Communication is what's important. Whether it happens over a cable or through the air is irrelevant, so long as the link is secure and the data transfer is successful. Luckily, there are now plenty of avenues to make that happen, so wireless devices and methods are becoming as routine in process monitoring, data acquisition, automation and even control as sensors, I/O points, hardwiring, PLCs and DCSs--just like the toothbrushes, clean socks, car keys, sack lunches and other items that engineers, operators and other working people use daily.
However, wireless transmitters, antennas, site surveys and wireless protocols remain unfamiliar to many potential users. So it helps to know how those further along the learning curve use wireless to solve mundane, but persistent operational headaches.
Curing Common Complaints
For instance, Thames Power Services' 1,000-MW Barking Power Station near London recently installed 35 Rosemount 708 acoustic transmitters from Emerson Process Management to find more failed steam traps, leaking or misbehaving valves and costly boiler tube leaks, and reduce steam losses, feedwater costs and downtime (Figure 1). If a steam trap fails or a leak develops, an acoustic device in the transmitters reports sound and temperature changes, which are configured to alert operators of a potential problem. Ian MacDonald, Barking's senior control systems engineer, reports the transmitters immediately helped by identifying a leak from a high-pressure, super-heater steam trap, which would have cost £1400 for every day of downtime.
"Improving process performance is all about understanding what's happening around the plant and being able to respond quickly to any problems," explains MacDonald. "Wireless technology enables us to introduce additional measurement points quickly and cost-effectively at any location so we can gather more information to identify potential faults."
Later, Barking installed 15 more acoustic transmitters to monitor other problematic areas, including vent valves that can stick during start-up and pressure relief valves that don't seat correctly. Previous manual monitoring was time-consuming and also failed to indicate when or why a release occurred, increasing the chances of a safety, regulatory or environmental incident. The new wireless devices enable precise monitoring and alert operators when valves have opened for as little as 1 second.
Next, data is fed into Barking's existing Emerson Ovation control system, where noise levels can be trended to identify gradual changes. Repairs can then be scheduled during normal off-times to maintain maximum plant availability and avoid forced downtime. Using its existing wireless networks, more devices can be added at much lower cost than if they had to be individually wired-in. This gives the plant more opportunities for monitoring where it was previously cost-prohibitive, such as identifying blockages in Venturi eductors, which typically use inlet/outlet pressure differences to create suction and rapidly mix injected substances.
"Having already installed Emerson's Smart Wireless THUM adaptors for access to stranded HART diagnostic data in field devices, we were familiar with Smart Wireless," adds MacDonald. "The mobility and flexibility of the battery-powered wireless devices also allow us to run trials and move devices to different areas without temporary cables. As a result, we can spot early problems and improve response to malfunctioning equipment, enabling better planning and use of maintenance resources."
Finding the Right Fit
Probably the most important virtues on the road to wireless are patience and flexibility in researching, designing and implementing the most useful solution.
For instance, engineers at Valero Energy Corp.'s refinery in Wilmington, Calif., were introduced to wireless several years ago when a third-party, point-to-point wireless system was installed to extend process monitoring. However, it was cumbersome and took too much time to deliver data, according to Rick Felix, Valero's associate process control systems coordinator. So the plant's engineers sought improved wireless tools; implemented Honeywell Process Solutions' OneWireless site-wide in 2009; and have been tailoring it to suit their applications and enhancing performance ever since.