Motor-operated valves: Implementing predictive maintenance

The motor operator maintenance program at the Duane Arnold Energy Center (DAEC) involves predictive and preventive maintenance. The primary objectives of this program are to reduce unplanned corrective maintenance and to achieve and maintain a high level of motor operator reliability, regardless of plant operating conditions. Preventive maintenance is the firs step in reducing unplanned corrective maintenance. The second step in achieving and maintaining a high level of reliability under any operating conditions may require some additional information. In this regard, Iowa Electric Light and Power Company will be determining which factors change a motor operator's performance over time and determining how motor operator performance will change from cold static test conditions to normal on-line operating conditions. The DAEC will begin on-line diagnostic testing in April of 1989 to determine the effect on motor operator performance of changing from the cold static test conditions. The diagnostic system uses a yoke-mounted force sensor. After initial sensor installation, which is performed during a system downtime, diagnostic testing is set up without removing the motor operator from service. This allows for all test data to be gathered on a normal stroke of the valve during the surveillance test. The authors expect to be able to detect and identify subtle changes in motor operator performance and to use these as the bases for their predictive maintenance program