A piping fitting failed, resulting in the release of approximately 5 pounds of ammonia (NH3) in the machinery room. The nipple (fitting) between the oil separator and its relief valve cracked and failed to hold ammonia in the piping, resulting in the activation of the exhaust ventilation system. Fittings made of certain materials are incompatible with ammonia and degrade quickly in its presence. For example, Copper and its alloys. The presence of vibration in the system further increases the chances of initiation and quick progression of any crack-type discontinuity, leading to the failure of the fitting.
Root Cause(s):
- cyclic service caused vibration in the piping system,
- incompatible fitting used
The pressure relief valve and nipple were installed on December 12, 2014. Within 3 years of installation, the nipple cracked at the inlet of the pressure safety valve.
At the start of the shift, the arena worker detected the smell of ammonia inside the machinery room. The ammonia detector read 25 parts per million (ppm), and the emergency alarm was activated at 7:43 am. The exhaust fan was activated, and the arena worker called the refrigeration contractor to the site. The contractor pinpointed the leak and isolated the oil separator and compressor, and changed the cracked fitting and pressure relief valve.
