Ammonia Release | Roof Collapse

Summary

In December 2016, a roof collapse resulted in a release of approximately 24,000 lbs of ammonia. Two (2) ceiling-suspended evaporators were hung from the roof and fell to the ground when the structure collapsed. 

Incident Description

During a heavy rainstorm, the roof over a cold storage room collapsed. Two (2) ceiling-suspended evaporator coils fell with the roof, breaking the piping between the roof-mounted accumulator and the two coils. Additionally, a large water pipe broke and flooded the room. The facility was evacuated and first responders were notified.

First responders arrived on scene and shut off power and water to the facility. The king valve was closed by the Hazmat team and no further action was taken due to structural concerns. Ammonia levels inside the facility were monitored until it was determined that the leak was no longer active. 

Release Calculation

The system inventory prior to the release was 28,000 lbs. After the release, an ammonia supply company came on-site to remove the remaining ammonia inventory from the system. The amount removed was approximately 3,705 lbs. Therefore, the amount released was calculated by subtracting 3,705 lbs from the initial inventory of 28,000 lbs.

Ammonia Released = 28,000 lb – 3,705 lb = 24,295 lb 

Significance

IIAR 2-2021 §6.2.2 states that “Where piping is supported by the floor, roof, or ceiling structure, the structure or foundation supporting the piping shall be designed to support the expected static and dynamic loads, including seismic loads. Foundations and supports shall be in accordance with the building code.”

Insufficient roof drainage appears to be a contributing factor to the roof collapse. While it is unknown whether the roof structure was designed in accordance with the Building Code at the time it was installed, this incident illustrates the importance of monitoring the building structure and foundation. Even if a building is designed to code, decades of deterioration may result in a sudden collapse if not monitored and addressed.