CORRECTION: Oct. 8: This story has been corrected to show that maintenance was being performed on a gas isolation valve.
The federal board investigating the fatal August explosion at the Clairton Coke Works says the incident happened when a crew did maintenance on a gas isolation valve.
In a preliminary update, the U.S. Chemical Safety Board said a U.S. Steel worker identified a leak in a gas isolation valve on July 8. A cracked valve was patched, and the company planned to take the surrounding area — called a coke battery — off-line to replace several valves.
Clairton Coke Works, site of Monday’s explosion, has a history of problems
A battery is a series of ovens where coal is heated to become coke, a fuel used for steel making. As it’s baked, the coal gives off volatile compounds that can be collected and processed into a mixture of hydrogen, methane, nitrogen and carbon monoxide gases, which can be used to fuel the ovens.
On Aug. 11, a crew went to open and close the Battery 13 gas isolation valve to “exercise” it. Because residue builds up on the valves, they also planned to flush the valve with water.
The CSB noted U.S. Steel’s procedure specifies the steam pressure allowed for cleaning valves, but does not mention water.
Shortly after the crew pumped water into the valve, monitors alerted the workers to a gas leak. A supervisor called for others to evacuate.
The explosion happened less than one minute after the evacuation order. Two people were killed: Steven Menefee and Timothy Quinn.
Five other workers were seriously injured and hospitalized, and six were treated for injuries but not hospitalized.
The CSB said the valve involved was a cast iron, 18-inch, double disc gate valve that was made in 1953 and had been refurbished in 2013. The valve body had fully split open. Other valves also showed signs of damage.
In a statement, United Steelworkers Union District 10 Director Bernie Hall said USW appreciates the board’s attention to the incident and that they will continue to work with investigators as they finish their report.
“We owe it to our fallen siblings to not only learn everything we can about what may have contributed to the explosion on Aug. 11, but to carry those lessons forward so that all workers can be safer on the job,” Hall said.
The CSB continues to investigate the cause of the gas release and is reviewing U.S. Steel’s use of cast iron components in the coke ovens, maintenance policies, and safety management procedures.
The Clairton Coke Works have a history of maintenance issues, explosions and environmental violations. The plant is among the largest sources of pollution in Allegheny County.
The coke works was acquired by Nippon Steel this summer when the Japanese steelmaker bought U.S. Steel.
