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.
There are three types of technologies we frequently use on a Smart-PIG and each provides unique data about the pipeline.
Getting the PIGs through the pipelines works a little differently in liquids and gas pipelines. Both pipelines have launchers and receivers installed, like a T off the main pipeline. These sections are slightly larger than the size of the pipeline, which can range from 4” to 48”. This allows the inspection teams to load or remove the PIGs safely. Once the PIG is in the barrel of the launcher, the cup at the front of the tool is snugged against the diameter of the pipeline and the flow of oil or gas is controlled to move the PIG along the pipe and provide accurate readings during the run.
In a gas pipeline, the cups act like a sail on a sailboat catching the wind in its sails. The natural gas flows through the pipeline, catching in the cup and pushing the PIG along. The speed can be controlled by controlling the speed of gas in the pipeline, or by opening in the middle of the cup to allow some of the gas to flow through.
Since oil is not compressible like gas, the tool has to run at the speed of the liquid in the line. The cup is sealed against the sides of the pipe and gets pushed along, like riding an underwater current.
"We do these in-line inspections periodically and it gives us an overall health of the pipeline.”
Jon Sadler, Manager of In-line Inspection Canada at TransCanada
Jon Sadler, Manager of In-line Inspection Canada at TransCanada, has been working with these tools and running in-line inspections for 15 years and compares it to getting a regular check-up from your doctor.
“We do these in-line inspections periodically and it gives us an overall health of the pipeline.” Sadler explains.
“Ideally it tells us our pipeline is in really good shape, but if we find something unexpected we know where it is and why and we can take preventative measures so we can keep supplying energy to our customers.”
For more information about PIGs or in-line inspection watch the full-length videos from our PIG suppliers or read our other stories:
There are thousands of shut-off valves along TransCanada's pipelines. Here's how they work.
The International Energy Agency (IEA) predicts a 31 percent increase in global energy consumption by 2040.