What is a PIG?

Every industry has its share of TLAs (three letter acronyms) that can be confusing outside of the workplace. The pipeline business is no exception. One TLA that frequently pops up in operating pipelines is the PIG. No, it isn’t a cute barnyard animal, pot-bellied pet, or potential dinner menu option. A PIG is a pipeline inspection gauge, and it is a critical part of keeping our pipelines operating safely. 

There are several different PIGs in the in-line inspection toolbox and each performs a different function. Smart-pigs are data capturing tools that provide readings and information on the health of our pipelines, but before they can get accurate readings, a cleaning tool, affectionately known as a ‘dumb-pig’, goes through the pipeline, cleaning the steel so the Smart-PIGs sensors can get a clear and accurate reading.

Once the cleaning tool has cleared the pipe of debris and checked for any possible obstructions, the Smart-PIGs can be sent through to provide valuable information and locations for potential metal loss, disbonded coating and small cracks or dents in the steel.

Three little pigs

There are three types of technologies we frequently use on a Smart-PIG and each provides unique data about the pipeline.

1. Magnetic Flux Leakage (MFL): This technology creates a strong magnetic field in the steel of the pipe, through magnets located circumferentially around the PIG. There are sensors located between the magnets that record any disturbance in the magnetic field, which indicates metal loss. The sensors measure where and how much magnetic field is lost, providing a picture of the thickness of the steel around the pipe.
   
   
2. A caliper tool: This technology suspends little ‘fingers’ on springs that feel along the inside of the pipe looking for dents. If there is a depression in the pipe, the fingers are pushed down for the length of the dent and spring back up after it. Dents on the top of a pipe could occur from third-party digging, while dents on the bottom are likely caused by the pipe resting on a large rock or boulder over time. The caliper tool provides an exact location so the cause can be addressed and the steel repaired. This technology is often used with the MFL technology.
   
   
3. Electromagnetic Acoustic Transducer (EMAT):  This technology looks for small cracks in the pipe. It works like sonar and creates sonic waves within the steel. When the wave hits a crack, the sound wave is reflected back and the technology records those reflections to tell us where there could be cracks or crack colonies. This is the newest technology used by in-line inspection teams.