Pipeline Pigging

            A pipeline inspection gauge, commonly referred to as a ‘pig’, is a device used to clean and/or inspect a pipeline. The term originates from the initial pig devices, which were bundles of straw wrapped with wire or leather that were forced down the pipeline, resulting in a squealing sound. The term ‘pipeline inspection gauge’ is a backronym and helps to accurately represent the increased capabilities of these devices.

               The spherical or cylindrical devices manufactured today vary greatly in construction material, size, color and accessory components. Common to all pigs, though, is that they closely conform in diameter to the pipe bore. This allows the device to knock away any accumulated debris or material and to closely inspect for cracks or flaws in the pipe.

               There are a variety of types of pigs used today, including:

1.      Utility pigs                 : used to clear the line of debris or seal the line

2.  Inspection pigs    : used to gather information about the pipeline, which can include temperature and pressure, corrosion/metal loss, diameter, bends and curvature.

3.     Specialty pigs           : one example of a specialty pig is a plug, used to block off a line so that maintenance can be performed

4.    Gel pigs                  : gelled liquids that can be used alone or in conjunction with other types of pigs for various procedures including debris removal, hydrostatic testing, product separation, dewatering, condensate removal, removing a stuck pig and more

This video show how pig works : https://www.youtube.com/watch?v=KMoCbqOT7yU

             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.

source:https://www.c-a-m.com/products-and-services/valves/valve-academy/how-does-it- work-pipeline-pigging