Alberni Valley Multiplex ammonia release incident investigation results

The yellow box (far right) shows the location of weld failures in the direct expansion chiller at the Alberni Valley Multiplex that led to an ammonia leak.

Technical Safety BC has published its incident investigation report into an ammonia release at the Alberni Valley Multiplex.

At 6 a.m. on November 3, 2019 an ammonia leak was detected. It later reached 25 ppm which activated an alarm in the ammonia detection system.

The source of the ammonia leak was found to be coming from a weld crack in the chiller vessel, one of multiple internal cracks found in the chiller, likely created during manufacturing. The crack grew while the chiller was in service until it penetrated the vessel shell, releasing ammonia into the room. Cracks can form inside welds during manufacturing if certain precautions—such as welding procedures that avoid formation of internal defects and high residual stresses—are not taken. Stress corrosion cracking was also a possible contributing factor. Caution should be exercised to avoid stress corrosion cracking in welds of "direct expansion" chillers such as the one in use at the Multiplex. This chiller design is such that it requires a relatively low charge of ammonia compared to traditional flooded chillers. However, the ammonia charge in the new chiller was still sufficient to cause serious harm in the case of an uncontrolled release.

According to the investigation, the Alberni Valley Multiplex remained operational for approximately two days while leaking, before the source was found. Technical Safety BC reminds equipment owners and operators that even "small" leaks can quickly become very dangerous if the cause is not understood and effectively managed. All ammonia leaks must be reported to Technical Safety BC within 24 hours of occurrence, as per the Safety Standards Act.

Technical Safety BC’s full incident investigation summary provides an overview of the incident, the scope of our investigation, and key technical findings. The report is available at:  https://www.technicalsafetybc.ca/alerts/ammonia-leak-alberni-valley-multiplex

About Technical Safety BC
Technical Safety BC (formerly BC Safety Authority) is an independent, self-funded organization that oversees the safe installation and operation of technical systems and equipment. In addition to issuing permits, licences and certificates, it works with industry to reduce safety risks through assessment, education and outreach, enforcement, and research. For more information, visit www.technicalsafetybc.ca/about.

Media contact:
Media Relations Team
Email: media@technicalsafetybc.ca
Cell: 778 396 2164

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