How Does An Pneumatic Actuator Work? | An-Overview

A pneumatic actuator is a mechanical equipment that transforms energy into mechanical movement, usually in compressed air. These actuators have various names, such as air actuators, air cylinders, pneumatic actuators, etc., and the working of all these actuators is the same.

An actuator consists of ports, valves, cylinders, or pistons that can transform energy into rotary or linear mechanical movements. This depends on either the application uses a pneumatic linear actuator or a rotary actuator.

Linear actuators work well with angle seat control valves for high steam and temperature applications. In contrast, the pneumatic rotary actuator works well with quarter-turn valves depending on the application specification.

Pneumatic actuators have high reliability, efficiency, and safety source for motion control. These are most suitable for repeatedly closing and opening valves and other industrial functions where electricity can produce ignition or fire hazards. In chemical and manufacturing activities, actuators are widely used to control valves that control the movement of liquids.

Below given figure shows a simplified diagram of the pneumatic actuator. It works with the combined action of spring force and air. An actuator sets the position of a shut-off valve by conveying its movement to the valve stem.

pneumatic actuator

A rubber diaphragm divides the actuator casing into two air chambers. The top chamber gets air due to the opening in the upper part of the casing.

The lower chamber has a spring that presses the diaphragm in contrast to a mechanical stop in the top chamber. Lastly, a local gauge connects with the valve stem to display the valve position.

The valve position controls by changing the inlet air pressure in the top chamber. This process changes the force on the top of the diaphragm.

How does a pneumatic actuator work?

A pneumatic actuator relies on some kinds of compressed gas or air to generate the pressure into the pressure chamber. When the required pressure level exceeds outside the chamber compared to atmospheric pressure, a controlled motion of the gear or piston occurs. This can be done in the form of circular or linear mechanical movements.

These actuators are suitable for different types of applications and can be used in a variety of industries. The most common uses of these actuators are:

  • Aviation.
  • Railway applications
  • Packaging and production machines
  • Air compressor
  • Combustible automobile engines

Types of Pneumatic Actuators

Pneumatic actuator has many types, but the most basic types are given below:

1) Linear Actuator

A linear actuator is an actuator that converts the rotary motion of a motor into a straight or linear-pull/push motion. These actuators are perfect for all applications that require a few pounds of force to tilt, lift, pull or push. When you want clean, safe, and simple motion with precise precision and smooth motion control, then the electric linear actuators are the recommended solution. In 1979, LINAK made the first electric linear actuator and has been a leader in the linear motion industry ever since.

Linear actuator

Linear actuators are used in dampers and valves, industrial machines and machine tools, computer peripherals (like printers and hard drives), and in numerous places where linear motion is an important factor. A pneumatic or hydraulic cylinder essentially creates a linear movement. Many other methods use to produce linear motion from a rotatory motor.

2) Rotary Actuator 

A rotary actuator generates rotatory torque or motion. The simplest actuators are purely mechanical, where linear movement in one direction causes rotation. The most common actuators are electrical actuators. Others can be operated hydraulically or pneumatically or may also use the energy amassed in the springs.

The actuator movement can be continuous rotation (like a motor) or motion to a fixed angular position (like a stepper motor or servomotor). Another type of torque motor does not essentially generate any rotation but only produces a precise torque. This torque causes a rotation or is offset by a specific reverse torque.

rotary actuator

If conventional cylinder assembly is unworkable due to movement, weight, or space requirements, a rotary actuator can use to rotate the joint. This actuator can mount directly on the device joints without occupying the long strokes required for the cylinder. Electromechanical rotary actuator designs to move weights in angular units with extremely high positioning accuracy and reproducibility. All rotary actuators allow rotation up to 360 degrees, but many designs can allow continuous rotation in multiples of 360 degrees.

Advantages of Pneumatic Actuators

These actuators are perfect for multipurpose applications, including applications that can be used in potentially explosive atmospheres.

1) Powerful force and speed of motion:

When pneumatic actuators use for linear motion control uses, these provide higher forces and faster movement speeds. It depends on the use of flow rate and air pressure in the equipment.

2) High durability:

Pneumatic actuator doesn’t create overheating problems, regardless of the overuse of pneumatic actuator. Compared to other equipment, it can withstand a certain pressure to be used for a long time.

3) High reliability:

In terms of functionality, pneumatic actuators are considered highly reliable. This is mainly due to the advanced controls that can convert gas into energy. As mentioned above, the pneumatic actuator has high durability, so it has high standards of performance and a very long life span.

4) Clean technology:

These actuators are the recommended devices for hygienic applications. This depends a lot on the use of air instead of liquid. This compressed air contains no hazardous chemicals and protects your application from contamination. Therefore, pneumatic actuators are very important in the beverage, food, and pharmaceutical industries.

5) Inexpensive:

Pneumatic actuators are often viewed as a low-cost option in industrial applications, partly because their installation and maintenance are easy. Obviously, from a practical point of view, the above benefits may be more important, but in today’s economic environment, the cost is still the most important issue for any application administrator.

Disadvantages of Pneumatic Actuator

  • Because of the compressibility and pressure loss of the air, the pneumatic system has less efficiency as compared to other techniques.
  • Limiting the compressor and air supply means operating at lower pressures will result in slower speed and less power.
  • To be truly effective, the size of the pneumatic actuator must be suitable for a particular task. This requires comparative-sized compressors, regulators, and valves which increases the complexity and cost. Therefore, it can’t use in any other application.
  • Even if the air is easy to get into, it can be impure with lubricants or oils, resulting in downtime and maintenance.
  • Industries still have to pay for compressed air, making it useable, and maintenance costs for compressors and pipes.
  • It has low control precision.
  • It has performance difficulties at slow speed

What Is the Difference Between Pneumatic, Electric, and Hydraulic Actuators?

pneumatic vs electric vs hydraulic actuator

Characteristics Electric  Hydraulic  Pneumatic
Power Source It is drive by an electric motor It uses various fluids as a power source. A pneumatic actuator uses compressed air.
Operating Cost Low   High Moderate 
Purchase Cost

High

High Low

 

Maintenance

 

 

Very low maintenance required. High user-maintenance High user-maintenance
Reliability Good Good Excellent
Maintenance Cost Low High Low
Efficiency High  Low  Low 
Utilities Power only option  Pipes, power, Pump Pipes, power, compressors
Environmental Minimal noise level Hydraulic fluid leaks and disposal  High noise levels
Shock Loads Limited capacity to control shock loads Spark-proof, shock-proof, and explosion-proof Capable of controlling shock loads
Peak Power High  Very high  High
Acceleration Moderate  Very high Very high
Load Ratings It can be very high depending on the position and speed. Very high High
Position Accuracy Positioning function and speed control can be synchronized Mid-stroke positioning needs extra components and user support  Very hard to attain position precision
Control The flexibility of the motion control function with the electronic control unit User must Simple valves
Lifetime Long Long Moderate
Speed Moderate Moderate Very High

Pneumatic Actuators Examples:

Put simply; an actuator is a tool that operates or moves to something. Each of us uses at least one actuator in our daily life. Let’s look at some examples of actuators.

1) Door of the grocery store

When you enter into the grocery store, the door will open automatically. It is an actuator that opens the door.

Grocery Store Door

2) Car Seat

You can move the car seat back and forth before driving the car. This is the actuator that moves the seat.

car seat movement

See More:

How Does A Pneumatic System Work

FAQ Section

What Makes an Actuator Move?

We have discussed the motion of the actuator, but we’re not talking about how the actuators move. Let’s start a discussion about it:
An actuator receives energy from a source and uses it to move something. In other words, actuators convert energy into mechanical, physical movement.
A butterfly valve operates by rotating the handwheel coupled to the rotary actuator. In different industrial functions, the handwheel can be replaced by one of three typical power sources that can run rotary actuators.

  1. Pneumatic actuator: It operates by compressed air.
  2. Hydraulic actuator: It uses a variety of fluids as a power source.
  3. Electric actuator: It works with electrical energy.

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