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CSB: Mechanical Failure Caused Tank Explosion

A pressure vessel at the Loy-Lange Box Co. that exploded on April 3 and killed four people - including three Faultless employees in a building adjacent to the box facility - was leaking and was shut down for repairs on the Friday before the incident that took place the following Monday in St. Louis, according to a news release from the federal Chemical Safety Board (CSB).

The explosion released an amount of energy equivalent to roughly 350 lbs. of TNT, the release said.

The CSB’s report noted that the 17.5-foot-long, 30-inch-diameter steel pressure vessel had undergone emergency repairs in 2012 due to leaks. Five years later, following the March 31 shutdown, the deterioration of the metal in the tank caused additional leaking when the pressure vessel was restarted on Monday, April 3. As hot water in the pressure vessel converted to steam, it broke free and flew through the roof at a speed of roughly 120 mph. Kenneth Trentham of Loy-Lange died in the initial explosion. A co-worker at the scene also was critically injured. The nearly 2,000-lb. tank then flew roughly 520 feet before landing on the roof of Faultless Healthcare Linen, where it claimed the lives of staffers Tonya Gonzalez-Suarez, Clifford Lee and Christopher Watkins.

“The immediate cause of this incident is the sudden mechanical integrity failure of the entire ring of the original bottom of the pressure vessel,” a release from the CSB said. “This rupture separated the bottom of the tank from the rest of the pressure vessel. This created the unique conditions for a steam explosion, launching the vessel through the building about 520 feet before landing at the Faultless Healthcare Linen’s site. This was a massive explosion – releasing energy equivalent to about 350 lbs. of TNT.”

The release noted that a city ordinance requires inspections of all boilers annually. However, there was no evidence that the city had carried out any inspections. In an article in the St. Louis Post-Dispatch, a reporter questioned acting St. Louis Building Inspector Frank Oswald on this issue. Oswald said the city requires companies that operate boilers or related equipment to conduct their own yearly inspections with a stationary engineer licensed by the city. “The station engineer actually did say that the system was not proper,” he said. “I can’t really speculate why they would have done this when they had a professional saying not to. I don’t know who made that decision. I guess that’s the real question.”

The CSB – a nonregulatory federal agency charged with investigating serious chemical incidents – is continuing its inquiry into the incident. Faultless officials declined comment at this time. Click here and here for details.