Bends in dust collection

[paul cottingham]

Quick question:

Am I better off with 2 90 degree bends in 4" abs, or 1 90 degree abs corner and the other bend in flex hose? Or would it make any difference? I am plumbing dust collection for my jointer, and am using a puny 800 cfm 1 hp dust extractor. The way it is set up now with flex is working, but I suspect it could be much more efficient.

Thanks in advance.

[Dave Gaul]

90's and flex pipe kill you cfm's

2 45's are better than one 90, and longer bends are better than short/sharp bends

flex pipe is obviously not always avoidable, but should be minimized wherever possible.

[Paul Wunder]

+ 1. I agree with Dave.

Paul

[Chris Padilla]

In your case, I'm not sure it will matter much. If you have time, you could experiment and see or check and see if Bill Pentz's site has some calculations for you. Since you are using 4" to start with, you have already limited yourself quite a bit....

[Bob Borzelleri]

There are 90 degree elbows and there are 90 degree elbows. I think the radius is a pretty big factor in whether or not to use them. I'm using long radius elbows and I don't think they have anywhere near the cfm killing impact of standard 90s.

[Neil Davie]

It does make a great difference on the bends in the dc piping. When I made a cyclone unit for my dc, I also decreased the bends in the unit. At least to my uneducated perceptiion. the suction was nearly twice. The difference was a larger opening from the blower and larger and straighter piping near the unit. 1 hp is rather weak, but for a single unit at a time, and minimal piping run restrictions, it should be ok.
Neil Davie

[Mike Hicks]

not sure if it available in S&D pipe or regular pvc but I know in plastic electrical conduit there are 90 degree elbows and there are 90 degree sweeps. The sweep is not as sharp as the ellbow. I have no idea if this will affect the airflow or not. I do know it makes a big difference when pulling wiring throught them though. The sweeps make pulling wire a lot easier.