Pipeline damage that crippled the nation's biggest oil field this week is triggering worries about not only the safety record of energy giant BP but also the reliability of the 200,000 miles of pipe that move oil products across the United States.

Some of that pipe was installed 100 years ago, most in the 1960s and '70s.

"We're learning that BP did not do its maintenance, but also that federal regulators have been asleep at the switch," Sen. Charles Schumer, D-N.Y., said yesterday. He demanded that federal regulators inspect interstate pipelines in the next 30 days "before another disruption causes a national energy emergency."

BP on Sunday ordered the shutdown of the Prudhoe Bay, Alaska, oil field, source of 8 percent of the oil produced in the United States. BP said a dangerously corroded pipeline, built in 1977, hadn't been scrubbed of sludge since 1992.

Regulators had ordered BP to test the line after a similar one at the oil field ruptured in March, spilling 267,000 gallons of oil. BP said this summer it could not meet the government's deadline because too much sludge — a cause of corrosion — was in the line to send a probe known as a "smart pig" through, said James Wiggins, a spokesman for the U.S. Pipeline and Hazardous Materials Safety Administration.

BP ultimately tested parts of the line and found corrosion had eaten more than two-thirds of the way through its walls in spots, triggering the shutdown.

The cause is being investigated, but "poor maintenance was obviously a factor," Wiggins said.

BP plans to replace 16 of the 22 miles of pipeline it operates around Prudhoe Bay. Spokesman Daren Beaudo said the company would ask regulators for permission to continue some production while repairs are made.

The government said it expects the field back in full production after January.

U.S. crude prices, which shot up after the shutdown was announced, closed yesterday at $76.31, down 67 cents.

Beaudo said BP would "upgrade" inspection practices at Prudhoe Bay.

Corrosion inside and outside the pipes is the biggest single cause of pipeline leaks, resisting eradication even as the industry minimizes other problems.

Data from the federal Office of Pipeline Safety show that between 2002 and mid-2006, internal corrosion, such as that at BP, was blamed for 60 of 593 pipeline accidents, totaling 69,292 barrels, causing $8.1 million in damage.

Corrosion can't be halted, only slowed, notes Tony Keane, executive director of NACE International, a corrosion engineers' trade group. "It has to be an ongoing maintenance process," he said.

A 2001 regulation requires tests every five years. Low-pressure lines such as those at Prudhoe Bay, are presumed safer and aren't subject to the federal rules.