Pigging Of Oil & Gas Pipelines

“PIGGING” is a term used to describe the process of driving a purpose-built device through a pipeline to clean, inspect or measure certain parameters of the pipeline. The name “Pigging” is derived from the squealing noise, characteristic of pigs, emitted when the device passes through the pipeline.

Pipeline pigs exist in two fundamental groups: CONVENTIONAL PIGS which perform functions such as cleaning and dewatering and INTELLIGENT PIGS which provide information about the condition of pipelines. Conventional pigs are deployed at various stages during the life of a pipeline. Depending on regulation requirements, pipelines may be pigged during the construction phase, during the operations phase and/or at special occasions in the life of a pipeline. Given the fact that pipelines are the primary means by which crude oil, gas and refined petroleum products are transported from one location to another, the subject of pigging of   pipelines is yet another critical function in the value chain of Oil & Gas Industry activities.

During pipeline construction, pigging is effected for various reasons which include debris removal, gauging to detect dents and buckles, cleaning to remove mill scale and add corrosion inhibitors, flooding prior to hydro-testing, and dewatering to displace water. Especially for gas pipelines, water in pipelines may combine with the gas to form hydrates and waxy solids which could block the lines. Debris and dirt in newly constructed pipelines could cause havoc by blocking filters, damaging pump impellers and jamming valves open or shut.

During operations, pipelines are pigged for product separation, wax removal, line cleaning, condensate clearance, corrosion inhibition and meter proving. To successfully execute pigging during operations, pipelines have to be designed and built with pig launchers and receivers.

Specialist applications of pipeline pigging arise when there is a need to accurately determine the present state of pipelines. In such instances, dents, buckets, pitting and cracks are detected using intelligent pigs, which use the principles of magnetic flux leakage or ultrasonic reflection to take measurements. The gathered data is stored and interpreted using appropriate computer software. Pigging systems also find special application in painting the internal bore of pipelines and in the installation of retrievable subsea safety valves.

Intelligent pigs vary in complexity with the manufacturer and are often very different and specialized, that without exception, they are not sold by their manufacturers, but are used to carry out inspection on behalf of operators.

Intelligent pigging of pipelines is critical to guaranty safety of lives, protect the environment, and improve pipeline asset utilization, especially with the plan to make more use of gas in the domestic economy through the gas master plan project. To this end, pipeline operators and regulators should review relevant codes of practice to establish a reliable and cost effective inspection program in conjunction with pipe manufacturers.

Local organizations and individuals wishing to join the local content train will also find value in this segment of the service industry.

Source : Guardian