'Smart pigs' keep oil pipelines clean

Saturday, August 12, 2006 · Last updated 3:45 p.m. PT

'Smart pigs' keep oil pipelines clean

By KRISTEN HAYS
AP BUSINESS WRITER

photo

Pipeline pigs sit on the shelves at Inline Services Inc., a Houston area-based pig manufacturer and distributor, Thursday, Aug. 10, 2006 in Tomball, Texas. Propelled by pressure, oil or other contents running through the pipeline, the devices that often look like huge dumbbells dislodge debris and clean the pipe walls. The importance of so-called "pigging" leaped to center stage this past week after BP PLC shut down part of the Prudhoe Bay oil field on Alaska's North Slope, raising questions about the integrity of the country's pipelines and how more than 3,000 pipeline operators keep them running. (AP Photo/David J. Phillip)

HOUSTON -- Of all the technologies available to maintain the nation's 2 million miles of pipelines, one of the most critical devices evokes images of a muddy farm animal - the pig.

Now erase the image. The earliest, primitive pipeline pigs may have squealed as they scraped wax, mineral deposits, sand or other corrosion-causing debris from the insides of the nation's energy highways, but even that similarity is long gone.

The importance of so-called "pigging" leaped to center stage this past week after BP PLC shut down part of the Prudhoe Bay oil field on Alaska's North Slope, raising questions about the integrity of the country's pipelines and how more than 3,000 pipeline operators keep them running.

Metal, foam, plastic or gel, ranging in size from a few inches to seven feet tall and wide as a tree - or however big they have to be to fit snugly inside a pipe - some pigs are simple scrapers. Others, known as "porcupine pigs," sport scrubbing wire brushes.

Propelled by the pressure of oil or other contents running through the pipeline, these devices dislodge debris and clean the interior pipe walls.

More sophisticated "smart pigs" carry instruments that gather images and other data inside the pipeline that allow operators to pinpoint trouble spots.

"I've heard so many people say 'If you could make one for arteries, you'd be rich,'" said Gary Smith, president of Inline Services Inc., a Houston-based pig manufacturer and distributor.

BP ordered the Prudhoe Bay shutdown after discovering a leak and severe corrosion in 16 miles of aging "transit" pipes that feed into the 800-mile trans-Alaska pipeline.

The company acknowledged those lines hadn't been pigged in years. Instead, BP had relied mostly on exterior ultrasound to monitor the pipes' integrity, believing the risk of corrosion was low because they carried market-ready crude or processed oil that had been stripped of harmful water, gas, and solids.

BP now says it will use pigs to maintain and inspect all its transit lines.

Even pipes that sit unused will corrode, said Steve Arrington, global operations manager for Houston-based oil services conglomerate Halliburton Co.'s pipeline and process services group.

"Corrosion is just a fact of life. Corrosion of metal alloys occurs all the time. All that man can do is minimize that or reduce it, but we cannot stop it completely," Arrington said.

Legend has it that early pigs, made of stuffed burlap bags or other material, would squeal as they scraped through a pipe, hence the name. But Smith said the name is an acronym for pipeline inspection gauge.

Smith said all kinds of debris can build up in a pipeline, everything from sand left over from fabrication of the pipe to condensation from natural gas to salt water from oil extracted offshore. And even simple bacteria can corrode the metal, he said.

However, many operators resort to pigging only when a problem is apparent. By then the pipe is usually already damaged, which can cause safety and environmental risks as well as jeopardize a multimillion-dollar pipeline.

Regular pigging is good business, said Kirk Langford, head of transmission pipeline inspection for oil services firm Baker Hughes Inc. "The better pipeline operators have always done this."

Other technologies help assess pipe integrity, such as measuring the flow of an electrical current, said Tom Miesner, a Houston-based pipeline consultant. Increased resistance means the pipeline wall is thinning.

However, smart pigging is the ideal, said Miesner, who worked 25 years with Conoco before its merger with Phillips Petroleum.

A five-year study by the Association of Oil Pipe Lines found the use of smart pigs can help reduce pipeline spills. The study, which covered 1999-2004, showed the overall number of spills on pipeline segments tested with smart pigs dropped approximately 50 percent.

"They are about the only thing you can run through a pipe in order to find anomalies," Miesner said.

---

AP Business writer Steve Quinn in Dallas contributed to this report.