WirelessHART Control Applications

Control Engineering magazine had a thought-provoking article, Commentary: Are you using wireless for control? Process industries editor, Peter Welander was at the ARC Advisory Group forum last month in Orlando. After hearing Emerson’s Bob Karschnia present on the topic of wireless, Peter wrote:

Listening to the presentation, I could hardly believe my ears. “30% of wireless devices are being used in control applications.” Did he really say that? The “he” in this case is Bob Karschnia, VP of wireless business for Emerson Process Management, arguably one of the largest suppliers of wireless process instrumentation and control systems today.

Peter quoted Bob in the types of applications where control was being performed:

Sure, people use wireless for monitoring applications, but about 30% of our wireless devices are in control applications. Some are open-loop control, meaning an operator will take an intervention, but they use it as a control point. Others are built into control strategies, but they’re things that have longer time constants, like supervisory control applications, tank levels, temperature control of heated jackets, and things like that with slower time constants.

It didn’t take long from when the WirelessHART standard was announced in September 2007 until the wireless devices and gateways came along. Next came the monitoring applications for applications like: spray water, remote pumps, moving rail cars, rotating reactor, wellhead/heat exchangers, temperature profiling/tank level, gross production headers, combustion engine emissions, benzene tanks, turbine units, pump vibration, rotating lime kiln, plugged filter detection, safety showers, wellhead maintenance, mobile/temporary networks, refinery management, roll bearing, and hot tanks.

Engineers, by nature, look for new ways to apply technologies in which they’ve gained confidence. It was only a matter of time before they built experience with the capabilities of these wireless devices and looked for applications beyond monitoring to include open-loop control and slower, closed-loop control.

An example might be a large, remote tank with a sight-only level indicator because of the expense in running cables. During operator rounds, the level is read and adjustments to the inlet and outlet flows are made. The reading might be made only once or twice per shift. An engineer might determine that one or two wireless level transmitters could provide readings back to the automation system for more frequent and smaller flow adjustments.

Most plants have several applications where the current practice could be greatly improved by the addition of a wireless measurement. If you’re an engineer who came upon this post, I bet you’re already thinking of at least one.

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