TM 5-3825-226-24
STEERING HYDRAULIC SYSTEM
PUMP EFFICIENCY CHECK
For any pump test at a given rpm, the pump flow
(gpm) at 100 psi (7.0 kg/cm2) (690 kPa) will be larger
than the pump flow (gpm) at 1000 psi (70.0 kg/cm2)
(6900 kPa).
The difference between the pump flow of two operating
pressures is the flow loss.
Method of finding flow loss...
Pump flow at 100 psi ................
57.5 gpm (litre/min)*
Pump flow at 1000 psi ..............
-52.0 gpm (litre/min)*
Flow loss ..................................
5.5 gpm (litre/min)*
Flow loss when given as a percent of pump flow is
used as a measure of pump performance.
Example of finding percent of flow loss...
gpm flow loss
Percent
x 100 =
of flow
Pump flow @ 100 psi
loss
* 5.5
or
x100+=
9.5%
* 5.5
If the percent of flow loss is more than 10%, pump
performance is not good enough.
* Numbers in examples are for illustration and are not
values for any specific pump or pump condition. See
SPECIFICATIONS for pump flow of a new pump at
100 psi and 1000 psi.
Test On The Machine
Install a 9S2000 Flow Meter. Measure pump flow at
100 psi (7.0 kg/cm2) (690 kPa) and at 1000 psi (70.0
kg/cm2) (6900 kPa) with engine at 2000 rpm.
NOTE: See Tee Test Tooling Chart Form No.
REG00910.
Formula I:
gpm @ 100 psi - gpm @ 1000 psi
Percent
x 100 =
of flow
gpm @ 100 psi
loss
Test On The Bench
If the test bench can not be run at 1000 psi at a high
rpm, do the first part of the test with the pump shaft
rotation at 1000 rpm. Measure pump flow at 100 psi
(7.0 kg/cm2) (690 kPa) and at 1000 psi (70.0 kg/cm2)
(6900 kPa). Then to measure the pump flow for the last
part of the test, see SPECIFICATIONS for: Pump rpm
at 100 psi with the engine at 2000 rpm.
Formula II:
gpm @ 100 psi - gpm @ 1000 psi
Percent
x 100 =
of flow
gpm @ 100 psi @ 2000 rpm
loss
STEERING CONTROL VALVE
The values shown in the SPECIFICATIONS are for
hydraulic oil that is 150°F (65°C). Run the engine and
operate
the
hydraulic
system
to
increase
the
temperature of the hydraulic oil. Stop the engine and
loosen the filler cap to let the air out of the supply tank
before a test hose and gauge are installed or removed.
Relief Valve for the Steering Circuit
The steering control valve is located under the
operator's station.
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