UK’s National Grid selects monitoring system for LNG line

A bespoke DTS system designed by the company has been installed at the terminal, providing 82 sensing elements that are attached to the top and bottom surfaces of the pipe. The pipeline forms part of the first phase of the development of the LNG terminal, which was opened earlier this year as part of National Grid’s development project and å£130 million of initial investment.

In addition to continuous temperature monitoring, the system has already successfully monitored the preliminary process of cooling along the pipeline, which must be done prior to the first transportation of the LNG to reduce stress and damage on the pipes. In order to maintain the pipes at a crucial temperature of -161oC, when natural gas becomes liquid, small amounts of LNG are flushed through the pipes. The whole cooling process was carried out over four days, ending with a successful first LNG shipment of 138,000cum transported through the line from ship to storage tanks on the shore.

“With Sensa’s DTS system we are able to pinpoint a temperature anomaly to the nearest metre in the pipeline, so that if there is a detected leak we can locate and repair any problems quickly and without causing further damage”, said Ian Belmore, Site Manager at National Grid’s Grain LNG facility. “Work has now commenced on the second phase of this project, which will triple the size of the facility and the volume of LNG processed.”

Sensa’s DTS solution uses fibre-optics to provide real-time data regarding temperature measurements at many thousands of individual points across the surface of the tanks or pipelines for distances up to 30km using a single fibre. A potential LNG leak would be highlighted as a cold spot on a temperature trace, as the freezing LNG seeps from the lagged inner pipeline into an outer pipe.

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