Pigging in pipeline maintenance is the practice of using a pipeline inspector or "pigger" to perform various operations on a pipeline without stopping the flow of product in the pipeline. Pigs are named for the squealing sound they make as they move through a pipe. These operations include but are not limited to, pipe cleaning and inspection. This is accomplished by inserting the pipe cleaner into the pipe cleaner transmitter (the funnel-shaped Y-shaped portion of the pipe). The launcher is then closed and the pressure of the product in the pipe is used to push it down the pipe until it reaches the receiving trap - the "pig catcher".

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