Has ISA 100.11a Been Overtaken by Events?

By Andrew Bond, Industrial Automation Insider

Jul 06, 2010

Walt Boyes, editor in chief of Control magazine and one of the signatories to the appeal against the ISA100.11a standard which led to its failure to clear the ANSI hurdle back in November 2009, has broken his self-imposed silence on the subject in a recent posting on Control's "Sound Off!" blog.

In what he calls a 'capsule update on the wireless standards war,' he reiterates how presentation of the Shell-sponsored "Nice" use case at the ISA 100.11a meeting in Orlando in February revealed shortcomings in the original standard. As a result, according to Boyes, the ISA 100 committee has indeed now decided to abandon its attempt to achieve ANSI acceptance of the current version of the standard and is instead balloting on a so called "maintenance activity" that will deal with the technical issues raised by the Nice use case and, at the same time, effectively bypass the procedural issues raised by his and his colleagues' appeal.

If the ballot passes, "which," says Boyes, "it certainly will," then the aim is to have a revised and more robust field device standard ready for approval by October of this year.

All But One
The problem, as was pointed out last month, is that this whole laborious ISA 100.11a process is being overtaken by events. What prompted Boyes' posting was the announcement by Siemens (see below) that it is to become the latest vendor to introduce a family of WirelessHART devices. As Boyes points out, that means that all but one of the world's major automation vendors, the exception being of course Honeywell, and every one of the major device vendors is supporting WirelessHART. With end users calling increasingly vociferously for a single standard, most recently at that same meeting in Orlando, WirelessHART looks increasingly like the de facto answer to their wishes.

Where does that leave ISA 100.11a? In Boyes' view, pretty much with nowhere to go. While he concedes that there may be things which ISA 100.11a might eventually be able to do which Wireless HART cannot and might not, it's still going to be another between six months and a year before working products become available.

His proposed solution? Abandon the whole ISA 100.11a exercise and adopt WirelessHART as the single field device standard within ISA 100, while pressing ahead with the other aspects of ISA 100's work in such arguably equally important areas as backhaul, power harvesting and discrete manufacturing. Such a move would, of course, also eliminate the need for any further deliberations by the almost equally contentious ISA 100.12 sub-committee on convergence of ISA 100.11a and WirelessHART.

Will it happen? Chances are that among end users even those who would, in an ideal world, have preferred an ISA 100.11a solution would now opt for WirelessHART if it settled the issue and resulted in a single field device standard, but vendor politics and precedent, not least from the fieldbus wars of the '90s, hardly give grounds for optimism.

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