Wireless Process Control Gets Greater Airing

Dec. 5, 2003

Wireless technology for plant-floor applications promises a radical shift in how process control is approached. The current buzz, clearly heard at last month's ISA show, stems from the growing roster of vendors, technology "evangelists" and proud implementers of some of the first systems. Yet, this enthusiasm must be tempered by the realization that a lot of wireless capability is already installed-in the telemetry systems of some pipelines and tank farms, and in the form of extensions to microcomputer operating systems-but has not been put to use. Also, some of the early pioneers in the field, notably the Bluetooth industry consortium, are struggling to make headway in a crowded field of competing technologies, standards and applications.

The picture is hauntingly reminiscent of the early days of PCs. Even after PCs became common in offices, industrial control experts resisted the technology, properly pointing out that the machines were not industrial-strength, that operating systems were flaky, and that purpose-built controllers were doing the job just fine, thank you. But PC hardware and software vendors chipped steadily away at the technology's limitations, and, especially after the introduction of human-machine interface (HMI) software, the technology took off.

Today, control engineers worry about the safety ratings of wireless devices in industrial settings; the problems inherent with line-of-sight communications and radio interference; and the plethora of standards (such as Bluetooth, IEEE 802.11(a) and (b), CDMA and GSM cellular). But these limitations are not thwarting use of the technology in a variety of plant-automation settings.

A picture of the coming transformation can be seen at Eastman Chemical Co., Kingsport, Tenn., where a conversion of warehouse operations to wireless systems has been under way for over a year. "We started on wireless technology by giving upper management Blackberry personal digital assistants (PDAs) so that they could access their e-mail remotely," says David Hrivnak, mobile projects manager. "Then, we started using IEEE 802.11 technology for wireless communications with computers. Now, we're involved in converting our seventh warehouse to wireless data entry of incoming and outgoing inventory," he notes, adding that "we choose projects where the benefits are quantifiable in reduced manpower, better productivity or efficiency; it's evolutionary, not revolutionary."

Eastman also is dabbling in plant-floor wireless applications, says Steve Wright, an associate of Hrivnak who focuses on this area. "We've used the technology for pilot plant work, where we can put up and take down instrumentation easily, and for applications where the cost of a sensor might be $1,000, but the cost of running conduit and wire to that sensor would be $20,000-that's easy to justify." Wright foresees more enthusiasm for the technology when devices with UL Class 1, Div. 1 hazardous-location ratings are readily available.

Those are the ratings met by transmitters introduced at the ISA show by Accutech, Hudson, Mass. "We're serving a market niche with these devices," says Cliff Lewis, a sales VP at the firm. "The units offer a low-cost way to monitor a remote relief valve, or a leaky steam trap, or to provide a temporary process monitor that can be installed and removed easily." The devices utilize the unregulated 900-MHz radio bandwidth and generally make sense for low data-transfer rates over a range of a couple of thousand feet. He says that the transmitters are capable of sending a reading every 10 s for up to five years, while requiring only a C-cell battery as power.

Products and applications like these offer a glimpse at where wireless technology is likely to go in the next few years. While there will be competing standards (and the accompanying interoperability issues), control engineers will begin cherry-picking the most obvious candidates: remote sensors, temporary data-logging projects, and noncritical operations like warehousing. As users gain experience, the technology will edge closer and closer to real-time, critical plant-floor applications. There might even be justification for devices that are both hard-wired and wireless, simply to offer the best access to the all-important data.

One aspect of this accessibility can be seen at Eastman, where the in-place plant information-management system carries built-in wireless-transmission capability, which Eastman plant managers are using to tap into the database to review operating data almost at will. Similarly, at the ISA meeting, Wonderware, Lake Forest, Calif., a division of Invensys, announced compatibility with the Microsoft Tablet PC technology. Inherent in that is wireless communication into Wonderware's HMI software, again providing access to plant data. Plant managers at the Tri-City Water Pollution Control plant in Oregon City, Ore., have been using the system to monitor plant operations via Tablet PCs, in a "walk-around" fashion.

Applications like these may presage a more-conditional type of plant management, where operators gather data when and where needed and plant managers can tune in and out of the system from a PDA or remote laptop. Hardwired systems certainly will not disappear, but will be more flexible to meet new demands. And, as we get beeped from a pager while talking on a cellphone while looking at an operator screen from a wireless LAN connection, we'll start wondering how to keep up with the flow of data.

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