Textron JACOBSEN GP400, Technical/Repair Manual

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HYDRAULICS
4252490-Rev A 6-31
6
Instrument Test Procedures
Instrument Test Overview
The following tests are specifically designed to approach
hydraulic testing on a system level. Each component
within the system represents a portion of the total system
leakage. An internal leakage percentage for each
component will be calculated and recorded, enabling the
technician to view the system performance issue more
completely. The test results will help the technician to
determine which repairs will best remedy the
performance issue experienced by the machine operator.
The internal leakage percentage ranges are as follows:
0–10% = Good
11–20% = Marginal
21% and Beyond = Bad
Example: Cutting Unit System Performance
Complaint
The machine operator reports that the mower is not
cutting correctly.
Troubleshooting must first be performed to rule out a
cutting unit adjustment issue. Once the issue is known to
be component related, the entire cutting unit system is
tested as outlined. The calculated system leakage is
28%, a result that requires the testing of individual
components. This result can also be interpreted as a
system that is 72% efficient.
The remaining components in question are as follows:
gear pump, reel valve unit, right reel motor, left reel
motor, and center reel motor. Following the procedures
as outlined, test each individual component, then
calculate and record leakage percentages.
The results from this test reveal leakage of 5% in the
gear pump, 5.3% in the reel valve unit, 20% in the right
reel motor, 5.6% in the left reel motor, and 4.4% in the
center reel motor. Although all the components lend to
the overall circuit leakage, only the right reel motor, which
is at the extreme end of the marginal range, would be
considered for repair/replacement.
Formulas:
Cutting Units Circuit Test
No Load Flow – Loaded Flow / No Load Flow x 100 =
Leak Percentage
Reel Valve Unit and Reel Motor
Loaded Flow from previous component – Loaded Flow
from current component / Loaded Flow from previous
component x 100 = Leak Percentage
Calculations:
Cutting Units Circuit Test
No Load Flow = 10 gpm
Loaded Flow = 7.2 gpm
10 – 7.2 / 10 x 100 = Total Circuit Leakage 28%
Gear Pump Test
No Load Flow = 10 gpm
Loaded Flow = 9.5 gpm
10 – 9.5 / 10 x 100 = Front Cutting Unit Pump Leakage
5%
Reel Valve Unit Test
Loaded Flow from front cutting units pump test = 9.5 gpm
Loaded Flow from front reel valve unit test = 9 gpm
9.5 – 9 / 9.5 x 100 = Reel Valve Unit Leakage 5.3%
Right Reel Motor Test
Loaded Flow from reel valve unit test = 9 gpm
Loaded Flow from right reel motor test = 7.2 gpm
9 – 7.2 / 9 x 100 = Right Reel Motor Leakage 20%
Left Reel Motor Test
Loaded Flow from right reel motor test = 7.2 gpm
Loaded Flow from left reel motor test = 6.8 gpm
7.2 – 6.8 / 7.2 x 100 = Left Reel Motor Leakage 5.6%
Center Reel Motor Test
Loaded Flow from left reel motor test = 6.8 gpm
Loaded Flow from center reel motor test =
6.5 gpm
6.8 – 6.5 / 6.8 x 100 = Center Reel Motor Leakage 4.4%