scope:

Description of Driving Event:

During repressurization of a test chamber, ammonia in a test article heat exchanger froze resulting in rupture of the exchanger. The rupture caused pressure to build up in a second test support unit. This second unit had a pressure relief valve, which was released when the pressure exceeded the upper limit, spilling ammonia into the work environment. The facility had to be evacuated.

The root cause of this mishap was failure to treat "low hazard" systems, when connected to ammonia systems, as ammonia hazard systems. Had this been done, the design of the relief valve would have been configured to preclude direct venting of the valve into the facility work environment.