Sundstrand Sauer Danfoss Series 15 Circuit Diagram Description

In this diagram it talks about the suction flow, charge pressure, case pressure and atmosphere on a fixed motor.

Bypass Valve
This can be used on all applications except the “U” unit. The fixed displacement motor fluid can moved in short distances without the using the prime mover. If you want to use this in a “U” unit, you would need to do the following: add a screw in type valve (when it is unscrewed lets both sides of the pump/motor circuit to free wheel.
It needs to be closed while you operate it to achieve its highest performance so it will not allow heat build.
A “U” unit uses a button you have to push in the charge check valve in order for the valve to be open.

Inlet Filter

It only lets in fluid that has not been contaminated by using a 25 micron filter that goes in the charge pump line.

Reservoir

The bottom of the reservoir has to be always have fluid in it. This comes from the charge pump line.
Here is a total minimum amount: In gallons 5/8 of the charge pump flow in gallons per minute with a minimum fluid capacity equal to one half the charge pump flow.
The return flow port needs to be a close to the inlet port so gives highest level of dwell time for the fluid in the reservoir. And the fluid has to discharge below the fluid level.
If you use an open reservoir, the air breather has to be free of contamination in order to work properly.

Heat Exchanger
The transmission shouldn’t rise above 200 degrees as long as it is running operation. If you wish to run it like that you will need to add a Heat Exchanger in the line bringing back the fluid to the reservoir. A normal heat exchanger should be able to handle 25% of the input horsepower to the transmission.

If you have further questions on this topic, please let us know.
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