Testing and Adjusting the Charge Pressure
Introduction
This test is designed to determine if the charge pressure is set to the correct pressure setting.
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Sudden movement of the machine or release of oil under pressure can cause serious injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system. |
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| NOTICE |
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Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "AVSpare Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on AVSpare products. Dispose of all fluids according to local regulations and mandates. |
Required Tools
Hydraulic test procedures may be performed using either one of the following test equipment:
- Digital Pressure Indicator
- Standard tooling
Digital Pressure Indicator
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| Illustration 1 | g00929122 |
Table 1 provides a list of the required tools if the 198-4240 Digital Pressure Indicator is used to perform the following test procedure.
| Required Tools Digital Pressure Indicator |
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|---|---|---|---|---|
| Tool | Item | Part Number | Description | Qty |
| A | A1 | 198-4234 | Digital Pressure Indicator | 1 |
| A2 | 198-4238 | Pressure Sensor 0 - 34500 kPa (0 - 5000 psi) |
1 | |
Standard Tooling
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| Illustration 2 | g00929125 |
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| Illustration 3 | g00929126 |
Table 2 provides a list of the required tools if standard tooling is used to perform the following test procedure.
| Required Tools (Standard Tooling) | ||||
|---|---|---|---|---|
| Tool | Item | Part Number | Description | Qty |
| B | B1 | 177-7860 | Hose As | 1 |
| 6V-4143 | Coupler | 2 | ||
| B2 | 8T-0855 | Pressure Gauge 0 to 4000 kPa (0 to 580 psi) |
1 | |
| 6V-3989 | Fitting | 1 | ||
| C | - | 4C-6500 | Digital Thermometer | 1 |
Test Procedure
The 198-4240 Digital Pressure Indicator was used in the following test.
Note: A charge relief valve is located in both the propel pumps. The charge relief valve in the drum propel pump should be the controlling relief valve (lower pressure setting). If the setting of the charge relief valve for the drum propel pump does not change, the charge relief valve for the axle propel pump may be set too low.
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| Illustration 4 | g00948757 |
Propel pumps (1) Charge pressure test port (2) Charge relief valve | |
- Make sure that the parking brake is applied. Make sure that the propel control lever is in NEUTRAL position.
- Connect Tool (A2) to pressure test port (1) next to the propel charge filter.
- Start the machine and run the engine at 2310±50 RPM. Check the hydraulic temperature with Tool (C) until the hydraulic oil temperature reaches 38°C (100°F).
- Check the pressure at test port (1). The setting for the charge relief valve should be 2300 ± 100 kPa (335 ± 15 psi).
- The charge relief valve must be adjusted if the pressure setting is incorrect. In order to adjust the charge pressure, stop the engine and remove the charge relief valve (2) from the axle propel pump.
Note: If you need to test the charge pressure of the axle propel pump, add two shims to the charge relief valve of the drum propel pump. The shims will increase the pressure of the drum propel pump above 2951 ± 152 kPa (428 ± 22 psi) so that you can check the pressure of the axle propel pump.
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| Illustration 5 | g00478414 |
Charge Relief Valve (3) Shim | |
Adjusting Procedure
- If the charge pressure is too low, add shims (3) to the charge relief valve. If the charge pressure is too high, remove shims (3) from the charge relief valve.
Note: When the shims are added to the charge relief valve, a 1 mm (0.04 inch) shim is the equivalent of raising the charge pressure by 390 kPa (56.5 psi). When the shims are removed from the charge relief valve, a 1 mm (0.04 inch) shim is equal to reducing the charge pressure by 390 kPa (56.5 psi).
- Install the charge relief valve.
- Perform this test again in order to verify the charge pressure after the adjustments have been made.
- Remove the pressure gauge from the test port.