Fieldbus

Are end users always right? A deeper look at Foundation fieldbus, Profibus

Big new projects that could save millions in copper by deploying Foundation fieldbus or Profibus contentedly nurse at the warm and familiar breast of analog solutions.

By John Rezabek, process control specialist, ISP Corp.

At this time of parties and feasts with family and friends, it's interesting to reflect on the feasts we celebrate with our "work" family. In the large process industries, we deal with equipment full of hot, flammable, explosive, toxic substances—in the words of OSHA, "highly hazardous." We celebrate making it through a year or two or five while managing to protect our employees and contractors from harm. "Our first mission is to ensure everyone (contractors included) goes home the same as they arrived," says our plant manager. More so than market share or efficiency or sustainability, the safety of employees remains the biggest and best thing we have to celebrate.

It's serious and stressful for supervisors and management, who must concern themselves with the safety of their reports every day. For the plant manager, it's 24/7/365. From this stressful and serious workplace is born an especially heightened disdain for disruptive changes, distractions and unexpected breakdowns. Anything that's a change is confronted with extreme and arguably unfair skepticism.

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What do our vendors celebrate? Well, we know it typically isn't the smashing success of fieldbus. Fieldbus sales lag behind good ol' 4-20 mA analog by almost 10 to 1, by some accounts. Big new projects that could save millions in copper by deploying Foundation fieldbus or Profibus contentedly nurse at the warm and familiar breast of analog solutions. When fieldbus shows up at the junior high lunch, it's often shunned from the "popular table" like the debate club captain. This apparent lack of popularity has some vendors, especially those who measure success by volume and market share, declaring that fieldbus is a disappointment, if not a failure. They point to end users who say, "Fieldbus is too hard, we love HART," while admitting that few really use HART for much beyond range changes and initial configuration. This underutilization masks issues with HART that mirror the challenges of fieldbus. Those of us who use both will tell you, HART is no easier when you try to use it as a fieldbus.

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Should this apparent lack of popularity relegate fieldbus to the land of misfit toys, laser disks and Betamax? Can the Dungeons-and-Dragons geek take a cheerleader to the prom? Some vendors feel like they've been trying for 15 years to get the attention of the homecoming queen (ExxonMobil?) to no avail. But wait, this isn't junior high, is it. The fieldbus specifications were developed under the scrutiny of experienced, large process industry end users—the same people who celebrate producing saleable product from a highly hazardous process without hurting anyone. Perhaps fieldbus doesn't have greasy hair and a complexion problem—maybe it's just taken time for certain end users' tastes to mature.

One of the biggest obstacles to fieldbus adoption in North America is DCS inertia. Most of the companies that were running highway- or LCN-based systems in 1999, when early adopters were first deploying fieldbus for large projects, are still running those systems today. Many are loyal to their favorite systems supplier, which perhaps did not have a truly robust and bug-free fieldbus solution until 2010. The lifespan of our field devices can be even longer, and most large plants would struggle to justify ripping out field devices en masse even if they do date back to the days of the Laser Disc.

It is fundamentally a systems decision to adopt fieldbus, and no one spends much time, if any, discussing it with the systems boys and girls. If you're the transmitter salesman, you may not even know who these people are. Fieldbus remains a little geeky, but it's matured, no longer wears high-water trousers, and offers an unmatched and increasing wealth of features and capabilities. Unlike the fickle consumer world of fads and fashion, the serious and stressful world of process control shouldn't focus on today's popularity or sales volume as an indicator of value or capability.

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