Ammonia Release | Auto-Purger

Summary

In September 2012, the rupture of an auto-purger bubbler resulted in two injuries, one of which was permanent and disabling. The root causes were determined to be a buildup of scale inside the bubbler, and failure to follow proper maintenance/operating procedures.

Incident Description

Water & mineral deposits were collected in the drain line of the auto-purger which eventually prevented water from draining freely from the bubbler. As a result, water began to escape from the top of the bubbler where the ¼” vent is located. 

The two operators responsible for troubleshooting the situation failed to isolate and pump down the auto-purger before performing work. Instead, the vent hole was plugged, but the scale buildup in the drain pipe was not discovered or addressed. Since the water could no longer drain from the bubbler, the pressure rose when the auto-purger went through its normal purge cycle, and the bubbler ruptured. Both operators were standing near the bubbler and were splashed in the face with aqueous ammonia.

Significance

With further training regarding auto-purger operation and maintenance procedures, it is likely that the operators could have determined the root cause, and avoided the incident altogether. Based on the approach taken to address the water leak, it can be assumed that the operators were not aware that the hole they plugged was a necessary  vent port for proper drainage. Furthermore, if the auto-purger had been isolated and pumped down before performing work, the bubbler would not have overpressurized while the operators were addressing the water leak. 

This incident illustrates the importance of ensuring personnel are equipped with sufficient knowledge of a component to perform work safely. The auto-purger design is complicated and is hard to grasp intuitively. This is an instance where written operating procedures can be valuable both for training purposes and for guidance while performing work on the system.