How to Calculate Vacuum Flow Rate

Are You Wondering How to Calculate a Vacuum Flow Rate?

Well, this article covers all the necessary details. Therefore, keep reading and stay with us till the end to better understand how to calculate a vacuum flow rate.


What Does Vacuum Flow Rate Mean 

Vacuum flow rate is the volume of the air that measures how quickly the air is suctioned. On the other hand, Volumetric flow rate is the flow of fluid that passes per unit of time.

Some Common Flow Rate Units 

Here are some commonly used units to calculating vacuum flow rates;


  • cubic feet per minute, 
  • liters per minute, and
  • Gallons per minute. 

However, the units of volumetric flow rate can be interchangeable with millimeters, inches, feet, etc. 

SI Units of Volumetric Flow Rate 

The SI units of the volumetric flow rate of vacuum are meters cube per second, milliliters per second, and feet cube per hour. 

How to Calculate the Vacuum Flow Rate 

For this, we use Chamber evacuation Calculators, which are used to determine the flow rate of the vacuum to a specified pressure level. Follow the given steps to calculate;

1.    Enter Volume

In the calculator, enter the volume that is evacuated in liters.

2.    Add Time

Enter the time in minutes to the vacuum’s evacuated volume. 

3.    Insert Initial Pressure Value

Then put the initial pressure in the torr at which the pump begins to work, which is 760 torr. Last, put in the final pressure at which the evacuation of the chamber was completed. 

Moreover, the leak rate of the vacuum is optional. If your vacuum has a leak rate, then measure the leak rate. 

How to Measure the Leak Rate of a Vacuum 

To measure the leak flow rate of the vacuum, 

  1. Close the inlet and outlet openings. Only open the end that leads to the pump. Open the pump and start it. 
  2. Measure the leak rate by pumping to the known pressure. At this time, record the pressure.
  1. Then turn off the pump and allow the pressure to rise for one to five minutes. Also, measure the pressure at the end.
  2. Calculate the leak rate by dividing the change in pressure over time.

Calculate The Flow Rate of Vacuum 

After measuring the volume of air, time, initial and final pressure, and leak rate of your vacuum, calculate the flow rate of vacuum in meter cube per hour. 

Measurement of Volumetric Flow Rate 

To present the vacuum system performance, it is important to understand the flow rating and pump curves. In most cases, the manufacturers give only a single unit of flow rating. If we use the CFM unit, the manufacturer gives the value of the standard cube feet per minute (SCFM). 

Standard Cube Feet Per Minute (SCFM) 

SCFM is the rating of the amount of flow of the vacuum pump. The SCFM is the flow rate of the vacuum pump at room temperature and atmospheric pressure, which is known as zero vacuum. Nevertheless, the SCFM is not the actual value because the conditions change at the point of use.  

Actual Cube Feet Per Minute (ACFM) 

The conditions that are not met by the standard cube feet meter are fulfilled by actual cube feet per minute (ACFM). Whereas, actual cube feet per minute is the condition at which the pump curves are introduced. It describes how well the vacuum pump will work under the actual cubic feet per minute condition.

in addition, if we make a graph between the vacuum level and the flow rate of two pump curves. The one curve will have a higher ACFM level than the other curve. It means that the higher ACFM curve has a higher flow rate capacity. Although, the standard cube feet per minute are the same for both pump curves. Then the rating flow of ACFM is crucial in many conditions. Pump curves are available to the manufacturer. Read these curves if the flow rate is contributing as the vacuum level increases.  

What Do You Know About Vacuum Level 

The vacuum level is the measurement of vacuum pressure using a measurement scale in a system.  The level of vacuum measures the vacuum pressure level in relation to the atmospheric pressure or determines how much the vacuum pressure is close to the absolute pressure, which is zero. The vacuum level and the flow rate of the vacuum are related to each other. 

Devices to Measure the Vacuum Flow Rate 

Devices such as flow meters are used to measure the flow rate of a vacuum. Other than flow meters, some vacuums use digital readouts. But simple dial readers are also available nowadays. It should be considered that the standard and actual ratings are used in examples. The flow meter is an instrument to measure the amount of fluid, gas, or steam in the flow sensor. The vacuum flow rate is measured by a flow meter sensor.

Helpful Tips to Make Your Vacuum Last Long

The most important factor in making your machine last long is cleaning it on a regular basis. For this, follow the below-mentioned steps;

  1. Unplug your vacuum cleaner from the main power supply.
  2. Clear out the dust canister.
  3. Properly remove the filter and rinse it with water. 
  4. Now, clean the roller brush of your cleaner
  5. Unclog your vacuum’s hose.
  6. Don’t forget to clean the exposed parts of the vacuum cleaner.

Bottom Line

Well, it is imperative to know the flow rate of your vacuum because it determines the volume of the air that moves in your machine over time. Having a better understanding of flow rates and their units plays a significant role in the performance of your appliance. Protection Status
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