Today, when discussions turn to industrial wireless networking, one often hears a curious mix of successful application stories combined with promises of much to come in the future. The field is new enough to generate a whole series of unfamiliar buzzwords that can leave managers and engineers scratching their heads in bewilderment when trying to decide which direction to go in their plant automation designs.

Wireless technology is not totally new to the factory. Remote supervisory control and data acquisition (SCADA) sites have used specialized radio telemetry for many years. Also, the growth of the network popularly called WiFi (from wireless fidelity) for personal computer (PC) networking based on the 802.11 standard of the Institute of Electrical and Electronics Engineers (IEEE) has bled over into industrial applications.

Now, however, a recent series of new sensor network products—especially for process plants—is showing promise for helping engineers achieve better plant performance. To be sure, continued bickering among technology suppliers regarding which technology is best
suited to industrial performance clouds this promise. But there are signs that the situation is beginning to sort itself out, and now may be the ideal time for manufacturing professionals to take the deep dive into the promise of wireless.

Wireless pump control

The Coca-Cola Co. purchased a plant in southern Missouri to bottle its Dasani brand of drinking water. The facility would draw water from the nearby Roubidoux Formation—the source of some of the purest water in North America. What Coca-Cola officials didn’t know, however, was that the plant was not equipped to pump the roughly 1,000 gallons of water per minute needed to meet demand. At best, the plant would be able to pump only half that amount.

Now, though, the plant is pumping more than 1,500 gallons of water per minute, thanks to a new control and data acquisition system provided by Opto 22, of Temecula, Calif. “We used Opto 22 hardware and software to build this system primarily for the sake of simplicity,” says Barrett Davis, owner of The Automate Company LLC, the Pacific, Mo., control systems integrator that designed and installed the system for Coca-Cola. “We typically build the panels for our control systems from scratch, and the Opto 22 hardware and software makes it easy to do that.”

The system includes a pump on each of the three wells, each controlled by a variable frequency drive (VFD). The three drives must work in coordinated fashion to ensure that the storage tank does not overflow. “Any of the well pumps can be designated as the lead,” Davis explains. “That pump will have a set point for moving water at a certain level of pressure, say 60 psi (pounds per square inch). Once that point is set, the pump will work to provide that level of pressure to the plant at all times. The VFD works to speed the pump up or slow it down, as necessary, to keep the pressure at that level.”

An Ethernet network for the system connects an OptoTerminal—the primary operator interface—and Snap Ultimate input/output (I/O) controller and I/O systems, many of which are connected to the network wirelessly. The system continually monitors pumping activity. It detects when a VFD is operating at maximum speed and can no longer make the lead pump push enough water to keep up the required level of pressure. When that happens, an additional pump is called into action. This new “lag” pump begins moving water at a preset minimum speed.

“Having an Ethernet-based system and running it over a wireless network means that all of the communication takes place very quickly and efficiently,” Davis says. “When the Snap Ultimate unit sends out a request for information, the response arrives within three milliseconds, as opposed to five to 10 seconds with traditional radio telemetry equipment.” This fast response time means that the plant is always operating at maximum efficiency and never pumping too much or too little water.

Possible applications

While there are already SCADA and some control applications such as this one using wireless technologies, many possible applications are awaiting the outcome of standardization efforts. There are two organizations working on standards—the Hart Communications Foundation and the SP100 committee of the Instrumentation, Systems and Automation Society (ISA). Davis Mathews, regional business unit manager for interface at Phoenix Contact, a Harrisburg, Pa.-based automation supplier, reflects the opinions of many when he notes that the SP100 committee seems to be divided on technology into two groups driven by vendors Emerson Process Management and Honeywell Process ...