Hydraulic Valve selection?

[Spell]

I have a Kubota 2320 and want to put rear Hydraulic remotes on. Hydraulic pump flow is approx 4.7gpm. I am looking at a 11gpm valve and I want to know if this high flow rate will affect how the valve works when trying to move the cylinders slowly?

 

[J_J]

With a large valve flow rate of a 11 GPM, with the lever about half, you will have applied the full flow to the cyl.

You will have slower and a more finesse action with a valve that matches the flow rate.

 

[Spell]

Thanks J_J. That's what I thought would happen. Now I have to find a 5gpm two or three spool valve with bsp fittings

 

[CHDinCT]

I'm just about to embark on the same project so I'm curious about JJ's logic here. I would think the speed of the cylinder would relate directly to the amount of GPM delivered by the pump and not the valve. Though the valve can allow as much as 11 GPM to flow through it, the pump is only delivering 4.7. I thought as long as the valve GPM exceeds the pump GPM you're good to go. By the way, I ordered and 8 GPM for my BX, which delivers something like 3.6 GPM to implements (vs power steering).

 

[J_J]

Yes, you could reduce engine rpm for reduced flow.

If you use a larger valve , by the time you open the valve to half, you will be using the full flow of the pump, and any more lever action will not add anything.

Valves with higher flow rates cost more also.

 

[J_J]

I'm just about to embark on the same project so I'm curious about JJ's logic here. I would think the speed of the cylinder would relate directly to the amount of GPM delivered by the pump and not the valve. Though the valve can allow as much as 11 GPM to flow through it, the pump is only delivering 4.7. I thought as long as the valve GPM exceeds the pump GPM you're good to go. By the way, I ordered and 8 GPM for my BX, which delivers something like 3.6 GPM to implements (vs power steering).

With your lever at half, you are allowing the pumps full flow to go to the cyl.

The cyl would be moving as fast as it could go. Lower the volume, = increase time for work.

You could have used a smaller valve if they made them.

Yes, your valve will allow the pump, and cyl to work at max potential at half lever action.

 

[jasong123]

With an open centre valve as you move the spool across you close down the open centre and open the connection to your cylinder. If there is less flow coming from the pump then you would have to close off the centre even more to generate enough pressure to start flowing into the cylinder (assuming the cylinder has some load), this means it would feel like you have to stoke the spool a long way before you get any flow. You would however, get all the flow when fully stroked.

An example of this is when you have a moderately loaded front end loader and move the spool accross until the flow starts. check the position of the lever at idle and at 2000rpm and at lower RPM you needed to stroke the spool further to get the service to start flowing.

With a closed centre, the point at which the oil starts flowing does not move around (generally) and therefore you would have the same flow curve but would max out the pump early.

I would try to match the valve size closely with the pump flow at max rpm to deliver the best controlability.