Component Inspection And Adjustment - Sauer Danfoss 51 Series Service Manual

Bent Axis Variable Displacement Motors

Component Inspection and Adjustment

WARNING
The following procedures may require the ve-
hicle/machine to be disabled (wheels raised off
the ground, work function disconnected, etc.)
while performing the adjustments to prevent
injury to the technician and bystanders.
Charge Pressure Relief Valve Adjustment
An appropriate combination of pump and motor charge
pressure settings should be maintained to insure the
proper function of the loop flushing circuit. Correct
charge pressure must be maintained under all
conditions of operation to maintain pump control
performance in closed loop systems.
To measure motor charge pressure, install a 0 to 60
bar or 0 to 500 psi pressure gauge in the motor charge
pressure gauge port. Install a gauge to measure case
pressure. Operate the system with the prime mover
at normal operating speed and the pump at half
stroke (forward or reverse) when measuring motor
charge pressure.
In most applications, the motor charge relief valve is
set 2 to 4 bar (29 to 58 psi) below the setting of the
pump charge relief valve (measured with the pump in
its "neutral" or zero-angle position). This setting as-
sumes a reservoir temperature of 50° C (122° F), and
is referenced to case pressure.
Series 51 motors are equipped with an external screw
adjustable charge pressure relief valve. To adjust the
charge pressure, loosen the lock nut (with a 1-1/16"
hex wrench) and turn the adjustment plug with a large
screwdriver. Clockwise rotation of the plug increases
the setting, and counter-clockwise rotation decreases
the setting (at a rate of approximately 3.4 bar [50 psi]
per turn). The lock nut should be torqued to 52 Nm (38
ft•lbsf).
Once the desired charge pressure setting is achieved,
remove the gauges and reinstall the port plugs.
30 - 5
Fig. 30-6 - Adjusting Charge Pressure
Relief Valve
Fig. 30-7 - Tighten Charge Pressure Relief
Valve Lock Nut
Series 51
51000042
51000043
27