How to calculate DC pipe diameter

[Eduard Nemirovsky]

Can't find it on net, and I did not see this calculation on Bill Penz site.
I have 2hp 12" impeller Grizzly DC. It is a 1550 CFM max and static pressure 11". Planning to convert to two stage system with Cyclone. I bought this Cyclone long time ago from eBay.
Approximate length of piping two branches with 15-20 feet each.
To create most effective system what diameter PVC should I use - 6" or 4"?
I have TS, J/P combo, BS, router table, CMS and a few other small tools.
Please just point me on site or if you have same system with 4" PVC please tell me if you have enough :D"sucking":D power.

Thank you,
Ed.

[Tom Veatch]

Seems I recall there's a spreadsheet application on Bill's site that lets you do some "what-if" configuration studies. But, the bottom line is, the larger, straighter, and smoother the ductwork the lower the pressure drop and the greater the flow rate.

All other things being the same, 6" will give you better "sucking" power than 4". Mine is all 6" S&D so I can't talk to 4" pipe. 4" could be perfectly acceptable to you, I can't say one way or the other, but I can say that whatever your results with 4", they'll be better with 6". (also more expensive)


Edit: Link to Bill's Static Calculator: http://billpentz.com/woodworking/cyclone/staticcalc.xls

[Chris Padilla]

Typically, 6" is the best way to go....

[Kent A Bathurst]

Yeah - if you're using PVC, you'll want the 6" - too much CFM loss through the 4". If it was metal pipe, then 5" would be a reasonable alternative IMO - but can't get 5" in PVC.

[Tri Hoang]

I think 2 4" pipes are the rough equivalent somewhere between 5" & 6" pipes. I once cost out that it's less expensive to run 2 4" PVC lines than a single 6" (mainly due to cost of connectors). Not pretty/more work but could be an alternative.

[Chris Padilla]

Interesting idea, Tri, but does sound like a pain and I foresee pressure loss depending on how the 2 4"ers are joined together.

The cross-section area of a 4" pipe is about 12.5 sq. in so double that is about 25 sq. in. A 5" pipe is about 20 sq. in. and 6" is about 28 sq. in.

I'd run the 6"ers myself. :)

[Steve Peterson]

Interesting idea, Tri, but does sound like a pain and I foresee pressure loss depending on how the 2 4"ers are joined together.

The cross-section area of a 4" pipe is about 12.5 sq. in so double that is about 25 sq. in. A 5" pipe is about 20 sq. in. and 6" is about 28 sq. in.

I'd run the 6"ers myself. :)

A 4" pipe has a perimeter of 12.56". 2 pipes have a perimeter of 25.13"

A 6" pipe has a perimeter of 18.85".

Therefore, 2 4" pipes will have more sidewall friction than a single 6" pipe.


It is an interesting idea from a cost perspective, but I think 6" pipes will have better airflow and be easier to install.


Steve