CSB Provides Update on Investigation of Fatal Explosion in St. Louis

The U.S. Chemical Safety Board (CSB) has confirmed that the vessel that launched into the Faultless Linen building was a vertical condensate storage tank, technically referred to as the SCR or semi-closed receiver. The SCR provided the condensate or hot water to a steam generation and supply system supporting a corrugated box manufacturing process. That process was being started up on the morning of the incident.  Initial visual examination suggests that the bottom pressure boundary of the SCR failed.  Once the SCR unit is removed from the building, CSB investigators will conduct a more thorough inspection of the SCR. 

According to initial calculations performed by CSB investigators, the SCR contained about 510 gallons of water and was operated at about 330°F and 100 psig. The SCR itself is roughly 20 to 25 feet tall and about 3 feet in diameter and about 3000 lbs. When the vessel failed, the hot condensate jetted from the bottom, converting from hot water to steam. The power of the jet of water rapidly turning to steam broke the vessel loose from its piping attachments and fastenings, propelling it through the internal structure and roof of the building. The downward force of the steam launched the 3,000 pound vessel with a speed of about 120 mph, about 425 feet into the air and about 515 feet from its starting point. The SCR remained airborne for over 10 seconds.’

The structural integrity of both buildings is still being assessed. One crew was able to enter an area deemed safe at the Loy-Lange facility to 3-D photo-document the scene. This information will be used to further assess the site and determine next steps to stabilize the building and the location of potential evidence. Protocols to remove the SCR from the Faultless building are also being developed. The failure mode of the SCR is unknown at this early stage in the assessment, however, in cases of vessel failure it is typical for the CSB to examine issues of vessel operation, preventive maintenance, and mechanical integrity.

About the CSB

The CSB is an independent federal agency whose mission is to drive chemical safety change through independent investigations to protect people and the environment. The agency’s board members are appointed by the President and confirmed by the Senate. CSB investigations look into all aspects of chemical incidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems.

For more information, contact public@csb.gov.