May 1, 2009

Lessons Learned from a Hydrogen Explosion

Angela Neville, JD

Reducing the Risk

After the incident, AEP took corrective actions to guard against future problems related to the handling of hydrogen at the plant.

"Muskingum River Power Plant employees and employees of plants owned by Ohio Power Co. and its sister corporations (AEP employees) took immediate action to prevent recurrence," McCullough said. "The remaining relief devices were verified as being the correct design and constructed with fusible plugs."

The hydrogen vendor was restricted to delivering only 2,100-psi hydrogen to the site (versus the typical 2,400 psi), and the vendors’ employees are now under observation by AEP employees using a defined procedure, the Job Hazard Analysis and Job Safety Assessment Checklist, McCullough explained.

AEP has made other changes in plant operations to further ensure that no more hazardous incidents occur at the facility. "In addition to the procedure changes, the hydrogen system was redesigned and rebuilt to eliminate the use of rupture disc – style relief devices," he said. "Now a relief valve system is used that will reset once pressures have been reduced. The cylinders have been moved away from spaces occupied by people, and the structure is protected from vehicle encroachment and ignition sources."

Key Safety Lessons

In September 2005, a working group with CIGRE (International Council on Large Electric Systems) estimated that there may be more than 40,000 hydrogen-cooled generators in service around the world. Despite the large number of systems that use pressurized hydrogen to cool generators, for the most part, few incidents or problems occur. However, given the inherently hazardous properties of hydrogen, plant staff working with this flammable material need to regularly review both the equipment and handling procedures to verify that there are no problems.

This case history is intended to be helpful to personnel who deal with hydrogen used to cool the generators at their power plants. Proper management, including safe equipment design and construction and correct procedures for handling hazardous materials, can ensure safe results in dealing with this useful substance.
—Angela Neville, JD, is POWER’s senior editor.