Definition: Actuators that use compressed air as their working fluid are pneumatic. Pneumatic actuator use pressurized air as an input and transform it into mechanical motion.
Mainly, pneumatic actuators are devices that change the pressure obtained by compressing air into mechanical energy.
Introduction
An actuator is a device employed in a control system that acts on the control signal received from the controller and generates an equivalent signal to drive the plant.
It is not necessary that the signal produced by the controller can drive the plant every time. This is why actuators are use.
Operating Principle
Pneumatic technology is concerned with the behavior of compressed air. A system based on pneumatics uses air as the medium for operation.
The pneumatic actuator works by converting the pressurized air it receives into displacement. The two primary components of these actuators are pistons and diaphragms.
The two units create the motive force from the supplied air in this type of actuator. To put it simply, airpower is use to move the actuator.
Two common types of pneumatic actuators are:
- Linear and
- Rotatory
Pneumatic actuators are classified based on the type of motion they produce. Pneumatic actuators that generate linear motion are describe as linear pneumatic actuators. When the conversion from air to motion is rotational. It is said to be a rotatory pneumatic actuator.
Working of Pneumatic Actuator
We discussed in the previous section that a pneumatic actuator converts energy from a pressurized fluid into mechanical motion or action.
Here are the major components of the pneumatic system:
- Flow Control Valve
- Diaphragm
- Compressor
- Storage Reservoir
- Spring
We already know that here the fluid energy is convert into mechanical energy for driving the system. As shown above, the fresh air is compress by the compressor and stored in the storage reservoir.
A flow control valve regulates the direction, rate, and pressure of the flow of fluid. By carrying the air from one location to another. The spring unit provides a return stroke to the piston.
Details
- In the absence of air supply, the control valve remains open, and the diaphragm is pulled upward by the spring.
the air is drawn from the atmosphere, however, it is filtered by a filter and provided to the compressor. Now, the compressor compresses the air, causing the level of pressure to increase.
As the pressure of the air increases, its temperature also rises. To keep the temperature in a moderate range, the air cooler is use.
- So that the pressure level can be maintained, the pressurized air is now stored in a storage reservoir. The pressurized air inside the system also exerts a force on the actuator’s diaphragm. When the force due to pressurized air overcomes the force of the spring that keeps the diaphragm at the top. The diaphragm will move downward, closing the control valve.
Increasing the supply air pressure causes the diaphragm to continuously move downward, closing the control valve at a certain point.
When the supply pressure decreases, the force due to the diaphragm’s spring then overcomes the force of the supplied pressure. A motion in the upward direction of the diaphragm opens the control valve.
- The position of the control valve depends on the air pressure. So, the opening and closing of the control valve are related to the movement of the diaphragm as well as the air pressure.
Our understanding is that actuators are present after controllers that provide a signal for the desired action to occur. Depending on the control signal, the air pressure changes. Which simultaneously changes the position of the control valve.
Consequently, the assembly inside the actuator responds to the received control signal and drives the process.
Advantages
- Most pneumatic actuators can operate in a wide temperature range, generally ranging from 0 to 200 °C.
- It is easier to construct and requires less maintenance.
- It is fire and explosion-proof.
- Pneumatic actuators are lightweight and less expensive.
Disadvantages
- The pneumatic actuator delivers less output power than the hydraulic actuator.
- Due to the use of air as the fluid, the internal machine parts are not lubricate.
- The output produced in low-velocity operations is somewhat less accurate.
- These are most effective when used with specific applications.
As a result of the above discussion about pneumatic actuators. It can be concluded that their use in the control system provides the signal which is sent to the plant to get the desired output.
With the movement of the diaphragm, the position of the control valve corresponds to the mechanical motion it produces.
Aira Euro Automation is a leading manufacturer of Pneumatic Actuator in India. We, offer many types of actuators for the different valves as per the size and customer requirement. We have low to high torque actuators.
