May 1, 2009

Lessons Learned from a Hydrogen Explosion

Angela Neville, JD

The Explosion

McCullough explained what happened when the explosion occurred on January 8, 2007.

"A hydrogen relief device failed, permitting the contents of the hydrogen tank in question to be relieved and be ignited by an unknown source," he said. "The explosion fatally injured the vendor’s driver and also injured 10 others who had been working nearby. The explosion caused significant damage to the unit’s service building, turbine room, and steam generator building" (Figure 2).

2.    Amid the wreckage. The building housing Muskingum River Power Plant’s Unit 5 was significantly damaged by the explosion that occurred when hydrogen, used to cool generating units at the plant, was being delivered. Courtesy: American Electric Power

McCullough noted that "Ohio Power Co. accident responders and first aid workers responded immediately to the scene to fight the fire and attend to the injured." Local fire department and emergency medical technicians also quickly responded to the incident and assisted with emergency response and evacuation actions (Figures 3 and 4).


3.    Cooling things down. Water from fire hoses sprays on a hydrogen delivery truck and the surrounding area to keep the area cool after the explosion. Courtesy: American Electric Power


4.    A prompt response. A fireman walks through debris near a hydrogen delivery truck after the explosion. The local fire department arrived quickly on the scene to assist the other emergency response teams in fighting the fire and aiding injured workers. Courtesy: American Electric Power

Investigation of the Incident

In the aftermath of the incident at the Muskingum River Power Plant, AEP personnel conducted their own examination into the cause of the explosion. Due to the fatality and the injuries sustained by workers at the facility, the U.S. Occupational Safety and Health Administration (OSHA) also conducted an investigation that included all parties involved in the incident.

"The investigation into this event showed that the relief device was a rupture disc that normally would have been built to relieve pressure to prevent catastrophic failure of the hydrogen tanks," McCullough said. "Normally, the device has a fusible bismuth plug that holds the coin-shaped disc in place until temperatures exceed 180 degrees. The device had been replaced by the hydrogen vendor several months prior, when the vendor was on-site to make repairs related to an apparent leak. The replacement relief device assembly did not have a fusible plug to support the disc."

When the rupture disc failed, the disc, or a piece of fusible plug left in the vent pipe during the replacement several months prior to the explosion, penetrated a bend in the piping, permitting the hydrogen to vent lower down in the area of the tanks as well as up the normal vent path, McCullough explained.

OSHA brought enforcement actions against the involved entities as a result of the findings from its investigation of the incident. Those actions initially consisted of 18 citations, nine each against the hydrogen vendor and Ohio Power Co. After an informal conference, the number of citations against each company was reduced to eight. Most of the citations were directed at the design and construction of the hydrogen system.