Surprised at hearing that statement? Often industrial valve users have connected gate valve operation with multi-turn electric actuators, not realizing that linear pneumatic or hydraulic valve actuators have features that can make them preferred for rising stem valves. This is especially true when faster stroke speed, mechanical failure position, precision, and higher thrusts are required.
What are Linear Actuators?
Linear actuators have a simple design that adds to their reliability. Basically its construction has only one moving part, a piston operating in a cylinder. The concept has been working successfully for more than 200 years on steam engines. Even its adaption to a gate valve from a handwheel operation is easy. Once the drive nut and handwheel come off exposing the stem, a coupling connects the stem to a piston rod for direct linear operation. Pretty simple and straightforward.
Functions of Linear Actuators
Linear actuators provide thrust rather than torque. The cylinder size is a function of the valve thrust and the available supply pressure (pressure x area = force). As the required thrust increases so does the cylinder size. To accurately calculate the actuator’s price, it is important to specify thrust based on actual design conditions in order to correctly determine the required cylinder diameter, a major price determinant.
The linear actuator has proven itself in many applications. Its simple yet robust design, compact profile for tight piping runs, reliability of operation, and adaptability to hydraulic or pneumatic power sources, make it a very viable choice for use with gate or other rising stem valves.
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