摘要 |
Methods for releasably plugging off a section of a pipe line and apparatuses for practicing or carrying out the methods are disclosed. An apparatus comprises one or more pigs, each pig having an inflatable ring therearound, inert gas therein for inflating the ring, and a remote command signal receiver for initiation of expansion of the pigs responsive to a remote command signal generator at the pipe section to be sealed off for sealing the pigs in the pipe as they reach their respective pipe section termini. The remote command signals may comprise sonic or ultrasonic energy.
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