| 摘要 |
A collapsible pig attached to the end of a tubing and having a seal to the bore of a pipeline for pulling the tubing into the pipeline at up to a predetermined pressure differential across the seal and while allowing the fluid in front of the pig to flow into the end of the tubing without pressure restriction, alternately having reversed flow from within the tubing exit the end of the tubing through jetting nozzles, and having the seal collapse at a pressure differential higher than the predetermined pressure differential.
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