| 摘要 |
In the preferred and illustrated embodiment, an improved pig is set forth. The preferred version includes a body with a hollow cavity filled with foam. The body supports a number of encircling ribs for wiping the inside pipe surface. The internal foam filled cavity is exposed to pipeline pressure which enters through a constricted opening at the rear. In the event of a pressure surge, the fluid enters the pig with a pressure wave front, the pressure wave front being slowly propagated through the foam body. As the retarded pressure wave front moves through the body, the pig has sufficient time to move. Failure to incorporate this retardation of the propagated pressure wave front risks blowing out the nose of the pig.
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