Can you reduce gpm this way?

[20 20]

I came across a 540 rpm hydraulic pto gear pump that had been reduced at the inlet from 1 1/2" to1" and reduced at the outlet from 1 1/2" to 3/4" and I guess they were trying to reduce the gpm.
My question is can you reduce the gpm this way without causing some sort of
problem?.

Reducing this way, from what I was told{hydraulic mechanic}, will cause damage.

 

[Stonehaller]

The particular model of compensated flow control picked out by J_J has an internal relief set at 1500 psi. You should look for a model without the internal relief or at least verify that the internal relief can be set to 2500 psi or greater.

 

[J_J]

The particular model of compensated flow control picked out by J_J has an internal relief set at 1500 psi. You should look for a model without the internal relief or at least verify that the internal relief can be set to 2500 psi or greater.

The valve that I posted is adjustable, it come from the factory set to 1500 psi. I use one of these valves for my PTO control implements, and you select whatever speed you want for the hyd motor. What isn't used goes back to tank.

 

[J_J]

Reducing this way, from what I was told{hydraulic mechanic}, will cause damage.

Not really. Although the hoses from the large PTO pumps, seem large, somewhere down line, whether it be the control valve, or the hyd motor, you will have to reduce the fittings to match the valve or motor. There is no reason to reduce the input size, as the distance is usually short. The hose size for a flow velocity of 30 GPM at 20 FPS, is around 3/4 in to 7/8 in.

 

[Egon]

With a PD pump the output will remain constant unless there is insufficient fluid getting to the pump suction. You will then get a negative pressure head and cavitation in the pump.

 

[desert trader]

Thank you all for your input it will help me greatly.

 

[sizzami]

what is the difference between bushing from 1.5 to 1.25 at the pump and installing a restrictor valve? except that the passage in the valve is probably no larger than .125? I see it in log splitter valves every day , haldex 22 gpm pumps are 1.00 outlet and prince ls 3000 valves are .75 0n the inlet side.
is this only ok because they are two stage JJ?

 

[J_J]

If you restrict any more than what the input and the output fittings are, you will have to accept the difference generated by such action. Two stage operation in a pump dose not have anything to do with reducing the pressure at the fittings or ports.. A two stage pump simply switches to a different displacement part of the pump when the pressure equals the designed pressure cut in and cut out. Anything that restricts flow will cause a change in the flow of the fluid. At a certain rpm, a pump will try and pump a certain amount of fluid, based on the cu in of the pump. If you restrict the flow from that pump, the pressure will increase, similar to the technique used by pressure washers to get that 3000 psi. They are pumping fluid through a 3/8 in hose of say, 4 GPM Then the fluid goes through a tip with a reduced outlet of about 1/32 in or smaller. A relief valve is in the system to keep from destroying the pump or other components.

 

[kennyd]

what is the difference between bushing from 1.5 to 1.25 at the pump and installing a restrictor valve? except that the passage in the valve is probably no larger than .125? I see it in log splitter valves every day , haldex 22 gpm pumps are 1.00 outlet and prince ls 3000 valves are .75 0n the inlet side.
is this only ok because they are two stage JJ?

Restrictors are usually placed on the work ports where there is not constant flow like the IN/OUT ports.

 

[AKKAMAAN]

I came across a 540 rpm hydraulic pto gear pump that had been reduced at the inlet from 1 1/2" to1" and reduced at the outlet from 1 1/2" to 3/4" and I guess they were trying to reduce the gpm.
My question is can you reduce the gpm this way without causing some sort of
problem?

They did not try to reduce Flow or GPM. Flow can not be "reduced" by restriction unless there is a flow by pass available.....exception is the "suction" or inlet side. But that is a "NO NO" method to use, because of risk for caviation.
So by reducing port sizes, the only reason that somewhat could make sense is that they ran the pump on a lower maximum rpm than rated, so the flow actually was lower than the rated flow...other than that, the reason are usually to reduce costs on fittings, tubing and hoses.....which will come back as losses on power economy and problems overheating and/or cavitation....

I'm reposting this because if this won't work I'm not going to use this pump.
Your input will be greatly appreciated.

Determine the displacement size, cui per rev, of the pump, calculate the gpm flow, use a Nomogram to check what recommended hose sizes you will need.

It is all that simple!!