Abstract: The hydrogenerator unit No.2 of Qinshan Hydropower Station has commissioned for 1 year, while the machine rotated slightly again after it had been shut off and the air brake had been reverted. This may lead to failure of thrust-bearing because of low speed. By inspecting, it was found that the guide vans’s perpendicular surface, i.e. waterproof surface, was cavitated badly, so the unit was hard to shut down. After analyzing this problem, the methods of resurfacing welding for the cavitated area and then burnishing were implemented. The operation has proved that: the disposal effect is preferable, and the unit’s safety and stability in operation are insured.

Key words: hydrogenerator unit, cavitation erosion, analysis, resurfacing welding, burnish, application effect