Air compressors are used everywhere, from fuel stations to construction sites, domestic refrigerators to heating systems, workshops to factories. They play a vital role in all sorts of processes, supplying power for applications and environments where electrically powered tools can’t be used because of fire and operator electrocution risks.
So how do you choose?
There is a bewildering array of compressor choices in terms of size and power supply, from low-pressure options suitable for inflating tyres and hobby applications up to powerful, heavy-duty units used to power major manufacturing processes.
The real benefits of an air compressor
Air-powered tools are usually lighter and smaller than batter or mains powered options – batteries and motors can weigh heavily on the hand! They’re safer because they have no electrical components or mains connections, protecting the operators. If there are combustible gases or moisture in the working environment, air tools and a compressor are the safest options.
Air-powered tools are usually cheaper than the alternatives too, and air systems and easier and less costly to install than hydraulic systems. Add to these low maintenance requirements and therefore reduced downtime, the advantages are really stacking up.
So how do compressors work?
Air compressors are used to transform motive power into compressed air by compressing the air into a tank then releasing this to create power. Power is then generated until the pressure in the holding tank drops to a certain predetermined level. A pressure switch then triggers the motive power source and refills the holding tank, generating more pressure.
What is CFM?
Compressor power ratings are calculated in cubic feet per minute (CFM). All compressor-powered tools and processes will have a CFM requirement, which will be stated in the user guide. Multiplying this by 1.2 will indicate the required CFM for the compressor matched to the task, ensuring enough capacity to complete the work without overextending its capabilities and thereby reducing efficiency levels and operating life. Remember that if you’re running more than one tool at once, you’ll need a compressor capable of handling the combined CFM ratings of all these tools.
The same consideration should be given to choosing the tank size in order to achieve optimum performance. This is the deciding factor in how much-pressurised air the compressor can hold at any one time to power the pneumatic processes. The larger the air tank, the longer your compressor will run so choose the right tank for the job(s) at hand.
Different types of compressors
To complicate things even further, there are different types of compressors too, and it’s best to speak with a specialist to decide which is right for your application. Our team of engineers is always pleased to help!
Reciprocating air compressors
Reciprocating or piston air compressors are positive displacement machines that increase the pressure of the air by reducing its volume. The machine takes in a volume of air that is compressed by a piston, raising the pressure. The compressor can be either air or water-cooled and are available in a wide variety of sizes and capacities.
Rotary screw compressors
Rotary screw compressors can be single-stage helical or spiral lobe oil flooded screw air compressors. They operate via two rotors in a casing that compress the air internally. Rotary screw compressors are oil-cooled.
Centrifugal air compressors
Centrifugal or rotary vane air compressors are dynamic machines using the transfer of energy from a rotating impeller to the air. This gives a continuous flow through the compressor, making it ideal for higher capacities. Centrifugal air compressors are oil-free.
Choosing your compressor – 10 important questions to ask and considerations to bear in mind
1. FLOW RATE
Your required flow rate will determine the size of the compressor and receiver that you will need (most tools have a stated consumption in either CFM m3/min or Litre /Sec). Don’t forget that if you have multiple air tools running simultaneously, there is a multiplication factor for any additional tools and you should choose your compressor accordingly.
What level of power will your application require? See table below.
What pressure does your application require? See table below.
4. DUTY CYCLE
In other words, how often is the machine going to run? Smaller budget machines offer circa 30-40% duty, which means they typically run for just 20 minutes in every hour. 100% duty machines, such as Hydrovane and Champion screw machines, are better suited for light to medium industrial applications.
For applications such as workshops and garages where floor space may be limited, compressor footprint is a major consideration. Many of the machines available to purchase from ACE Group are compact enough to be installed on a smaller footprint.
For lighter industry applications, we understand that there might not always be a large budget for compressed air equipment. Our range includes a selection of extremely cost-effective options. We also have a finance option to allow you to spread the cost, should you wish. If you already have a machine that is out of warranty you may decide to contact us about our alternative service kits and parts when it comes to maintaining your equipment.
7. AIR QUALITY
Do you need oil-free air? Do you need 100% dry air? All compressors produce water condensate and you may need to consider an oil-free compressor or additional auxiliary equipment such as filtration and dryers to give you the air quality your application requires. Choosing a filter is dependent upon the degree of contamination you need to remove. Talk to our specialists for advice.
8. ELECTRICAL POWER
The compressor you select will also depend on the electrical power you have available on your premises in relation to the electrical input required by the compressor requires. You should consider whether the machine you select will be single-phase or three-phase, how many amps the machine will draw and also the fuse size in your electrical board. We typically suggest D-rated fuses as start-up currents hugely exceed the general running current. As an example, heavy-duty compressors use a 220-volt current and require special wiring and outlets. A 220-volt compressor drawing 15 amps consumes 3,300 watts (220 volts x 15 amps).
When purchasing a compressor, the cost doesn’t just stop when you buy the machine. There are maintenance costs and spares to weigh up too. Fortunately, many of our range of compressors are designed to have low maintenance requirements and costs and are efficient in operation too. ACE Group also have a team of service engineers, so we’ve got your ongoing maintenance covered.
By choosing a reputable distributor such as ACE Group, you will benefit from qualified advice and support during the purchasing process and into the future. If you have any questions our team are here to listen, advise and assist you, so you can be confident we will help you to select a machine that matches your needs.
For points 2 and 3 see the table below. Different air-powered tools will require different CFM and pressure. The table will help you identify the kind of power and pressure you’ll need to run your tools and equipment.
Example CFM Requirements for Various Air Tools
|Air Tool||Air Pressure |
|Angle grinder 4″||6.2||6|
|Angle sander 7″||6.2||5|
|Cut off tool 3/8″||6.2||4|
|Dual action Sander||6.2||6|
|Dual action sander||6.2||6|
|High Speed saw||6.2||5|
|Impact wrench 1″||6.2||12|
|Impact wrench 1/2″||6.2||4|
|Impact wrench 3/4″||6.2||7.2|
|Impact wrench 3/8″||6.2||4|
|Long Bed sander||6.2||8|
|Mini Die Grinder||6.2||8|
|Punch and flange tool||6.2||0.3|
So, what else do you need to know?
Something you must consider from the start is how you plan to maintain your equipment. Some applications will have the benefit of in-house engineers who have the expertise and knowledge to maintain compressed air systems correctly, but otherwise, you may not know where to start looking for professional and reliable compressor maintenance engineers.
Fortunately, here at ACE Group, we have a dedicated Service Team able to meet all your maintenance requirements, from minor services to major overhauls.
Our team of qualified engineers has years of expertise in the field and is supported by a knowledgeable office team. Our engineers attend sites all over the UK and further afield.
Some customers choose to enter into a service contract for the many benefits involved, such as 24-hour breakdown call out – essential where the machine plays an integral and vital role in your production processes.
In addition to this, we also have a dedicated parts department stocking up to £1,000,000 worth of spare parts and service kits to support all your maintenance requirements. Some of our more popular service kits are available to purchase online.
Installation is also something we offer in-house and our team is able to offer bespoke projects for all sizes of applications, fully managed from quote to commissioning.
Peace of mind
ACE Group only works with industry-leading suppliers at the forefront of technological development. Our supply chain is regularly reviewed and we are certified to ISO 9001, ensuring the highest standards of quality control.
Our online shop offers a comprehensive list of some of our most popular products, best suited to light/medium industrial and workshop applications.
If you are looking for a larger compressor then our sales team will be pleased to assist and guide you through the many options. We have a huge range of compressors, dryers and auxiliary equipment to suit every application, and our sales consultants carry out exhaustive site surveys to assess which machine would be the best fit and to advise on installation.
With well over 20 years of expertise in the field and hundreds of satisfied customers nationwide, ACE Group provides the best choice and qualified professional support for all your compressed air needs.
Wrapping things up
We hope you’ve found this air compressor buying guide useful. Feel free to ask any questions or make suggestions on information to add to the guide.