A ‘pig’ is a tool that is used to assist in maintaining pipeline integrity. Pigging is the process of running a pig through an in-service pipeline using the flow of product, and can be undertaken for a number of different reasons.

Cleaning pigs are used to clean the internal surface of a pipeline. Over the lifetime of a pipeline, deposits can build up inside, resulting in reduced throughput or blockages. Regular pigging with a cleaning pig can remove these and improve operation. Attachments such as brushes and scrapers can be added to improve the pig's cleaning performance.

‘Intelligent’ or ‘smart’ pigs are used to inspect pipelines for defects, collecting data during their run and providing information to technicians and engineers about the pipeline’s condition. Geometry (or caliper) pigs can also be used for this purpose, determining whether the pipeline has any dents, bends or even if it is corroded via internal surface measurements.

Other functions for pigs include product separation, pipeline dewatering and drying, condensate removal and plugging.

A number of facilities are required for pigging, including pig traps – launching and receiving stations that allow operators to insert and remove pigs without interruption to the pipeline product flow; pig trackers, which allow operators to locate the position of the pigging tools during a pipeline run; and pig signallers, which are installed on a pipeline or pig trap to detect the pig as it passes through.

Some pipelines are considered to be ‘unpiggable’, which means they cannot be inspected by conventional intelligent pigs. This could be due to a number of reasons, including multiple pipeline diameters, valve restrictions or sharp radius bends. Over the years, innovative technology and techniques have been developed to counter this problem, with a range of products now available to inspect even the most difficult pipelines.

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