Ammonia Release | Brine Chiller

Summary

In October 2017, an ammonia release inside a machinery room resulted in the deaths of three people – two city workers and one refrigeration technician. A pinhole leak developed in a shell and tube brine chiller, which allowed ammonia to leak into the brine solution. The leak was discovered, but due to a lack of refrigeration knowledge, the root cause was not properly addressed. This allowed a larger leak to occur later that day while personnel were present in the machinery room. Click here for a detailed video of the event.

Incident Description

The ammonia refrigeration system was used to cool a brine solution. The brine circulated and chilled two ice rinks installed at the facility. Corrosion in a shell and tube brine chiller caused the formation of a pinhole in one of the tubes. Ammonia leaked through the pinhole and began to mix with the brine solution. Some of the brine solution is stored in tanks that are open to the atmosphere. Once the ammonia reached these tanks, the vapor triggered the ammonia detectors which activated an alarm, and notified the fire department and security company.

Two firefighters and one city worker entered the machinery room wearing SCBAs (self-contained breathing apparatus). Using hand-held ammonia detectors, the ammonia concentration was measured at 300 ppm. The leaking chiller was isolated on the ammonia side, and the ammonia refrigeration system was shut down. Parts of the brine system were shut down and the machinery room was vented of ammonia vapor. Eventually, the ammonia levels in the machinery room dropped to 50 ppm. Unbeknown to the responders, the ammonia continued to leak into the brine solution, even after the chiller was isolated.

In order to prevent the ice rinks from melting, it was decided that the ammonia compressors should be turned back on. It was soon discovered that the oil in the compressors had been contaminated with brine which prevented the compressors from starting. A refrigeration contractor was called to replace the oil in the compressors.

Prior to the arrival of the contractor, the ammonia alarm was placed into silent mode. When the contractor and two city workers entered the machinery room, they were not wearing PPE (personal protective equipment), or equipped with ammonia detectors.

While the oil was being changed, the pressure in the brine piping began to rise due to the increasing amounts of ammonia inside the brine system. One of the couplings in the brine piping was unable to withstand the pressure buildup, causing it to separate and spray the three workers with ammonia and brine. The resulting ammonia concentration in the machinery room was not survivable and resulted in the deaths of the contractor and two city workers.

Significance

Many steps were taken without sufficient knowledge which resulted in this tragedy. If the first responders had been advised by a knowledgeable refrigeration expert, they would have been able to properly isolate and pump down the shell and tube chiller. Once the shell and tube chiller was empty of both ammonia and brine, it could have been completely isolated and the leak mitigated. This incident also illustrates the deadly toxicity of ammonia and how quickly a situation can escalate. Proper PPE and training can make the difference between escaping with your life, or never making it back home.