This shows how one of the "pigs" fits into the pipe. Pig is an acronym for "pipeline inspection gauges". This improves the flow of oil through the pipeline and monitors its condition. Pigs are launched and retrieved at pump stations and travel through the pipeline with the moving oil. The orange polyurethane sample here is a cleaning and flow improvement pig. Other more sophisticated pigs use magnetic fields and ultrasonic signals to detect small changes in the pipe's wall thickness and shape. Pigs are among the most important tools available for protecting the pipeline and detecting potential problems.