Operators in a powdered metals production facility heard a hissing noise near one of the plant furnaces and determined that it was a gas leak in the trench below the furnaces. The trench carried hydrogen, nitrogen, and cooling water runoff pipes as well as a vent pipe for the furnaces.

Maintenance personnel presumed that the leak was nonflammable nitrogen because there had recently been a nitrogen piping leak elsewhere in the plant. Using the plant's overhead crane, they removed some of the heavy trench covers. They determined that the leak was in an area that the crane could not reach, so they brought in a forklift with a chain to remove the trench covers in that area.

Eyewitnesses stated that as the first trench cover was wrenched from its position by the forklift view more

The hydrogen feed system for the furnaces inside a pit furnace developed a leak. The leak was on the hydrogen dryer inside a shack attached to a building. The leak vented 200 psig hydrogen into the shack. The hydrogen low-pressure alarm sounded. No furnace operators were present at the time. An estimated 10,000 standard cubic feet of hydrogen vented. T

he hydrogen release was caused by a failure of an elastomeric pressure seal on the body of a particulate filter located in the hydrogen supply circuit of the Pit Furnace. After a similar event a month earlier, the cause was identified as a simple seal failure; however an independent engineering review after the present incident showed the cause to be system overpressure, caused by regulator failure.