The ruggedness of ancient instruments is both a blessing and a curse

Oct. 27, 2017
Our instrument and systems suppliers are, thankfully, more cooperative about support and repairs of our vintage instrumentation and control systems. But they have limitations.

The lightning strike was so intense, it must have been a direct strike, thought Chas. It was 5 AM as he was crossing the bridge over the refinery’s railroad yard. It came as no surprise that the strike had affected the plant, causing enough havoc with legacy 4-20 mA transmitters to make them fail high and vote for a compressor shutdown. Since the 20-year-old emergency shutdown (ESD) system had no accommodation for integration of intelligent devices, it would never be able to distinguish between the lightning-induced fault behavior and a bon fide vote to trip. Failing such instruments in the hazard direction is the safe choice, so it becomes inevitable: a spurious event like a lightning strike will invoke a spurious trip.

That we trudge ever onward with our 20-year-old devices, DCS and interlock systems stands in stark contrast to consumer appliances like the ever-evolving iPhone, Android and associated apps. Updates and enhancements seem to be non-stop. And we are compelled to replace our phone—better to call it a “pocket computer” that includes phone functionality—as often as once a year. Maybe you stubbornly hang on to your phone of yesteryear, and like me, you find out that it gets ever more bogged down with operating system updates and resource-hungry apps. When you take it to the vendor, they have few solutions aside from selling you a new device. There’s little profit for them in keeping your old phone alive.

Our instrument and systems suppliers are, thankfully, more cooperative about support and repairs of our vintage instrumentation and control systems. But they have limitations. It’s not unlikely that circuit boards from 1995 used chip-ware and silicon that’s no longer manufactured. At some point, the supplier has to draw the line and say, we just can’t service those any more. There’s also brain drain—if you’ve been doing this for 20 years, how many of the people you consulted for tech support are still in that role, if they’re employed at the same place at all? The new folks and even the ones who have stuck around are consumed with selling and supporting the current offerings, or they have been promoted into entirely new roles.

Certainly, we have to acknowledge that the level of ruggedness and durability built into our control and measurement systems is remarkable. Many of us have controllers, power supplies, I/O cards and field devices that have been energized and functioning continuously, error-free, for decades. Imagine your smart phone doing that. Or your laptop. But we all know this longevity is both a blessing—an astounding accomplishment on the part of the supplier community—and a curse. It’s a curse because we’re mired in decades-old technology, most likely proprietary technology, that has limited capability for new tech like wireless HART or fieldbus, or even Ethernet. With some work, you can probably fashion a Modbus connection to a gateway or bridge, but such deployments rarely employ all the features available.

As an industry, we are all pretty good at slogging through the swamp of day-to-day, operate-and-maintain challenges, even with a potpourri of several generations of technologies. We may think we are staying pretty close to the herd—after all, none of the plants in the complex around us are doing anything remarkable with instruments. But our brownfield brethren might be too complacent. We will compete with modern plants built with post-2010 technology, and these plants are much better positioned to leverage device intelligence. Will we be able to rip and replace fast enough when it’s clear that we can’t keep up?

Those temperature transmitters had served us flawlessly for almost 20 years, and so has the 20-something ESD system to which they’re connected. Within seconds after the lightning strike, they were back online providing protection for a vital compressor, although it took a while before the plant was back to producing saleable product. They might serve us well for another 10 or 20 years, and maybe dodge future lightning bolts. But today the zeitgeist favors using device intelligence. The door is open—or at least it isn’t locked—for us to budget and justify capital for upgrades, before the supplier totally abandons support. Why not put our brownfield sites on a path to gradually upgrade the field devices as well as the control system?

About the Author

John Rezabek | Contributing Editor

John Rezabek is a contributing editor to Control

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