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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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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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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the work tools have been lowered to the ground, and the oil is cool before removing any components or lines. Remove the 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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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the work tool to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock. |
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| NOTICE |
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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. |
Introduction
This procedure describes the method for testing and charging the ride control accumulator. The procedure includes the following:
- Shutdown procedure
- Measuring machine carry pressure
- Discharging and charging procedure
- Testing the ride control diverter valve
- Road test
Required Tools
 | |
| Illustration 1 | g02571852 |
Tooling (A) 198-4240 Digital Pressure Indicator Gp | |
| Tool | Item | Qty | Part No | Description |
|---|---|---|---|---|
| A | 198-4240 | Digital Pressure Indicator Gp | ||
| A1 | 1 | 198-4234 | Digital Indicator | |
| A2 | 1 | 198-4237 | Pressure Sensor Gp (0 to 3,445 kPa (0 to 500 psi)) |
|
| A2 | 1 | 198-4238 (1) | Pressure Sensor Gp (0 to 34,450 kPa (0 to 5,000 psi)) |
|
| A2 | 1 | 198-4239 | Pressure Sensor Gp (0 to 41,368 kPa (0 to 6,000 psi)) |
|
| A2 | 1 | 251-9600 (2) | Pressure Sensor Gp (0 to 68,900 kPa (0 to 10,000 psi)) |
|
| A3 | 1 | 198-4236 | Adapter Cable As | |
| ( 1 ) | This sensor must be purchased separately. The sensor is not included in the 198-4240 Digital Pressure Indicator Gp |
| ( 2 ) | This sensor can only be used on large diameter pressure taps like 6V-3965 Fitting . |
Shutdown Procedure
- Start the engine and move the machine to a hard, level surface.
- Move the transmission control lever to the NEUTRAL position.
- Engage the parking brake.
ReferenceFor more information about preparing the machine for testing and charging the ride control accumulator, refer to the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting".
- Press and hold ride control button (1) for 2 seconds to put the ride control system in service mode. Two indicator lights should be illuminated.
 | |
| Illustration 2 | g03823740 |
Location of ride control button on the panel (1) Ride Control | |
- Lower the bucket to the ground.
- Move the lift control lever to the FLOAT position. The hydraulic pressure in the accumulator will be relieved.
ReferenceFor more information about releasing the hydraulic pressure in the system, refer to the Service Manual module Testing and Adjusting, "System Pressure - Release".
- Turn the engine start switch key to the OFF position.
- Disconnect the hydraulic lines for servicing, as needed.
Measuring Machine Carry Pressure
- Move the machine to a smooth horizontal location. Move away from working machines and personnel. Lower the work tool to the ground.
- Allow only one operator on the machine. Keep all personnel away from the machine or in the view of the operator.
- Move the transmission control lever to the NEUTRAL position.
- Engage the parking brake.
- Place the steering frame lock in the LOCKED position.
 | |
| Illustration 3 | g02181445 |
- Start the engine. Operate the engine at high idle. Continuously stall the RACK BACK function while simultaneously raising the lift arms at full speed. When the lift arms are almost raised, cycle the tilt cylinder almost to the FULL DUMP position. Then move the tilt cylinders to the full RACK BACK position. Continuously stall the RACK BACK function and simultaneously lower the lift arms back to the ground level position. Without stalling the RACK BACK function, cycle the lift function to raise the lift arms fully. Then lower the lift arms in order to allow the pump to operate at low-pressure briefly and circulate oil through the system. Repeat this process in order to increase the temperature of the oil to normal operating temperature of approximately 54° to 70°C (129° to 158°F).
- Lower the lift arms to the ground.
- Move the lift control lever to the FLOAT position. The hydraulic pressure in the accumulator will be relieved.
For more information about releasing the hydraulic pressure in the system, refer to Testing and Adjusting, "System Pressure Release".
- Turn the engine start switch to the OFF position.
For more information about preparing the machine for testing and charging the ride control accumulator, refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".
- Connect a 0 to 35,000 kPa (0 to 5076 psi) pressure gauge on the load sense signal pressure tap (2) .
Note: Do not stall any of the implement functions once the gauge is installed. This action could result in the gauge being over pressurized and damaged.
Note: The pressure tap is located on the right side of the machine on the non-engine end frame near the articulated hitch.
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| Illustration 4 | g03823771 |
(2) Implement pump load sense pressure tap | |
- Start the engine. Rack the worktool into the desired carry position. Fully lower the worktool. Insure the worktool is below the desired carry position.
- Increase the engine speed to high idle. Give steady RAISE command (suggested roughly 20 percent command) that allows the work tool to travel smoothly through the desired carry position. While the work tool travels through the desired carry position, observe the pressure gauge and record this value. Stop RAISE command after traveling through desired carry position. Repeat three times and record the average pressure.
Note: Pressure may monetarily "spike" with the initial command prior to stabilizing. Make sure to record the stabilized value through the carry position, not the maximum pressure.
- Press and hold the ride control button (1) for 2 seconds to put the ride control system, in service mode. Two indicator lights should be illuminated.
| | |
| Illustration 5 | g03823740 |
- Position the worktool on the ground.
- Move the lift control lever to the FLOAT position. The hydraulic pressure in the accumulator will be relieved.
- Turn the engine start switch to the OFF position.
- Remove the test equipment.
- Use recorded value as "Carry Pressure with Empty Worktool" and determine correct precharge from Table 2.
Discharging and Charging Procedure
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| Illustration 6 | g03823829 |
Inside loader frame (Right side looking forward) (3) Ride control accumulator | |
Discharging Procedure
Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures" for the required tooling, and the testing and charging procedure.
Nitrogen Charging Procedure
Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures" for the required tooling, and the testing and charging procedure.
Accumulator Precharge Setting Guidelines
Accumulator precharge pressure should be set approximately 1500 to 2000 kPa (217 to 290 psi) under the carry pressure of the machine with the worktool in the desired roading carry position. The carry pressure will change depending on the worktool size and desired carry position.
| Accumulator Precharge Recommendations at 21° C (70° F) |
|
|---|---|
| Carry Pressure with Empty Worktool kPa (psi) (1) |
Accumulator Precharge kPa (psi) |
3500 kPa (507 psi) |
1750 kPa (253 psi) |
4000 kPa (580 psi) |
2250 kPa (326 psi) |
4500 kPa (652 psi) |
2750 kPa (399 psi) |
5000 kPa (725 psi) |
3250 kPa (471 psi) |
5500 kPa (797 psi) |
3750 kPa (544 psi) |
6000 kPa (870 psi) |
4250 kPa (616 psi) |
6500 kPa (942 psi) |
4750 kPa (689 psi) |
| ( 1 ) | This pressure should be measured using "Measuring Machine Carry Pressure" included above |
Note: To ensure that the accumulator nitrogen charge is correct, the accumulator piston must be at the bottom of the accumulator cylinder. This procedure can be done by following "Shutdown Procedure" to drain the accumulators.
Note: Nitrogen pressure varies with the temperature. To obtain the most accurate nitrogen charge, the temperature of the accumulator should equal the outside air temperature. If the machine has recently been operated, turn off the machine. Wait for some time to allow the hydraulic oil and accumulator temperatures to stabilize to outside air temperature.
Note: The accumulator precharge pressure should not be set above the carry pressure. This action will ensure that the accumulator piston will not strike the internal stop during roading. The pressures in Table 2 are suggested for specific carry pressures.
Note: The suggestions in Table 2 are intended to be a good starting point. The precharge pressure may still need adjusted for operator comfort during roading.
Note: Refer to accumulator warning label for pressure limitations so the accumulator is not over pressurized.
The pressures in Table 3 are adjustments that should be made to the result from Table 2 if the outside air temperature is not around 21° C (70° F).
| Accumulator Precharge Pressure Temperature Relationship for a Typical Ride Control Accumulator | |
|---|---|
| Temperature ° C (° F) |
Pressure Correction kPa (psi) |
−7° C (20° F) |
−270 kPa (−39 psi) |
−1° C (30° F) |
−215 kPa (−31 psi) |
4° C (40° F) |
−160 kPa (−23 psi) |
10° C (50° F) |
−105 kPa (−15 psi) |
16° C (60° F) |
−50 kPa (−7 psi) |
21° C (70° F) |
0 kPa (0 psi) |
27° C (80° F) |
60 kPa (8 psi) |
32° C (90° F) |
115 kPa (16 psi) |
38° C (100° F) |
170 kPa (25 psi) |
43° C (110° F) |
225 kPa (32 psi) |
49° C (120° F) |
280 kPa (40 psi) |
Testing the Ride Control Diverter Valve
The following procedure is used to determine whether the check valve for the rod end of the lift cylinders is operating correctly. Perform this test after the ride control accumulator is charged.
- Start the machine.
- Press ride control button (1) to turn off the ride control system.
- Place the bucket in the full DUMP position. Lift the front wheels off the ground by moving the lift control lever to the LOWER position.
- When the front wheels are off the ground, place the lift control lever in the HOLD position. In approximately 5 seconds, press and hold ride control button (1) for 2 seconds to turn on the ride control system. Two indicators should be illuminated. The front wheels should lower to the ground.
If the wheels do not lower to the ground, the diverter spool has not shifted to the ON position. The following conditions are probable causes:
- The keypad or CAN bus has failed.
- The solenoid coil on the diverter valve is faulty.
- The cartridge valve in the diverter valve is faulty.
- The diverter valve spool sticks.
- The pilot oil passage to the ride control diverter valve is blocked.
To test the check valve for the head end of the lift cylinders, drive the machine and evaluate the smoothness of the ride.
- The keypad or CAN bus has failed.
Road Test
- Place the steering frame lock in the STORE position.
- Put a typical load in the bucket.
- Press and hold ride control button for 2 seconds to put the ride control system in service mode. Two indicators should be illuminated.
- Drive the machine over a rough road surface.
- If the operator wants:
- Less Lift Cylinder Movement - Decrease the precharge pressure in increments of 345 kPa (50 psi) until comfortable.
- More Lift Cylinder Movement - Increase the precharge pressure in increments of 345 kPa (50 psi) until comfortable.
- Less Lift Cylinder Movement - Decrease the precharge pressure in increments of 345 kPa (50 psi) until comfortable.
Note: If the accumulator is striking the internal stop with an empty worktool, decrease the precharge pressure as needed. This action may compromise loaded worktool comfort, but will eliminate the noise from the accumulator.
Note: The ride control accumulators are equipped with warning labels that specify maximum pressures. Make sure that these warning labels are referenced before adjusting precharge pressure. Only add enough nitrogen in order to achieve a suitable ride for the typical payload of the machine.
Note: For more information on the nitrogen charging procedure, refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures".