Failure analysis and test for motor-driven isolated valve with remote-transmit entity

The failure analysis and treatment for motor-driven isolated valve with remote transmit entity was done in a pressurized water nuclear power station. It was found that the immediate cause of the abruption of clutch coupling brace was the impact loads by the repeated start and stop of the motor. The microscopic test and the valve performance curve test in field found that the root cause was the mismatch between the motor and the actuating mechanism. The feasibility of increasing the driving moment or decreasing the innocent resistance was studied theoretically and verified in field. It found that, when the output rotational speed of the driven motor decreased by 50%, the average friction force decreased by 30% during the isolated valve acting; when the gland tightening force decreased by 50%, the average friction force decreased by 50% during the isolated valve acting. (authors)