“Blasphemy is an epithet bestowed by superstition upon common sense.”
—Robert Green Ingersoll, American statesman and orator

No one would equate the cautious nature of process engineers to superstition. After all, they are often dealing with things that can blow up and kill people, among other dire consequences, so an insistence upon absolutely dead-solid technologies that have been proven to work before installation in a plant is not only prudent, but essential.

Yet, an idea that some might have considered almost blasphemous just a few years ago—that of using wireless technology for industrial process applications—is today gaining broader acceptance. Much of the recent focus is on wireless deployment for monitoring and data gathering based on wireless sensor networks (WSNs) using the WirelessHart standard, ratified by the Hart Communication Foundation (HCF) in 2007. Also gaining momentum is the ISA100.11a industrial wireless standard, developed by the International Society of Automation (ISA) and released last September.

Early work is showing that these and other wireless technologies can be reliable in real-world industrial environments. And as users gain more confidence, many would agree that for certain monitoring applications at least, wireless is beginning to look like a common-sense alternative for the future, given the potentially huge benefits in wiring cost savings and the increased process knowledge to be gained.

Mixed views
Now comes what for many may require the next leap of faith—consideration and use of wireless for control applications. As part of the “Control” focus for this issue of Automation World , we decided to take a look at the status and prospects for industrial wireless control. It is not a topic that many process end-users are anxious to discuss openly, for fear of controversy, perhaps. And according to vendors, there is still a mixed bag of opinion in the field.

“Most of our customers today are OK with the idea of wireless for monitoring. There might be some caveats on where they would or would not use it, but generally speaking, it’s considered an acceptable approach,” says Jeff Becker, global wireless business director for automation supplier Honeywell Process Solutions, in Phoenix. But users have a much less universal response when the topic turns to wireless control, Becker concedes. “You still get people who say, ‘No way. Never for control.’ ” Becker notes. “But you also get some customers who say, ‘Yep, I’m doing it right now,’ ” he adds. “And a lot of the customers are still somewhere in between.”

Yes, according to vendors, wireless technology is already being deployed in control applications at some process plants. In fact, between 20 percent and 30 percent of all wireless products sold by Emerson Process Management, the Austin, Texas-based automation supplier, are today being used in control applications, says Bob Karschnia, Emerson vice president, wireless.

But that statement requires some definition. There are different levels of control, of course, and neither Karschnia nor other supplier representatives are suggesting that wireless is close to being deployed for critical, high-speed control loops. Instead, users are building confidence in wireless technologies one step at a time, initially with monitoring, then by starting with the least critical control applications first and working their way up toward more critical control jobs. Early wireless control applications typically involve non-critical, open-loop control tasks, or closed-loop control applications with longer time constants such as tank level control, temperature control of heated jackets, or control of oil field steam injection for secondary recovery operations, says Karschnia.

Brain check

Supervisory control applications in which operators can provide a layer of common-sense back-up in case of problems are among the early wireless candidates. “If you’re an operator in a control room and I’m sending you a data point that’s coming in on wireless, and you get to use your brain and make a decision on what you’re going to do, that’s a form of control, and I’m okay with that,” says an engineer at one process manufacturer who asks not to be named. “But for my critical control loops, I’m a long way from doing that on wireless. I don’t think any of the vendors are quite there yet.”

Whenever process users are ready to try out wireless control, however, the standards are in place to help them do it.

WirelessHart was designed specifically to support a wide range of process-industry use cases, from simple monitoring to closed-loop control using a mesh network topology. And last year, the Hart Communication Foundation published a White Paper, “Control with WirelessHart,” available on the HCF Web site, that ...