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Clogged valve cited in New York steam pipe blast

NEW YORK (Reuters) - Utility Consolidated Edison on Thursday blamed a pressure buildup caused by a faulty repair and excessive rain for July’s steam pipe explosion that killed a person and created panic in Manhattan.

Workers wearing Hazmat suits inspect the site of a steam pipe explosion in New York July 19, 2007. Utility Consolidated Edison on Thursday blamed a pressure buildup caused by a faulty repair and excessive rain for July's steam pipe explosion that killed a person and created panic in Manhattan. REUTERS/Brendan McDermid

The 83-year-old steam pipe exploded underground during the afternoon rush hour on July 18, shaking buildings, creating a towering geyser of debris and sending people fleeing in scenes reminiscent of the Sept. 11 attacks.

The combination of rain water that built up around the pipe and clogging inside a steam trap, or automated valve, created more than seven times the pipe’s normal operating pressure in what is called a water hammer, Con Edison said.

That led to the blast that rocketed up through the street near the Grand Central rail and subway station.

One person died and two people were badly burned.

The pipe’s two steam traps were clogged with epoxy resin that had been injected into the system to repair a leaking flange months earlier, Con Edison said in a statement.

“Some of the resin ultimately entered the traps and hampered their drainage of excess water inside the steam pipe,” the statement said.

In addition, heavy rains that morning flooded the outside of the pipe, cooling it and creating excessive condensate, or water build-up, inside the pipe, the statement said.

In response Con Edison said it was replacing all 1,654 steam traps and will implement new responses to heavy rain, among other measures.

Con Edison, primarily an electricity and gas utility, also transports steam underground for a variety of industrial purposes.

As a regulated monopoly, Con Edison naturally receives its share of public criticism, and the steam pipe blast came amid bad publicity from power blackouts.

Con Edison shared traded flat the day after the blast and have risen 6.3 percent since then compared to a 6.9 percent rise in S&P Utilities index.

Editing by David Wiessler

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