With the cost of installing new wire for networking as high as $2,000 per foot in some older plants, it's easy to understand why many manufacturers believe it makes sense to invest in wireless networking technologies to tie together plant floor devices and systems. Still, the lack of products supporting established industrial wireless standards, combined with the relative novelty of the technology in plant environments, is forcing many manufacturers to take a cautious, incremental approach to deploying wireless networks.
"We've deployed wireless technology in support of a few isolated applications, but mostly for device monitoring so far," says Ronald T. Morris, senior engineering associate at DuPont Chemical Solutions Enterprise, who spoke at a recent Wireless Summit conference sponsored by the ISA in Vancouver, B.C. "We've looked at wireless for some closed-loop control applications, but right now we're holding off."
In fact, a recent survey of 500 manufacturing organizations, conducted in part by ISA members and released at the conference, indicated that the vast majority of manufacturers pursuing wireless networks are focusing on applications such as safety and waste/water monitoring and alerting, rather than control applications, said Richard Caro, president and CEO of CMC Associates, a consulting organization.
Why are manufacturers limiting their wireless networking deployments to monitoring and alerting applications? For one thing, Caro said, manufacturers worry about the reliability and security of the networks. "They worry about things like interference to wireless networks, especially from devices such as cordless phones and microwave ovens that use the same 2.4-GHz frequency as [IEEE standard] 802.15.4 wireless networks."
Until manufacturers gain experience with the reliability of wireless networking technologies on the plant floor, they're unlikely to use them for closed-loop control applications, Caro said.
Manufacturers say they also worry about wireless network and device interoperability and the lack of a single wireless standard for industrial applications. Two standards groups, the ISA and the HART Communication Foundation, are developing industrial wireless protocol standards that are complementary and overlapping. The proposed Wireless HART standard, for example, defines a protocol to enable HART-compatible instruments and other devices to communicate securely over an 802.15.4 mesh network. The ISA's ISA100 proposed standard would do the same, while also defining different wireless applications and supporting multiple message types.
Neither Wireless HART nor ISA100 have been finalized, however. HART, experts say, is further along, having recently released a draft of its wireless protocol to members for review. The organization says it expects commercial products supporting the standard by early next year. ISA members won't vote on a final draft of its
proposed standard until next year, officials say.
Some manufacturers are waiting for products that support these standards before they use wireless networks for control applications. "We're committed to [ISA100], so we're not pursuing wireless for control until the standard is final and supported," James D. Murphy, an Eli Lilly engineering manager told the summit audience.
Others, including DuPont's Morris, said they would like to see the HART and ISA100 standards reconciled and unified before they invest in wireless, particularly for controlling applications.
Manufacturers also worry about the performance of wireless mesh networks and protocols, specifically their ability keep up with the demand of critical control applications that require low latency times. GE Global Research has been testing 802.15.4 wireless technology in industrial environments for the U.S. Department of Energy since 2004 and, at least for now, the technology can't keep up with high-speed PLC-connected control applications that require five-second or faster response times, said Daniel Sexton, a manager at GE Global Research.
Despite such concerns, a few manufacturers are forging ahead with wireless, attracted by the opportunity to transform core manufacturing processes. Aerospace giant Boeing, for example, believes wireless technology can make its manufacturing process more flexible, Research Manager Richard Paine told summit attendees. Historically, he said, wired networks have forced Boeing to used fixed tooling, such as cranes to reposition airplanes as they are
assembled. With wireless technology, he said, Boeing will be able to move the tooling rather than the plane, speeding up the process.
In pursuit of that goal, Paine said, Boeing has formed a Secure Mobile Architecture demonstration project, which has included development of Boeing's own industrial wireless protocol, based on the 802.11 wireless LAN standard. The technology, he said, has been tested in Boeing's 777 and 787 programs.
This article originally appeared in the September 2007 issue of Managing Automation.