Engineering Design & Testing Corp. Releases Preliminary Findings on Deadly U.S. Steel Explosion at Clairton Coke Works

A Connecticut engineering firm retained by U.S. Steel to investigate the deadly Aug. 11 explosion at its Clairton Coke Works facility today released preliminary findings.

The firm, Engineering Design & Testing Corp., issued the following information on its website Thursday:

The explosion took place in the 13-14 Coke Battery transfer area when an 18-inch cast iron valve ruptured, releasing flammable coke oven gas, which subsequently exploded. The valve was originally manufactured in 1953 and underwent refurbishment approximately ten years ago.

Damage to other valves at 13-14 Coke Battery was determined to have resulted from the explosion. At the time that the valve ruptured, U. S. Steel employees and employees of MPW Industrial Services were opening and closing the valve to ensure proper operation in advance of planned maintenance activities.

As part of the valve opening and closing work, water at a high pressure was introduced into the valve in order to flush accumulated deposits. A sealed cavity inside the body of the valve filled with high-pressure flush water in excess of the pressure rating of the valve. This resulted in a sudden and complete rupture of the valve body, releasing combustible coke oven gas. The coke oven gas accumulated in the transfer area basement and exploded when it reached an ignition source at the adjacent 14 Battery.

Among the findings? The firm determined that U. S. Steel did not have a specific procedure addressing the use of high-pressure water to flush valves. 

“U. S. Steel does have an established Management of Change procedure that should have been used to evaluate the change from low pressure steam to high pressure water,” the report stated.

U.S. Steel Thursday morning announced the findings on its social media platforms and issued a statement that read in part:

“These initial findings are consistent with our own, and we remain committed to working closely with all parties involved in investigations—including the Chemical Safety Board, OSHA, and EDT—to ensure a comprehensive understanding of the event. In parallel, we continue our investigation, and we’ve already strengthened several safety protocols based on what we’ve learned.”

Editor’s Note: Stay tuned. GASP continues to follow this issue closely and will keep you posted. Please check out our Clairton Explosion resource page for the latest developments, documents obtained through public records requests, and a timeline of events.