Unexpected vibration and noise was found on turbine oil supply mains. Through system condition analysis method

the major factors influencing the pressure in turbine oil supply pipes were investigated. The angular momentum conservation method was employed to calculate the minimum stable fluid velocity of check valve at the main oil pump outlet under rated condition. Moreover

the flow characteristics and resistance coefficient change were also analyzed when the valve is in low fluid velocity. The results show that

the swing check valve at low fluid velocity is incompletely open

resulting in unstable oscillation when disturbed by upstream fluids

then the flow resistance coefficient of the valve changes

thus the pressure in the oil supply pipes fluctuates. It proposed that

during the system design and equipment selection

the check valve should be required being stable at the minimum velocity in fully open state

and the corresponding flow coefficient under certain minimum open velocity should be ascertained. This analysis method is suitable to solving the pressure fluctuation problem caused by check valve type selection and pipeline arrangement.