ABSTRACT:

Distributed fibre optic sensors can be used to provide effective leak detection and condition monitoring of pipelines and vessels and have the capability to pinpoint the exact location of the leak or potential weak spot to within 1m of the event. Each system can provide coverage of more than 60km of pipelines, providing a cost effective method for monitoring long pipelines and providing full coverage of refineries. The principle of leak detection is based on the principle that distributed fibre optic sensors are able to detect the leak through the measurement of temperature or strain in the surrounding environment of the pipeline. A distributed strain measurement is able to monitor movements of the pipeline, which can be critical in areas of seismic activity, and take action before there is structural damage to the pipe itself. In the event of a leak occurring on the pipeline, the leaking gas or liquid effluent will carry a distinct temperature signature which will differ from the surrounding environment. The distributed fibre optic sensors are able to measure temperature changes as small as 0.01°C and so can detect large temperature changes caused by leaks of gas or LNG, or more subtle changes in temperature caused by chemicals, water or oil. The distributed fibre optics sensors are installed along the length of the pipeline, usually during pipeline construction. What is unique about distributed sensing technology is that the fibre optic cable itself is the sensor and the instruments can take measurements at intervals every 1m along the entire length of the sensing fibre, providing continuous total coverage of the pipeline

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