Wireless technology removes the physical and economic barriers associated with wired gas detection devices. It can save up to 90 percent of installed cost and time and can be applied in both field and plant networks, detecting leaks that might not otherwise be detected by sparsely distributed wired units. Just about any type of wired sensing technology can be adapted for wireless and some incorporate multiple capabilities, combining both IR and electrochemical for example. At the sensor level, there is little difference in the basic technology deployed between a wired and a wireless gas detector.
However, using sensors designed for wired gas detectors in a true wireless (no power and signal wires) application, would be impractical as batteries would require replacement in months instead of years. Figure 1 shows the exterior of a wireless gas detector with all of the built in protections necessary for deployment in inside and outside hazardous area locations. It shows the antenna by which it communicates with its host. The housing should be rated Class 1 Div 1 explosion proof, and there should be a graphic display that shows gas concentration, network, calibration, temperature and battery status. Accessible field connection points should be rated intrinsically safe for Zone 1, allowing connection to a hand-held communicator for configuration and testing as well as for swapping out sensor types without a hot permit.
Once the sensor takes the measurement, the wireless devices send signals to a wireless
gateway which can be connected to a fire &gas control system, distributed control systems (DCS) or programmable logic controller (PLC) host for processing. The wireless signals may be designed using any network protocol, although, as will be discussed later, standard open protocols such as Wireless HART have specific advantages.
In our next post, we will explore the applications of the wireless device. Stay tuned!
by: Wil Chin, Vice President of Marketing and Business Development at United Electric Controls
Joe Mancini, Senior Product Manager at United Electric Controls
Greg LaFramboise, Retired Wireless Technology Lead, Chevron