In this guide, we talk about what a pneumatic actuator is in detail, including its working principle and various industry applications, as well as its advantages and limitations, to help you decide if it’s the right actuator type for your project.
1. What is a Pneumatic Actuator?
A pneumatic actuator is a mechanical device that converts energy from compressed air into either linear or rotary mechanical motion. The way it’s configured allows you to handle heavy-duty tasks, such as opening or closing valves, operating dampers, and moving conveyor belts.
You may have heard of its counterpart, the electric actuator, which uses electricity as its power source and is just as powerful. However, electricity is a fire hazard, making it unsuitable in explosive or flammable environments. In this regard, pneumatic actuators have the upper hand.
Beyond safety, pneumatic actuators are widely chosen for their cost-effectiveness (especially if your facility already has a compressed air system), high-speed operation, and durability, which we’ll explore in more detail later.
For now, let’s look at what’s actually happening when a pneumatic actuator turns compressed air into motion, and how it’s able to handle jobs requiring a high-force output.
2. How Does a Pneumatic Actuator Work?
Being essentially a pneumatic system, a pneumatic actuator is fueled by compressed air, which enters and fills the air chamber entirely. This creates pressure difference strong enough to move the piston (or vane), which then transfers the motion to mechanical linkages, allowing the actuator to perform heavy-duty tasks.
Components of Pneumatic Actuators
Let’s have a more in-depth look into the components that allow pneumatic actuators to function as intended:
Air Compressor
The air compressor is not technically part of the pneumatic actuator itself, but rather, a part of the broader pneumatic system – and a vital one, as it provides the compressed air supply to the actuator through supply lines.
Control Valve
Like the air compressor, the control valve is separate and, thus, not housed inside the actuator itself. However, it plays a critical role in regulating airflow and directing it to specific parts of the actuator to successfully initiate movement in the intended direction (forward or backward).
Air Chamber or Cylinder
This part is where compressed air enters (on one side) and builds up. Once the pressure reaches the required levels, it forces the piston or vane to move. The more compressed the air (the higher the pressure), the greater the force exerted.
Piston or Vane
Earlier, it was mentioned how pneumatic actuators can cause two types of motion: linear motion and rotary motion.
A piston is required where a linear motion is intended (i.e. linear actuators). Where rotational motion is required, a vane is used (i.e. rotary actuators).
Mechanical Linkages
Mechanical linkages connect either the piston or the vane to the equipment or system that needs to be moved so as to perform the intended task. That said, mechanical linkages aren’t inherently a part of the actuator, but rather, of the pneumatic system as a whole.
Exhaust Port
The exhaust port is where compressed air is released after generating movement has completed its work.
Spring
In a single-acting actuator mechanism (more on this later), particularly in linear actuators, the spring pushes the piston back to its original position (i.e. spring return action). This mechanism is often used for fail-safe or default-position applications.
Control Mechanisms
Control mechanisms simply refer to whether the actuator is designed as single-acting or double-acting.
A single-acting actuator uses compressed air to move the piston or vane in one direction. As mentioned earlier, a spring mechanism returns the piston/vane to its original position. So, it only requires air pressure on one side of the piston.
Double acting actuators, on the other hand, use compressed air to move the piston or vane in both directions. Here’s how it works: One side of the piston is pressurized to move it in one direction, the air is vented, and then the opposite side is pressurized to move it back.
This is controlled by a control valve that directs the air to either side of the actuator.
3. Types of Pneumatic Actuators
Linear Pneumatic Actuators
Linear pneumatic actuators create linear motion necessary for lifting, pushing, or pulling applications.
There are two types of linear pneumatic actuators: piston-style actuators and spring-diaphragm actuators.
The piston-style actuator uses a piston inside a cylinder to generate linear motion. Compressed air enters on one side of the piston, causing it to move back and forth. Below is a rundown of its characteristics:
- Suited for heavy-duty applications that require precise control and consistent motion
- Requires more space compared to other actuator types
- May be slower than rotary actuators in some cases
Spring-diaphragm actuators use a flexible diaphragm (or spring-loaded diaphragm) that moves when air pressure is applied. The spring assists in returning the diaphragm to its original position. Some of its characteristics include the following:
- More compact and lighter compared to piston-style actuators
- Suited for fail-safe systems
- Has a stroke length that’s shorter than that of a piston-style actuator
Rotary Pneumatic Actuators
If that’s the case for linear actuators, what is a pneumatic rotary actuator used for? As the name suggests, it’s used where rotational movements are required, such as in ball or butterfly valve applications, turntables, and machinery requiring angle adjustments.
Vane actuators and rack-and-pinion actuators are the two types of pneumatic actuator that converts compressed air flow into rotary mechanical power.
A vane actuator uses a rotor with vanes that are pushed by compressed air. As air enters the actuator, it pushes the vanes, causing the rotor to turn. These are some of its characteristics:
- Offers high torque output for rotational motion
- Smaller and more compact than a rack-and-pinion actuator
- Highly sensitive to air pressure variations
Rack-and-pinion actuators, as their name suggests, use a rack (a straight bar) and pinion (a gear) to convert the linear motion of compressed air into rotational motion. The air pushes against the piston, which moves the rack, turning the pinion. Characteristics include the following:
- Provide higher torque capacity than vane actuators
- Bulkier in design, and thus, require more space
- Generally has more moving parts, making them more susceptible to wear and tear
Single-Acting vs Double-Acting Actuators
As discussed earlier, single-acting actuators move the piston or vane in one direction and utilize a spring (or other return mechanism) to return the piston/vane back to its original position. Some of its characteristics include the following:
- It has a simpler design, making it less expensive and easier to maintain.
- It’s more compact, taking up less space than double-acting actuators.
- The spring mechanism provides a fail-safe return to the default position.
On the other hand, double acting actuators require compressed air to move in both directions, moving the piston or vane in the same way. Their characteristics include the following:
- They can generate a higher force output compared to single-acting actuators.
- They have a more complex design, making them more expensive.
- They require constant air supply to perform forward and return movements.
4. Applications of Pneumatic Actuators
Many times, we’ve mentioned how pneumatic actuators allow us to carry out the hardest, most heavy-duty tasks. But where are pneumatic actuators used in the real word?
Valve Control in Industrial Processes
Pneumatic actuators are most commonly used for valve control in industries like oil & gas, water treatment, and chemical processing.
The pneumatic actuator is connected to a valve (e.g. ball, butterfly, or globe valve). Once the actuator is activated, it can fully open or close the valve – or in some cases, partially open it to enable throttling and precise control of liquids, gases, or steam within pipelines.
Automation in Manufacturing and Assembly Lines
In manufacturing and automotive industries, pneumatic actuators are used to automate various tasks such as moving parts, sorting materials, or positioning tools.
They can move assembly arms, conveyors, or grippers at high speed and efficiency over lengthy operating periods.
Control Systems in Hazardous Environments
Pneumatic actuators are prevalent in hazardous environments such as chemical plants and oil refineries where there’s a high risk of fire or explosion. This is because it uses compressed air instead of electricity, which is a fire hazard.
5. Advantages of Pneumatic Actuators
To summarize why industries choose pneumatic actuators for their operations, here’s a list of advantages:
High Speed and Quick Response Time
The main factor behind this advantage is the immediate availability of compressed air.
Additionally, unlike an electric actuator that requires more time to power up or move, a pneumatic actuator can instantly convert compressed air into mechanical motion. Arguably, there’s also minimal internal resistance due to the absence of motors or electrical components.
Highly Efficient
Pneumatic actuators can store compressed air in a reservoir, which allows it to continue performing rapid, repeatable actions over extended periods before needing to recharge the air supply
Cost-Effectiveness
Pneumatic actuators are cost-effective for two reasons. First, they typically have a lower upfront cost, since compressed air systems are usually already in place in many industrial settings.
Secondly, pneumatic actuators generally have a longer operational life, often outlasting their electric counterparts. This is mainly due to the simplicity of design, which means less wear and tear and fewer maintenance requirements.
6. Limitations of Pneumatic Actuators
Of course, pneumatic actuators are not ones without drawbacks.
When your air supply is not good and fluctuations occur more often than expected, pneumatic actuators have a hard time achieving and maintaining incremental movements.
Additionally, noise can be an issue when operating with pneumatic actuators since the compressor can be loud. This can be bothersome for workers or professionals in nearby office spaces.
Learn More About Pneumatic Actuators
As you can see, pneumatic actuators come with a lot of advantages that make them suitable for industrial automation and heavy-duty work. To know more about how it fares relative to other actuator types, check out our guide on pneumatic actuator vs electromechanical actuator.
Better yet, give us a call and let us discuss the right actuator for your specific application.
Reference
How Pneumatic Actuators Work and Advantages of Pneumatic Actuators
