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

Introduction

The line relief valves are located between each cylinder and the respective control valve. The line relief valve limits the overload pressures that can be created in the implement cylinders. The line relief valves are located on the left side and right side of the main control valve. The line relief valves are accessible from above the main control valve and below the machine after removal of the access plate.

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	g03627036
   Pump compartment (1) Pressure tap (delivery pressure for drive pump) (2) Pressure tap (delivery pressure for idler pump) (3) Pressure tap (power shift pressure)

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

6. Connect a 34,450 kPa (5,000 psi) pressure sensor to pressure tap (3) to monitor power shift pressure.

7. Start the engine.

8. 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.

9. Increase the hydraulic oil temperature to 50° ± 10°C (122° ± 50°F).

Temporary Setting of the Main Relief Valve

1. A temporary setting of the main relief valve is required before any line relief valves can be adjusted.

2. Move the joystick for the boom until the boom is at the full BOOM RAISE position (full extension of boom cylinder).

3. Check the main relief valve pressure setting at pressure tap (1) or pressure tap (2).

4. Be sure that the main relief valve pressure is set at the pressure specification. Refer to Table 2.

   Note: Always make final pressure adjustments on pressure rise.

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   Illustration 5	g03626980
   Main relief valve (standard) (A) Adjustment screw (L) Locknut

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   Illustration 6	g03626997
   Main relief valve (heavy lift) (A) Adjustment screw (L) Locknut

5. Loosen the locknut. Turn the adjustment screw clockwise for one half turn. Tighten the locknut.

6. Reset main relief valve pressure setting to the normal operating condition after the completion of the line relief test and adjust. Refer to Testing and Adjusting, "Relief Valve (Main) - Test and Adjust".

Test Procedure

1. Start the engine.

2. Select a work tool to meet the following conditions.

   • Two-way flow

   • Variable relief valve pressure set at the default specifications of 40,000 kPa.

   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).

5. Enter the service mode.

   1. Input the password "9992".

   2. Select "Override Parameters".
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   Illustration 7	g02319174

6. Highlight "Power Shift Pressure" and press the OK key. Set the power shift pressure to the specification. Refer to Table 2 for the pressure specification. Confirm the power shift pressure setting at pressure tap (3).
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   Illustration 8	g02292583
   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)

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   Illustration 9	g02292257
   Control Inputs for attachment control valve retracted. (LJ) Left-hand joystick (RJ) Right-hand joystick (B) Thumb wheel (Backward) (FP) Electric foot pedal (B) Pedal (Backward)

7. 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.

8. 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.

9. Return the joystick to the NEUTRAL position.

Adjustment Procedure

Attachment Control Valves Extend

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Illustration 10	g03627416
Line relief valve for 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 8 for the control input.

2. Check the pressure reading at pressure tap (1).

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 pressure tap (2) 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 pressure tap (2) 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.

Attachment Control Valves Retract

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Illustration 11	g03628398
Line relief valve for the retraction of the attachment control valves

1. To adjust the line relief valve pressure setting, operate the control input for retraction of the attachment control valves to the FULL position and hold. Refer to Illustration 9 for the control input.

2. Check the pressure reading at pressure tap (1).

3. Return the control input to the NEUTRAL position.

4. The pressure reading should be to the specification. Refer to Table 2. If the pressure reading at pressure tap (2) 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 pressure tap (2) 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