Question about Danfoss Sundstrand-sauer-danfoss Sundstrand Hydraulic Pump

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Pressure setting of series 90 pumps

Hi, this is chandrakant from india. i am working for Schlumberger asia services ltd. as mechanic. we are user of sauer sundstrand pump . we have a problem with one series 90 pump, we want to set a pressure rating we are getting now 2000 psi and we wnt to increase it up to 3000 psi. is it possible ? pls guide me.

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Well, first you have to remember that your charge pressure is about 10% of the setting pressure, I mean if your main pressure is 2000 psi, then your charge pressure must be set at not lower then 200 psi in idle (650 rpm).
To increase pressure, take a 15/16 wrench and 5/16 allen wrench, on top of pump, at the side of charge filter block, you will see two multifunctional valves, one for port M1 and one for port M2 ( ports "A" and "B")
Remove hoses from such ports underneath the pump and plug them, then with engine in idle, with wrench 15/16 brake lose the top set screw nut of the multifunctional valve, slowly turn set screw with 5/16 allen wrench 1/2 a turn cw, this must increase your pressure about 500 psi, so from 2000 to 2500 psi, do this with both multifunctional valves.
Double check your pressure by stroking manually these pump.
You should increase your charge pressure also, remember 10% of your desired pressure.
main pressure 3000 psi
Charge pressure 300 psi
If you look your pump from behind, at your right hand,little above next to port M2, you will find another set screw with a big nut.
With a 1 1/4 wrench or 1 1//8 wrench, sorry cant remember the right size at this moment, brake lose such nut and turn 1/2 way in set scrwe with wrench 1/2 of an inch. this will increase your charge pressure

Posted on Apr 22, 2009

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Yes 90 series pumps will run pretty close to 6000 psi. there are cross port reliefs built into the endcap of the pump and usually a POR valve as well. so the POR should be set at 3000, the cross ports in the pump should be set higher than this. There may also be a "transmission block" which is a seperate block with hot oil shuttle and cross port reliefs. Make sure these reliefs are also set higher than the POR valve in the pump. There may also be cross port reliefs in the motor. These too must be set higher than the POR valve in the pump. If you system overheats after increasing the pressure setting of the POR valve, you are probably loosing oil across one of the cross port relief valves.
Please visit for more information. I** If am electric motor is being used to drive this pump, be sure you have sufficient horse power for this increased load. **

Posted on Mar 15, 2009


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