Note: The accumulator only maintains sufficient pressure for lowering the boom for approximately 1.5 minutes after the engine stops. The boom cannot be lowered by this method after this time limit.
When you test the pilot oil accumulator, the pressure in the pilot hydraulic system must be released. The temperature of the nitrogen gas must also be taken into account. The pressure and volume of dry nitrogen gas varies with temperature.
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Personal injury or death can result from sudden machine movement. Sudden movement of the machine can cause injury to persons on or near the machine. To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine. |
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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak. |
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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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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. |
- Ensure that the oil in the hydraulic system is at normal operating temperature. Park the machine on a smooth, level surface.
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Illustration 1 g01936539 Parking Brake Switch - Place the parking brake switch in the ON position. The ladder will lower. Ensure that all personnel are clear of the ladder before you lower the ladder.
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Illustration 2 g01936615 - Install the steering frame lock with the two pins. Place blocks in front of the wheels and behind the wheels.
- Raise the boom.
- Stop the engine.
- Turn the key to the ON position.
- Move the joystick in order to lower the boom. You should be able to lower the boom up to 1.5 minutes after the engine has stopped.
- Lower the boom to the ground.
- There are two accumulators for the brake system. One accumulator for the front brake and one accumulator for the rear brake. Both systems will need to be tested separately.
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Illustration 3 g01944348 The front manifold for the brake and differential lock is located under the cab on the left side of the frame. the side panel has been removed for this photo. - Connect a pressure gauge to the "GAC" port of the front brake manifold.
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Illustration 4 g01944349 The rear manifold for the brake and differential lock is located in the rear frame below the loader. Remove the oval shaped panel from the frame in order to access the manifold. - Connect a pressure gauge to the "GAC" port of the rear brake manifold.
- Run the machine for five minutes. Once the accumulator is fully charged observe the pressure gauge during the charge cycles. The pressure should be
15237 ± 4757 kPa (2210 ± 690 psi) .The duration of the charge cycle is approximately 45 seconds. If the accumulator charging cycles are occurring for a longer rate of 24 seconds, check the accumulator charge pressure. Accumulator charge pressure should be
6205 ± 1034 kPa (900 ± 150 psi) .If the accumulator charge pressure is at the recommended specification replace the manifold for the brake and differential lock. The charge valve for the accumulator is integral to the manifold and the valve is not serviceable.
| Required Tools | ||
| Part Number | Description | Quantity |
| 175-5507 | Nitrogen Charging Group | 1 |
| 224-5152 | Adapter | 1 |
| 8T-0846 | Pressure Gauge | 1 |
| Accumulator Precharge Pressure/Temperature Relationship for the |
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- Ensure that the oil in the hydraulic system is at normal operating temperature. Park the machine on a smooth, level surface.
- Ensure that all wheels are in contact with the ground. Keep the operating mode switch in the WORKING MODE position.
- Engage the parking brake.
- Stop the engine.
- Turn the engine start switch to the ON position. Move the implement joysticks and the steering through the full range of travel. Depress the brake pedal several times. This will release all the pressure in the hydraulic system.
- Turn the engine start switch to the OFF position.
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Illustration 5 g01944337 The front brake accumulator is located on the front frame with access through the belly guard. Show/hide table
Illustration 6 g01944336 The rear brake accumulator is located in the rear frame. The accumulator is accessible through the access panel on the top of the bunk. - Remove the plug from the accumulator. Attach a
0 to 1000 kPa (0 to 145 psi) pressure gauge to the accumulator. The indicated pressure on the gauge should be the pressure in Table 2. If the recorded pressure is not correct, perform Steps 8 through 13. - Install the 224-5152 Adapter to the accumulator.
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Illustration 7 g00107133 Nitrogen Charging Group
(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. - Ensure that valve (7) is closed. Install chuck (13) onto the adapter for the pilot accumulator. 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 pressure gauge (8) 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 accumulator:
- Connect a hose from the nitrogen cylinder to chuck (11).
- 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.
- Slowly open valve (7) and charge the accumulator. Then, close valve (7). If pressure gauge (8) and pressure gauge (3) show the same reading and the readings do not change, the 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. Remove the adapter. Reinstall the plug.
- Proceed to the "Test" section.
