Let us first try to figure out how the valve actuator actually works. So what valve actuators do is they mount on the valve and in response to the signal, the valve then moves to the desired position using the outside power source. Another thing that you need to keep in mind is that while you finally decide to go ahead with a valve actuator, it will increase uptime, reduce maintenance costs, and also increase plant safety.

Most valve actuators come fully prepared, properly oiled and operate best with instrument-quality air. You can also package them with position sensing equipment, digital communication capacity and even motor protection.

Now let us try to understand the valve method of control and function.

Why do you think you need to know more about this? This is because both valve motion and operation style are crucial specifications that you must consider while you are selecting valve actuators.

So what is the valve method of control?

First, there are rotary motion valves like a plug, ball, and butterfly valves; they rotate a quarter-turn or more from open to close. Then comes linear motion valves, like a globe, gate, diaphragm, angle-style valve, and pinch. So they come with a sliding stem design that pushes the closure element open or closed. However, the valve stem may rise during rotation or may rise even without it.

Valve Function

Valve function can be bifurcated into:

First comes, start/stop valves, they are also known as on/off or isolation devices, what it does is, it limits actuator motion to preset open and closed positions.

Second, throttling or control devices, so it provides a controllable motion that means valves can be throttled as the need be. So with this type of actuator, you can pair it with a positioner which will help the actuator to move to its required position accurately.

Actuation Method

There are an array of valve actuators that are present such as manual, electric, pneumatic, and hydraulic.

1) First let us talk about manual valve actuators; they do not require an outside power source. So basically with the help of a handwheel or level, it drives a series of gears whose ratio results in a higher output torque when you compare it to input (manual) torque.

2) Single-phase or three-phase alternating current (AC) or direct current (DC) motors are used in an electric valve actuator so that it can drive a combination of gears to build the required torque level.

3) Air pressure is converted into linear or rotary motion by adjusting the valve position, carried out by the pneumatic valve actuators.

Actuator Specifications

The following are the specifications for rotary and linear valve actuators.

Rotary Actuator Specifications

Rotary motion or torque is produced by rotary actuators. In this, the mechanical appliance generates motion in one direction to cause rotation. Then comes the electrical versions of the rotary actuator which continuously rotate, on the other hand, servo motors are used to move the actuator to a fixed angular position.

Rack and pinion actuators

Now, this consists of housing to support the pinion; it is majorly driven by a rack that consists of cylinder pistons on the ends. The racks are available in single, double, or multiple designs. If you look at them together, it’s overall efficiency averages about 85-90%. Both of them together can cover a variety of torque outputs and rotation range from a few degrees to five revolutions or more. 

In conclusion, we would like to hope that this article gave you more insights towards the valve actuator and will help make a decision.