Guide to Calculating Dust Collection CFM

CFM is a measurement of airflow related to air conditioning, heating and ventilation environments. In dust collection applications CFM measures the amount of air per minute that can be moved from a space.

If you’re not familiar with how to calculate dust collection CFM, the process can be intimidating. In this article we will help you understand our approach to calculating CFM requirements for you. Along with the questions you should be asking your dust collection engineering firm to identify the optimal solution for your plant.

Dust Collection CFM Questions to Consider

• Where is your dust being created?


• Are you using taps or hoods at the points of dust creation?


• What type of dust are you working with?


• What are your dust characteristics?

One of the first questions we ask is, “Where is your dust being created?” This allows us to understand where your pick-up points are, and how many of those need to factor in when calculating your CFM.

Methods of Dust Collection

Once we understand where the dust is being created, then the next question becomes, "What's the best way to collect the dust at that dust creation point?" Three common methods are:

1. Tap


2. Hood


3. Articulating Arm

Many facilities include source taps at every machine. If there are no taps, then a hood or a smaller pickup point can be added. For example, a hood can be added above a table to capture dust if there is a need to constantly maneuver around the table.

If there is movement happening around the machine in different ways (e.g., leaning over a machine) then there may be a need for an articulating arm. An articulating arm allows a way for the hood or pick up duct to be as close as possible to the actual creation of the dust. As U.S. Air Filtration helps you calculate the right CFM, we will work together with you to gather these details machine by machine.

What’s Needed to Calculate CFM?

You may not know the CFM you need, but here are the things you can provide that will allow us to help solve that for you.

• How close can we get to the machine?
  
  
  
  • For example, if the machine has a six-inch tap, then we would know that would require a six-inch duct. Generally, when the machine is designed, your pickup points are also designed with the intention to efficiently capture dust.
  
  
  
  


• Blueprint of your facility or a roughly drawn layout
  
  
  
  • This helps us understand the distances between the machines, walls, and where the dust collection system will be placed.
  
  
  
  


• Photos of your machines. This helps us identify if you are using taps or hoods.
  
  
  
  • Tap
    
    
    
    • If there are no taps, how are people using the machine?
    
    
    • Is the machine stationary?
    
    
    • Does someone need access 360 degrees around the machine?
    
    
    
    
  
  
  • Hood
    
    
    
    • If there are no hoods, what is the size of the machine or table that’s creating dust? This helps us properly size a hood and with those dimensions we can look at velocity at the hood.
    
    
    
    
  
  
  
  

Then, depending on the weight of the dust, we get a better understanding of the specific velocity needed to move the dust and the duct size that’s required. These two factors together can help us get to the right CFM for your dust collection project.

Dust Collection Source Capture versus Room Capture

In the case of a grinding application, you may do all your grinding in one room and want to ventilate the entire room itself.

While the initial calculations and process to ventilate one room may seem easier, it’s not necessarily the best in terms of cost. Our recommendation is to get as close as you can get to the source of the dust, which allows you to move less air. This can mean a smaller system, which can lower the price tag of your project while also capturing dust more efficiently.

For an everyday example, let’s say you have dust all over your kitchen floor and you don't want to vacuum every square inch of it. Then your option would be to try and suck the dust up through a hood. That requires you to pull a large amount of air very quickly, which in turn requires much greater force from the fan to capture the dust. In contrast to that, if you have a vacuum and a hose, then you can pick up everything closely using a very small amount of air and suction requirements.

While it may be tempting to “just ventilate the room”, keep in mind that every CFM comes with a price tag. Moving 100,000 CFM versus 10,000 CFM is going to be more costly. The details that go into calculating your CFM may be cumbersome at first, but it will save you from spending a considerable sum of money in the long run.

Negative Impacts of Miscalculating CFM

When designing a dust collection system, it’s best to err on the high side of CFM rather than the lower side. It’s very difficult is to make a dust collection system larger once it's in place. It's much easier, if necessary, to damper the fan down or add a smaller fan.

Correcting for a larger than needed dust collection system involves adding more filter media. Upfront costs are slightly higher, but your system will work well, and you’ll be able to remove dust out of the way as you intended. The reverse isn't true. If your system is too small, it's very difficult to add filter media. Getting the dust out of your facility will always be an uphill battle. So, to reiterate when in doubt error on the high side.

• If you underestimate CFM, you won't capture the dust that you need to capture.


• The system will not work the way it was designed. Therefore, you will spend a large sum of money on maintenance expenses due to increased wear and tear..


• If you overestimate CFM, the dust collection system will work just fine, but long term you will pay 20%-30% more for a system.

Advantages of Working with USAF

One of the advantages of working with U.S. Air Filtration is that we have a team of engineers with over 40 years dust collection experience who can gather the details you provide and calculate the numbers to get you to the right CFM.

Calculating CFM and designing a system is a complex engineering process. We do all the leg work for you, so you don’t have to.

If you would like to speak to an engineer about your specific project, contact us at 888-221-0312 or email info@usairfiltration.com