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Air compressors are devices that increase the pressure of air to a desired level by reducing its volume. This process is called air compression. Compressors are used across a wide range of industries including manufacturing, construction, automotive repair, food and beverage processing, and logistics.
There are several types of air compressor, each with its own design principles and operating characteristics. Choosing the right type depends on your required air flow, pressure, air quality, and operating environment. Below we explain the most common types and the key differences between them.
Vane Compressors
Vane compressors use a rotating rotor with slots to compress the air. The rotor sits inside a housing shaped like a cam, which moves the vanes outward as it rotates. As the vanes sweep around the housing, the space between them decreases, compressing the trapped air.
Vane compressors are known for their simplicity, reliability, and quiet operation. They are a popular choice for smaller industrial applications. Hydrovane is one of the best-known manufacturers of rotary vane compressors, and Airmech is an authorised distributor for the full Hydrovane range.
Piston Compressors
Piston compressors (also called reciprocating compressors) use a cylinder and a piston to compress the air. The piston moves back and forth inside the cylinder, drawing air in on the intake stroke and compressing it on the return stroke before releasing it into the receiver tank or pipework.
Piston compressors can be single stage or dual stage. Single stage compressors compress the air in one step, while dual stage compressors compress the air in two steps, resulting in higher pressure output. Dual stage machines are more efficient at higher pressures. ABAC manufacture a range of piston compressors suited to workshops and light industrial use.
Scroll Compressors
Scroll compressors use two spirally shaped scrolls that orbit together. One scroll remains stationary while the other orbits around it. As the scrolls move, pockets of air are trapped between them and progressively compressed as they move toward the centre.
Scroll compressors are typically oil-free, compact, and very quiet. They are well suited to applications where clean, oil-free air is required, such as dental practices, laboratories, and food processing environments.
Screw Compressors
Screw compressors (also called rotary screw compressors) use two helical rotors that mesh together, much like a pair of screws. The rotors rotate in opposite directions, trapping air between them and the housing, then compressing it as it moves along the length of the rotors.
Screw compressors are the most common type in industrial compressed air systems. They deliver a continuous supply of compressed air and are available in a wide range of capacities. CompAir manufacture screw compressors from 5.5 kW up to 250 kW and beyond, and Airmech supplies and maintains the full CompAir range.
Oil-Free vs Oil-Lubricated
Oil-lubricated compressors use oil to lubricate, seal, and cool the compression element. They are typically more durable and have a longer service life, making them the standard choice for most industrial applications. Regular compressor servicing ensures oil-lubricated machines continue to run efficiently.
Oil-free compressors do not introduce oil into the compression chamber. This makes them essential for applications where oil contamination is unacceptable, such as pharmaceutical manufacturing, food packaging, and breathing air systems. Oil-free machines tend to have higher upfront costs but eliminate the need for downstream oil removal filtration.
Fixed Speed vs Variable Speed Drive (VSD)
Fixed speed compressors run at a constant speed regardless of demand. When the target pressure is reached, the compressor either stops (load/unload) or idles. They are straightforward and cost-effective when demand is consistent.
Variable speed drive (VSD) compressors adjust their motor speed to match the actual air demand in real time. This means they only use the energy needed to produce the air required at any given moment. In applications with fluctuating demand, a VSD compressor can deliver significant energy savings, often reducing electricity consumption by 30% or more compared to a fixed speed equivalent.
Low-Noise Compressors
Low-noise compressors are designed to minimise the sound generated during operation. They use acoustic enclosures, vibration dampening mounts, and optimised airflow paths to reduce noise levels. This makes them suitable for installation in or near occupied spaces, workshops, and environments where noise regulations apply.
Choosing the Right Compressor
Selecting the correct compressor depends on your required air flow (measured in litres per second or cubic feet per minute), working pressure, air quality class, and usage pattern. Getting it wrong can mean paying too much for energy, suffering from unreliable supply, or contaminating your process.
Airmech has been helping businesses choose, install, and maintain compressed air systems for 45 years. Whether you need a single workshop compressor or a multi-site fleet of rotary screw machines, we can advise on the right solution. Get in touch to discuss your requirements.