2" PVC dust collector pipes

[Mike Olson]

I have a cyclone with a shopvac which is setup for 2 1/2" pipes. I'm now thinking of trying to run PVC pipe along the wall to reach a few stationary machines and I'm wondering if someone could answer a few nagging questions I have.

1. How far could I run 2" PVC pipe without harming the suction too much?
2. Would i get a big drop in CFM or Suction if I went with 3" or 4" PVC pipe connected to the 2 1/2" inlet on the cyclone?
3. I have seen a few DIY projects that used hot sand to soften PVC to bend for snowshoes, i'm thinking about doing this for the bends, would that be more beneficial compared to using 2 45* angle fittings for air flow?


Thanks,
Mike

[Phil Thien]

All my tools are portable/benchtop types, so they were all designed to be used with shop-vac type systems.

I use the clear pipe solution that was sold by Rockler. Not sure if Rockler carries it any more, but Woodcraft and Lee Valley both have it, I think.

The pipes are closer to to 2-1/2", and the kits come with wyes or tees (wyes would be better but my Rockler kit came with tees). Also included are blast gates, 45 and 90-degree elbows, etc.

I also have one of my separators b4 the shop vac, and this is all I use for DC in my shop (along with an air cleaner).

It works surprisingly well. I do give up some losses to the separator and extra ductwork. BUT, I'm much more inclined to use a system where all I need to do is open a blast gate at my machine, than a system where I have to drag a hose around.

[Alan Schaffter]

I have a cyclone with a shopvac which is setup for 2 1/2" pipes. I'm now thinking of trying to run PVC pipe along the wall to reach a few stationary machines and I'm wondering if someone could answer a few nagging questions I have.

1. How far could I run 2" PVC pipe without harming the suction too much?
2. Would i get a big drop in CFM or Suction if I went with 3" or 4" PVC pipe connected to the 2 1/2" inlet on the cyclone?
3. I have seen a few DIY projects that used hot sand to soften PVC to bend for snowshoes, i'm thinking about doing this for the bends, would that be more beneficial compared to using 2 45* angle fittings for air flow?


Thanks,
Mike

As long as you are sucking from small handheld power tools you can probably run it all around your shop. Remember, that is how whole house vacuums are set up- most of those systems don't suck any harder than a shopvac.

Remember, a shopvac works differently than a dust collector- it works on static pressure (SP) to suck up stationary stuff (visualize the commercial where the vac picks up a bowling ball), while a DC works by moving large quantities of dust laden air- CFM. Shopvacs don't move much air to begin with- around 120 CFM, however the good ones have SPs in the range of 80" - 100" of H20. Dust collectors have SPs in the range of 8" - 12" H20.

Don't enlarge the pipe! Your SP and velocity will drop.

Forget trying to bend the PVC- too much of a hassle. Go to Lowes and get the gray PVC electrical conduit with long sweep bends. Use plumbing long sweep wyes instead of "Ts"

http://www.ncwoodworker.net/pp/data/1404/medium/PB050004.JPG

http://www.ncwoodworker.net/pp/data/1404/medium/PB050005.JPG

http://www.ncwoodworker.net/pp/data/1404/medium/PB050006.JPG

http://www.ncwoodworker.net/pp/data/1404/medium/PB0500161.JPG

[Mike Olson]

Ah nice idea about the conduit, I'll look at home depot tomorrow for those.

my Shopvac has just over 200cfm which was the reason I got that model.

[Alan Schaffter]

Ah nice idea about the conduit, I'll look at home depot tomorrow for those.

my Shopvac has just over 200cfm which was the reason I got that model.

Put a filter on the Shopvac, add the mini-cyclone and 15' of hose/pipe then measure the CFM! :eek:

[Mike Olson]

Put a filter on the Shopvac, add the mini-cyclone and 15' of hose/pipe then measure the CFM! :eek:

ok, any way to do that without buying a $200+ Anemometer
I found a thing on using a garbage bag for HVAC registers but at 7.48 cf in a 55 gal can liner that would be filled in less than a second which wouldn't work very well for calculations

[Alan Schaffter]

I wouldn't worry about it. You get what you get and you won't be able to do much tweaking to improve CFM from a shopvac. CFM doesn't matter with a shopvac anyway. It is insufficient to keep dust from escaping from a big machine and won't capture airborne dust worth a darn anyway, unlike a high CFM DC.

The best you can do is "trap" as much of the dust, in a small area, at the source, so the shopvac has time to suck it up. A shopvac with its high SP is best suited for use with small hand powertools (ROS, router, biscuit joiner, etc.) that have small (≤ 2") dust ports.

If you have any doubts about the differences between a shopvac and a DC with regards to capturing airborne dust. Have both ready, light up a stogy and make a cloud of smoke. Now watch how each collects the smoke. If you turn off the lights and shine a spotlight on the area you can see it better. The DC will collect the smoke from a lot more of the surrounding space a lot quicker than a shopvac.

On the opposite side (SP side) of the spectrum, use both to suck up water from a dish or plate- a shopvac will suck it up, while a DC won't do squat.