Pipeline Proving and Gauging
Pipeline proving is essential for pipelines with no previous pigging history, or when there are doubts as to the internal pipeline condition. The purpose of proving is to simply confirm whether or not a pig can traverse the pipeline from the launcher to the receiver.
Very often a Foam Pig or Polly Pig is used for pipeline proving. Manufactured from open cell polyurethane foam and available in soft, medium and heavy densities, these pigs can be supplied as bare foam or with a coating of polyurethane. A gauging plate can be fitted and depending on size, a transmitter can be fitted in a cavity within the pig body for pig location purposes. If pig tracking and pig detection is required, then magnets can also be fitted.
Depending on the type and density of Polly Pig, it should offer minimal cleaning capability to allow for the easiest passage through the pipeline. Due to their flexibility, Foam Pigs can also pass through some restrictions of up to 50% and can readily negotiate tight radius 90 degree bends. To prevent the pig from negotiating the receiver off-take line and entering downstream facilities, it is usually recommended that a pig receiving sleeve or pig stopper is fitted to the pig receiver.
Pipeline gauging detects any internal restrictions and gives indicative results as to whether the pipeline is geometrically suitable for the progression to more aggressive cleaning pigs. Gauging is achieved by fitting a pig with an aluminium plate, sized proportionally to the minimum internal diameter of the pipeline.
Steel bodied pigs such as a Bi-Directional Pig or Flexi-Cupped Gauging Pig are often used for pipeline gauging. These pigs are fitted with a combination of polyurethane guide discs and seal discs or cups. Depending on pipeline diameter, transmitters and magnets can usually be fitted for pig tracking and pig location purposes.
Whilst these pugs should offer only light cleaning, they should be fitted with pluggable by-pass ports to front of the pig body to help flush any accumulated debris ahead of the pig.