The U.S. Chemical Safety and Hazard Investigation Board (CSB) released a safety video Dec. 7 on the events leading to the April 2017 fatal explosion at the Loy-Lange Box Company in St. Louis, Missouri.
The video includes an animation of the sequence of events leading to the incident and interviews with CSB Interim Executive Steve Owens and Lead Investigator Drew Sahli.
1 worker, 3 bystanders at neighboring business killed
On the day of the incident, a severely corroded pressure vessel catastrophically failed, causing an explosion that launched the pressure vessel into a neighboring building.
One worker was killed in the explosion and two bystanders were struck and killed by the boiler when it crashed into the neighboring business. A third bystander was trapped under the boiler where it landed and later died from his injuries.
Corrosion was well-known problem
Investigators 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.” A CSB investigation report said the company “repeatedly ignored clear warnings that corrosion was causing major problems within its operations.”
“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,” Interim Executive Owens said in the video. “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.”
Corrosion was a well-known problem at Loy-Lange, with the failed pressure vessel having experienced at least three leaks due to corrosion prior to the explosion. In 2012, a repair company removed most of the area of the pressure vessel where a failure occurred, but the remaining steel was also thinned from corrosion and continued to degrade.
The CSB found that it was the unacceptably thin remaining material from the 2012 repair that failed, causing the explosion.
Pressure vessel never inspected by city officials
Loy-Lange also never applied for an installation or repair permit for the pressure vessel and it was never registered with the city of St. Louis. Since it wasn’t registered, the pressure vessel was never inspected by city officials.
However, the city also failed to inspect Loy-Lange’s steam generators as frequently as regulations required, so it missed several opportunities to identify the nearby unpermitted pressure vessel.