Use metal or pvc for dust collection pipe?

[Mike Heidrick]

I bought out a retiring cabinet shop's nordfab. Its great stuff when your installation environment is interesting (up super high in my case).

[Curt Harms]

I don't understand that rationale at all. You want as much suction at the machine, that will force all of the airflow to that machine and produce more airflow where you need it. Bleeding off air at any other place is simply wasting valuable potential airflow.

Ok, if you have a 3 hp blower and you are using it with an 1.25" airhose to your ROS, then maybe...but even then my rationale applies.

Static pressure is good but you also need enough air volume to allow for adequate air speed to keep dust and chips moving, not dropping out of the airstream and sitting on the bottom of the pipe. When I first installed stationary D.C. lines I'd use a 2.5" hose for something and the dust and chips would get sucked up. When I'd open a blast gate upstream from the 2.5" hose, there'd be a slug go into the blower. There wasn't enough airflow in the main line with just the 2.5" hose open. Since I've cracked an upstream blast gate no more slugs going into the blower.

[roger wiegand]

I uset metal and am very happy with it. Largely driven by the availability of Y's with all combinations of diameters and large radius elbows that I couldn't find in PVC. Sched 40 is also darn heavy to hoist up into the air in 6-8" diameters when working alone.

Little known (apparently) is the availability of duct tape back in the plumbing section that is ASTM rated for use on ducts. Works great-- when I disassembled my last system for a move after 10 years it was still like new. $12 a roll rather than $2, but makes for a nice tight system.

[Joe Jensen]

I choose metal for the following reasons:
- PVC has tight elbows, bad for flow
- PVC is heavy and larger outside for the same inside diameter
- PVC comes in 6" and 4" but no 5"
- blast gates, etc readily available for steel.
- For 6" the cost wasn't that different

[Jim Finn]

I used 26 ga. steel pipe (not spiral) and sealed all the joints and seams with a brush on sealer made for for camper tops or metal roofs. Easy to use and the pipe can easily be taken apart if necessary.

[Charles Lent]

My dust system is all PVC, even the parts that I made for it, except for the rubber couplings between the pipe and separator.

Charley

[Ben Rivel]

Metal all the way IMO.

[Frank Pratt]

I used 26ga spiral steel with long sweep fittings. Easy to install. I choose not to spend the money on Nordfab though, that stuff's crazy expensive.

If you go spiral, make sure it's externally seamed with no corrugations (smoother interior). The corrugations give more strength, but at the expense of more pressure loss.

[Benjimin Young]

thanks to all for the great information. I went with metal for the small run from the DC to the cyclone and I have a new respect for tin-bangers. only had 3 elbows and 3x30" ducts 26g but lots of frustration, clearly there are tricks to assembling the duct. The elbows fitted together nicely on the bench but again gave me trouble on the final assembly, I had to add additional crimping, more frustration... in the end it all came together but with more screws then I wanted. The very good news is Prelim ft/m meter tests indicate suction will not be an issue and I have not even applied tape yet. Once I apply tape I may remove the screws.
Next challenge, mount the cyclone platform on wheels and join it to the DC (already on wheels) and then support duct to the cyclone platform so I have one unit on wheels for cleaning and maintenance.
Pictures ad meter readings to follow.

[Benjimin Young]

My dust system is all PVC, even the parts that I made for it, except for the rubber couplings between the pipe and separator.

Charley

Where did you get the coupling? Is it 6"

[Benjimin Young]

So the metal pipe was the best solution for me as I had to adjust, adjust, adjust and adjust some more but in the end it works. It did not turn out as pretty and perfect as I envisioned, but the great part is it squeezed into its allocated space bulling with my router table for floor space, albeit with some rough cutting of the new base. The DC, cyclone and connecting duct are now one full unit so they can roll together as a unit when maintenance is needed. I still need to add a bridle rope pulley to lift the cyclone to empty the container. Then I will seal the duct with tape

Note the Plexiglas view-port on the cyclone may be a waste, already getting too foggy.
DC setup1.jpgDC-base-extended.jpgDC-base-extension-2.jpgDC-tight-space.jpgviewport.jpg

[Alan Schaffter]

Sched 40 is also darn heavy to hoist up into the air in 6-8" diameters when working alone.

Why would anyone use Sched 40??? The right stuff is thin-walled sewer and drain. Not as readily available as sched 40 but cheaper (pipe and fittings), much cheaper, and much lighter. It has different names- "solid perf" "thin-walled gravity drain, ASTM 2729, etc.

[Alan Schaffter]

I choose metal for the following reasons:
- PVC has tight elbows, bad for flow
- PVC is heavy and larger outside for the same inside diameter
- PVC comes in 6" and 4" but no 5"
- blast gates, etc readily available for steel.
- For 6" the cost wasn't that different

- Don't use elbow- use 45's and 4 wyes
- Not thin wall ASTM 2729
- true
- make your own
- yes it is. 6" ASTM 2729 pipe and fittings are cheaper than most metal

[Peter Christensen]

Why would anyone use Sched 40??? The right stuff is thin-walled sewer and drain. Not as readily available as sched 40 but cheaper (pipe and fittings), much cheaper, and much lighter. It has different names- "solid perf" "thin-walled gravity drain, ASTM 2729, etc.

Alan thin 6" and 8" S&D PVC etc., isn't readily available outside the few large urban centres we have in Canada, and if it is, it is horrendously expensive. Here in Saskatoon, largest city in the province with a population of 1/4 million, 6" was quoted to me at $10.00 to $16.00 per foot and 8" at $16.00 to $24.00. You don't even want to ask about fittings. Borg stores don't even stock 6" of any kind so it is only available from plumbing or irrigation companies. Heavier PVC or metal are the only options.

[Alan Schaffter]

Alan thin 6" and 8" S&D PVC etc., isn't readily available outside the few large urban centres we have in Canada, and if it is, it is horrendously expensive. Here in Saskatoon, largest city in the province with a population of 1/4 million, 6" was quoted to me at $10.00 to $16.00 per foot and 8" at $16.00 to $24.00. You don't even want to ask about fittings. Borg stores don't even stock 6" of any kind so it is only available from plumbing or irrigation companies. Heavier PVC or metal are the only options.

I've never seen ASTM 2729 in 8" but a few years ago, 6" went for about $15 for 10' at irrigation and some building supply stores!!! Yikes! Time to make a border run!