On January 7, 2023, at approximately 4:55 p.m., about one (1) pound of anhydrous ammonia was released at the facility. Exposure to the toxic ammonia gas seriously injured one refrigeration technician. At the time of the incident, the employee was working on an ammonia compressor that was “out-of-service”. The ammonia compressor is used in the refrigeration system. The compressor had been previously isolated from the system, and the ammonia was understood to have been removed entirely.
When removing the bolts on the flange connecting the outlet piping to the compressor, a burst of ammonia vapor was released directly into the employee’s chest and face. The employee was not wearing respiratory protection because the ammonia compressor was understood to be empty.
SAFTENG NOTE: No Line/Equipment Opening Permit was issued for this work under the assumption that the compressor was free of NH3!!!
The injured employee was taken to a hospital for treatment of the ammonia exposure injuries he suffered. The facility’s investigation found that the company’s ammonia removal procedure allowed some ammonia to remain trapped between the compressor’s discharge check valve (a valve that only allows for single-direction flow) and an isolation valve. Another valve needed to be opened to remove ammonia from the isolated piping. It was determined that this valve had remained closed because the procedure did not include this valve.
Probable Cause
Based on the investigation, the CSB determined that the probable cause of the anhydrous ammonia release was disconnecting the outlet piping from the ammonia compressor while some ammonia remained within the equipment. The ammonia removal procedure contributed to the incident because following it did not effectively remove the ammonia from the compressor.
https://www.osha.gov/ords/imis/establishment.inspection_detail?id=1644489.015