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Sizing Hydraulic Flow Control Valves

Started by Rougespear, January 10, 2017, 11:08:04 PM

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Rougespear

Anyone know much about sizing hydraulic adjustable flow controls?  I see flow controls capable of between 8 and 30 GPM.  My system is 3-4gpm.  Does it matter if I use a flow control rated at 16gpm, or should I choose one closer to my system's flow rate?  I ask because I am unsure if the flow control's adjustable flow is proportional to it's orifice diameter or simply the incoming flow to the valve.  My thinking is that is I use a large flow control, I will have less of an adjustable range, but I'm not sure!  Thoughts?
Custom built Cook's-style hydraulic bandmill.

redprospector

The rating of the valve is for maximum flow, you can shut the flow completely off. So you won't loose anything (other than a few bucks) using an oversized flow control.
1996 Timber King B-20 with 14' extension, Morgan Mini Scragg Mill, Fastline Band Scragg Mill (project), 1973 JD 440-b skidder, 2008 Bobcat T-320 with buckets, grapple, auger, Tushogg mulching head, etc., 2006 Fecon FTX-90L with Bull Hog 74SS head, 1994 Vermeer 1250 BC Chipper. A bunch of chainsaws.

ozarkgem

Not sure of your application but a flow control restricts flow in one direction only and a needle valve restricts flow in both directions.
Mighty Mite Band Mill, Case Backhoe, 763 Bobcat, Ford 3400 w/FEL , 1962 Ford 4000, Int dump truck, Clark forklift, lots of trailers. Stihl 046 Magnum, 029 Stihl. complete machine shop to keep everything going.

Kbeitz

With the bigger one you will probably need to reduce the connection
fittings.
Collector and builder of many things.
Love machine shop work
and Wood work shop work
And now a saw mill work

Rougespear

Thanks guys.  I'm controlling the feed speed of my mill.  I understand flow is controlled only in one direction. 

I'm concerned about the fine-tune adjustability of the flow.  Most descriptions of one-way adjustable flow control valves suggest "flow is proportional to orifice diameter", and I would assume the orifice diameter of a given valve increases as the GPM rating increases.  So for example given my fixed flow of 4 gpm, an 8 gpm flow control set at 50% open would pass 4 gpm, and a flow control with 16 gpm set at 25% would pass 4 gpm.  So what I'm thinking is I will have less of a range of adjustability with the 16 gpm (0-25%) vs the 8 gpm (0-50%).  And less adjustability would mean less control over the carriage feed speed.

Am I just babbling or making sense?  I'm no hydraulics expert by any stretch!!
Custom built Cook's-style hydraulic bandmill.

bandmiller2

I would use the same size as your valve and hoses. You want needle control for feed and full flow for gig back. I used a 1/2" valve for my feed, or what ever is close for metric. Frank C.
A man armed with common sense is packing a big piece

Brucer

Flow control valves are most accurate at the high end of their range.

Avoid the pressure-compensated type unless you expect to see a wide variation in pressure while you are sawing.
Bruce    LT40HDG28 bandsaw
"Complex problems have simple, easy to understand wrong answers."

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