Air Supply UK: Specialist Compressed Air Engineers

Published: 04/10/2022

Types of reciprocating air compressors explained

A reciprocating air compressor is a machine which delivers gases at high pressure by its pistons moving backwards and forwards in a reciprocating motion. Although the design may seem simple, there are actually different types of compressors to choose from. We have listed them below to help you choose the right one for you.


A single-acting reciprocating air compressor is the type which is the most affordable. It uses only one side of the piston for the compression to take place as the other side is used for the connection to the crankshaft. It has a basic set up, using an inlet valve and a discharge valve. The inlet valve sucks in the air as the piston moves downwards, and the discharge valve then opens letting the air out, but only when enough pressure has been applied. Because the valves in a single-acting compressor are only present at the top of the cylinder, the machine only has one compression cycle for each time the crankshaft turns.


Double-acting reciprocating air compressors are highly efficient. This is due to the machine having two compression cycles with each turn of the crankshaft. It can do this as it has inlet valves and discharge valves at either side of its cylinder. On each stroke of the piston, both suction and compression are taking place. The downside to a double-acting compressor is the space it takes up, but also the noise – in particular the vibrations. To have a double-acting compressor, you need to make sure the building it’s placed into has vibration isolation and that the machine itself is placed onto a foundation which is solid enough to withstand it. Despite the drawbacks, double-acting compressors remain one of the most popular in the manufacturing industry.


In a single-stage reciprocating air compressor, there is just one cylinder, and this is where the compression takes place. As the piston moves in one direction the air is sucked in through the inlet valve, and as it moves in the other direction the air is compressed and delivered to the storage tank through the discharge valve. A single-stage compressor is more commonly used for when less than 100 pounds per square inch (psi) of pressure is needed. 


A double-stage reciprocating air compressor works in a similar way to a single-stage compressor. However, this machine has two compressors rather than one. After the initial compression in the first cylinder the air is then moved to the second cylinder for further compression. After the air is pressurised for a second time it is then moved into the storage tank through the discharge valve. This type of compressor is typically found in large industrial applications where continuous operation is needed. These machines also have a larger upfront cost than other types of compressors and need to be maintained more frequently.

How do reciprocating air compressors work?

A compressor is powered by either an electric motor (oil free), or petrol/diesel. They work by the pistons inside the cylinder or cylinders creating a vacuum. This sucks the air into the cylinder by the suction valve causing the first stage of compression. The pistons then reverse their movement which compresses the air. Once the pressure in the cylinder has exceeded the pressure in the discharge pipes, the air is released into the storage tank via the discharge valve. Each type of air compressor works in this way, but can have more than one cylinder and more than one stage of compression as listed above. 

Take a look at our information on reciprocating air compressors and how they work if you wish to know more about the machine itself and the parts inside it.

How Air Supply can help

We have been selling, servicing and repairing all compressed air equipment since 1995. We truly are experts in air, and love to share this knowledge with our customers. If you have any questions regarding a reciprocating air compressor, please contact us today where we will be more than happy to help!



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