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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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Hot hydraulic oil under high pressure can remain in the components of the hydraulic system or the power train system after the engine has been stopped. The uncontrolled release of the hydraulic oil can cause sudden machine movement and can also result in the following conditions:
If hydraulic oil penetrates body tissue, the injury must be treated immediately by a doctor who is familiar with this type of injury. Use a board or a piece of cardboard to check for a hydraulic oil leak. Make sure that all of the attachments have been lowered to the ground and that all trapped pressure has been released from the hydraulic system and the power train system. Also, make sure that the hydraulic oil is cool before the removal of any components or lines. Remove the hydraulic 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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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. |
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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 you order nitrogen gas, be sure that the cylinders are equipped with CGA No. 580 Connections. Do not use color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders. |
Nitrogen gas pressure varies with the temperature. To obtain the most accurate nitrogen charge, the temperature of the accumulator must be identical to the air temperature around the accumulator.
Note: Adjust the pressure for ambient conditions, as required. Refer to the following table for the accumulator precharge pressure/temperature relationship.
| Accumulator Precharge Pressure/Temperature Relationship for the |
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| Accumulator Specification | |||
| Date | Equipment ID Code | ||
| Item | Specification | Actual | Engine Speed |
| Accumulator Charge Pressure | |
High Idle | |
The accumulator stores hydraulic oil pressure that can be used to lower the implements when the engine is off. The accumulator is located on the pilot manifold.
The following procedure will determine if the accumulator for the pilot system is charged to the appropriate pressure.
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| Illustration 1 | g02726620 |
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Tooling (B) | |
| Tool | Item | Qty | Part Number | Description |
|---|---|---|---|---|
| B | B1 | 1 | 8T-0856 | Pressure Gauge
(0 to 6,000 kPa (0 to 870 psi)) |
| B2 | 1 | 6V-3989 | Fitting | |
| B3 | 2 | 6V-4143 | Quick Connect Coupler | |
| B4 | 1 | 177-7860 | Hose As (10 ft) |
Test Preparation - Accumulator Charge Pressure
- Move the machine to a smooth horizontal location.
- Engage the parking brake.
- Lower all of the implements.
- Stop the engine.
- Turn the key to the ON position. Make sure that the implement lockout switch is turned to the UNLOCKED position. Move the implement control levers to all positions several times in order to release any pressure in the hydraulic system.
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Illustration 2 g03738049 - Attach tooling (B) to pressure tap (1) located by the filter.
Test Procedure (Accumulator Charge Pressure)
- Start the engine. Warm the hydraulic oil to a minimum temperature of
65° C (150° F) . - Operate the engine at HIGH IDLE.
- Exercise the implement hydraulics. At the accumulator, the pilot pressure at tooling (1) should be approximately
3585 kPa (520 psi) .
Note: There is no test for checking the actual charge pressure of the accumulator on the machine.
Charging Procedure - Accumulator Charge
- Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures".
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Illustration 3 g02788256 - The accumulator is located underneath the operator in the cab. Charging valve (2) is located on the top of the accumulator.
Note: Do not attempt to charge the accumulator until all pressure has been removed from the pilot accumulator.
- When all of the adjustments are complete, remove all tooling and reinstall all guards.
