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By John Rezabek, Contributing Editor
A few months back, I received a quote from my instrument salesman that was shockingly devoid of the previously ubiquitous WirelessHART attachment. Every prior quote—in my case almost exclusively for wired devices—contained an added attachment extolling the virtues of wireless. So when I opened the one with no such addendum, I wrote him back about the missing attachment. "You must have lost it," I joked. Can anyone remember an instrument technology that was marketed with such persistence and zeal?
Perhaps that's because WirelessHART emerged in products well before the completion of the ISA 100.11 wireless specification. Consensus standards are messy and difficult for suppliers. It's much easier to create the standard and then just dish it up. Isn't this how we ended up with multiple fieldbus standards?
Well now we have multiple wireless standards. The "freedom to choose" that was so fundamental to the mission of ISA SP50 and later Foundation fieldbus is not particularly strong in the wireless arena. If you have the wrong system, you may not be free to choose your favorite field device—unless you're happy with two wireless backhauls, one for ISA 100.11 devices and one for WirelessHART.
There's some talk of convergence, but what convergence can avoid stranding hundreds of existing WirelessHART users? The Fieldbus Foundation is working on a specification for a backhaul to serve both, but host suppliers would need to push forward support of Foundation High-Speed Ethernet, instead of preempting an open solution with proprietary ones.
I worked for one of the companies that installed early betas of WirelessHART before 2005. The effort at a fairly modern refinery on the West Coast included measurements of rotating equipment bearing temperatures, which turned out to be of extraordinary value, allowing the plant to predict failures before they caused an unplanned outage. But, to this day, I've never understood why such valuable measurements—claimed to have saved tens of thousands or even hundreds of thousands of dollars—couldn't justify running wires.
And, none of us sitting around at that 2004 Technology Information Exchange (TIE) had applications that were aching for a wireless solution. We already had wireless solutions that were rarely used because they were rarely needed. We had a lot of aging legacy systems that needed a path to modern digital integration, and most of the legacy systems had wires connecting the DCS to field devices. We had scores of new safety interlock applications requiring SIL-rated safety instrumented functions—no one saw wireless helping us with that. Even tank farms, where we always dreamed of using wireless, required SIL-capable systems. No one could imagine wireless measuring up in that area. The mountain of measurements stranded due to the expense and/or complexity of running wire—that could be solved with a Zigbee or Dust radio mesh—were off the radar, as it were, of many process industry users.
WirelessHART products have been available since at least 2007, and today one can obtain compatible products from ABB, Endress+Hauser, Siemens, Pepperl+Fuchs, Emerson and others. Given the numerous installations already in the field at diverse end users, and the prestige of the excellent suppliers who support it, I'm happy to say I'm sold. WirelessHART works and delivers as advertised.
Is there anyone remaining out there who thinks otherwise? I haven't installed any personally, but I have plenty of neighbors and friends who have, and none of them are ripping it out.
Wireless is not a hard sell—most managers are ready to approve it if the expense seems justifiable. They are typically already big users of wireless, from their laptops to their iPhones and Blackberries. Maybe it is our overly conservative process culture, but I think it's really "fitness for purpose" that causes most users to just keep yanking in their copper twisted pairs.