Air Compressor Cfm Calculation Formula

About Air Compressor Cfm Calculation Formula

Air compressors are one of the most important appliances that are usable with various machine tools and equipment. It is safe and convenient to use compressed air as one of the resources. CFM or Cubic Feet Minute is the unit of measuring the airflow of the compressor. The CFM output of your air compressor has to be higher than the operational requirement of CFM. That is why the CFM calculation is much essential to buy one of the best quality air compressors.

There is a formula for measuring the CFM. However, we have now shared some facts on the CFM value of your compressor.

  • Some manufacturers have listed the compressors’ flow in terms of the displaced CFM. This displaced CFM indicates an airflow, generated by the compressor, functioning in a 100% efficient environment.
  • Horsepower has a relation to the performance of the compressor. However, CFM calculation is more important than that. The most common rule is that 1 Horsepower has to turn out 3.5 CFM.
  • You may also find 4 to 5 CFM rate per hp. at about100 psi.
  • Rotary screw compressors may work between 1,500 CFM to 2,500 CFM.

Know these facts on CFM to have the best air compressor for your purpose.

 What Is Air Compressor Cfm Calculation Formula?

Air Compressor Cfm Calculation Formula
Air Compressor Cfm Calculation Formula

 The acronym, CFM measures the mass of the flowing air for driving it out of your compressor. However, CFM never refers to the compressed air volume. It indicates how much air is flowing on every minute. Thus, CFM is all about the mass and not about the volume. With the help of CFM calculation formula, you will be able to find out the real value.

While talking about CFM, you have to know about the other related terms. You can find that most of the manufacturers mention CFM, ACFM, NCFM and SCFM.

  • SCFM is a standard CFM that measures the airflow mass with the temperature and pressure. However, CFM calculation formula, you cannot measure the particular temperature and pressure.
  • Normal CFM denotesthe mass of airflow in normal conditions, when the relative humidity is 36%.
  • No company gives you accurate CFM, and thus, you have to calculate it by using the formula.
  • SCFM and PSI are not convertible to each other.
  • For CFM calculation, you have to make out three things- ATM of pressure, tank volume and crank time per minute.

The above information is highly relevant to the calculation of CFM.

 How Is FAD Of Compressor Calculated?

Free Air Delivery or FAD is the real amount of compressed air that is convertible to the compressor’s inlet conditions. In case of SI system, FAD unit is l/min. However, for the imperial system, this is CFM. These units are measurable as per the standard conditions of the inlet.

To measure the FAD, you have to focus on various factors

  • Ambient temperature
  • Relative Humidity
  • Ambient pressure
  • Cooling air or water
  • Working pressure

You have to know that 1 m3/min equals to 1000 liter/min. For the calculation of FAD, you have to know all these things.

For FAD, the rate of output flow can be recalculated to the rate of free air volume.

It is much challenging to measure the FAD. With the mathematical calculations and with the best flow meter, you will be able to manage it. However, you must also know the way of choosing the right flow meter. Most of the manufacturers of the air compressors have mentioned FADs at a variety of inlet conditions. That is why you have to calculate FAD in your own way, based on the above factors. You can choose the air compressor of the best performance level.

How Is CFM Air Flow Calculated?

We have found out the major things that are highly related to CFM and air flow.

  • While the tank size is larger, the air supply will be higher. Thus, you will find better CFM supply. However, this tank size is not important, when the pressure is identifiable, and you are looking for CFM.
  • Get your compressor separated from the tank. You can find a linear relationship between PSI and CFM. For instance, at 120 PSI, you will have 8 CFM. At 60 PSI, there is 4 CFM.
  • Compressor and motor- Assume that your motor is 80% efficient and your compressor is 100% efficient. A motor of 5hp can generate 10 CFM value at about 100 PSI. The right way of finding the compressor CFM airflow is to identify the steady current of the motor.

CFM is also measurable with the use of the flow meter. However, most of the methods of calculating the value is much intricate. You can try out the process by following the above steps that we have written for you.

How Is Air Compressor CFM Measured?

It is not much easy to find out the CFM of your compressor. However, we have still presented you with some steps to simplify the process for you.

  • At first, you have to know the air compressor tank volume in gallons. You can find clear marking on the tank.
  • After identifying the volume, you have to divide it by 7.48. The value obtained from the division process indicates the volume of your tank in cubic feet.
  • Take the air out of the compressor.
  • Then, refill it with the air. Track the time for refilling the tank, and you have to focus on the tank gauge of your compressor. You must also know PSIG during the refilling process. Find the differences of two PSIGs (the values at the time of kicking in and kicking out by the compressor).
  • Divide that difference by 14.7 and the outcome will reveal you the pressure level during the air filling cycle of the tank.
  • Take your tank volume unit in in cubic feet and then get it multiplied by the pressure level.
  • You will find a number at the above step, and you have to convert it to minutes. Divide this number by the time, taken by for pumping the air. Then, multiply it with 60 to have CFM value of the compressor.

Now, you can start calculating the CFM of your recently purchased air compressor and measure its performance and quality.

You May Learn More What Size Air Compressor Do I Need For Impact Wrench.

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