| The Required Tools | ||
| 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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Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the brake system. |
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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand. |
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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, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates. |
Note: Perform this test only if the test for the steering and brake manifold valve was not to specifications.
Stop the engine. Depress the brake pedal at least fifty times in order to release the brake pressure.
To ensure that the nitrogen charge is correct, each brake accumulator piston must be at the bottom of the accumulator cylinder. Nitrogen gas pressure varies with the temperature. To obtain the most accurate nitrogen charge, the temperature of each accumulator must be identical to the air temperature around the accumulators.
If an accumulator has less than half of the required amount of precharge pressure, the accumulator should be charged, and then charged again after operating the service brakes several times. This prevents trapping a quantity of oil in the accumulator which will give an inaccurate precharge reading.
However, the temperature of the accumulators could be higher than the air temperature around the accumulators. In this case, the temperature of the accumulator should be used instead of the surrounding air temperature.
Note: The pressures in the following table are for an ambient air temperature of 21°C (70°F). Adjust the pressure for other ambient conditions, as required.
| Accumulator Precharge Pressure/Temperature Relationship for the 6900 kPa (1000 psi) Brake Accumulators |
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| Temperature | Pressure |
-7°C (20°F) |
2240 kPa (325 psi) |
-1°C (30°F) |
2061 kPa (299 psi) |
4°C (40°F) |
2106 kPa (305.5 psi) |
10°C (50°F) |
2151 kPa (312 psi) |
16°C (60°F) |
2196 kPa (318.5 psi) |
21°C (70°F) |
2241 kPa (325 psi) |
27°C (80°F) |
2286 kPa (331.5 psi) |
32°C (90°F) |
2330 kPa (338 psi) |
38°C (100°F) |
2375 kPa (344.5 psi) |
43°C (110°F) |
2420 kPa (351 psi) |
49°C (120°F) |
2444 kPa (354.5 psi) |
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| Illustration 1 | g00107133 |
Charging Equipment (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. | |
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| Illustration 2 | g00279570 |
Brake Accumulator (15) Cover. (16) Cap. | |
Note: The accumulators are located on the left side of the machine and the accumulators are attached to the frame.
- Remove cover (15) from the brake accumulator. Remove cap (16) from the valve assembly on the accumulator.
- Use a 0 to 4000 kPa (0 to 580 psi) pressure gauge (8) to check the nitrogen charge in the brake accumulator.
- Install chuck (13) onto the nitrogen charging valve for the brake accumulator.
- Open valve (7) and charge line (14) to the correct precharge. Refer to Table 2.
- Turn valve handle (12) completely in the clockwise direction. 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) in order to lower the pressure. If the reading on the pressure gauge is too low, use the following procedure to charge the brake accumulator:
- Connect a hose from the nitrogen cylinder to valve (7) .
- Close valve (7) and open the valve on the nitrogen cylinder. Adjust screw (10) on regulator assembly (9) until pressure gauge (3) is at the correct charging pressure. Refer to Table 2 for the correct charging pressure.
- Open valve (7) and charge the brake accumulator. Then, close valve (7). If pressure gauge (8) and pressure gauge (3) show the same reading and the readings do not change, the brake accumulator has the correct charge.
If the pressure reading on gauge (8) decreases, open valve (7) and allow more nitrogen to fill the accumulator.
Perform this procedure until pressure gauge (8) and pressure gauge (3) show the same reading. Make sure that neither reading changes when valve (7) is closed.
- Close valve (7). Close the valve on the nitrogen cylinder.
- Turn valve (12) on chuck (13) outward in the counterclockwise direction. Remove the test equipment.
- Perform this procedure for the other brake accumulator.