30 Gage Metal Duct Pipe can Collapse

[Ole Anderson]

I sense that I'm being baited into an argument.

So instead, how about you get right to it and share your concerns?

I was simply asking if your conclusion from his test was that 30 gauge pipe is appropriate for a DC system. That is how I took your comment, but it wasn't clear. To me, his test conclusion appeared to be that in order for 30 gauge pipe to survive you must use stiffening rings. Which is Ok if that is how you choose to build your collection system. As you know by now, I try to steer anyone within earshot away from using 30 gauge duct for a dust collection system. It gives metal collection systems a bad name when they fail, and I believe that metal should be the first choice of materials. My personal view as well as the view of professional installers (using steel). There, you got it.

[Peter Aeschliman]

Got it. Thanks. I misread your tone. My apologies.

What other concerns do you have aside from collapsing? The OP has found a reasonable solution, so I'm assuming you have other issues? I.e., are the joints not smooth enough and could thus cause clogging?

Seems to me that if you can keep it from collapsing, it's a good option for those who are budget conscious and want 6" ducting... unless there's something I'm missing.

[Ryan Baker]

I would also like to thank the OP for posting the test results. I would just caution not to interpret the results too broadly. Changing the collector, duct setup, etc. can and will produce different results (in either direction) -- in other words it all depends on the situation and YMMV.

I would offer a couple other suggestions when using 30ga pipe. Be sure to fully seal all the joints and all the lengthwise pipe seams. I have tried it both ways and you would be stunned how much loss you get from leakage through those seams (even just the lengthwise seams). Foil tape works well. That's like adding another HP to your collector. Also, be careful not to bump into and dent those pipes, as that will greatly increase the chances of sucking it down.

[Ole Anderson]

The only difference between 30 gauge snap lock and 26 gauge snap lock is the thickness and resulting rigidity. 30 gauge is easy to dent, 26 gauge is MUCH stronger in that category. Joints and seams are the same. Agreeing with Ryan, tape the straight joints and seams with aluminum duct tape (regular duct tapes works for everything BUT ducts) and run a thin bead of clear silicone along each joint in your fitting that can't be easily taped. You can use duct sealing mastic, but the silicone looks much better. Check this out: http://www.sawmillcreek.org/showthre...tall&highlight=

[William C Rogers]

This exactly. I think I mentioned this in your other thread. I have neaver sean a spring loaded vacuum relief in dust collection (yes for pneumatic conveying systems with PD blowers, but that is different altogether).

As far as 30 ga used for DC, if you can make it work in a home shop, why not? Most of the duct mentioned on here is not meant for DC anyway. S&D, PVC, 30ga or 26ga KD (knock-down), metal spiral...none of it was designed for wood shop DC, but we are adapting it for home shop hobby use.

Industrial/Commercial DC ductwork should be metal (conductive) for wood dust and meet the appropriate SMACNA standard. I think minimum SMACNA is 18 gauge for dust collection for full pen welds. HVAC systems do not handle the dust loading (neither do HVAC filters!) of a DC system nor do they approach the negative static pressures often present in dust collection systems.

Mike

I tried the spring loaded vacuum vacuum because it was what I had on hand. It would be very difficult to make that system work IMO. I don't need the vacuum relief for the system to work, but it would be an advantage. When I put the pipe seams at 90 degrees the pipe didn't collapse. I think I would eliminate the plywood rings where not needed for installation if I can make a damper system work. A relief system will lessen the shock and the flex hose trying to contract.
Bill, I'll have to look at the barometric damper. I'm not familiar with them, but that may be the ticket. Even with the damper I figured that would need to be 24 gauge for stability.
Ole, thanks for the link on your install, interesting read.
I am running electric to my wall and will finish that today, but won't be in the shop again until after the holidays. I think I will set the make shift system back up and see if I can get a damper system to work. I know it won't be final and need to be redone due to actual system losses. It will be after the first of the year before I can play again.
Thanks to all for the inputs.

Happy Holidays and Happy New Year to everyone.

[Michael W. Clark]

The benefit to the damper style is that it opens fully, passes more air at a lower pressure drop. It also can be tuned to partially open if you have a single 4" gate open and want to make sure you have enough flow in the 6" main to keep dust from dropping out.