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Hydraulic system issue...

Hydraulic system issue...

Hydraulic system issue...

Hi Gents,
We have an ongoing simple winch project and got stuck a bit with hydraulic motor issue.
The system consists of a hydraulic unit (tank+gear pump+el motor), supplying pressure/flow to an axial piston motor.
The winch is equipped with centrifugal brakes (same principle as drum brakes in automotive industry). We use those brakes to lower loads without el. power. This means that the pump in hydraulic unit is not running and the axial piston motor (working in reverse during lowering) is not supplied with pressurized oil.

Any idea how to safely loop the motor to avoid cavitation and keep it lubricated?

RE: Hydraulic system issue...

Give more details and you will have an answer for your situation.

RE: Hydraulic system issue...

You are learning; there is nothing simple about a winch.

Mike Halloran
Pembroke Pines, FL, USA

RE: Hydraulic system issue...

Why not have a check from that will allow oil to be "sucked" from the tank when the low pressure part of the motor drops below atmospheric?

Peter Nachtwey
Delta Computer Systems

RE: Hydraulic system issue...

Pressurize the case of the axial piston motor with a static line from the system reservoir, which then must be mounted above the motor to provide a little gravity head.

Mike Halloran
Pembroke Pines, FL, USA

RE: Hydraulic system issue...

Use cross-port check valve. Let motor output return to itself. When hydraulic flow and pressure is applied to operate the motor the check valve will close and the motor operates normally.


RE: Hydraulic system issue...


Providing positive head of pressure to the motor by a line from the tank is not possible in our case as the tank is places approx. 1 meter below the winch. We were considering this before - tank has to be lower due to manufacturing & operation reasons.


The installation height is around 50 meters. We were planning to loop the motor as you said from A to B ports. In this case, keeping in mind the installation height, we might need to refill the circuit with fresh oil as some of it will go to internal leakage.
In this circuit (without oil refill) will the motor have tendency to cavitate?

RE: Hydraulic system issue...

At the low recirculating pressure leakage will be non-existant. Cavitation will not be a problem.

Do you have a motor spool in the motor directional valve? This would open motor ports to each other and tank so the motor would turn freely with the directional valve centered.


RE: Hydraulic system issue...

Basically what you described is what we have planned to do.
There is a pilot operated directional valve which loops both motor lines while the suction line remains open to tank.

We were sure in the beginning that this solution would work however the motor manufacturer (his representative) was concerned about cavitation in this loop and advised to provide pressurized oil to it or place the tank above motor position.

Attached the loop...

RE: Hydraulic system issue...

The tank is 1 meter below the winch. I presume the motor is directly connected to the winch, therefore at same elevation. Unless your fluid is very viscous, I would not expect a cavitation problem.

Can you show us all of the circuit schematic?


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