Pneumatic actuators turn compressed air into mechanical motion without human intervention. Mechanisms such as a control valve are made to open and close by pushing pressurised air through a cylinder, resulting in linear or rotary movement later in the process.
Compressed air cylinders, pneumatic actuators, and air actuators are all names for the same part. They are widely used across hundreds of industries to automate systematic processes, producing predictable, accurate movements within an industrial production line, oil and gas facility, auto workshop, or other facility.
As a practical example, pneumatic actuators control process valves in a processing facility. These are triggered on/off through the delivery of compressed air to move a piston. The piston’s movement eventually results in valve activation. Air actuators have numerous other applications.
How do Pneumatic Actuators Work?
Pneumatic actuators use compressed air to create movement. When air enters a sealed chamber, it pushes a piston. This moves connected components such as valves or dampers.
Key operational features:
- Basic function: compressed air at 6–8 bar pushes a piston inside a cylinder, creating motion.
- Motion types:
- Linear actuators produce straight-line movement. These are common in packaging lines at McVitie’s factory in Manchester.
- Rotary actuators create a turning motion. The rack-and-pinion type is often used in Sunderland’s automotive plants.
- Control: standard flow regulators adjust speed. Most UK workshops use 1/4″ BSP fittings on the control lines.
- Actuation modes:
- Single-acting actuators use a spring for return movement. Springs typically need replacing every three years.
- Double-acting actuators use air on both sides. These are preferred in Scottish paper mills for their reliability in damp conditions.
- Safety applications: many North Sea platforms use pneumatics where electrical sparks would be dangerous. The control panels need weekly draining during the winter months.
- Monitoring: position sensors can be added. Most British facilities connect these to standard PLCs using 4–20 mA signals.
Pneumatic actuators generally respond faster than electric ones. They work well in dusty environments like Yorkshire grain mills, where electrical components often fail. Maintenance typically involves changing seals and checking for air leaks with soapy water on connections.
Types of Pneumatic Actuators
There are different types of pneumatic actuators. Here are a few examples:
Single-acting actuators: a piston is set into motion in a single direction from its starting point. A spring returns the actuator to its original position. These actuators are highly energy efficient compared to some other types.
Double-acting actuators: the piston receives compressed air on both sides. This allows two directions of movement to activate and return to its original position. No spring is required. Using more compressed air reduces wear and tear on parts.
Rotary pneumatic actuators: instead of linear movement generation, these actuators create rotary motion from compressed air. Applications for these include lifting mechanisms, presses, and more.
As a useful comparison, conveyor belt systems designed for product packaging rely on double-acting actuators to operate bi-directionally when needed. Chemical plants depend on rotary actuators to operate valves, opening and closing them precisely to control flow and pressure levels.
To better understand the actuators available, please discuss this with our team at J LL Leach. Festo-branded pneumatic actuators are highly recommended for many applications.
Advantages of Pneumatic Actuators
Pneumatic actuators provide several practical benefits for industrial use. They deliver quick movement with short cycle times. At the Walkers Crisps factory in Leicester, pneumatic systems operate bag-sealing mechanisms at 120 cycles per minute.
They work well in hazardous areas. Unlike electric motors, pneumatics do not generate sparks. This makes them suitable for the BP refinery in Hull, where flammable vapours are present. The maintenance team replaces actuator seals twice yearly as part of their safety programme.
Their basic design means fewer parts can break. Most pneumatic cylinders contain just a piston, rod, and seals. At Cadbury’s Birmingham plant, maintenance records show pneumatic door actuators typically last 7–9 years before needing replacement.
Key advantages:
- Good power-to-size ratio – a 50 mm bore cylinder produces about 950 N of force at 5 bar pressure.
- Clean operation – no oil leaks to clean up. Food factories in Scotland prefer them for this reason.
- Safety features – single-acting models return to a safe position if air pressure drops. Many Yorkshire textile mills use these on emergency stops.
Pneumatic systems connect easily to standard factory controls. Most UK installations use 6 mm nylon tubing with push-fit connectors. These often develop leaks at the elbows where they connect to machines – a common daily check for engineers at Nissan Sunderland.
Pneumatics cost less than electric options for simple movements. A basic pneumatic cylinder for packaging costs about £85 to £120, while an equivalent electric actuator might cost £350 to £400.
Applications of Pneumatic Actuators
The range of applications for pneumatic actuators is huge. Below are a few of them:
Oil & Gas: offshore drilling platforms and pipelines benefit from their predictable performance and durability in highly changeable environmental conditions.
Manufacturing: automated production lines rely on controlling valves, components moved by pneumatic processes, and connected factory machinery.
Food production: this industry uses pneumatic actuators in wash-down environments, such as wet and cool. Cylindrical, sealed actuators are unaffected.
Other applications: air-fed work tools, pneumatic drill systems, and robotic arms can all use pneumatic actuators.
Limitations of Pneumatic Actuators
There are some downsides or limitations to pneumatic actuators. We detail these below:
Movement precision: high precision movement is better suited to electric actuators, which initiate slower but offer finer control.
Noise rating: electric actuators are quieter in operation compared to air-fed versions.
Energy efficiency: operating a pneumatic actuator continuously requires considerable compressed air. Air systems must be sufficiently robust to support this demand.
Operating costs are greater: a compressed air system is required, including separate air dryers, to manage airflow requirements.
Clean compressed air requirement: an uninterrupted supply of filtered air is essential. Compressed air production is slowed, and performance is affected should the ambient air supply become compromised.
How to Choose the Right Pneumatic Actuator
Our basic suggestions for choosing the right pneumatic actuator are as follows:
Measure the force required to be generated by the actuator. It must be more than sufficient, with a margin of safety, to control or move the required load.
A pneumatic actuator either creates a rotary or a linear motion. This is specific to the type of actuator and should not be considered interchangeable.
The degree of precision with generated movement is an essential consideration. Electric actuators offer higher precision than air-fed solutions. Electrical actuators are the better option when near-exacting control of force and/or speed is required.
What internal environment will the actuator be used within? Wash-down environments in food production are specific. Corrosive or high-temperature/high-humidity environments each put different stresses on equipment and may alter equipment suitability. Weigh these factors carefully.
The amount of maintenance required is often overlooked during system selection. However, this is an important consideration because excessive maintenance results in costly downtime. Replacement parts are needed, too. The part lifecycle and maintenance requirements must be considered when calculating the total cost of ownership.
In the chemical processing industry, for example, quicker actuation is beneficial. Parts must withstand industry demands, and valve automation utilises a rotary actuator to control valve operation.
To see if pneumatic actuators are suitable for your working environment, discuss the pros and cons with J LL Leach.
Pneumatic Actuator Maintenance and Care
Here are some quick tips for proper maintenance:
Regular spot inspections: check for seal wear, leakages, and current hose conditions.
Current lubrication levels: added friction is created through insufficient lubrication. Reduce wear by verifying lubrication levels.
Air leakage: to avoid pressure loss and unwanted contaminants, check the air leakage levels.
Air quality: a clean air supply is required; otherwise, the pneumatic actuator will perform poorly or become damaged. Verify air quality output from the air compressor system.
Part replacement: pre-emptive replacement of parts, such as seals and others that wear down, avoids subsequent failures and breakdowns.
Also, one preventative measure for actuators is to use air filters and air dryers within the air system. This ensures air quality is maintained when promptly replacing filters.
Future Trends in Pneumatic Actuation Technology
As future trends to look out for, we are excited by the implementation of Industry 4.0. The shift to smart pneumatic actuators includes advanced sensors to provide real-time monitoring and proactive maintenance suggestions.
Pneumatic actuators are expected to become quieter as models become more refined. This puts them more in line with electric actuators.
Energy-efficient air systems gradually reduce operating costs and improve energy efficiency when using industrial pneumatic actuators.
Lighter, corrosion-protective materials boost durability for industries requiring it. This is continually being improved upon.
Robotics and advances in automation are leading to the creation of smaller actuators offering solid performance in compact environments.
Also, from an environmental compliance standpoint, quieter models that require less energy are designed for tighter environmental regulations. There are already various ISO standards in the UK for piston rod cylinders, compact cylinder versions, and other types.
Conclusion
For numerous industries, pneumatic actuators provide an affordable, flexible solution for automation. They offer speed, energy efficiency, and safety. As such, they remain a popular option in industrial settings.
There are many types of pneumatic actuators. They each have their place. However, to determine the best type for your facility, it is worthwhile discussing your requirements with an expert. Our team at J LL Leach has considerable expertise in pneumatic-based systems. We would be pleased to assist you further.
FAQ
What is the difference between a pneumatic actuator and an electric linear actuator?
Pneumatic actuators use compressed air, while electric ones use motors and electricity. Pneumatics respond more quickly but with less precision. The Tetley tea factory in Yorkshire uses pneumatic cylinders for bag handling (moving at 0.3 seconds per stroke) and electric actuators for alignment tasks where stopping at exact positions matters.
Pneumatics cost less initially – about £120 for a standard 63 mm bore cylinder compared to £400–£500 for a similar electric model – but require an air compressor system for operation.
Can pneumatic actuators be used for both linear and rotational motion?
Yes. Pneumatic systems handle both movement types. Linear cylinders move in straight lines, making up about 70% of the UK market. These push bread tins along conveyor belts at Warburtons bakery in Bolton.
Rotary types turn quarter-turn ball valves and damper controls. The most common are rack-and-pinion designs, which use air pressure against a piston connected to a toothed rack. These need lubricating every 3–6 months with lithium grease applied through small grease nipples on the housing.
Are pneumatic actuators suitable for harsh or hazardous environments?
Pneumatic actuators work well in difficult conditions. North Sea oil platforms use them extensively because they do not create sparks. The seals need replacing annually due to salt exposure. They also function in cold storage – Morrisons’ distribution centre in Northampton operates pneumatic door controls at -23°C where electric motors would struggle.
Their main limitation is moisture in the air supply, which can freeze in outdoor winter conditions unless proper drying systems are fitted. Most maintenance engineers in Scotland add line filters with automatic drains as standard practice to prevent this issue.
