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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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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. |
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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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Personal injury can result from rotating and moving parts. Stay clear of all rotating and moving parts. Never attempt adjustments while the machine is moving or the engine is running unless otherwise specified. The machine must be parked on a level surface and the engine stopped. Attach a "Do Not Operate" or similar warning tag to the start switch and controls before servicing, repairing, or making adjustments to the machine. |
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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. |
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.
| Charge Pressure for the Accumulator at Different Temperatures | |
| Temperature | Pressure |
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| Accumulator Precharge Pressure | ||
| Pressure | Actual | |
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Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures" for the instructions and tooling required for the charge procedure.
This information includes the following test:
- Brake Accumulator test and charge
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| Illustration 1 | g06221008 |
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Tooling (T2) | |
| Required Tools | ||||
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| Item | Qty | Part Number | Part Name | |
| T2a | 1 | 8T-0859 | Pressure Gauge ( |
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| T2b | 1 | 6V-3989 | Fitting | |
| T2c | 2 | 6V-4143 | Quick Connect Coupler | |
| T2d | 1 | 177-7860 | Hose As ( |
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| T2d | 1 | 177-7861 | Hose As ( |
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| T2d | 1 | 177-7862 | Hose As ( |
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- Move the machine to a smooth, horizontal location that is away from operating machines and away from personnel.
- Permit only one operator on the machine. Keep all other personnel away from the machine or in the operator sight.
- Rotate the steering wheel to a NEUTRAL position.
- Move the transmission control to park to engage the parking brake.
- Lower or retract the implements.
- Stop the engine.
- Turn the key to the ON position, but do not start the engine.
- Make multiple applications to the service brakes and engage and disengage the parking brake to exhaust stored hydraulic pressure in the accumulators.
- Place blocks in front and behind the wheels.
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Illustration 2 g06185680 (1) Parking Brake Outlet Pressure Port - Connect tooling (T2) to parking brake outlet pressure port (1).
- Start and operate the engine at low idle for 1 minute to fully charge the accumulator.
- Shut off the engine, and move the engine start switch to the on position.
- Move transmission control (2) to the neutral position.
- Move transmission control (2) from the park position to the neutral position to engage and disengage to parking brake.
- Observe the pressure on tooling (B). As successive parking brake applications are made, the pressure reading will fall. Continue to engage and disengage the parking brake until the pressure drops to zero.
Note: The last pressure reading recorded from tooling (B) is a close approximation of the nitrogen precharge in the accumulator.
- Refer to Table 1 for the appropriate accumulator charge.
Note: If the precharge of the original accumulator is out of the specifications, the accumulator will need to be replaced. The replacement accumulator has a charging valve and may be charged if needed.
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| Illustration 3 | g06188023 |
| (2) Transmission Control | |
- Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures" for the instructions and tooling required for the charge procedure.
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Illustration 4 g06188092 (4) Accumulator
(5) Valve
(6) Cap - Accumulator (4) is on the left side of the machine beneath the fender. Charging valve (5) is on the top of the accumulator under the cap (6).
Note: Do not attempt to charge the accumulator until all pressure has been removed from the pilot accumulator.
