Today the US Chemical Safety Board (CSB) released its latest安全视频detailing key lessons from the release of 32,000 pounds of anhydrous ammonia that occurred at Millard Refrigerated Services Inc. on August 23, 2010. The accident resulted in over 150 exposures to offsite workers, thirty of which were hospitalized – four in an intensive care unit.
新发布的七分钟的安全视频，题为“对系统的震惊”，”包括详细的3D动画，这些动画导致了最终的氨发布。该视频基于CSB最近标题的安全公告“预防工业制冷系统中液压冲击的关键课程。”
主席拉斐尔·穆雷·埃索索（Rafael Moure-Eraso）说：“ CSB的新安全视频是一种有价值的工具，旨在在利用无水氨的大量设施中使用。从我们的调查中学到的关键经验教训 - 在我们的报告和视频中进行了检查 - 可以帮助设施防止因液压冲击而导致的类似事故。”
CSB的视频可在其上使用YouTube频道和atwww.csb.gov
CSB的调查发现，事故发生前的第二天，米拉德设施经历了持续了七个多小时的电力损失。在此期间，制冷系统被关闭。第二天，即2010年8月23日，该系统恢复了电源，尽管运营商报告了某些问题，但仍在运行并运行。在进行一些故障排除时，操作员清除了控制系统中的警报，该警报重置了一组正在解冻的冰柜蒸发器上的制冷周期。
This resulted in both hot, high-pressure gas and extremely low temperature liquid ammonia to be present in the coils and associated piping at the same time. This caused the hot high-pressure ammonia gas to rapidly condense into a liquid. Because liquid ammonia takes up less volume than ammonia gas – a vacuum was created where the gas had condensed.
突然的压力下降通过管道散发了一波液体氨 - 导致突然的压力浪潮称为“液压冲击”。
This abnormal transient condition results in a sharp pressure rise with the potential to cause catastrophic failure of piping, valves, and other components. Often prior to a hydraulic shock incident there is an audible “hammering” in refrigeration piping,.
CSB Investigator Tyler said, “The CSB’s animation details how the pressure surge ruptured the evaporator piping manifold inside one of the freezers causing a roof-mounted 12-inch suction pipe to catastrophically fail, resulting in the release of more than 32,000 pounds of anhydrous ammonia and its associated 12-inch piping on the roof of the facility.”
The release resulted in injuries to a Millard employee when he fell while attempting to escape from a crane after it became engulfed in the traveling ammonia cloud. The large cloud traveled a quarter mile from the facility south toward an area where 800 contractors were working outdoors at a clean-up site for the Deepwater Horizon oil spill. A total of 152 offsite workers and ship crew members reported symptomatic illnesses from ammonia exposure. Thirty two of the offsite workers required hospitalization, four of them in an intensive care unit.
该视频介绍了从CSB的调查中汲取的关键课程，包括避免在解冻中手动中断蒸发器的手动中断，并要求控制系统配备密码保护，以确保只有经过培训和授权的人员有权手动覆盖系统。在事件当天，控制系统没有意识到蒸发器已经在解冻过程中，并且允许操作员手动重新启动制冷循环，而无需从蒸发器线圈中除去热氨气。
CSB还发现，Millard设施的蒸发器的设计是为了控制四个独立的蒸发器线圈。结果，连接到该阀组的所有四个线圈的内容都参与了液压冲击事件，从而导致更大，更危险的压力激增。结果，CSB指出，在设计氨冷藏系统时，每个蒸发器线圈应由单独的阀组控制。
一个d the CSB found that immediately after discovering the ammonia release, a decision was made to isolate the source of the leak while the refrigeration system was still operating instead of initiating an emergency shutdown. Shutting down the refrigeration system may have resulted in a smaller release, since all other ammonia-containing equipment associated with the failed rooftop piping continued to operate. A final key lesson from the CSB’s investigation is that an emergency shutdown should be activated in the event of an ammonia release if a leak cannot be promptly isolated and controlled. Doing so can greatly reduce the amount of ammonia released during an accident.
CSB是一个独立的联邦机构，负责调查严重的化学事故。该机构的董事会成员由总统任命，并由参议院确认。CSB的调查研究了化学事故的各个方面，包括设备故障以及法规，行业标准和安全管理系统等物理原因。
董事会不发出引文或罚款，而是对OSHA和EPA等工厂，行业组织，劳动团体和监管机构提出安全建议。访问我们的网站，www.csb.gov。For more information, contactpublic@csb.gov。
