Pigging & Pressure Testing
Pigging operations are often used as an aid to pressure testing, where the pigs are used to remove air from the system which would otherwise cause pressure fluctuations resulting in an unsatisfactory test. They are also used to flush and clean pipelines removing both debris and mill scale or corrosion deposits from the internal surface of the pipe. They are further used to check the profile of the pipeline to ensure that the internal weld profile is satisfactory and that during backfill, there has been no damage to the pipeline.
Pressure testing is the final test stage prior to the commissioning or reinstatement of a system. Individual valves, spools, skids, complete modular system or pipeline can be pressure tested. This final proof testing is normally performed between 1.1 to 1.5 design pressure of the system, and various test mediums are employed including liquid and gas.