Ammonia Release | Falling Ice Breaks Pipe

Summary

In December 2022, a falling piece of ice broke off a ¾” ammonia charging connection on a high pressure receiver. This resulted in a release of approximately 2,375 lbs of ammonia. 

Incident Description

Extreme weather conditions resulted in excessive ice buildup under the condenser platform. The high pressure receiver was located under the condenser platform, where it was susceptible to falling ice. A portion of the ice fell onto a ¾” nipple associated with the high pressure receiver, shearing it off upstream of the charging connection check valve.  

The facility quickly responded by closing isolation valves on both the high pressure receiver and the thermosyphon vessel in order to isolate the leak. 

Release Calculation

Due to the nature of the release, flash gas was developed as the liquid ammonia leaked out of the broken pipe. Therefore, the release calculation was performed as follows which accounted for both liquid ammonia, and the resulting flash gas:

Analysis

IIAR Technical Papers, 30th Annual Meeting (2008), Tech Paper 7, Estimating Refrigerant Release Quantities, Fauske Model, Equation 10:

Significance

Falling ice has the potential to both damage ammonia equipment, and cause injury to employees. While extreme weather conditions cannot be helped, ice buildup should be monitored and removed if the need arises.