 |
|
Personal injury or death can result if two persons are not used in the following procedure. |
|
|
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. |
|
|
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). |
| NOTICE |
|---|
|
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, PERJ1017, "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. |
Note: An accumulator pre-charge pressure of
| Accumulator Pre-charge Pressure/Temperature Relationship for the |
|
|---|---|
| Temperature | Pressure(1) |
| |
|
| |
|
| |
|
| |
|
| |
|
| |
|
| |
|
| |
|
| |
|
| |
|
| |
|
| (1) | Nominal allowable tolerance equals |
Note: The pressures in Table 1 are recommended for machines with a typical bucket. Machines with heavier buckets may require an increase in nitrogen pressure to keep the accumulator piston from striking the stop during normal roading. Raising the nitrogen pressure will result in a stiffer ride.
The following procedure is used to test and charge the brake accumulator.
To ensure that the nitrogen charge is correct, the brake accumulator piston must be at the bottom of the accumulator cylinder. 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.
If an accumulator has less than half of the required amount of pre-charge pressure, the accumulator will need charging. Operate the service brakes several times and then charge again. This procedure prevents trapping a quantity of oil in the accumulator giving an inaccurate pre-charge reading.
However, the temperature of the accumulator could be higher than the air temperature around the accumulator. In this case, the temperature of the accumulator should be used instead of the surrounding air temperature.
| Required Tools | ||||
|---|---|---|---|---|
| Tool | Item | Qty | Part No | Description |
| D | 175-5507 | Nitrogen Charging Group | ||
| D | D1 | 1 | 8S-4600 | Fitting |
| D2 | 1 | 8S-1506 | Coupling As | |
| D3 | 1 | 162-4147 | Hose As | |
| D4 | 1 | 8S-4599 | Coupling As | |
| D5 | 1 | 2S-5244 | Fitting | |
| D6 | 1 | 1S-8937 | Needle Valve | |
| D7 | 1 | 8T-0859 | Pressure Gauge
|
|
| D8 | 1 | 162-4146 | Regulator | |
| D9 | 1 | 7S-5106 | Chuck | |
| D10 | 1 | 1S-8938 | Chuck | |
| D11 | 1 | 1S-8941 | Hose As | |
| |
| Illustration 1 | g06268995 |
| (D) Tooling | |
Stop the engine. Release the braking system oil pressure.
Reference: Refer to System Operation, Testing and Adjusting, "System Pressure - Release" for the machine that is being serviced.
- Depress the service brake pedal repeatedly until there is no oil pressure in the brake hydraulic system.
- Remove cover (2) from the brake accumulator. Remove cap (1) from the valve assembly on the brake accumulator.
Show/hide table
Illustration 3 g06131435 Tooling D
(3) Pressure gauge
(4) Pressure regulating screw - Ensure valve (D6) is closed. Connect chuck (D9) or (D10) of Tooling (D) onto the nitrogen charging valve for the brake accumulator.
- Turn the valve handle on chuck (D9) or (D10) completely in the clockwise direction. Check the temperature of the air around the brake accumulator. The reading on the pressure gauge must be within the tolerances in Table 1.
- If the reading on the pressure gauge is too high, slowly open valve (D6) to lower the pressure. Close valve (D6). If the reading on the pressure gauge is too low, use the following procedure to charge the brake accumulator.
| |
| Illustration 2 | g06131431 |
|
Brake accumulator (1) Cap (2) Cover | |
Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures" for the required tooling, and the testing and charging procedure.
- Connect a hose from the nitrogen cylinder to valve (D6). Ensure valve (D6) is closed.
- Open the valve on the nitrogen cylinder. Adjust screw (4) on regulator assembly (D8) until pressure gauge (3) is at the correct charging pressure. Refer to Table 1 for the correct charging pressure.
- Put a charge of nitrogen into the brake accumulator. When pressure gauges (3) and (D7) show the same reading, and the readings do not change, the brake accumulator has the correct charge. Ensure that neither reading changes when valve (D6) is closed.
Charge Procedure for a New or Rebuilt Accumulator
Removing all the air from the nitrogen chamber of the brake accumulator is necessary. When the brake accumulator is new or rebuilt, put approximately
| NOTICE |
|---|
|
Low nitrogen charge can cause early pump failure because of short cycle times between the cut-in and cut-out operations of the brake accumulator charging valve. |
- Install chuck (D9) or (D10) onto the nitrogen charging valve for the brake accumulator.
- Turn the valve handle on chuck (D9) or (D10) completely in the clockwise direction.
- Start and run the engine until normal operating temperatures are reached. As hydraulic oil flows into the bottom of the brake accumulator, the air and then the oil will discharge through the test equipment. When the oil flow stops, the top of the brake accumulator will be free of air. The piston in the brake accumulator will be at the top of the accumulator cylinder.
- Close valve (D6) completely.
- Stop the engine. Release the braking system oil pressure.
Reference: Refer to System Operation, Testing and Adjusting, "System Pressure - Release" for the machine that is being serviced.
- Connect a hose from the nitrogen cylinder to valve (D6).
- Open the valve on the nitrogen cylinder. Adjust screw (4) on regulator assembly (D8) until pressure gauge (3) is at the correct charging pressure. Refer to Table 1 for the correct charging pressure.
- Open valve (D6) and charge the brake accumulator. Then, close valve (D6). If pressure gauges (3) and (D7) show the same reading, and the readings do not change, the brake accumulator has the correct charge.
If the pressure reading on gauge (D7) decreases, open valve (D6) and allow more nitrogen to fill the brake accumulator.
Perform this procedure until pressure gauge (D7) and pressure gauge (3) show the same reading. Make sure that neither reading changes when valve (D6) is closed.
- Close valve (D6). Close the valve on the nitrogen cylinder.
- Turn the valve on chuck (D9) or (D10) outward in the counterclockwise direction. Remove the test equipment.
| |
| Illustration 4 | g06131435 |
|
Tooling D (3) Pressure gauge (4) Pressure regulating screw | |