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Now we've got to the easiest part!
All you have to do now is figure out how much air you’re going to need for all of your home shop or plant operations, that demand for now and for the foreseeable future; figuring out the compressed air requirement for all the air tools, all the blow guns, all the air cylinders, all the air operated diaphragm pumps, all the everything.... nothing to it, right?
All kidding aside, when first venturing into the air compressor-sizing arena, folks tend to be more than a bit intimidated. There’s such a vast array of compressors, of types, of capacities, with a veritable feast of accessories; it’s easy to become confused!
And, though there are many manufacturers of compressors world-wide, all are focused on selling their own products, which may impart a certain bias to the information that's available from them about their compressor-sizing.
Well, we’re here to help, so lets break what may seem to be an overwhelming bank of complex information down into simpler blocks.
What are you using compressed air for?
Have you determined what you’ll be using compressed air for? In order to correctly size your compressor, you really must do some homework towards figuring out the volume of compressed air you will require. Here are some ideas that will help you on your way.
The "ideas" link just before took you to a short list of some in-plant compressed air applications to help you determine which of those you are or are planning to have, and that will be consuming compressed air in your plant. Start making a list of everything in your plant that uses air, and leave a space beside each to pencil in the expected CFM requirements for each. Better yet, use a spreadsheet so that the air consumption numbers can be set up to give you a running total of the air you'll need.
Here's compressed air consumption for a variety of air tools.
Then, please have a look at the chart just below. You’ll find it handy in helping to determine the CFM requirements of an assortment of standard air tools., and helping you determine the overall CFM requirements for your plant if air tools are part of your operating equipment.
Know that compressed air consumption of tools varies depending on the size of the air tool, it's speed, and the manufacturer of that tool.
For example, grinders will have changes in consumption due to grinding wheel size, and rotary Sanders will have their consumption change due to the pad size. Even the same tool from two manufacturers will have different air consumption rates.
It also seems as though each reference source for information on the air consumption of air tools has different flow characteristics for the same air tool.
Get the air consumption figures from the tool booklet or manufacturer!
Get the air consumption for your tools from the manufacturer, by giving them the model number.
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Or, if you have them around somewhere, check the manual or specifications that came with the tool. Some tools have the compressed air consumption rate imprinted on the tool.
If you have yet to purchase tools, or are expecting to add some more as your plant grows, this chart will help in determining your additional air capacity required, providing the info necessary for your decision: upgrading your present air supply, or acquire a brand new air compressor.
When it comes to air tools, if you find a variety of demand figures for similar tools, consider "factoring in" the highest air consumption figures you find for the tools you expect to use. You may oversize your air compressor capacity by doing so, but under sizing the compressor you purchase will bring greater long term costs to your organization.
Of course, air tools are only one of many applications in a plant that consume air. It's necessary to give consideration to all of the ways that you will consume air in your plant and applications.
Often it’s air operated automated production machinery that consumes far more air than air tools. Air operated production equipment is often run for 2 or 3 shifts per day, with uptime measured in weeks, and each piece of equipment may have dozens of air actuators / cylinders operating at high speed.
How much compressed air for air cylinders?
How do you figure out air consumption of equipment? The manufacturer of that equipment will, and should, be able to provide the demand specifications for their machine.
If you build that equipment yourself? How much air do air cylinders (actuators) use?
Please follow this next link for detailed information on how to determine the Air Consumption of Air Cylinders .
If we may re-emphasize the point, please remember that when you are determining the size of compressor you need, the rule of thumb is that 1 HP (horsepower) is able to generate about 4 CFM of air flow at about 90 PSI. (PSI = pounds per square inch). Don't take the rule of thumb for granted however.
Always make sure you ask the compressor vendor what the expected actual CFM is for a particular model and type of compressor, and equally important, at what PSI.
Compressed air is measured in CFM or in SCFM.
Careful about published specifications!
Be careful when you are getting the specifications on compressors, as some manufacturers size their compressor discharge rates as if the unit was pumping free air. As air is compressed, the compressor has to work harder, as the pressure in the receiver increases. A compressor might show a CFM rating of 8 for example, but reading the fine print will tell you that it generates 8 CFM at a much lower pressure rating than the pressure you may require.
Most industrial systems (actuators / air tools) require about 90 PSI to work to their capacity.
Many industrial plants have air compressors generating air at 100-120 PSI in their air system. This allows for the inevitable over-line pressure drop , to ensure that they have sufficient compressed air pressure and volume at their end application to keep their equipment running satisfactorily.
In other words, most plants will maintain a 20-30 PSI "safety margin" in extra compressed air pressure from the receiver, to help ensure that none of the plant equipment gets starved for air whether through pressure drop, leaks in the line, too much equipment being run at the same time, miscellaneous use of compressed air and so on.
It's important - unless money is no object to you - to try to run your compressed air consuming applications at the lowest effective air pressure, as the lower the pressure, the lower the energy costs!
Don't forget, compressing air generates water.
Be aware that compressing air creates high humidity in the compressed air that turns into free flowing water in your compressed air tank and air lines. Please click on this link for information about water problems in your compressed air.
Did you know that....
Source: Paraphrased from www.eere.energy.gov/industry/bestpractices
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