CSB Releases Investigative Update Into Loy Lange Box Company Catastrophic Pressure Vessel Failure
May 25, 2017, St. Louis, MO – The U.S. Chemical Safety Board (CSB) released a “Factual Investigative Update” on the April 3, 2017, catastrophic rupture of a pressure vessel at the Loy Lange Box Company that killed four people and left another in critical condition.
The CSB’s ongoing examination of the incident has identified a history of leaks in the pressure vessel, which was part of a steam generation system. In 2012, the vessel was repaired when it was discovered that water was leaking from the bottom of its tank. In what was termed an “emergency repair,” a portion of the bottom of the tank was replaced with a custom made center section.
On Friday, March 31, 2017, employees again noticed a leak from the bottom of the vessel. Photos taken by the employees revealed leaks coming from at least two distinct sections of a 6-inch ring of original tank material that had been left surrounding the replacement center section of the vessel in 2012. Three days later, on April 3, Loy-Lange started up the steam generation system and the vessel ruptured in the area of that ring.
In examining the vessel post-incident, investigators found the metal in the rupture area extremely thinned from its original state. While the thickness of the metal should have been a quarter of an inch (0.25”) thick, this specific area had been worn down to eight hundredths of an inch (0.08”).
The immediate cause of this incident is the sudden mechanical integrity failure of the entire ring of the original bottom of the pressure vessel. 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 Fautless Healthcare Linen’s site. This was a massive explosion – releasing energy equivalent to about 350 pounds of TNT.
The City of St. Louis is required to inspect the pressure vessel by its ordinance; however, the CSB has received no evidence of inspection.
The investigation will continue with mechanical analysis and additional document reviews, interviews, research and analysis. A full factual investigative update can be found here.
The CSB is an independent, non-regulatory federal agency charged with investigating serious chemical incidents. The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Visit our website at www.csb.gov.
=========================
ST. LOUIS, MO
The U.S. Chemical Safety and Hazard Investigation Board says the immediate cause of a steam tank explosion at the Loy-Lange Box Co. that killed four people last month was the failure of original steel that remained after a 2012 emergency repair to the bottom of the tank.
That steel was "uniquely vulnerable to catastrophic failure" because corrosion left it much thinner than the newer steel circle that had been welded onto the bottom, according to a report the investigative board released Thursday.
Moreover, stationary engineers at Loy-Lange had noticed the tank was leaking again three days before the explosion, the report says. The board investigation found that the company had shut down the steam-generation system on Friday, March 31, and arranged for a repair to be performed Monday, April 3.
"On Monday, despite the leak and the pending technician visit, Loy-Lange started up the steam generation system," the report says. "… it appears that the catastrophic failure occurred near the end of the start-up process."
The 17.5-foot-long, 30-inch diameter carbon steel tank was part of the steam heat system used to manufacture corrugated cardboard. It was inspected and registered with the National Board of Boiler and Pressure Vessel Inspectors in February 1997, the report says.
The company that made the 2012 repair, Kickham Boiler and Engineering, submitted a proposal about a month later to replace the entire bottom four feet of the tank, but the box company never made that repair, the report says. The new steel would have been 50 percent thicker than the original as a "corrosion allowance," the report states.
The report explains that repairs to such tanks can be overseen by states or cities. Missouri requires repairs to comply with National Board standards, but the city of St. Louis "opted out of the state requirement" and instead has its own mechanical code that requires annual inspections. The report states the city has not provided investigators "any evidence of inspections" of the tank in question.
The city's mechanical code requires all mechanical systems to be maintained in a safe condition. The responsibility for this provision falls to the owner of the building, the report says. City inspections "shall be as thorough as circumstances permit," leaving it up to the inspector to decide what is sufficient.
The city's code also requires a permit for repairs such as the one performed at Loy-Lange in November 2012. The Chemical Safety and Hazard Investigation Board found no evidence that Loy-Lange requested a permit for the repair, nor that the city issued one.
Tank removed from deadly explosion site in Soulard
KTVI - St. Louis, MO
The report describes details of the explosion:
About 7:20 a.m. April 3, the bottom of the 1,952-pound steel tank, known officially as a semi-closed receiver, failed, causing the pressure to suddenly drop. The resulting steam explosion launched the tank through the box company roof, killing one employee and critically injuring another. The tank flew at about 120 mph, rising 425 feet over the street. It was airborne for more than 10 seconds, then crashed through the roof at Faultless Healthcare Linen, 2030 South Broadway, killing two people and fatally injuring a third as they filled out paperwork on their first day on the job there. The energy released was equivalent to about 350 pounds of TNT, and propelled the tank about 520 feet from Loy-Lange's building at 222 Russell Boulevard.
Pipe and debris rained down on the industrial area near Soulard. A building at 400 Russell Boulevard, owned by Pioneer Industrial Group, suffered damage when a large piece of pipe punctured the roof and ruptured the sprinkler system. A 7-foot pipe speared the windshield of a truck parked nearby, embedding in the dashboard and floorboard.