A consultant hired by U.S. Steel to investigate an August 11 explosion at the company’s Clairton Coke Works found water pumped into a valve during a scheduled maintenance exceeded the valve’s pressure rating, leading to the blast that killed two workers.
“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,” said the preliminary investigation report, from Connecticut-based Engineering Design & Testing Corp (EDT).
High pressure water was pumped into the valve “in order to flush accumulated deposits,” the report said. “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.”
Ten other workers were injured in the blast.
The valve was originally manufactured in 1953 but refurbished “approximately ten years ago,” the report said.
The report said the company had previously used low-pressure steam at less than 10 pounds per square inch, to clean and flush the valve.
It said the company did not have “a specific procedure addressing the use of high-pressure water to flush valves.” The company has a “Management of Change procedure that should have been used to evaluate the change from low pressure steam to high pressure water,” the report said.
U.S. Steel did not respond to questions about why workers were using high-pressure water, not low-pressure steam, to flush the valve at the time of the explosion, or why the company was using a piece of hardware made over 70 years ago at the plant.
In a statement, the company said that it had prohibited the use of high-pressure water for valve cleaning, and is conducting a “thorough review and restructuring” of its “Management of Change program.” The company said it was reviewing its corporate governance documents and making adjustments to provide more detailed guidelines to workers.
“Throughout this process, our top priority continues to be the safety and well-being of our employees, their families, and our communities,” the statement said.
The U.S. Chemical Safety Board and Occupational Safety and Health Administration are also investigating.
Bill Farrier, president of Local 1557 United Steelworkers, which represents around 1,000 employees at Clairton, declined to comment on the report.
