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.
The manager in charge acknowledged that, while he made relatively recent modifications to the high-pressure gas storage side of the system and had directed a major rebuilding of various units, the moderate-pressure interconnecting system (the source of the problem) remained essentially in its original condition. He acknowledged waiting for safety definitions in the Safety Manual and thereby letting improvements be delayed. He supported the decision to have an independent engineering review after the second incident, pointing out that this essential step assisted in defining the actual root cause and led to more constructive and long-range corrective actions.