COMMUNICATIONS/TELEMETRY 37
could not use a line of sight wireless solution as the signal may be interrupted by passing cars, affecting the reliability of communications. With Emerson’s self-organising Smart Wireless technology, each measurement point has a redundant communication to the RTU via two or three routes. Wireless devices can act as a router for other nearby devices, passing messages along until they reach their destination. If there is an obstruction, transmissions are simply re-routed along the network until a clear path to the Smart Wireless Gateway is found. As conditions change or new obstacles are
encountered in a plant, such as temporary scaffolding, new equipment, or a parked construction trailer, these wireless networks simply reorganise and find a way to get their signals through (Fig. 1). All of this happens automatically, without any involvement by the user, providing redundant communication paths and better reliability than direct, line-of-sight communications between individual devices and a receiver. This self-organising technology optimises data reliability while minimising power consumption. It also reduces the effort and infrastructure necessary to set up a successful wireless network.
Because cabling enters into potentially explosive
zones, regular checks are required of cable integrity as well as the condition of the EX barriers. This is
especially important for older sites where there can be an aging cabling infrastructure. Wireless removes such concerns and reduces the number of site inspections needed. Bord Gáis was very familiar with Emerson’s Rosemount pressure transmitters and was confident that Emerson’s Smart Wireless technology would work well for this application. Having tested a number of devices on a work bench, they had no hesitation in applying the technology to the Middleton facility. At Middleton, Rosemount wireless transmitters include five measuring pressure, one differential pressure, and one temperature; all transmitters have been successfully installed and are sending measurements back to the control room via the RTU. The devices are placed in enclosures, standard practice for all instrumentation used at Bord Gáis AGI’s, and the Smart Wireless Gateway is positioned within the instrumentation kiosk, which is effectively a ‘walk in’ enclosure. “We found that the enclosures do not interfere with the signals at all. We tested a few devices that were positioned furthest away from the gateway and these worked without any problems so we proceeded to install the rest of the transmitters,” explained Brid Sheehan, communication and instrumentation engineer, Bord Gáis. Reliability of the wireless signal has not been an issue, she said. o
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