Installing ductwork for dust collector? Pics

[Steve Mathews]

I just ordered most of the ducts and fittings for my dust collection system. A few questions remain for the install that I'm hoping to resolve here. Photos are included below to give some sense of what I'm trying to accomplish. The first photo below shows a rough sketch of the layout. Along the wall where most of the drops will take place I was thinking of rolling the wye outlet about 45 deg. downward and connect the drop with an adjustable 90 deg. ell, essentially making it a rolling 45 deg. transition. I thought of doing this instead of having the wye outlet horizontal and dropping down with a straight 90 deg. ell. First of all, does anyone see any problems with this approach.
Dust Collection 006.jpg

Here's a photo of the wall where most of the outlets take place. I plan to run the duct above the wall ties as close to the wall as possible.
Dust Collection 001.jpg

Here's a photo of the dust collector. I have to rise up from the outlet to before getting to the wall. Would a couple of 45 deg. ells be better than using flexible hose. The size of duct at this point is 8"
Dust Collection 003.jpg

And lastly here is a photo of the dust collector installed in it's temporary location before I get a chance to add on a mechanical room. I may also hook up the compressor shown for my next project, installing shop air.
Dust Collection 002.jpgDust Collection 004.jpg

[Malcolm McLeod]

After an epoch of research, I just put in an EF-5, and phase 1 of my ducting. Biggest thing I came away with after all the angst and engineering was the inlet duct run to the cyclone. People drop in 3-5 Hp of fan and then kill their air flow by installing 2 90*Elbows on the inlet to get to their horizontal run. This induces turbulence right at the inlet with no chance for the air to return to laminar flow.

Turbulent flow means the dust is moving in random directions - - but still forward with some average velocity.

Laminar flow means you have a fairly consistent velocity over the majority of the duct's cross section. This means the dust has the most possible kinetic energy as it hits the cyclone = hugs the wall = separates from the air. My advice is find a way - even if a bit inconvenient - to get a straight run ~10x the duct diameter into the cyclone. So, if you have 6" duct = 60" of straight duct.

- - not sure of my audience, so pardon the mini-fluid-dynamics course.

[Ken Fitzgerald]

Steve,

Here's a thread showing how I installed mine. https://sawmillcreek.org/showthread....me-DC-progress

[David L Morse]

After an epoch of research, I just put in an EF-5, and phase 1 of my ducting. Biggest thing I came away with after all the angst and engineering was the inlet duct run to the cyclone. People drop in 3-5 Hp of fan and then kill their air flow by installing 2 90*Elbows on the inlet to get to their horizontal run. This induces turbulence right at the inlet with no chance for the air to return to laminar flow.

Turbulent flow means the dust is moving in random directions - - but still forward with some average velocity.

Laminar flow means you have a fairly consistent velocity over the majority of the duct's cross section. This means the dust has the most possible kinetic energy as it hits the cyclone = hugs the wall = separates from the air. My advice is find a way - even if a bit inconvenient - to get a straight run ~10x the duct diameter into the cyclone. So, if you have 6" duct = 60" of straight duct.

- - not sure of my audience, so pardon the mini-fluid-dynamics course.

Malcolm, I don't know if you really meant laminar flow in the technical sense, but if you check the Reynolds number for typical dust collection velocities and duct sizes you'll see that it's all turbulent flow, not even close to laminar.

[Steve Mathews]

Ken - Thanks for the link to the thread about your duct install. That was very helpful.

Here's a not much better sketch showing my intended layout. I'm trying to stay close to the one wall with the main run because 1) that's where most of the equipment is located and 2) the height for attaching hangers is much lower. I'm still a little concerned about rolling the laterals to the drops and making an elevation change at the DC. My plan for the latter at the moment is to use a couple of 45s along with a short section of hose to compensate for vibration at the DC. Again, any suggestions are most appreciated.Dust Collection 008.jpg

[Ryan Yeaglin]

Steve, as someone who works in the trades I can appreciate your drafting skills!

[Steve Mathews]

Forgot to mention that I'll probably exhaust the DC outside without filtering for now. That's the direction shown in one of the photos. My closest neighbor is at least a couple hundred yards away. It may be a good idea to install some type of louver or flexible gate to keep bugs and critters out.

[Malcolm McLeod]

True dat. But audience :: I needed to use some term to delineate difference in flow. (Not sure how many here speak Reynolds).

[Thomas Wilson]

True dat. But audience :: I needed to use some term to delineate difference in flow. (Not sure how many here speak Reynolds).

The term you are looking for is “fully developed” meaning that the effects of elbows on the velocity profile have decayed away. Typical straight pipe distances of 5 to 10 pipe diameters are needed for fully developed turbulent flow.

[Jim Becker]

You can use adjustable elbows to do the slight bends that get "down" to your inlet from your intended duct height. Ideally, you want a few feet of straight run into the cyclone inlet before any direction changes, but sometimes you have to do what you have to do and if the bend is very gentle, you'll be fine. NEVER use flex hose for this kind of thing, however. If you do use this technique once you have everything set with the angles and you confirm it's how you want it, be sure to fully seal up the ten billion joints in the adjustable elbows with mastic and/or foil tape.

[David L Morse]

True dat. But audience :: I needed to use some term to delineate difference in flow. (Not sure how many here speak Reynolds).

You're right, context is important. I didn't mean to sound like a 240 vs 220 pedant.

I sometimes call it "undisturbed" or "reasonably uniform".

The term you are looking for is “fully developed” meaning that the effects of elbows on the velocity profile have decayed away. Typical straight pipe distances of 5 to 10 pipe diameters are needed for fully developed turbulent flow.

Well, at dust collection velocities you need more than 10D to get fully developed flow. But 5D to 10D from a disturbance is usually good enough for both testing and not too much system effect (interaction between closely spaced components).

There's a difference between what's agreed upon for reproducible testing and what's required for actual operation. Per AMCA a 10D test pipe is used for testing DC type fans. That convention has been extended to the testing of cyclone-fronted hobbyist dust collector systems. That means you should be able to reproduce a manufacturer's test data if you're careful. It doesn't mean the system quits working if you only have 1D, just that you get different (usually not as good) results.

So, a 90 close to the input of a cyclone will almost certainly increase the loss coefficients of both the 90 and the cyclone (system effect). It will also change the collection efficiency vs particle size curve, probably spreading the transition region somewhat. I think the overall impact of that will be a lot less than a reduction in airflow or a collection bin leak. That's an opinion, I've not seen any actual data on what inlet disturbances do to collection efficiency.

[Steve Mathews]

After an epoch of research, I just put in an EF-5, and phase 1 of my ducting. Biggest thing I came away with after all the angst and engineering was the inlet duct run to the cyclone. People drop in 3-5 Hp of fan and then kill their air flow by installing 2 90*Elbows on the inlet to get to their horizontal run. This induces turbulence right at the inlet with no chance for the air to return to laminar flow.

Turbulent flow means the dust is moving in random directions - - but still forward with some average velocity.

Laminar flow means you have a fairly consistent velocity over the majority of the duct's cross section. This means the dust has the most possible kinetic energy as it hits the cyclone = hugs the wall = separates from the air. My advice is find a way - even if a bit inconvenient - to get a straight run ~10x the duct diameter into the cyclone. So, if you have 6" duct = 60" of straight duct.

- - not sure of my audience, so pardon the mini-fluid-dynamics course.

Actually, I may be able to run straight into the DC inlet by lowering the 8" duct along the back wall to 7'. Supporting wouldn't be a problem because it would be bracketed to the wall. Two 45 deg. ells would also be eliminated in the process. The more I think about it the better I like it. Thanks Malcolm!

PS I don't know if this is relevant to air flow but straightening vanes are frequently used in hydraulics, especially at inlets to pumps to reduce turbulence. Maybe it can also be applied to air flow.

[michael dilday]

I don't really understand what you mean by "rolling the wye outlet about 45 deg. downward and connect the drop with an adjustable 90 deg. ell, essentially making it a rolling 45 deg. transition". My system has a 3 hp Jet Cyclone and I drop from a 9' ceiling with a 90 directly into the cyclone using spiral steel pipe. My cyclone separates nearly 100%. Filling a 55 gallon drum and I may get a few tablespoons past the cyclone into the canister bag. I do understand about the straight pipe into the cyclone but in my shop it just didn't work out. One thing I might be able to add is the 45's out of the main should be horizontal there 90 for each drop. This will keep debris from dropping into the drops and clogging.

[Matt Day]

So it looks like you have a change in ceiling height, just north of your DC, right? If you keep your layout, I’d run 5-6’ of straight pipe before any 45’s.

Have you considered a straight run diagonally from your DC and branching off from there? So from the DC toward the bandsaw? At some point, maybe after 8’ you could roll the main above the ceiling joists if you wanted.

[Steve Mathews]

Clarifying what I'm planning to do now ... The 8" duct coming straight out of the DC will be about 7' high until just past the lathe. That should provide over 20' of straight duct to the DC. The 6" branch at the 8"x4"x6" wye will be pointed up at some angle to receive a short section of 6" duct and an adjustable 6" ell at about 10' high. This will be height of the remaining 6" run, which will be just above the wall ties. Delete Section A-A in the last sketch. There are no fittings immediately after the DC.