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US Chemical Safety Board releases final report into fatal Loy-Lange Box Company explosion

02 August 2022

The US Chemical Safety Board (CSB) published its final investigation report into the 3 April 2017 explosion at the Loy-Lange Box Company in St. Louis, Missouri which killed four people. The report includes factual information and an analysis of the incident, as well as several conclusions and recommendations.

Image: CSB
Image: CSB

The CSB's final report can be found in full by clicking here.

The incident at Loy-Lange occurred when the bottom head of a pressure vessel called a Semi-Closed Receiver (SCR), which was used in Loy-Lange’s steam system, catastrophically failed. The pressure vessel failure caused a boiling liquid expanding vapour explosion (BLEVE) which fatally injured a Loy-Lange employee working nearby and launched the pressure vessel from the Loy-Lange building into the air. The vessel eventually crashed through the roof of a nearby business, fatally injuring three members of the public.

In the report, the CSB outlines how it found four key safety issues relating to the incident:
- Pressure Vessel Corrosion. Oxygen pitting corrosion and generalised corrosion thinned the pressure vessel bottom head until it could no longer contain the pressure inside the vessel. Aspects of Loy-Lange’s operation directly caused or failed to prevent the corrosion. The company’s start-up practices likely introduced oxygenated water into the SCR daily, and its inadequate water treatment failed to eliminate dissolved oxygen from the water.

- Pressure Vessel Inspection and Regulation. 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, however it 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.

- 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 3 April 2017, initiating the explosion. Aric Inc., the Authorized Inspection Agency for Kickham’s repair, did not detect Kickham’s inadequate repair.

- Process Safety Management Systems. Loy-Lange did not establish a strong process safety culture and did not have programmes that could have identified the hazards or analysed and mitigated the risks of its operations. Such programs could have enabled Loy-Lange to learn from its operational experience. Loy-Lange, however, did not employ sound process safety management principles in addressing the risks associated with corrosion in its steam process.

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 in its Semi-Closed Receiver and Kickham Boiler and Engineering’s performance of an inadequate repair to the SCR in 2012 that left damaged material in place. Contributing to the incident was the City of St. Louis’s missed opportunities to identify and ensure the inspection of the SCR, Arise Inc.’s acceptance of and failure to detect Kickham’s inadequate repair, and gaps in Arise’s and the National Board of Boiler and Pressure Vessel Inspectors’ repair inspection requirements.

The report also outlines several recommendations to the Loy-Lange Box Company, the City of St. Louis Board of Aldermen, the Mayor of the City of St. Louis, Arise Inc., and to the National Board of Boiler and Pressure Vessel Inspectors.

The CSB's final report can be found in full by clicking here.

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