Polyurethane And Pipeline Pigs Make A Perfect Match

Pigs have been squealing in pipelines for decades. A lot has changed, however, since the first modern-day pipeline pigs were introduced in the early 1940s. Many would cite the development in recent years of smart pigs, also called inline inspection (ILI) tools, as the biggest change. These pigs, which use sensors and computers to accurately inspect and analyze pipeline conditions and problems, do represent a vital improvement in the technology.

But you might not realize that a lesser-known breakthrough has made all that possible: the introduction of cast polyurethane as a material for manufacturing pipeline pigs. Let us take a look at how cast polyurethane has helped revolutionize the pipeline pig industry through the years.

The Original Pigs
Although various makeshift instruments had been used to clean pipelines for many years, the first iteration of what today would be called a pig wasn’t developed until 1942 when the War Emergency Pipeline System was built in the United States in response to an urgent wartime need for huge quantities of oil and gasoline on the East Coast to supply that area and the armed forces in Europe.

The 20- and 24-inch pipelines were the first of these large sizes. T.D. Williamson, Inc. (TDW), which today is a global leader in pipeline equipment and services, developed a pipeline scraper capable of effectively removing debris and contaminants in the large-diameter piping system. These original pigs had leather cups, but TDW quickly transitioned to neoprene and nitrile rubber materials. The next big material transition would occur more than 20 years later.

The Trouble With Rubber
After World War II, oil and gas companies around the world accelerated construction of pipelines of widely varied sizes, carrying an increasingly diverse array of materials. Meanwhile, pipeline velocities increased dramatically.

Under these more severe conditions and demands, the pigs’ rubber cups, scrapers and blades began to show too much wear and tear on the job. In many cases, the pigs broke apart before going the full distance and completing their tasks between the launcher and the receiver. In addition, different products in the lines—particularly hydrocarbons—proved to be too harsh for the rubber materials. Pipeline companies and their suppliers knew they needed something tougher to handle the job.
Researching A New Material

In the early 1960s, engineers at TDW embarked on several years of internal research and development at their Tulsa, OK headquarters to find a new material with greater durability and chemical resistance.

Their focus? Cast polyurethane, one of the world’s most versatile, durable raw materials. Polyurethane can be formulated for superior load-bearing capability, abrasion resistance and impact absorption. TDW engineers tried many different polyurethane formulations and tested them with various in-house techniques including a rolling drum covered with sand paper, to simulate the pipeline environment. Their work ultimately produced the first polyurethane pig components: scraper cups and blades.