The gasket on the suction valve cover failed
The gasket on the suction valve cover failed allowing ammonia to release into the machine room which set off the high ammonia alarm at approximately 02:00 hours. Qualified personnel responded to find the sensor readings at 500 ppm.
The ammonia enters the compressor through the suction valve which is designed with a cover plate that is removable. The gasket between the valve body and cover is approximately 0.020” thick and has four holes for the bolted connection. The gasket failed at one of the bolt holes.