CSB Cites Ineffective Corrosion Management as Contributing Factor to the Deadly 2017 Explosion at Loy-Lange Box Company in St. Louis

U.S. Chemical Safety Board (CSB), August 2, 2022

The U.S. Chemical Safety Board (CSB) has released its final report on the deadly 2017 explosion that occurred at the Loy-Lange box company in St. Louis, Missouri. On April 3, 2017, the bottom head of a pressure vessel called a Semi-Closed Receiver (SCR), which was used in Loy-Lange’s steam system, catastrophically failed causing a boiling liquid expanding vapor explosion that fatally injuring one employee at the company and launched the pressure vessel from the building and through the roof of a nearby business, fatally injuring three members of the public.

The Chemical Safety Board investigated and 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. The CSB also found that Loy-Lange repeatedly ignored clear warnings that corrosion was causing major problems within its operations. In fact, prior to its failure, Loy- Lange ran the pressure vessel normally despite knowing that it was leaking.

CSB Interim Executive Steve Owens said, “A tragic series of circumstances contributed to the explosion at Loy-Lange: ineffective corrosion management, poor pressure vessel repair, a lack of inspections of the vessel, and the absence of sound safety management systems. Those factors led to a severely corroded pressure vessel that presented a serious safety hazard but was allowed to operate until it ultimately failed, taking the lives of four people.

The CSB determined that the cause of the explosion was deficiencies in Loy-Lange’s operations, policies, and process safety practices that failed to prevent or mitigate chronic corrosion.

Furthermore, the CSB determined that contributing to the incident was the City of St. Louis’s missed opportunities to identify and ensure proper inspections, identify an inadequate repair and existing gaps in inspection requirements.

As a result of its findings the CSB identified the following four safety issues and is issuing recommendations to Loy-Lange, the City and Mayor of St. Louis, the inspection company Arise, and the National Board of Boiler and Pressure Vessel Inspectors.  

  1. Pressure Vessel Corrosion. Oxygen pitting corrosion and generalized corrosion thinned the pressure vessel bottom head until it could no longer contain the pressure inside the vessel. Aspects of LoyLange’s operation directly caused or failed to prevent the corrosion: Loy-Lange’s startup practices likely introduced oxygenated water into the SCR daily, and its inadequate water treatment failed to eliminate dissolved oxygen from the water.
  2. Pressure Vessel Inspection and Regulation. Pressure vessels are used across nearly all manufacturing sectors, including steam production, refining, petrochemical manufacturing, pulp and paper, and many other industries. Industry codes, guidance, and regulations provide methods to inspect and maintain pressure vessels safely, as pressure vessel failures can be catastrophic, as demonstrated by this incident. Loy-Lange was aware of corrosion in the SCR as early as 2004. Loy-Lange, however, had no mechanical integrity or inspection program, as recommended within industry guidance documents, to monitor or mitigate corrosion in the SCR. The City of St. Louis was the regulatory authority responsible for inspecting pressure vessels in the city. However, due to manpower limitations and Loy-Lange’s deficient regulatory compliance, the City never inspected the SCR.
  3. Pressure Vessel Repair. A repair made to the SCR in 2012 by Kickham Boiler and Engineering, a National Board “R” Certificate holding company, did not adhere to applicable National Board Inspection Code requirements because Kickham likely left material in place that was thinner than the SCR’s required minimum thickness. Only a portion of the corroded pressure vessel bottom head was replaced, leaving the compromised remaining portion of the head in place to continue corroding. This remaining portion of original steel failed on April 3, 2017, initiating the explosion. Arise, the Authorized Inspection Agency for Kickham’s repair, did not detect Kickham’s inadequate repair. When repairing a pressure vessel, it is essential to remove all unacceptably damaged material. Repair companies and inspectors must ensure that such material is fully removed.
  4. Process Safety Management Systems. Loy-Lange did not establish a strong process safety culture and did not have programs that could have identified the hazards or analyzed and mitigated the risks of its operations. Such programs could have enabled Loy-Lange to learn from its operational experience. LoyLange, however, did not employ sound process safety management principles in addressing the risks associated with corrosion in its steam process. It is essential that facilities with hazardous processes have an effective process safety management system to help ensure major incidents such as the LoyLange incident are prevented.


About the CSB

The CSB is an independent, non-regulatory 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. The CSB does not issue citations or fines but makes safety recommendations to companies, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. For more information, please visit

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