ONE OF THE most discussed topics in the past year has been the use of wireless communications in process automation. No other topic since the heyday of the Fieldbus Wars has generated so much interest, comment, information, disinformation, FUD (fear, uncertainty and doubt), and sheer noise.
We're going to try to cut through the noise for you, and help you separate what’s real from what’s just hype. We'll take a tour through the wireless landscape, show you the applications, talk about the technology, tell you who the players are, and show you how to write your own scorecard. After all, it’s going to be you end users who get stuck with this technology, and get to make it work in your plant.
We've written about wireless before, both in Control magazine (September 2005, November 2005) and in Sound Off!! (the Control editor's blog), and our sister magazines have covered it as well. We've also discussed wireless several times on ControlGlobal.com's Process Automation Radio Network.
What End Users Want
Herman Storey, senior automation consultant for Shell Global Solutions, and co-chair of ISA's SP100.11 committee says, "Frankly, I don't think there are as many wireless applications as some vendors believe. Those applications that can be done with wires will be done with wires."
Jim Sprague, a member of Control's editorial advisory board, and an automation engineer with a major Middle Eastern oil company adds, "What I want is for the wireless vendors and SP100 to produce standards."
Storey agrees. "Shell will not be installing more than the minimum wireless applications until there is a standard we can work with."
Despite these hurdles, many other end users have told Control that they believe wireless automation systems can be made robust enough and reliable enough to be used, even for loop control. Polls conducted by B&B Electronics ("Wireless Winning Wider Acceptance in Automation"), and by the SP100 committee itself (see "Tell SP100 What You Think" sidebar below) indicate that there’s widespread interest in having the ability to use wireless sensors for process monitoring, for asset management, and even for loop control in what they describe as "non-critical" applications. A minority of end users even believe that wireless communications can be made reliable enough to be used in critical, closed-loop control and even in safety instrumented systems (SISs).
As we’ve reported before, the bottom line is that end users want a standard or a set of standards that they can design to and procure from before they’ll use wireless in their plants other than in demonstration-type applications, or where they absolutely have no other choice.
Such "no other choice" applications abound, at least apocryphally. That is, everybody has a story, but nobody will identify where the application actually was located. There’s the steel plant that uses wireless temperature sensors to protect the water bath around the electric arc furnace. There’s the tank farm with all wireless level sensors. There are lots of others, and many vendors and even some end users will talk about them, but won't name them.
So, it's hard for end users to figure out what's FUD and what's not.
The Wireless Landscape
As we reported nearly a year ago ("Users Want and Industrial Wireless Standard," wireless isn’t like wired communications. "It’s not enough to say, as if we were Rodney King, ‘Can't we all just get along?’” says Dr. Peter Fuhr, of Apprion Corp., and chair of SP100’s interoperability committee. The wireless landscape is tricky, and littered with standards and applications that have little or nothing to do with process automation, with the exception of one glaring fact—they’re all in use in process plants from refineries to biopharma installations. As you can see in Figure 1 below, there are a lot of wireless technologies.
FIGURE 1: ALL THE DIFFERENT WAYS TO WIRELESS
Many standards can mean tough decisions of process control engineers.
In fact, as a senior ABB Inc. official told me recently, the use of wireless in discrete automation and robotics is far advanced when compared to the use of wireless in continuous process or batch process automation. "We're even delivering power to the machine wirelessly," he said.
Many plants, whether discrete, process, or hybrid are already using wireless technologies such as radio frequency identification (RFID) and WiFi (802.11b or 802.11g) both in offices and on the plant floor.
Even though there are more than 100 industrial communications buses, as long as they stay in the wired world, everything is okay, and all you have to have is interoperability between devices on the same bus. So, you can have Profibus, HART, Foundation fieldbus, Modbus, and many more devices in the same plant without worrying that adding a device or a network will cause the rest of the communications buses in the plant to go dead.
However, once you go wireless, you’re in a different world. Interoperability of devices on the same network is still an issue, but it pales in comparison to the problem of [ital]coexistence[end ital] between wireless devices on the same or adjacent networks. Now you have to decide if adding a device or another network node will work, work part of the time, or simply bring down the entire network. Wireless communications are such that you may not even know the answer until you turn the new device on.