Overheating Issue in a Closed Hydraulic System – Sauer SP23 Pump & Hydraulic Motor

[funwithfuel]

No. Charge pressure is for proportional control, cooling and lubricating.

To clarify, i was trying to help you understand that the volume of the charge pump is NOT what you would see coming from case drain. Yes, charge pressure helps purge hot oil so that it can replenish with cooled but it has other functions. It sounds like the intent or meaning was lost in text or translation

 

[Milos 123]

Sure, so from drain line we can have charge pump displacement plus internal lost of piston pump and motor, and if all fine it will be charge pump flow plus maximum 10% of volume of pump and motor ? If I am understanding good

 

[funwithfuel]

Sure, so from drain line we can have charge pump displacement plus internal lost of piston pump and motor, and if all fine it will be charge pump flow plus maximum 10% of volume of pump and motor ? If I am understanding good

Forget charge pump volume. You said your charge pressure was in spec, you said your loop flushing valve was correct. What is your pumps rated volume at maximum displacement at full throttle. You don't want to see more than 10% of that number . I hope this clears things up.

 

[Milos 123]

Okay will measure it

 

[Ben Witter]

I am going to assume this system is the old Sauer series 20 pump and motor. My experience is that charge pressure should be 1.7-2 bar so 13 sounds a bit low. If a Sauer series motor it should have a purge relief in the motor which acts as a secondary charge relief. This is usually set around 0.3 bar lower than the charge relief in the pump and you should see that drop in charge pressure when the pump is stroked. This also serves as a cooling function as it purges oil through the case drain of the motor and through the pump back to the cooler. These older systems did not usually have a loop flushing valve unless installed externally.

If you have overheating you either have inefficiency in your cooling system or you have excessive leakage somewhere in the system. If you have excessive leakage in the rotating groups it will show as significant drop in charge pressure when operating the system.

 

[Milos 123]

That is strange for me because charge pressure is 13 bar and I don't have drop of it. I read in service manual that 13bar is normal for this system. Rebuild pump and motor and will see now how system will work.

 

[Milos 123]

I checked today without operation charge pressure is 18bar, and when start to operate it drops to 8 bar. And hydraulic motor is more hoter during operation.. so probably something wrong with it

 

[HarleyHappy]

Well, generally when you cook your oil, better get ready to rep your pump.

 

[Milos 123]

It is happening after repair.. Can it be that high pressure relief valves on hydraulic motor not good ?

 

[Milos 123]

Problem solved, lot of dirt because of pump first time was broken and after repair it stay in system and demaged rotary plates. Grinded rotary plates and it works like brand new.

 

[Milos 123]

New problem with closed loop system, pressure will not go above 150bar in one and in another direction 50bar, no case drain from hydraulic motor in neutral and charge pressure is normal 18bar. When pressure go to 150bar low side lose pressure to 3bar, all parts put new in hydraulic motor. Flushing relief valve good, can it be wear of flushing piston ? Because when it stop I have lot od oil from drain of hydraulic motor

 

[Vetech63]

You are not right friend,

LMAO.