Selection of motor operated valves (MOV'S) for nuclear power plant application

Nuclear power plants are reviewed and qualified by the Nuclear Regulatory Commission (NRC) to operate only if it is certified that every safety related installed equipment is in good standing and operative. They should be able to perform the functions for which they are designed whenever they are called upon to do so, especially in cases of nuclear emergencies. Motor operated valves (MOVs) are one of such very important equipment. They are used to seat and unseat valves which perform safety related duties in nuclear power plants. Most of the failure of the valves reported are due to the incorrect sizing and selection of the actuator motor. The problem is that the valves are mechanical equipment with their associated mechanical terminology, yet the electrical engineer is more often than not called upon to size and select the appropriate motor required to drive the valve in order to perform the desired functions. This paper presents a background on motor operated valves in order-to provide a starting point for electrical engineers stepping freshly into this field. It reviews the procedure to select the correct size of the actuator motor to match a given application. Examples of typical selection procedures are provided.