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Pressurized System! Hydraulic accumulators contain gas and oil under high pressure. DO NOT disconnect lines or disassemble any component of a pressurized accumulator. All gas pre-charge must be removed from the accumulator as instructed by the service manual before servicing or disposing of the accumulator or any accumulator component. Failure to follow the instructions and warnings could result in personal injury or death. Only use dry nitrogen gas to recharge accumulators. See your Cat dealer for special equipment and detailed information for accumulator service and charging. |
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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. |
Gas pressure is variable 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.
Note: The temperature of the accumulator may change as the accumulator is being charged due to the expansion or compression of the nitrogen charge. Charge the accumulator in several steps to ensure a correct charge.
Note: One 6,000 psi nitrogen bottle with CGA677 connectors is required to charge on empty 32 L accumulator. The contents of one 6,000 psi bottle will be around 482 cu ft.
| Charge Pressures and Temperatures | |
| Temperature | Pressure |
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| Illustration 1 | g03258476 |
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Cap for charging port on swing accumulator | |
The swing system is equipped with one
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| Illustration 2 | g01963393 |
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| Illustration 3 | g02726225 |
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Tooling (D) | |
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| Illustration 4 | g01964413 |
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Tooling (F) | |
| Tool | Item | Qty | Part Number | Description |
| D | D1 | 1 | 162-4147(1) | Hose As |
| D2 | 1 | 8T-0859(1) | Pressure Gauge ( |
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| D3 | 2 | 8S-1506(1) | Coupling As | |
| D4 | 1 | 1S-8937(1) | Needle Valve | |
| D5 | 2 | 2D-7325(1) | Pipe Tee | |
| D6 | 1 | 2S-5244(1) | Fitting | |
| D7 | 1 | 346-3622 | Valve - Relief (Pop-Off) | |
| D8 | 1 | 338-0500 | Regulator | |
| D9 | 1 | 1S-8938(1) | Chuck | |
| D10 | 1 | 1S-8941(1) | Hose As | |
| D11 | 1 | 3F-2779 | Pipe Coupling | |
| F | 1 | 164-3310 | Infrared Thermometer | |
| (1) | Part included in the 175-5507 Nitrogen Charging Group |
Use the pressure sensor on the accumulator gas end and tooling (F) to check the charge pressure of the swing accumulator.
- Check the charge pressure of the swing accumulator.
- Enter the "Service" menu of the monitor.
- Enter password "9992".
- Select "Status".
- Select "Hybrid System Status".
- Use tooling (F) to check the temperature of the swing accumulator.
- Compare the swing accumulator charge pressure and temperature to Table 1.
Note: If the gas pressure is out of specification, then verify the charge pressure with a pressure gauge. Refer to "Testing and Charging Procedure for the Accumulator Precharge Pressure".
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| Illustration 5 | g03417260 |
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(1) Cap
(2) Hex nut (3) Nitrogen charging valve | |
- Attach hose assembly (D10) to nitrogen charging chuck (D9).
- Remove cap (1) from nitrogen charging valve (3).
- Attach nitrogen charging chuck (D9) to nitrogen charging valve (3).
- Hold nitrogen charging valve (3) with one wrench. Turn hex nut (2) with a second wrench in a counterclockwise direction.
Loosening the nut opens nitrogen charging valve (3). Three turns will fully open the valve. Opening the valve will release all the nitrogen from the accumulator through hose assembly (D10).
Testing and Charging Procedure for the Accumulator Precharge Pressure
Note: Test the accumulator precharge pressure when the machine is not running and all pressure has been released from the hydraulic system. For information on releasing the system pressure, refer to Testing and Adjusting, "System Pressure - Release".
- Remove protective cap (1) on nitrogen charging valve (3).
- Assemble tooling (D).
- Attach tooling (D) to nitrogen charging valve (3) on the accumulator.
Note: Do not attach the regulator to the nitrogen charging tank now.
- Turn the valve handle for needle valve (D4) all the way in the clockwise direction. Completely turning the valve handle will ensure the needle valve (D4) is closed.
- Hold nitrogen charging valve (3) with one wrench. Turn hex nut (2) with a second wrench in a counterclockwise direction.
Loosening the nut opens nitrogen charging valve (3). Three turns will fully open the valve.
- Read pressure gauge (D2) to determine the charge pressure in the accumulator. If charging is needed, attach regulator (D8) to a nitrogen tank.
- Adjust pressure regulating screw on regulator (D8) to obtain the correct pressure reading on the gauge. Refer to Table 1.
Note: If the machine has been running for some time, the temperature of the accumulator may be different from the ambient temperature of the outside air. Use tooling (F) to determine the current temperature of the accumulator.
- Open needle valve (D4). Nitrogen will flow from the regulator to the accumulator. When gauge (D2) reads the correct pressure, close needle valve (D4).
- Allow the accumulator to sit for a half hour to allow the temperature to equalize and check the pressure. Adjust the charge if necessary.
- Once the accumulator is charged, hold nitrogen charging valve (3) with one wrench. Turn hex nut (2) with a second wrench in a clockwise direction. Tightening the nut closes nitrogen charging valve (3). Remove chuck (D9). Remove regulator (D8) from the nitrogen tank.
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| Illustration 6 | g03417260 |
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(1) Cap
(2) Hex nut (3) Nitrogen charging valve | |
Accumulator Charge Procedure for a Rebuilt Piston Type Accumulator
When the accumulator has been rebuilt, the air must be removed from the upper nitrogen chamber of the accumulator. The oil is added before the accumulator is charged. Use hydraulic oil to help remove the air from the upper nitrogen chamber, and to lubricate the top seal of the piston in the accumulator. The piston within the accumulator is typically cupped on the nitrogen side. Secure the accumulator in a vertical position with the gas side facing up. Ensure that the piston is seated against the end cap on the gas side of the accumulator. Remove the nitrogen charging valve. Pour clean hydraulic oil through the hole where the nitrogen charging valve was located. Pour the oil until the oil completely fills the piston cavity and overflows out the hole. Install the nitrogen charging valve to the specified torque.
After the installation of the rebuilt accumulator is complete, use the following steps to charge the accumulator.
Note: One 6,000 psi nitrogen bottle with CGA677 connectors is required to charge on empty 32 L accumulator. The contents of one 6,000 psi bottle will be around 482 cu ft.
- Remove protective cap (1) on nitrogen charging valve (3) on the swing accumulator.
- Assemble tooling (D).
- Attach tooling (D) to nitrogen charging valve (3) on the swing accumulator.
- Turn the valve handle for needle valve (D4) all the way in the clockwise direction. Completely turning the valve handle will ensure the needle valve (D4) is closed.
- Hold nitrogen charging valve (3) with one wrench. Turn hex nut (2) with a second wrench in a counterclockwise direction.
Loosening the nut opens nitrogen charging valve (3). Three turns will fully open the valve.
- Attach regulator (D8) to a nitrogen bottle.
- Adjust pressure regulating screw on regulator (D8) to obtain the correct pressure reading on the gauge. Refer to Table 1.
Note: If the machine has been running for some time, the temperature of the accumulator may be different from the ambient temperature of the outside air. Use tooling (F) to determine the current temperature of the accumulator.
- Slowly open needle valve (D4). Nitrogen will flow from the regulator to the accumulator (A). When gauge (D2) reads the correct pressure or the pressure has equalized, close needle valve (D4).
Note: Use nitrogen tank (1) to fill accumulator at an approximate rate of
300 kPa (45 psi) per minute. Fill the accumulator until the accumulator and nitrogen tanks equalize in pressure or the target charge pressure is reached. Make sure both the accumulator and nitrogen tank reach equilibrium temperature with the surroundings before making final pressure measurement. - Once the accumulator is charged, hold nitrogen charging valve (3) with one wrench. Turn hex nut (2) with a second wrench in a clockwise direction. Tightening the nut closes nitrogen charging valve (3). Remove chuck (D9). Remove regulator (D8) from the nitrogen tank (3).
- Allow the accumulator to sit for a half hour to allow the temperature to equalize and check the pressure. Adjust the charge if necessary.
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| Illustration 7 | g03417260 |
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(1) Cap
(2) Hex nut (3) Nitrogen charging valve | |