hydraulic flow capacity

[cityevader]

I currently have a 9hp 16gpm splitter with 5"cylinder, and I've got an extra 5x24" cylinder that I may use for a homebuilt splitter with a bigger engine/pump....something like 13-ish HP (or more) and 22gpm.
The cylinder has 1/2" npt ports. The valve I've got has 1/2"npt working ports and is rated for 25gpm.

My question is, can 1/2" really support 22gpm? I seem to remember someone here adamantly saying it couldn't, or that the flow would be so fast it would readily overheat... but then saw the flow rating of the valve with 1/2" and 25gpm. Or would it be better take cylinder to machine shop and have old ports cut off and 3/4" ports welded on and use 3/4" for everything?

 

[Patrick62]

okay...

The 1/2 fittings are capable, and a 1/2 hose isn't. As you pointed out the valve is rated to 25 GPM and has 1/2" ports. I am running a 16 GPM pump thru 1/2 hose and it really isn't the right thing to do.

I think that a 3/4 hose can be made with 1/2" NP fittings, go for it.

-Pat

 

[cityevader]

Forgot to mention that the hose would be right about 2 ft long, regardless of diameter.

 

[cityevader]

Does anybody have a link with a chart or something that shows max flow capacity at certain diameters at certain lengths?

Or even a generic rule of thumb for max flow with 1/2" and 3/4"?

 

[Labman]

Since the calculations for flow are complex, a lot of pipe sizing is done by guess and by garsh. You might try looking at commercial units. If all else fails, you need one short little hose. Likely as suggested, one 3/4 hose with 1/2 fittings, won't cost that much more.

I can say a 3/4 hose will carry 4-5 times as much oil at the same back pressure as a 1/2.

 

[brisawyer]

Gates flow chart
http://www.gates.com/downloads/download_common.cfm?file=NomographicChart.pdf&folder=brochure

 

[cityevader]

Can I assume that a 3/4" hose with a 1/2" end fitting is preferable to a 1/2" hose?

Is it more a matter of friction against the inside walls being more important than diameter at the smallest point? I.E. one fitting dropping in diameter over a length of its one inch is preferable to two feet of that same reduced diameter?

 

[Labman]

Yes. To do a flow calculation, you have to solve an equation for each section. There are some rules of thumb such as a valve or elbow is equal to the length of so many diameters. For laminar flow, back pressure or flow varies as the fourth power of the diameter. A short section of half inch has much higher pressure drop than a longer section of 3/4.