Why pig a pipeline?
There are various reasons to pig a pipeline, but the most common is to clear the line of debris. This process ensures that the product running through the line is flowing smoothly and reduces the likelihood of product contamination. There also are major safety advantages to clearing a line, as built up debris can degrade the integrity of the pipe wall over time.
Smart pigs also are commonly used today to detect various elements about the pipeline. As mentioned earlier, inspection pigs collect information regarding temperature and pressure, corrosion/metal loss, diameter, bends and curvature to verify pipeline integrity. Cracks, weld defects, surface pitting and areas of crushing/deformation are often measured through pigging as well.
Because of the variety of environments that pipelines are found in, including underground or underwater, and the construction materials of most pipelines, pigs must record their data internally until it can be retrieved by the user. Retrieving and monitoring where certain data was collected5 is done through surface instruments using audible, magnetic or gravimetric methods to record where the pig is at various points. The user then uses this information to map out defects to aid repair crews in maintenance.

Some new, “smart” pigs have GPS capabilities that can assist in mapping a pipeline. This helps maintenance crews save time and money by pin-pointing exactly where is a pipeline is run, instead of having to excavate a large area to reach a specific location in the line.
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