VALVE ACTUATORS Process Controlslimiters de-energize the electric motor when the amount of turning force has reached a specifiedvalue. The turning force normally is greatest when the valve reaches the fully open or fullyclosed position. This feature can also prevent damage to the actuator or valve if the valve bindsin an intermediate position.SummaryThe important information in this chapter is summarized below.Valve Actuator SummaryPneumatic actuators utilize combined air and spring forces for quick accurateresponses for almost any size valve with valve position ranging from 0-100%.Hydraulic actuators use fluid displacement to move a piston in a cylinderpositioning the valve as needed for 0-100% fluid flow. This type actuator isincorporated when a large amount of force is necessary to operate the valve.Solenoid actuators are used on small valves and employ an electromagnet tomove the stem which allows the valve to either be fully open or fully closed.Equipped with limit switches and/or torque limiters, the electric motor actuatorhas the capability of 0-100% control and has not only a motor but also a manualhandwheel, and a clutch and gearbox assembly.end of text.CONCLUDING MATERIALReview activities: Preparing activity:DOE - ANL-W, BNL, EG&G Idaho, DOE - NE-73EG&G Mound, EG&G Rocky Flats, Project Number 6910-0019/2LLNL, LANL, MMES, ORAU, REECo,WHC, WINCO, WEMCO, and WSRC.IC-07 Page 60 Rev. 0
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