The U.S. Chemical Safety Board (CSB) released a new safety video about the fatal explosion that occurred on April 3, 2017, at the Loy-Lange Box Co. in St Louis, MO. The incident occurred when a severely corroded pressure vessel catastrophically failed, causing an explosion that launched the pressure vessel into a neighboring building. One worker and three members of the public were fatally injured.

The video includes an animation of the sequence of events leading to the incident, as well as interviews with both the CSB’s interim executive Steve Owens and lead investigator Drew Sahli. 

During its investigation, the CSB found that over the course of many years, an area of the failed pressure vessel had thinned due to a known corrosion mechanism that was poorly controlled at Loy-Lange. And the CSB found that Loy-Lange repeatedly ignored clear warnings that corrosion was causing major problems within its operations. The CSB found that prior to its failure, Loy-Lange ran the pressure vessel normally despite knowing that it was leaking.

In the video, Owens summarizes the CSB findings: “The incident at Loy-Lange resulted from a tragic series of circumstances -- ineffective corrosion management, inadequate pressure vessel repair, a lack of inspections, and the absence of sound safety management systems. The result of those factors was that a severely corroded pressure vessel, which presented a serious safety hazard, was allowed to operate until it ultimately failed, resulting in the death of four people.”

The potential for corrosion was a well-known problem at Loy-Lange. During its time operating the pressure vessel that failed, Loy-Lange experienced at least three leaks due to corrosion. In response to a 2012 leak, a repair company removed most of the area of the pressure vessel where the failure occurred. The company patched it with new steel but left some of the original steel in place. The original steel, however, was also thinned from corrosion, and between 2012 and 2017, it continued to degrade. The CSB found that it was the unacceptably thin remaining material from that repair that failed, initiating the incident.

The CSB also learned that Loy-Lange never applied for an installation or repair permit for the pressure vessel, or otherwise registered the vessel with the city of St. Louis. Therefore, although the City required annual inspections of boilers and pressure vessels, the CSB found that there was no record of a city inspector ever having inspected the pressure vessel. The CSB also found, however, that the City also did not inspect the Loy-Lange steam generators as frequently as required by the City’s code and therefore missed opportunities to identify the unpermitted pressure vessel that was in close proximity to one of the Loy-Lange steam generators.

Owens concludes the video saying, “Leaking pressure vessels can be dangerous and should be thoroughly evaluated to ensure they are fit to operate. But even before a pressure vessel is compromised there are many ways for companies to ensure that damage mechanisms, including corrosion, are properly understood and controlled. Doing so can prevent catastrophic incidents before they ever happen.”