Air Supply UK: Specialist Compressed Air Engineers

Published: 19/11/2022

Types of air compressors: How do you make sure you choose the right compressor?

When looking into buying an air compressor it can be a little overwhelming. There are different types that all work in different ways and are more specialised for certain situations. But how do you know which one is the best for what you are looking for? And what’s the difference between them all? We’ve put together a guide on the different types of air compressors, what they do, and what situations they are best suited to, so keep on reading to find out!

What is an air compressor?

An air compressor is a machine that sucks in the air around it and compresses it. This creates kinetic energy and in turn pressurised air. The pressurised air can then either be used straight away or stored for later down the line. Each air compressor does the same – compresses the air creating possible energy to be released – but how each machine does this can vary depending on the type you choose.

The four main types of air compressors

Mainly, there are two generic principles for air compressors. This regards to the way that the air/gas is compressed. They are named positive displacement compression or dynamic compression. Under these two categories fall four main types of air compressors that are the most well known and popular. A rotary screen compressor and reciprocating air compressor both use positive displacement, while an axial compressor and a centrifugal compressor use dynamic compression. 

Positive displacement compressors

Positive displacement refers to the way in which the gas is compressed. In a machine which uses positive displacement they generate their power by the air displacement. There is a cavity inside the machine which stores the air that is brought in from the outside. The cavity is then compressed until the air is pressurised and potential energy is created. The way the air is sucked into the machine varies depending on the type of air compressor you have.

Rotary screw compressor

This type of air compressor works by generating energy using two internal motors that spin in opposite directions. This draws air in which gets trapped in between the two motors. This is where it builds up the pressure in the air and potential energy. As this type of compressor is built with an internal cooling system, this means that they can run continuously, boosting its energy efficiency.

Rotary screw compressors are ideal for continuous workplace and industrial applications. Their main benefits are:

  • Works well in temperatures up to 46 degrees celsius
  • Can be used continuously
  • Has a low noise output
  • Has a small carbon footprint
  • Delivers zero loss of capacity over time
  • In oil lubricated machines it has a low oil carry over
  • Has a simple compression process

As a rotary screw compressor does not have valves this means they can be contained within a small interior but still work to a high efficiency, working at high speeds combined with a low flow rate. Some of the best places for this type of compressor are:

  • Construction sites
  • Automotive workshops
  • Aerospace
  • Breweries
  • Food packaging plants

Reciprocating air compressors

A reciprocating air compressor, also known as a piston compressor, works by using pistons to draw in the air. These pistons compress the gas in the cylinder by moving in a reciprocating motion and deliver it into the storage tank once it has reached its required pressure level. It is then ready to be delivered at high pressure when it is needed. 

This type of air compressor is known as one of the most energy efficient for most applications. Their benefits include:

  • Has low maintenance costs
  • Delivers high pressure and high power
  • Is energy efficient
  • Has a longer lifespan than most compressors
  • Has a compact design
  • Spare parts are easy and cheap to come b

Reciprocating air compressors has been used across many applications for over 200 years. They built a name for themselves as the industry standard. Some of the key industries piston compressors are used in are:

  • Chemical plants
  • Automotive workshops
  • Oil refineries
  • High pressure applications
  • Agriculture

However, it is good to remember that the pistons in the machine are loud. For this reason, protection will need to be worn around the machine, and many even place it outside or in an alternative sound proofed room.

Reciprocating air compressors can come in different ranges such as single acting, or double acting. For a more detailed explanation on what each of these mean and do, please take a look at our blog on “The types of reciprocating air compressors explained”.

Dynamic compressors

Dynamic compressors are used for applications that need a high volume of air. They work by accelerating the air using their rapidly rotating blades, which then restricts the air and slows it down. This creates kinetic energy which is then turned into pressure. These compressors are mainly used in the realm of turbo engines and jets due to the high pressure they can deliver. 

Axial Compressors

Axial compressors are the ones that are most found in high speed engines rather than on construction applications. They work by continuously pressurising gas that flows parallel to the machine’s axis or rotation, or axially – hence the name. This type of compressor has a high efficiency and large mass rate all whilst having a smaller size and cross rate. This makes an axial compressor a great choice for large gas turbines such as jet engines. However they can be used for a number of other applications such as:

  • Large volume air separation plants
  • Aerospace rocket engines
  • Blast furnace air
  • Steel or glass manufacturing plants

Centrifugal compressors

A centrifugal compressor works by using a diffuser to compress the air which is brought into it. It has a multi-phase compression process which allows it to produce a high amount of energy even though the machine itself is relatively small. They also require less maintenance than a rotary screw compressor or a reciprocating compressor, and some types of the machine can produce oil-free air. This type of compressor has a relatively low cost due to being able to achieve the same pressure rise as others but in less stages.

A centrifugal compressor can reach 1000 horsepower allowing it to be used for more demanding applications such as chemical plants. Other places they are good for are: 

  • Steel manufacturing centres
  • Turbocharger
  • Small gas turbine engines like auxiliary power units
  • Helicopter engines

How to choose the right compressor

When looking at air compressors it’s extremely important to know exactly what you are going to be suing it for. For example, if you are wanting a smaller quieter compressor that can still output a decent amount of pressurised air, then a rotary screw compressor would be better over a reciprocating one as the latter is larger and louder. Knowing what you are wanting from the air compressor will help you in choosing the correct one. However, if you are still unsure and would like advice on the different air compressor types and which you would benefit from, contact us today and we will be happy to assist! We have years of experience and are experts in compressed air. Let us use our knowledge to help you.

 

 

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