2-9
PRESSURE TESTS 2.5
The following photos show the various port locations
available on the hydrostatic tandem pump for checking
system pressure.
Completing these pressure test will diagnose any mechan-
ical problem in the hydrostatic system.
Installing a gauge into the high pressure port ‘A’ or ‘B’ ,
will verify the status of the high pressure relief valves.
Checking the pressure at port ‘C’ will give accurate
charge pressure reading.
Checking the pressure at port ‘D’ will verify case drain
pressure.
Measuring the vacuum at the charge pump inlet can help
locate in in the inlet lines and filters. It would be neces-
sary to tee into the charge pump line fitting.
Snubbers are recommended to protect the gauges from
pressure spikes. Frequent gauge calibration is necessary
to insure accuracy.
Gauge Information
A
B
C
D
E
System
Pressure
Port ‘A’
System
Pressure
Port ‘B’
Charge
Pressure
Port
Case
Pressure
Port
Charge
Pump Inlet
Vacuum
10,000 PSI Gauge (690 Bar)
9/16 - 18 O-Ring Fitting
10,000 PSI Gauge (690 Bar)
9/16 - O-Ring Fitting
500 PSI Gauge (34.5 Bar)
Tee Into Charge Filter Outlet Line
500 PSI Gauge (34.5 Bar)
1 - 1/16 - 12 O-Ring Fitting
Vacuum Gauge (30 in. Hg)
Tee Into Charge Pump Inlet
C1794
C1795
C1796
Tandem pump flow can also measure pump performance.
1 Connect a flow meter between the high pressure
ports, one section at a time.
2 Start the engine and increase operating speed
between 1775 ~ 1800 RPM.
3 Restrict the flow to show 2000 PSI (137.8 Bar) over
charge inlet pressure.
Example: Charge pressure = 220 PSI (15.2 Bar) Gauge
pressure reading would need to be 2220 PSI (153 Bar).
4 Minimum flow reading should be 9.5gal / min. (36L /
min).
WARNING
Use caution when dealing with hydraulic fluid
under pressure. Escaping fluid under pressure can
penetrate the skin and cause serious injury.
WARNING
Raise the machine securely from the ground before
performing system checks to prevent sudden move-
ment.
A complete testing kit is available from Thomas, p/n
44365, that contains gauges, hoses and adapters for
Sauer Sundstrand model pumps.
Illustrations are of an internal charge pump model.
Actual model in machine may vary.
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