Automation drives productivity in factories, workshops and plants across the UK; you might be surprised how many sophisticated automated systems are powered by the rather unassuming pneumatic actuator.
This is a guide to pneumatic actuators, exploring how they function, their place in the overall system, and why the quality of compressed air supplied to your actuator is so crucial to how well it performs.
What Is a Pneumatic Actuator?
A pneumatic actuator is a mechanical device. It transforms energy from compressed air into controlled mechanical motion. This motion can be a straight-line push/pull action (linear) or a turning action (rotary).
The primary function is to automate processes like clamping, moving, or positioning components. Pneumatic actuators are known for their speed, reliability, and safety.
Converting Air Pressure into Force
The operation of a pneumatic actuator is based on a simple physics principle. It uses a pressure difference to generate force. There is a sealed chamber within the actuator that houses a piston. When compressed air is supplied to one side of the chamber, the pressure on that side rises. The force exerted over the piston area is the pressure within the chamber. This causes the piston to move.
The force generated is calculated using the formula: Force = Pressure × Area. In typical pneumatic actuators in UK systems, the compressed air pressure ranges from 6 to 8 bar (approximately 87-116 psi). This is enough to generate a substantial and controllable force.
The Mechanics of How a Pneumatic Actuator Works
Let’s take a look at a pneumatic actuator. By that, we do not mean to focus solely on this one element. We need to check out the components involved and also the system that supplies them.
Core Components of a Pneumatic Cylinder
A standard pneumatic actuator will have these main parts:
- Barrel: The main body that holds the piston and also the pressure.
- Piston: The disc inserted into the barrel that is used to translate air pressure into linear force.
- Piston Rod: Hardened steel rod attached to the piston to push out the cylinder and use the generated force.
- End Caps: Caps that secure the barrel and have air connection ports for intake and exhaust.
- Seals: Vital for efficiency, as these are the pieces that stop air from escaping past the piston or around the rod.
The Wider Pneumatic System
The performance of an actuator depends entirely on the system that feeds it. Key upstream components include:
- The Air Compressor: The heart of the operation. It produces the high-pressure air that powers the actuator. There are various types of air compressors, including rotary screw and piston models.
- Air Treatment: Compressed air must be clean and dry. Compressed air filters remove harmful particulates and oil from the air. Air dryers remove moisture that can cause corrosion and damage.
- Control Valves: These act as the brain. They direct the flow of compressed air to the actuator to control its movement.
- Piping Network: A system of durable tubing, such as modern aluminium compressed air piping systems, transports air from the compressor to the point of use with minimal pressure loss.
The correct design and installation of these upstream components are essential to maximise actuator efficiency.
Linear and Rotary Actuators
Actuators are classified based on the motion they produce and how they operate.
Linear and Rotary Motion
- Linear Actuators: Create linear motion (push/pull) for precise control. The most common type is for clamping, lifting, and positioning.
- Rotary Actuators: Convert air pressure into rotary motion (torque). Used to automate quarter-turn valves or for positioning/mixing applications.
Single-Acting and Double-Acting
- Single-Acting Actuators: Use compressed air to move the piston in one direction only. A mechanical spring returns the piston to its original position. The primary advantage is a mechanically applied “fail-safe” position in the event of air pressure loss—a key requirement for emergency shutdown valves.
- Double-Acting Actuators: Use compressed air to control movement in both directions. This provides more control over the load but consumes more air per cycle. Leading brands, such as Festo pneumatic drives, offer a wide range of both types.
Applications and Benefits Across UK Industries
Pneumatic actuators are a cornerstone of factory automation due to their unique combination of benefits:
- Safety: Intrinsically safe for hazardous environments (ATEX compliant), as they use air and do not generate sparks.
- Speed: Speedy response times that are ideal for high-cycle applications, such as packaging and sorting.
- Reliability: Their simple, robust design means fewer points of failure, supporting a long service life, even in harsh conditions.
- Cost-Effectiveness: Initial purchase cost is usually lower when compared to electric alternatives.
They are widely used in sectors including:
- Manufacturing & Engineering: Pneumatic actuators power assembly tools, conveyors, and robotics.
- Automotive: Powering welding robots, assembly fixtures, and when applying paint.
- Food & Beverage: Used in packaging lines and filling machines to ensure hygiene is upheld to the highest standard.
- Pharmaceutical: Used in combination with oil-free air compressors to maintain pristine, sterile environments.
- Logistics & Warehousing: Used to power sorting gates, diverters, and automated material handling systems.
Electric and Hydraulic Alternatives
Here’s how pneumatic systems compare to their main alternatives, to help you choose the right actuator technology for your business:
- Pneumatic Actuators are the go-to choice for speed, simplicity, and safety. They excel in rapid, point-to-point movements and are significantly cheaper to purchase. Their use of air makes them inherently safe for explosive environments, where electrical sparks pose a significant risk. Their main disadvantage is their less precise mid-stroke positioning, due to the compressibility of air, adding variability.
- Electric Actuators are renowned for their reliability, precision, and control. They provide highly repeatable positioning, velocity, and force as they are programmable with complex motion profiles. Although they have a higher initial cost, electric actuators are highly energy-efficient. The major downside to electric actuators is their unsuitability for use in hazardous environments. To be used safely in these environments, they must be housed in costly explosion-proof enclosures.
- Hydraulic Actuators are used when superior force and power density are required. They are ideal for these applications due to their use of incompressible oil at extremely high pressures. This makes them suitable for heavy-duty industrial applications, including the lifting of exceptionally heavy loads. However, they are more prone to messy fluid leaks, have higher maintenance needs, and slower cycle speeds than pneumatics.
Meeting UK Compliance and Standards
Operating pneumatic systems in the UK comes with some industry standards and regulations you must follow:
- ATEX Directive: As pneumatic actuators don’t use electricity, they are a common choice for use in atmospheres with explosive risks. This is because of their lack of ignition hazard risk.
- HSE PUWER Regulations: Ensuring pneumatic systems are correctly installed, well-maintained, and inspected regularly.
- ISO 8573-1: A 3-part international standard of compressed air purity classes determined by the presence of particulates, water, and oil. Matching the appropriate class is key to prolonging the life of your actuators and ensuring product integrity.
- Energy Efficiency & Net Zero: A poorly performing pneumatic system with air leaks is using large amounts of energy needlessly. Optimising your system is a small but significant step towards lower running costs, as well as company sustainability and net zero targets.
The Future is Smart: Pneumatics in Industry 4.0
Smart sensors are becoming more prevalent in the next generation of pneumatic actuators. Pneumatic systems, although rugged, require regular maintenance to continue operating effectively. On-board sensors provide real-time feedback on pressure, position, n, and temperature. Empowering operators with this data allows for predictive maintenance, preventing downtime before it occurs. Remote monitoring technology, such as Atlas Copco’s SMARTLINK system, aligns with the connected factory’s objectives of Preventive Maintenance.
Preventative Maintenance Checklist
Scheduled maintenance prolongs the life of pneumatic actuators and your overall system.
- Daily/Weekly Checks:
- Listen for Audible Leaks: Walk the line and listen for the hissing sound of air escaping. A good place to start is at the fittings and actuator seals.
- Drain Filter Bowls: Drain water from filter bowls to prevent it from being transported downstream. Note: Some filter bowls can be drained manually.
- Monthly Checks:
- Verify Air Pressure: Ensure the gauge on the point-of-use regulator is set to the correct pressure for the application.
- Inspect Mounting Hardware: Verify that all bolts and fittings securing the actuator are tight and free from evidence of vibration.
- Quarterly/Annual Checks:
- Replace Filter Elements: Filter elements become clogged over time. Replace filter elements as recommended by the manufacturer to ensure proper airflow and filtration.
- Test Safety Functions: If the actuator is part of a safety system, test its function to ensure it is operating correctly.
- Inspect Rods and Seals: Inspect exposed piston rods for evidence of scoring, corrosion, or damage. Inspect external seals for evidence of cracking or wear.
Identifying Common Problems
If your actuator is moving slowly or appears to be acting erratically, there are several common causes that could be to blame. These problems can usually be found upstream on your pneumatic system, such as a plugged filter, an incorrectly adjusted regulator, or a leak in your system.
The Unbreakable Link: Your Compressor and Your Actuators
The performance of every pneumatic actuator in your facility is directly connected to the health of your compressed air system. If your air compressor is well-maintained and of high quality, providing clean, dry air, your automated equipment will function reliably and efficiently.
J.L. Leach is an experienced Atlas Copco Premier Distributor with over 80 years of experience in the industry. We have the expertise to help with the design, installation, and maintenance of your complete pneumatic system. If you are having problems with actuator performance, high energy bills, or production downtime, the culprit may be your compressed air supply. Call J Ll Leach today to schedule a compressed air audit, leak survey, or a custom maintenance plan and ensure your pneumatic actuators perform optimally.