Wireless transmitters monitor gas transmission pipeline system in Ireland

29 April 2009

Emerson’s Smart Wireless technology is being used to help monitor an expansive natural gas pipeline transmission system as part of an upgrade to Bord Gáis’ Above Ground Installations in Ireland.

Bord Gáis’ Above Ground Installation at Middleton near Cork, in Ireland

Rosemount wireless devices have replaced aging hard wired devices as part of a trial to decide the future ‘specification’ of such sites going forward and for other sites that are due upgrades.

Bord Gáis is a leading Irish energy provider, wholly owned by the Government of Ireland that is responsible for the supply, transmission and distribution of natural gas to over 600,000 customers. Management of the gas pipeline system is a sophisticated 24-hour operation involving constant monitoring through Supervisory Control and Data Acquisition (SCADA) systems. Gas is transmitted at high pressure, around 60 - 80 bar from its main facilities and then at remotely located Above Ground Installations (AGIs) it is reduced appropriately to supply regional distribution points and commercial customers. Bord Gáis has in excess of 200 AGIs throughout Ireland, and at all these sites the gas lines in and out are monitored.
Existing AGI’s have between three and twelve pressure transmitters measuring both inlet and outlet pressure. The cooling effect as a result of pressure reduction is also measured using temperature transmitters. These devices are connected, by hardwiring, to an onsite Remote Terminal Unit (RTU) that transmits data back to a SCADA system Master Terminal Unit at the central monitoring station in Cork. Should thresholds be exceeded to pressure or temperature, alarms are activated.

Bord Gáis’ Mains Renewal Programme aims to ensure that the Irish natural gas facility is one of the most modern pipeline systems in Europe. As part of the process, existing AGIs reaching the end of their lifespan are being upgraded with the latest instrumentation. One such site was at Middleton, near Cork, where a number of instruments needed to be upgraded with the latest temperature and pressure transmitters.
When Bord Gáis looked to upgrade the facility with new instrumentation, it was decided to use a network of wireless pressure and temperature transmitters. The Middleton site is quite unusual as it is divided by a road. Although cable ducting was already in place and this could have been reused, this facility presented an excellent application to test wireless technology with a view to installing wireless at other AGI’s.

“Having adopted GPRS (General Packet Radio Service) as a `back up’ communications technology for our RTUs we were very comfortable with wireless,” said Frank Smiddy, Communication & Instrumentation Engineer, Bord Gáis. “We like to think that we are very forward thinking and open to new ideas and we are always looking to improve our service using the latest technology.”

Whenever AGI’s are installed to support extensions to the pipeline system, or existing sites are upgraded, Bord Gáis is continually looking to minimise any installation costs. Power and data cabling are usually installed in ducting at the AGI’s. However burying cables can prove to be costly and time consuming. 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 Gáis could not use a line of sight wireless solution as the signal may be interrupted by passing cars affecting the reliability of the 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.

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.

“Emerson’s Smart Wireless technology is ideal for site upgrades where instruments and cabling can be up to 25 years old and in need of replacing,” said Smiddy. “Installing the transmitters is very simple as the wireless devices simply replace the existing analogue devices and these then connect back to a gateway that we installed within the existing instrumentation kiosk.”