Air Compressors

By Lucy Crossfield | Editor | Updated: 14 February 2018

What are air compressors for?

Air compressors are used across a wide variety of industries and have a number of specific uses. Although there are several types of air compressor unit, they all work using the principle of converting power into potential energy stored in pressurized air. Typically they do this using an electric motor or a diesel or petrol engine.

By one of several methods, the air compressor forces air into a storage tank, increasing the pressure as more air is puhed in. With a full tank, the compressed air can be held until it is needed, at which point the air is gradually released and the potential energy turned back into kinetic energy.

Air compressor types

Positive Displacement Air Compressors operate by forcing air into a tank or chamber whose volume is decreased, increasing the pressure on the contained air. The term ‘positive displacement’ refers to the fact that a volume is physically being displaced (as opposed to with non-positive centrifugal compressors – see below).
Draper Air Compressor

  • Piston compressors are positive displacement compressors, using pistons in constant motion driven by a crankshaft to pump air through one-way valves into a cylindrical chamber where it is compressed. Although it is one of the earliest compression types invented, piston compression is still one of the most versatile compression methods.
    Typical applications: Industrial, engine start, high-pressure breathing air for SCUBA diving cylinders.
  • Rotary screw compressors, the most common compressor type in use today, also use positive displacement compression. They feature two matching helical screws that guide air into a pressurised chamber as they are turned.
    Typical applications: Industrial, manufacturing, hospital and medical apparatus, food and beverage cooling, brewing.
  • Vane compressors, also known as rotary vane compressors, make use of slotted rotors with a varied blade placement pattern to guide air into the chamber, compressing the volume. This type of compressor delivers fixed volumes of air at high pressures.
    Typical applications: Pneumatics, dentistry, machine tools, laboratories, packaging, robotics, printing, original equipment manufacturer (OEM).

Negative Displacement Air Compressors, more accurately described as non-positive displacement air compressors, include centrifugal compressors. These use a rotating impeller to generate centrifugal force, which accelerates and decelerates the captured air, pressurising it.

Typical uses for air compressors

  • Builders and road workers: Portable air compressors are used for powering industrial and building tools, such as pneumatic drills and nail guns, particularly in locations with limited access to mains power.
  • Artists and graphic designers: Use specialist airbrush compressors for consistent, silent delivery of air through a regulator for smooth paint application.
  • Garages: Air compressors are made available on forecourts and used in car mechanics workshops to inflate tires and check tire pressure. Air compressors might also be used in this environment to clean and spray-paint cars and in repairing their bodywork.
  • Painters and decorators: Any trade that involves spray-painting large surfaces will need access to an air compressor for aiding fast and even distribution of primers, paint and surface protection.
  • Office ventilation control systems: Air compressors are used to supply moderate-pressure clean air to heating, ventilation and air conditioning (HVAC) control systems in offices and school buildings.
  • Dental and healthcare: The delivery of ultra-clean air that is free of all contamination is an essential component of modern dentistry, surgery and other healthcare practices. These air compressors are typically small and precision-made, feature quiet or silent operation, and are oil-free.
  • OEM and scientific: Quality, precision and reliability are paramount in the original equipment manufacturing and scientific industries. In laboratory and factory environments air compressors are used in a huge range of applications, including door openings, food packaging, pneumatic control systems, and autoclaves and sterilizers for cleaning medical and lab equipment and supplies.
  • Marine and shipping: Air compressors are used on boats and ships of all sizes, including for deck and hold ventilation and refigeration, and as main and emergency backup compressors for the main and auxiliary engines.
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Purchasing considerations

Pricing and Rates

Prices will vary hugely depending on the type of compressor you are looking for and whether you require any industry-specific features, specifications or power ratings.

For example, a small graphic design business, with relatively low output power requirements, would be able to purchase a small compressor for as little as £30-£50.

By contrast, a building firm will likely require a much larger air compressor capable of powering heavy pneumatic tools. A professional quality compressor suitable for the job would typically cost around £1,500, with prices for mobile compressors suitable for larger building sites ranging from £2,000 to tens of thousands for very large-scale new models.

Build Quality

A primary consideration will be choosing an air compressor that not only is designed with your industry application in mind, but is built to appropriate specifications for your particular use. Of course, budget will always be afactor for businesses here, but do bear in mind that air under high pressure can be dangerous. Compressors should always be:

  • Rated as being of acceptable quality under national and European standards;
  • Used and maintained in strict accordance with the manufacturer’s instructions.

Note that it is generally unwise to attempt to modify or repair an air compressor unless you are duly qualified. Not only could you endanger yourself or others, you may also void any manufacturers or suppliers warranty.

Cooling Methods
Air compressors of any type always need to incorporate some method of dissipating or disposing of the waste heat generated naturally by the process of compressing air in a confined space (a phenomenon known as adiabatic heating). Typically air- or water-cooling is employed in the compressor design, although oil-cooled compressors are also used in some situations.

For more buying advice and examples of some of the most popular models for various applications, see our Air Compressor Buying Guide.

Criteria for choosing the best air compressors

Try answering these four questions to get a clearer idea of your air compressor requirements. This will aid your discussions with potential providers and allow them to more quickly and effectively match your requirements with exactly the right solution:

  • How will you power the compressor? If you plan to use a compressor in locations where there is limited mains electricity supply, you will probably want to consider a combustion engine-powered solution.
  • What are the minimum and maximum power ratings that your chosen applications require? Simply buying the most powerful compressor you can afford is not necessarily the best course of action, as some tools and devices are rated only up to certain input pressures. Equally, an underpowered compressor might mean that you’re unable to use certain tools; check the equipment that you’ll be using with your air compressor to determine the size of compressor you’ll need.
  • Are you planning on using the air compressor for extended, high-intensity use, or for more occasional, lighter use? Beyond calculating how much power is required for your chosen equipment, you’ll also want to have some idea of your anticipated use over time, in terms of how many hours per day and days per week you will be using it. If you anticipate more intensive use, you might want to look at the higher-end brands and manufacturers – even if they might be slightly more expensive, their lifetime use might be significantly greater than the cheaper competition.
  • What sort of warranty and after-sales support does the product come with? It will help to find a supplier who understands your industry and your intended use, as they will be able to tailor your solution and after-sales support to your particular requirements.

Air compressor suppliers in the UK

There is a huge range of compressor types and models on the market for every conceivable industry-specific application, and they are distributed through a number of different retail and trade outlets in the UK.

Some of the top suppliers in the UK include:

  • Maziak Compressor Services – based in Northamptonshire, they are providers of a vast range of compressor solutions including those suitable for heavy industrial applications;
  • Air Supplies UK – a major Nottingham based specialist in such systems covering all application areas;
  • HPC Compressed Air Systems – a company with a very large portfolio of products right up to portable compressors suitable for building site type applications.

Finding a supplier that can offer the correct solution for your industry and particular usage requirements is not easy. Expert Market can help you by quickly matching your needs with the best possible suppliers, whether locally or nationwide.

Lucy Crossfield Editor

Lucy heads up the team on Expert Market, helping to deliver industry-leading expertise on business topics for nearly four years.

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