Application of diagnostics to determine operational readiness of aged motor operated valves

Oak Ridge National Laboratory (ORNL) has been carrying out an aging assessment of motor operated valves (MOVs) with the primary objective of recommending diagnostic methods for detecting and trending aging. As a result of experimental investigations at ORNL, it was discovered that the motor current during a valve stroke was a very useful diagnostic parameter for detecting and trending many MOV drive train load variations. The motor current signatures were analyzed at four levels: mean value for a stroke, gross trends during a stroke, transients, and noise frequency spectra. Examples illustrating the use of this technique are presented. The use of motor current signature analysis was also shown to apply to other electric motor driven equipment. Future work will include developing a data base of MOV diagnostics, including criteria for determining the extent of degradation and application of the technique to other LWR motor driven safety equipment. (author). 4 refs, 9 figs