TM 5-3895-382-24
System Tests and Adjustments
Pump Efficiency Check
For any pump test at a given rpm, the pump flow at 2100 kPa
(300 psi) will be larger than the pump flow at 6900 kPa
(1000 psi). The difference between the pump flow of the two
operating pressures is the flow loss.
Method of finding flow loss:
Pump flow at 300 psi ................................... 57.5 gpm (liter/min) *
Pump flow at 1000 psi ................................-52.0 gpm (liter/min) *
Flow loss .......................................................... 5.5 gpm (liter/min) *
Flow loss when expressed 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 of
Pump flow @ 300 psi
X 100 =
flow loss
*5.5
or
*57.5
X 100 =
9.5%
If the percent of flow loss is more than 10%, pump
performance is not good enough.
* The numbers in the 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 2100 kPa
(300 psi) and 6900 kPa (1000 psi).
Machine Test
Install a Flow Meter. For Formula I, measure pump flow at
2100 kPa (300 psi) and at 6900 kPa (1000 psi) with the engine
at high idle rpm.
Formula I:
gpm @ 300 psi -gpm @ 1000 psi
Percent of
gpm @ 100 psi
X 100=
flow loss
Bench Test
If the test bench can be run at 6900 kPa (1000 psi) and at full
pump rpm, find the percent of flow loss using Formula I.
If the test bench cannot be run at 6900 kPa (1000 psi) and at
full pump rpm, run the pump shaft at 1000 rpm. Measure the
pump flow at 2100 kPa (300 psi) and at 6900 kPa (1000 psi).
Use these values in the top part of Formula II. For the bottom
part of the formula, run the pump shaft at 2000 rpm. Measure
the pump flow at 2100 kPa (300 psi).
Formula II:
gpm @ 300 psi -gpm @ 1000 psi
Percent of
gpm @ 300 psi @ 2000 rpm
X 100 =
flow loss
Travel Speed Test
NOTE:
The machine must be in high speed range for this
test.
The oil in the system must be SAE 10W hydraulic oil. The oil
temperature must be at 38°C (100°F) to get correct results. All
speed tests are made with the engine rpm at maximum rpm.
Time the machine in forward and reverse through a
30.5 m (100 ft) timing trap. The vibration system must be off.
NOTE: The machine must be at top speed through the
entire timing trap.
Travel speeds that are the same as those that follow are an
indication that the circuit operation is normal. The relief valves
for both charge pump and main line closed circuit must be
tested to be sure that the opening pressure of each is correct.
Maximum travel time ....................................................10 seconds
Minimum travel speed:
Forward motion .......................................11 km/h (600 ft/min)
Reverse motion ......................................11 km/h (600 ft/min)
Times for forward and reverse through the 30.5 m
(100 ft) timing trap must match within one second.
If the travel speed is not correct, check the following:
1.
Pump efficiency.
2.
Setting of the charge system relief valve.
3.
Setting of the main line closed circuit relief valves.
4.
Make sure the machine is in high speed range.
5.
Make sure the linkage rod between the drum and axle
pumps is adjusted correctly.
6.
Check
axle
propel
motor
for
correct
minimum
displacement adjustment.
11-37
