The following is a synopsis of information received via facsimile:
On March 18, 2010, Samkwange returned an NH90 Hydramotor to ASCO because the motor was not operating when power was applied. ASCO tested the actuator and found all recorded electrical values to be within specifications, however the output shaft did not have any movement. With the mounting plate removed and the pump activated, it was observed that the shaft was not turning with the rotor.
On November 24, 2010, Diablo Canyon Power Plant returned an NH90 Hydramotor to ASCO because the unit was not attaining its full stroke when a signal was applied. The output shaft would start to stroke, but intermittently stopped and the pumping sound ceased. However, normal operating current was noted which indicated that the motor was still running and that a locked rotor condition was not occurring. Further testing revealed that the rotor core was turning on the shaft.
In both of the above cases, it was determined that the output shaft was undersized.
Corrective Action: All rotor-shaft assemblies in ASCO's inventory as of April 22, 2010 were returned to the supplier to confirm that they met specifications. In addition, a static
torque test has been implemented for all rotor-shaft assemblies of all pump assemblies manufactured by ASCO since December 10, 2010. Also, all rotor-shaft assemblies that were in ASCO's inventory as of December 10, 2010 successfully completed the static
torque test. Finally a static
torque test will be performed on all pump kits in AREVA's inventory before they are supplied to customers.