Inspection Detail

Inspection: 300571171 - Madison Gas And Electric Company

Inspection Information - Office: Madison Area Office

Investigation Summary

Employee #1 was training Employee #2 as a turbine operator at an electric power generation plant. The turbines the employees were working with were cooled by hydrogen. The system circulated oil to cool the bearings on the turbine, and the oil pressure was designed to prevent hydrogen from flowing into the oil filtering system. Three pumps maintained oil pressure. Two of them were electric pumps; the backup pump was steam powered. The 480-volt circuits supplying power to one section of the plant opened, which caused one of the boilers to shut down. In response, the two employees initiated shut down procedures for the associated turbine (turbine #6). Employee #1 noticed that steam was going into an area that could damage the system. Employees #1 and #2 closed the closest steam valve, which was a main line to the area, and then went to shut off steam to the individual pumps where they suspected that damage could occur. As they were returning to turbine #6, they were called to help shut down turbine #5. After a short time helping on that job, they returned to finish the shutdown of turbine #6. Another operator noticed the lack of oil pressure and asked Employee #1 about the problem. Employee #1 realized that the 480-volt pumps were not energized. When he had closed the main steam valve, the steam pump had also stopped. The steam was immediately turned on, and oil pressure was restored. Employees #1 and #2 then went down to the oil tank and filter to close some valves and prevent oil from overflowing. Because oil pressure had been lost for a period, hydrogen had flowed into this tank. While the employees were closing the valves, the hydrogen ignited, causing an explosion. Employees #1 and #2 received minor injuries. The explosion blew the cover off the oil filter tank, and the flying cover damaged some utilities on the ceiling. The turbine was also damaged from the lack of oil.

Keywords: BURN, HYDROGEN, EXPLOSION, ELEC UTILITY WORK, OVERHEATED, PROCESS SAFETY, CONTUSION