Which hydraulic valve to use?

Question

I am putting together a hydraulic system in which there will be three motors and one cylinder. One of the motors will need to be reversable and the cylinder will too. The system will be powered by a variable volume piston pump which will be putting out about 30gpm. I have heard that variable volume piston pumps need to have closed center valves. Is that true? As I am on a very restrictive budget I was thinking of getting two manifolds that together would handle 30gpm instead of getting one manifold that can handle 30gpm but is much more expensive than two 20 gpm manifolds. Any ideas? Thanks Rick

Jon Elson · Accepted Answer

Right. The variable displacement pumps will deliver whatever volume is needed to maintain constant pressure, up to their maximum displacement. If you have a power-beyond valve, it will dump all the volume to the tank when no valve is supplying a load, and will likely overheat the pump. The pump is designed to run with a blocked output, and will draw very little power from the power source in this condition. These pumps usually have a small cooling pump that circulates fluid to cool the pump when it is not delivering volume.

As I am on a very restrictive budget I

As long as no single load needs more than 20 GPM, then that should work fine.

Jon

Rick Wilmath · Answer

I am putting together a hydraulic system in which there will be three motors and one cylinder. One of the motors will need to be reversable and the cylinder will too. The system will be powered by a variable volume piston pump which will be putting out about 30gpm. I have heard that variable volume piston pumps need to have closed center valves. Is that true? As I am on a very restrictive budget I was thinking of getting two manifolds that together would handle 30gpm instead of getting one manifold that can handle 30gpm but is much more expensive than two 20 gpm manifolds. Any ideas? Thanks Rick

Ned Simmons · Answer

Assuming you have a pressure compensated pump. Variable volume pumps also come in flow compensated (constant flow) and power compensated (constant power) flavors.Ned Simmons

Which hydraulic valve to use?

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