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

Specification

Introduction

The main relief valve for medium pressure is located on the medium pressure control valve. The main relief valve limits the maximum pressure that the work tool can rotate at. The medium pressure control valve is located on the left side of the swing motor compartment in front of main control valve.

Illustration 1	g03626958
Relief valve (typical example) (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. Disconnect the medium pressure lines for tool rotation and install the shipping plugs on the medium pressure lines. This action will prevent oil flow to the work tool for rotation during this procedure and allow for the valve to relief.

5. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, " System Pressure - Release" for the machine.
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   Illustration 4	g03628457
   Medium pressure control valve (1) Pressure tap (delivery pressure for the auxiliary pump)

6. Attach a 34,450 kPa (5,000 psi) pressure sensor to pressure tap (1).

Test Procedure

1. Start the engine.

2. Select a work tool for tool rotation.

   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 55° ± 5°C (131° ± 9°F).
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   Illustration 5	g02292894
   Control Inputs for extension and retraction of the attachment valve for medium pressure (LJ) Left-hand joystick (RJ) Right-hand joystick (C) Thumb wheel (Forward) - "Attachment Valve Extend" (D) Thumb wheel (Backward) - "Attachment Valve Retract" (FP) Electric foot pedal (C) Pedal (Forward) - "Attachment Valve Extend" (D) Pedal (Backward) - "Attachment Valve Retract"

5. Operate the control input to extend and retract the attachment 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) for both directions of flow. Refer to Table 1 for the pressure specifications of the main relief valve.

7. Return the joystick to the NEUTRAL position.

Adjustment Procedure

Main Relief Valve

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Illustration 6	g03628900
Main relief valve for attachment control valve

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

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

3. Return the control input to the NEUTRAL position.

4. To adjust the main relief valve pressure setting, operate the control input for retraction of the attachment control valve to the FULL position and hold. Refer to Illustration 5 for the control input.

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

6. Return the control input to the NEUTRAL position.

7. The pressure readings should be within the specification. Refer to Table 1. If the pressure reading at the pressure taps is not within the specification, adjust the main relief valve.

8. In order to adjust the main relief valve, loosen the locknut on the main relief valve. Turn the adjustment screw until the pressure reading at the pressure taps is within the specification. Refer to Table 1.

   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.

9. Tighten the locknut on the main relief valve.