349E, 349F and 352F Excavators and 349E MHPU Mobile Hydraulic Power Unit Tool Control System Caterpillar

Introduction

The tool relief valve is located between work tool and attachment control valve. The relief valve limits the maximum pressure that the work tool can operate at. The relief valve is located on the left side of the swing motor compartment in front of main control valve.

Illustration 1	g03626958
Line relief valve (L) Locknut (A) Adjustment screw

Required Tools

Illustration 2	g01623868
Tooling group "B" 198-4240 Digital Pressure Indicator Gp

Machine Preparation

1. The following procedures must be completed before performing the calibration.

   • Set the pilot pressure to the specifications in Testing and Adjusting, "Relief Valve (Pilot) - Test and Adjust" for the machine.

   • Calibrate the power shift pressure. Refer to Testing and Adjusting, "Solenoid Valve (Proportional Reducing) - Calibrate (Power Shift Pressure)" for the machine.

   • Calibrate the attachment valves. Refer to Testing and Adjusting, "Solenoid Valve (Proportional Reducing) - Calibrate (Attachment Valves)" for the Tool Control System.

   • Calibrate the flow limit valves. Refer to Testing and Adjusting, "Solenoid Valve (Proportional Reducing) - Calibrate (Flow Limit Valves)" for the Tool Control System.

2. Position the machine on level ground and stop the engine.
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   Illustration 3	g03602396
   Stop valves for high-pressure oil delivery to the work tool (typical example)

3. Close the stop valves that are mounted on each side of the stick in order to prevent oil flow to the work tool during this procedure.

4. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "System Pressure - Release" for the machine.
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   Illustration 4	g03625037
   Pump compartment (1) Pressure tap (delivery pressure for drive pump) (2) Pressure tap (delivery pressure for idler pump)

5. Attach both 41,368 kPa (6,000 psi) pressure sensors to pressure tap (1) and pressure tap (2).

Test Procedure

1. Start the engine.

2. Select a work tool one pump flow or two pump flow. Refer to Table 2 for the specifications for each setting.

   Refer to Testing and Adjusting, "Work Tool - Select" for the Tool Control System.

3. Place the machine controls at the following settings: engine speed dial "10" and AEC switch OFF. Refer to Testing and Adjusting, "Engine Performance - Test (Engine Speed)" for engine rpm settings.

4. Increase the hydraulic oil temperature to 50° ± 10°C (122° ± 18°F).
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   Illustration 5	g02283934
   Control Inputs for attachment control valves extended. (LJ) Left-hand joystick (RJ) Right-hand joystick (A) Thumb wheel (Forward) (A) Switch (FP) Electric foot pedal (A) Pedal (Forward) (FS) Foot switch (A) Foot switch (ON)

5. Operate the control input in the appropriate direction in order to relieve the valve.

   Note: A continuous relief of the valve for more than 10 seconds is not allowed.

6. Check the main relief valve pressure setting at pressure tap (1) or pressure tap (2). Refer to Table 2 for the pressure specifications of the line relief valves.

7. Return the joystick to the NEUTRAL position.

Adjustment Procedure

Attachment Control Valves Extend

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Illustration 6	g03618842
Line relief valve for the extension of the attachment control valves

1. To adjust the line relief valve pressure setting, operate the control input for extension of the attachment control valves to the FULL position and hold. Refer to Illustration 5 for the control input.

2. Check the pressure reading at pressure tap (1) or (2) depending on pump flow setting.

3. Return the control input to the NEUTRAL position.

4. The pressure reading should be within the specification. Refer to Table 2. If the pressure reading at the pressure taps is not within the specification, adjust the line relief valve.

5. In order to adjust the line relief valve, loosen the locknut on the line relief valve. Turn the adjustment screw until the pressure reading at the pressure taps is within the specification. Refer to Table 2.

   Note: Turn the adjustment screw clockwise in order to increase the pressure. Turn the adjustment screw counterclockwise in order to decrease the pressure.

   Note: Always make final pressure adjustment on pressure rise.

6. Tighten the locknut on the line relief valve.

Worksheet