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Off-line HART: A Great Place to Start

Sept. 16, 2013
Mobile, on Demand HART Connectivity Delivers Results at Little Cost or Risk

Todd Gordon understands how HART usage can start small and grow to become a cornerstone of a plant's reliability and maintenance strategy. As computer/instrument technician leader at We Energies, he's lived through it.

"We went through all the transitions, starting with offline handhelds and laptop PCs," Gordon explains. "One of the beauties of HART technology is that you can use it in so many ways."

At the Valley Power Plant generating station, which also provides district heating for much of downtown Milwaukee, We Energies started out as many plants do, using HART technology on handheld communicators to test control loops and configure and troubleshoot transmitters. "HART cut our loop checkout time by 50-75% because of its built-in functionality," Gordon says. Documenting calibrators that speak HART are also a "huge advantage" for the plant, increasing the efficiency and consistency of calibration tasks.

Handhelds Are First Foothold

These early chapters of the We Energies story reflect the experience of many plants in their use of the HART Protocol. For decades now, the typical plant has started by using a handheld HART communicator to perform offline device configuration, commissioning and troubleshooting tasks.

And because of the portability and at-line visibility they provide in even classified environments, the need for handhelds will likely always be with us. Indeed, suppliers continue to roll out next-generation HART communicators that bring more memory, power and features to bear.

John Balogh, director of engineering for Meriam Process Technologies, sees HART handhelds as evolving along the same lines as smart phones and other portable consumer electronics. "Smart phones perform complex tasks, but they're intuitive and easy to use," Balogh says. "Industrial products have to move in that same direction. Users want to get connected, do what they need to do and be done with it."

Balogh cites as evidence Meriam's recently introduced MFC 5150 HART communicator, which packs a 1GHz microprocessor, 4G microSD card, and 4.3-in. color touchscreen display into an optionally Atex intrinsically safe package. Importantly, the device can read native HART device descriptions (DD) files so it can interface with any device, Balogh says. Further, the unit's capacious memory allows it to carry the HART Communication Foundation's entire suite of registered DDs and accommodate 10,000 device-specific configurations. "It's really an intrinsically safe mobile computer," Balogh says.

Calibrators Pack More Punch

Today's HART handheld communicators, such as the Yokogawa YHC5150X FieldMate device shown here, pack increasingly powerful capabilities for performing instrument commissioning, configuration and maintenance operations.

Meanwhile, just as smart phones have been able to displace other purpose-built devices such as wrist-watches and navigation systems, portable documenting calibrators offer the opportunity to further streamline instrument maintenance tasks. The user interface for HART-based calibration devices also is being driven by consumer expectations, according to Ned Espy, technical director for Beamex in North America.

"With our current touchscreen user interface, it's much easier to drill down through the menus," Espy says, citing the company's MC6 calibrator and communicator. "I just handed it to a technician, and he knew exactly what to do."  And because technicians typically have a calibration-specific agenda when they visit an instrument with the MC6, the device also filters the default information displays to only show measured variables and their corresponding status. "It hides all the commissioning and other information that you don't need when calibrating in order to make it more efficient for the technician," Espy says.

The continuity of calibration procedures for WirelessHART instruments relative to wired HART is another thing that the protocol designers got right, Espy says. "For calibration, you have to physically clip onto the terminals of the WirelessHART transmitter -- but then you can test the process variable against the digital signal being transmitted using the very same methods you would use with wired HART. It's easier for the technician, the designer of the menus and the calibrator manufacturer, too." A WirelessHART device configures exactly the same way with the addition of only two paramters – the network identification and the device join key.

Notebook PCs Add Power, Visibility

The next stage of the HART user's evolutionary development is typically an offline laptop system that can bring to bear the greater computational power -- and larger screen size -- of a Windows PC. For the offline HART user, this approach can have its advantages.

PC-based software together with a HART modem can actually be less expensive than a purpose-built communicator, although your typical laptop likely isn't ruggedized for industrial use -- much less able to run in classified environments. But many users have derived significant benefit from this sort of set up. The PC's higher computation and visualization capabilities also have proved particularly useful in the periodic characterization of valve performance, for example, to determine which valves should be pulled at an upcoming turnaround.

PC-based diagnostics for final control elements were the next stop in We Energies' journey as well. "Digital valve controllers opened a whole new world of possibilities," Gordon says. "Even with offline valve diagnostics, we found many things wrong that needed to be fixed."

"You need to do both measurement and control devices," he adds. "Your plant performance will only be as strong as your weakest link."

Although WirelessHART replaced the 4-20mA analog wires with a mesh radio network, the calibration methodologies have remained essentially the same for instrument technicians. Here, an Emerson Process Management Smart Wireless (WirelessHART) temperature transmitter is calibrated using a Beamex MC6 calibrator.

Jeff Dobos, president of ProComSol and developer of DevCom2000 PC-based HART communicator software, notes that in the past the use of a PC-based HART communicator in plant environments could be awkward at best. "Carrying a laptop up a ladder is dangerous," Dobos admits, "but the advent of wireless Bluetooth-to-HART modems has changed that. Connect the Bluetooth HART modem in the hard-to-reach location, climb back down and use your PC-based HART communicator safely from the ground."  Of course another option is to connect the HART modem anywhere on the 4-20mA loop.

Setting the Stage for Fulltime Connectivity

As valuable as it is, offline HART connectivity through handhelds, communicators and portable PCs really represents only the opening volley in the HART value proposition. To realize the full potential for HART communication to enable improved plant reliability, a significant and growing number of users are moving to full-time, integrated HART connectivity.

Back at We Energies, for example, the Valley Plant has progressed to HART instrument communications that are fully integrated with its process control and asset management systems. Automated valve tests run seamlessly in the background, kicking off tiered levels of alerts -- all using HART. If no issues are detected in the course of an automated test, no alerts are generated. Issues that need attention -- but are not expected to affect operations in the near term -- go straight to a workstation running Emerson Process Management's AMS Suite asset management software for subsequent resolution. Only issues that the operator really needs to know about go to the Emerson Ovation control system operator console. "We're leveraging HART to do proactive diagnostics," Gordon explains. "We want to solve problems before they appear to the operator."

Offline HART Usage Already Widespread

In a recent survey of Control readers, a full 70% indicated they use HART communication in an offline, ad hoc fashion through handheld communicators and calibrators and/or portable PCs.

Percentage of HART Users with Integrated Connectivity

  • Occasional HART device connectivity -     70%
  • Via handheld communicator/calibrator -     68%
  • Via portable PC -     32%
The power plant also uses WirelessHART to boost safety and to quickly and easily add new measurement points. One example was a hard-to-reach temperature transmitter and thermocouple that had been installed five years ago, "but we never pulled a cable," Gordon says. WirelessHART solved that problem in short order. The company also uses WirelessHART to monitor safety showers and eyewash stations scattered through the remote areas of the plant.

Today, the plant is migrating standalone local control loops over to HART-based digital valve controllers and transmitters. Similarly, on/off valves are being retrofitted with digital valve controllers to provide diagnostic capabilities over HART. "With HART and a digital valve controller, I can remotely run a five-minute valve test and tell whether the valve is leaking through without ever taking anything apart," Gordon says.

"HART technology has made our job of keeping things up and running a lot easier," Gordon says. "When you look at how we previously used HART versus what we do with it now, it's an incredible leap in technology. Today, our rule of thumb is that if a device we're buying comes with HART, we want it."

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