US Steel probes cause of blast
Firm suggests gas valve failure may have lead to deadly explosion
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HARRISBURG -- Preparations for a routine maintenance task may have led to an explosion at a U.S. Steel coal-processing plant near Pittsburgh that left two dead and sent 10 to hospitals, the company said Friday.
U.S. Steel said it developed the information, along with other investigators, from reviewing video footage and interviewing employees.
That has suggested to them that the explosion happened when workers were flushing a gas valve in preparation for a routine planned maintenance task, the company said.
The explosion, which heavily damaged part of the sprawling facility, started around a set of ovens where coal is baked to 1,200 degrees Fahrenheit into a more efficient carbon fuel called coke, a key component in steelmaking. A byproduct of processing the coal is a combustible gas called coke oven gas, made up of a lethal mix of methane, carbon dioxide and carbon monoxide.
"Pressure built inside the valve, leading to valve failure and coke oven gas filling the area and ultimately exploding when finding an ignition source," U.S. Steel said.
U.S. Steel didn't say why pressure built inside the valve or what was the ignition source. It said the investigation is in the early stages and that it will provide more information when it can.