Fieldbus Reigns in Process Control

Oct. 3, 2007
After nabbing the savings from easier installation, plant managers are beginning to use fieldbus for asset management.

Plant managers at the water plant in DeKalb Country, Ga., learned about the benefits of fieldbus networks quickly when they installed Profibus in their new water plant. They were so pleased with the results, they retrofitted two existing wastewater plants with the fieldbus. “It makes your life easier,” says Merat Zarreii, F&T Division manager at the DeKalb County Department of Watershed Management in Stone Mountain, Ga. “With fieldbus, I can interrogate the device from my office and get a flag if it needs maintenance or replacement.”

At the retrofitted plants, DeKalb already had Siemens control technology, which made the network communications simpler. “It wasn’t difficult to change over from analog,” says Zarreii. “Our technicians really took to the new technology and were comfortable with the change.” One of the biggest changes was the ability to change devices only when they show a problem. “We were changing out devices on a schedule before,” says Zarreii. “Now we can pinpoint what needs to be done, so we spend much less.”

Part of the ease in shifting to fieldbus was the training that DeKalb’s technicians received. “We got training from Profibus Trade Organization (PTO),” says Zarreii. “I have eight certified technicians at the plant. We even trained those technicians who have two-year degrees.”

Surprisingly, the most difficult part of the switch to fieldbus was convincing the engineering company overseeing the project to take on the digital network. “Most of the engineering companies we talked with didn’t have a lot of experience designing and installing fieldbus,” says Zarreii. “They were very limited in the design of fieldbus systems.” Zarreii persisted with pressure. “I had to twist their arms. We told them, ‘Either you do what we want or we’ll find somebody else.’ ”

Most plants implementing fieldbus technology first look to the installation savings as a justification for the switch. In recent years, however, process plants are looking for the deeper benefits of asset management. In many cases, the asset management gains come later. Often, the plant installs fieldbus to save on wiring and configuration but doesn’t get around to monitoring devices for health until much later. Recently, plant managers started to adopt fieldbus specifically for asset management and predictive maintenance. They want the big savings—fewer plant shutdowns.

Installation Savings

Even if installation savings are not the most significant benefit of fieldbus, they still matter. Those savings are often the impetus to adopt, because those savings can convince the bean counters that the project is worthwhile. “One of the biggest benefits I’ve seen is the ability to configure devices while sitting in the control room,” says Moin Shaikh, distributed control system (DCS) consultant at vendor Siemens Energy and Automation Inc., in Alpharetta, Ga. “In the old days—and still in many places—people go to the device with a handheld tool to configure it.”

Installation savings is one of the big reasons JV Industrial Companies pushes fieldbus. JV Industrial, of Laporte, Texas, is a contractor for industrial power plants. At first, company managers found their customers were skeptical of fieldbus networks. They were won over by the installation benefits. “They were leery of fieldbus at first, but they saw some benefits on the cost of wires and installation time,” says James Goodman, controls engineer at JV Industrial. “As well as saving on wiring, we also save on the calibration of the instruments themselves. Since we can monitor any problems from the network, it reduces the number of people you need for installation.” Goodman uses Foundation Fieldbus technology from Emerson Process Management

While installation savings are important, Goodman points to diagnostics and asset management as the real benefits of fieldbus. “We use diagnostics to see any problem that could be caught early on. That helps, since downtime is money,” says Goodman. “We do diagnostic work to see any problems with devices that can be caught early on.”

Carl Henning, associate director of the Profibus Trade Organization (PTO)—the Profibus and Profinet association in North America, based in Scottsdale, Ariz.—sees process plants migrating to asset management as the primary use of fieldbus networks. “At first, they looked at the installed savings. Now they’re looking at the diagnostics and the ability of fieldbus to support asset management,” says Henning. “The diagnostics allow you to troubleshoot problems and only do maintenance when it’s needed.”

In response to the potential savings in asset management, some control companies are developing technology to boost those benefits. “You will see more and more companies coming out with a diagnostic tool for the physical layer,” says Bernd Schuessler, manager of fieldbus products at Pepper+Fuchs, an automation components vendor in Twinsburg, Ohio. “We can now point to actionable items. You get noise on the line, and instead of just saying there’s noise on the line, the tool will analyze the problem, pinpoint it, and give you a recommendation on how to solve it.”

Some observers say the savings in asset management is the real point of fieldbus, that installation savings may be a mirage. “People are saying they getting value out of the installation of fieldbus, but that hasn’t been a big savings,” says Dave Applebee, process business unit manager at vendor Rockwell Automation Inc., in Milwaukee. “What’s important is being able to monitor the health of the device. You can put an alert into the control system so that device health will be part of your control strategy.”

Overcoming Resistance

Even with all the benefits of fieldbus, there is still resistance to adoption. Henning says that virtually everyone involved in new projects is asking about fieldbus. “But only 40 percent actually move to fieldbus,” says Henning. “There is still some reluctance, especially at some of the large engineering firms. They don’t want to change what they’ve always done.”

He notes that there is a big difference in adoption between discrete plants and process plants. “This is a very conservative industry on the process side,” says Henning. “On the discrete side, almost every new project involves fieldbus.” He believes that regulation is a factor. “While all plants are equally under the microscope, the discrete plants are less regulated.” Henning believes that heavy regulation translates into hesitancy in adopting new forms of technology.

One of the emerging areas of fieldbus technology is wireless. The savings in installation is potentially higher if you don’t need wires. “We’ve been exploring wireless fieldbus,” says Chuck Carter, center director and principal investigator for the Fieldbus Center at Lee College, in Baytown, Texas, where fieldbus is taught. “Wireless looks like it’s coming in a couple of years. Right now, plants are uncomfortable with it. As it matures and more testing is done, and as wireless fieldbus gets approvals from agencies, plants will see that it’s viable.”

Some don’t see wireless fieldbus as a significant change that should prompt any reluctance to adopt. “There isn’t much change with wireless fieldbus—it’s a migration,” says Ed Ladd, director of technology programs at the Hart Communication Foundation, in Austin, Texas. “Hart Foundation has developed a WirelessHart standard that is fully compatible with wire devices.” The specification was voted on and approved in June, and was ratified last month.

Ladd notes that there is plenty of interest in wireless fieldbus because of the huge benefit of eliminating wires. “We have 24 million devices in the field and each has a wire attached. The wireless system gives the user another mechanism to communicate without changing the control system,” says Ladd.

While fieldbus has become well known as a network that brings savings in installation—the wiring and the configuration process—now plants are shifting the emphasis to asset management. They want the savings that comes from catching problems before they cause a plant shutdown. They also want the savings that comes from predictive maintenance rather than preventive maintenance. Why replace a device that’s still operating well, just because it hit an operational milestone? “As the word gets out about the benefits of fieldbus, it will become more and more prominent,” says Goodman, of JV Industrial. “There was much resistance and fear of something new. But as soon as they get a feel for the benefits, they warm up quickly.”

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