Metal Piece Missing in Alaska Pipeline

ANCHORAGE, Alaska -- Operators of the trans-Alaska pipeline hope a scraping device will push out a piece of metal 20 inches in diameter that's been missing in the pipeline since December.

A pipeline cleaning device known as a scraper or paraffin pig broke apart inside the pipeline in December between pump stations just north of Fairbanks and near Delta Junction about 100 miles to the south.

Most of the pieces have been recovered but a stainless steel ring that holds other pieces in place has not been found.

Mike Heatwole, spokesman for Alyeska Pipeline Service Co., which operates the 800-mile pipeline, downplayed the risk. An Alyeska engineer described it as losing the pop top off of a soda can down the drain of a house, Heatwole said.

"From our view, there's no integrity risk associated with this," he said Saturday. "It's a concern, yes. We'd like to locate it."

In the worst-case scenario, the missing piece of metal could interfere with a check valve that stops the flow of oil in the case of a leak, but Heatwole said the probability of that happening was low.

Over time, wax builds up on pipeline's 48-inch diameter walls, slowing flow. Alyeska inserts paraffin pigs _ a sort of tube with fins _ inside the pipe to scrape the walls of the pipe about every seven to 14 days.

Scraper pigs pushed along by the flow of oil are designed to come apart if they encounter obstacles so that the pipeline will not be plugged.

After the scraper pig broke apart, Alyeska sent another one in. It pushed out 40 barrels of wax and most remnants of the broken pig.

A more aggressive cleaning tool was working its way through the line and was expected in Valdez, the pipeline terminus, on Saturday night. Alyeska officials hope the missing ring will be there _ if not, they will sift through the paraffin pushed out of the pipeline to see if it's there.

The pipeline runs from Prudhoe Bay on Alaska's North Slope to Valdez on Prince William Sound, where oil tankers collect crude oil and deliver it to West Coast refineries. It averaged 809,412 barrels per day in December.