The primary bushings of main intake valve in Huizhou Pumped Storage Power Station were found damaged in less than a year after the commercial operation. The site inspections showed that the self-lubricating material of the inlet valve bushing fell off and was jammed into the valve trunnion which caused the inlet valve cannot be opened normally. Through the forces analysis under all the different operation conditions

it was found that the bushing bore the largest force in its static state

which indicated that

main inlet valve involved in the transition regulation was irrelevant to the bushing damage. The manufacturing defects were confirmed to be the main cause of the fallen self-lubricating material. In one year after the replacement of the new type bushings

all the operation conditions of the inlet valve were normal and stable

which further proved that the inlet valve involved in the transition regulation had nothing to do with the damage of primary bushing.