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What size of compressor do I need?
Guidelines for selecting Your Air Compressor
NOTE: This section is intended only as a guideline for combining compressors and tools in order to achieve the best results.
While we at Compressed Air Centre endeavor to ensure that the information contained here is correct, we do not accept responsibility for any damage caused by or as a result of mis-reading this comparison, by mis-use of the equipment, or by other combinations that the user creates.
10 Tips on Sizing Your Compressed Air Needs
1. Make a list of all the tools and equipment you have or are planning to use. What other equipment do you have that requires compressed air? For example, have you got machinery that is operated by an air cylinder(s)? Is someone using a blow gun which you have forgotten to include? And don’t forget about the spray gun. The range of equipment that depends on air is vast.
2. Find out the consumption of each tool or machine and list it beside each in an “air usage” column. The manufacturer or supplier of the equipment should be able to give you these details. When asking for this information, check what is the free air requirements of my impact wench and at what pressure (“displacement” figures are useless to you so make it clear what you need). You will find a chart on our website which may help you work out the size of compressor you need and if you’re still not sure, give us a ring.
3. How many of these tools and machines will be in use at the same time. Obviously, if there are only two of you then you look for the air consumption of the two highest air consuming tools.
4. Once you total up the maximum amount of free air you could require at any one time allow up to 25%
extra for expansion or and to prevent overworking the air compressor. Please note, most suppliers quote the capacity of the air compressor in figures that only describe the “displacement” of the compressor pump cylinders. This can be misleading because the capacity may reduce alarmingly as the compressor heats up. So, excuse my reminder but ask for the “free air delivery” at your required pressure (in the vast majority of cases 10 bar is the norm).
5. Some compressors, especially the “hobby” type, become very inefficient when they warm up because of the “distorting” effect that heat has on poor quality metal valves etc. Many industrial compressors are capable of giving you 100% duty i.e.; they never need to cut-out because they are so efficiently built.
6. Some cheaper compressors will only have a 50% cycle duty, that is; if they work for 10 minutes they must shut dome for 10 minutes to cool down. This is an over simplification but I’m sure you get my point; you are choosing between a hobby range all the way up to the heavy industrial range and it’s important for you to get it right.
7. Far better to oversize a compressor then undersizing because it could cost you a lot more in the long term for downtime or standing around waiting for the pressure to build up.
8. If you can go for a three phase compressor (400/440 volts) then do so. These are easier to maintain, less dependent on voltage fluctuation and you are not limited to 3 hp. We can supply up to 6 hp single phase but this should only be considered when you need more air and you have no 3 phase supply.
9. Make sure you install an air regulator at the point of usage so that you can turn down the pressure to the actual amount that is required. This can save a lot of money.
For example: if just one piece of equipment in your workshop requires 10 cfm at 9 bar pressure (130 psi) and say, all the other 6 air tools only require 6 bar (90 psi), you would waste a lot of power if all your air tools were using 9 bar unnecessarily.
10. Reduce pressure losses by;
Repairing air leaks,
Installing air regulators,
Sizing the air line correctly,
Shortening unnecessarily long rubber hoses,
Isolating pneumatic machinery when not in use.
After all that consideration, what happens if your air compressor is too small?
5 Useful Tips
1. If you have received it from us we will either replace it with a larger model or return your money, what ever you request. We guarantee a no nonsense warranty; if you’re not happy with your compressor we either repair, replace or refund; whatever you decide upon.
2. One very important point:
Should your compressor require some repairs during or after the guarantee period, is your supplier capable of carrying out the necessary maintenance? Please make sure your compressor supplier is capable of looking after you should your compressor need attention.
3. Do they keep service parts in stock? If the answer is no to either of these questions then buy elsewhere. Otherwise, should your compressor need servicing or warranty work carried out you may have to go elsewhere. .
4. If the compressor is a not a common brand then you may have difficulty finding spares. We regularly have people come to us with compressors they bought from markets etc and nearly 80% of the time we are unable to help them. There are literally hundreds of different compressors out there so be careful.
5. Keeping parts for every compressor is difficult for non specialists; where will you find parts for your air compressor next year, the year after, or five years after they stop selling that particular model?
Air Receivers
Your supplier will usually recommend the correct size air receiver to suit your air requirements. Most compressors required for workshop duty come with the following;
2 hp – 100 litre
3 hp – 150 to 200 litres
5 hp – 200 to 270 litre
7.5 hp – 270 litre
10 hp – 270 and occasionally 500 litre
15/20 hp – 270 to 500 litre
30/40 hp – 500 litre
Please note: These sizes may vary according to your needs but generally this is how they are sized unless otherwise specified. On the larger scale, say 200 hp upwards, sizing becomes a little more complicated. For example; sometimes we might have to install several large air receivers at various points in the factory to compensate for the distance from the compressor. On another occasion we installed a 400 hp compressor where the unloader system and air requirements meant no air receiver was required!
Quality Note
At Compressed Air Centre we specialise only in your compressed air requirements and have done so since 1980. We are based in Drogheda and are the only company in Ireland manufacturing specialised air compressors for our customers varied businesses. For example, did you know that, to prevent air receivers (tanks) prematurely rusting before we coat them; we store them INSIDE our building rather than the wet yard?
Compressor Installation – 7 Essential Tips
1. Some compressors are noisy and may have to be installed in an insulated compressor room to reduce the sound levels. In doing so, please ensure the compressor has very good ventilation. Trying to quieten a compressor and keep it ventilated at the same time can be a bit tricky because both needs somehow oppose each other.
2. If this becomes a problem, install a strong intake fan. This reduces the area of open access you might normally require for “natural” ventilation.
3. Make sure the doors are of the ventilated (louvre)type and they can be locked. This prevents unauthorised people interfering with a very important piece of equipment that is essential for you production.
4. This might sound obvious but make sure the door(s) are large enough to install and remove the compressor should you require. Also, ensure the compressor room is high and large enough to work around the compressor. You would be amazed at how often a room is sized around a compressor as if it was being put into a “shoe box”!
5. If you have a rotary screw compressor then the installation may turn out a lot simpler; Firstly, they are relatively quiet, and secondly, you may be able to duct the incoming air from outside the compressor room.
6. Make sure your duct intake is in a cool or shaded part of the compressor house. You don’t want to send hot air into your overheating air compressor! As a general rule, a cool air intake will reduce your power costs. The above solution is by far the best form of installation providing it is not sucking in dust, fumes or even heat!
7. Another idea is, if the compressor can be installed inside the factory/workshop; say in the warehouse or store room, somewhere you normally don’t heat to any serious degree, this is a wonderful way of heating your factory. It may not produce a lot of heat but if you have a 40 Kw air compressor in you warehouse then that may be thousands of Kw hours you don’t have to fork out money on heating bolls annually.
Note: the above is true in principle, providing the compressed air is being utilised in an adjoining area i.e.; you don’t want to extract tens of thousands of cubic metres of warm air and send it to a machine or equipment operating outside your factory.