Electric actuators for valve control limit torque
Limitorque SMB actuators from Flowserve Corp., Irving, Tex. (flowserve.com), have been used for over 40 years in almost every kind of heavy-duty industrial application, and can be found in every nuclearpower installation in the U.S. Flowserve now provides these actuators with 10-year warranties for standard commercial applications, a new benchmark in the flowcontrol industry. The actuators deliver up to 60,000 lb-ft of torque and thrusts to 500,000 lb. SMB actuators feature rugged cast-iron housings, and can be built in weatherproof, explosionproof, or submersible constructions. Nuclear constructions are also available. The actuators feature double-reduction gear sets (helical and worm) and are available in several configurations. A hammerblow feature lets the motor reach full speed before the load is engaged, enabling the actuator to apply appropriate force to the valve shaft. Automatic torque limiting deenergizes the motor in case of obstructions to prevent valve damage. In addition, geared limit switches control valve travel during opening and closing operation of the valve.