Load sense pump setup questions

[abasinger]

Hello,

I have a few questions regarding a LS pump setup. Please view the attached jpg for description and specs of the pump that I have.

I am thinking of using the pump in a log splitter build. It has a margin, and cutoff spool set to 305 and 4640, respectively. I am familiar with piston pump systems and operation, but usually when I deal with them, I am adjusting them to certain specifications. I would like a little deeper technical guidance on the characteristics of this style of pump.

My first question is power requirements. When are the peak power requirements of a pump like this? When it is at full flow? When it is at high pressure cutoff? How many horsepower should I expect this pump to require at the most?

My second issue: Adjustment of the cutoff spool is pretty self explanatory. The margin spool, however, is a little more foggy to me. Margin pressure as I know it, is difference between the output pressure, and your work port (signal) pressure. What effect would I expect to see if margin pressure was adjusted in a log splitter application? Does it affect the maximum flow output? Which spool is going to affect horsepower draw more? ( I assume the cutoff will)

My third question: The pump spec sheet shows 1000 rpm can yield 84 GPM. If I plan on running the pump at 500-600 rpm, can I expect a linear change in the output flow, I.E. 45GPM?

I will be using a roughly 6" bore cylinder with approximately 4' stroke, and a LS closed center valve. If I am thinking correctly, that should be about 70 tons of pressure at the rod eye?

Thanks in advance for any input.

Anthony

 

[HPost]

I can't be bothered to change all of the imperial units to SI...so here is the basic answer to your questions.

The peak power, otherwise known as corner power is the point where the pump is at full displacement and the pressure is just under the pressure cut off point.

The margin should be set to match the flow requirement across the spool. If the pressure drop across the spool is too high, the pump will never get to max flow. If the pressure drop is too low, relative to the margin pressure, then the pump will consume more power than it needs to. It is the margin compensator that will burn more oil if it is set incorrectly. If the pressure reaches the setting of pressure cut, the pump will go to minimum displacement and will consume less power. That is always governed by the load on the machine.

The pump displacement is given in cubic inches / rev. Convert gpm to cubic inches and divide it by 1000 to get the displacement. Then multiply that by the rev you want to get the flow.

Cylinder force is pressure x area - 70 tons of force, not pressure.

 

[hydtools]

Hydraulic hp = psi x gpm / 1714
Gal x 231 = cu.in.
Ted

 

[abasinger]

Thanks for the replies, I have answered my mathematical questions by them.

Am I understanding correctly that I can adjust the pump to a certain corner horsepower by adjusting margin? I could size the valve appropriately after figuring the margin/power requirements. The horsepower choices available are the limiting factors in this case.

 

[HPost]

The pressure cut off compensator sets the corner power. The margin compensator matches the pump power to the system demand.