel generators. proved that the device never exceeded its maximum Lowery doesn’t mince words about how imporoperating temperature of 50 ºC,” adds Lowery. tant HART is to the plant. “We have approximateThese data convinced the vendor to replace ly 200 to 250 HART-enabled devices. Without the valve positioner, “and the problem went HART, this plant wouldn’t operate,” he says. away,” Lowery notes. This is important because HART also helps the plant’s technicians save the vendor originally claimed the boiler’s operatime finding instrument problems. “We don’t tion had overheated and caused the SH venthave to spend as much time looking for what’s control valve to become stuck. wrong,” adds Lowery. Ohio State also convinced the vendor to fix six For example, staffers recently observed interSH vent valves saving approximately $10,000. mittent signal failures on a temperature transAlso, the combined digital PVs and SVs’ performitter on one boiler’s mance not only saved a superheater (SH) vent potential $300,000 cost “We have approximately 200-250 control, which caused of replacing the existing the vent to go into the superheater, but also led HART-enabled devices. This plant wrong position. Howthe vendor to install a wouldn’t operate without HART.” ever, thanks to a HARTmore reliable positioner. enabled Honeywell Lowery appreciates DCS system on the B&W boiler, they were able to this digital value functionality. “Digital PVs are quickly correct the problem. extremely valuable in critical loops to validate the “This was the first time we’d seen this type of analog position with the digital position,” he adds. HART information,” he explains. The spreadsheet Besides diagnostics, having analog and digital showed data with a log/time-stamp describing an communication available simultaneously with event. In this case, descriptions included “primary HART is particularly valuable to Lowery. “This variable (PV) was out of sensor limits” or “bad: capability is extremely important when validating check measuring” and “field device malfunction.” loops. We use the digital PVs to validate analog Once the staff found the event descriptions in the PVs on critical positioners. It just tells us what event log, they solved their problem the same day. is wrong with the device,” he states. “And on “We knew exactly what was wrong. The technician critical loops, if the analog PVs and digital PVs went out, and repaired the resistance temperature don’t match up within a certain percentage of device (RTD),” he says. “With the HART-enabled each other, we alarm that loop and have operators DCS, our technicians know what the problem is.” investigate the actual valve position.”
Results Proven, Risks Lessened
Buckeyes’ Assets Managed
A second event at Ohio State involved an SH ventcontrol valve failure. The McCracken plant’s valve wouldn’t open or would become stuck while partially open, Lowery recalls. “A vent-control valve failure put the boiler superheater at risk.” Lowery decided to use the HART protocol’s digital PV (DigPV) that was accessible from the DCS.
The simultaneous analog-digital capability of HART fulfills one of the most obvious asset management functions of HART-enabled automation— protecting equipment and keeping plants operating. Of the 200-250 HART-enabled devices at the McCracken plant, an asset management system (AMS) monitors 40 of them. By the end of 2007, the AMS Advertising supplement to CONTROL S-
tale of two plants will monitor 180-200 HART devices, Lowery says. “The asset manager monitors and tracks device faults for all HART-enabled devices. Types of device faults—anything you can think of,” he explains. Overall, diagnostics are much improved, he notes. “Our asset manager package tracks faults that occur in HART devices through our DCS. Small items, like a positioner losing its zero position are now caught early and repaired,” Lowery says. “But without that asset management software, the problem might have never been corrected because it wouldn’t have been seen until complete device failure.”
Kerls adds it’s important that Genentech can use any vendor’s flow or temperature devices as long as they’re HART-compatible. “If a device that we wanted had a HART option, we asked for it. For almost all devices, the HART capability was free from the vendor. But even if the HART option cost money, we still purchased it,” he recalls.
Remote Configuration Nearby
The ability to view instrument health is available in Genentech’s DCS without added hardware. “We’re able to view/modify instrument configurations without interrupting process monitorBiotech’s Digitaling,” Kerls explains. Analog Future “Managing our instrument config- Genentech chose HART While the university’s because buses such as experience with HART Profibus, Foundation urations reduces our regulatory is more traditional, fieldbus, and DeviceNet Genentech’s attraction had issues concerning risk and our risk to product.” to HART focuses on their design, which is the protocol’s availabildifferent from HART ity and innovative use at the Vacaville’s CCP2 and its 4-20mA capability. “ It takes more time to facility. There, the company is implementing get other buses operable. We get the most benefit HART with 15% of the I/O. via HART,” he adds. Number one on Kerls’ list of “There are a lot of instrumentation manufacturers HART benefits is an enhanced view of the instruthat offer HART-compatible products,” says Kerls. ments., which includes status, alarming informaThat availability plus a huge installed base makes tion, and remote configuration. HART a proven technology, he adds. “This is techGenentech also values the HART protocol’s renology that’s going to continue to be supported and mote capabilities. “The biggest bang for the buck developed. It uses the same 4-20mA wiring you’d use is remote configuration and monitoring. HART in traditional I/O, so there’s no steep learning curve.” won over all the other buses,” Kerls asserts, “beHe emphasizes this means reduced installation costs cause it provides remote capabilities, installation and reduced risks during startup. simplicity, and met our requirements.” Kerls adds that HART’s simultaneous analog and Remote device setup and configuration is essendigital communication capability is a key attribute tial because it allows Genentech to easily backup to the protocol’s value. “We’re able to implement instrument configurations using a central dataHART communication over familiar 4-20mA base. The firm also can make changes to instrutwisted-pair signal cable, a proven and simple inment configurations from a controlled database stallation method,” he says. “There are no addresscompliant with 21 CFR Part 11 (Title 21 Code ing schemes, network-sizing concerns, or special of U.S. Federal Regulations Part 11: Electronic communication requirements to deal with.” Records; Electronic Signatures from the U.S. Food Genentech reports it also chose HART because and Drug Administration). Kerls adds this was its Honeywell instruments are HART-enabled. “So, possible without relying on handheld devices or we need no new infrastructure other than a new technicians’ hand-written notes. database server. The information is seamlessly integrated throughout the I/O, DCS controller, and the Overall Configuration is Crucial process data server,” Kerls says. In other systems, Central configuration management is another area however, he believes multiplexers or other devices where Genentech will use the HART protocol. The are needed to pick up digital signals. “With the company will use a database to capture, view, verify, Honeywell system, HART data is tightly integrated, test, and backup instrument configurations for more so information is available right in the DCS.” than 1,125 instruments during the startup of CCP2. S-10 Advertising supplement to CONTROL
tale of two plants “HART protocol with the online configuration-management database eliminates the need for a time-consuming paper process,” says Kerls. “It probably saves an hour off each calibration which basically is a half a person-year saved under normal operations. In initial documentation of parameters and startup, this may also save 3,000 hours. These are very conservative estimates.” Compared to traditional I/O, Genentech can use HART to diagnose an instrument just by opening a view, rather than sending someone out to the device’s location. “If anything goes wrong with that device, it’ll notify the operator though a DCS alarm,” he adds. Genentech reports that HART-associated work at CCP2 is enabling more efficient management of instrument configuration. “Once we get this up and running, part of corporate automation engineering’s role is to disseminate information about the project throughout the corporation,” says Kerls “This also means educating our maintenance group on our systems’ capabilities and developing efficient processes to leverage HART-enabled technology.” Another benefit includes building the corporation’s instrument configuration-and-calibration Standard Operating Procedures (SOP) on how to use the HART protocol and Genentech’s configuration management database. “We’ll continue to minimize the time required to perform configurations and calibrations,” Kerls emphasizes. “You can put these technologies in, but if you aren’t educating your lifecycle group— maintenance and the local automation engineering group—to use them, then the corporation never gets the full benefit.”
Compliance Protects Doses Diagnostics. Maintenance. Regulatory compliance. SOPs exist for them. All are taken seriously at CCP2, and HART plays a crucial role here, too. “Our HART devices are installed as part of an 8,500-I/O DCS. Any device errors or alarms will automatically be available to the operators/technicians,” explains Kerls. HART allows Genentech’s staff to receive device-specific alarm values, which reduces troubleshooting time. “On a new plant, we don’t really know what the issues will be,” Kerls says, “but we expect that we’ll find them quicker, which goes directly to the bottom line. Our HART implementation will ensure that the current conS-12 Advertising supplement to CONTROL
figuration is always correctly backed up.” And, if an instrument needs replacement, HART simplifies this process. “We download the backed up configuration for the old instrument from our HART configuration management database. These parameters upload to the new device through the analog I/O card,” says Kerls. “Effectively managing our instrument configurations reduces our regulatory risk and risk to product.” Risk to product usually means producing less at poorer quality. “If a critical instrument is involved and you can’t prove you had adequate control over properly configured devices, it could lead to regulatory action and/or a recall of the entire batch,” says Kerls. “You’d have offline analytical measurements so you might not lose the batch, but you might spend a lot of time defending it.”
Tips from the Field Correct monitoring, particularly with HARTenabled instruments, also concerns Lowery, who offers tips for users. “HART device diagnostics is only as good as the vendor’s device description (DD) file. The more detailed the DD file, the more diagnostics you’ll have,” he explains. Lowery also suggests ensuring that the DCS analog I/O is HART-enabled. “Using a third-party solution to strip out and send HART data via a serial connection will likely prevent using HART digital PVs in a fast changing loop,” he says. ■
Future’s Surface Only Scratched Ohio State’s experience with HART was so positive that the power plant’s staff is examining tracking the drift of the analog PV compared to the digital PV. Also, there’ll be more use of HART device diagnostic faults in the control strategy, says Lowery. Ohio State also plans to evaluate using a field device manager (FDM) for configuring HART devices, rather than using HART communicators. “This will help us catalog devices. We’re told that if you replace a device, when you plug it in, the DCS will automatically give it its tag and other operating information,” he adds. Overall, Kerls is even more optimistic about the role of HART in Genentech’s future. “If HART works well at CCP2, we can just roll it out to other Genentech plants,” he says. “If you use HART, you’re going to save big time in lifecycle management because the installation cost is no more than if we installed traditional I/O systems.”
hart users win big
HART Champions Stay Competitive Reliable communications via HART bring large gains to many process projects
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he HART Communication Protocol provides the toolkit for process champions. It imparts this through a global installed base of more than 20 million HART-enabled devices. This is extraordinary because HART debuted just 20 years ago, and only became an open standard in 1990. Not surprisingly, all major industrial-automation suppliers support HART. Pick any process measurement and control application, and HART is there. The protocol assists in chemical production, water desalinization, as well as pulp and paper, natural gas and steel production. It helps manage wastewater facilities. And it’s in OEMs’ pressure and temperature metering devices. So, why does HART enjoy such popularity? End
users say it’s simple, reliable, robust, flexible, easy to use, rugged and cost-effective. They also know that HART keeps their businesses competitive by providing simultaneous analog and digital communications, as well as interoperability. We asked several end-users how they’re using HART to keep their plants competitive. They report that they’re gaining efficiencies and saving money by better using their installed assets, and using the intelligence in their HART-enabled field devices. By tapping into this information, they’re now working smarter and keeping competitive. The investments in many cases are small and the returns are big. Creative? Yes! Difficult? No! The key is just getting started!
Appleton Paper targets better asset management To win in the paper-coating game, pulp-and-paper producer Appleton Paper implemented HART in an addition/upgrade to a coating machine in its facility in Appleton, Wis. The company installed more than 100 HART-enabled flowmeters, control valves, and pressure sensors. The papermaker targeted several criteria for the project. 1) Minimize costs for hardware, software, training, spare parts, etc. 2) Find a simple, robust system to inform staff about device health. 3) Use that system in other applications. 4) Get a database for configuration, tracking, troubleshooting, etc. 5) Obtain access to all instrument/device data. “HART gave us the best opportunity to expand with the rest of our existing control systems at the lowest costs,” says Chris Van Sambeek, Appleton Paper’s control systems technician. The ultimate goal was better asset management. Appleton uses HART via a leading supplier’s PLCs and a supporting supplier’s HART-enabled I/O system to link its smart instruments to Emerson
Process Management’s AMS package. Appleton enhanced its instrument-configuration capability and preventive maintenance with HART’s better troubleshooting capability. “So far, HART has been very effective,” says Sambeek. Appleton also saved by installing and configuring fewer transmitters. “HART saved us roughly $40,000 on wiring alone with its ability to pull multivariable information from our mass flowmeters,” adds Sambeek. Using AMS for commissioning, Appleton also saved money and time by remotely configuring devices. HART technology saved another $10,000 or so because the company now needed 12 fewer pressure and 12 fewer temperature transmitters. Sambeek says HART also improved operations in other areas, including “better diagnostics; control-loop validation by pulling information into the PLC through the HART signal; increased plant availability; better product quality and utility; higher product yield; lower Advertising supplement to CONTROL S-15
hart users win big operations-and-maintenance costs; and enhanced regulatory compliance.” Appleton succeeded with HART because the protocol was a better fit for expansion than other fieldbus technologies, adds Sambeek. Finding a new HART smart card that the PLC system could use also helped Appleton. This card allowed the company to upgrade existing systems with minimal equipment and costs, says
Sambeek. “Most of our existing instruments are HART-enabled, and the HART cards used are compatible with our existing control systems.” And, installing an OEM’s HART-enabled cards into Appleton’s control PLC platform allowed the paper company to use HART data in both the AMS and control systems. “HART provides additional information not available to normal analog systems,” Sambeek adds.
V-F Controls reduces troubleshooting time V-F Controls Inc. in Mentor, Ohio, provides flowmetering systems to petrochem and steelmaking companies, and to the district-energy market for custody transfer. “Often, we assist in commissioning,” explains Jim Weinstein of V-F. “However, process conditions often aren’t as originally anticipated.” This means initial set-up of the instrument must be changed. “HART allows us to make changes in minutes, compared to hours if we used analog electronics.” “Troubleshooting is a dream with HART. One of my first HART installations was a steam-flow metering system with differential-pressure, pressure, and temperature transmitters. The signals were sent to a flow computer,” he recalls.The transmitters were located on the piping near the ceiling of a high-bay building. “The customer had done the installation and wiring, and then called to tell us that the transmitters were indicating totally erroneous readings on the flow computer,” says Weinstein. “When we visited the site to troubleshoot, we agreed.” “I thought this would be a good time to try out our new HART communicator. I hooked it up to the pressure-transmitter terminals on the flow computer, and established communication with
the transmitter,” says Weinstein. “It came back and said, ‘I am a temperature transmitter.’ ” Without the HART-enabled devices, it would’ve taken longer to detect the bad setup. “It probably would have taken us an hour just to get 50 feet in the air to start troubleshooting.” Weinstein says that HART adds loop-validation functions to V-F’s applications like the ability to identify the transmitter at the end of the loop or driving a 4-20mA signal in the loop to verify proper response at a flow computer, chart recorder, or indicator. “These capabilities not only identify proper wiring terminations, they help us find potential ground-loop issues and configuration errors in the transmitter or secondary electronics,” he states. Weinstein’s a longtime HART fan. “HART is simply the only way to go for quick start-up, re-ranging, and troubleshooting,” he says. “The fact that it is a standard is most important when systems involve different vendors’ products. “I’m not aware of any standard for digital communication on a 4-20mA loop. As proprietary protocols fall by the wayside, more instrument manufacturers jump on the HART bandwagon. Why carry two or three communicators, when you can carry just one?”
Persian Gulf becomes drinkable The Saline Water Conversion Corp.’s (SWCC) AlJubail Phase 1 desalination and power plant was built on the Persian Gulf in 1982. The facility has six 60-megawatt power plants and a desalination plant. A recent re-instrumentation project involved adding more than 2,000 HART-enabled devices from various manufacturers. “Despite the size of this mega project, HART Communication helped us to the core,” says T. Veeresh Prasad of Yokogawa Engineering Asia. “HART also achieved best resolution and accuS-16 Advertising supplement to CONTROL
racy of the data, compared to the old devices that were in place for the past 20+ years.” Prasad also appreciates that HART technology’s analog and digital communications are simultaneously available. “Analog communications helped because of our fastest turnaround time requirements,” says Prasad. “Digital helped quickly calibrate and troubleshoot issues, including controlvalve-positioner feedback.” Something else that worked best for the project was HART technology’s response time at the host
hart users win big system. “In terms of asset management, all the devices couldn’t give enough information to the host system,” says Prasad of the plant’s pre-HART days. The protocol’s interoperability also allowed SWCC to integrate a Yokogawa’s Plant Resource Manager (PRM) asset management system, using
HART-compatible input/output (I/O) cards. The staff now uses PRM to crosscheck status. The result? “HART is a very reliable platform for fastest response requirements of control and automation/ safety-instrumented systems. It will compete with all other buses, all the time.”
Sewers safer in Wisconsin The Milwaukee Metropolitan Sewerage District (MMSD) recently installed more than 200 level transmitters with HART interfaces in manholes. The new instruments were needed because the former level instrumentation wasn’t temperature compensated. HART technology’s analog functions allowed an intrinsically safe barrier and installation calibration in these explosion-proof areas. “The collection-system manholes are typically entered yearly for calibration checks,” explains Eugene Moe, senior instrumentation and control engineer for Earth Tech Inc., Sheboygan, Wis., which jointly manages MMSD’s operations. “The result is an
installation that reduces time to calibrate the instrument, and eliminates the need to enter the manhole, unless the unit fails.” “It’s not critical that the signal and calibration be available at the same time,” he explains. “But the dual functionality allows seamless operation of the system while the instrument is being interrogated and updated.” Moe asserts that using HART-enabled devices saved money for MMSD, and adds those savings, coupled with the technology’s flexibility, reliability and field ruggedness, are why HART devices are used throughout Milwaukee’s sewage-treatment system.
Eastman Chemical eases the pressure At Eastman Chemical Co.’s operation in Longview, Tex., pressurized tanks may have an allowable working pressure of 63 psig, which may be 10 times more than the span of the pressure transmitters. According to Josh Lowery, electrical engineer at Eastman Chemical, pressure variations in those tanks can cause problems. On startup, one tank’s pressure shot up, and popped a relief valve. A solution using HART technology includes only one transmitter, rather than two as required before. “We use the HART signal to read the actual value at the cell, and so read the full range of the transmitter,” says Lowery. This means operators can determine the actual pressure without re-span-
ning the transmitter. “We can strip the HART signal, and get full range from transmitters in which the scale has decreased,” he says. “When we have upsets where the process went out of the expected range, we can capture the actual reading from the HART signal.” HART’s remote-configuration capability has improved operations at the Texas facility. “HART saves us the time we used to spend going to and from the instrument,” Lowery says. “More importantly, hazardous-area work requires many more permits. Hooking up with HART in the control room is much easier.” Remote configuration also allows Eastman to verify field wiring from the control room.
Australian Steelmaking glitches vanish Australian steelmaking giant OneSteel’s Whyalla SteelWorks in South Australia annually produces approximately 1.16 million metric tonnes (1.30 million tons) of steel. In the electromagnetic stirrers at this facility, OneSteel uses a major vendor’s calibrator to reprogram its HART field instruments and control elements. OneSteel chose HART technology for a new analog/digital interface because older systems caused S-18 Advertising supplement to CONTROL
problems. “I read about the HART system and its efficiency, so I pitched the idea to my manager,” recalls Jeremy Pereira. “And, well, here we are.” Fully functioning means more efficiency. Every system can be monitored and adjusted remotely, adds Pereira. “It doesn’t have anywhere near as many glitches as our old system.” That’s a blessing, he says, because it requires fewer technicians. “So, it definitely saves money and, more importantly, time.” n
Team hart scores
Users Want Suppliers’ HART Solutions on Their Teams End-users implement suppliers’ HART-enabled tools to operate their businesses better, faster, and more simply. This is the essence of what keeps them competitive.
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esides the benefits HART gives end-users through approximately 20 million installed devices, its success also comes from its partnership with suppliers of HART-enabled technologies. These suppliers include the world’s major control-and-instrumentation vendors, such as ABB, Emerson, Honeywell, Invensys, MACTek, Magnetrol, Moore Industries, ProComSol, Siemens and Yokogawa. It’s no secret why end-users keep coming back to these and other suppliers—HART is a gamechanging solutions enabler. “We offer HART because our end-users worldwide expect us to support this capability,” declares Magnetrol International’s Dave Miller. Eric Olson, ABB Automation Products’ business unit manager, adds, “HART is the most widely installed intelligent device technology today, and it continues to deliver significant benefits. So, of course, we remain a strong supporter.” By implementing and using suppliers’ HARTenabled technologies, such as smart field devices, end-users know they can be more competitive. Suppliers’ smart-HART solutions lower operating costs by allowing quicker device set-up and commissioning, and by enabling protocol interoperability via easy integration of multiple vendors’ technologies. Suppliers’ HART technologies also improve process control, increase safety-instrumented-system (SIS) integrity levels, and smooth troubleshooting and maintenance. These tasks also become less disruptive because HART grants access to 30-40 S-20 Advertising supplement to CONTROL
data items—such as process variables, device status, diagnostic alerts, loop current, and percent range— built into suppliers’ HART devices. Another reason end-users rely on these suppliers is because HART provides simultaneous 4-20mA analog and digital channels or signals over one pair of wires. Analog gives the PV, while digital provides real-time connection to intelligent field devices and their information. This analog-digital combination also provides better control security and loop integrity.
HART Suppliers Guide Users to Future T.S. Prasad Raghavendra, Honeywell Process Solution’s product manager for HART solutions, believes two key improvements will drive future growth. The first is HART 6. Its protocol revisions will offer better support for multivariable devices and actuators, more device and variable-status information, and some new and extended commands. Enhanced electronic-device-description language (EDDL) is the other advance fueling growth, says Raghavendra. By expanding device description language (DDL) capabilities, EDDL establishes a new industry standard for advanced visualization of intelligent-device information, while maintaining DD technology’s integrity.
Smart Devices Get Smarter One recent upgrade involves Emerson Process Management’s Version 8.4 of its DeltaV system software. It uses standard HART device-status information to generate Emerson’s PlantWeb alerts
Team Hart Scores for any HART-enabled device. This gives end-users products released in September. “More products access to the predictive-diagnostic functionalities will follow before year’s end,” explains R. L. in those devices. Doing this can prevent abnormal “Rick” Gorskie, senior product marketing manplant operating situations and enhance smart SIS. ager for Honeywell’s Industrial Measurement and HART fully integrates with the analog signal, and Control (IMC) pressure/temperature products. allows end-users to adopt it at their own pace and within their budgets, adds Jim Cobb, marketing Competitive Asset Management director of Emerson’s Rosemount Division. “HART Besides these advances, HART technology still instruments allow us to provide cost-effective inneeds to be configured. Consequently, configuranovations with a technology that isn’t disruptive to tion tools also keep end-users coming back to customers’ operations and maintenance practices.” suppliers of HART-enabled technology. These tools Likewise, Moore Industries’ HIM HART loop make it easier for end-users to integrate HART into interface and monitor is another innovative tool that operations. And, as these tools become easier to use provides process and diagnostic information that through suppliers’ upgrades and new systems, endwould be otherwise unavailable with smart multivari- users get more out of their HART-enabled systems. able transmitters and valves. All an end-user has to “As HART data becomes more integrated into do is install HIM into a critical loop. control and asset-management systems, Yokoga“Smart/HART multivariable transmitters sense wa continues to enhance the powerful features multiple process variables,” says Steve Todd, in our flow, temperature, pressure, and analytiMoore’s corporate marketing director. “These cal devices because we know there’s an easy way transmitters perform an internal calculation to to maximize these additional capabilities,” says derive a measurement, Hoag Ostling, chief such as mass flow.” It’s no secret why end-users come application engineer Next, the transmitters for Yokogawa Field send the process variInstruments. Yokogaback to these suppliers—HART is a able to control systems wa’s HART solution game-changing solutions enabler. via a 4-20mA signal, includes integrated but Todd reports that, HART I/O modules without HART-based control systems, end-users in its CS3000 production-control system and can’t continuously monitor non-primary variables HART-compatible field instruments. used to make the calculation. When end-users integrate these with Yokogawa’s Meanwhile, Honeywell’s intelligent HART tech- Asset Excellence solutions, which provide the founnology, such as its Experion Process Knowledge dation for comprehensive, condition-based mainteSystem (PKS), also makes end-users more competi- nance strategies, users gain the intelligence inherent tive. “This is the first control system to offer I/O in protocol-enabled field devices. with native HART 6.0 support,” says RaghavBecause asset management can occur remotely, endra. “It’s also the first system to fully adopt suppliers also are helping end-users integrate that the HART Communication Foundation’s (HCF) technology into operations. “The initial customer Smart Device Configurator Model 625 (SDC-625) benefit for remote configuration via HART has reference host technology.” expanded in recent years with the addition of asset Other smart technology that makes HART intemonitoring for improved predictive maintenance,” gration easier comes from ProComSol, which now says ABB’s Olson. This has helped ABB’s end-usoffers HART-enabled, device-configuration software. ers improve productivity and lower maintenance DevCom2000 smart device communicator is based costs, he adds. ABB has increased its Smart/HART on SDC-625. This HART-compliant host software capabilities through HART-multiplexer support for accesses all HART DD features and functionality, installed systems, and with new HART-based, consays Jeffrey Dobos, president of ProComSol. “This figuration-and-calibration handhelds that support includes monitoring and editing device variables, and ABB and non-ABB devices to a device-specific level. executing all device DD methods,” he adds. Because remote connections, including wireOther new additions to HART’s smart toolbox less, require modems, end-users can implement are Honeywell’s HART 6.0-certified pressure two HART-compliant devices from ProComSol, Advertising supplement to CONTROL S-21
team hart scores including its universal serial bus (USB) HART modem, HM-USB, and its wireless Bluetooth HART modem, HM-BT-BAT. Another supplier providing access to HART data is MACTek with its Viator RS232 and USB HART interfaces. These HART-compliant technologies allow a host PC to communicate to a HARTenabled device made by any supplier, according to Thomas Holmes, MACTek’s president. “What this means to end-users is that these modems work the first time,” Holmes emphasizes. This capability means end-users can communicate with their HART-enabled devices without worrying about the modem’s reliability or capability when serving in an industrial environment, he adds. In response to today’s trend of connecting smart devices via PCs to configure and manage intelligent device lifecycles, Holmes reports that a PC-HARTmodem combination lowers costs, and makes device configuration easier, especially with many parameters. Another advantage of this combination is its improved use of device capabilities that suppliers build in to produce and maintain database configurations, Holmes notes. These capabilities may be used, for example, in radar tank-level applications to display the shape of a tank. End-users may use these data to diagnose device health, validate operations, and to replace instruments.
EDDL Aids Operations Suppliers also offer new solutions involving HART’s EDDL enhancements, which fit into Smart/ HART technologies, and integrate easily into endusers’ industrial operations. These include improved user interfaces with support for menus, windows, tabs and groups, as well as added graphic support for graphs, trends, charts, and dial indicators.
EDDL further standardizes the user interface for managing intelligent devices, and eliminates the need for Windows resource files, supplemental files, and other modifications, previously required by some asset-management applications. In fact, Invensys Process Systems’ Foxboro Automation unit recently announced plans to embed HART’s SDC-625 technology into Foxboro’s process automation system. “This HART technology will enable customers to take advantage of the new enhanced EDDL,” says Betty Naylor-McDevitt, Foxboro’s marketing director. Automation and control device vendors can program sequential interactive steps for calibrating and starting up field devices in EDDL, she adds. And enhancements to EDDL let device vendors define user interfaces for plotting, trending, and storing device data. To make EDDL more available through HART and other fieldbuses, Emerson and Siemens Automation & Drives announced a new technologysharing effort in July. They’ll expand some systems to give end-users more access to HART and other fieldbus standards. Siemens will add interfaces to its Simatic PCS 7 process-control system and its Simatic process device manager. Emerson will expand its DeltaV and Ovation control systems and its asset management system (AMS) suite. The two companies plan to release their first products in this cooperative effort in mid-2007. Through all of these new technologies and upgrades to existing ones, suppliers have helped HART become widely accepted by global customers. “HART’s efforts to take this ‘communication standard’ to the next level with Release 6.0 shows its drive to remain one of the world’s premier communication options for the process control industry,” adds Honeywell’s Gorskie. n
Affordable DD Based Configuration Using Your PC ProComSol, Ltd designs and manufactures both the hardware and software needed to perform complete HART device configuration and monitoring using your PC. DevCom2000 software uses the registered DD’s from the HART Foundation, allowing full access to all device parameters, including Methods. The HM-USB USB HART modem and the HM-BT-BAT Bluetooth HART modem offer significant cost savings and productivity benefits. Units meet industry standards for USB, Bluetooth, and HART connectivity. Order this affordable solution online using our secure website.
ProComSol, Ltd
Process Communication Solutions Tel. 216.221.1550 • Fax 216.221.1554 • www.procomsol.com • [email protected] S-22 Advertising supplement to CONTROL
HART FORWARD
Use The Tools You Have S
ome tools sit in your toolbox and are rarely used. Other and other intelligent device information into the control, tools are attached to your tool belt and used daily. In asset management or safety system. This supplement is some cases we overlook the added benefits and capabilities loaded with useful tips on how to identify projects that that a tool can provide because, well, we just don’t think of provide a high ROI and significant value to your operation. it that way. Do you think of HART as a tool in your toolbox In this supplement, we review how small and gradual inor one that is on your tool belt and used daily? vestments will enable plants to avoid unplanned shutdowns Remaining competitive in today’s global economy is no and unnecessary maintenance costs. Optimizing your assets small task. We need every possible resource and asset maximized “HART Communication is one to provide that competitive edge of those tools that might be needed to survive. We spend time wishing for things we might like to in your toolbox but needs to have and in reality the wish might be moved to your belt!” be sitting right in our toolbox. HART Communication is one of those tools that might be in your toolbox but needs to be and increasing the efficiency of your staff contribute to moved to your belt! When you open it up, you will find a making HART a low-risk and cost-effective decision—one powerful, easy to use and cost-effective field communication that is easy to deploy and to justify. Finally, we identify the protocol solution that lowers operating cost, increases plant benefits of the enhanced Device Description Language and availability and helps with regulatory compliance. Based on wireless HART. We continue to invest in HART technology the industry standard 4-20mA, this robust, low-risk protocol to make sure it addresses your need to remain competitive. is the right tool for the job. Regardless of the make and vintage of your control system or In this 5th annual HART supplement, we present ideas, the type of HART-enabled field devices you may already have information and testimonials on using the POWER of installed, there are many solutions available from the 160+ HART and getting more from what you’ve got installed. HART Communication Foundation member companies that HART is the tool you can use to make your plant run more can help you put the POWER of HART to work in your plant. efficiently by putting it to work with your plant automation, Get more from the HART devices you’ve got working in safety and asset management systems—maximizing your you plant. Why? Simple—in order to become or remain assets. As pointed out in this document, HART-enabled competitive. You need to think of HART as the tool you projects are easy to find, install, use, and to justify. In most use daily to solve critical problems or better yet, identify cases, the pay back is quick and benefits significant. and avoid them before they become problems. Field instruments are becoming more intelligent and Getting more information is as easy as contacting your more open with advanced functions and diagnostic features device or system suppliers or by visiting www.hartcomm. that are powerful tools to achieve corporate objectives. org. The HART Communication Foundation is here to eduEnabled by HART Communication, today’s control systems cate, train and assist you to get more from what you’ve got and I/O interfaces can painlessly integrate the intelligent in- and to UNLEASH the POWER of HART. formation from these devices and put it in the hands of plant Is HART on your tool belt? personal to maximize and optimize the operation. New tools & technology enhancements like the DD-IDE development environment, HART 6 and the enhanced Device Description Language contribute to HART’s ability to be one of the most useful tools on your belt. Ron Helson We will help you identify big opportunities when you Ron Helson, Executive Director, move from part-time to full-time communications with HART Communication Foundation HART-smart field devices and the integration of diagnostics 512-794-0369; [email protected] Advertising supplement to CONTROL S-7
HART VALUE
I
t’s ironic; in their endless quest to reduce costs while increasing output and quality, many manufacturers have been ignoring one of the most potent technologies for achieving those ends. Not only that, it’s a technology in which most of them already have made substantial investments! The technology? HART. For years, instrument and systems vendors have been incorporating HART communications capabilities into field devices, enabling those devices to send digital information, including diagnostic information and secondary variables, to host systems. (The HART Communication Foundation estimates that more than 15 million HART-capable devices are installed worldwide.) But with the exception of maintenance personnel tramping into the field with handheld communicators to configure instruments, most users have left HART’s benefits untapped. Those days are coming to an end, however. Instrument vendors are providing open access to their devices through readily available device descriptions; control systems providers are including HART I/O hardware in their products as well as asset management software; and many vendors are marketing products that enable the owners of legacy, analogonly systems to access the power of HART. So, with HART data more accessible and potentially useful, key questions users face are: What’s the best way for my company to access that data? How do we identify applications in which we can use HART to generate business value?
A Brief History HART, an acronym for Highway Addressable Remote Transducer, was developed in the late 1980s and became publicly available in the early 1990s. Unlike other recent field communications protocols, such as Foundation Fieldbus and Profibus, which are totally digital, HART is a “hybrid” analog/digital technology. An instrument’s primary variable is transmitted via the industry standard analog 4-20 mA signal, but up to four secondary variables and device diagnostic information can be digitally “piggybacked” on it. As a result of these digital communications capabilities, users have access to extensive data from their devices, including diagnostic information and -- in the case of some instruments -- multiple process variables (i.e., a pressure transmitter also might be capable of providing temperature data).
In 1993, the HART Communication Foundation (HCF) assumed ownership of the protocol and responsibility for administering and maintaining it. As part of its mission, HCF tests systems and devices for HART compliance and provides educational services to vendors and users. In HART’s early years, many instrument vendors quickly adopted the technology, but the remote connectivity was complex due to the need for additional wiring and hardware, such as multiplexers. Sandro Esposito, Masoneilan’s diagnostic product manager, says this lack of seamless connectivity created “islands of automation” for the user. Charlie Piper, fieldbus product manager for Invensys’ Foxboro business unit, agreed. “There are more than 500 different HART
People are realizing that HART is capable of delivering many of the same benefits as fieldbus. devices in the marketplace, and there’s lots of information you can get about their performance, such as when valve positioners are starting to wear out or stick,” he says. “But until recently no one had come up with a way for all the host vendors to have a user interface to do these neat things with everyone else’s devices.” Today, however, most vendors make their Device Description (DD) files openly available. HCF maintains and distributes a library of hundreds of DDs that enable any HART host (e.g., control system, configurator, asset management system, safety system, etc.) to communicate with a vast array of field devices. That development is coupled with the development of comprehensive applications to monitor assets, such as Siemens’ Process Device Manager, Emerson Process Management’s AMS Device Manager, and Honeywell’s Asset Manager PKS. As a result, users now are able to access most – if not all – of their device information from a single screen, regardless of device manufacturer. In recent months, HCF has developed new tools and technologies to make development of HARTcompliant DDs easier. These include the new Device Description Integrated Development Environment (DD-IDE), which is designed to streamline development, testing and maintenance of DDs and facilitate the creation of product applications with Advertising supplement to CONTROL S-11
HART VALUE DD capabilities. “The DD-IDE supports the iterative DD development style with a fast and efficient integrated tool set. Each step in the edit-build-test cycle is supported in a DD-aware editing environment,” says Wally Pratt, HCF’s chief engineer. Also near completion is the Enhanced Device Description Language (EDDL) specification. EDDL gives vendors the ability to add new capabilities to
Keys to HART value • Identify the most critical loops in your plant first and begin monitoring them via HART on a full-time basis. Other less essential loops can be monitored offline periodically. • An outsider can bring fresh perspective. So consider bringing in an outside consultant to help you identify areas where you can realize maximum benefit from HART-based solutions. • Make a business plan to determine if the cost of incidents is higher than the cost of investing in HART-enabled I/O. • Employ a diagnostic tool to monitor loops and field instrument performance and identify potential troublespots that could benefit from full time monitoring via HART. • Take advantage of resources and training provided by HART Communication Foundation. • While HART is used primarily for equipment monitoring and configuration purposes, don’t overlook opportunities to use it in appropriate control applications. DDs while improving cross-platform compatibility and facilitating device set-up. (See details elsewhere in this supplement.) HART-enabled instruments deliver greater value than ever before, says Dave Smith, manager of Yokogawa’s plant network technology center. “The processing power of the devices is increasing greatly,” says Smith. “Therefore, field instruments feature additional functionality, including diagnostic type functions, predictive functions and others.” Jim Cobb, marketing manager of Emerson Process Management’s Rosemount Division, notes that users are increasingly aware of the capabilities of the digital field. “One of the reasons is that suppliers are better implementing features to use the capabilities of HART devices,” says Cobb. “Another reason, ironically, is that there’s been so much talk about fieldbus in recent years. People S-12 Advertising supplement to CONTROL
are realizing that HART is capable of delivering many of the same benefits as fieldbus.”
Identifying High-Value Applications Industry experts are nearly unanimous that the greatest return on HART technology investment lies in the ability to continuously monitor the field instruments. Masoneilan’s Esposito notes that drastic reductions in maintenance staffs during the past decade have made automated monitoring of field instruments an absolute necessity in many plants. By being able to watch and track the condition of plant floor devices, maintenance and operations personnel can spot problems in the making and take action before they cause process upsets and unplanned shutdowns. Conversely, being able to see that a device is working well enables users to avoid unnecessary maintenance activities. “If you have a lot of HART devices in your installation, and you’re not monitoring them on a continuous basis, you’re missing a great deal of opportunity,” says Tom Holmes, president of MACTek, a manufacturer of HART modems. “There’s diagnostic information, alarms, alerts and confirmations of whether the analog signal is good or bad.” Industry experts recommended a number of strategies to help users identify the most high-value applications involving continuous monitoring. Emerson’s Cobb suggests that plants go about taking advantage of HART gradually. “One of the nice things about HART is that you can add its capabilities to your plant, loop by loop, and gradually take your facility from analog to a fully integrated HART plant,” says Cobb. “I’d start with online monitoring of my most critical assets. That’s where I’m going to get the most value from predictive diagnostics, such as being able to avoid unplanned shutdowns and preventing off-quality products,” adds Cobb. “At the same time, I might start using HART to monitor other instruments offline and gradually, as my maintenance budget allows, bring other assets online.” Marcelo Dultra, vice president of sales and marketing for Smar International, recommends plant audits as a means of identifying areas ripe for improvement via HART. “They should do a full check of what equipment they have installed and what technologies they’re using. This kind of thing usually takes a maximum of two or three days,” says Dultra, who adds that Smar, as well as other vendors and consulting firms, provide such services.
HART VALUE “It’s always good to get opinions from outside the plant, from people who have seen other operations. If you work a long period in your own plant, you miss some points that are important, especially when it comes to the technologies available today,” he adds. Prasad Raghavendra, Honeywell’s product manager for all systems-related HART products, recommends that users review a history of process upsets and their causes to identify areas that are ripe for HART-enabled continuous monitoring. “Make a business plan out of that to determine if the cost of incidents are higher than the cost for investing in HART-enabled I/ O,” says Raghavendra. “That’s a fairly simple method that would clearly indicate whether it was worth it for the customer to make the investment.” In some instances, he says, the benefits from investing in HART will be plain. “For example, your plant could be having problems caused by simple incidents like sensor failures. If you’re simply relying on a 4-20 mA signal, the operator will see a local trip, but everything in that group of devices becomes suspect. This requires the operator to call maintenance and initiate what could be an extensive debugging process. With HART, however, if there’s a sensor failure, the device tells you that it’s the source of the problem, saving you time and resources in correcting the malfunction.” “Processes that could benefit the most from this technology are those with a large number of remote-connected HART devices that can be brought in to a control system through a remote HART I/O,” says Eric Olson, a senior product manager with ABB. “This could include processes such as those in the oil and gas or wastewater treatment industries, where there are many satellite I/O stations.” Foxboro’s Piper recommends that users employ a diagnostic tool such as ExperTune’s PlantTriage, to monitor loops and field instrument performance and identify potential troublespots that could benefit from full time monitoring via HART. HART can play an important role in refineries, mills and power plants that employ process safety systems. To maintain a system’s Safety Integrity Level (SIL) rating, safety system valves must be periodically tested to ensure that they will move if called upon in an emergency. Full-range tests can be conducted only during plant shutdowns, but these occur only every two to three years. However, by stroking a valve by as little as 10 percent, which does not disrupt a process, plants can ensure the reliability of their safety valves. A valve positioner has the ability, via HART, to conS-14 Advertising supplement to CONTROL
firm to operators that the valve actually responded to the movement command. Robert Hotard, a product manager with instrument-maker K-Tek, also suggests that users take advantage of HCF’s expertise in planning HARTbased projects. “The first thing I’d recommend to anyone interested in HART is to go to the Foundation’s website (www.hartcomm.org),” says Hotard. “There’s a lot of information there that’s available to everyone and explains in great detail how to use the protocol and the benefits that are possible. I’m currently writing some manuals for K-Tek products, and in them I specifically reference the HCF website.”
Don’t Overlook Control Opportunities While most facilities use HART for applications related to device configuration and maintenance, users also should look for opportunities to use HART data for process monitoring as well. For example, in applications where conditions such as temperature, pressure and levels change relatively slowly, users can reduce the number of instruments they need in the field by acquiring multiple variables from a single device. Hotard points to tank farms as being ideal sites in which to make use of HART for applications such as inventory monitoring. (see accompanying story). In relatively small operations, users can set up modest, but effective SCADA systems that utilize HART technology, says Mactek’s Holmes. “You could continuously monitor up to eight points using a PC equipped with eight USB HART modems. That’s very do-able,” says Holmes. “For software, you could use a dedicated data acquisition package such as Wonderware’s InTouch software, or something as basic as a Microsoft Excel spreadsheet. I think there are plenty of operations such as bakeries or small specialty chemical plants that can’t justify spending the money for a large control system. But with HART input and a PC, you can build yourself a quick and dirty DCS,” he adds. Liberate the Genie Having HART capabilities at your disposal, but not taking advantage of them, is like keeping the genie stuffed in the lamp. By carefully examining your facility, looking at the HART capabilities you already have, and carefully weighing the need for additional investments, you can take full advantage of opportunities for improvement.
JUSTIFYING HART
Selling UP! Justifying HART Investments to Management
“A
no-brainer!” “Mom and apple pie!” “So obvious, it’s barely worth discussing!” These are some of the immediate responses from systems and instrumentation suppliers and users when asked how maintenance and operations departments should go about justifying investments in HART technology to plant managers. But a no-brainer to a plant maintenance manager may not necessarily strike the same chord with a senior financial manager. Consequently, personnel who want to start reaping the benefits of HART need to develop strategies that take into consideration the HART capabilities the facility already has (e.g., installed HART instruments, HART I/O, etc.), additional investments needed, and the benefits the company will realize from those expenditures.
Intelligent Field Communication
The no-brainer attitude stems from the fact that most plants already have made substantial investments in HART technology. So, say the experts, it only makes sense to put those capabilities to use. “If you’ve bought 4-20 mA instrumentation in recent years, chances are good that it’s already HART-enabled,” says Prasad Raghavendra, a
A no-brainer to a plant maintenance manager may not necessarily strike the same chord with a senior financial manager. systems product manager for Honeywell. “And if you’re considering buying new instrumentation, the incremental investment in buying HART-enabled devices rather than those capable of only 4-20 mA
• HART data integration with control, asset management and safety systems • Systems communicate with HART devices “full time”– both 4–20mA and digital
HART Data
ERP CMMS HMI
Control
• Systems detect impending problems and provides alerts • Continuously validates control signal integrity
HART I/O
• Automatically detects deviation in device/system data • Continuous device diagnostics • Multi-Variable device data available to improve operations
HART Field Devices
Advertising supplement to CONTROL S-17
JUSTIFYING HART is extremely small. So it becomes easy to decide to go with HART without having to make a big case.” If you’ve purchased your control system during the past few years, odds are good that it has native HART I/O, meaning you can bring the digital HART signal, including diagnostic information, secondary process variables, etc., directly into the system. In addition, HART Communication operates over existing wires, so much of the physical infrastructure you need already is in place. Most plants, however, will have to invest at least a small sum in equipment and/or software to take advantage of HART capabilities. These include HART multiplexers, which strip the HART digital signal from the 4-20 mA signal and route it to PC-based software applications equipped to accept HART input; and HART modems, which are PC I/O cards that enable users to communicate with devices via HART. In putting together a case for those investments, maintenance and operations departments should stress to management the situations that won’t occur as a result of using HART. Specifically, HART will enable plants to avoid unplanned shutdowns and
unnecessary maintenance, particularly on valves. “You’re going to make your workforce more efficient, because you can get them focused on working on the right stuff,” says Jim Cobb, marketing manager for Emerson Process Management’s Rosemount Division. “This is especially true of the valve diagnostics. It’s probably the one that hits you right in the face.” Being able to keep an eye on valve performance via HART and compare it against valve signatures will reveal to plants when the device actually needs maintenance. ‘If your current mode of maintenance involves shutting down every six months and checking valves, transmitters, etc., the use of HART may enable you to reschedule and reduce those activities,” says Marcelo Dultra, vice president of sales and marketing for Smar International. “If you can show that a valve can run eight or nine months, you might not have to shut down every six months. There’s enormous value in that.” In plants that employ safety systems, testing safety valves periodically is absolutely essential. Af-
Inergy’s Bakersfield Plant Moves Gas With HART Inergy, headquartered in Kansas City, Mo., is a major provider of propane and services to 600,000 customers. While most of its operations are in the Southern, Midwestern and Northeastern states, the company operates a natural gas liquids site in Bakersfield, Calif., that includes processing, storage and terminal services. Propane manufactured at the facility is stored in bullet tanks, each of which holds 10,000 to 15,000 gallons of propane. It is critical for the company to monitor levels and temperatures in each of the containers, since propane expands as temperatures rise. If pressure increases too much, the company must vent gas into the atmosphere and risk violating stringent California environmental regulations. Ken Clifton, instrumentation and electrical supervisor at the plant, says personnel used to rely on sight glasses and “spinner” gauges mounted in the tanks to visually judge levels. “Our people would have to actually go out there and look at the tanks to determine the levels,” he says, adding that it was inefficient. To improve the situation, Inergy decided three years ago to install field instruments in each S-18 Advertising supplement to CONTROL
tank that would send readings on temperature and level back to Inergy’s control system. “We could have put separate temperature and level transmitters into each of 40 tanks, but that involved quite a bit of instrumentation and wiring. Instead, we purchased instruments from K-Tek, each of which was able to monitor both of those variables,” says Clifton. The transmitters send 4-20 mA level readings back to the plant’s programmable logic controller equipped with a HART gateway and use a HART digital signal to communicate temperature and level information. Using the two readings, the system is able to calculate the level in each tank accurately and display it on the system’s HMI. “With this system, we’re able to get two readings for the price of one, and it’s worked well for us,” says Clifton. “We’ve had a few minor problems, but none involving use of the HART Protocol.” “In fact,” adds Clifton, “all the instrumentation we put in this plant has the HART Protocol, because it makes troubleshooting easy for our instrumentation techs.”
JUSTIFYING HART
The HART Difference Analog 12 mA
Control System
+4–20 mA
Two Simultaneous Communication Channels • 4–20mA channel—fast, robust & reliable • Digital two-way communication channel for device status, diagnostics, alerts, etc.
ter all, the last thing you want is for a valve to stick in an emergency. Under IEC and ISA safety system standards, a plant system’s probability of failure on demand can be reduced by increasing the frequency of system testing. Increasing frequency once was impractical for many plants, since valves could only be tested during shutdowns. However, plants now can run partial-stroke tests in which a valve is moved only a small percentage of its full range, to ensure that it functions properly in emergencies. If the valve actuator is HART-capable, the device can confirm its actual movement to operators and maintenance personnel. Even in terms of day to day safety for workers, HART can play an important role. Norit Americas manufactures activated and reactivated carbon at its plant in Pryor, Okla. The manufacturing process requires the usage of acid, coal, steam, burners and compressed air, creating a hazardous work environment. By replacing conventional analog monitoring devices with HART-capable devices, maintenance personnel are able to run diagnostics and perform calibration checks and even make adjustments from the safety of the equipment control room through the use of a handheld set. In addition, the plant recently installed an asset management system workstation in its maintenance building, allowing personnel to work on HART-capable devices without leaving the structure. Fritz Geiger, a systems product manager with Siemens, notes that HART Device Descriptions enable users to store all or nearly all of their instrument data in a single database, thus improving organization, reducing expenditures on multiple pieces of equipment and software, and making more efficient use of personnel. “This provides high benefit for the user,” says
HART Transmitter
35–40 Data Items Standard in Every HART Device! • Device Identification • Calibration Data • Process Variables • Diagnostic Alerts
Geiger. “He may have thousands of instruments and has to keep all of those different ranges and parameters updated. The best way to do that is to have all of the information available in a single database.” Sasol, an international chemical manufacturer, can testify to the value and benefits of HART based on its use in its South African solvents operations. In 2000, as part of the planning process for construction of a butanol plant, the company set as goals the detection of field instrumentation and valve problems before they could cause production loss; migration from run-to-failure maintenance mode to predictive maintenance strategies; a reduc-
“HART will enable plants to avoid unplanned shutdowns and unnecessary maintenance, particularly on valves.” tion in control valve maintenance expenditures; and improved change management. Sasol saw HART-based asset management as the means for achieving these ends. Among the benefits the company realized through the use of HARTbased asset management just in the past two years are savings of nearly $2 million on prevention of plant trips, the avoidance of unnecessary repairs, and detection of faulty or poorly optimized valve positioners. Obviously, no two plants are alike, and results that each can achieve through the use of HART can vary widely. Based on their experience working with a wide variety of users, systems and instrumentation vendors have come up with a number of implementation tips to consider and pitfalls to avoid: Advertising supplement to CONTROL S-19
JUSTIFYING HART Implement solutions gradually Emerson’s Cobb notes that HART can be effectively implemented gradually, by tiers, making it easier to budget investments over a long period. ”At the low end of investment, you can stay offline and simply monitor loops on a manual basis periodically. This can be done in the field with a handheld communicator or by hooking up a PC equipped with asset management software, including data on all your instrumentation,” says Cobb. “At the next level up, you can establish
“You’re going to make your workforce more efficient, because you can get them focused on working on the right stuff.” continuous monitoring via a separate asset management system. And, beyond that, if your plant has invested in a control system with HART I/O, you can bring the secondary variables directly into it.”
Rely as much as possible on existing equipment Steve Todd, marketing director for Moore Industries, which manufactures HART multiplexers says, “We’ve found that customers that stand to gain the most from HART technology are the ones that can leave as much existing equipment in place as possible, yet still make significant, cost-effective process improvements. For example, if a customer wants valve position feedback at the control room, he can go the traditional route and run additional wiring back to the control room that provides this data. This gets expensive fast. A second alternative, though, is for the customer to leave everything else alone, and install smart HART controllers on the existing valves. Then, extract the stem position data from the HART digital data using a HART interface instrument installed in the control room.” Demand interoperability from vendors “While HART is a very open protocol, not every company subscribes to it,” says Honeywell’s Raghavendra. “Consequently, buyers should make sure from their vendors that the field device and/or system fully complies with the protocol as defined by the HART Communication Foundation. Customers also should encourage their vendors to register their devices with the foundation.” S-20 Advertising supplement to CONTROL
Be specific about your goals Be specific about how you want HART to meet your needs, advises John DuBay, instrumentation product manager for Meriam Process Technologies. “Predictive maintenance is a great story, but many end users aren’t sure what diagnostics they’re looking for. If you ask them about the specific diagnostic capabilities they’re interested in, they’re not always sure.” Provide easy access to HART data To achieve the benefits of online configuration and diagnostics, operations and maintenance personnel need to cooperate. However, that situation often is the exception rather than the rule, says DuBay. “Not many operators are eager to open up access to their maintenance crews because they’re fearful that devices could be reconfigured incorrectly or by accident.” Know where the ROI is coming from Masoneilan Digital Product Specialist Leo Hughes advises that users should not expect to get substantial maintenance-related ROI from new HARTenabled digital valves. “The big rate of return is on the existing valves,” says Hughes. “You can graph a valve’s performance over time and see that it plateaus at a high level of performance when it’s new. You want to know where’s the drop-off from that plateau, and how steep it is.” Minimize scan time with multiple masters If you plan to use HART to continuously monitor your field devices, update parameters, and cyclically read additional values, make sure you have a suitable number of HART masters, says Siemens’ Geiger. “If you just have one master talking to 32 field devices, you’ll wind up with scan time of five or 10 minutes. You don’t want that.” It’s about work processes, too Technology alone won’t deliver HART benefits if your workforce fails to alter its work processes. “If they continue to do everything in the same way, even after they’ve put in some of these HART connections and asset management software packages, they’re not going to get the payback that they should,” says Cobb. “They need to change their work practices to take advantage of the fact that the transmitters are delivering more, very valuable information.”
FUTURE HART
HART to the Future! HCF turbocharges plant communications with Enhanced Device Description Language and Wireless HART
H
ART has been a mainstay of process automation for more than a decade, but don’t mistakenly equate its maturity with stagnation. The HART Communication Foundation (HCF) staff and its members have been working for the past several years on enhancements that will increase the HART protocol’s value to users. The fruit of those efforts will become evident during the coming months with the release of the new Enhanced Device Description Language (EDDL) and a wireless version of HART. EDDL represents an “upgrade” to the DDL that has been an important component of HART Communications since the very beginning. Instrument vendors use DDL, a text-based language, to write Device Descriptions (DDs), which are binary files that identify their products to a host system and provide the system with their operating parameters. (DDs are analogous to driver files provided to PC users by the makers of printers, scanners and other peripherals. The driver allows the PC to recognize the device, configure it and control its operation.)
EDDL Benefits
Organizations responsible for other digital field communications protocols, including Fieldbus Foundation and Profibus Nutzerorganisation (PNO), have adopted the use of DDL as well. In 2004, the International Electrotechnical Commission designated DDL as an international standard.
“Wireless HART will improve their ability to establish full-time digital connectivity to field devices. It will lower the cost to add points to a HART network, reduce wiring and make sensing more ubiquitous throughout installations.” As “smart” field instrument technology progresses, suppliers embed more capabilities in them, including the ability to transmit information on additional variables, perform increasingly complex math functions, provide more sophisticated diagnostics, etc. As a result, configuring asset man-
Device Suppliers • Covers all devices—from simple to complex • Efficient development of DD’s • Operating System independent • Stable EDD Users standard • Universal tools for all devices • Lowers devel• Consistent look & feel opment and • Highly reliable and robust support costs • Safe operation • Compatible with existing devices • Protect investments • Lower maintenance costs • Lower training cost
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FUTURE HART agement and control systems to use this abundance of information has become a more complex task. Complicating things further is the fact that vendors must develop and maintain separate DDLs for every different host system. To ease the burden on users and vendors alike, HCF, the Fieldbus Foundation (FF) and PNO have been working together for the past three years to develop an enhanced version of DDL that gives vendors the ability to add new capabilities to DDs while improving cross-platform compatibility and facilitating device set-up. More recently, the OPC
Foundation joined the development effort. Ed Ladd, HCF’s director of Technology Programs, says some vendors already have added EDDL capabilities to their products and adds that major systems vendors will incorporate it into control systems starting early next year. To make their systems EDDL-capable, systems vendors must add an EDDL Host Service Module, which will be available from HCF, FF and PNO. Among the most noteworthy improvements enabled by EDDL is instrument vendors’ ability to use DDs to dictate the look and feel of graphical
EDDL Enhances HART Communication • Electronic Device Description Language (EDDL) is the most installed and important digital communication descriptive
conforming to HCF, FF, PNO and OPC specifications all use EDDL as a means of interpreting device parameters.
language in the manufacturing and process industries. • The EDDL enhancements provide new capabilities to • EDDL is a text-based language used to describe the
benefit users in taking full advantage of the intelligence
standard and unique characteristics of field devices.
in millions of smart HART-enabled measurement and
HART was the first protocol to implement EDDL - which
valve actuator devices. The enhancements provide users
enables suppliers of HART-capable instruments to
with more information about the connected device while
define and document their products in a single, open
giving device developers the tools they need to provide a
and consistent format. This format is readable by many
consistent look and feel, regardless of the host application.
devices including handheld communicators, control systems, PC’s and other process interface devices that support DDL.
• The EDDL enhancements include improved data visualization and display capabilities – like waveforms and valve signatures, a standardized method to access
• Automation suppliers use EDDL to create Device Descrip-
historic measurement or device performance informa-
tion (DD) files that provide a standardized method for
tion and enhanced tools for high-level information
host systems to access and display valuable parameters
– such as algorithmic relationships for complex device
located in field instruments so that the full capability of
parameters - display and use in control systems.
the device can be accessed via the protocol. • EDDL enhancements include an improved user interface • EDDL is used to describe such parameters as device
with support for menus, windows, tabs and groups and
status, process data measurements, device diagnostics,
added graphic support for graphs, trends, charts and
multi-variable measurements and device configuration
dial indicators. The enhanced EDDL further standard-
information in a digital format. As applied in the HART
izes the user interface for managing intelligent devices
Protocol, this digital information is imposed on top of
and eliminates the need for Windows resource files,
the industry-standard process control signal of 4-20mA.
supplemental files, and other DD modifications previ-
EDDL allows the control system to read and format this
ously required by some asset management applications.
information making it valuable to the user. • The new EDDL enhancements enable users to interact • Developed in a cooperation with Fieldbus Foundation,
with their intelligent devices in new ways. Graphs,
Profibus and the OPC Foundation, the enhanced EDDL
charts, and calculations assist in the configuration of
extends the capabilities of Device Description Language
devices including complex instruments such as digital
to provide an industry-standard solution for advanced
valve controllers, radar level gauges and multivariable
visualization of intelligent device information to main-
meters. The enhancements also support storage of
tain the proven integrity of existing DD technology
historical data from field devices for troubleshooting
across all four communication technologies. Devices
and diagnostics.
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FUTURE HART interfaces to instrument information and set up, regardless of host platform. “Using the current DDs, device attributes show up in a hierarchical tree,” says Ladd. “But with the new interface options and graphical capabilities, device suppliers create actual windows that enable users to see all of the pertinent information about
“Some vendors already have added EDDL capabilities to their products and major systems vendors will incorporate it into control systems starting early next year.” intelligent instruments. And, with the exception of things like colors, fonts, etc., that data will appear the same way on System X, System Y or System Z.” Because vendors will not have to develop or maintain DDs for each host system that communicates with their field devices, development and maintenance of device description files should be far less complex, he adds. EDDL also will enable the incorporation of graphical elements, such as valve signatures, x-y graphs and bar charts, directly into the displays, eliminating the need for separate applications to display the data, says Ladd. The enhanced DDL also allows persistent storage of data related to field devices. For example, users will be able to store multiple valve signature files generated by DDs and compare them to their valves’ current states, enabling users to more easily and quickly evaluate each device’s performance and whether maintenance is necessary. EDDL also allows vendors to include in DDs instructions to host systems to execute advanced math functions that provide users with important information about the status and operation of their instruments. Wireless HART represents the other imminent improvement to the HART protocol. Today, HART enables communication of a device primary value over standard twisted-pair wiring, using a 4-20 mA signal, while secondary values are digitally “piggybacked” on the analog signal via Frequency Shift Keying or Phase Shift Keying. With Wireless HART, the primary value may still be carried via wiring, but users will be able to use a wireless S-26 Advertising supplement to CONTROL
signal either to supplement or replace the wired transmission of digital data. HCF’s Wireless HART Working Group, comprising representatives of numerous instrument and systems providers, began development of the Wireless HART specification late last year and set March 2006 as the goal for completion of the specification, says Kelly Orth, distinguished technologist with Emerson Process Management’s Rosemount Division and leader of the working group. “HART is a very lightweight protocol, so it is relatively simple to ‘tunnel’ HART messages inside wireless data packets,” says Orth. “At this point, we’ve generated a list of almost 50 requirements of how we want a Wireless HART system to behave.” Orth estimates that only 5 to 10 percent of users who have installed nearly 15 million HART-enabled devices use anything more than their 4-20 mA analog capabilities to communicate with higher level systems. As a result, most users are missing the opportunity to capture data that can vastly improve their operations and maintenance capabilities. “Wireless HART will improve their ability to establish full-time digital connectivity to field devices. It will lower the cost to add points to a HART network, reduce wiring and make sensing more ubiquitous throughout installations,” he says. The Wireless HART Working Group is considering a “mesh network” architecture for the protocol to deliver reliable communications. Unlike pointto-point networks, in which all nodes communicate directly with a line-of-sight “base” station, mesh networks allow nodes to communicate with one another, establishing ad hoc, redundant paths to the base. “This improves reliability,” says Orth. “If a particular path is blocked, there are other ways for the message to get through. Mesh networks also scale well. You just add more repeaters or routers without having to add much power. Also, the bigger a mesh network is, the more reliable it is, because more redundant pathways are automatically created.” Point-to-point networks are really just a subset of mesh networks, so the Wireless HART solution will cover these applications as well. As part of the development of Wireless HART, the working group is coordinating its activities with other industry wireless organizations, including the ISA SP100 Wireless Committee, to ensure continuity and uniformity with wireless standardization efforts currently under way.
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Get Connected with HART
P
OWER. For centuries peoRegardless of the make and vintage of your conple have tried to harness, trol system or the type of HART-enabled field create and control it. In today’s devices you may already have installed, there are economy, the ability to use the many solutions available from the 150+ HART power at your disposal is the Communication Foundation member companies name of the game. Corporate that can help you put the POWER of HART to work objectives typically include: lowin your plant. ering cost, increasing availability, HART is the easy, low-cost, low-risk and highimproving operations and optimizing assets. In this 4th annual HART Sound familiar? Field instruments are supplement, we present ideas, becoming more intelligent with advanced information and testimonials on functions and diagnostic features that are powerusing the POWER of HART ful tools to achieve corporate objectives. Enabled by HART Communication, today’s control systems and I/O interfaces value field communication solution that most can painlessly integrate the intelligent information likely is already installed in your plant. Put it to from these devices and put it in the hands of plant work, get your control system in continuous conoperators to maximize and optimize assets. tact with the intelligent capabilities of your smart In this 4th annual HART supplement, we present field devices—Use the POWER and see what ideas, information and testimonials on using the HART can do for you! POWER of HART and putting it to work with your Getting more information is as easy as contacting plant automation, safety and asset management sysany of your device or system suppliers or by visiting tems for maximum benefit. As pointed out in the www.hartcomm.org. The HART Communication first article, HART-enabled products are easy to Foundation is also here to educate and help you to ● install, easy to use, and easy to justify. The pay back UNLEASH the POWER of HART. is quick and within your grasp. The article “New Value from Your Asset Data” identifies big changes that have occurred concerning realtime communications with HART-smart field devices and the integration of diagnostics and other intelligent device information into the control system. There are many ways to get and use the HART data in your conRon Helson, trol systems–the key is to start today! Finally, the artiExecutive Director cle “Ready for HART? Pick a High Value Project to HART Communication Foundation Start” provides valuable tips from users of the technol512/794-0369; [email protected] ogy on how to maximize your investments. Advertising supplement to CONTROL
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The Power is In Your Hands Looking for a Digital Field Network? With HART, It’s Right in Front of You
A
t BP’s PTA (Purified Terephthalic Acid) plant in Wando, S.C., managers are facing a dilemma familiar to their counterparts at thousands of manufacturing facilities throughout the country: do more with less. “BP is interested in maximizing our competitive position. Our objective is to lower costs and increase our availability. We need to use what we have and use it better,” says A.J. Lambert, an instrument and electrical reliability specialist with BP. One way plant personnel are achieving that goal is by using a previously underutilized technology that is providing them with a remarkably detailed view of conditions throughout their plant and the ability to reduce asset management/maintenance costs. The “silver bullet” that’s generating these benefits: the HART Field Communication Protocol. “Through the use of HART diagnostic information, this BP plant is saving a hundreds of thousands of dollars per year in maintenance and production costs,” says Lambert.
Feel the Power Of course, not every plant will attain such dramatic
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results, but most users can achieve all, or nearly all, of the functionality they seek by tapping into the proven power of the HART-enabled field devices they may already own. As a result, most of the benefits they achieve through the use of HART communication drops right to the bottom line. HART’s exceptional value to process manufacturers lies in its ability to simultaneously communicate an instrument’s primary variable via a standard 4–20 mA analog signal and additional process variables and diagnostic information via digital signals on the same wire (See accompanying article). Initially, HART was embraced by maintenance staffs who were delighted to be able to use handheld communicators and calibrators, such as those made by Meriam Process Technologies or Emerson Process Management, and take them into the field. All they had to do was attach them to any HART-compliant instrument—regardless of manufacturer–and they were immediately able to retrieve critical information about an instrument’s condition, its health and its range. They could also perform and document calibrations and obtain much more digital information besides.
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Since then, manufacturers have developed a wide range of new intelligent products and added HART capabilities to existing ones, providing even greater benefits to a broader base of users. For example, field device makers such as Siemens differentiate themselves by communicating additional HART data that is unique to the company’s instruments. Siemens pressure transmitters have the ability to monitor and store data on the highest and lowest pressures experienced by the entire instrument, the instrument’s pressure capsule and its electronics, says Lou DiNapoli, marketing manager for the company’s pressure and temperature transmitters. “All users have to do,” says DiNapoli, “is use a HART handheld device or our Device Description Language (DDL)-enabled Simatic Process Device Manager (PDM) software to get that information, which is highly useful in diagnosing process problems. If you use someone else’s equipment and software, you need the Device Description for our instrument.”
Sophisticated Asset Management
HART, we pull only five or six valves during a shutdown. And we have a lot more information about why we’re pulling it. Our diagnostic system can show us when a problem assumed to be in a valve really isn’t, but is perhaps somewhere else in the process. In other cases, we’re able to see potential problems in valves before they become serious.” Petro-Canada, which is implementing projects at its Montreal and Edmonton refineries to reduce sulfur in its gasoline and diesel fuels, will use HART data for troubleshooting valves and field instruments, says Pat Castelino, PE, a managing engineer with the company’s process technology and reliability group. “I expect a manpower reduction in the startup phase of the project and then on a lifecycle basis,” says Castelino, when asked about potential benefits stemming from the use of HART data. “We feel that the additional information we incorporate into our asset management solutions will help us establish more effective predictive maintenance practices.” Several factors make HART solutions relatively easy and cost-effective to implement. First, HART does not require a costly “rip and replace” strategy. The HART protocol runs on standard wiring that most plants already have in place and, as mentioned, there are more than 14 million HART-enabled devices already in use. Often, field instruments that are not HART-
In recent years vendors have developed sophisticated asset management software packages, including Yokogawa’s Plant Resource Manager (PRM), Siemens’ PDM, Emerson Process Management’s AMS and Honeywell’s Asset Manager PKS, that enable maintenance engineers to view, track and analyze the condition of instruments remotely. In these Asset management systems applications, data from a device may be split into separate analog and their ability to use and digital signals. The analog signal, carrying the primary variable, HART data are proving is routed to the control system, while the digital secondary values enormously beneficial and diagnostic data are conveyed to the asset management systems. Asset management systems and their ability to use ready can be easily and inexpensively upgraded. HART data are proving enormously beneficial as Because HART represents an enhancement of the numerous users will attest. standard 4–20 mA analog field communications BP’s Wando plant started tapping the full potenstandard, there is no need for companies to undertial of HART about five years ago, when it installed take major retraining programs. Courses offered by Emerson Process Management’s ValveLink software HCF, vendors and other sources generally provide to gain diagnostic information from its approxiall the background information plant personnel mately 125 most critical control valves. need to use HART effectively. “Before using HART, we would pull out 35-50 In addition, the HART network architecture is valves for maintenance during shutdowns every two simpler than that of most all-digital fieldbus protoyears,” says Lambert. “There might have been a work cols, making it the ideal option for many plants. order or some concern about a particular valve, but “If I’m putting in a 4–20 mA system with HART, the we really didn’t know what might be wrong with it. engineering is very simplified; it’s basically a matter of As a result, we’d spend a lot of money and time. routing wires from the control system to the final eleNow, with more information from ValveLink and ments,” says a major refiner’s senior engineer. Advertising supplement to CONTROL
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Easy and Effective In addition to HART being relatively easy and costeffective to implement, plants can adopt it very gradually and realize benefits, even on a small scale. For example, many users get their first experience with HART by commissioning instruments on the “bench” in maintenance shops. All that’s required is a PC equipped with DDL-enabled asset management software and an interface between the computer and the field device–typically a HART modem. Thomas Holmes, president of HART modem manufacturer MACTek Corporation, says there are significant advantages to using a desktop or notebook computer for bench or field configuration of HART-enabled devices rather than using handheld configurators. “All of the information you need about all of the devices you use is right there on your computer’s hard drive. You can do signal processing, a host of higher-level diagnostic applications data storage,
and/or downloading of archived configurations that are right on the computer. You don’t have to go through the trouble of downloading a device configuration from a server, loading it into the handheld configurator and then reversing the process when you get out to the instrument,” he says. Besides producing modems for RS-232 serial ports, MACTek recently began producing models that use USB ports. In addition to USB ports being simpler to use, many computer vendors no longer include serial ports on their computers, making the USB version a necessity. Also, multiple devices can be attached to a single USB port through the use of USB hubs. As a result, says Holmes, some customers have been able to set up small monitoring/data acquisition systems using several USB modems. “There’s one customer doing a fiscal metering application involving custody transfers of product. He needs high accuracy and reasonable sampling rates,” says Holmes. “The application requires him to moni-
What is HART?
I
n 1993, the HART Communication Foundation (HCF) was established to provide worldwide support for application of the Highway Addressable Remote Transducer technology—or HART Field Communications Protocol. The HCF owns the HART technology, manages the protocol standards, and ensures that the technology is openly available for the benefit of the industry. The ARC Advisory Group, Dedham, Mass., estimates that, of the approximately 40 million field devices installed worldwide, 26% are HART-enabled, making it the most widely used protocol for smart field instrumentation. HART is a hybrid communications technology in which a modulated, two-way digital signal is imposed on the industry-standard 4–20 mA analog signal carrying the primary process variable. The digital signal conveys additional process variables, device status and diagnostics information that can be routed to asset management, process control and safety systems. This means that HART provides two simultaneous communication channels on the same wire–the industry standard 4–20 mA channel for fast, reliable and robust control (PV) and a digital channel for real-time communication of additional process/device information. HART includes a standardized application layer
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addressing device status and diagnostics, cyclical process data including floating-point digital value; engineering units, data quality and status. The protocol also enables field devices to continuously publish their process data and standardized operating procedures (e.g., loop test, current loop re-ranging and transducer calibration). Every HART device includes 35–40 standard pieces of information, which are easily accessible by all HART-enabled systems. These include device identification, basic calibration data, process variables (measured and calculated) and diagnostic alerts. All HART-smart field devices continuously assess and monitor their own performance and return diagnostic status information with every message. A HART innovation was the creation of Device Description Language (DDL)–an object-oriented, text-based language for modeling the characteristics and real-time capabilities of intelligent field devices. Instrumentation suppliers use DDL to create a Device Description (DD) file, which is similar to an electronic data sheet describing all capabilities of the smart field device so that the DD-enabled host systems can communicate with all device features. In early 2004, the International Electrotechnical Commission (IEC) approved DDL as an international standard.
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tor eight HART loops. They are using eight USB modems, connected to two four-port hubs, which, in turn are plugged into two PC USB ports. They’re using Emerson Process Management AMS Device Manager to monitor the equipment.” Moore Industries’ HART Interface Monitor (HIM) is another product particularly well-suited to small
of terminations you have to do per point for field devices,” says Pat Moyer, Rockwell Automation’s marketing manager for distributed I/O. Like a multiplexer, smart, distributed I/O separates the analog and digital signals and routes them to the appropriate systems. Multiplexers, including those manufactured by MTL Instruments, enable users to simplify their wiring and scale up their sysThe digital feedback on tems incrementally. For example, by using MTL’s MTL4840 HART connecthe valve position also tion system, users can connect nearly 8,000 loops to a single PC communicacan be used in safety tions port and easily configure a scan list and get LED indications of the loop system applications, being scanned, says Tess Thonger, a MTL marketing manager. a burgeoning application Because HART delivers many of the same benefits as all-digital fieldbus profor HART technology tocols, it’s not surprising that there’s confusion in some potential users’ minds about the technology. Part of the and medium-sized installations or those that lack problem stems from users’ mindset based on their an asset management system, says John Emmett, initial exposure to HART, says Jim Cobb, Emerson Moore’s London-based HART specialist. Process Management’s Plantweb marketing manager. The Moore Industries HIM passes the 4–20 mA sig“It’s a little bit of a case of HART having been nal directly into a DCS or a PLC, but it also breaks out around long enough that people think they know it, the digital signals, converts them to analog and makes but in reality, they only know the surface,” says them available to the control system as well for alarmCobb. “Now, when you see some of the systems that ing and other functions. are coming out today, they have pretty good HART Using the two alarm relay contacts in each HIM, support. As the systems vendors start educating users can set limits around process variables. their customers, that’s going to be the most impor“For example, with a smart valve positioner, you tant way the message gets out to the users.” have the control system using a 4–20 mA signal to Joe Serafin, Honeywell’s product manager for HART drive the valve open and closed. Using an HIM, you integration, says Honeywell tells its customers that can read the valve position feedback over the same their choice of field communication protocols should pair of wires and return it to the control system. In be dependent on what they want to achieve. “If they’re addition to there being a cable savings, the alarm interested in peer-to-peer control on the wire, we tell relay contacts act as ‘soft’ limit switches. So you can them to go with Foundation fieldbus. But if they don’t set a trip limit within the HIM and cause a relay to want to do that, they can probably get everything else close when the valve reaches its limit,” says Emmett. they want out of HART,” says Serafin. The digital feedback on the valve position also can In for the Long Haul be used in safety system applications, a burgeoning Few industry observers question that, in the long application for HART technology (see sidebar). run, the process industries will eventually migrate to Other components that enable users to implement fieldbus protocols. But don’t even think about and expand their HART-based field networks are mothballing your HART devices anytime soon. smart distributed I/O modules, such as those proHART combines the reliability and robustness of vided by Rockwell Automation. today’s analog signal with the power of tomor“Instead of running all of the wiring back to the row’s digital field network. Considering the milcontrol room from each individual device, our FLEX lions of HART devices already installed, the most I/O is out near the field and brings the data back via a responsible action for the industry is using HART network. This reduces long home-run wiring runs ● to its full potential. from multiple field devices, and it reduces the number
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New Value from Your HART-Enabled Assets
W
hile HART provides users with enormous value through the exchange of digital data via asset management and maintenance systems, the value of that data would leap if users could integrate it into their real-time control systems. Fortunately, that’s now possible. Major control vendors who offered HART as well as their own proprietary digital field protocols (e.g., Yokogawa’s BRAIN, Honeywell’s DE, Foxboro’s FoxCom, etc.) have yielded to user demand and enthusiastically embraced HART. Today, virtually every major automation system vendor includes native HART I/O in their control systems, meaning users can now integrate secondary variables into their control schemes, ensure that their analog 4–20mA signals represent the actual situation in the field, and troubleshoot problems quickly to minimize process disruptions. “A control system can be considered to have full HART capability if it supports true, full-time communication with both the digital and 4–20mA analog signals of HART-enabled field devices,” says Wally Pratt, chief engineer of the HART Communication Foundation. Other important factors are smart HART-enabled I/O with HART capability at every channel (as opposed to being multiplexed or shared across several channels); controllers that are HARTaware, enabling them to use HART data; and the ability to display HART data on operator stations.
Source: Emerson Process Management
HART in the Control System Lets Users Realize Great Gain Without the Pain
With HART-enabled field devices, operators can detect and correct costly process overload and other dangerous conditions.
New Valuable Capabilities Users who implement HART-enabled control systems gain new, valuable capabilities. Among the most important is the ability to validate their process data. As reliable and time-proven as 4–20 mA signals are, external electrical noise, faulty instruments and other problematic inputs can produce errors that are not immediately apparent. “In control systems with HART I/O, the 4–20mA signal can be validated continuously,” says Pratt. “The I/O continuously checks the loop current for agreement with digital values being sent by the
device. If there is a disagreement, the problem shows up immediately on the operator interface. “Information where you continuously monitor valve position versus the desired setpoint that you’re sending can represent a major cost savings, because if the valve is not tracking the setpoint, then your control strategy is in jeopardy. There’s no way to do advanced control if you don’t know if the valve is going to the position you want,” Pratt adds. HART capabilities in control systems also enable users to quickly detect field device problems. If a Advertising supplement to CONTROL
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system is able to display an instrument’s self-diagnostics data as well as changes in device status, process disruptions can be avoided, since operators can spot and react to the problem quickly. The availability of multivariable device data also enables operators to anticipate situations they might not be aware of otherwise. According to Pratt, “Most HART-enabled pressure transmitters also have ‘temperature’ as a secondary variable. Wouldn’t it be nice to be able to have the instrument tell the control system when the instrument temperature is about to drop below freezing, so a heater can be turned on, either manually or automatically? All you need is the ability to read that secondary variable. You can save downtime and possibly avoid damage to your equipment.”
Detect, Correct, Protect In addition, HART data enables operators to detect and correct process overload conditions. If a loop current becomes saturated, readings go “off the scale,” and the operator essentially is blind to the situation in the field. Often, the problem stems from the process measurement being out of range, but determining the source of the problem typically requires dispatching an instrument specialist to the field. However, if the control system is receiving the instrument’s digital data, the operator is able to see the actual values the instrument is generating. Standardized device status alerts also assist the diagnosis by indicating whether the process condition is outside the sensor limit or just outside the 4–20mA range. The net result is a reduced need for emergency manpower and the pos-
HART’s Critical Role in Safety System Testing
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he HART protocol’s bi-directional, digital communication capability has given the technology a vital role in the testing of safety instrumented systems that protect people, the plants they work in and the environment. By their very nature, valves in a safety system remain stationary nearly all the time, but in those rare instances when they’re called upon to bring about the safe shutdown of a process, they must work without fail. The only way to ensure that a safety system valve will function when it’s needed is to periodically test it. In fact, the length of time between tests has a major effect on the system’s Probability of Failure on Demand (PFD), a factor in determining the System Integrity Level (SIL) under industry regulations governing safety systems. Lengthening the interval between tests has a linear affect on the PFD. So, if the length of time between tests is doubled, the PFD is doubled as well. “Therefore, it is imperative that these valves be tested frequently in order to reduce the PFD and meet the target SIL rating,” says Riyaz Ali, development manager for Emerson Process Management’s FIELDVUE instruments. The answer: partial stroke testing. Stroking a safety valve as little as 10% does not have a significant effect on the ongoing process, but it provides enough travel to determine the valve’s responsiveness in emergency conditions. What’s necessary in this situation is feedback from a positioner to verify that the valve actually
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has moved, as expected. Consequently, some vendors are providing that capability via HART. “The HART protocol defines a device-status byte, which is determined by the HART standard,” explains John Emmett of Moore Industries International. “It says things like‘ a signal has gone over-range’ or ‘a signal has locked up.’ There are eight defined states in HART protocol, one of which is called ‘additional status available.’ That’s the one that allows manufacturers to build in their own special features, like partial stroke testing,” notes Emmett. “Our HART Interface Module can pick up signals like ‘test in progress,’ so we can actually indicate back to the control system that a partial stroke test is happening. But more importantly, the smart positioner can detect if the valve is stuck. We can pick up that particular alert and alarm back to the control room,” adds Emmett. Emerson Process Management notes that users of the Fisher DVC6000 Series of digital valve controllers and Emerson’s AMS ValveLink software for emergency shutdown solutions do not require the presence of personnel in the field because the controller’s software is able to to provide feedback on positioner information via HART. In addition, they can automatically initiate partial stroke testing routines. Many plants using this technique have extended their intervals between scheduled shutdowns–results that appear on the bottom line!
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With HART, processors can increase plant availability and lower operating costs.
sible avoidance of unnecessary downtime. enabled control systems are created equal. While The availability in a HART-enabled control system some provide one-to-one I/O, others rely on multiof multiple variables from a single instrument gives plexed data, which creates latency. While this does users the ability to put that data to work in their not matter a great deal in some applications (in control schemes. which variables do not change frequently) in other “For example, one of our customers is thinking applications such latency is unacceptable. about doing his own level of condition-based mainteEven with multiplexed systems, however, users nance by taking additional information provided by can install products, such as Moore Industries’ HART the valve—such as the number of strokes or closed Interface Module, on critical loops and place them in times–and integrating it into the process logic,” says “burst mode.” In burst mode, a field device continuDave Smith, manager, Plant Network Technologies, ously publishes data to the module. “It’s a faster way Yokogawa Corp. of America. The decision process will Another advantage to routing indicate that, if a valve has reached a level of operation as HART signals to a control measured by the number of strokes, the packing is worn and system rather than a the process should switch to a different valve, perhaps autoseparate entity is its matically, says Smith. “This is a big improvement architectural simplicity over previous ways of doing things, which involved looking at the process variable and of getting information, but in addition, burst mode deciding whether it was good or bad,” he adds. doesn’t require the host to poll the devices, so there’s Inherent Architectural Simplicity less overhead on the control system,” says Pratt. Another advantage to routing HART signals to a No matter which control system users pick, or the control system rather than a separate entity, such as means that the system uses to incorporate HART an asset management system, is its architectural simdata, they are positioning themselves to use a signifplicity. “There’s a lot less hardware, which means a icant source of data at the heart of the process that lot less risk,” explains Smith. “The capital expendimight otherwise go untapped. With this additional ture is lower, and you don’t need multiple PCs, information in hand, operators and engineers have multiplexers and other components.” the ability to lower operating costs and increase ● Pratt cautions, however, that not all HARTplant availability. Advertising supplement to CONTROL
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Ready for HART? Pick a High Value Project to Start When Implementing HART, Experts Advise Start Small, But Think Big
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f it’s apparent to you that HART’s potential benefits go way beyond taking readings with handheld configurators in the field, you may be thinking about taking some careful steps toward tapping your HART-enabled field instruments for value. But like most journeys, the first steps are the most intimidating. Where to begin? What to expect?
Look Before You Leap
itor up to 32 of the plants most important loops,” says a senior engineer with a major oil refiner. “That way, you can start to realize that you can monitor the health of your instrumentation and start moving from fighting fires and suffering capacity loss to being able to detect instrument health issues before they have an impact on your business. Once you’ve proven the value to yourself and your management, expand to other critical areas of the facility.” Carefully evaluate your expenditures–As mentioned earlier, nearly every plant has at least some of the components it needs to begin realizing HARTenabled benefits. Before investing in additional hard-
Fortunately, you can implement HART a little at a time, so look for projects with the most potential value, start small, expand gradually, and be willing to take a few prudent risks. Become the HART champion in your organization–Users If there are areas in which you involved in all aspects of plant operations have a role to play in think HART can be advantageous implementing HART and attaining its benefits, and in most to your business, why not step companies, no single group “owns” HART. Consequently, up and drive the effort? you have an opportunity to be a HART champion in your organization. If there are areas in which you think HART can be advantageous to your ware and software, evaluate what you already have and business, why not step up and drive the effort? determine how much more you actually need to invest. Select a proving ground–The fact that even the “You need a good asset database, so you can figsmallest HART implementation can yield benefits ure out what the critical points are in your plant, with minimal investment can relieve some of the because they’re the only ones that really need smart risk and anxiety that naturally accompany upgrade instrumentation,” says Louis Reeves, who is in projects. Pat Castelino of Petro-Canada recommends charge of control valve asset management at Internathat users start small and carefully evaluate areas tional Paper in Pensacola, Fla. ripe for HART-driven improvements: “It’s a big waste to spend a lot of money on mar”People should start off small and find very spevelous technology where you don’t really need it,” cific projects that they feel comfortable with. And Reeves adds. “It’s like getting an 800-horsepower then, they should actually go through the learning engine for your Ford Mustang. Where are you going process, deciding and quantifying benefits at various to drive it, and are you really going to use all of that stages,” he says. Several other users and vendors had horsepower? I don’t think so.” more specific recommendations along those lines. Joe Serafin, Honeywell’s product manager for HART “A plant can begin by using a single multiplexer integration, says his company has a series of questions and a stand-alone asset management system to monusers can ask their instrument vendors to determine Advertising supplement to CONTROL
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how much information is available from their devices. ”Which version of the Universal Commands (HART 5 or HART 6) does the device use? What secondary process variables are available from the device? Does the device support HART Command 48 for devicespecific status? Are all available device information and features defined in the Device Description? These are the kinds of questions users need to ask in order
Even small HART implementations can yield plant-wide benefits.
to determine, with all HART’s potential, if the vendor’s put it into his product,” says Serafin. Think in terms of benefits, not just technological capability–“If they say HART is the answer, then my question is ‘How do you want to use the data?’ ” says Steve Lazzok, a support specialist with Yokogawa Corp. of America. “If they don’t know, it means to me that they may be wasting their money until they have a clearer plan in mind. If you’re going to bring in the data, how are you going to make or save money from it? How are you going to implement preventive maintenance? How are you going to reduce accidental shutdowns? The user should consider these questions before making investments.” Conversely, however, you should not be afraid to invest in HART technology on at least a small scale, even though the immediate payoff might not be apparent, says Dave Smith, manager, Plant Network Technologies, Yokogawa Corp. of America. “I know that ‘technology for technology’s sake’ is a difficult issue in our business, but could you have imagined 15 years ago that you’d need an Internet browser to do your job? Sometimes technology gets you someplace that you wouldn’t have dreamed,” Smith adds. Users have indicated that getting the project approved is easier when you can show the ability to implement HART Communication without having
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to shut down processes. Question vendors thoroughly–While on a superficial level, it might seem like every vendor offers a similar level of support for HART in their systems, in fact capabilities vary widely. Consequently, HART Communication Foundation chief engineer Wally Pratt recommends that you carefully question vendor companies about their products “HART-ability.” For example, if you’re evaluating Smart I/O, topics for discussion with your vendor should include: ● How much HART capability is built into the I/O? ● Can the I/O validate and secure the 4–20 mA signal? ● What is the ratio of HART modems to I/O channels? How often does it update HART data to/from a device. ● How well does the system support access to multivariable device information? ● Can you merely “push a button” on the I/O to calibrate the loop current and/or check the range? ● Does the I/O support multi-drop? ● Does the I/O automatically scan and monitor the HART–enabled field devices or is the scanning only possible using “pass through.” ● Does the system make it easy to use all HART capabilities? “Some vendors say, ‘Yes, we can use the HART data,’ but it might take a little more training in one system vs. another to configure the thing. You want it to be easy,” cautions Pratt. ● Does it understand HART Status? ● Can the system detect configuration changes? “Ask questions about notification by exception. How does the system detect changes in configuration or status? “How do you go about performing tests when there’s an error in the device?” Pratt asks. ● How open is the system to third party software? Train your staff in HART capabilities–Experienced instrument technicians and process engineers will have little trouble familiarizing themselves with HART’s capabilities and putting them to work, and it’s unlikely they’ll require much–if any–additional training. However, if you want an in-depth look at HART and the way it’s used, you can obtain training from many of the vendors who sell HART-enabled devices and systems. In addition, the HART Communication Foundation offers numerous courses globally, educational webcasts and a CD-based library of information. Need more help? Visit the ● HCF web site at www.hartcomm.org.
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Contents
9 Platform for the Future New Capabilities Make HART a Fieldbus to Be Reckoned With. The Protocol’s Evolution Includes Powerful Real-Time Applications
14 The HART of Asset Management HART Capabilities Offer Fundamental Value While Real-Time Connections Deliver Results
19 Time to Tap Into HART Seize the Data. There Are Major Asset Management and Process Improvement Gains to Be Realized With HART
23
HART Plant of the Year The Detroit Water and Sewerage Dept. (DWSD) Uses HART to Eliminate Metering Disputes, Improve Reliability, and Streamline Operations
Ad Index Advertiser
Circle No. Page No.
Emerson Process Management/PlantWeb 100
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Endress+Hauser
101
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The Foxboro Co.
102
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Harold Beck & Sons
103
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HART Communication Foundation
104
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Honeywell Industry Solutions
105
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MACTek Corp.
106
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Moore Industries
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Ohmart/Vega
108
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Siemens
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Smar
109
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Yokogawa
111
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ver the past three years, automation suppliers have introduced new control system interfaces, remote I/O systems, and software applications to leverage the intelligence in HART-smart field devices for continuous real-time diagnostics and process information. Real-time connections are the key to unlocking the riches of your installed HART devices and to helping you lower maintenance costs, increase plant availability, improve plant operations, and facilitate regulatory compliance. In this issue, we present ideas, information, and examples of putting the power of HART to work—maximizing and optimizing assets. Our 2003 HART Plant of the Year winner is a great example of unlocking the value in HART-enabled devices. The Detroit Water & Sewerage Department discovered the powerful capabilities of their HART devices—already installed—and combined them with other technologies to create a solution that satisfied their customers, their management, and their technicians. We thank those of you who submitted your plant applications for consideration as the 2003 HART Plant of the Year. Don’t miss this article because it shatters the image you might have of water system applications. Asset management is the hot topic these days and with the tight budgets I’m hearing about, you can’t afford to overlook the untapped value of HART-enabled devices. HART communication is a key enabler for asset management—so get connected and realize the potential of your installed HART devices! Regardless of your control system, the 150-plus members of the HART Communication Foundation (HCF) have costeffective solutions to help you. This year, the HCF is celebrating its 10th anniversary, and HART technology remains the protocol of choice for communication with intelligent process instrumentation around the globe. With our continued enhancements to the technology—including our focus on Device Description Language and new development tools—HART will remain the simple, low-cost, low-risk, and high-value process communication solution for your plant operations. Want to learn more? Call us—we’ll be happy to help you get connected and realize the potential of your HART applications! ◊
Ron Helson, Director HART Communication Foundation 512/794-0369 [email protected]
HART ® is a registered trademark of the HART Communication Foundation.
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Platform for the Future New Capabilities Make HART a Fieldbus to Be Reckoned With. The Protocol’s Evolution Includes Powerful Real-Time Applications
A
s part of a major upgrade to a plant in Sao Paulo, Brazil, plate and specialty glass manufacturer Cebrace sought to improve the volume and quality of data it was receiving from its plant equipment, so it could improve maintenance quality. Although the plant has a Foundation fieldbus network in place, the plant elected to rely on instrumentation using the HART protocol for the data it needed. According to Benedito Adalberto Pestana, a Cebrace engineer who worked on the instrumentation project, plant technicians were more familiar with HART
and felt comfortable relying on its proven capabilities in critical situations. Using a HART-to-Foundation fieldbus gateway developed by Smar, Cebrace operators were able to view and control instruments on both networks from the same Smar AssetView interface. “The benefit for us was the ability to pull all of our process information together, improve maintenance quality, and, most important, improve our mean time between failure,” says Pestana.
Feature-Rich While most industrial users associate HART with handheld terminals and in-
HART Technology Enhancements Increase Value to Users HART has been in wide use for more than 10 years, but the protocol continues to evolve and grow in value to users around the world. The HCF last year finalized HART 6, the latest version of the protocol. HART 6 enhancements provide additional diagnostics and many new capabilities to improve integration with plant control and safety systems—all while protecting users’ investments through backward/forward compatibility with existing networks and devices. Consequently, HART 6 systems can communicate with HART 5 instruments and HART 5 systems can communicate with HART 6 instruments. However, access to the full range of HART 6 functions requires both masters and slaves to be HART 6-enabled. New features and capabilities support multivariable and valve/actuator devices, enhance status and diagnostics, increase interoperability, and extend commissioning and troubleshooting capabilities. Among the many new features in HART 6: • Device Variable Classification: Allows control systems and other master applications to determine the number and type of processrelated variables available within a device. • Extended Device Status: Provides an additional byte for device status alerts, such as "Device Needs Maintenance." • Device Variable Status: Allows field devices to assess and report on the quality of the data being transmitted. • Catch Device Variable: Enables devices to share process data via peerto-peer communication for use in complex flow calculations or functions. • Block Data Transfer: Supports the transfer of large blocks of data among master applications and field devices.
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the-field-configuration of instruments, Cebrace and other companies are recognizing that this proven, reliable communications technology is capable of delivering much more value. HART— introduced more than a decade ago— is finally being recognized as a featurerich, highly capable communications technology that permits full-time communication among field devices and control systems. Among the benefits HART delivers to users are a reduction in costly unplanned outages through improved, real-time troubleshooting; better use of field assets; and a rich, real-time flow of data that enables users to introduce new, high-value applications for control and asset management. Meanwhile, HART’s presence in plants all over the world increases every day. The vast majority of installed smart instruments are HART-capable, and many of those that aren’t can be easily and inexpensively upgraded. In addition, the protocol is included in more than two-thirds of all smart devices now being installed. Brian Oeder, marketing manager for instrumentation maker Ohmart/Vega, noted that his company considers HART compatibility to be a basic requirement of any instrument in use or being sold today. “We don’t consider HART capability to be something special anymore,” says Oeder. “We consider it something that is absolutely necessary for doing business. We wouldn’t think of developing an instrument without HART.”
See the Light Still, despite HART’s universal presence in plants around the world, many users are unaware of the cost-effective capabilities the protocol provides and the enormous returns they can gain with vir-
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“We don’t consider HART capability to be something special anymore. We consider it absolutely necessary for doing business.”
tually no additional device investment. “When a user finally sees the light about the power of the extra information in HART, they discover that the bulk of the investment is already sitting in their plant,” says Hoag Ostling, chief application engineer with Yokogawa. “All they have to do is tap into it.” The evolution of the HART protocol is being driven by several key factors. First is the ubiquity of HART in field devices — it’s everywhere. In addition, virtually all major vendors of control systems include the native ability to communicate digitally via HART on a continuous, real-time basis, meaning users have the ability to tap the full range of data in their field devices and incorporate that information directly
into their control schemes. For those unfamiliar with HART, or in need of a refresher, a quick review is in order. HART is a digital field communication protocol that enables intelligent field devices to communicate with control systems, asset management systems, safety systems, and other maintenance and configuration tools. While HART uses the familiar 4-20 mA analog standard, it piggybacks a digital signal atop the analog that conveys a wealth of information, including secondary measurements and data useful in device and process diagnostics and monitoring. HART’s evolution from a maintenance and configuration tool to a highly capable digital network for control as well as asset management began when
HCF, Profibus and FF Enhancing Device Description Language Earlier this year, the HART Communication Foundation (HCF) entered into a collaborative agreement with the Fieldbus Foundation (FF) and Profibus Nutzerorganization e.V. (PNO) to enhance the Device Description Language (DDL) supported by all three organizations. The jointly developed enhancements will provide additional DDL constructs and functions to support the data visualization needs of sophisticated devices for full-screen graphical displays and data captures for performance assessment. The DDL enhancements will allow device manufacturers to describe display layouts and persistent data storage needs entirely within the device DD file—including graphical display elements such as photos, two-dimensional plots/charts, and data groupings by window, dialog, tabbed-dialog, table, and/or menu. DDL is an object-oriented, text-based language for modeling the characteristics and real-time capabilities of intelligent field devices. Instrumentation suppliers use DDL to create Device Description (DD) files describing the capabilities of their smart field device products. Procedures for proper operation and read/write access to device parameters are described in the device DD file. DD-enabled host applications such as handheld communicators, calibrators, control systems, and asset management systems use the DD file to display device information and interact with the device for calibration, commissioning, diagnostics, and maintenance functions. HART was the first protocol to implement DDL. For more than a decade, it has proven its value as a stable platform for suppliers to define and document the capabilities of HART-capable products in a single, open, and consistent format. DDL is the standard of HCF, but soon it will become an international standard of the International Electrotechnical Commission (IEC) known as IEC 61804-2, EDDL.
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the protocol first became available to vendors and users in the early 1990s. Technicians in the field generally attached a handheld communicator to each instrument to obtain additional HART-enabled data, calibrate, and configure the device. This provides huge benefits, but in large installations such as refineries, months typically pass before the device’s communication capability gets used again. Later, users gained better access to HART data through multiplexers, HART modems, and other devices that enable them to access the digital device data remotely and store it in PC-based applications for asset management. Typically, these systems would poll each instrument just once or twice per day in large installations—an improvement over monthly onsite visits, but still a far cry from an up-to-the-second picture of an instrument’s condition.
New View From the Control System With the inclusion of HART in control systems, however, users suddenly had a powerful new real-time technology to improve plant floor visibility, troubleshooting, and control. “We have a software tool that allows you to have a connection to all your HART devices at all times so you can view status and make changes online, without any interruption to the process,” says Andreas Aufenanger, U.S. product manager, Siemens. “Whatever changes you make to a device are instantly recorded in the same central database.” Invensys’ Foxboro automation systems contain HART input cards with eight channels, each with its own modem circuit. These features make full-time communication with intelligent field devices fast and easy. “We’re able to speak to eight transmitters at once, so we’re getting status and diagnostic information every second, rather than monthly or daily,”
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“We’re getting status and diagnostic information from eight transmitters every second, rather than monthly or daily.”
says Charles Piper, Foxboro’s fieldbus products manager. Yokogawa offers fully redundant HART interface modules for its CENTUM CS 3000 R3 distributed control
uration, just like everyone else, we have an explorer view of the whole system that typically shows the network, DeltaV controllers, workstations, and I/O cards,” says Ramachandran. “But
Leverage Your HART Instrumentation
Condition and diagnostic information from HART-capable field instruments can be captured from control networks by online applications and integrated with enterprise asset management systems.
system as part of the company’s Fieldnetwork I/O subsystem, notes Bruce Jensen, Yokogawa’s manager of systems marketing and sales support. “These modules can be installed in remotely mounted units within Class I, Div. 2 environments and include such options as ISA G3 corrosion resistance and a high temperature rating of -20-70° C,” he adds. In addition, Yokogawa’s Plant Resource Manager—its field asset management solution—automates data collection from HART devices. The software functions as a standalone application or through the CENTUM system, and allows integration, management, and maintenance of these field devices using a common database. Ram Ramachandran, director of systems marketing for Emerson Process Management, touts the tight integration of HART into his company’s DeltaV control system. “In instrument config-
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what we do, that I think is unique, is show the HART devices in this hierarchy. That does lots of things for you. You can go into your system, click on an I/O card and ask it to auto-sense all of the devices for you and populate the explorer with them.” Systems from companies such as Siemens, Honeywell, ABB, and others also offer their own sets of features that enhance HART’s capabilities. By using a control system with native HART support or third-party add-ons from companies such as MACTek, Moore Industries, MTL, and others, end users can put this data to work in their plants at minimal cost, since many, if not all, of their existing field devices are HART-compatible. In addition, HART operates over the same wiring as 4-20 mA signaling, and little additional training is needed to bring plant personnel up to speed.
Benefits Abound Here are some of the benefits that HART users can realize today: Reduce plant downtime, improve asset productivity: “What every customer wants out of a fieldbus like HART, first and foremost, is the ability to get faster notification of device problems, so he can avoid either a shutdown or off-quality production,” says Foxboro’s Piper. By integrating HART self-diagnostic information in control schemes or by polling instrumentation through a separate asset management system, users can spot potential problems before they happen. Harold Beck & Co., a Newtown, Pa., manufacturer of actuators used in industrial boilers and furnaces, began incorporating HART in its products about two years ago. Scott Kemp, Beck senior process control engineer, says the diagnostic capability embedded in a HART device is a major boon to users who want to improve management of their plant assets and ensure their maximum productivity. “The diagnostics in HART can tell you the reason the drive won’t move forward right now is because of this specific problem,” says Kemp. “Or it will tell you how many times a drive has been overtorqued or exceeded its temperature ratings. These all are features that weren’t available in standard analog electronics.” Gain additional value from existing instrumentation: Most of the smart instruments installed throughout the world are capable of measuring multiple variables. Using the HART protocol, manufacturers can acquire the additional digital information from their devices and incorporate it natively into their control schemes or route it to separate systems such as PC-based asset management systems, for monitoring equipment health in real time. For example, Detroit Water and Sewerage Dept. (DWSD)—this year’s winner of the HART Communication Foundation’s Plant of the Year award
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“Users want to validate that the instrument they believe is at the end of a pair of wires is exactly what they expect.”
—recently implemented a HART-based automated, system-wide metering and data monitoring application (see p23). Improve safety systems: HART serves as a valuable tool to ensure that process plants operate safely. DuPont’s DeLisle titanium dioxide production plant in Pass Christian, Miss. — HART Communication Foundation’s 2002 Plant of the Year — uses the protocol to provide key safety interlock inputs to its Honeywell TDC 3000 DCS and its hardwired safety shutdown relay system. The safety interlock system has a number of on/off control valves, each equipped with a HART-enabled valve-stem positioner. Each positioner communicates with the DCS via a 4-20 mA signal. Digital HART data is superimposed on the 4-20 mA connection and is extracted by a Moore Industries SPA HART loop monitor. The SPA then sends the actual valve-stem position data to the DCS via an additional
4-20 mA connection. By comparing the two 4-20 mA signals, the DCS ensures proper positioning of the valve stem. The HART data also allows DuPont to test the valve safety interlock operation from the control room by placing the appropriate DCS output in manual mode and adjusting the 4-20 mA signal to open and close the valve. The SPA returns a 4-20 mA signal derived from the device’s HART data to verify the valve position. Continuous validation of data and instrument accuracy: “Users want to validate that the instrument they believe is at the end of a pair of wires is exactly what they expect,” says Joe Serafin, Honeywell’s product manager for HART system integration. “That’s done through HART’s ability to access the device ID. In addition, users want to make sure the configuration on a device is correct, and they want to do that without having to walk out to the
HART Works With Other Protocols HART can easily operate in an environment that includes other fieldbus communications protocols such as Foundation fieldbus or Profibus. Products such as Smar’s HART-to-Foundation fieldbus gateway, in use at Cebrace’s Sao Paulo plant, are enabling companies to view and operate industrial networks as unified entities, even though they rely on multiple communication technologies. While HART can exist in harmony with newer digital fieldbus technologies, users should take a close look at HART’s functionality before investing in newer and potentially costly technologies. There’s no doubt that these newer, all-digital protocols can bring a wealth of benefits to users, but they come at a cost. For example, use of these protocols usually involves the purchase of new instruments, new wiring, elaborate network configuration, and extensive, potentially costly training for plant personnel. HART technology, which is mature and proven, offers many of the same advantages as the newer protocols with minimal additional investment. “I can bring the smart information in, and the same people who took care of that transmitter yesterday can take care of it today,” says Joe Serafin, Honeywell. “You can probably train someone to be an expert in HART in four hours. You can’t do that with other technologies. HART is very easy and simple, yet it gives you the core features of other digital protocols without a lot of the overhead.” So, the next time you hear the word “HART” don’t just associate it with maintenance personnel, trips to the field, and handheld communicators. Instead, think: “HART: Easy, proven, high value, low risk, outstanding results.”
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device with a handheld.” In addition to validating the presence of the expected instrument, HART enables users to spot deviations in range and loop current, and identify “in-band” errors that might not otherwise be apparent. For example, a Midwest refinery suffered a $300,000 disruption as the result of a short circuit causing an erroneous measurement signal to a critical level control loop. The problem went undetected, because the "in-band" error to the 4-20 mA signal made it seem as though the level control was functioning normally. Had the level transmitter and control system been HART-enabled, the mismatch between the 4-20 mA and digital signals from the level transmitter would have been detected in real time (seconds), allowing the disruptive shutdown to be avoided. More efficient use of operations and maintenance personnel: The use of HART-enabled control systems and devices enables plants to optimize the use of operational and maintenance personnel. First, training existing personnel on the use of HART is relatively quick and painless, and migration from an analog system to the analog-digital HART protocol is relatively simple. During commissioning, users can view and validate loop and field device configuration from their operator or engineering workstations. HART’s selfdiagnostic capabilities reduce the number of false alarms that otherwise would result in fruitless and sometimes hazardous trips to the instrument site. In addition, HART-enabled data on equipment health enables plants to perform more accurate maintenance and replacement, further eliminating trips to the field. Gilbert Hurtubise, consulting engineer on Syncrude’s expansion of its Fort McMurray, Alberta, crude oil production facility, estimates that use of HART has enabled the company to reduce systems commissioning labor by as much as 70%. ◊
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T HART Capabilities Provide Fundamental Value HART Fundamentals
HART Data—Overview
Field-proven, global industry standard
Digital data: 35-40 valuable data items standard in every HART device
Two communication channels simultaneous on the same wire
Device identification: device tag, supplier, device type and revision, device serial number
4-20 mA analog channel: for fastest possible data transfer of control signal Digital channel: for read/write access to all device data 35-40 data items standard in every HART device Advanced diagnostics and intelligent multivariable devices Many cost-effective solutions for integration with plant systems Unmatched range of products and worldwide support
Calibration data: upper and lower range values, upper and lower sensor limits, PV damping, last calibration date Process variables: primary variable plus secondary measurements and multivariable parameters Status/diagnostic alerts: device malfunction, configuration change, power fail restart, loop current fixed or saturated, primary or secondary variable out of limits, communication error, plus more
HART Benefits Highly accurate and robust communication unlocks value in smart devices Simple, cost-effective, high-value, low-risk, feature-rich: easy to use and maintain Lowers cost through faster commissioning and simplified maintenance Real-time diagnostics and predictive maintenance alerts enable problem detection in seconds Benefits multiply by real-time integration with plant control, safety, and asset management systems
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The HART of Asset Management Real-Time Connections Deliver Results Improve Plant Operations
Aid Compliance
Leverage intelligent device capabilities for operational improvement
Enable automated recordkeeping of compliance data
Real-time diagnostic alerts provide early warning of device or process problems Reduces time from problem identification to problem resolution Continuous validation of control information and loop integrity Increases asset productivity and system availability
Increase Plant Availability
Facilitates automated safety shutdown testing Advanced diagnostics increase safety integrity level (SIL) Intelligent multivariable devices aid reporting
Integration with systems enables detection of previously undetectable problems Device and/or process connection problems detected in real time Early warning enables proactive action to minimize impact Avoid high cost of unscheduled shutdowns or process disruptions
“HART does the job for us, and you don’t pay extra for it.” ••• Dennis Green, Head Engineer DWSD, Detroit
Lower Maintenance Costs Quickly verify and validate control loop and device configuration Remote diagnostics reduce unnecessary field checks Predictive diagnostics and advanced problem detection capabilities simplify maintenance Lower spares inventory and device management costs
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Time to Tap Into HART Seize the Data. There Are Major Asset Management and Process Improvement Gains to Be Realized With HART
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s manufacturers wrestle the challenges of a feeble economy, a slowdown in capital investment, and intense competition in a global economy, many are searching for ways to wring additional value from their existing assets. Yet in their quest, many of these same manufacturers are leaving a major source of improvements untapped. Most manufacturers access HARTenabled variables only when maintenance personnel go to the field to calibrate them. And that, say some experts, is like leaving money on the table at a card game. “When you spend money for an asset and then don’t do proper asset management or let that asset degrade, you’re just not getting the return you should,” says Jake Oddo, leader of a process control steering team for Dupont’s titanium dioxide business. “In DuPont’s Six Sigma quality initiative, we view an underutilized asset as a defect. With HART, you can avoid that situation, and you’ve already paid for that HART transmitter.”
Where to Begin? Even users who are aware of the untapped riches locked in HARTcapable instruments might be at a loss about where to begin taking advantage of this resource. Here are some steps to consider: Identify your HART instruments: The first step in many plants – particularly large operations that might have thousands of instruments – is to determine which installed instruments are HART-capable. In many cases, this is simply a matter of consulting the plant’s asset management system and/or instrument documentation. A general rule is that any smart instru-
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ment manufactured from the mid1990s onward almost certainly is HART-capable. Also, be sure all future instrumentation purchases include the capability to communicate via HART. More than 150 suppliers offer HART on more than 600 different devices covering a wide range of measurement and control functions. Identify benefit opportunities: Determine where you can gain the most benefit most quickly by tapping into
Top 10 HART Apps 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Configuration/commissioning Calibration/ranging Multivariable device data Real-time diagnostics Process/device alerts Control signal validation Safety integrity verification Remote SCADA applications OPC/Ethernet integration Asset management/optimization
the rich flow of data available from your HART devices. “Would you put in a massive program to acquire information from sump pumps?” says Oddo, whose DuPont facility in Pass Christian, Miss., was last year’s HART Communication Foundation Plant of the Year. “Probably not. But would you do it to gain more information on critical reactor temperatures? Yes, you probably would. In situations where you might have temperature upsets that could cause you to go critical, you could be risking explosions and fatalities, so when you start assessing those situations, using HART is pretty much a no-brainer.”
Modest Investments Required Most major control vendors have incorporated HART I/O into their systems, enabling users to integrate digital HART data directly into their control schemes and applications. Users of most legacy systems do not have this capability, but fortunately, a number of companies have developed innovative solutions to help users get the most value from their instrumentation. Gil Hurtubise, consulting engineer on Syncrude’s plant expansion project in Alberta, acknowledges users might have to purchase devices for HART connectivity and data extraction, special software such as Emerson Process Management’s Asset Management System, PCs to read the data, etc. But he adds, “All of that is offset by a big reduction in labor, because you don’t have so many people running around in the field, verifying calibration. In an application such as partial valve stroking, you can tell right from your laptop or desktop PC whether the valve is actually moving or not. You don’t have to have someone out in the field watching.” Among the additional investments plants might need to consider are: HART interfaces: An interface such as the HIM HART Loop Interface and Monitor from Moore Industries strips digital HART data from the instrument for use in the control system or in applications based on other platforms such as a PC. For example, smart HART multivariable mass flow transmitters sense three process variables (pressure, temperature, and differential pressure or raw flow). Using these data, they perform an internal calculation to derive mass flow, which is transmitted as a 4-20 mA signal to the control system. “Unfortunately, unless you have a
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“HART may not give you everything you want, but it could get you 85 to 90% of the way.”
HART-based control system, there is no way to continuously monitor the non-primary variables used to make the calculation,” says Steve Todd, Moore Industries’ marketing director. “By reading the HART digital data on the secondary variables and transmitting them as an analog signal, these variables can be obtained in an older control system.” HART multiplexers: HART multi-
plexers enable users to save on wiring to field instruments by serving as a field interface to multiple HART-enabled field devices. Typically, a PC acts as the host, providing the human-machine interface and performing other highlevel functions. The multiplexer continuously monitors the field devices, reports the current readings and instrument status to the host, and passes
About the HART Communication Foundation The HART Communication Foundation (HCF) is an independent, not-forprofit organization that provides worldwide support for the HART technology. Established in 1993, HCF is the technology owner and standards-setting body for the HART protocol. HCF manages the protocol standards, ensures that the technology is openly available, and educates users through training and support for application of the protocol. Memberships HCF memberships are open to any company interested in the use of HART technology—suppliers, systems integrators, end users, and others. HCF membership provides many benefits including the ability to vote on matters influencing future direction of the protocol, participation on HCF working groups/committees, access to HCF technology and tools for HART development, use of the HART logo, and participation in HCF-sponsored promotion activities. HART Training Workshops HCF workshops educate users on HART communication. Workshop sessions are scheduled quarterly in Austin, Texas, and Basel, Switzerland: • HART Applications: This special on-site workshop provides a basic overview of HART communication and the capabilities of HART-enabled devices. The benefits and options for real-time integration with plant automation/asset management systems also are discussed. • HART Protocol Fundamentals: The HART protocol is relatively easy to implement, but there is a learning curve. This intensive, three-day, developer-oriented workshop provides all the information and tools necessary to efficiently develop a HART-based field device or system interface. • Writing Device Descriptions (DDs): This four-day consultative training session covers all aspects of the Device Description Language (DDL) and how to use DDL to write the DD for a specific field device. Students leave the workshop with a working prototype DD for their HART device. HART Communication Foundation 9390 Research Blvd., Suite I-350, Austin, TX 78759 Telephone: 512/794-0369; Fax: 512/794-3904 Email: [email protected] Web: www.hartcomm.org
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HART commands from the host computer to the field devices. A multiplexer also can be an integral part of the control system as a third-party I/O. As an I/O system, the multiplexer can include intrinsically safe barriers and other filtering capabilities and provide services to the field device, such as galvanic isolation or power. For this type of installation, no additional terminations or space are required. HART PC modems: Users of desktop or laptop PCs can equip their computers with modems that enable two-way communications with HART instruments. Among the leading manufacturers of such devices is MACTek. The devices are available for serial and USB ports as well as for laptop computers’ PCMCIA card slots. “Our modems work with just about every HART communication software package that I know of,” says Tom Holmes, founder and president of MACTek. While a PC equipped with a HART modem can perform many of the same tasks as a handheld communicator— downloading configuration information to a field instrument, for example—PCs generally have far more memory than such communicators and are capable of more sophisticated tasks. Protocol converters—Converters can deliver HART data to control systems, asset management systems, and other platforms via other digital protocols. For example, Smar last year introduced a converter to deliver HART data via a Foundation fieldbus network. Moore Industries’ HART Interface Module, mentioned above, also has a HART-toModbus option that converts the digital signal from a smart HART instrument to a standard Modbus RTU protocol output. As DuPont’s Jake Oddo puts it: “Right now, your plant might be about 10% of the way towards where you want it. HART may not give you everything you want, but it could get you 85 to 90% of the way.” ◊
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HART Plant of the Year The Detroit Water and Sewerage Dept. (DWSD) Uses HART Technology to Eliminate Metering Disputes, Improve System Reliability, and Streamline Operations.
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he old adage “numbers don’t lie” may be true in some cases, but when buyers and sellers rely on different sets of figures, the situation is ripe for dispute. That’s the situation the Detroit Water and Sewerage Dept. (DWSD) decided to rectify in its dealings with suburban municipality customers across Southeast Michigan. Many customers had measuring devices operating in parallel with DWSD’s older equipment. Invariably, the two systems disagreed and the customer always argued for the lower-cost reading. DWSD was forever in battles to show the legitimacy of its meter readings. In response, DWSD developed and implemented an extraordinary Automatic Meter Reading/Supervisory Control and Data Acquisition (AMR/ SCADA) system that relies on the power of the HART communication protocol to deliver consistent, reliable data on system performance directly to customers as well as to the utility. Citing the utility’s innovative approach to real-time use of the HART protocol, its aggressive plans to expand its use of HART technology, and the results it is achieving, the HART Communication Foundation selected the Detroit Water and Sewerage Dept. as its HART Plant of the Year for 2003.
Water, Water Management Everywhere DWSD’s services extend far beyond Detroit’s city limits to an area of more than 1,000 square miles including approximately 40% of Michigan’s population. Water flow and pressure are controlled and measured through instruments housed in nearly 300 underground meter-
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ing pits throughout the system. Measurement devices include a variety of flow and pressure meters manufactured by Smar, Endress+Hauser, and ABB. Prior to implementation of the AMR/SCADA project, data was recorded via chart recorders and similar paper-producing methods. Because the meters inform the utility of how much water is being used and by which customers, DWSD’s director and its head water system engineer refer to the meters as the utility’s “cash register.” However, by the mid-1990s, many of the customers were using cash registers of their own, says Head Engineer Dennis Green. The parties disagreed over consumption data and that’s where problems arose. In response, the department approved development of the AMR/SCADA sys-
tem (Figure 1), which was successfully piloted from 1996 to 1997 and is being expanded as a $10 million piece of a major infrastructure upgrade project.
Watershed Objectives To create the system it needed, DWSD and its consultants set five goals: • System dependability: Failure of any single component could not disrupt system performance, the flow of data, or the calibration work of the meter technicians. • Preservation of metering data: There can be no discrepancies between data anywhere in the system, and there must be opportunities to recover data when failures occurred. • Standardization of equipment and control of versions of software. • Minimal reliance on paper documents. • Incorporation of software aids into
Figure 1: Extraordinary Meter Reading
DWSD’s Water Board Building
DWSD’s Central Services Facility
RADIO
PC on LAN/WAN
Oracle database
Mobile headend for meter calibration crew
RADIO
SCADA Master
SCADA Master
Oracle database
PC on LAN/WAN
Office of customer’s water department typical of 85 sites
Metering site typical of 276 sites Above-ground control cabinet RADIO
RADIO Oracle database
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RADIO PLC/ RTU DP
Community SCADA Master PC Oracle database
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Pumping stations & water treatment plants typical of 27 sites Underground meter vault
RADIO
Distributed controller of DCS
The new SCADA and automatic meter reading system is being expanded as a $10 million segment of a major infrastructure improvement program.
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“HART is a stable protocol posing a low compatibility risk for planned expansions.” The Power of HART Through the use of HART, the Detroit Water and Sewerage Dept. integrated a vast array of diverse field devices and technologies on a single networked system that takes full advantage of HART’s digital communication capabilities. The result is a common odometer total display throughout the system that can be read via the LCDs on the HART meters just like the odometers of the mechanical meters while the PLC/RTU collects total and instantaneous rate of flow readings to control switching between the large and small venturi meters using standard and extended HART commands. In addition to stemming billing disputes with its customers, the AMR/SCADA system is delivering the following benefits to the utility and its customer communities: • Increased ability to quickly detect and repair troubles in the distribution system. • Improved safety through HART-enabled remote monitoring, calibration, and validation. Performing these tasks remotely enabled DWSD to reduce field crews’ need to enter potentially hazardous meter pits. • Greatly enhanced value from existing instrumentation without having to rely on communications technologies that are not as well field-proven as HART and that require steep investment and risk. • Greater accuracy in readings throughout the water-distribution system, largely due to HART’s ability to preserve the full accuracy of the measuring element in a digital format. • Range switching and totalization with a single instrument through HART’s digital transmission of multiple variables. • The ability to drive computational functions to the field device (e.g., totalization), which frees the higher-level PLC/RTU for tasks such as monitoring equipment health. • Fault tolerance through the ability of HART instruments to retain a history of their readings. In addition, the system’s packet radio network reroutes signals in case of a node failure. • Creation of a computer-based historian, which facilitates analysis and reduces paper records.
the SCADA system for maintenance, calibration, performance monitoring, and other functions. At the core of the new system are the existing flow and pressure transmitters and flowmeters. Among the issues DWSD faced were identification and adoption of a digital means of measuring and transmitting data that would work with the variety of measurement technologies already in use (e.g., mechanical meters, venturis, orifice systems, magnetic flowmeters, etc.).
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The Answer Is HART DWSD determined that HART provided the best solution for several reasons. First, HART minimized the additional investment DWSD had to make, since most of the existing instrumentation was HART-capable and could use existing wiring. In addition, HART is a stable protocol posing a low compatibility risk for planned expansions. Furthermore, HART enabled DWSD to digitally extract secondary variables and diagnostic information, and the intelli-
gence built into HART instruments enabled them to perform calculations, freeing computing power in higherlevel platforms for other tasks. For example, the differential pressure cells used in the system are capable of self-monitoring and on-board totalization, says Dan Lacy, sales executive for Greenwood, Ind.-based Endress+ Hauser. E+H transmitters are used throughout the water system to report pressures in DWSD’s mains and the pressures delivered to customers, which can confirm proper operation of the community’s pressure-reducing valves and avoid telephone calls to DWSD’s Systems Control Center. In addition to approximately 750 instruments in nearly 300 metering pits throughout DWSD’s service area, the system consists of a PLC/RTU located at each meter pit. Each PLC/ RTU is connected to the pit’s instrumentation and is equipped with radio telemetry and a battery backup. The two DWSD SCADA head-ends feature dual historians, each capable of maintaining up to 10 years of data for recovery and analysis. Other components of the system include 35 laptop computers that serve as mobile SCADA masters for field calibration and are used to set and download instrument parameters. DWSD also supplied its customers with approximately 90 PCs that serve as SCADA monitoring stations, thus giving customers access to the same data that DWSD is receiving. All laptop and desktop PCs run iFIX software and Oracle relational database management software and can operate independently of the DWSD SCADA headends. “Every PLC/RTU runs the identical copy of software developed for DWSD by Control Microsystems and EDS,” says Cliff Montgomery of Rhythm Technologies, a Michigan consulting firm that helped design and implement the network. “We download parameters from a laptop PC running GE Fanuc iFIX
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“I know these newer fieldbus technologies are the hot thing right now, but it could have cost us twice as much money.”
software to configure the PLC/RTU for monitoring and operating a particular meter, and we upload those operating parameters each day and store them in the historian, along with the HART device serial numbers and communication statistics. That way, we know the configuration of the system each day and when it changes.” The AMR/SCADA system is designed to accept readings from up to four flowmeters and four pressure devices at each metering point, each of which is capable of measuring and digitally transmitting multiple variables. In keeping with the goal of fault-tolerance, the devices, although connected in a common loop, are wired to the PLC/RTUs in a star topology, so if a single device or instrument cable fails, it can be taken out of the loop at the aboveground PLC/RTU. The fault-tolerant philosophy extends to the PLC/RTUs and the packet radio network as well. “The system operates like the Internet,” says Green. “The messages going back and forth are like email. Each radio acts as a repeater for its neighbors and automatically reroutes messages around a radio that fails or that is suffering interference.” The customers feel better about all this. “The municipalities that purchase water from DWSD receive the data from their meters directly rather than from the DWSD head end,” adds Montgomery. “This assures customers that DWSD is not adjusting or manipulating the data.” Cesar Cassiolato, manager of pressure transmitters for Smar, notes that his company’s differential pressure transmitters (Figure 2) are designed to retain totalization, even in the event of a power loss. “There’s no reset upon loss of power. When the power returns, you can continue to totalize correctly,” he says. That meant DWSD could rely on HART. “So we decided to have the HART instrument perform the integration of rate to volume, rather than the
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PLC/RTU calculating a volume by scanning instantaneous flow rate values from the HART loop,” says Green. “In addition, the HART instrument/meter integrates far more frequent readings than
Figure 2: Took a Load Off
HART-enabled devices allow DWSD to distribute total flow computation responsibilities to the processors of the differential pressure transmitters and the magnetic flowmeters in the vaults, reducing the load on the PLC/RTUs.
the PLC/RTU, so the values are much more accurate. This freed up the PLC/RTU to do all the instrument health monitoring and store 31 days of 5-min. meter readings.” As part of that monitoring, HART allows the PLC/RTUs to detect the types and brands of instruments on the network and collect their serial numbers each day for a permanent record of equipment that can be used in billing disputes and to quickly identify faulty equipment.
So Far, So Good Overall, the utility is happy with the new system, but it hasn’t attempted to
quantify the payback on the project. “The continuing controversies over the accuracy of our meters can be bottomless pits in terms of time and money,” says Green. “With the new system, DWSD is seeking an end to those disputes. Estimated bills that err in favor of the protesting customer have been reduced substantially.” Other networking technologies such as Foundation fieldbus and Profibus have matured considerably since 1996, when DWSD began piloting its system. Nevertheless, Green says that he would still use HART, even if the project were beginning today. “I know these newer fieldbus technologies are the hot thing right now, but it could have cost us twice as much money,” he says. “HART does the job for us, and it’s done on our standard equipment that was already installed – you don’t pay extra for it. It certainly was ideal for what we wanted to do.” Looking ahead, Green noted that DWSD is building a SCADA system for controlling its treated water transmission system and wastewater collection system, which includes new sewer meters. “Once our customers are satisfied with the water meters of the distribution system, we want to integrate our 54 sewer meters into the SCADA system. Much of the equipment on the process control SCADA system also is HART-capable, so we definitely want to bring them in,” says Green. For more information on this application, go to www.hartcomm.org. ◊
How DWSD Won The HART Plant of the Year Award is an annual award presented to companies that use the real-time communication power of their HART devices. The HART Communication Foundation asked its members and CONTROL magazine readers to nominate plants that are using the power of HART technology. A panel of HART Communication Foundation officials and CONTROL editors reviewed the submissions, interviewed the finalists, and selected the 2003 HART Plant of the Year.
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Leverage Your Assets HART Communication: It's Not Just for Configuration Anymore
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ant to run your plant more efficiently? Would you like to set up a better, more automated maintenance management program? Are you trying to obtain asset management information from your plant instrumentation? Maybe you’d like to avoid process disruptions. Or keep your plant from catching fire and blowing up. A level transmitter at a Midwest refinery was short-circuited by condensation and created an erroneous 4-20 mA signal. The operator was suspicious, but no one could find a problem until the tank overfilled and shut the entire plant down. The process disruption cost $300,000. If the system and level transmitter had been HART-enabled, the erroneous signal could have been detected and the operator would have been alerted to the problem before it shut down the plant. You can create those kinds of capabilities in your plant. You may already have much of what you need to get started, particularly if you purchased new smart field instrumentation in the past 10 years. That’s because just about every smart field instrument built these days is capable of HART Communication. And if you have devices with HART Communication, you also have a good start on what you need to run your plant more efficiently. You’re ready to begin an asset management program, obtain early alarms on process upsets, and increase the reliability of your processes. What’s more, it won’t be a major investment to obtain the information you need, because it’s already there, ready to be accessed via HART Communication.
More Than Maintenance Maintenance technicians appreciate HART because it makes their jobs easier. Techs can interrogate devices directly from the control room, eliminating many unnecessary trips out into the plant.
The Gainesville Regional Utility, Gainesville, Fla., uses HART Communication to diagnose instrumentation problems and reduce unnecessary trips to the field. The data is fed to asset management system software from Emerson Process Management.
Figure 1: Powerful Intelligence
HART diagnostics mean technicians at the John R. Kelley Generating Station, Gainesville, Fla., make far fewer futile trips up the seven-story heat recovery generator to check out questionable field devices.
What you may not realize is that simplifying maintenance and calibration tasks is just the tip of the iceberg. Your HART devices also have the power to push your existing plant instrumentation and control systems into the 21st Century. You can use HART technology to get started in asset management, for example. HART devices have all the information you need to determine device status, health, and the need for field maintenance. HART devices can also determine the health of other process equipment, such as control and safety shutdown valves.
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Operators at its John R. Kelley Generating Station (Figure 1) can check many process problems by examining asset management data from a PC. For example, if an operator suspects a transmitter is not zeroing out, he can check the asset management system historical data. If there’s a difference of 5% or more between the process signal and the HART data, the operator knows a problem exists, and someone must physically check the transmitter and associated equipment. More often than not, the utility will report the problem is a leaking valve, found long before the consequences become
“After nearly a year of working with HART, our reliance on the asset management software continues to grow.” serious and cause a system breakdown. “After nearly a year of working with the HART-capable instrumentation installed as part of a re-powered 110 MW combined-cycle generating plant, our reliance on the unit’s asset management software package continues to grow,” says Terry Gordon, instrumentation supervisor. “It enables us to do a lot more things a lot quicker, with fewer personnel than we could by following conventional instrument maintenance procedures.” One of the finalists for this year’s HART Plant of the Year Award, a Solutia plant in Chocolate Bayou, Texas, that started up in 2000, has lots of HART-enabled instrumentation. All the HART data is logged to an AspenTech data historian and to an asset management system. “Our design decision was to use as much smart instrumentation as possible,” says John Forbis, Engineering Fellow at Solutia’s Integrated Nylon Div., St. Louis. “Ninety-nine percent of all instruments are HART-enabled. The only non-HART instruments are on OEM systems, such as chillers and air compressors. We tried another communication technology, and it just did not work for us.” A British Petroleum ethylene plant in Cologne, Germany, has about 2,000 HART-enabled instruments and about 800 HART-enabled control valves integrated with its DCS. “We plan to use condition-based preventive maintenance implemented via the Foxboro DCS and HART to reduce downtime,” says Helmut Schult, DCS site manager. “Specifically, we are configuring the system to automatically send e-mails describing impending problems to our maintenance department.” HART Communication is being used by many companies to acquire data for SCADA systems and DCSs. Although the traditional 4-20 mA output from each HART transmitter con-
tains the basic flow, temperature, level, or pressure signal, the digital HART data superimposed upon the 420 mA signal contains much more information. Depending on the device, the digital signal can contain 40 or more data items. After a HART-enabled device is commissioned and installed in a plant, it provides those data items 24 hours a day, continuously. All you have to do is communicate with the device.
The HART of the Matter What can you do with all that data? Here are a few ideas: • Asset management: HART instruments contain data on the health and status of field assets, plus additional process variables. Software is available from several vendors to acquire data directly from the HART field devices to track calibration and configuration changes, and keep records on instrument changes for compliance purposes. Asset management systems can use the additional process variables to directly read flow,
Top 10 HART Apps 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Configuration Commissioning Calibration Diagnostics Multivariable process data Process/device alarms Signal verification Redundant signals Data for SCADA applications OPC-compliant data
level, pressure, and temperature data to be used for compensation, environmental check, or other purposes. • Acquire process data: HART allows control and other systems to obtain digital process data directly from field devices. For example, the Solutia plant at Chocolate Bayou uses HART technology to acquire analog
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inputs for a Triconex triple-modular redundant system used for safety and emergency shutdowns. “When the same signal needs to go to our control system and the Triconex safety system, we use a signal splitter/isolator from Moore Industries,” says Bart Propst, process control engineer. “The Moore device receives a 4-20 mA signal from a HART instrument and sends 4-20 mA outputs to the control system and another 4-20 mA signal created from the HART data to the safety system.” This lets them use the same 4-20 mA sensor for control, safety, and shutdown, and still maintain signal isolation. • Improve product quality: HART data can be used to improve process dynamics and product quality. The Solutia plant in Chocolate Bayou acquires process data from multivariable HART transmitters. Forbis says they use Valvelink software to do advanced testing and trim key valves to improve process performance. • Manage maintenance: At the Air Products and Chemicals plant in Baytown, Texas, the asset management system keeps track of 1,000 transmitters and 150 valves using HART data. “Plant personnel use asset management for routine troubleshooting of process issues, recalibration, and verifying valve operation relative to the original valve signatures,” says Mark Lusignia, instrument engineer. • Real-time diagnostics: When problems arise with a field instrument, the array of diagnostic information available in HART devices makes it possible to diagnose many problems from a PC screen. In some plants, half of the times an instrument tech is asked to go out into the plant to check an instrument, the result is “no problem found.” Being able to diagnose
“HART data showed that the calibration cycle could be at least doubled to every six months.” instrument problems remotely saves time and improves worker safety. For example, the Gainesville Regional Utility uses HART communication to verify the condition and operational status of instruments on top of a seven-story heat-recovery generator and other inaccessible points. “It would take a technician up to an hour to go out into the plant and check a single instrument,” says Gordon. • Diagnostic alarms: When a control system depends on a 4-20 mA signal alone, an operator has no way to check the accuracy or validity of data when a problem is suspected. With HART-enabled systems, software can be set up to automatically look for a device status problem or a performance problem and sound alarms long before a problem can be detected in the 4-20 mA loop current. • Minimize scheduled downtime: GSK Pharmaceuticals in Irvine, Scotland, also a HART Plant of the Year finalist, wanted to reduce the frequency of
calibration for 122 critical devices from once every three months to something less often. It takes four hours to calibrate each device, and four times per year seemed to be too frequent, but they had no way of knowing how often calibrations were really necessary. The plant used HART data to collect device information and run online diagnostics. “After a yearand-a-half evaluation period, HART data showed that the calibration cycle could be at least doubled to every six months,” says Ian Allen, instrument engineer. “We also got more accurate information as to when a device actually did fail, as opposed to waiting for the next calibration, so it could be repaired or replaced immediately.”
Where Do You Go From Here? For companies building new greenfield plants, the choice might be simple: buy only HART-enabled field instruments and system components
Finding Problems HART communication enables intelligent I/O systems to identify and diagnose process problems such as: • Loop fault: With a standard 4-20 mA signal, I/O systems can detect a problem only if the signal is outside the 4-20 mA range, and only if it is constant; they can easily miss intermittent problems. A HART system can periodically check the 4-20 mA signal to ensure its agreement with the field I/O device. It detects intermittent problems and performs loop tests whenever needed. • Device failure: With ordinary transmitters, I/O can detect catastrophic device failure only if the 4-20 mA signal is outside the normal operating range. With HART, internal diagnostics can communicate the status of field devices in real time, provide early notification of problems, and help you take action to prevent a process disruption. • Incorrect reading: When the accuracy of the 4-20 mA signal is impaired by, for example, a bad connection or deteriorating sensor, the host system can detect the incongruities between the 4-20 mA signal and the additional process variables communicated by the HART protocol. Early detection and analysis of these incongruities can focus maintenance operations and prevent shutdowns.
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and enjoy the benefits of HART Communication from the beginning. HART will simplify installation, startup, calibration, and maintenance, and provide a cost-effective low-risk foundation for an intelligent instrument network for the entire plant. For companies that already have existing plants with legacy instrumentation, the upgrade path is different. First, take an inventory of all the HART-enabled instrumentation in your plant. You probably will be surprised to find out how many installed HART instruments you have. Second, map out an upgrade strategy. Non-smart field instruments have to be upgraded and replaced periodically, so make sure that new instruments are HART-enabled. Such an upgrade path is quite easy, because nearly every legacy 4-20 mA instrument can be directly replaced with a HART device. What’s more, the replacement device will require no change to your existing control system, because the HART device’s 4-20 mA output connects to the same terminals as the legacy device. When you map out the upgrade strategy, you may find that a particular process unit needs only one or two instruments to become an all-HART system. In such a case, you may want to speed up the upgrade on that unit or swap some HART instrumentation into the system from elsewhere in the plant. Third, review the migration strategies we show on pages S-12 and S-13, and see how your plant might take advantage of its HART instruments. Then obtain a HART server, HART-capable multiplexers, HARTenabled I/O, or a similar HARTbased system from your instrument supplier and begin implementing an asset management, automated maintenance, device diagnostics, or device status alarm application.
Unleash the P Critical Facts About HART • Traditional 4-20 mA analog signal is used for control and/or monitoring. • Digital signal carries additional information on the same wiring. • All HART smart devices continuously provide process data for plant operation—24/7. • HART provides access to all device data while the 4-20 mA analog signal is being used for control. • Information about the status (health) of the field device and quality of the 4-20 mA signal is in every message. • The Process or Primary Variable (PV) is transmitted as a 4-20 mA signal and also as a digital value. • Many devices have measured or calculated process variables in addition to the PV. • The more you communicate with HART devices, the more value you receive from your investment.
HART Device Data Every HART device, regardless of the supplier, comes standard with the ability to communicate 35-40 data items you can use to improve your operations. These data items include: • Process Variable Values Primary, secondary, and other values Loop current value in milliamps • Device Status & Diagnostic Alerts Device malfunction Configuration change Variable out of limits Primary variable output fixed or saturated • Device Identification Instrument tag, device type, etc. • Calibration Information Date of last calibration Upper & lower range value PV damping Loop current transfer function & alarm action Write protect status
Point-to-Point Strategy • Part-time connection • Single device
Migration Strategies for HA HART• Rem • Cen • Off
Analog DCS/PLC
Asset m
HART for device configuration
HART-to-Analog Strategy • Real-time process variable data • Device diagnostics conversion
To analog control system Signal extracter
Existing system I/0
Analog + HART
HART process data converted to 4-20 mA
HART value
A Choice of Migration Strategies There are many ways to benefit from the power of HART communication and leverage the intelligence in your smart field devices. The figures show several simple and cost-effective migration strategies to get more from currently installed HART equipment • Point-to-Point Strategy: This is the most common way HART is used. The communication capability of HART-enabled devices allows them to be configured and set-up for specific applications, reducing spares inventory and saving time and money
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More HART value
in commissioning and maintenance. Connecting to the 4-20 mA wires, you can interrogate a device from remote locations for diagnostic information. • HART-to-Analog Strategy: Signal extractors communicate with HART devices in real time to convert the intelligent information in these devices into 4-20 mA signals for input into an existing analog control system. Add this capability one device at a time to get more of the power of HART. • HART-Plus-Analog Strategy: New HART multiplexer packaging solu-
ower of HART Serve HART to Plant Networks HART-enabled DCS/PLC/PAS Full HART Implementation Strategy • Real-time and integrated data • HART data part of DCS • Full HART data access
RT Integration
a
-Plus-Analog Strategy ote device access tralized device diagnostics f-line data access
HAR T
dat
HART-enabled I/0
anagement system
HART data
I/O with mux
HART-to-Plant-Network Strategy • HART data to LAN • OPC-compliant • Enterprise-wide access SCADA
HART
Historical trending
OPC SPC/SQC
Ethernet MIS/ERP OPC clients
Ethernet-TCP/IP
data HART
HART OPC server
RS-232 interface
I/O with mux HART-enabled I/O
Maximum HART value
tions make it easy to communicate with HART devices by replacing your existing I/O termination panels. Your analog control signal continues on to the control system but the HART data is sent to a device management system providing valuable diagnostics information 24/7. Although the control system is not aware of the HART data, this solution provides access to device diagnostics for asset management and process improvements. • Full HART Integration Strategy: Upgrading your field or remote I/O system provides an integrated path to
continuously put HART data directly into your control system. Continuous communication between the field device and control system allows automatic detection of problems so corrective action can be taken before there is negative impact to the process operation. • HART-to-Plant-Network Strategy: HART OPC server software tools provide a simple, cost-effective means of passing HART data onto your plant Ethernet network to OPCcompliant applications anywhere in the plant.
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The HART Communication Foundation has developed the HART Server Tool to facilitate serving HART data to plant networks and other high-level OPC-compliant applications. The tool provides easy access to HART device data anywhere on a plant network. • Allows several applications to simultaneously access data in a HART device. • Enables popular HMI and trending packages to access HART data. • Connect to one or a thousand devices using common HART I/O systems and interfaces. • Cost-effective and easy to set-up and use. • Can put HART data on your desk top, PDA, e-mail system, etc. • Created and supported by the HART Communication Foundation.
What to Do? HART communication technology is simple, easy to use, low-risk, and costeffective. As with any journey, taking the first step is important. Here’s how to get started: • Visualize one or more of the many ways HART communications could improve operations in your plant. • Identify your installed HART devices to confirm that key measurements are included. If not, map out a plan to make all devices HART-capable. • Provide HART technology training to your staff. • Explore HART solutions with your suppliers to determine your best migration strategy. • Contact the HART Communication Foundation or visit the Foundation web site, www.hartcomm.org, for more information and for specific cost-effective solutions you can use to Unleash the Power of HART.
Powerful Connections New Products Seamlessly Connect HART Field Devices to Any Control System
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n essence, HART’s value proposition is moving more data from the process into the control system with an infrastructure you already own, then leveraging that information to increase plant efficiency. A range of connection options make it relatively easy. If your plant has a DCS connected to a large number of HART-enabled instruments and field devices, the HART signal superimposed on the 4-20 mA wiring is readily available and contains a wealth of useful process and device diagnostics information.
Control Systems Get HART Most of the major DCS and control system vendors already have HART Communication capability in their newer systems, and many have upgrade paths for older systems. For example, in May the Foxboro division of Invensys announced new I/A Series HART modules. Each module can accept up to eight 4-20 mA inputs and fully integrates HART Communication. The Foxboro upgrade has already been used to implement asset management and preventive maintenance at a British Petroleum ethylene plant in Cologne, Germany. The plant has about 2,000 HART-enabled instruments and about 800 HART-enabled control valves. “We purchased new input and output modules and installed the newest version of the Foxboro I/A software,” says Helmut Schult, BP’s DCS site manager at the Cologne plant. “We then installed the modules, and configured the I/A system to recognize the modules.” There was no need to change field devices since they were already HART-capable. This kind of system offers full-time, real-time HART data integration with
the control system and higher-level systems. While the several-second latencies of other approaches are usually quite acceptable in process applications, control systems optimized for HART Communication can reduce latency times to about 0.4 sec. per point, depending on the network configuration. Honeywell’s Experion PKS control system offers eight-channel HART analog-input and analog-output modules. Both modules scan the standard 4-20 mA analog signal and the HART digital signal. The HART digital data is made available to the control system over ControlNet. “HART device information is scanned from each device and made available for display, logic, control, or trending,” says Joe Serafin, Experion
“HART instruments are connected to the Industrial IT I/O system,” explains Martina Walzer, marketing manager of fieldbus technologies for ABB. “HART information is then tunneled to the controller via Profibus.” HART Communications is also available on ABB’s legacy control systems including Advant, Symphony, and Freelance 2000. HART devices can communicate with Siemens’ systems through its compatible remote I/O, HART modem, HART interface, or HART multiplexer products, and a HART I/O module is offered as part of the APACS+ control system. Emerson Process Management delivers its DeltaV automation systems with HART as a standard. “We feel so
Figure 1: Multiplexers Link HART to Any PC
DIN rail-mounted multiplexers can be interconnected to provide communication with as many as 7,905 HART devices.
PKS product manager for Honeywell Industry Solutions. ABB supports the HART protocol through its Industrial IT controllers.
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strongly that HART is a good protocol for those not considering Foundation fieldbus that the DeltaV automation system analog I/O is only sold with
“Signal extractors can access portions of HART data from a device and send it to your plant control systems.” HART capability,” says Ron Eddie, vice president of technology for FisherRosemount Systems. HART functionality is also available on Westinghouse Ovation systems and on Provox and RS3 systems. On older generations of Provox it is only necessary to upgrade the I/O terminal strip and the analog I/O card. For the older generations of RS3 systems, it is necessary only to upgrade the I/O electronics.
Clever Devices Fill Gaps If your existing DCS is not HARTenabled, and if immediate plans do not call for a new DCS or an upgrade to your DCS to make it HART-capable, there are many other options. Signal extractors can access portions of HART data from a device and send it to your plant control system via 4-20 mA signals and/or discrete outputs. The 2002 HART Plant of the Year (page S-21) makes extensive use of
process variable values, the status and diagnostic alerts, and the device identification information contained in the HART data. Many control systems already have the capability to communicate via a digital fieldbus or an OPC interface. A low-cost way to connect HART instruments and control valves to these control systems is through a communications gateway. Multiplexers, RS232 interfaces, and gateways that connect HART to Ethernet, Modbus, and Profibus are widely available. The Viator HART PC modem from MACTek, for example, attaches to a PC serial port and allows the PC to communicate with HART devices. The modem is a good interface for Siemens’ Simatic PDM and other asset management software. Pepperl+Fuchs has a choice of HART multiplexers that convert HART data to RS-485. This serial data
Figure 2: At Your Service SCADA
Historical trending
SPC/SQC
MIS/ERP OPC clients
Ethernet-TCP/IP HART
HART OPC server
data
RS-232 interface
I/O with mux HART-enabled I/O
The HART OPC server provides a standard interface between HART devices and any OPC client.
Moore Industries’ SPA loop monitor and alarm. Signal extractors like the SPA extract the HART data superimposed on a 4-20 mA signal and retransmit virtually any combination of the
can be recognized by a number of PCbased software programs including AMS from Emerson, Cornerstone from Applied Systems Technologies, and Pepperl+Fuchs’ PACTware. A typical
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connection scheme combining master and slave multiplexers (Figure 1) can connect as many as 7,905 HART field devices to a PC.
OPC Serves It Up A more versatile and powerful method of connecting HART instruments and control valves to existing control systems is through the OPC-compatible HART Server Tool (Figure 2). Inexpensive and simple to implement, all that is required is a PC, OPC server software from the HART Communication Foundation, and a multiplexer or serial modem. The PC can be anything that runs Windows 95/98/NT/2000, from a fullblown desktop machine to a rackmounted device. The PC does not require a keyboard or a display to run the HART Server Tool software program, so it can be very compact, industrially hardened, and designed for low power consumption. The HART Server Tool software communicates with the HART devices, and converts HART data to OPC data. This OPC data can then be communicated to any software package with OPC client communications. Virtually all HMI, asset management, and soft logic software has a built-in OPC client interface, so the HART Server Tool can be used to connect just about any application to HART field devices. The HART server also allows several systems to access data from a HART device at the same time, and it can even be used to transmit data to handheld wireless devices such as PDAs. Whether starting small by extracting HART data on a limited basis for a specific purpose or diving in with a fully HART-capable DCS, using the information you already have available from your installed base of HART field devices is a powerful, cost-effective way to leverage your plant’s assets into the 21st Century.
HART Plant of the Year DuPont Uses HART Data to Satisfy Safety Interlock System Valve Test Requirements
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or its recognized success with HART-enabled instrumentation, as well as its commitment to future system enhancements using HART technology, the DuPont chloride-processing facility in DeLisle, Miss., has been selected the 2002 HART Plant of the Year. The HART Communication Foundation asked CONTROL readers and its members to tell us about plants that are leading the way in using the power of HART technology. Many worthy nominations were received. A panel of Foundation officials and CONTROL editors reviewed the submissions, interviewed the candidates, and selected the HART Plant of the Year. Three main factors led the judges to select this DuPont application as this year’s winner. First, the plant uses the power of HART even though it does not have a HART-enabled control system. Second, HART Communication is used full-time in daily operations. Finally, the plant is migrating to using HART information for additional cost-effective solutions that deliver significant benefits to the enterprise today and into the future. The DeLisle plant produces DuPont’s proprietary R-104 Ti-Pure titanium dioxide (TiO2). TiO2 is a white pigment used in paint, plastics, and products where color retention is desired. TiO2 absorbs ultra-violet light energy and it also possesses light-scattering properties that enhance whiteness, brightness, and opacity. TiO2 production requires a sophisticated manufacturing process that includes chemical reduction, purification, precipitation, washing, and calcination of titanium, iron, and other metal sulfates. “DuPont determined that the best way to control and monitor these
Fail-Safe System Relies on HART Communication Most safety interlocking at the DeLisle plant is implemented through a dedicated DCS controller, but certain processes must be equipped with a hardwired relay safety shutdown system. Many of these processes use HARTenabled pressure and temperature transmitters. Each of these transmitters sends a 4-20 mA process variable signal to a Moore Industries SPA loop monitor that decodes the HART data superimposed on the 4-20 mA signal. The SPA then sends a process variable signal derived from the HART data to the DCS, and it also sends fail-safe alarm contacts to the hard-wired relay safety shutdown system. These alarm contacts are set to indicate high-level, low-level, and the presence or absence of the HART signal. HART-enabled instruments allow DuPont to operate the plant in a safe and efficient manner. “HART and the SPAs provide a solution that unlocks a wealth of diagnostic and process information in the positioners and transmitters,”says DuPont project manager Joe Moffet. “This information is used to increase reliability and minimize the duration of required plant shutdowns.”
DuPont is using this highly efficient TiO2 processing site as a benchmark for other facilities because of its outstanding compliance with safety, health, and environmental requirements. DuPont plans to fully exploit the available HART data with an asset management system that will provide automated partial valve-stroke testing, predictive maintenance alerts, and comprehensive management of the plant instrumentation system.
processes was with HART-enabled instrumentation,” says Joe Moffet, project manager with DuPont. “Virtually all of the plant instrumentation is HARTenabled, and this includes instruments used to monitor and control temperature, pressure, level, and flow.” The DeLisle plant control and instrumentation system uses the HART communications protocol in a variety of ways. HART data is used as an input to
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the safety interlock system and as an input to the control system. Like most other users, DeLisle personnel use handheld HART communicators for configuration, calibration, and troubleshooting. And as we’ll see, future plans call for HART data as a key input to an asset management system. Normal plant operations are controlled by a Honeywell TDC-3000 distributed control system (DCS), and
“Virtually all of the plant instrumentation is HART-enabled...temperature, pressure, level, and flow.” the DCS is also used with a hard-wired relay system to control safety shutdown systems. Although future generations of Honeywell DCSs will be able to directly receive and transmit HART data, the present DCS does not have HART communications capability. DuPont needed to add intermediate instrumentation to extract relevant data
connected to the DCS via a 4-20 mA signal sent from the DCS to control the valve position. HART data is superimposed on the 4-20 mA connection, and the SPA loop monitor and alarm extracts the valve-stem position from the HART data. The SPA then sends the actual valve-stem position data to the DCS via an additional 4-20 mA connection.
Major Benefits of HART Communication for DuPont 1. Expedites testing of safety interlock valves, shortening plant shutdowns. 2. Provides fail-safe inputs to the hard-wired relay safety interlock system. 3. Allows remote configuration and ranging of virtually all instrumentation. 4. Reduces the number and duration of shutdowns by using partial valve-stroke testing. 5. Establishes the foundation for an asset management system.
from the plant’s HART instruments, and Moore Industries’ SPA HART loop monitor and alarm is used for this purpose. One of the main reasons DuPont selected the SPA instrument is that Moore Industries submitted the SPA to an independent third party for failure modes, effects, and diagnostic analysis (FMEDA). “FMEDA is a detailed circuit and performance evaluation that estimates the failure rates, failure modes, and diagnostic capabilities of a device,” explains Bud Adler, director of business development with Moore Industries. “Using the reliability data from the SPA’s FMEDA report, DuPont is able to verify that required safety integrity levels (SILs) are attained.”
HART Increases Uptime TiO2 production involves many critical and potentially hazardous processes, so reliable operation of the safety shutdown systems is of paramount concern. DuPont uses HART to provide key safety interlock inputs to the DCS and to the hard-wired relay system. The safety interlock system has a number of on/off control valves, each equipped with a HART-enabled valvestem positioner. Each control valve is
The DCS compares the valve control output signal to the HART valve-stem position data to ensure proper positioning. This data is used to verify correct functioning of the valve in normal operations, and to test the valve when DuPont performs periodically required plant shutdowns to verify operation of the safety shutdown system. The HART data allows DuPont to test valve safety interlock operation from the control room. Control room operators place the appropriate DCS output in manual mode and adjust the 4-20 mA control valve output signal to open and close the valve. The SPA sends a 4-20 mA signal derived from the HART data back to the DCS to verify valve position. Consider the alternative: If the valvestem position data was not available at the DCS through HART and the SPA, DuPont would have to station an instrument technician at each valve to observe valve operation. The technician would have to observe valve travel, and communicate this information to control room personnel. “There are over 100 control valves equipped with Moore SPA loop monitors, so valve safety interlock testing would be a labor-intensive and cumbersome oper-
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ation without HART Communication,” observes Moffet.
Online Tests Reduce Outages DuPont has plans to take valve testing to another level—a level that will reduce the number and lengths of outages required for safety interlock testing. Certain valve testing requirements for safety interlock systems can be met with partial valve-stroke testing of emergency shutdown valves during normal operations. Performing those tests during normal operations means fewer shutdowns are required, and the required tests take less time so the shutdowns can be shorter. Partial valve-stroke testing during normal operations is a procedure, either manual or automated, used to stroke a valve over a small percentage of the valve’s total travel range. For example, a safety interlock valve might be fully closed during normal operations. Partial valve-stroke testing could be used to move the valve to a slightly open position. This would verify valve operation without affecting normal operations. The present system could be used to undertake manual partial valve-stroke testing, or an upgraded system could be used to implement automated partial valve-stroke testing. “We are currently evaluating device management system that would be able to directly accept data from all of our HART instruments,” Moffet says, “and the system could be used to implement automated partial valve-stroke testing.” Other plans call for using additional SPA capabilities to monitor the diagnostic status of the valve-stem positioners, to provide alarm on low valve-operating air pressure, and to provide relay contacts for open and closed valve position. For more critical applications, one-outof-two (1oo2) and two-out-of-three (2oo3) configurations can be used to increase availability and reliability.
Use the Power of HART Your Wish Is HART’s Command
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ook under your nose. Though rarely in the news, HART has the largest installed base of all digital field communications protocols in the process industries. A significant percentage of the field devices in your plant are probably HART-enabled, and you almost certainly are or will soon be under pressure to bring more information from those devices to your control, asset management, and enterprise systems. But many end users haven’t made the connection. HART can do much more than serve as an occasional information bridge for device configuration and troubleshooting. In many applications it can serve as the primary means of two-way communications for system integration. Using the power of HART communication is like letting the genie out of the bottle.
Resources Are Rising When HART technology was introduced in the early 1990s, control engineers realized information from intelligent devices was valuable, but at the time there was no easy or clean way to integrate this data into control systems. For years, valuable information in these devices has languished in parts of subsystems, in limited applications such as maintenance and loop check-out tools, or ignored altogether. Meanwhile, the business situation in the process industries has changed dramatically, creating the need to maximize any and all investments and assets. Reduced manpower, budget cuts, higher profit requirements, and increased global competition have users looking at all possible
means of capturing information that can improve the operation and financial results of their plants. Highly visible discussions have promoted fieldbus capabilities and the value of additional information from remote communications. But access to information is one thing— the ability to get it full-time and without pain is another. Over the past 10 years, companies of all sizes have created HART-capable devices that operate in a hybrid fashion. These devices offer a powerful bridge between the analog and digital worlds by using the 4-20 mA signal to feed the control system as initially designed, and simultaneously carry digital HART information— which in most cases is free—with additional process variables, enhanced alarms and diagnostics information. HART Communication Foundation (HCF) members around the globe have created a cadre of instrumentation that collectively provides all the pieces of the puzzle needed to address the many needs of process control. And the HART protocol continues to evolve as a global standard. Members recently approved new HART 6 specifications that expands communications capabilities and is compatible with existing instrumentation. In addition, the HCF has initiated a significant program to educate both
users and suppliers/members on the value of full-time HART communication. The HCF web site, www.hartcomm.org, has been redesigned to make it more user-friendly as well as to provide more user-application and user-oriented information.
What to Do Take another look at HART as it applies to your company’s needs. Review your installed base of instrumentation and your current buying requirements as they are likely to show you have a significant investment in and potential to harness HART. Talk with your suppliers about how their products support the full power of HART. If they don’t, ask why. Discuss your current installation with your suppliers to ascertain the degree of HART compatibility of your system. Then map out a plan to use your assets to the fullest. There is a growing need to use intelligent data from the field to address enterprise improvements such as performance, quality, safety, reliability, profitability, maintenance, and management. No one bus or communication technology is perfect for all applications, but HART may be the simple, cost-effective, low-risk, highvalue solution you need for improved process control—and odds are you’ve already got it. ❖
Ron Helson, Director HART Communication Foundation 512/794-0369 [email protected]
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Call for Information HART Delivers Process Data to SCADA, ERP, and Asset Management Systems
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Automation gas chromatographs and calculates compressibility constants using AGA8 calculations. This information is downloaded to the HART-compatible Rosemount 3095FT flow transmitters via the HtNode every three hours. Production data is also acquired from Daniels 2500 flow computers and RTUs,” adds Tandy. The HtNode is a protocol translator that allows HART devices to communicate via Modbus. The 3095FT flow transmitter was chosen by Calumet because it provides high accuracy, is physically smaller than most flow computers, and has a competitive price. It provides differential pressure, absolute pressure, and temperature inputs on the same transmitter. The HART protocol is used for communication of process variables
ost users were attracted to HART for instrument calibration and maintenance, but many don’t realize the protocol has the power to be the main digital communication bus for applications such as SCADA, ERP, and asset management. HART provides a wealth of the type of data required by these highlevel applications. Corporations have spent billions of dollars over the past few years installing ERP and asset management systems. A tremendous amount of pressure is now being applied to process plant managers and engineers to provide data to these systems. SCADA systems must also be upgraded to improve performance and reduce costs. Existing HART instruments can accomplish these tasks in a cost-effective and low-risk manner.
Figure 1: Get Connected
SCADA Can Do More With HART The market for SCADA applications continues to grow. According to Russ Novak, director of consulting for the ARC Advisory Group, Dedham, Mass., “The worldwide SCADA systems market for the oil & gas and water & wastewater industries exceeded $650 million in 2000. This market will reach almost $780 million by the end of 2005, growing at an annual rate of 3.5%.” HART devices can be expected to play a significant role in this growth. Periodic instrument adjustment is a necessity in process plants, but continuous monitoring can be a requirement for certain applications. One of these applications is a SCADA natural gas metering system designed by Arcom Control Systems, Kansas City, Mo., for the Tejas Calumet gas plant in Louisiana (Tejas is an affiliate of Royal Dutch Shell). The Calumet gas plant receives raw natural gas from offshore pipelines and separates out liquids such as propane, ethane, and methane. The plant consumes natural gas in the process and is charged for the energy usage by its suppliers. “Our firm designed a gas flow measurement system for Calumet to internally verify the amount of energy used in various parts of the process. Calumet needed to provide check metering for gas usage,” says Jon Tandy, a project engineer for Arcom. The gas flow measurement system uses a combination of protocols to gather and process data. “Our SCADA system acquires gas composition data from Applied
HART-enabled field devices like the ones in this safety system offer both a conventional analog signal (for control) and a digital signal (for information).
and for the acquisition of device-specific historical and configuration data. Accurate measurement of gas flow with the flow transmitters is only possible with continuous composition feedback. “The gas chromatographs yield information with respect to gas composition. The SCADA system uses this data to continuously calculate correct parameters for the flow transmitters. These parameters are sent to the flow transmitters via the HtNode so that that the flow calculations are adjusted dynamically based on composition of the natural gas,” Tandy says. Another SCADA application makes use of HART’s capability to simultaneously transmit both 4-20 mA and digital signals. “HART devices were the best choice for a safety shutdown system installed in a process plant. Two independent control systems were required because
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“Tests validate the condition of the field device and often eliminate unnecessary trips to the field.” The AMR system uses spread-spectrum radio and satellite communication to extend the HART network beyond the traditional 10,000-ft. distance limitation. Spread-spectrum radios from Freewave Technologies provide the wireless link between the gateway and the HART instruments. “The radios allow great flexibility in network architecture through multipoint and repeater configurations, as well as providing reliable data transmission of the HART messages,” Tandy adds. “With the use of repeaters, HART units can be brought into a single multiplexer from a radius of 80 miles or more.” By implementing the HART-based AMR system, the pipeline company was able to realize cost savings in several ways. The paper chart recorders previously had to be collected and tabulated manually for each monthly billing.
digital fieldbus protocols have not been approved by the standards organizations for shutdown applications,” observes James Gray, director of I/A systems marketing for Invensys Process Systems, Foxboro, Mass. In this application (Figure 1), each field device must have the capability to transmit a signal to each of the two independent control systems. “A Foxboro I/A system is the DCS and a PLC was used for the safety shutdown system. In the I/A system, the fieldbus module interfaces to the HART digital communication signal from the field device. The PLC uses the 4-20 mA signal from the field device for its analog I/O as the primary input of the safety shutdown system,” continues Gray. The DCS analyzes the HART signal information and distributes this information throughout the control system. “The HART protocol is used for diagnostic information from the field device. This information can provide an active status word to the system and alert the operator of a device fault before it impacts the performance of the process. The status word is integrated into the analog input block of the control system and propagated throughout the control strategy if an error or device fault is detected,” adds Gray. If an error is found, the DCS can interact with an operator to correct the problem. “Once an error in the field devices is detected, the operator or technician can interrogate the field device from the console. Using the tools of the I/A system’s Technician’s Workbench, a poll command is sent from the operator console to the field device to read or perform a series of diagnostics,” Gray says. “These tests validate the condition of the field device and often eliminate unnecessary trips to the field.” HART capabilities can also be extended to wireless SCADA applications. A major Midwest gas pipeline company planned to replace paper chart recorders on its natural gas pipeline with an automated meter reading (AMR) system. The AMR system would have to be capable of acquiring data from devices within a radius of up to 80 miles, publishing this field data from locations throughout the Midwest to a central host in Tulsa, and integrating the data with an existing measurement system. The system architecture diagram (Figure 2) illustrates the design of the wireless SCADA system. Multivariable flow transmitters provide flow measurement and data logging capabilities. These transmitters communicate via HART over a wireless radio link to a network gateway/ multiplexer from Arcom. “Our Director gateway satisfied all the requirements for the project,” says Tandy. “The Director uses HART to acquire real-time and historical information. Data is then published to a central host via satellite.”
Figure 2: HART Works With Wireless
A gateway/multiplexer in this gas metering application acts as a HART master and publishes data using TCP/IP.
This is now done automatically with ongoing savings estimated at $1.25 million per year. Because the HART signal is transferred over the radio link, there is no need for a separate remote terminal unit (RTU) or multiplexer at each meter site. One multiplexer serves as a master to 32 HART meters and allows data consolidation. Wireless communication avoids costly cable runs to each HART meter. The multivariable flow transmitters effectively combine a traditional flowmeter and three discrete instruments into a single instrument, yielding hardware cost savings of almost 30% per site. TCP/IP communications allow remote diagnostics and configuration, reducing the need for on-site technical support. HART provides the communication tool to create an extended meter-reading network via spread-spectrum radio and satellite communication.
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“The status and diagnostic information available from each HART device can be used to automatically verify proper operation.” ERP Needs HART
Initial device configuration establishes a baseline for each instrument that can be compared to later readings to create a history for the instrument. The baseline includes not only calibration information, but also device information such as a user-designated tag number, a user-defined descriptor, and manufacturer’s information. “One specific issue in calibration management that is addressed by the HART protocol is the ability to positively confirm the identity of the device being calibrated. Prior to smart devices, there was no inherent method available to confirm the unique device identification, which is obviously required to validate the calibration history,” observes Alexander. This observation is seconded by Aventis. “Using Cornerstone with the HART interface has helped us tremendously in getting new instruments configured and calibrated quickly,” adds Humphreys. “Cornerstone also has
ERP and e-business systems from vendors such as SAP, Baan, and Oracle cannot perform as designed without extensive information from plant-floor control systems. This information is often available through existing HART devices. Plant engineers can extract data from these existing devices and provide it to ERP systems. The expenses of purchasing and installing new devices often can be avoided. Many food and pharmaceutical processes require extensive recordkeeping with respect to batch parameters. These parameters can include process variables such as pressure, temperature, and level. The multivariable capabilities of HART devices can be exploited to extract these secondary variables from existing devices. Batch records should also indicate if each field device is operating properly. The status and diagnostic information available from each HART device can be used to automatically verify proper operation. The only alternative in most cases is to have a field technician check and verify device operation.
Figure 3: Manage Change
HART Helps Manage Assets Recordkeeping also extends to instrument calibration activities. Asset management programs can use HART capabilities to automate much of the calibration and recordkeeping required for critical processes. One provider of Windows-based instrument asset management software is Applied Systems Technologies, Fort Lauderdale, Fla. Its Cornerstone software is a family of Microsoft Windows-based process instrument maintenance management tools. Aventis Crop Science uses Cornerstone software at its plant in Institute, W.Va., to configure and manage its HART-compatible instruments (Figure 3). “Each instrument is configured and trimmed in the Aventis instrument shop prior to putting the device into service,” says Brad Alexander, Applied Systems president. “The HART protocol makes it easy for the device to be automatically added to the Cornerstone database when the first connection is accomplished.” Three of the instrument shops at the site use Cornerstone, and Aventis plans to convert the rest of the shops in the near future. “We use the HART interface with Cornerstone to configure the instruments for our use and to track any changes that are made to these instruments,” says Denny Humphreys, an instrument/electrical technician with the equipment reliability group at Aventis. “These changes might be made in the field through a documenting calibrator, in the field though a field communicator, or through Cornerstone itself.”
Instrument maintenance management software can use HART data to track calibration and configuration changes.
a database that is password protected and that automatically documents every change that takes place at our site.” Aventis uses the software in conjunction with HART instruments to provide complete management of instrument calibration and maintenance. Alexander says, “The Cornerstone HART maintenance station makes it possible to confirm existing configurations, to automatically detect any configuration changes introduced in the field, to prepare configuration edits for download to an instrument upon next connection, and to reconcile any variances between the instrument database records and the devices.” The software can also be used to provide remote diagnostics by periodically polling each instrument to access device status. This information can then be used to alert the instrument shop and generate repair orders. “We use the Cornerstone monitor feature with our HART Instrument. This allows us to quickly spot any problems with an instrument including signal spiking, ground loops, or a
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“The HART interface is not proprietary so we are not tied to one instrument vendor.” process uptime can be increased by delivering field-based data directly to an EAM. When AMS is integrated with an EAM system, early predictive maintenance warnings can be provided about potential equipment problems. Trial-and-error preventive maintenance can be replaced by prioritized work orders based on actual evidence that a repair or replacement is required. Rather than scheduling field devices for maintenance based on the calendar, the EAM system receives notification from AMS that service is necessary and a work order to that effect is generated. Integration of an online AMS with an EAM system lowers overall maintenance costs and increases process uptime by providing advanced warning about potential equipment failures. By combining these important maintenance tools, companies can establish a predictive maintenance environment to keep plants running at higher efficiency with less technician involvement. Potential problems can be corrected before serious damage occurs, and the cost of maintenance can be significantly reduced. Syncrude Canada, Calgary, Alberta, is using HART and the AMS system at its oil refinery in Fort McMurray, Alberta. “During the design of our most recent process unit, a 305,000 barrel-per-day vacuum distillation unit, we decided to install all HART smart instruments and hook them up to the AMS through a Honeywell DCS,” says Gil Hurtubise, process automation specialist with Syncrude in Calgary. The AMS system works with HART devices to improve plant efficiency. “The largest economic payback is the maintenance efficiency gained by being able to access the equipment diagnostics in order to make our maintenance more predictive,” adds Hurtubise. “Equipment diagnostics also allow us to keep a history of control valve signatures. This becomes a very valuable tool as the equipment ages and also assists in planning which equipment must come out for maintenance during a planned process unit outage. It is important, however, that this tool [AMS] be set up as a working system initially and later supported on a dedicated basis through organizational structure.” Another benefit of HART was realized during plant startup. “Using the HART component of the signal allows you to be much more efficient during final construction checks, commissioning loop checks, and startup,” adds Hurtubise. “It allows you to forgo many of the point-to-point wiring checks that you would normally make with analog instruments, by making use of the digital network to prove the integrity of the wiring instantly for the entire loop.” ❖
problem with the primary element,” continues Humphreys. The HART protocol and maintenance management software allow Aventis to use instruments from many different vendors. “The HART interface is not proprietary so we are not tied to one instrument vendor or one type of documenting calibrator. Cornerstone is also able to handle many vendors through the use of model libraries and calibrator libraries that can be used anywhere on the LAN,” Humphreys says. “I have been completely sold on the HART interface for years, but it was not until I discovered Cornerstone that the benefits became so very apparent.”
Application Optimizes HART Condition and diagnostic information generated by field instruments can be captured from control networks by online applications and integrated with an enterprise asset management (EAM) or computerized maintenance manFigure 4: Leverage Assets
Bringing data from HART instruments into enterprise asset management (EAM) systems allows automatic generation of work orders based on actual device conditions.
agement system (CMMS). One such online application is Asset Management Solutions (AMS) software from Emerson Process Management, Austin, Texas. AMS provides the interface between fieldbus devices and maintenance management systems (Figure 4). This allows automatic generation of work orders based on actual device conditions. The online asset management software gathers data from HART instruments and stores it in a device-oriented database. The data is then processed, organized, and presented in graphic displays. The information can be used to speed unit startups, streamline routine maintenance, and provide early warning alerts of component failure. Overall maintenance costs can be further reduced and
V
Hidden in HART Field Devices Offer Much More Than the Process Variable
M
ost users know HART provides for limited accuracy for storage tank weighing systems. These communication of multiple data systems often measure weights up to 200,000 lbs. and items between field devices and require high precision to resolve the total weight to an a host controller or computer. acceptable level. Many existing and most new HART devices have mulMany also know that integrating additional field device data into control or maintenance strategies can improve tivariable measurement capabilities. This is true of many pressure and temperature devices; most flow, level, and system performance. What most HART users don’t know is there is an analytical devices; and all valve positioners and valve conincredible amount of data that can be communicated trollers. Table I lists common types of multivariable between their existing HART devices and control systems. devices and typical outputs available from these devices. Up to three secondary process variables in addition to Typical user estimates of available data items range from three to 10 values in addition to the process variable. The the primary process variable (total of four) can be simulactual number is 35 to 40 values depending on the type of taneously transmitted from a HART device to a host in a HART device (see sidebar, “Data Items Available for single message. This multivariable capability can be exploited in a number of ways. Communication Between HART Devices and a Host”). There is tremendous value in the data available from HART devices. “Many users have little or no idea of the Multivariables Provide Multi-Benefits measurement and process improvements that can be imple- Multivariable transmitters with a digital HART interface mented through HART devices,” says Warren Meyer, prin- offer tremendous functionality and application diversity cipal marketing specialist with The Foxboro Co., Foxboro, compared to instruments with only a 4-20 mA output. Mass. “These improvements typically require minimal Unfortunately, the average user of HART devices only engineering and can be implemented quickly and at very low Table I: Common Multivariable Devices cost. These HART devices are Device Primary and Secondary Process Variables* like icebergs—we only see Pressure transmitter Pressure, temperature, differential pressure about 20% of the functionality pH transmitter Electrode output, compensation temperature, sensor impedance and 80% is hidden from view.” Coriolis meter Mass flow, density, temperature, totalized flow The most important data items Valve positioner Target stem position, actual stem position, actuator pressure, available from HART devices output signal to actuator are the process variables. The Temperature transmitter Temperature, cold junction compensation value primary process variable is conDP level transmitter Level, pressure at cell 1, pressure at cell 2, tinuously transmitted in two temperature of capillary fluid formats: 4-20 mA analog and *HART supports up to 256 process variables in a device. However, only four of them can be transmitted in a single HART message. digital as part of the HART protocol. The primary process variable is also transmitted as a percent of range. Finally, the scratches the surface in terms of using the information loop current in milliamps can also be accessed. The loop available from them. current reading can be used to validate the signal being One of the best ways to improve plant profitability is received by the controller. to use the on-board temperature sensor located in virtuThe primary process variable digital value is expressed ally all HART devices. This sensor measures the internal as an IEEE floating-point number with up to 32-bit preci- temperature inside the field device, not the ambient or sion. This far exceeds the standard 12-bit precision offered process temperature. The manufacturer uses internal with most PLC and DCS analog input modules. device temperature to characterize the output during wide High precision can be especially useful in weighing and temperature fluctuations, thereby eliminating most of the scaling applications. Twelve-bit resolution yields very temperature-related error of the device. A user can also
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“One client…saved over $300,000/year since 1989 using the ‘free temperature measurement’ for alarming.” digitally transmit the on-board device temperature to the control system using the HART protocol. “Our clients often use the on-board temperature sensor for freeze protection alarming,” says Meyer. “During the winter months in cold climates, every process plant has some type of freeze protection on various production lines. The protection can be electric heaters, steam, or just insulation to keep the process fluid from freezing.” The conventional solution is to purchase and install a temperature sensor inside the freeze-protection housing. This can be very expensive and may not be cost-effective for many applications. “When our clients use the internal temperature measurement already available over the HART interface, all that is required is a software change to set alarm points,” adds Meyer. “One client in northern Canada with approximately 2,000 microprocessor-based transmitters estimates they have saved over $300,000 each year since 1989 using the ‘free temperature measurement’ for alarming as compared to the previous installation with 4-20 mA transmitters.” Another use of the internal instrument temperature is for ambient temperature error compensation on a dual-seal level transmitter. The ambient temperature error of the differential pressure transmitter is virtually eliminated with factory compensation using the internal temperature sensors. The problem is that the compensation is done before the dual seals are installed on a vessel, and this installation can introduce temperature errors. The temperature errors of the dual seals tend to offset each other because the error on one side is canceled by a similar error on the other side. But there still is one error that is not compensated: a shift in the output caused by a temperature-driven change in the density of the fluid inside the capillary between the two seals. As the ambient capillary temperature changes, the change in the fluid density creates an error. The low-cost solution is to take the on-board temperature inside the basic differential pressure transmitter as a good approximation of the seal fill fluid temperature. A user can then program a software compensation block with a table of the fill fluid density vs. temperature. A few basic math calculations using the distance between the seals, the span of the level measurement, and the density vs. temperature chart greatly enhance level measurement accuracy. A hydrostatic tank gauging system can be configured using pressure transmitters with a temperature secondary variable. “We multi-drop two or three pressure transmitters, each with secondary temperature variables, to create a tank level measurement system. This system is marketed as our Hydrostatic Interface Unit,” says Jim Cobb, marketing manager for Austin, Texas-based Emerson Process
Management, formerly Fisher-Rosemount. Multivariable instruments often can use multiple variables to calculate process information. A differential pressure flowmeter, for example, uses pressure taps upstream and downstream of an orifice plate, and the square root of the differential pressure is proportional to the flow. A multivariable transmitter could transmit the flow value, the upstream pressure, and the downstream pressure. Calculations performed at the instrument level can provide better accuracy and can off-load central controllers from these math-intensive tasks.
Valves Vie for Attention The multivariable features of HART are used extensively for valve control. “The management of final control elements through digital communication offers significant advantages,” says James Gray, director of I/A systems marketing, Invensys Process Systems, Foxboro, Mass. “Intelligent valve positioners provide real-time feedback of valve position, measurement of pneumatic supply pressure, and measurement of the positioner’s output signal to the actuator.” Operators can use the secondary variable Figure 1: Bring Full Closure
A smart HART loop monitor used with a HART communicating valve positioner provides a reliable and cost-effective alternative for online emergency shutdown valve testing.
information to perform remote diagnostics on valves. HART valve positioners can monitor actuator pressure (Figure 1). “Excess friction in a control valve often leads to surging conditions that can result in dangerous process upsets,” says Bud Adler, director of professional development for Moore Industries, North Hills, Calif. “Our HART loop monitor can be configured to alarm on loss of actuator pressure (a secondary variable) that often results from a clogged air filter or a torn diaphragm.” Emergency shutdown valves can use the multivariable
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“The management of final control elements through digital communication offers significant advantages.” “A prudent strategy is to upgrade the valve with a smart HART positioner and a HART loop monitor,” says Adler. “With this combination, the presence of adequate air supply can be verified and the valve can be partially stroked on a regular basis to ensure its ability to move off of the seat.” The loop monitor reads the HART secondary variable and provides stem position feedback to ensure that the valve is only partially stroked.
capabilities of a HART valve positioner. “Potentially catastrophic results can occur when an emergency shutdown valve does not close when triggered by a dangerous process upset,” Adler says. “These critical valves often go for months or even years without being stroked to assure proper operation.” Users do not stroke these valves because partial valve actuation without position monitoring can be hazardous.
Data Items Available for Communication Between HART Devices and a Host Process Variable Values1
Status and Diagnostic Alerts2
Primary Process Variable (analog) 4-20 mA current signal continuously transmitted to host
Device Malfunction Indicates device self-diagnostic has detected a problem in device operation
Primary Process Variable (digital) Digital value in engineering units, IEEE floating point, up to 24-bit resolution
Configuration Changed Indicates device configuration has been changed
Upper Range Value Primary variable value in engineering units for 20 mA point, set by user
Percent Range Primary process variable expressed as percent of calibrated range
Cold Start Indicates device has gone through power cycle
Lower Range Value Primary variable value in engineering units for 4 mA point, set by user
Loop Current Loop current value in milliamps
More Status Available Indicates additional devices status data available
Upper Sensor Limit Set by manufacturer
Secondary Process Variable 1 Digital value in engineering units available from multivariable devices Secondary Process Variable 2 Digital value in engineering units available from multivariable devices Secondary Process Variable 3 Digital value in engineering units available from multivariable devices
Commands From Host to Device
Primary Variable Analog Output Fixed Indicates device in fixed current mode Primary Variable Analog Output Saturated Indicates 4-20 mA signal is saturated Secondary Variable Out of Limits Indicates secondary variable value outside the sensor limits Primary Variable Out of Limits Indicates primary variable value outside the sensor limits
Set Primary Variable Units Set Upper Range
Device Identification
Set Lower Range
Instrument Tag User defined, up to eight characters3
Set Damping Value Set Message Set Tag
Descriptor User defined, up to 16 characters
Set Descriptor
Manufacturer Name (Code) Code established by HCF and set by manufacturer
Perform Loop Test Force loop current to specific value
Device Type and Revision Set by manufacturer
Initiate Self Test Start device self test
Device Serial Number Set by manufacturer
Get More Status Available Information Codes vary by manufacturer/device
Sensor Serial Number Set by manufacturer
Set Date
Calibration Information for 4-20 mA Transmission of Primary Process Variable Date Date of last calibration, set by user
Lower Sensor Limit Set by manufacturer Sensor Minimum Span Set by manufacturer PV Damping Primary process variable damping factor, set by user Message Scratch pad message area (32 characters), set by user Loop Current Transfer Function Relationship between primary variable digital value and 4-20 mA current signal Loop Current Alarm Action Loop current action on device failure (upscale/downscale) Write Protect Status Device write-protect indicator
1. Quality indicators for process variable data added with HART 6. 2. On/off values, eight bits, always defined as shown. Set by device selfdiagnostics. Device status alerts increased to 16 bits with HART 6. 3. Additional tag with up to 32 international characters added with HART 6.
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“This strategy provides differentiation between a sensor problem and potentially dangerous process condition.” Handheld communicators can access this information when connected to the instrument loop, but most applications would benefit from continuous monitoring of these status bits. This monitoring function is provided with some DCS and HMI software packages, but not all control and monitoring systems have this functionality. “Moore Industries
The inherent capability of HART valve positioners to provide diagnostic and preventive maintenance information has proven invaluable in an installation at the Aylesford Newsprint manufacturing mill in Aylesford, England. The mill recently constructed a new de-inking and pumping plant and installed a modern newsprint machine. The mill uses the Smart Adviser plant health monitor from Thermo Measurement, Winchester, England, to enhance the existing process monitoring and control system and to provide significant benefits in three areas: valve maintenance, valve failure, and multiplexing. “A large number of valve positioners with HART communication are in operation at the mill,” reports Peter Vincent, sales and marketing director for Thermo Measurement. “Some are installed on minor applications but many perform critical safety tasks.” The advantage of using HART-capable devices is their ability to communicate digitally on top of the traditional 4-20 mA line and transmit a wealth of data rather than only one process variable. Additional parameters that can be monitored by a HART-capable valve positioner include requested valve position, actual valve position, temperature, and actuator pressure. During normal operation, HART communication provides a cost-effective and time-saving method for identifying problematic valves and valve positioners. Instrument performance is monitored by extrapolating the digital data readings related to the requested valve position and the actual valve position and comparing the two readings (Figure 2). The software analyzes valve positioner performance and alarms when an abnormal condition occurs. “If the difference between the two readings falls outside of the normal tolerance of the valve (i.e. valve deviation), Smart Adviser logs it as a fault,” Vincent says. “The dead band or hysteresis facility is used to determine the normal delta and this is adjustable up to 25% of span to cover nearly all conditions.” In addition, should the valve deviation exceed the programmed alarm point, the critical alarm mode provides instantaneous indication of valve failure. When the maintenance schedule is drawn up, the log is studied to see which valves are frequently working outside of normal tolerances. Smart Adviser can also function as a multiplexer, collecting up to 24 channels of field data from smart valve positioners and sending it to the control system.
Plenty of Devices Device Category1
No. of Companies
No. of Devices
Actuator
3
4
Analytical
12
58
Analyzer
1
8
Cabling
1
9
Calibrator
3
3
Control
4
6
DCS
2
2
Density
7
19
Flow
24
78
Gateway
1
1
Handheld
6
6
I/O system
9
23
Interconnect
1
9
Interface
9
9
IS barrier
6
44
IS isolator
1
6
Isolator
3
16
Level
31
60
Modem
6
8
Modem IC
1
2
Monitor
4
5
Positioner
18
28
Pressure
32
66
Services
5
15
Software
17
19
Temperature
26
41
Tools
5
15
Total
2382
560
1. per HART Communication Foundation web site 2. 111 different companies
provides loop monitors that are typically panel-mounted and connected just like a handheld calibrator. When a HART status bit changes, the loop monitor provides both LED indication and a relay output,” says Adler. The relay output can be connected to an existing control and monitoring system, and the loop monitor can also
Available: Advanced Diagnostics HART devices provide eight diagnostic status bits (16 bits with the new HART 6 enhancement). These status bits can be used to provide early warning of device problems.
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“There are more than 30 diagnostic parameters available to maintenance to determine the health of a valve.” branches,” Hage says. “Windows-based software allows setup choices like input type and range, output zero and span, output damping, upscale/downscale drive, and display parameters to be easily viewed, selected, and downloaded to a HART instrument with a few clicks of a mouse.” Configuration via a computer is especially advantageous for multiple instruments with the same parameters.
provide a 4-20 mA signal based on one of the HART process variables. This allows a HART instrument to be interfaced to a control system simply and quickly. The performance of temperature transmitters can be improved by using the status and diagnostic information provided by HART devices. “Most temperature transmitters incorporate sensor diagnostics to drive the 4-20 mA output either upscale or downscale upon sensor failure. In a safety-critical application, this high or low action would often trigger an expensive and perhaps unnecessary process shutdown,” says Adler. HART compatible temperature transmitters can be used to avoid a process shutdown. “A HART loop monitor can be configured to use the status bits to provide a relay output indicating sensor failure,” Adler adds. “This strategy provides differentiation between a sensor problem and potentially dangerous process condition. For more safety-critical applications, a dual nonvoting scheme or a two-out-of-three scheme provides even more reliability.” A transmitter can lock at a fixed output value if it is placed in a manual mode for tests and not returned to automatic operation. HART’s Primary Variable Analog Output Fixed status bit can be used to detect this condition and alert an operator. Distributed control systems such as Foxboro’s I/A can automatically detect and use HART diagnostic information. “HART status and diagnostic signals can be transmitted in digital format and used by the control strategy and operator displays,” says Gray. “In addition, there are more than 30 diagnostic parameters available to maintenance to determine the health of a valve. These are available through our Technician’s Workbench I/A system module.”
Figure 2: Requested vs. Actual Valve becomes sticky or not fully positioned
Accepted Delta/tolerance (dead band/hysteresis)
Time Delta between 'requested' and 'actual' valve position
Event is time and date stamped and written to alarm log, alarm is set
Valves can be monitored by comparing requested vs. actual position data via HART.
“Another significant advantage of the PC over a handheld is that once developed, a PC configuration can be stored to disk and downloaded to multiple transmitters. The more transmitters with the same or similar setup, the more time you save,” concludes Hage. Periodic instrument adjustment is a necessity for all processes, but continuous adjustment can be a requirement for certain applications. These applications virtually necessitate a digital data interface to a smart instrument. If the composition of the fluid or gas that is being measured changes continuously and if this change in composition affects setup parameters, then continuous reconfiguration is required to maintain the accuracy of process measurements. Smart instruments equipped with HART capability can enable continuous adjustment by receiving data from instruments with respect to fluid or gas composition, using these data to automatically calculate settings, and downloading these settings to the affected instruments. Asset management software programs make extensive use of the device identification information available through HART. This information is read by the asset management program and stored in a database, allowing the program to automatically populate the database with pertinent information related to each instrument’s tag number, manufacturer, device type, final assembly number, and serial number. ❖
Configuration Is Easy With a PC Most HART users are aware that HART instruments can be configured remotely from any point on the HART data highway. This can be performed with handheld calibrators or through a host computer. Calibration performed with a host computer offers many advantages over calibration via a handheld unit. “HART transmitters feature programming options that go far beyond relatively common universal input capabilities. The arrival of simple and highly functional Windowsbased calibration and configuration software allows faster set up and more precise settings than is possible with a handheld communicator,” observes Joseph Hage, vice president of engineering, Moore Industries. Setup is simplified and time is saved by using a host computer for calibration. “Handheld calibrators often require a user to scroll through lengthy configuration
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Put It to Work Take Advantage of HART Communications by Connecting Instruments to Control Systems, Laptop PCs, or Wireless Networks
A
s we saw in the article, “Call for Information,” processing companies are using HART information in SCADA, asset management, optimization, and ERP systems. In the article, “Hidden in HART,” we saw the multitude of information available in field instruments, all of which is available for the taking. Here’s how to access all that valuable information. You will be happy to learn that not only is instrument information readily available, it is downright easy to get. What’s more, you don’t have to be a programmer. We’ll walk you through the various options available, starting with handheld terminals and working up to the most complex networking systems.
Calibrating Field Devices Virtually everyone who owns HART instrumentation knows how to connect a handheld terminal to calibrate or diagnose a field device. Essentially, you find any convenient location along the 4-20 mA signal line—between the instrument and its termination in the control room or remote data acquisition system—and clamp on an adapter. The adapter is able to read the analog and embedded digital signal without affecting the signal in any way. Many of the handheld terminals are based on Emerson Process Management’s 275 HART device, which it supplies to many HART vendors as a house brand. It was designed years ago, but it still works just fine. Newer handhelds from companies such as Smar are becoming available with Palm user interfaces. According to Jonas Berge, manager of Smar Asia-Pacific Operations in Singapore, the Palm-based devices have a Windows-like user interface. “This comes in handy, as newer-generation HART devices have more diagnostics information than ever before,” says Berge. “Some information is better visualized graphically on a large screen than on just a textbased screen like the older units.” About 80% of all process controller and field instruments have a HART interface these days, and practically every maintenance technician, operator, instrument engineer and control engineer knows how to use a handheld HART terminal to change the zero and span, or check status. In probably 99% of the process installations, this was why HART devices were bought in the first place. That was most definitely true 15 years ago, when
HART-based smart instruments first appeared on the scene. Back then, being able to work with a handheld terminal to remotely change, calibrate, and diagnose a field instrument was all the rage. Today, engineers and technicians still use this capability out in the field, but now they don’t have to. Instead of getting wet or huddling in an instrument shed, engineers and operators can interrogate and change parameters from the comfort of the plant’s control room, using software loaded on any Windowscompatible PC. All they have to do is connect the PC to the HART device network, and install a simple software package that emulates a handheld terminal. Siemens and Emerson Process Management both offer software packages—Simatic PDM and AMS respectively—that run on a PC. Both can connect directly via RS-232 to a HART multiplexer (see below), and provide all the configuration, setup, calibration, and diagnostic functions of handheld terminals. At this point, Device Descriptions (DDs) enter the picture. While a handheld terminal or PC software package has the ability to configure any HART device, DDs make the procedure much simpler, because they provide the necessary parameter locations. Every vendor that makes a HART instrument also writes a DD that can be loaded into a handheld terminal. Typically, an end user loads handheld terminals with DDs for all the field instrumentation in the plant so engineers and technicians can work with anything. Owners of the 275 HART terminals often send the unit off to the manufacturer to have the necessary DDs loaded. This is much easier for some plants than loading DDs locally. Fortunately, the latest handheld terminals and PC software packages are able to load from CD-ROMs, disks, or Internet sources, simplifying the update process. At present, there are more than 250 unique HART instruments from 70 vendors, all with individual DDs.
Getting Connected For a simple connection, a HART modem interface from MACTek will connect your PC’s RS-232 port to a HART field device. The modem connects to the 4-20 mA signal line just like the handheld communicators, and provides an RS-232 signal containing all the digital HART information. If more than a few HART devices are involved, then
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The HART Server starts working immediately. Users can start gathering HART data in a matter of minutes. The HART Server is a plug-and-play device; that is, once it is connected to the HART network via a modem, it automatically recognizes and communicates with all HART devices it can find on the network. This includes HART devices directly connected via RS-232 as well as devices connected through various control networks, multiplexers, and I/O systems. Once it establishes communication, the HART Server automatically retrieves device information. Each OPC client that connects to the HART Server can request information at any rate desired. The client can specify update frequency, dead band, and so on. The HART Server will update information as requested and send it to the client. To see how easy it is to use, download a free evaluation version of the HART Server. Just go to www.hartcomm. org, select the End User Info box, then click on HART Server. From there, you can request a demo evaluation kit that allows you to download server and related software modules on your PC and simulate the complete server functionality, free of charge for 30 days. This kit includes: ❖ HART Server software ❖ Xmtr-mv instrument simulation software (Windows NT only) ❖ GnHost diagnostic software To use these modules, simply load the software into a Windows NT, 98, or 2000 environment, associate and jumper the correct COMM ports on your PC (for example, COMM 1 for the server, COMM 2 for Xmtr-mv) and follow the instructions in the kit. You may also use your own instruments in the simulation by connecting a HART modem to the serial port.
RS-485 multiplexers from companies such as Arcom, Elcon, MTL, Pepperl+Fuchs, Stahl, or Thermo Measurement can be used (Figure 1). Up to 31 multiplexers can be connected, each with 32 loops, for a maximum of 992 devices. Some multiplexers support a multi-tier architecture that allows you to connect thousands of field devices into a single virtual network. The point is, no matter how many HART devices you want to connect—from one to thousands—the connection to your PC is simple and straightforward. All you need is a modem and a cable. And a server, of course. The HART Communication Foundation (HCF) recently announced the availability of the HART to Enterprise OPC server, or HART Server. Load this software into your PC, hook up to HART devices with a modem, and you gain real-time access to all the process-related informaFigure 1: Serial Killers
Multiplexers can be used to bring a virtually unlimited number of HART field devices into serial ports.
tion available in HART devices. With HART Server software and a $350 RS-232 link or a $2,000 multiplexer, you may have all the connective functionality you’ll ever need. The HART Server is OLE for Process Control (OPC)compliant, so it can obtain information from HART devices and pass it along to any OPC client applications, such as SCADA/HMI software, an Internet web browser, an Excel spreadsheet, SQC and SPC software, and ERP systems. For example, real-time flow transfer data obtained from a HART device can be delivered to an Excel spreadsheet. No special skill or customized software is needed. Using simple drop-down screens (Figure 2), fill-in-theblanks functions, and tag names, the HART Server can be configured to automatically collect real-time information from any number of HART devices and deliver it to any OPC client application. Once configured, the HART Server starts working immediately. Users can start gathering HART data in a matter of minutes, rather than several hours or days.
Hooking Up a HART Multiplexer If you have more than one HART device, connecting them to your control system can be done in one of two ways. The first is to run the HART signals to a HART I/O board in your control system. The second way to obtain HART data is to use a HART multiplexer. This is ideal for end users with control systems that do not yet support HART digital data for control and monitoring purposes. Users with legacy control systems also are in this situation. David Hohenstein, manager of the hardware marketing group at Pepperl+Fuchs, Twinsburg, Ohio, explains that hooking up a HART multiplexer is easy. “Just run the 4-20 mA signals from HART field devices into a HART multiplexer,” explains Hohenstein. “The multiplexer strips off the digital HART data, then sends the 4-20 mA signal on its way.” The original 4-20 mA signal is unaffected, so it can connect to a normal analog input board at a control system.
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“The multiplexer strips off the digital HART data, then sends the 4-20 mA signal on its way.” Meanwhile, the multiplexer sends the digital HART data to the control system via a serial link, typically RS-232 or RS-485. The only trick to using a HART multiplexer is that it must be compatible with the control system, says Hohenstein. “The connection to all HART instruments is standard, but every control system is different. You have to purchase a HART multiplexer with an I/O interface that works with your particular control system.” Pepperl+Fuchs has 40 different HART multiplexers, with models ranging from 32 to 255 channels. Once connected to the control system, the multiplexer becomes a passive device, serving merely as a conduit of information. When asset management or HART Server software in the control system wants data from a HART instrument, it sends the device a HART command. The command signal goes to the HART multiplexer which embeds the digital signal into the 4-20 mA loop. The command arrives at the HART device where it is acted upon. The HART device embeds the requested information into the 4-20 mA signal, and the multiplexer strips out the digital data and sends it on to the control system. Issues to be considered with HART multiplexers primarily involve speed. A multiplexer with 255 channels and a single modem operates much slower (on a channelby-channel basis) than does a 32-channel multiplexer with one modem. If a control system needs faster access to data, it can use smaller, eight or 16-channel multiplexers, or you can purchase multiplexers with multiple modems.
ment information available to any OPC client device (Figure 3). This includes web browsers, SCADA systems, ERP systems, and software that drives cell phones, handheld computers, personal digital assistants (PDAs), and wireless equipment. A control system designed and installed by SysInc Engineering to support multiple plants, process areas, and loading facilities makes extensive use of HART devices. A Windows 2000 HART OPC Server at each plant is connected directly to an Arcom 32-channel HART multiplexer via an RS-485 serial port. Approximately 70 two-wire and four-wire HART devices per plant are connected to the multiplexer. These devices include SAAB and Krohne radar level gauges, Inor
Getting More Complex
and Smar temperature transmitters, Micro Motion mass flowmeters, and Endress+Hauser volumetric flowmeters. Most of the HART devices are wired in a multi-drop configuration and connected to the HART OPC Server. Other HART devices feed into four-channel ProLinx HART/Modbus gateways that in turn feed into the Modbus OPC server. The OPC server provides a clean interface to custom as well as off-the-shelf SQL and web-based applications. Most of the devices are set up on multi-drop networks and do not use the 4-20 mA signal available from each device. The faster update time of a 4-20 mA signal took a back seat to the accuracy of the HART digital signal for this application. According to the system integrator, the client plans to take advantage of many HART features. “Our client will use the multivariable, status and diagnostics, and remote calibration capabilities of the HART devices. The most critical capabilities for this application are multivariable and device status,” says Curtis Butt, electrical engineer, SysInc. “The long-term manageability of the system required us to
Figure 2: Drop-Dead Easy
The HART Enterprise OPC server offers drop-down screens, fill-in-the-blanks functions, and tag names.
So far, we’ve only looked at HART networks that connect to a single PC. Much more capability is available for a serious user. It’s possible to connect your HART instruments into most major networks, the Internet, and even into wireless systems. Arcom, for example, sells a series of multiplexers that plug into Modbus networks. At Shell’s Tejas Calumet gas plant in Louisiana, data from Rosemount HART flowmeters is stored in Modbus registers in an Arcom HtNode multiplexer, allowing any Modbus host to access the information. A SCADA system in a PC accesses the flow data every five minutes by interrogating the HtNode device over Modbus. HART multiplexers are available that support Ethernet TCP/IP connections. Such a system could easily connect into the Internet, a plant intranet, OPC systems, or other plant network schemes based on Ethernet. In such a case, a PC or workstation equipped with HART Server software can access HART instruments anywhere on the network. With a HART Server in your PC, you can make instru-
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“The HART protocol will help us achieve better repeatability and higher accuracy.” provide not only remote access to basic variables, but also remote diagnostics and configuration.” The client and SysInc expect to see a significant improvement in the reliability of the data coming from the devices. “The old system had only local displays at each instrument,” says Butt. “Operators did not trust the system and would often revert to manual operation. Part of this was due to devices being in remote locations, which led to difficulties in calibration and verification of proper operation.” Figure 3: Opened to OPC
The HART Server can make process data available to any OPC-compliant device: web browser, SCADA system, ERP system, cell phone, PDA, wireless, etc.
Operators will now be able to remotely access devices and receive accurate information. “The new system will provide complete access to all devices including status, calibration, and configuration information,” Butt concludes. “Use of the HART protocol will help us achieve better repeatability and higher accuracy, both in the process area and in the bulk storage/inventory area.” You may never need such complex communication schemes, but it is comforting to know that HART instruments fit right in.
Connecting to Controls HART devices can connect directly to control systems and devices, allowing users to make use of instrument data for monitoring, alarming and control purposes. Allen-Bradley, Wickliffe, Ohio, provides a HART interface module for its PLC 5 and SLC programmable controllers that allows a PLC to see HART data. Installed as a remote I/O device, the module acquires data from a HART instrument, strips out the HART signals, and puts the data into a format that can be addressed by ladder logic programming.
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Pat Moyer, product manager at A-B, explains that the system is supplied with preconfigured instructions that support HART commands. “We provide several basic HART commands, but a user is free to write additional commands in ladder logic to perform whatever functions are needed, such as data logging, alarm checking, or monitoring device status.” Moyer says the HART module is a big hit among certain A-B customers. “We have users in the food and oil and gas industries that use the module extensively,” she says. Yokogawa Corp. of America, Newnan, Ga., offers hardware and software that acquire HART data and make it available to its Centum control systems. Bruce Jensen, manager of systems marketing, explains that a Centum can acquire data from a standard HART multiplexer or from its own FIO 4-20 mA input modules. “The FIO devices have a HART module that extracts the digital HART data from the 4-20 mA signal and provides both analog and digital data.” FIO devices are available in eight or 16-channel versions. Yokogawa’s Plant Resource Management software formats the HART data and makes it available to the HMI and controls software, where it can be monitored, trended, logged, and displayed. Jensen says most customers use the capability to automate instrument maintenance functions because the software supports all the standard configuration and calibration functions from an HMI screen. “We have several users, mostly in the pharmaceutical industry, who are starting to take advantage of HART data for more sophisticated purposes,” says Jensen, “but most of our users are not familiar with all the capability available within HART.” Virtually all major process control companies support HART, so it should be relatively easy to connect your control system to your own HART devices. Dave Sheppard, vice president of I/A Systems at Foxboro/Invensys, Foxboro, Mass., says Foxboro has supported HART for maintenance purposes for years. “We support the connection of HART multiplexers from several suppliers,” he explains, “and we bring the HART data into a dedicated PC where third-party software can obtain data for maintenance calibration and equipment configuration functions.” At ISA/2001 in Houston, Foxboro will unveil a new eight-channel analog I/O board with a HART module that splits out the digital signal and feeds it into standard equipment control block (ECB) modules. “The HART data will be made available to Foxboro’s HMI and process control software like any other process variable, so it can be used for control, data logging, monitoring and so on,” says Sheppard. “We are taking orders now for delivery in the
“HART data will be available like any other process variable, so it can be used for control, data logging, and monitoring.” second quarter of 2002.” Honeywell, Phoenix, is on a similar track. “We offer standard HART multiplexers from Pepperl+Fuchs or MTL,” says Joe Serafin, product manager for Plantscape I/O. “The MUX connects to the serial port of a PC, which runs Cornerstone or some other third-party HART software for maintenance and instrument calibration.” Honeywell’s customers have been asking for additional HART capabilities, so Honeywell has a HART I/O card in the works, scheduled for introduction in the near future. “The new card will strip off the HART digital data from the 4-20 mA signal and make it available to the control environment,” says Serafin. Meanwhile, if you don’t want to wait for products to become available, you can take matters into your own hands and implement a system using the HART Server.
that is supported by all software packages that claim to be OPC clients or servers, such as HMI/SCADA systems. When you get the HART system connected to the HART Server, simply go to the part of your HMI or SCADA system that defines I/O points. You will be adding the HART instruments the same way you configured your plant when you first installed the HMI/SCADA system: that is, you’ll probably use a menu-based configuration screen to define the path, device, tag name, and so on, and your HMI/SCADA system will lead you through the process. Figure 4: Dig Out All the Data
By the Numbers Here’s a step-by-step procedure for getting started with the HART Server. This should get you up and running in a matter of just a few minutes: 1. Load and install the HART Server software on your PC. You can download it from the Internet or load it from a CD-ROM. 2. Configure your PC’s COM port to communicate with the HART network. You need to tell the PC port if it will be seeing RS-232, RS-485, or RS-485 with an Ethernet adapter. The HART Server configuration screens help you do this. 3. Configure the HART Server to set up links between the data sources and the data users (what programs want to see what data?). Again, the HART Server configuration screens ask the right questions. 4. Verify and test the HART Server using the GnHost diagnostic software tool, supplied by the HART Foundation. Most of the configuration menu screens are similar to Windows Explorer. With a series of mouse clicks, you should be able to complete the configuration quickly. The HART Server will automatically detect and learn the HART devices connected to the port. At the end of the configuration process, two-way communication between the HART Server and the HART instruments will be fully established. The HART Server pass-through software lets OPC client applications send HART commands to HART instruments. Therefore, any software such as configuration or valve analysis packages that run on handheld terminals can run on a PC equipped with HART Server. Likewise, HMI and SCADA software can access data using standard OPC functions. The OPC client browses the data items available from the server and subscribes to the data items of interest. This is a standard OPC function
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Loop monitors can read all the data from HART field devices and convert it into additional signals for control systems.
You will also be able to define how often you want each parameter or groups of parameters updated, or “turned on.” When a group is turned on, the HART Server will publish the data items (i.e., update, acquire, and send the group to the client). This allows processing packages from loop controllers to process historians to obtain instrument information from the field as often as necessary, simply by making the appropriate definitions in an OPC software package.
Using Specialty Devices Several HART instrument vendors have developed specialty processors and loop monitors that perform unique diagnostic and analysis functions. In many cases, this allows you to take advantage of the information contained in your HART instruments without making a network connection or using PC software. In other words, you can solve local problems without involving the plant’s main control system. An annoying problem in many plants involves sticking valves and worn-out positioners. Such problems are usually difficult to detect for most control engineers, maintenance technicians, and even the best process control and SCADA systems. Most all these entities are usually at a loss
“We will be able to use [HART 6] for at least 10 or 15 more years, or even longer.” to explain a valve’s bad behavior when it starts hunting, sticking, and performing poorly. The answer in most plants is to pull the valve out of the line for maintenance. A HART-based smart valve positioner has all the information you need to analyze valve performance. HART data can tell how many times the valve opens and closes, how much the stem has traveled, if actuator pressure has changed, and a host of other variables that are available through HART, but are never monitored in most plants. The positioner itself can perform its own analyses. For example, the Smar FY301 performs diagnostics, collects operational statistics, and stores information pertinent to the management of the valve and actuator. But how do you get to this data, and what do you do with it? You can install a HART loop monitor to monitor any of these variables, and to sound an alarm if it sees a condition that could result in dangerous process upsets. For example, excess friction in a valve can lead to surging conditions. Loss of actuator pressure from a clogged air filter or torn diaphragm can cause a dangerous or costly control offset. A loop monitor can be set to alarm on any of these conditions. Aylesford Newsprint in Aylesford, England, has many HART-based smart valve positioners and it uses Smart Adviser from Thermo Measurement to check for faults and problems. The module accepts data from up to 24 valve positioners, performs a variety of calculations to compare the requested position to the actual position, compares it against a deadband, monitors pressure to the pneumatic actuator, and sounds an alarm if it detects a fault. The module can also act as a HART multiplexer; that is, it can collect data from the valve positioners and send it to a PC via an RS-232 link. Control systems that are not fitted with a HART modem and HART Server cannot obtain any data other than the 4-20 mA signal from HART instruments. Here, loop monitors can serve as an intermediary. For example, Moore Industries’ SPA monitor can read all the data from a HART device, extract digital data, and produce additional signals (Figure 4). It provides up to four independent relay outputs that can be used as alarms when process conditions fall outside of user-selected high or low limits. It can also pick off any of the four dynamic (analog) variables from the HART data and transmit it to the control system as a 4-20 mA signal. For example, it could take the density value from a Coriolis flowmeter, the stem position for a valve, or it can calculate an analog variable as a function of two or more other variables. Rosemount’s Tri-Loop monitor, for example, can extract the remaining three process measurements and
create three additional 4-20 mA analog signals from a single HART message. The HART 4-20 mA signal goes to a control system flanked by three additional 4-20 mA signals. This makes it possible to extract gross flow, net flow, mass flow, and process temperature from a Brooks Instruments TRi-20 flowmeter; or valve position, actuator pressure, controller process variable, and controller setpoint from Fisher, Masoneilan, Neles, Samson, Flowserve, and other valve actuators. Multivariable devices such as these are becoming available to solve specific problems and help maintenance and operations engineers obtain the most information possible from their HART devices. The best part is that all this diagnostic, status, and operations information has been available all this time, so it requires no additional investment by end users. All they have to do is go get it with handheld devices, multivariable loop monitors, or PCs and HART Servers.
HART Marches On Although HART has been available for 15 years, like Ethernet it is showing no signs of getting old. The current version is HART 5, but HART 6 has recently been approved by the foundation’s members. “HART 6 is an augmentation of the existing standard that allows the installed base to continue while incorporating new features,” says Ben Cianfrone, engineering development manager, Fluke Corp., Everett, Wash. “We will be able to use this for at least 10 or 15 more years, or even longer.” The upgrade was necessary because HART instruments are getting smarter all the time, incorporating more self-diagnostics, saving more operational history data, and reporting on the quality of the data they obtain. Someday, HART devices may even have other HART devices embedded within, such as flow computers and multi-channel temperature monitors. HART 6 makes all this possible, without making any previous HART instruments obsolete. Some of the new functions include Extended Device Status, which alerts users to situations such as, “device needs maintenance;” Device Variable Status, which allows field devices to self-validate and provide quality indicators on process data (good, poor, bad, fixed); Long Tags, which allows international characters and longer tag names; Configuration Change Counter, which determines if a field device configuration has been changed; and Block Data Transfer, which moves large blocks of data between masters and field devices. The new spec should be available for all to review at the ISA Show in September. ❖
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Get Started The HART Foundation Will Help You Extract Information From Your Field Instrumentation
T
he preceeding articles have shown how HART is much more than just a way to calibrate flowmeters. It provides an enormous amount of plant-floor information not obtainable through any other means, and you don’t need a complicated fieldbus system to get to that data. In fact, since most of your instruments, valves, and controllers already have a HART interface, obtaining real-time process information is not only easy, it is very inexpensive. All you need to do is learn how to use it. When it comes to calibration and diagnostics with handheld terminals, HART technology is so easy to learn that vendors often teach their customers over the telephone. Bud Adler, director of professional development at Moore Industries, North Hills, Calif., says he often walks people through a quick course. “It is fairly easy to lead someone through a procedure over the phone,” says Adler. “The technology is simple and the procedures are straightforward. We do it all the time.” Jon Tandy, sales engineer at Arcom Control Systems, Kansas City, Mo., agrees. “I’m the one who usually deals with HART customers from sales through tech support, and I generally educate them over the phone,” he explains. “Often, they have some basic understanding of HART already.” When you need to go beyond handheld terminals, it gets a bit more difficult. Moore Industries’ Adler travels around the country giving HART seminars at trade shows and “Lunch-and-Learn” sessions, where employees from a chemical or process plant get a sandwich and a seminar on HART. “We get everyone from instrument engineers to maintenance technicians,” says Adler, “and most are amazed to find out what the instruments already installed in their plant are capable of providing.” Some companies conduct on-site training during installation. Thermo Measurement’s signal conditioning product manager, for example, trained people at Aylesford Newsprint on-site. All this vendor activity is useful and helpful, but what the industry really needs is a better and more consistent way to teach end users about HART.
that time, HCF left all the end user promotion to the marketplace while it concentrated on helping the vendors design and develop new instruments, software, interfaces, calibrators, and similar devices. All of HCF’s educational efforts and training classes have been designed for vendors, and all of its efforts toward standardization have been aimed at solidifying and enhancing HART products. It’s accomplished that, in spades. Today, HCF has more than 130 vendor members all over the world that offer a large number and variety of HART-compliant products (Figure 1). Virtually every process instrument built today has a HART interface. In spite of all the publicity garnered by the various fieldbuses, the fact remains that HART has the largest installed base in the industry, and it is growing every day. This is in part because many Figure 1: A Global Standard
North America 46% (65) Europe 44% (62)
Australia 0.7% (1)
Asia 9.3% (14)
Total companies: 142
There are HART Communication Foundation member companies almost everywhere you’d want to go.
fieldbus-compatible instruments and devices also have a HART interface. Fieldbus users may discover they actually have two plant networks built into their devices: fieldbus and HART. The HCF realizes its future lies in educating, enlightening, and engaging users, so it has launched an End User Program. This program will teach users about the benefits of HART, establish a training curriculum, bring end users into the HCF, and involve them in the HART interface for everyone’s benefit.
Educational Support Regarding Users in a New Light The HART Communication Foundation (HCF) has been strictly a vendor group since its founding in 1993. During
Learning more about networking and HART Servers is a little bit beyond a five-minute phone call from the rep. You need training and non-vendor technical literature.
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The HCF realizes its future lies in educating, enlightening, and engaging users, so it has launched an End User Program. HCF understands. Here’s what they have in store for you: ❖ The Complete HART Guide on CD-ROM: This is an excellent way to learn how HART works, in a format that is easy to pass on to fellow workers and bosses. The CD-ROM was recently completely revised to include new topics such as HART 6, asset management, and the HART Server. The new CD-ROM is available for free from HCF, and you should be able to get a copy at the HART Foundation booth at the ISA or Interkama shows this year. To obtain a free copy via the Internet, go to the HCF web site (see next bullet). You can also call the HCF office in Austin, Texas. ❖ Web site: The HCF web site at www.hartcomm.org has been completely updated to include a new end user focus on applications, education, downloads, Q/A forums, and a newsletter. An end user can pick up a large amount of technical, product, and application information by simply browsing through the web site and following the links. ❖ End user training: The HCF plans to offer a comprehensive two-day HART technology education class, starting in 2002. Two pilot classes will be held in 2001. The classes will be taught by HCF staff and will cover the technology, using DDs, applications, device configurations, communications, and using the HART Server. To find out more about specific dates and times, contact HCF or visit the web site. After HCF runs the pilot classes, it plans to finalize the training materials so that users will be able to conduct classes themselves. This will put training out in the field, closer to end users.
HART Communication Foundation The HART Communication Foundation (HCF) is an independent, non-profit organization that provides worldwide support for the HART protocol. Established in 1993, HCF is the technology owner and standards-setting body for the HART protocol. HCF manages the protocol standards, ensures the technology is openly available for the benefit of the industry, and educates users by providing training and support for application of the HART protocol. HART Workshops Workshops are an excellent value since an engineer can often spend weeks of valuable development time overcoming the learning curve of the protocol. A workshop provides all the needed information in a two or three-day session. Workshops include:
❖ HART End User Workshops: During the latter part of 2001, the HCF will begin training courses for end users.
❖ HART Fundamentals Workshop: The HART protocol is relatively easy to implement, but can have a steep learning curve. This provides all the information and tools to efficiently develop a HART-based device.
❖ Writing Device Descriptions (DDs) Workshop: The Device Description Language (DDL) provides significant benefits to slave developers, end users, and host manufacturers. This workshop explains how to use DDL to write DDs for a product. Participants leave the workshop with a prototype DD for a HART device. Memberships HART Communication Foundation memberships are open to suppliers, system integrators, end users, and others interested in the use of the HART protocol. Regular/associate and sponsor memberships are structured for corporate members. Information-only
Coming on Board
memberships are available for non-profit educational institutions,
The HCF also realizes that end users will determine the future of HART. Already, many experienced users are asking for additional capability and functions. Although HART has been available for 10 years for field communications, it is just now entering the early adopter step in its lifecycle as a networking system. At this point in HART development, user input is critical. The HART Foundation is considering forming an end user core group to provide it with input on key issues such as HCF activities, technology issues, applications, product needs, and other ideas. If you are interested in participating, contact HCF. While fieldbus efforts are struggling to deal with a large number of unrelated and incompatible networks, HART offers an excellent alternative. The HCF and its vendor members have built a technology that works, but end users are needed now to make sure that HART continues to meet all the information and network needs of the process industry. ❖
research institutes, and government agencies. End user companies can join as a regular/associate member, and individual control engineers may join as information-only members. Members are able to attend foundation meetings; participate on committees; obtain free specification updates; get 100 free copies of the quarterly newsletter; access engineering support services; and receive discounts on workshops, development tools, protocol licenses, and device description registrations. A membership application form is available on the web site. Contact Information HART Communication Foundation 9390 Research Blvd., Suite I-350 Austin, TX 78759 Tel: 512/794-0369; Fax: 512/794-3904 Web site: www.hartcomm.org E-mail: [email protected]
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WirelessHART™ offers several advantages over other wireless alternatives. Here’s how to get started.
with your installed HART devices.
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Expanding the Possibilities By Ron Helson, Executive Director, HART Communication Foundation
A
s the technology owner and standardssetting body for the HART Protocol, the HART Communication Foundation was in a unique position to develop a wireless communication standard for process measurement and control applications. We were able to draw on the technical resources and expertise of more than 200 member companies to create a new technology that expands the capabilities of the HART Protocol while protecting the global installed base of 24+ million HART devices. WirelessHART™ Communication is a new capability defined in the HART 7 specifications that establishes the first open and interoperable wireless communication standard for the process automation industry. WirelessHART™ focuses on the needs of the industry by providing a simple, reliable, and secure technology for wireless transmission of process and diagnostic data from intelligent field devices. This new wireless standard builds on established and field-proven technologies, including the HART protocol, IEEE 802.15.4 radios, frequency-hopping, and mesh networking. These standards allowed us to create a solution that is easily deployed by instrumentation professionals—preserving the HART-enabled devices, tools, training, and work procedures used today. WirelessHART™ is fully backward-compatible with existing instrumentation, extending the value of installed HART-enabled devices. It complements, but does not replace, wired HART technology, providing an additional
capability that can benefit both your existing wired applications and new monitoring and control applications. Why wireless? Wireless provides a cost-effective additional communication path for many legacy control systems, enabling access to the intelligent information in field devices. And new measurement and control devices can be quickly and easily deployed without the physical limitation and expense of signal wire. Soon suppliers will introduce HART 7-enabled devices that will provide a new way to monitor, manage, and diagnose existing and new measurement and control instrumentation—allowing your intelligent field instruments to communicate valuable information to provide significant operational cost reductions, enable process improvements, and facilitate regulatory compliance. HART Communication is stronger than ever. Millions of HART-enabled devices are purchased and installed each year. The HART protocol continues to be the technology of choice for smart instrumentation. WirelessHART™ is yet another example of how the Foundation continues to strengthen and enhance the technology to ensure that it supports your needs and protects your investment. The following articles provide an overview of the new enhancements to the HART Protocol standard. You will learn what WirelessHART™ is, where it can be used, how it expands the benefits of HART technology, and what you need to know to start expanding the possibilities!
For more information on WirelessHART™, go to www.controlglobal.com/articles/2007/184.html. HART® and WirelessHART™ are trademarks of the HART Communication Foundation.
Advertising supplement to CONTROL S-5
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unchain your data!
WirelessHART™— Information Unchained WirelessHart™ releases the information trapped in your field devices with 100% backward-compatibility with your installed HART devices.
O
f the 24 million-plus HART-enabled devices currently installed around the globe, only about 10 percent are delivering their full diagnostic potential, a state of affairs that is poised for change,” says Ron Helson, HART Communication Foundation (HCF) Executive Director. “Development of the WirelessHART,™ standard, along with the new enhanced DDL capabilities, opens the door to the untapped functions in HART devices and simplifies the task of integrating instrumentation from multiple vendors into plant asset optimization systems.” Enhancing HART Since 1990, millions of HART devices have been installed, and most remain in service today. Protecting that installed base was paramount when the HART Foundation, with the assistance of end users and ABB, Adaptive Instruments, Coronis, Dust Networks, Elpro, Emerson Process Management, Endress+Hauser, Flowserve, Honeywell, MACTek, Omnex, Pepperl+Fuchs, Phoenix Contact, Siemens, Smar, and Yokogawa, defined the requirements for WirelessHART.™ Emerson Process Management’s director of HART and Fieldbus Technology, Marty Zielinski, says, “The WirelessHART™ standard effort has produced a fully digital protocol that uses consolidated mechanisms to reduce communications overhead and adds important capabilities to the HART standard, including alarms, alerts, status with measurements, and time synchronization, just to name a few.” The results are seen in the key technical features of the recently released HART Protocol Revision 7 (HART 7) standard:
• WirelessHART™ using IEEE STD 802.15.42006-compatible physical layer and MAC PDU to produce both mesh and point-to-point wireless networks; • Worldwide appeal using 2.4 GHz frequencyhopping, spread-spectrum technology; • Enhanced data publishing modes, including oneway publishing of process and control values; spontaneous notification by exception; ad hoc request/response; and auto-segmented block transfers of large data sets; • Dedicated bandwidth for high priority and periodic communications; • Shared bandwidth to provide elasticity for event traffic and ad hoc request/response maintenance and diagnostic messages; • Time-stamped data gathered at time of measurements in order to provide improved signal processing and control; • Time-triggered actions/measurements for synchronized operation across multiple devices (e.g., vibration sensors); • Highly secure communications using AES-128 bit encryption with individual Join and Session Keys and Data Link Level Network Keys; • QoS messaging applied to all messages to ensure complete and prioritized delivery; • Clear Channel Assessment channel-hopping, blacklisting, and adjustable transmit power support to maximize coexistence between WirelessHART™ networks and other ISM-band equipment; • Multiple sequential data points of the same process variable in a single data packet; • Command aggregation for embedded multiple
S- Advertising supplement to CONTROL
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read commands in a single transaction, giving faster configuration uploads; • Backward-compatibility for the 24-plus million installed HART devices; • Multiple power options capable of using long life batteries, solar, loop, or line power sources. HART FOR PROFIT: USING THE DATA From its very beginning, the HART protocol has provided far more capabilities than configuring field devices. First, it provides real-time device diagnostics as well as multivariable device information. When effectively used, HART information has repeatedly enabled companies to lower operating cost and increase plant availability and reliability, thereby improving plant competitiveness. “Yes, we’re going to move into WirelessHART,™ says Rob Brooks, process control supervisor, PPG Industries, Lake Charles, La., who has been experimenting with wireless for three years. “We already have an AMS system. Ease-of-use-wise and cost-wise, wireless is the way to go.” In a traditional hardwired HART installation, a pair of wires connects the HART field instrument with a host system. On that pair of wires are two signals, a 4-20mA analog signal that carries the
Wireless Access to HART Device Information Easy Access to Intelligent Device Information
Existing HART Device Wireless Adaptor
primary process measurement – flow, pressure, temperature, etc. Simultaneously riding on that same pair of wires is an all-digital signal that contains HART device information – secondary measurement values, device health, and other process and diagnostic information. The release of the HART 7 standard added WirelessHART™ as an additional means of communicating the all-digital HART diagnostic and multivariable device information and even the basic process variable, if required. “While developing the WirelessHART™ standard, the committee remained vigilant of two key requirements,” says Wally Pratt, the HART Communication Foundation’s chief engineer. “It must be easy to deploy, and it must be easy to use. There should be no need for users to learn about radio technologies, communication linking or become antenna experts.” With the help of experts in process applications, wireless technologies and the HART protocol, the HCF thoroughly investigated wireless technologies, assembled the best elements, and added them to the popular HART specification. The result is that WirelessHART™ complements wired HART; it does not replace it. WirelessHART™ Device Wireless Gateway HART Data
Enabled by Wireless Adapter Device Status, Diagnostics, Configuration and more
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Advertising supplement to CONTROL S-9
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UNCHAIN YOUR DATA!
Wireless Access to Additional Process Measurements Wireless Gateway Connection to Plant Systems Minimal Installation Cost - No Wires Battery, Solar or Field Powered Devices
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HOW IT WORKS Hesh Kagan, Invensys’ director of technology, explains, “WirelessHART™ and SP100 use the same radio and mesh networking stacks. Though WirelessHART™ has some underlying differences, it could certainly be run as one of SP100’s protocols.” WirelessHART™ technology is based on the international radio technology standard, IEEE802.15.4 2.4GHz. These are low-power radios, making them ideal for industrial environments, and they are cost-effective and available from multiple sources. Conforming to international regulations, a +10dBm amplifier is used that allows a device-to-device communication range of approximately 650 ft. (200m). All WirelessHART™ field devices are required to be capable of routing messages from one device to another, effectively increasing the reach of a network beyond a single transmission link. Major features of the WirelessHART™ protocol include: • Time Division Multiple Access (TDMA) – This technique provides scheduled transmissions over the network in a series of 10ms time slots. This coordinates data transmissions, reduces power consumption, and eliminates data collisions within the network, effectively using bandwidth and reducing communication latency. • Frequency-Hopping – These techniques continually switch transmissions among different bands. This prevents potentially disruptive radio signals from blocking WirelessHART™ transmissions.
WirelessHART™ uses the IEEE-defined media access control (MAC) header, further ensuring robust, reliable co-existence with neighboring wireless networks. • Fully redundant mesh networking − WirelessHART™ permits each device to transmit its own data and relay information from other devices in the network, giving highly reliable end-to-end data communication. Each transmitting device has two routes to send data to the network gateway. The alternate (self-healing) route is automatically established anytime a portion of the primary route is temporarily blocked either physically or by electrical interference. • Enhanced security – WirelessHART™ employs robust, industry-standard authentication security techniques that help ensure that both the network and its data are protected at all times. This includes message confidentiality (end-to-end encryption), message integrity checking, authentication (message and device), and secure procedures for devices requesting to join a network. Thomas Holmes, president of MACTek describes the potential of WirelessHART,™ saying, “It expands the possibilities for users to gain access to valuable device information already sitting in their installed field devices. Access to this information provides the key to lowering operating costs while remaining competitive. In many cases, WirelessHART™ will allow users to have access to critical diagnostics and alarm information that would not be available using traditional wired HART technology.”
S-10 Advertising supplement to CONTROL
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Wireless Cuts the ChAIns
What WirelessHART™ Can Do For You When facing new operational challenges, innovative companies find solutions using wireless technologies.
W
irelessHART™ is not just another piece of manufacturing bling—the equivalent of the newest “must have” cell phone or MP3 player that, in reality, consumers can do just fine without. Rather, it extends the power of wired HART and has the potential to become an essential part of your process plant’s communications network. It opens up new possibilities for measurement, testing, quality control, asset management, and safety. What follows is an exploration of some of these potential uses. Not just “part-time” help The truth is, and always has been, that HART communication does aid device commissioning and troubleshooting, but it is a “full-time” resource, providing multivariable process data as well as device status and health information. And now, with the introduction of WirelessHART,™ each and every one of those features and benefits are easier than ever to collect. Gareth Johnston, a Fieldbus communication specialist with ABB, says “The low cost of installing WirelessHART™ will result in the end user being able to install short-term or ad hoc process measurements to improve the view of the process, perhaps to solve quality issues.” Marty Zielinski, Emerson Process Management’s director of HART and fieldbus technology, concurs. “WirelessHART™ can also be used to add new wireless measurement points at up to 90 percent lower installed cost than conventional wired points.” Whether you need additional monitoring, easier ways to calibrate field instruments, better records of instrument configuration changes and calibration records, online insight into instrumentation status, health and performance, assistance in
diagnosing and troubleshooting instrumentation, speedier commissioning, monitoring of critical data, or even supervisory process control, wired− and now WirelessHART™− is able to meet each and every one of those requirements. The Way it could be Some major industrial users, such as BP and PPG, are installing prototype projects. Both companies have installed Emerson’s wireless systems, that company spokespersons have said are intended to be pre-standard WirelessHART™ devices that can easily be upgraded once the standard is completely released and certified devices are available. Other vendors, such as ABB, Honeywell, and Yokogawa, have also had beta test sites. But because WirelessHART™ is so new, realworld examples are not available. So to explore the benefits of WirelessHART,™ we have provided four fictitious companies with real problems found in real process operations and that demonstrate the kinds of solutions WirelessHART™ can provide. Here are the real-world challenges faced by these fictitious companies. • Everyday Chemicals wants to expand its product offerings and quickly learns that it also needs better visibility into its processes. • Faced with aging instrumentation, no visibility about instrumentation health and performance, and ever-increasing customer demands for water, Mega-Metropolis Water Treatment needs a reliable, cost-effective solution that can be updated over time and will reuse as much of its existing instrumentation infrastructure as possible. • When Really Cool Colored Inks hires a new plant manager away from a competitor, it learns why its competitor is more efficient, agile, and
S-12 Advertising supplement to CONTROL
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Rosemount Flow Measurement Rosemount Level Measurement
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The Emerson logo is a trademark and a service mark of Emerson Electric Co. ©2007 Emerson Electric Company
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A wireless signal has no way through obstacles. It will just bounce around. At least the smart one will.
Introducing Emerson’s Smart Wireless – the secure, robust, self-organizing wireless network that’s as easy to use as it is smart. With Smart Wireless, all the devices in the network can communicate with each other. Whether it meets a permanent obstacle or a temporary barrier, the self-organizing network automatically routes the signal around it. Smart Wireless is not just flexible, it’s dependable – proven to deliver greater than 99% data reliability. To find why you should rely on Smart Wireless from Emerson go to EmersonProcess.com/SmartWireless.
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going the distance
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Host Application Network Field Devices Host Application
Gateway Handheld
Network Manager
Process Automation Controller
Existing HART Devices Gateway Adaptor
profitable: It’s using asset management software to access process and instrumentation information. Really Cool wants to move in the same direction. • Giganto Refining wants to extend the interval between planned maintenance shutdowns, but to do so and remain OSHA (Occupational Safety & Health Agency)-compliant, it needs a way to extend the full proof-testing intervals of its safety instrumented systems (SIS). AD HOC MEASUREMENTS Sometimes the addition of new measurement points can help improve product quality, process reliability or plant safety. Many modern analytical instruments provide multiple variables that are accessible via WirelessHART.™ By replacing obsolete, single-purpose instrumentation with HART-aware devices and adding self-powered WirelessHART™ adapters, new and/or secondary
process measurements can be provided easily and cost-effectively. For example, Everyday Chemicals will replace several single-measurement temperature transmitters with dual-measurement tools. For each new transmitter, the original (primary) temperature measurement used the existing wiring and I/O channel and appeared on the operator’s graphic exactly like the old temperature measurement. The new (secondary) temperature measurement will be collected and reported via WirelessHART™ communication. Because of the ease of installation, Everyday Chemicals will be able to replace the old transmitters with new ones while the process remains operational. When Everyday analyzes the cost savings of not having to add long runs of conduit and wire, not having to shut down the process, not having to re-do control system upgrades and configuration, Advertising supplement to CONTROL S-17
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Wireless Cuts the ChAIns and not having to retrain operators, it will be able to add several WirelessHART™ process measurement points that increase process visibility. Armed with new process insights, the operators will be able to significantly improve Everyday Chemicals’ product quality. Aging instrumentation When you read articles in trade publications or attend conferences and user group events, it’s easy to forget that not everyone has installed cutting-edge digital fieldbus. In fact, there are still many plants with decades-old pneumatic instrumentation. A significant number of process control installations have yet to make it to the 4-20mA analog electronic era, and there are boatloads of preHART 4-20mA instruments and another boatload of HART instruments that are under-utilized throughout the world. Because WirelessHART™ is fully backwardcompatible, it opens up all sorts of opportunities to use those thousands of miles of existing wire to ease replacement of aging instrumentation as well as begin using HART information to improve process reliability, availability, and plant utilization. Like many utilities and municipalities, MegaMetropolis Water Treatment cannot justify a rate increase to cover the cost of upgrading to digital fieldbus technologies. However, it also cannot afford to maintain the status quo; it needs a reliable, cost-effective solution that can be updated over time and reuse as much of the existing instrumentation infrastructure as possible. Enter WirelessHART.™ By conducting an in-depth instrumentation audit, Mega-Metropolis will be able to develop Safety Expert Weighs In When asked about the benefits of using HART process and device information to extend safety system proof-testing intervals, exida founder and recognized safety instrumented system expert, William Goble, said, “I believe that the use of HART in SIS for purposes of performing proof-testing or semi-automatic proof-testing could be very valuable. I see an increasing number of SIS manufacturers adding HART AI/AO input modules. The downside of HART is that configuration variables can be accessed and changed via handheld communicators. Some safety transmitters require that HART be disconnected during safety operation, as the devices’ software and hardware do not provide specific protection against that possibility.”
an upgrade plan that can be accomplished within existing budget constraints. Mega-Metropolis will develop a three-year plan to replace aging, but critical existing instruments with new HART instruments, each fitted with WirelessHART™ adapters. Less critical instruments will be placed in the “replace-on-failure-pay-out-of-maintenance” category. Anytime one of these instruments fails or otherwise qualifies for replacement, Mega-Metropolis will purchase a HART instrument with a WirelessHART™ adapter and pay for it using money from its maintenance budget. Because this plan uses existing wiring, instrument replacements will be easy to install, calibrate, and commission. After a minor upgrade to existing handheld configuration devices, MegaMetropolis also will be able to configure the new WirelessHART™ parameters. With rare exceptions, a measurement will be offline for less than one hour. Armed with new process information, MegaMetropolis Water Treatment will find it can improve filter efficiency and thus filter maintenance, thereby maximizing chlorine effectiveness. The ability to analyze HART information also will enable Mega-Metropolis to reduce filter maintenance frequency, thereby freeing up more maintenance dollars to purchase additional HART instruments. Managing assets The efficient management of a business’s assets is really what CEOs are expected to do, and how well they do it is what Wall Street analysts use to reward or punish a company’s stock. Asset management information is a critical predictive maintenance component, but that’s only one of its benefits. It can also capture important institutional knowledge. Like an increasing number of companies, Really Cool Inks specializes in producing “designer products”; that is, products designed to meet specific customer and/or niche markets. The upside of designer products is the potential for greater profits; the downside is that frequently a significant amount of time elapses between production batches, and product formulations aren’t well-documented or universally understood by operators. Really Cool Ink’s new plant manager understands that in order to capitalize on the upside of designer products, his plant needs to minimize the downside impacts, and that means establishing a robust asset
S-18 Advertising supplement to CONTROL
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Wireless Cuts the ChAIns management infrastructure that can capture the deep process knowledge that resides in experienced operators, maintenance technicians, and senior automation engineers. Using a similar, but a more aggressive approach than Mega-Metropolis Water Treatment, Really Cool Ink’s plan includes using the control system and a robust process-variable historian to identify the “gold production standard” for each product, with full recognition that because some products are so infrequently produced, it will take years to develop the entire gold-standard library. Nevertheless, Really Cool Ink’s initiative isn’t about quick profits; this asset management endeavor is viewed by the entire company as strategic to its long-term success. Therefore, the chief executives are committed to the tactical implementation of the plan. To ensure that as much in-process information as possible is captured, Really Cool Inks is identifying the critical measurements and replacing all the non-HART instruments with HART-enabled and WirelessHART™ devices and adapters. During the initial instrumentation audit, Really Cool Inks has been pleasantly surprised to find that many of its instruments are already HART-capable, but because they had been installed to help simplify commissioning and calibration, device diagnostic and process information has not been collected from a single instrument. Really Cool Ink is still in the early stages of its plan to capture exactly what is required to become more efficient, agile, and profitable in the delivery of designer products. However, it knows one thing for sure; WirelessHART™ is one of the critical components to its success. Mix & Match? No Problem Few, if any, process plants use only one instrument communication means. Older plants still have miles and miles of wire. Plants using digital fieldbus communications (i.e., DeviceNET, Foundation, Profibus, etc.) likely have installed different communication protocols to meet different requirements. The result is often a plant with a little-ofthis and a little-of-that, which when examined as a whole, produces the simple question, “Is there an easy way to get information from these multiple communication protocols into one collector (repository) device?” Now, with the introduction of industrial wireless, the answer has become much simpler; You bet there is and WirelessHART™ is part of that solution!
Safety instrumented systems During the past couple of years, process industry safety standard IEC 61511/ANSI/ISA 84.0.1 and its related safety instrumented systems (SIS) have been grabbing more and more headlines. At the same time, ever-increasing energy demands are forcing companies like Giganto Refining to seek ways to extend the interval between planned maintenance shutdowns (outages) while remaining OSHA regulation-compliant. While examining what will be required to extend the interval between planned outages, one of the problems Giganto engineers have identified is the safety criteria used to design its SISs. Unless Giganto’s engineers can find a way to extend the interval between when the SIS is fully proof-tested – a complex test that requires the process to be shut down – it will not be possible to extend the interval between planned outages. Consistent with good engineering practices, Giganto uses hardwired instruments as SIS inputs. To facilitate commissioning and calibration efforts, HART instruments have been purchased and installed. Though Giganto’s engineers are aware of the process and device diagnostics available in HART devices, efforts to collect and analyze the information have yet to be undertaken. Now, with an urgency to extend the interval between full proof-testing, Giganto’s engineers are taking a hard look at HART information, especially clause 3 of the IEC 61511 standard. Clause 3 defines, among other things, the safe failure fraction (SFF): the fraction of safe failures and dangerous detected failures in relation to the total failures. After consulting with safety system consultants, Giganto’s engineers are convinced that by adding asset management software and WirelessHART™ adapters to its existing SIS HART devices, they will be able to use the HART process and device diagnostics to improve the system’s SFF and thereby extend the time between full proof-testing. What makes the WirelessHART™ adapters especially attractive is that each can be added anywhere along the transmitter wires, and the new devices do not introduce any common-cause faults. To minimize the possibility that the HART configuration variables of the safety system transmitters might be inadvertently changed via a handheld communicator, Giganto engineers will place each safety system transmitter in a double-locked instru-
S-20 Advertising supplement to CONTROL
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ment enclosure and place one key under the control of the maintenance shop foreman and the second under that of the operations supervisor. Through the use of WirelessHART,™ asset management software and some clever physical transmitter configuration security plans, Giganto Refining will be able to improve the SFF of its safety systems, thereby extending the interval between full proof-testing and, in turn, extending the interval between planned maintenance shutdowns (outages), all while remaining OSHA regulationand IEC 61511- conformant. Additional wireless opportunities Though early deployments of WirelessHART™ are expected to be adaptors installed on hardwired devices, the HART 7 standard does provide for fully wireless HART deployments. Beyond process monitoring, wireless is a natural fit to provide a cost-effective means for health, safety, and environmental monitoring in such areas as area gas detectors, water effluent, gas emissions, relief devices, steam traps, and safety showers. Area gas detectors Many process plants require numerous gas detectors throughout the plant to ensure that the air is safe to breathe and to work in. Wireless detectors will not only provide an efficient means of providing an alert to operators, but also to monitor the operational status of the devices. Water effluent, gas emissions, and relief devices The quality of any liquid or gas leaving a process facility is vitally important to maintaining environmental quality. Regulations are requiring more measurements at more frequent intervals to ensure compliance and decrease the number of fugitive emissions. Specifically, WirelessHART™ devices could be used to monitor the opening of relief valves or the condition of rupture disks. By connecting the wireless data to the environmental monitoring software for the plant, WirelessHART™ devices can provide an easy, cost-effective way to audit the required measurements without extensive modifications to existing control systems and plant wiring. Since many effluents aren’t located conveniently close to the center of the plant, the ability of WirelessHART™ devices to operate on batteries
and completely wirelessly makes these measurements possible after all. Steam traps As energy prices rise, it becomes increasingly important to limit the amount of energy wasted. Plants often have many steam traps, and these can be easily monitored for unusual steam flows, allowing notification of a need for correction of faulty operation that might otherwise go unnoticed for some time. “We’re doing some temperature profiling on a stagnant steam line that is out in the middle between two major parts of the plant,” says PPG’s Rob Brooks, “where there aren’t even junction boxes.” WirelessHART™-enabled sensors can save thousands of dollars in steam costs for very little outlay. Safety showers In the United States, OSHA’s First Alert Response guidelines require that plant operators be alerted within 10 seconds of an activated safety shower. Many remote safety showers are located in hazardous locations with no existing signal wiring. A self-powered WirelessHART™ pressure transmitter could be used and would only be required to switch on its radio when the safety shower is operated or for remote diagnostic checking. Proceed with confidence WirelessHART™ is an extension of the wellknown, widely accepted and proven-in-use HART Communication Protocol that has helped improve thousands of process control facilities worldwide. You already have the instruments; now you can unchain the data in them. By updating the device description file, the same tools you already use become suitable for use with WirelessHART™ devices. WirelessHART™ devices can be configured wirelessly too. WirelessHART™ uses the experience and knowledge gained using HART to minimize training and simplify maintenance and support activities. With WirelessHART™ you are assured of the same attention to interoperability and robustness you’ve come to expect of wired HART. You get to use the same instruments in the same way, and you get the extra benefits. Like its wired counterpart, WirelessHART™ technology ensures your investment will be protected well into the future. Advertising supplement to CONTROL S-21
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Getting Unchained
How to Get Unchained with WirelessHART™ Deploying any industrial wireless network requires addressing physical and security related issues, however WirelessHART™ offers several advantages over other wireless alternatives.
“M
any control systems do not provide access to HART data,” says Yokogawa’s Manager, Field Instruments, Kaoru Sonoda, “and wireless technology can be a practical and cost-effective solution.” The solution is not to require control system vendors to revise, or end users to rip and replace existing control systems, but rather to enable them to do an end run around the problem. But increased demands on operators and maintenance demand a simple, effective solution. Enter wireless. “Wireless technology has now been tested,” Sonoda continues, “and we believe it is capable of meeting the critical demands of the process industries.” Gareth Johnston, fieldbus communication specialist with ABB, says, “WirelessHART™ has been designed to simplify commissioning and lifetime support. The specification team always had it in mind to keep it as simple as 4-20mA. The result is that users can employ Mesh network architecture
Figure 1. WirelessHART™’s mesh network architecture allows relatively easy installation, often without an extensive site survey. The self-organizing and self-repairing nature of a mesh network is well-suited to the industrial environment.
existing knowledge and software tools to support WirelessHART™ instruments and adapters.” Flexibility by design According to Guido Stephan, director technology and processes, automation, and drives, sensors and communication, R&D technology & processes, Siemens AG, “WirelessHART™ communication will not replace wired HART, but it will offer access to diagnostic features of field devices and will allow additional applications not possible with wired devices.” WirelessHART,™ part of the new HART 7 standard, provides four ways to acquire data from field devices. The first two are the traditional wired methods, with the primary physical variable on the 4-20 mADC loop, and the digital data (diagnostics, secondary physical variables, alarms, etc.) carried on the wire and pulled off at the control system or by a handheld calibrator. The two new ways are 1) Wireless adapters for existing field device, 2) WirelessHART™ field devices, with or without wires. The wireless adapter is designed to retrofit any of the more than 24 million existing HART devices and provides wireless access to both the primary process variable and all the digital data from the device. A WirelessHART™ field device can be installed with or without 4-20 mA loop, can operate on battery power, and provides the same data access as the adapter. The wireless data is transmitted to a gateway, which connects to the control or asset management system.
S-22 Advertising supplement to CONTROL
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Planning Though the underlying technology of WirelessHART™ all but eliminates the need to conduct complex site surveys, no one is so naïve as to believe that network robustness, maintenance, and ease of future expansion (scalability) can be achieved without some degree of up-front planning. To ensure a WirelessHART™ installation meets performance expectations, users should examine these four areas: 1) Physical layout, 2) Reliability, security and coexistence, 3) Commissioning, 4) Operation and maintenance. Physical layout When users begin planning an industrial wireless network, a plant walk-through reveals the physical difficulties of achieving clear-path transmissions of
Mesh network architecture 4-20mA with HART 4-20mA with HART 4-20mA with HART Field JB
4-20mA with HART Marshalling panel
As with all previous upgrades to HART standards, HART 7 and WirelessHART™ are completely backward compatible to any installed field device. Now is probably a good time to reiterate that HART information – diagnostics, health, secondary variables, etc. – is communicated digitally on the same pair of wires as the 4-20mA primary measurement signal. Implementing WirelessHART™ simply provides another means of accessing that same HART information and more. WirelessHART™ technology is based on IEEE 802.15.4 2.4GHz radio technology. The low power requirements of radios designed to this standard make them inherently suitable for low- power mesh networks, and because of international standards, these radios are cost-effective and available from multiple sources. To ensure conformance to international regulations, each radio includes a +10dBm amplifier that supports a clear-path transmission range of approximately 650 ft. (200m). Additionally, to extend the reach of the wireless network, each field device is required to communicate its own data messages, as well as being capable of passing on data messages received from neighboring devices. (See Figure 1.) The flexibility of WirelessHART™ provides multiple options for device placement to extend both the reach and reliability of the network.
WirelessHART 4-20mA with HART
Figure 2. Fully developed, a HART network uses WirelessHART™ to unchain the valuable diagnostic and process data locked inside existing systems and provides for future expansion with a choice of wired or wireless field devices.
even a few hundred feet. Beta testers have reported that they have installed a gateway and carried a wireless instrument around to check location and quality of signal, rather than doing an extensive survey. Typically process plants have both intermittent and permanent obstacles that are likely to reduce, often times significantly, a user’s ability to establish wireless communication between fieldmounted devices. WirelessHART™’s mesh network simplifies this issue by providing multiple paths around obstacles, including the ability to go pointto-point, not just mesh. Having the flexibility to locate HART wireless adapters anywhere along the wire can simplify installation, maintenance, and security significantly, as in the case of the wireless adapters inside a marshalling cabinet where distances are minimal and intrinsic safety isn’t an issue (Figure 2). Likewise, a transmitter can be placed in an otherwise inaccessible location, say, under a large reactor, and the adapter located in a location where clearpath transmission is available. No other wireless methodology provides this flexibility. Once a physical WirelessHART™ device layout plan is developed, the next step is to examine reliability and security requirements. Advertising supplement to CONTROL S-23
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Getting Unchained Getting Your Feet Wet You may have 50 or 5000 HART-enabled devices in your plant, and all of them are working, doing their jobs. You might not want to do anything to disturb them while they work until you have some more experience with the new WirelessHART™ technology. So what to do? You can gain experience with unchaining your HART data one of two ways. First, you could find a place where you’d like to monitor process variables, but because of the expense, you’ve never been able to justify doing it before.
One of the beauties of the WirelessHART™ standard is that the wireless adapter does not need to be located at the transmitter.
This field device is installed at PPG Industries’ Lake Charles, La., facility and transmits HART data entirely wirelessly. (Photo courtesy of Emerson Process Management)
BP’s Cherry Point, Wash., refinery did that in the most publicized beta test of Emerson’s SmartWireless system. SmartWireless was designed as a WirelessHART™ precursor; that is, the system was designed to take HART data wirelessly, using hardware and firmware that approximated a best estimate about the final standard. Emerson publicly stated at the time and has reiterated since, that SmartWireless was capable of and intended to be upgraded to WirelessHART™ as soon as the standard was released and products were certified and available for sale. Marty Gering, wireless data collection coordinator and wireless worker administrator for the refinery, was in charge of the demonstration installation. Although Cherry Point is actually the second-newest refinery in the U.S., there are many locations where large bodies of uncaptured data exist. "This data is valuable," Gering said at Emerson Exchange 2006 when he discussed the installation, "but we can't touch it because of the expense of wiring and running conduit. Lube oil and bearing temperatures, among other values, are just left out of the picture." Gering is at work on another project now: the tank farm. Cherry Point was built to be a 95,000 bbl/day refinery and
Reliability, Security & coexistence Understandably, reliability and security ranked high among end-user concerns during initial discussions about deploying wireless technologies within the process industry. To that end WirelessHART™ addresses reliability and security concerns by using robust, well-proven, and highly effective techniques. In fact, when combined with built-in good neighbor/tolerant neighbor coexistence features, WirelessHART™’s use of fully proven mesh network routing techniques make it highly reliable. Like any good neighbor, WirelessHART™ devices try to avoid bad behaviors, such as talking (transmitting) too loudly, talking too often, talking too long and/or using the entire frequency band, that affect others. Tolerance is a second characteristic of being a good neighbor. Within a wire-
less network, tolerance means that receiver nodes tolerate interference caused by other nearby radio frequencies or the occasional mistake, doing what is necessary to prevent data loss. WirelessHART™ transmitters can also use a power turn-down feature to reduce the reach and/or range of the signal to avoid network conflicts. WirelessHART™’s robust security measures protect the network and its data at all times. They include message confidentiality (end-toend encryption), message integrity checking, message and device authentication, and secure procedures for devices joining the network. Industry standard techniques are used to provide authentication and encryption. WirelessHART™ also gives users the flexibility to apply their own network security strategy while preventing security from ever being disabled.
S-24 Advertising supplement to CONTROL
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To control system
Asset Management Sysytem HART data to PC via OPC or other protocol
Control Loop
Controller
WirelessHART™ gateway WirelessHART™ network using adaptors for existing instruments
has now become a 245,000 bbl/day refinery just by increasing throughput and optimization. The tank farm was built with only level and, in some cases, temperature sensors, and Gering wants to access that information wirelessly. "We're beginning a new project to connect those tanks wirelessly with backup level. We also have hundreds of valves that we'd like to have positioner information on, as well as other pressures and temperatures," Gering announced. "We have mixers with motors we'd like to monitor current on, and lots of other things. We're looking at 300 points. We want to finish the engineering this year and have a big start on implementation by the end of 2007."
In addition to the wireless field device Gering is using, the second path to unchaining HART data is only now becoming available. One of the beauties of the WirelessHART™ standard is that the wireless adapter does not need to be located at the transmitter. It can be located anywhere along the 4-20 mA current loop. As soon as adaptors become certified for compliance, you’ll be able to buy and try them out on existing wired HART instruments where you already know you want the data inside them. This will require NO rewiring and will not require taking the instruments or control valves out of service at all.
As you prepare to install and then commission WirelessHART™ systems, remember that your experience, training, and tools used for HART-enabled devices apply to WirelessHART.™ WirelessHART™ devices are configured and installed in much the same way as they have been in the past, protecting your investment and maintaining the HART experience of being easy to use. After the WirelessHART™ adapters are installed, commissioning can begin. Actually there are two parts of commissioning–network commissioning and device commissioning.
each one joins the network. But first, the network manager, which may or may not be hosted in the gateway device, must be configured with the correct network ID and device password(s). Once that is done, the network manager will automatically adjust the network’s schedule based on the requirements reported by each device as it joins the network. Because WirelessHART™ provides an additional means of collecting HART information, the commissioning procedure is similar to that for wired systems. Using existing HART configuration tools, such as a HART handheld configurator or personal computer (PC) application, users only need to configure three additional parameters–device password(s), network ID and device refresh rate. Existing handheld or PC applications can also provide a status display of the joining process
NETWORK COMMISSIONING Network commissioning begins when the gateway device is powered up and begins advertising. Being the first device in the network, the gateway establishes its own schedule that synchronizes nodes as
Advertising supplement to CONTROL S-25
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Getting Unchained and will quickly help pinpoint any communication issues. These devices also can provide access to diagnostics and supporting device calibration and maintenance operations. Device commissioning The final step to commissioning a WirelessHART™ network is to complete device verification and conduct a loop test of any wired devices. WirelessHART™ devices need no 4-20 mA loop, and have a maintenance port for testing. Commissioning and maintenance are done via standard commands or DDL. When so specified on the purchase order, device manufacturers put device tags and other identification and configuration data requested the user into each field instrument prior to shipment. After installation, the instrument identification (tag and descriptor) can be verified in the host system using a configurator (handheld communicator or PC). Some field devices provide information on their physical configuration (e.g., wetted materials). These and other configuration data can also be verified, thereby ensuring the installed instrument is suitable for the application. Such verifications are important for regulatory health, safety, and environmental conformance, as well as ISO quality requirements. Loop integrity is important when commissioning a device. For HART-enabled devices, analog loop integrity can be checked using a loop test feature, available in many HART devices. The loop test feature enables the analog signal from a HART transmitter to be fixed at a specific value so total loop integrity from device to indicators, recorders, and operator displays is correct. Additional integrity can be achieved if the ana-
log value of the primary variable (PV) is compared to the digital value being reported from the device. For example, someone might have provided an offset to the 4-20mA analog value that has not been accounted for in the control system. Comparing the digital value of the PV to the analog value verifies the entire loop is properly calibrated. Consistent with wired HART, theWirelessHART™ specification allows wireless devices and wired devices using adapters to simulate a process value to accommodate loop testing, allowing verification of data across the network, through the gateway, and into a host application. A wireless device can be set to transmit a fixed value in order to conduct this important test. Many HART configurators provide easy ways of collecting, archiving, and/or printing commissioned device information. Because WirelessHART™ uses the same configurators as hardwired HART, existing procedures for collecting and recording “as-installed” device configuration data, calibration records, and other device records remains essentially unchanged. WirelessHART™ is the first open and interoperable wireless communication standard designed to address the critical needs of process industry users. It has been carefully designed and thoroughly tested to provide reliable, robust, and secure wireless communication in real-world industrial plants. WirelessHART™ provides new ways to gather information on process parameters and monitor the performance of plant assets in areas that have previously been difficult to achieve either technically or cost-effectively. It extends the power of HART into areas that were difficult to reach with conventional wired systems, and it provides lowcost digital access to existing HART devices.
Affordable DD Based Configuration Using Your PC ProComSol, Ltd designs and manufactures both the hardware and software needed to perform complete HART device configuration and monitoring using your PC. DevCom2000 software uses the registered DD’s from the HART Foundation, allowing full access to all device parameters, including Methods. The HM-USB USB HART modem and the HM-BT-BAT Bluetooth HART modem offer significant cost savings and productivity benefits. Units meet industry standards for USB, Bluetooth, and HART connectivity. Order this affordable solution online using our secure website.
ProComSol, Ltd
Process Communication Solutions Tel. 216.221.1550 • Fax 216.221.1554 • www.procomsol.com • [email protected]
S-26 Advertising supplement to CONTROL
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4HE NEW INTEROPERABLE WIRELESS COMMUNICATION STANDARD FOR THE PROCESS INDUSTRIES
WIRELESSHARTCOMMORG (!24¤ AND 7IRELESS(!24 4- ARE TRADEMARKS OF THE (!24 #OMMUNICATION &OUNDATION
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