Why must the pig’s diameter be larger than that of the pipeline?
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The main function of a pig is to insert and remove balls. The diameter of the ball is the same as that of the pipeline; why is the diameter of the pig slightly larger? How is it generally determined how much to amplify? Could those who know please explain it? Thank you.
My personal understanding: In a pipeline, the pig ball should have an interference fit; that is, its outer diameter before compression must be larger than the inner diameter of the pipeline, otherwise it will not be able to perform its function of cleaning the pipeline. When releasing the ball, its outer diameter is the same as or slightly larger than the inner diameter of the pig, which makes it easier to place it in position; then, by applying pressure, the ball is deformed and forced into the pipeline ； When retrieving the ball, if its outer diameter is still larger than the inner diameter of the pig, it is difficult to retrieve it. Moreover, if energy builds up, it could cause an explosion that might injure people.
The analysis done by the senior up there is completely correct