A valve actuator is a mechanism deployed to open and close a valve manually or automatically using fluid pressure or electric signals. In hydraulic actuated valves, fluid pressure is converted into motion on linear or quarter-turn (rotary) valves. This mechanism is usually found in industrial processes where high speed and a large force is required to operate the valve.
Working principle of hydraulic actuators
The most common type of hydraulic actuator is the piston type, which consists of a piston, cylinder, spring, stem, and a hydraulic supply and return line. An incompressible fluid is used in the system so that the pressure applied can be instantly transmitted to the member attached to it.
A pump fills the cylinder with this highly incompressible fluid that forces the piston to move. When the pressure increases, the piston moves linearly inside the cylinder and the speed of this movement can be modulated by changing the flow rate of the fluid.
To open the valve, the piston can be returned to its original position either by spring-back force or by supplying fluid pressure to the opposite direction with the help of another pump. As a result, hydraulic actuated valves come with several accompanying components like fluid reservoirs, heat exchangers, release equipment, etc.
Advantages of hydraulic actuators
The ability of hydraulics to deliver high force is one of the primary reasons why they are so popular in industrial process control. Even smaller cylinders like 3-inch bores can deliver over 66,700 kN force easily.
Moreover, hydraulic actuated valves are typically used in harsh conditions since they are durable and reliable with a robust design. They are also quite easy to use due to their simple construction, making them widely acceptable in several situations.
