| Required Tools | ||
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| Part Number | Description | Qty |
| 175-5507 | Nitrogen Charging Group | 1 |
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Dry nitrogen is the only gas approved for use in the accumulators. The charging of oxygen gas in an accumulator will cause an explosion. An explosion can be eliminated by using nitrogen gas cylinders with standard CGA (Compressed Gas Association, Inc.) No. 580 connectors. When nitrogen gas is ordered, make sure to order the cylinders with CGA No. 580 connectors. Do not rely on color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders. In any application, never use an adapter to connect your nitrogen charging group to a valve outlet used on both nitrogen, oxygen, or other gas cylinders. BE SURE YOU USE DRY NITROGEN (99.8% purity). |
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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, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products. Dispose of all fluids according to local regulations and mandates. |
Note: Before you perform this procedure, release the pressure from the steering system and from the braking system. Also, make sure that the steering frame lock is installed. For the correct procedure for machine preparation, refer to Testing and Adjusting, "System Pressure - Release".
To ensure that the pressure of the nitrogen charge is correct, the accumulator piston must be on the bottom of the cylinder.
Gas pressure varies with temperature. Check the temperature of the air around the accumulator. To check the amount of charge in an accumulator, the accumulator must be at the same temperature as the surrounding air. Use the following table to determine the correct amount of gas pressure.
| Charging Pressure and Temperature Relationship for a Typical |
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| (1) | Nominal allowable tolerance equals ± 70 kPa (10 psi). |
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| Illustration 1 | g00107133 |
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(1) Nipple
(2) Coupling assembly (3) Pressure gauge (4) Hose assembly (5) Coupling assembly (6) Nipple (7) Valve (8) Pressure gauge (9) Regulator assembly (10) Pressure regulating screw (11) Chuck for the nitrogen cylinder valve (12) Valve handle (13) Chuck (14) Hose assembly | |
Check the Nitrogen Charge in the Accumulator
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| Illustration 2 | g06221927 |
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Brake Accumulator (15) Bolts (16) Cover (17) Cap for the nitrogen charging valve (18) Nitrogen charging valve (19) Accumulator | |
- Remove two bolts (15) and cover (16) from accumulator (19). Remove cap (17) from nitrogen charging valve (18).
- Use pressure gauge (8) to check the amount of nitrogen charge in the accumulator.
- Install chuck (13) on nitrogen charging valve (18).
- Make sure that valve (7) is closed. Install valve handle (12) onto chuck (13). Rotate valve handle (12) clockwise until the valve is closed.
- Check the temperature of the air around the accumulator. The reading on the pressure gauge must be within the tolerances in Table 2.
- If the reading on the pressure gauge is too high, slowly open valve (7) to lower the pressure.
If the reading on the pressure gauge is too low, charge the accumulator.
When you charge an accumulator, make sure that you remove all of the oil from the oil end of the accumulator by charging the accumulator with nitrogen gas. Then, apply the service brakes repeatedly. The accumulator is charged when the application of the service brakes does not decrease the pressure of the nitrogen.
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| Illustration 3 | g00107133 |
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(1) Nipple
(2) Coupling assembly (3) Pressure gauge (4) Hose assembly (5) Coupling assembly (6) Nipple (7) Valve (8) Pressure gauge (9) Regulator assembly (10) Pressure regulating screw (11) Chuck for the nitrogen cylinder valve (12) Valve handle (13) Chuck (14) Hose assembly | |
- Assemble the nitrogen charging group. Connect chuck (11) to a dry nitrogen cylinder.
- Close valve (7) and open the valve on the nitrogen cylinder. Adjust pressure regulating screw (10) on the regulator assembly until pressure gauge (3) is at the required pressure for charging the accumulator. Refer to Table 2.
- Open valve (7) and charge the accumulator. Close valve (7).
- If the readings on pressure gauge (8) and on pressure gauge (3) remain identical, the accumulator has the correct charge.
If the reading on pressure gauge (8) decreases, open valve (7) and allow more nitrogen to go into the accumulator.
Perform Steps 1 through 4 until the readings on pressure gauge (8) and on pressure gauge (3) remain identical.
- Close valve (7) and the valve on the nitrogen cylinder.
- Turn valve handle (12) on chuck (13) completely in the counterclockwise direction.
- Remove the test equipment.
Nitrogen Charging Procedure for Rebuilt Accumulators
It will be necessary to remove all of the air from the valve end of the accumulator. When the accumulator is rebuilt, put approximately
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| Illustration 4 | g00107133 |
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(1) Nipple
(2) Coupling assembly (3) Pressure gauge (4) Hose assembly (5) Coupling assembly (6) Nipple (7) Valve (8) Pressure gauge (9) Regulator assembly (10) Pressure regulating screw (11) Chuck for the nitrogen cylinder valve (12) Valve handle (13) Chuck (14) Hose assembly | |
- Assemble the nitrogen charging group except for items (2), (3), (9), (10) and (11).
- Put the end of hose assembly (4) and nipple (1) into a clear container.
- Turn valve handle (12) on chuck (13) completely in the clockwise direction. Open valve (7).
- Start the engine. As oil flows into the oil end of the accumulator, the air and the oil will be pushed out of the valve end of the accumulator and through hose assembly (4). When the oil flow stops, the valve end of the accumulator will be free of air.
- Close valve (7) completely. Stop the engine. Allow any residual oil that may be in the hose assembly to drain into the container.
- Refer to the section "Nitrogen Charging Procedure" above for the remaining steps.
Note: The charging cycle will be longer because the piston must be moved to the oil end of the accumulator. Depress the brake pedal repeatedly to remove the oil pressure in the braking system. The piston in the accumulator will move toward the oil end of the accumulator.