New system pinpoints leaks in ethylene pipeline

A model-based leak detection, PLDS, developed by Modisette Associates, Inc., Houston has been operating on the Solvay et Cie ethylene pipeline since 1989. The 6-in. pipeline extends from Antwerp to Jemeppe sur Sambre, a distance of 73.5 miles and is buried at a depth of 3 ft. with no insulation. Except for outlets to flares, located every 6 miles for test purposes, there are no injections or deliveries along the pipeline. Also, there are block valves, which are normally open, at each flare location. This paper reviews the design and testing procedures used to determine the system performance. These tests showed that the leak system was fully operational and no false alarms were caused by abrupt changes in inlet/outlet flows of the pipeline. It was confirmed that leaks larger than 2 tonnes/hr. (40 bbl/hr) are quickly detected and accurately located. Also, maximum leak detection sensitivity is 1 tonne/hr. (20 bbl/hr) with a detection time of one hour. Significant operational, configuration, and programming issues also were found during the testing program. Data showed that temperature simulations needed re-examining for improvement since accurate temperature measurements are important. This is especially true for ethylene since its density depends largely on temperature. Another findingmore » showed the averaging period of 4 hrs. was too long and a 1 to 2 hr. interval was better.« less