Coke is the fuel used to generate the 2,912-degree heat needed to melt iron ore to make steel. Making coke requires coal to be superheated to nearly 2,000 degrees itself so it becomes pure carbon.

U.S. Steel’s Clairton Coke Works is the largest producer of high-grade metallurgical coke in the Western Hemisphere, the company boasts in the 2023 Mon Valley Works report.

The coke-making process uses terms that are also associated with a battlefield: The coal is kept in a bunker; it’s used to charge superhot ovens that are located in batteries.

Casualties aren’t mentioned in the report. But safety is — and it’s the top priority.

“I end every meeting and every message with the words, ‘Let’s get back to work safely.’ That commitment has never been more important, and we will honor it,” U.S. Steel President and CEO David Burritt said in a statement after Monday’s explosion at the Clairton plant, which left two men dead and 10 injured.

The explosion made fully evident the danger of being near an oven that’s 20 times the temperature that vaporizes water.

Before Monday, the most recent accident was Feb. 5, when a hydraulic issue caused an explosion that hurt two people.

The last fatality was after a Sept. 3, 2009, explosion, according to a review of TribLive and Occupational Health and Safety Administration records.

OSHA officials are investigating Monday’s explosion but did not immediately make further comment. The administration serves as the national employee safety watchdog, and it logs violations and accidents.

Other fatal accidents at U.S. Steel’s Clairton plant include:

• Oct. 21, 1992, when a man was killed by a cable attached to a barge.

• June 24, 1994, when a man was crushed.

• Sept. 14, 1988, when a man was crushed.

No one was killed in a July 14, 2010, explosion, but 20 people were hurt.

The Clairton plant is part of U.S. Steel’s Mon Valley Works, an integrated steelmaking operation that includes the Edgar Thomson Plant in Braddock and the Irvin Plant in West Mifflin. A fourth plant, Fairless, near Philadelphia, serves as a finishing facility.

The Clairton plant is on the west bank of the Monongahela River about 20 miles from Pittsburgh. As the largest coke manufacturing facility in the nation, it has 10 coke oven batteries and produces about 4.3 million tons of coke each year.

It is the only remaining U.S. Steel coke-producing plant in the country. As of 2023, the Clairton facility employed about 1,400 people, according to a U.S. Steel report.

St. Clair Steel Co. built the facility in 1901. U.S. Steel purchased it in 1904.

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