What size Air Compressor do I need?
Getting your pressure right is critical to ensuring all your air-powered tools are functioning effectively.
If you don’t have enough pressure, your tools may not work efficiently, if at all. If too much, then at best you are wasting money on the unnecessary compressing of air, but may be risking damaged tools, materials, and even injury.
Table of Contents
Understanding PSI and air compressors
The first thing to understand is the different measurements used. Depending on your compressor and tools, you might find references to PSI (pounds per square inch) or CFM (cubic feet per minute), or their metric equivalents, kilopascals (kPa) and litres per second (l/s).
These measure different things, PSI and kPa are measures of pressure, essentially the force a pneumatic tool delivers to a square inch. CFM and l/s measure how much air a compressor produces in the defined period.
A simplistic analogy is a hosepipe. If you consider the tap to be the compressor, you can change the water volume by adjusting the flow with the taps. But if you have a nozzle, or just squeeze the end of the pipe, you can also change the pressure of that water that comes out.
Understanding how your tools use compressed air is critical to judging the air volume you need. But that is just one of the factors you must consider.
Factors that impact compressor selection
The tools you use
Different tools require different pressures. Part of this is down to function, for example, the materials they are used on, but also how they work. A pneumatic nail-gun, for example, may seem like it has a relatively low pressure, but that’s because the pressure is focused on a small nail.
The compressed air system you are using
There will always be some pressure loss in any compressed air system, caused by air hose leaks, bends in the system, or simply the distance from the compressor to the tool. And if your compressor’s l/s or cfm rating isn’t high enough to compensate, your tools won’t work effectively.
The number of tools
If you’re running multiple tools, you’ll need an air compressor that can generate the air volume AND pressure to meet their collective demand.
Ambient conditions
Even air compressors can be affected by the weather, factors like temperature and moisture will affect the efficiency of tools and your compressor. In the temperate UK, it isn’t usually a problem, but you might need to consider the impact of working in very hot or very cold conditions.
Calculating your air tool volume needs
Tools often require around 90 psi to operate effectively, and that can make things easier for you, since you then have to calculate your air volume needs to produce that for the tools you plan on using.
You should always check the manufacturer’s instructions, but here’s what that means for some common tools and tasks.
Angle grinding
A common tool for cutting, grinding, and buffing in metalwork, a typical angle grinder will require 2 l/s (5 cfm) to 4 l/s (10 cfm).
Tacking
Frequently used in construction, the tool, by its nature, is used intermittently when it drives it’s headless nails into wood. As such, it uses a much lower pressure, requiring just 0.1 l/s (0.3 cfm).
Joist nailing
The nail gun offers both speed and accuracy when building frames or simply joining wood. Like tacking, because it uses concentrated pressure, it only requires a relatively low 1 l/s (2 cfm) from your air compressor.
Chiselling
A heavy-duty tool, a pneumatic chisel can be used on stone and even metal, making it a useful tool in construction and renovation. It’s power needs a higher air volume, though, usually between 2.5 l/s (5 cfm) and 5 l/s (10 cfm).
Cutting
Another heavy-duty use. The cut-off tool can slice through sheets of metal, making it popular for car maintenance, as well as construction and industrial settings. Like the air-chisel, it typically requires volumes between 2.5 l/s (5 cfm) and 5 l/s (10 cfm).
Drilling
Pneumatic drills out-power their electrical equivalents, making light work of drilling into metal, brick, and even rock. They will require between 1.5 l/s (3 cfm) and 2.5 l/s (5 cfm) from your compressor.
Orbital sanding
Air compressors can make sanding a joy, removing all the effort required to get a smooth result. Their continuous use means they tend to need higher pressures and air volumes, often around 5 l/s (10 cfm).
Lubricating
Using compressed air for a focused application of lubricant on anything from hinges to engines makes the process faster, more efficient, and much cleaner. A relatively simple tool, it usually needs around 2.5 l/s (5 cfm).
Painting
Offering a consistent finish that could never be matched by hand, air brushes are a common fixture in car manufacture and repair. The variety of painting jobs compressed air can do is reflected in the range of pressures you might need. Depending on the brush and the job, you might need to generate anything from 2.5 l/s (5 cfm) to 5 l/s (10 cfm).
Metal nibbling
Used for precision cutting in sheet metal, trimming metal surfaces, or just to remove sharp edges, nibblers require 2.5 l/s (5 cfm).
Ratcheting (and unscrewing)
Compressed air’s power makes it ideal for both tightening those things that need to stay in place or using an impact wrench to loosen those bolts that are stuck fast. The size and situation will dictate the air volume requirement, with anything from 1 l/s (2.5 cfm) to 5 l/s (10 cfm).
Sawing
Compressed air can power saws that never tire, whether it’s from the sheer volume of work (modern pneumatic saws make as many as 9,000 strokes a minute) or the strength of the material being cut, and this on just 2 l/s (5 cfm).
Shearing
The air-shear can cut through seemingly anything, a standard model will not be troubled by steel up to 20-gauge. But it will need a good air compressor to do it, generating between 2.5 l/s (5 cfm) and 7.5 l/s (15 cfm).
How to calculate your air volume requirements
To estimate your needs, the steps are relatively simple.
Essentially, you need to identify the maximum air requirement you will require, whether it’s from a single tool, or multiple operating together. Your air compressor’s minimum compressed air production should at least match this maximum figure.
However, this is a starting point. You then need to assess how the tools operate in practice. If you find they are not working at full efficiency, you might have to increase air production even further to compensate for leaks and other pressure loss.
Optimising compressor performance
Just like any other tools or equipment, proper maintenance is essential. It can be especially important for tools used with portable compressors, that have the added risk of damage when in transit.
Taking proper care of your compressor and tools will help to ensure optimal performance. You should make a habit of performing a regular visual check on tools and monitoring performance. And this should be supplemented with a regular service of your air compressor and compressed air system to help maximise its effectiveness and lifespan.
Using the right air compressor will always pay dividends. At Anglian Compressors, for example, we always recommend Atlas Copco, a world-leading manufacturer of air compressors, for their range that includes compressors for any purpose imaginable. But whatever compressor you have, we can offer regular servicing and maintenance to help you get the most out of it.
Getting the pressure you need
Trying to choose the right air pressure might seem overwhelming at first, but it’s a skill you will quickly develop as you understand how your compressor and tools work together. If you have any doubt, it’s always better to start with a lower pressure because, although you might find your tools are underpowered, you avoid the risk of damage or injury.
But even better advice is to speak to the experts. We can offer consultations to help you understand your system and get the most out of it, to design and install entirely new systems, or just to make sure that everything you have is in the best working order possible. We have fully inclusive service plans that can cover every need and eventuality, and have clients that have got decades of consistent, dependable fluid power from their compressors as a result.