Looking for a cost effective CFM meter for Dust Collector and Air Filter measurements

[Jesse Tutterrow]

The title pretty much says it all. I would like to get a meter that measures CFM (cubic feet per minute) or air movement speed that I can then calculate CFM. I want to measure the Dust Collector at different places along the pipe runs and also the output of my Grizzly hanging air filters on each speed.

Since this is not a woodworking tool that I will need to use very often I don't want to spend a lot on it.

Anyone have any recommendations?

 

[Mike Johnson]

They have some cheap anemometers listed on Ebay for around $30.00 and go up from there.

 

[Bill Boehme]

There's no such instrument as a CFM meter, but you can measure air speed as Mike suggested and taking measurements at several points to get an average velocity and using the cross sectional area, you can estimate the CFM. Don't forget to do the necessary units conversion from FPS, MPH, knots, km/h, or whatever the anemometer is displaying to feet per minute.

Once you have this number, what useful purpose will it be to you?

 

[RichColvin]

The easiest & cheapest is to use a manometer (shown below). This measures increased pressure, but it can work in reverse also. By hooking one end into your vacuum’s feed line, you can make a measure of the pulled vacuum (via the Venturi effect). Then you can find the configuration with the highest differential.

As for the liquid, just use colored water.

​

 

[Hy Tran]

The problem with the inexpensive (ebay, amazon) anemometers (measures air speed) is that they don't do really well at low air speeds. I suppose you could stick one directly in front of your duct before it's hooked up, to make sure your DC system sucks air, but dropping lint fibers or shavings in front of the DC duct would give you the same answer without having to buy an electrical or mechanical instrument...

 

[Gerald Lawrence]

https://www.woodmagazine.com/video/dust-collector-test
This video shows how Wood magazine did their test for static pressure to create the curve. They do not tell how to make the equipment but in an old issue of the magazine (maybe 10 years ago) they did show how to build a test apparatus. The whole things about this kind of test is that it is not a simple plug in and test procedure.

 

[Doug Rasmussen]

In college I had a summer job "air balancing" new buildings for a group of HVAC engineers. What this involved was going around to all the air registers and verifying air volume. Then adjusting dampers to get the registers as near to designed air volume specs as possible. Usually it was a matter of compromise...better to have all registers running at 90% of spec than some way below spec and others way over.

I can see air balancing would be helpful for a wood shop "plumbed" with a dust collection system multiple machines.

 

[robo hippy]

I am curious about why you want to measure.. There can be huge differences in 'advertised' airflow and actual airflow, and that mostly is determined by manufacturer. In looking up different systems before I purchased an Oneida, reviews said that static pressure was a more accurate and important measure when it comes to figuring how much your system can actually move. I think there are published methods for figuring how big your pipe should be, and how much they need to be stepped down as you go. For sure, the pleated paper filters are a huge improvement over the cloth bags...

robo hippy

 

[William Rogers]

There are many threads regarding CFM and dust collector size. I don't have one yet, but to me the better investment would be getting a Dylos meter. If the capture point is not very good, size of DC doesn't matter much. What is important is the amount of dust not collected and what is escaping around the source and through the DC filter. I think these meters are around $200. Knowing the dust particulate number is more important to me. Yes you need a DC that has sufficient capability, but you also need good point of collection.

 

[Jesse Tutterrow]

I am curious about why you want to measure.. There can be huge differences in 'advertised' airflow and actual airflow, and that mostly is determined by manufacturer. In looking up different systems before I purchased an Oneida, reviews said that static pressure was a more accurate and important measure when it comes to figuring how much your system can actually move. I think there are published methods for figuring how big your pipe should be, and how much they need to be stepped down as you go. For sure, the pleated paper filters are a huge improvement over the cloth bags...

robo hippy

Earlier this week I was looking at the pleated filter that I had taped to the inlet of my hanging air cleaners. It had turned from a off white to a medium gray. But is it in need of replacement? If I knew the CFM produced without the added filter, and the CFM produced with a new clean filter then I could decide if having the filter was efficient and when the air flow dropped off know it was time to replace. I was hoping to find a $30 air velocity measurer on Amazon or Ebay that would also display CFM.

 

[Bernie Hrytzak]

The manometer is your best bet, tap into the straight section of pipe pipe just before the filter, I use the manometer to determine when to clean my Oneida filter.
A clean filter gives me a pressure of 1.5 inches of water, while I consider cleaning at values of 2 inches of water or greater. This has saved me considerable time and of course ensures that I am collecting the most dust I can with this system.

 

[robo hippy]

Jesse,
I have had the same pleated filter on my Oneida dust collector for at least 15 years. Last time it needed cleaning, I took it out into the back yard and hosed out the inside. Now you have me curious if my actual air flow has gone down.... It still has lots of power. Only times it seems to go down is if I forget to clean out the barrel and the filter fills up, mostly with long shavings from the big bandsaw where I stand blocks on end and cut end grain wise... No idea about the air scrubbers...

robo hippy

 

[Dave Bunge]

Earlier this week I was looking at the pleated filter that I had taped to the inlet of my hanging air cleaners. It had turned from a off white to a medium gray. But is it in need of replacement? If I knew the CFM produced without the added filter, and the CFM produced with a new clean filter then I could decide if having the filter was efficient and when the air flow dropped off know it was time to replace. I was hoping to find a $30 air velocity measurer on Amazon or Ebay that would also display CFM.

Jesse, if I understand your question, you are trying to figure out when it's time to clean or replace the filter on the inlet of your overhead, ambient air cleaner. I will tell you my $0.01 solution to this issue. I tied a piece of ribbon, actually a some 1" plastic marking/flagging tape, to the discharge of my overhead air cleaner. When the filters are brand new, the ribbon blows straight out, is horizontal. As the inlet filter loads up, the ribbon starts to droop. When it gets to about 45*, I clean the inlet filter with my vacuum and the air flow improves. Eventually cleaning the inlet filter is not enough, and that probably means it is time to change the main filter inside the air cleaner.

I will agree with an earlier comment that the Dylos particle count meter is very helpful to determining how well your dust control measures are working.

 

[Mike Johnson]

We use a large number of filter systems on a large number of applications at the facility I work at.
Most of these applications use a differential pressure instrument that is connected on both sides of the filter
media employed for the process. This can be as simple as a manometer tube, pressure or vacuum
gauge, or transmitter that provides a digital value/signal communicated to the user or control system.
If you look on Grainger, MSC, or McMaster you can find these analog gauges that are commonly used
for these applications. Dwyer or Ashcroft makes many styles in various price ranges. You could most likely find one of these on Ebay for a decent price.