The following procedure is used to adjust the maximum pressure to the grapple cylinder. The maximum pressure is controlled by two signal limiter valves in the implement control valve. One signal limiter valve controls the maximum pressure for opening the grapple. The other signal limiter valve controls the maximum pressure for closing the grapple.
Before testing or adjusting the signal limiter valves, ensure that the standby pressure and high pressure cutoff are adjusted correctly.
Reference: For more information on the standby pressure, refer to Testing and Adjusting, "Piston Pump (Implement) Standby Pressure - Test and Adjust" for the machine that is being serviced.
Reference: For more information on the high pressure cutoff, refer to Testing and Adjusting, "Piston Pump (Implement) High Pressure Cutoff - Test and Adjust" for the machine that is being serviced.
In order to accurately adjust the cylinder pressure of the grapple cylinder, the valve spool for the grapple control system must be moved fully from the HOLD position. The proportional solenoid for the valve spool must be fully activated. Ensure that the solenoid is fully activated by adjusting the maximum current from the toggle switch on the right implement joystick above 680 mA.
Reference: For more information on adjusting the maximum current on the proportional solenoid, refer to Testing and Adjusting, "Joystick Control Preferences - Adjust" for the machine that is being serviced.
| Required Tools | ||
| Part Number | Description | Quantity |
| 198-4240 | Digital Pressure Indicator Group | 1 |
| 161-8958 | Wrench | 1 |
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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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| 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, "AVSpare Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on AVSpare products. Dispose of all fluids according to local regulations and mandates. |
- Park the machine on a level surface.
- Ensure that the hydraulic oil in the system is at normal operating temperature.
- Place the operating mode switch in the ROADING MODE position.
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| Illustration 1 | g00800981 |
Operating Mode Switch on the Right Hand Control Unit | |
- 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 | g00919915 |
Parking Brake Switch | |
- Stop the engine.
- Block the wheels.
- Install the steering frame lock.
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| Illustration 3 | g00913309 |
- Move the cover off the implement control valve.
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| Illustration 4 | g00914499 |
Location of the Implement Control Valve | |
- Install the 198-4240 Digital Pressure Indicator Group on pressure tap (1).
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| Illustration 5 | g00947790 |
End View of the Implement Control Valve (1) Pressure tap for piston pump (implement) signal pressure. (2) Pressure tap for piston pump (implement) supply pressure. | |
- Start the engine. Place the operating mode switch in the WORKING MODE position. Increase the engine speed to 1500 rpm.
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| Illustration 6 | g00800981 |
Operating Mode Switch on the Right Hand Control Unit | |
- Move the boom and the stick in order to prevent the grapple from contacting the machine when the grapple is fully open.
- Perform step 13 in order to adjust the pressure for closing the grapple. Perform step 14 in order to adjust the pressure for opening the grapple.
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| Illustration 7 | g00659829 |
Implement Control Valve (3) Valve section (Grapple). (4) Signal limiter valve (GRAPPLE CLOSE). (5) Signal limiter valve (GRAPPLE OPEN). | |
- Grapple Close:
- Slowly move the toggle switch on the right implement joystick to the GRAPPLE CLOSE position. Allow the grapple to fully close. Hold the toggle switch in the GRAPPLE CLOSE position. The pressure that is indicated on the pressure gauge should be 21500 kPa (3100 psi).
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Illustration 8 g00805815
Grapple Control Switch
- If the pressure setting is not correct, release the toggle switch. Remove the acorn nut from signal limiter valve (4) with a 13 mm wrench. Remove the grommet. Loosen the locknut for the adjustment screw with the 161-8958 Wrench .
- Turn the adjustment screw with an allen wrench. Tighten the locknut. Perform Step 13.a again in order to check the new pressure setting.
- Install the grommet and the acorn nut after the correct pressure setting is achieved.
- Grapple Open:
- Slowly move the toggle switch on the right implement joystick to the GRAPPLE OPEN position. Allow the grapple to fully open. Hold the toggle switch in the GRAPPLE OPEN position. The pressure that is indicated on the pressure gauge should be 12000 kPa (1750 psi).
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Grapple Control Switch
- If the pressure setting is not correct, release the toggle switch. Remove the acorn nut from signal limiter valve (5) with a 13 mm wrench. Remove the grommet. Loosen the locknut for the adjustment screw with the 161-8958 Wrench .
- Turn the adjustment screw with an allen wrench. Tighten the locknut. Perform Step 14.a again in order to check the new pressure setting.
- Install the grommet and the acorn nut after the correct pressure setting is achieved.
- Remove the pressure gauge.