| Tools Needed | |||
|---|---|---|---|
| Tool | Part Number | Part Description | Qty |
| A | 7S-5437 | Nitrogen Charging Group | 1 |
| B | 1U-5551 | Adapter | 1 |
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Personal injury or death can result from improper accumulator charging. Dry nitrogen is the only gas approved for use in the accumulator. Charging the accumulator with oxygen gas will cause an explosion. This danger will not happen if nitrogen cylinders with standard CGA Compressed Gas Association, Inc. Number 580 connections are used. When ordering nitrogen gas, be sure that the cylinders are equipped with CGA Number 580 Connections. Do not use color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders. 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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| Charging Pressure and Temperature Relationship for the 9T-4785 Steering Accumulator ( 8300 kPa (1204 psi)) |
|
|---|---|
| Temperature | Pressure (1) |
-7°C (20°F) |
7825 kPa (1135 psi) |
-1°C (30°F) |
7984 kPa (1158 psi) |
4°C (40°F) |
8143 kPa (1181 psi) |
10°C (50°F) |
8301 kPa (1204 psi) |
16°C (60°F) |
8460 kPa (1227 psi) |
21°C (70°F) |
8625 kPa (1251 psi) |
27°C (80°F) |
8777 kPa (1273 psi) |
32°C (90°F) |
8935 kPa (1296 psi) |
38°C (100°F) |
9095 kPa (1319 psi) |
43°C (110°F) |
9253 kPa (1342 psi) |
49°C (120°F) |
9412 kPa (1365 psi) |
| ( 1 ) | The allowable tolerance on nominal pressure is 70 kPa (10 psi) . |
Check that the engine has not been running for at least five minutes. This will allow the oil level in the steering accumulators to decrease. The accumulator bladder must be on the bottom of the cylinder. This will ensure that the pressure of the nitrogen charge is correct.
The accumulator has a dry charge of approximately 8300 kPa (1204 psi) .
Checking the Nitrogen Charge
 | |
| Illustration 1 | g00281220 |
Nitrogen charging group (1) . (2) . (3) . (4) . (5) . (6) . (7) . (8) . (1) Pressure gauge (2) Connection to nitrogen cylinder valve (3) Regulator assembly (4) Valve (5) Pressure gauge (6) Pressure regulating screw (7) Valve handle (8) Chuck | |
 | |
| Illustration 2 | g00302124 |
(9) Cap | |
- Remove cap (9) from the top of the accumulator. Install Tool (B) on the accumulator valve.
- Install chuck (8) on Tool (B) .
Note: Do not connect the hose to valve (4) . Make sure that valve (4) is closed.
- Turn valve (7) on chuck (8) clockwise.
- Use 13800 kPa (2000 psi) pressure gauge (5) to check the nitrogen charge in the accumulator.
- The pressure on the gauge must be within the tolerances that are listed in Table 2 .
- If the pressure reading on the gauge is too high, lower the pressure by slowly opening valve (4) .
- If the pressure reading on the gauge is too low, charge the accumulator.
Charging the Accumulator
- Close valve (4) .
- Connect the hose from valve (4) to pressure gauge (1) . The hose is part of the nitrogen charging group.
- Open the valve on the nitrogen cylinder. Adjust screw (6) on the regulator assembly until gauge (1) is at the pressure that will charge the accumulator. Use Table 2 as a reference for the correct charging pressure.
- Open valve (4) and charge the accumulator.
- When the pressure reading on gauge (5) and the pressure reading on gauge (1) are identical, shut valve (4) .
- If there is a decrease in pressure on gauge (5) , open valve (4) . This allows more nitrogen to enter the accumulator.
- Repeat Steps 5 and 6 until the following items occur:
- Pressure readings of gauges (5) and (1) are identical.
- Pressure readings do not change.
- Pressure readings of gauges (5) and (1) are identical.
- Close the valve on the nitrogen cylinder.
- Turn valve (7) on chuck (8) counterclockwise.
- Remove the test equipment.
Charging a Rebuilt Accumulator
Remove all nitrogen from the end of the accumulator. When the accumulator is rebuilt, put approximately 0.9 L (1 qt) of SAE 10W hydraulic oil in the end of the accumulator that holds nitrogen. This oil will be used to help remove air from the end of the accumulator.
After the accumulator is installed on the machine, use the following procedure to charge the accumulator:
- Use the same equipment that was used to check the nitrogen charge in the accumulator.
- Connect a drain hose to valve (4) .
- Turn valve (7) on chuck (8) clockwise.
- Open valve (4) .
- Start the engine. Run the engine until the engine is warm. As the oil is forced to the bottom of the accumulator, the air and the oil will be forced through the test equipment. When the oil flow stops, the top of the accumulator will be free of air.
| NOTICE |
|---|
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the machine. 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 in Caterpillar machines. Dispose of all fluids according to local regulations and mandates. |
- Close valve (4) .
- Stop the engine. Allow the oil pressure to decrease for five minutes. The bladder in the accumulator will be at the top of the accumulator.
- Charge the accumulator with nitrogen. Follow the procedure in "Charging the Accumulator" .