Feasibility Tests of Pipeline Pigs for Cryogenic Pipelines

摘要

The cryogenic pig experiment reported here was designed to test the concept of using a pneumatically driven pipeline pig to force cryogenic fluid through a long, large-diameter pipe, which is one of the key features of the proposed large-scale Spill Safety Test Facility. The Spill Safety Test Facility will spill materials such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), ammonia, and other liquefied gases under controlled conditions so that atmospheric dispersion of these materials can be better understood. Three pig design concepts were tested: (1) commercially available, bullet-shaped polyurethane foam pigs, (2) close-fitting spherical metal pigs with sufficient clearance to pass through the pipe at cryogenic temperatures. Three different sizes were tested to determine the effect of a loose fit, and (3) cylindrical metal pigs with flexible wipers at each end which would maintain a seal during transit through the pipe. The most effective pigs in removing liquid from the pipe were the polyurethane foam pig and the cylindrical wiper pig. For the LN sub 2 tests these two pigs left no liquid in the pipe, and for the water tests they left 1% of pipe volume. The large sphere was the next best pig, leaving 2 to 3% of pipe volume during the LN sub 2 tests and about 3% of pipe volume during the water tests. (ERA citation 08:047043)