Tuesday, November 2, 2010

Low-frequency ER welds may be putting PG&E pipelines at risk

SAN FRANCISCO, Calif. - As much as two-thirds of Pacific Gas and Electric Co. network of major natural gas pipelines may be vulnerable to failure because the pipe was made before 1970, using welding techniques that have been outmoded for four decades, a San Francisco Chronicle report alleges.
The problem is the result of a pre-1970 welding technique that put welds on the pipe seams that seal the spine of the pipe. The technology - known as
low-frequency electric resistance welding - could allow the pipe spine
to rupture more readily, especially when the pipe has been weakened by corrosion or a nearby dent.
Federal regulators warned pipeline companies more than 20 years ago to
reconsider use of pipelines older than 1970. That warning applies to the transmission line that exploded in San Bruno - it was built with pipe manufactured using the low-frequency ERW technology.
Government regulators did not require that pipeline companies replace the old pipe, however, mandating only that operators inspect lines in populated areas for problems.

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