After unscheduled maintenance to drain oil from the pumps, the refrigeration system was noted to be slow to return to performance and oil contamination of some system evaporators was suspected. The responding refrigeration mechanic stated he attempted to improve system performance by closing valves to generate pressure within an evaporator to move or dislodge potentially trapped oil. The pressure rose very rapidly once the evaporator was isolated between closed valves, breaking a pressure gauge needle (photo 3) and rupturing the evaporator (photos 1 and 2). An estimated 485 to 1,500 lbs of ammonia was released from the ruptured evaporator into the freeze-drying production chamber.
The chamber is not designed to contain ammonia and therefore ammonia escaped the chamber into the atmosphere. There was no provision for ammonia extraction from the chamber. As a result, a significant volume of ammonia entered into the chamber and could not be quickly removed. The release resulted in an extensive area being evacuated for two days (Diagram 1) while the leaked ammonia was dispersed into the atmosphere and contained within a water solution.
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