Cyclone Ducting

[Jamie Buxton]

Well if you're still skeptical here is the 30 gauge 8" duct I got from HD. That was on my Clearvue CV1800, and that was downstream of a 4" branch.

You might be able to get away with it for 6" ducts, but why risk it? The 26 gauge stuff that I got from a HVAC supply house was only like 5 bucks more for 10'.

Did you have all the blast gates closed when the duct collapsed?

[Jim German]

did that happen as soon as you started up the ClearVue ??

Yep
I believe I had a 4" gate open at the end, they might have all been closed though.

[Alan Bienlein]

I get a kick out of reading about don't buy the snap loc from the home centers as it's to thin and will immediately collapse on you. I say hog wash as my whole system is done with the snap loc from Lowes and Home Depot. I can close all blast gates with out fear of collapse and I run the same 16" impeller and 5 hp motor as the Clear Vue on my cyclone.

The difference between me being able to use it and others having it collapse is all in how you hang your duct. If you want to be lazy and just use a strap or a tie wrap to hang it it will definitely collapse but if you take the time to make a ring out of some 1/2" ply to slide over the duct work then it WILL NOT collapse.

[Jim German]

I get a kick out of reading about don't buy the snap loc from the home centers as it's to thin and will immediately collapse on you. I say hog wash as my whole system is done with the snap loc from Lowes and Home Depot. I can close all blast gates with out fear of collapse and I run the same 16" impeller and 5 hp motor as the Clear Vue on my cyclone.

The difference between me being able to use it and others having it collapse is all in how you hang your duct. If you want to be lazy and just use a strap or a tie wrap to hang it it will definitely collapse but if you take the time to make a ring out of some 1/2" ply to slide over the duct work then it WILL NOT collapse.

Sure, sure you can reinforce your 30g ductwork (which is what you're doing with your ply). Or you could just spend a couple bucks more and get thicker stuff.

[Paul McGaha]

I've seen pictures of thin gauge duct collapse from being connected to a cyclone.

When I did my system I bought the spiral duct and fittings from Oneida. If I had to do it again I would buy the fittings from Oneida and try to buy the spiral duct local (It's expensive to ship).

Oneida has really high quality elbows. Long sweep, heavy duty, perfect for dust collection.

I'm not experienced with the duct and fittings from Penn State Industries.

Good luck with it.

PHM

Edit - I just looked at the Penn State Industries duct and fittings, It looked like quality material to me.

[Alan Bienlein]

Sure, sure you can reinforce your 30g ductwork (which is what you're doing with your ply). Or you could just spend a couple bucks more and get thicker stuff.

I would be spending more than a few dollars trying to locate "the thicker stuff". The home centers are a lot more convenient and making simple brackets like shown in this picture from scrap lying around the shop serves two purposes. It provides a convenient way to support the duct work and yes it reinforces the duct work in that it is forced to stay round with a negative pressure inside.
7-5-09 1004.jpg

[Michael W. Clark]

Alan,
I was thinking stiffeners too when thinner duct was first mentioned in this thread. How are you attaching the plywood rings to the duct and how often are you spacing them?

I can't find any pressure ratings or stiffening requirements in the industrial references I have. They only go down to 22 ga.

Mike

[Brett Bobo]

That's a clever idea and interestingly enough, ring stiffeners are commonly used to strengthen steel tubular members in the offshore industry.

[Michael Mahan]

I would be spending more than a few dollars trying to locate "the thicker stuff". The home centers are a lot more convenient and making simple brackets like shown in this picture from scrap lying around the shop serves two purposes. It provides a convenient way to support the duct work and yes it reinforces the duct work in that it is forced to stay round with a negative pressure inside.
7-5-09 1004.jpg

that's a GREAT Idea ! the more u use the better & doubles as hanger as well , best of all it looks to be clean install

[Joseph Fronio]

Thanks for all the great advice. Really helpful. I may stear clear of hd and go through a hvac dealer for the straight pipe.
Sounds like its a good idea to get the fittings through oneida or penn state. Why don't hvac fittings work for dust collection?

[David Kumm]

Also look at Kencraft for fittings. They are reasonable and work well with spiral too. Blastgate co fittings are undersized and don't maintain the inside to outside assembly that is preferred. HVAC fittings are used when you need adjustability but are short radius ells and you should stay with 2.5 x radius when you can and no less that 1.5x radius. No Tees. Wyes are usually backwards relative to DC fittings in the way they attach to the pipe because they are designed for blowing air rather than pulling it. Dave

[Michael W. Clark]

Joseph,
If you are referring to my comment abou the HVAC fittings, I was mainly referring to the spiral HVAC fittings for Brett at the spiral duct fabricators. A lot of them don't do tee-on taper fittings or laterals. In HVAC, you are running much lower velocity and very little (if any) appreciable dust load. They use tees, and reducers in-line when they branch. They also use elbows that are usually a 1D radius, sometimes 1.5D.

Contact a local residential HVAC company and price duct and fittings from them or find out where they get their duct. You often see it referred to as KD (knock-down) duct. I found a supplier close to here. I emailed them my list of fittings, then sent back an itemized price list and part numbers, said they could deliver it the next day for $10 extra when I'm ready.

[Alan Bienlein]

Alan,
I was thinking stiffeners too when thinner duct was first mentioned in this thread. How are you attaching the plywood rings to the duct and how often are you spacing them?

I can't find any pressure ratings or stiffening requirements in the industrial references I have. They only go down to 22 ga.

Mike

If it's a long run with multiple full length straight sections then I use one at each joint. They are easy to make as I used the same setup as I used to make my blast gates.

The rings are a snug slip fit. After I did mine I read about some one who made theirs either in two pieces or was it one piece that was cut on one side and when they put the pipe in they tightened the screw to clamp it in place.

The blast gates are held to the end of the duct work by 18 gauge brad nails I shot through a piece of thin wood so it wouldn't go thru the metal and lightly tapped them the rest of the way with a small hammer.

[Ole Anderson]

Stiffening rings aren't needed with 26 ga or heavier pipe. As stated multiple times don't use 30 ga pipe and you won't need rings. Use short 1/8" x 1/8" pop rivets at 12:00, 4:00 and 8:00 for connecting steel pipe and fittings. Best to rivet after you tape the joints with aluminum HVAC tape. http://www.sawmillcreek.org/showthre...tall&highlight=

[Michael W. Clark]

I agree, 26 ga. is preferred, but it is not as easily available to some. I had trouble finding it locally, took me awhile and I live near a major city. Most probably have access to the 30 ga stuff and the stiffening solution may be appealing.

In industrial systems (SMACNA), minimum gauge is spec'd by the class primarily for abrasion/errosion resistance. On a spec job, the SMACNA class is given, flows and SP, along with material bulk density. It is up to the duct supplier and installer to determine the most economical combination of gauge, stiffening, and support spacing.