Your process plant probably contains hundreds if not thousands of control, automated on/off and manual valves. Odds are that these valves are one of your main maintenance headaches because, unlike most other automation components, they contain moving parts and are thus prone to failure. One of the best ways to reduce valve maintenance issues is through remote automated control and monitoring, using both wired and wireless technology. Wired connections between valve actuators and positioners and plant automation systems are a proven method for control and monitoring. But many existing valves don't have wired connections to the automation system, and installing these wires can be prohibitively expensive. The same is true for valves that are upgraded or retrofitted into existing process areas. In either case, wireless valve actuation and monitoring can be the best solution.
So, what's the best way to wirelessly control and monitor a valve? Ira Sharp, product marketing manager for I/O and networking at Phoenix Contact, says, "WirelessHART is ideal for short distance (generally less than 500 ft) networks for sensors because it uses a mesh network that can expand with each node being a repeater for every other node in the network. Bluetooth works well for short-distance (less than 500 ft) cable replacement of sensor cables or serial/Ethernet cables."
Sharps adds, "WLAN is good for medium-distance (1000 ft to 3000 ft), high-bandwidth applications, such as video surveillance. Our Trusted Wireless and other proprietary networks are suited for long-distance (up to 20 miles) SCADA applications. UHF is ideal for very long-distance (up to 40 miles) SCADA, and cellular is the best choice for applications where private radio will not work, such as very remote areas or mobile applications."
Of the technologies mentioned, WirelessHART is perhaps the market leader. "Since WirelessHART is HART technology, it is simple to install and use, making implementation fast and low-risk," claims Chuck Micallef, marketing consultant at the HART Communication Foundation. "The key is to have an asset management or device monitoring application that will provide user access to the diagnostic information already in the HART-enabled valve positioner. A WirelessHART adapter can be added to any HART-enabled positioner, existing or new, extending the benefit of the installed asset," adds Micallef.
"A typical plant has 15% control valves, 25% automated on/off valves, and 60% manual valves," notes Dan Carlson, specialist for wireless sales at the Fisher division of Emerson Process Management. "The best solution for control valves is the application of adapters that access local diagnostics in the valve controller, and relay it to remote monitoring systems."
"Ninety percent of users have an annual experience where a manual valve is in the wrong position due to human error—resulting in a bad batch, environmental release or safety incident. WirelessHART manual valve position feedback can be incorporated into digital interlocks, or a WirelessHART on/off controller can upgrade the manual valve to automatic."
"Wireless valve actuators and positioners generally make use of low-power IEEE 802.15.x radios, using a combination of proprietary and open protocols with varying levels of interoperability," says Paul Brooks, business development manager at Rockwell Automation.
Expect to see more and more wireless remote monitoring as time goes on. "Over the coming years, we expect the open standards Wireless HART and ISA100.11a to dominate—allowing a single wireless and asset management solution for instrumentation, actuators and positioners. Don't count out WiFi either. As companies extend their WiFi networks, and as suppliers add WiFi capabilities to their actuators, this technology may become more pervasive," says Brooks.