Condensation induced waterhammer in district steam distribution systems can cause catastrophic rupture of piping and inflict severe damage to personnel, property, and environment. On July 18, 2007, a 20-in. diameter underground steam pipe in New York City ruptured at 5:56 p.m. at the intersection of 41st Street and Lexington Avenue in midtown Manhattan. At the time of rupture, the steam system was in service delivering steam to the customers at an operating pressure of approximately 160 psig and a steam temperature of approximately 370°F. The incident opened a large cavity measuring approximately 32 ft × 32 ft × 18 ft deep at the intersection of 41st Street and Lexington Avenue. The pipe rupture released steam, condensate, water, pipe insulation and various construction materials to the environment.

Consolidated Edison Co. of New York, Inc. (Con Edison) and LPI (Lucius Pitkin, Inc.) investigated the event. Based on detailed metallurgical and engineering evaluations of the steam system configuration and operating conditions, it was concluded that the steam pipe ruptured as a result of excessive pressure caused by condensation-induced waterhammer.

This paper presents a summary of the engineering evaluation, root cause, and conditions leading to the pipe rupture and provides measures which can be taken to reduce the likelihood of such a failure and enhance public safety.

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