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Emerson Smart Wireless technology is being used to help monitor a natural gas pipeline transmission system, as part of an upgrade to Bord Gais above-ground installations (AGIs) in Ireland.

One such site was at Middleton, near Cork, where a number of instruments needed to be upgraded with the latest temperature and pressure transmitters.

The Middleton site is quite unusual as it is divided by a road.

Although cable ducting was already in place and could have been reused, this facility presented an application to test wireless technology with a view to installing wireless at other AGIs.

For the upgrade at Middleton, wireless promised to be lower-cost, offered faster installation and start-up, as well as easy integration into the existing RTUs using Modbus serial communications.

Although there is minimal traffic on the road dividing the Middleton facility, Bord Gais could not use a line- of-sight wireless system as the signal could be interrupted by passing cars.

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 rerouted 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.

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 potentially explosive zones, regular checks on cable integrity are required, as well as on 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.

At Middleton, Rosemount wireless transmitters include five measuring pressure, one differential pressure and one temperature; all transmitters have been 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 Gais AGIs, and the Smart Wireless gateway is positioned in the instrumentation kiosk, 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,’ said Brid Sheehan, communication and instrumentation engineer, Bord Gais.

Emerson Process Management – Wireless

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