The pig, or “Pipeline Integrity Gauge,” is a sophisticated device that is critical to the safety and integrity of pipelines. The oil and gas pipeline transportation industry can’t live without them. They help ensure the safe and efficient passage of crude oil, NGLs, petroleum products and natural gas through more than 2.3 million miles of pipeline in the U.S, according to PHMSA (Pipeline and Hazardous Materials Safety Administration). Over 3,000 pipeline operators in the U.S. manage this transport system. Their success is due in large part to pigs. Today we investigate the role of pigs in oil and gas pipeline transportation infrastructure.
College football season has started once again, but we want to be clear that today’s blog is not about the Arkansas Razorbacks or the “pig” they throw around. It’s about another kind of “pig,” one that is critically important to the oil and gas pipeline industry. This kind of Pig can cost over $500,000 and it does its work inside pipelines.
Pigs help keep pipelines round, clean and blemish free
There are lots of stories out there about why these contraptions are called “pigs”. One, that seems logical, is the fact that “pig” is an acronym for “Pipeline Inspection Gauge”, or “Pipeline Integrity Gauge.” But maybe they got their name from the squealing sound they make when traveling through a pipeline or the fact that after traveling through a pipe they look like a pig, covered in muck? Another story is how in the late 1800’s balls of pig leather (and other things) were used to clean pipes (which were then made from wood). No one really knows for sure.
What we do know is that pigs performed over 50,000 pipeline inspections in 2012 alone - along nearly 90,000 miles of pipe, according to PHMSA. There are many different kinds of pigs but they are used in pipelines for three main reasons:
1. Cleaning —better flow, more throughput, efficiency, corrosion control
2. Batching and Separation —separating product batches such as diesel and gasoline to keep them from mixing
3. Inspection —safe product flow and mapping
Pigs come in all shapes and sizes (Figure 1). There are simple pigs (sometimes called “dumb” pigs), and there are complex high tech pigs (a.k.a “smart” pigs). The more sophisticated smart pigs are used as in-line inspection tools. Smart pigs are typically owned and operated by specialty services companies. Dumb pigs are typically used by pipeline operators for cleaning and batching.
Figure 1: TD Williamson Pigs (Click to Enlarge)
Pigs can be metal, foam, plastic or gel and can have special add-ons like “scrubbers.” Their length can range from a few inches to over seven feet long, and whatever width it takes to fit (generally “snugly”) inside a pipe. Sometimes they look like dumbbells and sometimes porcupines. They move through pipelines propelled by added pressure from pipeline compressors or pushed by whatever product is in the pipeline. Pigs are launched into the pipeline at an injection location, such as a valve or pump station (from as you may have guessed, a “pig launcher”) and directed by the flow of the product in the pipeline until they reach the end of the testing or cleaning area. At the end of the line, pigs are removed into a receiver (or “pig trap”). If the pig is smart, the tool is removed, and the recorded data is collected and analyzed.
Smart pigs were developed in the 1960’s and provide “intelligence” by recording data inside the pipeline (Figure 2). The data collected might include measuring the level of damage and/or corrosion, or mapping an entire pipeline system for asset management purposes. New technology makes them even “smarter”. Pigs can now employ a variety of technologies like Magnetic Flux Leakage (MFL) and Global Positioning Systems (GPS) to record data about the condition of the pipeline. For example, if there’s a dent in the pipe wall, its exact quadrant and coordinate can be pin pointed. But the value of that data still has to be extracted by analysis. And smart pigs generate myriads of data – that is only useful if it is properly interpreted.