Process industry users have been walking the path toward wireless communications for a number of years now. They are building confidence in wireless technologies one step at a time. They may have embraced smart wired instrumentation and seen process improvements. They understand the potential cost- and time-saving benefits of wireless communications, and maybe even have freed up money for a pilot project to investigate it for themselves. But faced with the need to get specific—to pick devices for their applications, commit to a trial, and the like—they find that a tough choice has to be made: Two similar wireless protocols—WirelessHart, promulgated by the Hart Communication Foundation ( www.hartcomm.org) and ISA 100.11a, promulgated by the International Society of Automation ( www.isa.org)—are competing for dominance as the enabler of smart instrumentation in Europe and North America. And these two de facto standards don’t work together. A third standard, WIA-PA, exists in China and further complicates the task for those with Asian operations.

“Unlike with wired instrumentation, if you want to mix brands of wireless field devices to get an optimum mix of measurements, you can’t. You have to have two separate host systems to talk to two different types of field devices. And they have to come from different vendors,” explains Herman Storey, who retired from Shell Oil as a senior consultant in 2009 after 42 years with the company. “If you want to use the two types, you have to stock both types and remember which goes where. With the wired standards, I only have to stock one type of pressure transmitter and I can use it as a substitute for one of the others. I can buy the best product for the best application, I can switch vendors, and I can control my pricing and cost.”

The German Association NAMUR (representing some 120 users and vendors involved in process automation) published a very strong requirements document last year asking vendors for a single wireless sensor network for use in utility substations. In his blog, News on IEC 61850 and Related Standards, consultant and trainer Karlheinz Schwarz said, “NAMUR requires to get coexistence, interoperability and interchangeability for wireless based technologies…. The far too many IEC standardized protocol stacks of the Field Busses (comprising some 12,000 pages) are causing still a lot of headaches and pain.” IEC is the International Electrotechnical Institute, a European standards setting organization.

Can’t we all get along?

In many ways, WirelessHart and ISA 100.11a are alike. They are designed to serve the same market in the same way. At an application level, they perform the same function and have the same benefits.  Brian Neal, a senior controls engineer and project manager at Wunderlich-Malec Engineering in Las Vegas, says: “I see two remarkably similar wireless standards for instrumentation. Both ISA 100.11a and WirelessHart implement IEEE 802.15.4 radio hardware. Both protocols use DDL and Device Description files. Both would eliminate a lot of PLC I/O hardware, wiring and associated schematics. I could go on and on with the similarities,” he says. “It would be a huge win-win for the manufacturers and the consumers if the standards would converge,” Neal adds.

Now an independent consultant and co-chair of the non-profit ISA100 Wireless Systems for Automation standards committee, Herman Storey has been active both in the development of ISA100 wireless standards and in the discussions to converge ISA100.11a with WirelessHart. He and 119 other people sit on a convergence committee that is part of ISA100, called Working Group 12 (WC12). According to this group, a convergence of the WirelessHart and ISA100.11a protocols is urgent and essential. The effort, says Storey, is also “way down the road toward an impasse. I think we can break the impasse, but it isn’t a given.”

The obstacles seem to be commercial rather than technical. There are two similar protocols. Investments have been made, vendors and early adopters are lined up on either side, and product certification processes have been established. The two protocols have been developed into products for sale. Marketing programs designed to win over additional customers and vendor partners are in high gear. Both sides believe their approach is “right” and others should just come over to their way of thinking.  

ON THE WEB: The Race is On. Follow the intense developments of these two, wireless standards. See who’s jumped on board with what standard and what’s next. Visit bit.ly/related_026.

WirelessHart supporters say their protocol has numbers and momentum on its side: 15 vendors committed to making products and thousands ...