What Does Pigging Mean?
Pigging is a method for inspecting pipelines for internal damage and other issues. It is also used to clean and maintain pipelines. In either case, it can be completed without interrupting the flow of product in the pipe.
Pigging involves sending a device known as a pig through the piping. The pig then moves with the flow of the liquid or gas carried by the pipe. Pigs used for inspection are fitted with a small computer that collects, stores, and transmits data along its journey.
Most pigs use the magnetic flux leakage (MFL) method, while others use ultrasonic and other methods to perform the inspection. Remote visual inspection using cameras mounted on robotic crawlers can also be used to carry out nondestructive testing (NDT).
Safeopedia Explains Pigging
Pipeline pigging is used to inspect the condition of pipelines from the inside, revealing issues like corrosion or cracking. Based on the data collected by the pig, pipes that show signs of damage can be identified and either repaired or replaced.
Pigging can also be used to clean pipelines as part of regular maintenance procedures. Unlike those used for inspection, pigs designed to clear away debris, remove rust, or get rid of mineral buildup are not equipped with sensors and other measuring instruments.
To begin the process, the pig is inserted into the pipe using a pig trap. Then a pressurized flow is applied behind the pig to propel it forward. A second trap is set at the exit of the pipe to collect the pig once it has completed its run.
Unibody Pigging and Poly Foam Pigging
The two types of pig that are commonly used are the unibody pig and the poly foam pig.
These are single-body polyurethane pigs mainly used to remove liquid from wet gas systems, spearate refined products, and control the buildup of paraffin.
They are sturdier than poly foam pigs, with a multi-disc configuration that can be used for different purposes such as removing liquids, controlling buildup, and pipeline commissioning. Unibody pigs are designed to maneuver in less than 1.5 diameter radius ells and bends and can be equipped with wire brushes.
Poly Foam Pig
These pigs are made of open-cell polyurethane foam and can be used for sealing and lightly removing abrasion. They can navigate short bends, ells, tees, miter bends, and port valves. Their flexibility allows them to have a smaller diameter.
Poly foam pigs can be outfitted with a nose pull role, transmitter cavity, or wire strip brush to increase their functionality.