Dust collection tests: Different port sizes

[Allan Johanson]

Hey guys,

I had an interesting evening doing more airflow testing on my Delta 12.5" planer and Delta DJ20 jointer. My planer has the factory 4" hood and my jointer didn't come with a hood. So I made 6" hoods for my planer and jointer so I can get the most from my giant cyclone.

Before we start, I thought I'd mention that I got more airflow when my planer was actually running. So I can confidently pass on this great tip, turn your planer ON for better airflow.

On a duct run, I tried a variety of flex hose and port sizes at my planer and got the following results:

6" flex + 6" hood........779 cfm

6" flex + 4" hood........725 cfm

5" flex + 5" hood........718 cfm

4" flex + 4" hood........659 cfm

On my jointer I got the following:

6" flex + 6" hood........1029 cfm

6" flex + 4" hood........969 cfm

5" flex + 5" hood........1043 cfm

4" flex + 4" hood........811 cfm

Without any hookups to the tools, this duct flows well over 1400cfm.

With both machines hooked up at the same time with 5" flex and 5" hoods, the combined airflow is 1252 cfm.

Due to gauge reading errors, tolerance levels, etc, I expect the test results to vary by at least 20-40 cfm for each test. So don't get too picky.

When you look at those numbers, something to keep in mind is the brands of flex hose are different. The 6" hose is clear, very flexible (droopy) and has moderately heavy ribs. The 5" flex is really nice. It's grey and the ribs are very smooth on the inside. It's also not very flexible (can't bend it into a tight radius) so it isn't surprising just how well it can flow air. The 4" is your basic black 4" flex. I think this is why the jointer performed so well with the 5" flex because it's so smooth and the jointer airflow isn't being restricted much. Also, I found during testing if you lay out your flex hose in curves then you will reduce the airflow. If you straighten out the flex you'll increase the airflow. I didn't have space in my shop to be choosy so the flex curved and laid down where it wanted. Especially the 6" flex. But that's what it'll do at the tool so I wasn't too concerned.

To me, these numbers clearly indicate just how restrictive the planer is. That single 6" flex hose should be able to flow around 1150cfm in my configuration. This is an indication that you should really be paying attention to the tool itself to see if it can support the custom hood you're trying to install.

So, what does this tell you about 6" vs 4" drops and 6" vs 4" hoods? I'd say it confirms what you knew that a larger port and larger flex hose will flow more air. But now you have an indication of how much more it'll flow - at least with a large cyclone with a 7" main duct that's about 17' long and also has a few bends.

One set of tests doesn't scientifically prove anything, but would it be wrong to maybe use the following as a guideline if you want a ballpark number?

Going from 4" drop + 4" port to 6" drop + 6" port might give you a 20-30% increase in airflow at the tool.

Going from 4" drop + 4" port to 6" drop + 4" port might give you a 10-20% increase in airflow at the tool.

BTW, for this test my 5" and 6" hoses were about 10' long and the 4" was about 6' long.

I'm just trying to remove some of the mystery and unknowns from modifications like this so you all can make a more informed decision about what you'd like to do in your shop.

In the future I'll be duplicating a bunch of the tests I've been doing with a basic 1.5 - 2HP single stage DC unit. Something that more folks will have, rather than a large cyclone.

Cheers,

Allan

[Jim Dunn]

Alan is it your position that my Jet canister type dust collector would serve me better if I removed the dual 4" port system and used the 6" fitting? Also how would you incorporate a 6" dust hood to say a Dewalt or Delta planer. I can understand a DJ20 being retrofitted with a larger type hood but the Dewalt planer I have used in the past seem limited to retrofitting. Have you retrofitted a planer of any type with a larger hood? Is it a "portable" type or a larger 15" planer? Just asking cause, as usual, I'm confused.

In rereading your post I can see you used a 12.5" Delta planer. Do you have any pics of the retrofit?
Jim

[Jim Dunn]

Looks like you got me by 8 minutes. Thanks for the pics.

[Allan Johanson]

Hi Jim,

Which Jet is it? 1100 or 1200?

For both of those I'd toss the 4" ducting and start with 6". Depending on the tools and duct run the 1100 might be happier with 5" ducting so maybe I'd neck down from 6" to 5" at the first branch like Oneida tends to do.

I'm doing that with my cyclone too. I start off with 8" and then at the first wye drop to 7" to make sure the airflow is moving fast enough to go up the vertical incline in my main duct run.

The key in duct sizing is to make the ducts and ports as large as possible to flow as much air as you can, but you have to control yourself because if the ducts get too big then the velocity drops and at some point, dust particles start falling out of the airstream.

Having ducts that are too small will make sure dust never falls out of the airstream, but then this higher speed will result in higher friction losses and will reduce your overall airflow. And it can reduce it a lot.

Cheers,

Allan

[Jeff Sudmeier]

Allan,

Thank you for the detailed write up.... It really does show that you really need to get bigger ports on the tools for the highest impact. Going to 6" with 4" ports is an okay upgrade, but not really the impact we are expecting.

[Jim Becker]

Thanks, Allan. I'm really suprised you're getting that much airflow through the 4" stuff, especially the 4" drop/duct and 4" hood combination...those numbers are good for your "kick-butt" cyclone system, but probably don't represent what most folks would get from the average DC...which I suspect is about half. The velocity (FPM) you are getting would be of interest relative to these numbers.

[Allan Johanson]

You're welcome, guys.

Jim, I agree with you about getting lower airflow with a smaller DC. That's why I'd like to test one out. But the ratios might be similar, depends on a bunch of things I guess. As for the high cfm I'm getting with 4" hose, it's in line with the test in the June 2000 AWW where they took a 1.5HP Oneida and ran a 4" drop off it and got 702 cfm. My cyclone is bigger so it makes sense.

The velocity is easy to calculate. Here you go:

Planer:

6" flex + 6" hood........779 cfm....3967 fpm in 6" flex
6" flex + 4" hood........725 cfm....3692 fpm in 6" flex
5" flex + 5" hood........718 cfm....5266 fpm in 5" flex
4" flex + 4" hood........659 cfm....7552 fpm in 4" flex

Jointer:

6" flex + 6" hood........1029 cfm....5241 fpm in 6" flex
6" flex + 4" hood........969 cfm......4935 fpm in 6" flex
5" flex + 5" hood........1043 cfm....7649 fpm in 5" flex
4" flex + 4" hood........811 cfm......9293 fpm in 4" flex

9293 fpm in 4" flex on my jointer. Very insane!

Cheers,

Allan

[Terry Hatfield]

Allan,

Nice work!!!! Great info too. Thanks for doing the testing and posting the results. I'm sure it will be very helpful to many folks.

Terry

[Michael Gabbay]

Allan -

Great analysis. I have a Jet 1100 with a custom AFF top bag. I've run 6" from the DC down to 5" on the main run. The TS is hooked up to 5" but everything else is 4". I'm thinking about changing that so I can go 5" to the CMS, Jointer directly and 5" to 4" on the bandsaw, planer and router table. I'd do the 5" reduction at the tool to try and maximize the CFM.

Mike

[Rob Russell]

Allan,

Nice job on the research. A couple of questions for you:

1. What tool are you using to meaure airflow?
2. How are you measuring airflow at a machine like your planer?

Thx - Rob

[Allan Johanson]

Thanks guys!

Terry, thanks again for the assistance and inspiration.

Rob, I'm using a Dwyer 0-2" magnehelic gauge and the Dwyer 167-6 pitot tube. I also have a 0-10" gauge but most of the velocity pressure readings are under 2" so I get increased accuracy with the 0-2" gauge.

With the testing at the tools like the planer, I'm trying to simulate a real duct run and then reduce where I have to, just like in the final configuration. Here's a pic of my ducting as of about a week ago (the open run on the left has been lengthened and blocked off for now).

The 7" spiral pipe you see on the ceiling ends shortly past the right edge of the pic. From here I've added on a 90 deg bend downwards and a 30" section of 7" pipe. From there I added reducers and flex hose to go to my planer that is sitting on the floor. My jointer is there too and that's where they are going to live in my shop.

I took my measurements a couple feet to the right of the leftmost edge of the spiral pipe on the ceiling. Dwyer has specifications for pitot tube placement to ensure accurate readings. They want a length of straight pipe "10 diameters long" and to have the pitot tube inserted at least "8.5 diameters downstream and 1.5 diameters upstream" from any disturbance like elbows, wyes, etc.

So I simply hook up a tool that I want to verify how restrictive the hood may be and check the readings in the spiral pipe. I tested my Performax 16-32 last night and I have some work to do on that puppy.

My goal with all the tools is to run the 7" solid pipe as far as I can and then take an airflow reading in the main duct. Then hooking up the tool using multiple hoods where possible, try to make sure the airflow in the main duct is as close to the original reading (without the tool) as possible. Within 100cfm and I'll be happy. But if a branch is flowing 1400 cfm without the tool and the tool is only allowing 800 cfm, then I'm not happy. I have lots more work to do.

Cheers,

Allan