30 Gauge Ductwork

[William C Rogers]

Brian, when you say "hanger" are you talking about the perforated 3/4" steel strap? I was thinking of putting that around the pipe.

Here is what else I plan on doing. I am going to try to add a vacuum relief valve. Looked at a couple of damper style images, however cleaning a few things saw I had a left over gutter pop up. It seems to be a solution if I can get the right spring pressure balance. Nice thing is the shaft is a taper making it self center. I needed to drill a hole in the shaft for a longer screw and added spring length. Hopefully I can find the right spring balance. It fits just inside a 6" pipe.
This is the modifications I made. Won't know what spring rate until I get the system running.


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[Rick Potter]

I wonder what you have against having one gate open all the time? I have done that on two different shops with no problem. On my shop with the 1 1/2 Onieda, I left a 2 1/2" open with no gate, on the RAS. Never a problem. This was with 30 gage.

On my current shop with the 3 HP Onieda, I did the same, but usually have two 4" gates open at a time ( it works just fine), unless running the drum sander which takes a 6" drop. With your 3 HP DC, you could probably do the same, without worry, especially with 5' sections. Matter of fact, it is common for me to have the cabinet saw, 8" jointer, and RAS gates open all at the same time, not to mention that 2 1/2" open line to the RAS blade cover.

Note: I have spiral in the current shop. I give this example to show that an extra gate open should not kill your 3 HP DC. I will soon be adding a 20', 4" extension using 30 gage to my router tables.

YMMV

[Ryan Baker]

It depends on so many factors, it is hard to say what will happen. You can probably run a long time with the 30ga if you keep one gate (per branch) open all the time. It is pretty easy to get it to suck down though if you have a good collector.

With my old, small collector, there is no way I could ever suck down the 30ga pipe. There was nowhere near enough suck and way too much leaking. My cyclone could suck that down in a heartbeat and probably then pull it right through the collector. When I put in the cyclone, I rebuilt everything with spiral pipe. That's a whole other world.

[Ole Anderson]

Brian, when you say "hanger" are you talking about the perforated 3/4" steel strap? I was thinking of putting that around the pipe.

Here is what else I plan on doing. I am going to try to add a vacuum relief valve. Looked at a couple of damper style images, however cleaning a few things saw I had a left over gutter pop up. It seems to be a solution if I can get the right spring pressure balance. Nice thing is the shaft is a taper making it self center. I needed to drill a hole in the shaft for a longer screw and added spring length. Hopefully I can find the right spring balance. It fits just inside a 6" pipe.
This is the modifications I made. Won't know what spring rate until I get the system running.

And if you get the wrong spring balance and you collapse all of that 30 gauge stuff, what then? For $200 do it right the first time. Just go up from 30 ga snap lock to 26 ga snap lock, no need to go Cadillac style with spiral duct if money is the issue. No damper, no ugly rings and no diminished suction. Your dust collection system is the most important tool in your shop. Would you buy a great cabinet saw and run a cheap 24 tooth no-name blade on it? I hope not.

[Brian W Smith]

William,no on the perforated.

In HVAC world there is a name for this part......I've tried googling it several times and it just isn't coming up?Imagine two pcs of pipe/tubing that are the same diam,how can we connect them.The part is a sleeve,make it as long as you need......we use 3 and 4".The HVAC part is generally used to connect "boots" to straight tube(and that is really overslimplifying)where for a variety of reasons you can't or don't want to use a more conventional approach.

The sleeve is sized to go all the way 'round the joint,it has it's ends broke at a 90 to form flanges.It's through these flanges that we bolt this thing around the tube.Obviously everything is based on your accuracy/fit....but its pretty easy.What we do on hangars,instead of both flanges being 1/2" or so......one is left long.We still bolt it together just like the others......but this long leg serves as the standoff for that particular pce of tubing.The neat part is that it dosen't really matter which way we orient the duct....meaning,it works as well hanging from ceiling or mounted vertically.It also adapts readily when hanging at any angle to joists or whatever(you can break the long leg at the correct angle).

So,they act as connectors,they act as hangars,the side benny is they also stiffen.Not saying you should run 30g.......heck,you could "sleeve" two pcs of plastic SD together.And you can also sleeve the inside(no flanges,duh....).

*As a note,the original HVAC specs for these are quite a bit longer,guessing would say 1 1/2 X tube diam

[William C Rogers]

William,no on the perforated.

In HVAC world there is a name for this part......I've tried googling it several times and it just isn't coming up?Imagine two pcs of pipe/tubing that are the same diam,how can we connect them.The part is a sleeve,make it as long as you need......we use 3 and 4".The HVAC part is generally used to connect "boots" to straight tube(and that is really overslimplifying)where for a variety of reasons you can't or don't want to use a more conventional approach.

The sleeve is sized to go all the way 'round the joint,it has it's ends broke at a 90 to form flanges.It's through these flanges that we bolt this thing around the tube.Obviously everything is based on your accuracy/fit....but its pretty easy.What we do on hangars,instead of both flanges being 1/2" or so......one is left long.We still bolt it together just like the others......but this long leg serves as the standoff for that particular pce of tubing.The neat part is that it dosen't really matter which way we orient the duct....meaning,it works as well hanging from ceiling or mounted vertically.It also adapts readily when hanging at any angle to joists or whatever(you can break the long leg at the correct angle).

So,they act as connectors,they act as hangars,the side benny is they also stiffen.Not saying you should run 30g.......heck,you could "sleeve" two pcs of plastic SD together.And you can also sleeve the inside(no flanges,duh....).

*As a note,the original HVAC specs for these are quite a bit longer,guessing would say 1 1/2 X tube diam

Thanks Brian, I will check with my HAVC guy and see what he has. Sounds better than strap.

[Rod Sheridan]

I have seen pictures on the internet of 30 ga. ducting collapsing when all blast gates were closed.


John

And I've run mine for 20 years without issue, all depends upon the installation.

I hung mine with MDF hangers that have a cutout large enough for the pipe to slip through. (Made them on the bandsaw, don't worry about the blade entry cut, use that side on the wall/ceiling part).

The hangers provide reinforcement for the shape.

You won't have a problem with those hangers, use one on every legth of ducting, in the middle if possible. The normal crimping where they fit together provides plenty of strength at each end of the pipe.............Rod.

[John McClanahan]

Its only a work of caution, that it can happen. I don't remember what may have caused the collapse, maybe closing all blast gates while the dust collector is running.(?)

John

[Ole Anderson]

I close all of my blast gates frequently. I make a cut on the MS, close the blast gate and walk over to another part of the shop, open a gate and run the jointer. All without turning off the DC in between. It would be a pain to have to remember to always leave a gate open. Why buy the biggest, baddest DC you can afford, then compromise that DC flow and suction by leaving a gate open to save your piping? I don't get it.

[Alan Bienlein]

I made wooden hangers for mine out of scrap 1/2" plywood I had that the duct work slips thru.
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[Kent A Bathurst]

Why buy the biggest, baddest DC you can afford, then compromise that DC flow and suction by leaving a gate open to save your piping? I don't get it.

I look at it from a different perspective. You can properly design a dust sytem that will pull from multiple machines at the same time. Proper CFM, proper duct sizing from from DC thru all the drops.

In which case, you don't need to close any gates - because the system is designed to operate properly with them all open.

Or, taking one step back, design it with 2 main branches of [roughly] equal volume/flow, and then switch one gate from section A to B, but no gates downstream from there. In which case, a system with, for example, 1500 CFM capacity becomess the equivalent of a system with 3000 CFM capacity. You only need to pay for two blast gates, plus [assuming a top-notch filtration system] you are constantly pulling air from around the shop and filtering it to sub-micron or smaller.

If all you want to do is pull dust from one machine at a time, one 4" or 5" pickup at 400 - 600 CFM +/- will do it. Doesn't need to be big nor bad.

[William C Rogers]

I have read a lot on DC pipe collapse. The only pipes that have experienced collapse are 30ga. Basically (from recent memory) I have found two 8", one 7", and two 6" systems that have experienced this. I really only found the picture of the 6" by the poster on this form. Only one section of that poster's pipe collapsed. That section appears to be longer than 5 foot, but not sure. He had other sections that did not collapse that were 30ga. They were along the wall nested in wood half rings. However I found many instances where there was no problem with 30ga. From everything I have seen, it appears that installation is a key factor. On one of the 8" pipe collapse, it was replaced with the same gage with plywood rings and had no problems. I have concluded as Rod and Alan have done it is installation that is importantwhen using 30ga. With 26 ga not near as important. When the pipe collapses it changes shape and moves slightly at the end connection. It always collapses between the two end points. With a stiffener you prevent the changing of shape and screws at the connection prevent movement. Also it is more difficult to collapse a shorter length of pipe and a stiffener reduces the pipe length IMO. I will add some type of stiffener and will screw all the joints. I will go ahead and install my vacuum relief because it is easy to do. However I don't think I really need it. My system is no Dust Gorilla as my impeller is 14" vs. 15" and a little less CFM. It will cost me about $15 extra for the vacuum set up, but that is still $185 less than switching to 26ga. It will be mid January before I get this installed as I am building a wall in the workshop now. I will post my result. I do appreciate all of the input as it makes me think of different possibilities.