Given the vast quantities of oil and gas liquids that travel pipelines daily, minimizing and eliminating any risk due to defect or damage is an important part of pipeline operations. While external inspection is a big part of monitoring a pipeline, wear and tear happens internally and requires cleaning and inspection on an ongoing basis. Companies perform internal inspection through a process known as ‘pigging’.
Pipeline inspection gauges, or ‘pigs’, were developed originally to clean and scrape pipeline to cut rust and other deposits off the inside of the pipe. More sophisticated pigs, known as ‘smart pigs’, were developed for in-line inspection with the first smart pig run by Shell in 1961. Smart pigs use various electronics and sensors including magnetic field recorders and ultrasound to detect defects. Less advanced pigs known as ‘caliper pigs’ test for major deformities by measuring the internal diameter of a pipeline, and are often used first to make sure a smart pig can travel a pipeline without being damaged or getting stuck.
Smart pigs carry on-board recording devices to collect data on the condition of a pipeline including the existence, location and severity of any defects. External sensors track pigs as they move through a pipeline and that data is correlated with the positional and pipeline evaluation datasets collected by the device to provide a location-specific defect map. The information is collected and used for ongoing monitoring, and to determine maintenance and repair schedules so as to minimize and eliminate safety and environmental risks.
Pigs are loaded into a ‘pig launcher’ (or ‘launching station’) and are pushed through the pipeline by the pressure driven flow of the product until it reaches the ‘pig catcher’ (or ‘receiving station’). Pigs were originally designed to travel large-diameter pipelines but through advancements in technology have been miniaturized and can now travel smaller pipelines that measure 20 centimeters or less in diameter.
Where did the name ‘pig’ actually come from? It isn’t just an acronym. According to some people, the first of these devices that were straw wrapped in wire actually made a squealing noise as it moved through a pipeline.
Pipeline inspection gauges (or ‘pigs’) have been featured in three James Bond films: Diamonds Are Forever, where Bond disabled a pig to escape from a pipeline, The Living Daylights, where a pig device was used to get someone through the Iron Curtain, and The World Is Not Enough, where a pig was used to move a weapon of mass destruction through a pipeline. (Source: Wikipedia)
To find out more about pipeline safety and integrity including pigging, visit the Canadian Energy Pipeline Association (CEPA).