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[Millnturn]

That is why you use one size larger QD.

It would be easy enough to test.

Connect a full set of QD to a hose and place in a 5 gal bucket and measure the flow,

Then remove the QD and place the hose in a bucket and measure the flow.

I don't believe you will see a big difference.

That's not a valid test of flow restriction in a hydraulic system with a fixed displacement pump (gear, vane, piston, etc). Setup your test as you described, but add pressure gauges before and after the QD, or better yet, a differential pressure gauge. The effect QD's produce is pressure drop, which increases with flow rate. The flow rate will not change (or, by a negligible amount) until you reach a level of back pressure that exceeds system relief pressure or you slow/stall your prime mover (engine).

Besides a reduction in performance of the system downstream of the QD, another downside is heat. Pressure drop x flow = heat input to system. A hydraulic system, under the right conditions (dumping full flow across relief valve), will produce a tremendous amount of heat into the oil. A system driven by a 20 hp engine has the potential to generate around 15,000 watts of heat under those conditions! Just some food for thought when considering the effects of fluid conductor sizing and pressure drop.

 

[J_J]

My point in using the next higher size QD was about less restriction.

So what you are saying is that hose size/QD size has no effect on GPM's delivered at the end of the hose until relief pressure is met. .

I can understand that as the pump, based on rpm is pumping same volume but at a different pressure until it is slowed down by the end of stroke of a cyl, and the pump now has to force the same volume across the relief valve, therefore testing the engine and pumps ability to produce the GPM at a certain pressure with out stalling.

A lot of people seem to recommend 1/4 in hose for grapple cyl and such thinking it will slow down the action.

The only thing it saves is cost.

 

[Leejohn]

It's about the same as adding a needle valve to slow flow.