Coal, O&M

“Smart Pigs” Help Ensure Power Plant Gas Line Integrity

Issue 11 and Volume 107.

Last year Kirkland, Wash.-based National Energy Systems Company (NESCO), operator of the gas-fired Sumas 1 cogeneration plant in Whatcom County, Wash., conducted an extremely thorough examination of the 3.7-mile eight-inch gas pipeline that has fed the plant since it went into service in 1993. Owned by Calpine Corp., power generated by the 135 MW plant is bought by Puget Sound Energy for distribution throughout its regional transmission grid. The plant’s heat exhaust generates steam to dry lumber and wood products at the adjacent SOCCO Forest Products facility.

The pipeline integrity test, an example of a company anticipating rather than responding to safety and environmental regulations, was conducted by Houston-based Tuboscope Pipeline Services, Inc., using the latest in “smart pig” technology. Smart pigs, resembling small fireplugs, snake their way through underground pipelines. Some pigs are designed to merely clean the pipes, while others, packed with electronic elements that rival satellites in complexity, can detect miniscule flaws in the pipeline that wouldn’t be visible to the human eye even if a human could see the inside surface.

Tuboscope’s system detected four small out-of-round non-metal loss features in the 19,373-foot pipeline. The largest, at 0.19 inches (2.3% of the pipe inside diameter), barely exceeded equipment minimum reporting threshold criteria (0.17 inches) and proved well within allowable CFR (Code of Federal Regulation) tolerance (0.250 inches for pipes of up to 12-inch diameter). The remaining three losses were below equipment minimum reporting thresholds and typical reporting standards. Even though the variations were within tolerances and typical reporting standards, Sumas technicians pinpointed the section of pipe with the variation, uncovered it and added a failsafe patch.

Although the testing wasn’t legally required for the gas line, Bruce Thompson, senior vice president of Sumas, believes it was the right and prudent thing to do. “We all know that pipelines are the safest means of transporting natural gas,” he said, “but we also know that within the last four years, there have been a variety of local, regional, and national pipeline accidents that have brought the issue of pipeline safety to the public. For this and other reasons, we simply decided to do this test now, rather than later.”

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Joe Rangel of Tuboscope Pipeline Services prepares a smart pig inspection tool during a pipeline test at the Sumas 1 facility in Sumas, Washington. Photo courtesy of Tuboscope Pipeline Services.

Smart pigging provides an environmentally friendly advantage over pressure testing because no water is used or contaminated and there is no prolonged exposure to the inside of pipelines transporting hydrocarbons. Since 1984, the Federal Office of Pipeline Safety has been in charge of monitoring standards for pipeline operators, including the number of pipeline failures, injuries or deaths, and monetary losses. Proposed regulations will mandate two ways to inspect: pressure testing and in-line inspection (ILI). Of those, ILI is the preferred method, as it mitigates the potential for damage to the pipeline and minimizes disruption to daily operations, according to Ron Maurier, director of pipeline assessments for Tuboscope.

According to Maurier, Sumas 1 will realize several immediate benefits from the test. “It’s an integrity benchmark, so that future testing and daily operations will benefit from what has been done. It will allow Sumas 1 to establish a pipeline integrity management process for the future.”

Thompson concedes that such testing carries up-front costs, but believes it is good for business. “We invest in the machinery to protect the environment, respect our neighbors and employees, both for the short-term and the long-term,” he says. “In the process, NESCO and Sumas 1 went out of their way to respect private property and to minimize any disturbances. And the effort paid off from a public relations standpoint, as well.”