Off-line HART: A Great Place to Start

Mobile, on Demand HART Connectivity Delivers Results at Little Cost or Risk

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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

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."

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