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Author Topic: Sizing Hydraulic Flow Control Valves  (Read 650 times)

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Offline Rougespear

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Sizing Hydraulic Flow Control Valves
« on: January 10, 2017, 11:08:04 pm »
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?
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Offline redprospector

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Re: Sizing Hydraulic Flow Control Valves
« Reply #1 on: January 11, 2017, 02:19:23 am »
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.
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Offline ozarkgem

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Re: Sizing Hydraulic Flow Control Valves
« Reply #2 on: January 11, 2017, 05:38:46 am »
Not sure of your application but a flow control restricts flow in one direction only and a needle valve restricts flow in both directions.
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Offline Kbeitz

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Re: Sizing Hydraulic Flow Control Valves
« Reply #3 on: January 11, 2017, 08:35:30 am »
With the bigger one you will probably need to reduce the connection
fittings.
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Offline Rougespear

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Re: Sizing Hydraulic Flow Control Valves
« Reply #4 on: January 11, 2017, 10:19:31 am »
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!!
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Offline bandmiller2

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Re: Sizing Hydraulic Flow Control Valves
« Reply #5 on: January 11, 2017, 03:42:13 pm »
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.
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Offline Brucer

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Re: Sizing Hydraulic Flow Control Valves
« Reply #6 on: January 13, 2017, 01:25:03 am »
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 with two 6' extensions.
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