How to measure dust collector performance.

[Vaughn Kaloust]

Hi to all. This is my first post, but I sure have been reading a lot, and getting great info here.

After 40 years of abstinence, I am about to start working with wood again. I have set up a decent shop to begin my retirement, which includes dust collection through a separator. However, I am now trying to optimize the system, and was wondering if anyone has suggestions on how to measure the effectiveness of any adjustments I make.

I have seen CFM meters that look like they could do the job, but they range from $35- $500! Also, I am not sure that this tool would provide me with all the measurements I need to gauge performance of each section of the system.

I have read many posts about dust collection systems, but have yet to find any mention of a method or procedure for accurately measuring performance.

I am hoping someone can point me in the right direction.

Thanks

[Ole Anderson]

Vaughn, welcome to the Creek! Please edit your information to include your location, always good to know where you are from as folks from all over the world post here.

Depends on what you are trying to measure, cfm or dust particle removal efficiency. If cfm is your goal, best way is to measure the duct velocity just ahead of the separator in a straight section of smooth duct. Several ways to do this, but an anemometer isn't one of them. That is what I have (a Velocitor) and you are limited to measuring the velocity at the end of a duct or hose where you have access. Best to get a proper pitot tube with two connections, one for static pressure the other that is aimed into the airstream. The pitot tube should come with a calibration curve and coupled with the area of the duct, you can plot a differential static pressure vs cfm curve. You can make up a manometer with two dollars worth of 3/16" clear vinyl hose and some water with food coloring added or you can get a Dwyer magnehelic gauge for $30 to $40 on EBay. With this setup you can measure all combinations of gate openings and hood and duct/flex hose changes without relocating the pitot tube.

[David Kumm]

The velocitor Ole and I use is helpful in telling you the cfm available at the end of the hose going into each machine but will not tell you how the hood restricts that airflow if at all. The magneholic gauge will help you with that. I display amp draw continuously on my vfd so I just compare the draw with the hose not attached and then attached to see if there is internal restriction. It is useful to take readings without machines attached to get an idea of the real airflow the system is capable of delivering at each location. Even with a restriction inside the machine, more air entering means more air flowing through the restriction. Dave

[Vaughn Kaloust]

OK, now we’re talking. Thanks for the info.

I should have been more specific with my question. I am thinking that the end result is where the collection is done at each machine, so that is what I am trying to measure.

I thought that if I measured the velocity at the drop to each machine, (just before the connection to the machine), that should give me an idea if my suction is sufficient.

I will start looking for the pitot tube, but I have no idea what a velocitor is, and when I Google it, all I get is information on ammunition.

For the manometer, no problem, I have everything I need.

Ahhh, Velocitor is the brand of anemometer, right? Like this?
http://www.centurytool.net/AM50_CPS_..._p/cpsam50.htm

Now I am a little confused, because it sounds like this is where I started.

Can I simply use an anemometer at the end of each open duct, just before it enters the machine, to get the velocity and CFM? Wouldn’t those two numbers tell me if I have enough draw for that particular machine?

I will check into the pitot , magneholic gauge, and anything else I can find.

If anyone can direct me to a website that describes these tools and procedures, I would appreciate it.

[David Kumm]

Yes, the fan blade anemometer like the Velocitor or UEI DAFM is what I use. You move it around the opening and will see some variation in readings-10% or so. Take a rough average and convert to cfm. That will give you a pretty good idea of what cfm you have at each machine. If the machine says it needs 500 cfm and you have more life is good. Assuming the hood costs some and most machines can benefit from more than what is stated you want a good margin in excess. If you want to find out if the hood or internal routing is costing or if you need more make up air to satisfy the airflow you need further testing at the inlet. Dave

[Eric Kipker]

I would recommend you go visit Bill Pentz's web site, before you purchase any meters. It is free and he has done a lot of the leg work. I managed the R&D department for a very large HVAC manufacturer before retiring, and had access to all kinds of meters while I was building my dust collection system, but never saw a need to bring a meter home, especially after reading through Bill's entire web site.

[Michael W. Clark]

Here is a link for the pitot tubes
http://www.dwyer-inst.com/PDF_files/122d.pdf I would recommend the 167-12 for home use.

A u-tube manometer is probably the most veratile and cheapest. If you get a magnehellic, you will need two for the pressure range if you want to measure static pressure as well. For airflows, you want 0-2"wc (4005 FPM = 1"VP). For SP, you may want to be able to go to -10"wg, maybe higher depending on your system.

http://www.dwyer-inst.com/PDF_files/004.005.d.pdf You would probably best served with the 2002 and 2010 models
http://www.dwyer-inst.com/PDF_files/1211.d.pdf Probably the 1211-12 or 1211-16 would be best (don't forget the gauge fluid and tubing, but it maybe in the kit)

Mike

[David Kumm]

Eric, Bill's site had the opposite effect on me. Maybe because I don't believe anything I read without some verification I wanted to know what the numbers were for my system. Not knowing the pressure drop of my cyclone or filters but knowing the fan curve of my Cincinnati blower, I needed some way to figure out cfm and how swapping a length of 7" for 8" etc affected the flow or what a drop of 6" necked to 4" delivered vs a full length of 4". There is no way to calculate that given the info we have available. Bill has written his stuff over a period of time so even his views have been refined and even modified. Most of the testing stuff costs less than choosing an incorrect sized pipe and fittings. Dave

[Ole Anderson]

A u-tube manometer is probably the most veratile and cheapest. If you get a magnehellic, you will need two for the pressure range if you want to measure static pressure as well. For airflows, you want 0-2"wc (4005 FPM = 1"VP). For SP, you may want to be able to go to -10"wg, maybe higher depending on your system.

Mike

Make that three if you want to keep track of filter losses. After a while, that becomes the go-to gauge, everything else is a one-time measurement. Sometimes with my saw running I glance up at my gauges to make sure I turned on the DC. A low filter gauge reading means I remembered to close my last open gate before opening another.

[michael osadchuk]

Vaughan

A different way to go is to buy an dust particle counter such as

www.dylosproducts.com

which is very useful in detecting problems in new dust collection points as well as more directly advising you of the air quality in the workshop.

More than a few woodworkers have the Dylos so if you do a search for 'dylos' in this forum you should get some further information on this option.

good luck

michael

[Bernie May]

I second getting a Dylos meter. Best investment ever. First thing I turn on in the shop before I start. I was totally surprised at what I learned about the dust collection at different machines. who knew drill presses made so much dust or sweeping for that matter.

[Vaughn Kaloust]

Thanks for all the advice and suggestions.

To start, I made a manometer from some plastic tubing and a yard stick. I used a plate with the clear tube mounted to it to measure at different tools in various points in my shop.

Although this tells me almost nothing about CFM or how truly effective dust collection will be at any particular tool, I thought it would give me some idea of how tight my system is.

I was a little surprised at the results??

1) I think my system is indeed pretty tight, as I could not find any difference in the vacuum at any of my outlets. All measured the same, or the difference was so small I could not detect it on my simple manometer.

2) Now, keeping in mind that I live at 5,000 feet in Denver, so I could never achieve the same type of vacuum that could be done at sea level. I could only pull about 3” on my manometer? This is much less than I expected, but I have no benchmark to measure this by, and maybe this is normal for a dust collector of this size.

I have a HF collector with the stock bag that came with it. But I had the outlet disconnected and made my first measurement directly at the inlet (the grate/grill is still in place as I have yet to remove it).
Just for fun I connected my shop vac up and did the same test, and of course it pulled enough of a vacuum to start sucking the water out of my manometer.

Does 3 inches of vacuum seem normal (at 5,000 foot altitude)?

Thanks

[Paul Stoops]

Hi Vaughn,

Welcome to Sawmill Creek Forum!

Am I understanding you correctly that you blocked off your fan inlet with a plate and attached a manometer and got a reading of 3" WC? What is the HP of your DC motor? Do you know what the diameter of the fan impeller is?
That reading seems quite low, unless you have some serious leaks somewhere. I am not familiar with the HF dust collectors, but I would expect a static pressure of at least 6"-8" WC (or more) at the inlet with no back pressure from the outlet.
Has anyone on the forum measured the static pressure of an HF dust collector? Would the altitude in Denver affect the SP that much?

To measure CFM airflow in the ducts you will need additional test gear, as the folks above have explained. But it seems to me that it would be prudent to first understand why your static pressure is so low. There is a lot of experience in this area here on the SC forum, so we should be able to help you. Be patient, this DC stuff can be knarly.....................:-)

[Michael W. Clark]

3" at the hood is good, kind of low at the fan inlet.
Mike

[David Kumm]

The altitude correction factor is about 1.2 at 70 degrees and 5000 ft. Some harbor freight collectors run with a forward inclined blade. Provides high cfm at low pressure but really craps out a high. If you are running that configuration I would expect low but not that low. Dave