349F and 352F Excavators Hydraulic System Relief Valve (Line) - Test and Adjust Caterpillar

Specification

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 accessible from above the main control valve and below the machine after removal of the access plate.

Required Tools

Illustration 1	g02571852
Tooling (A) 198-4240 Digital Pressure Indicator Gp

Machine Preparation

1. Position the machine on level ground and stop the engine.

2. Release the pressure in the hydraulic system. Refer to Testing and Adjusting, "System Pressure - Release".

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Illustration 2	g03369540
Pump compartment (1) Pressure tap (delivery pressure for drive pump) (2) Pressure tap (delivery pressure for idler pump)

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

Test Procedure

Note: A temporary setting of the main relief valve is required before any line relief valves can be adjusted. Refer to Table 3 for temporary main relief setting for the function being tested.

Note: Pressure values in Table 4 are approximate values. Use a pressure gauge for adjustments.

Bucket Cylinder Head End, Bucket Cylinder Rod End, Boom Cylinder Rod End, and Stick Cylinder Head End

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

Illustration 3	g03369529
Main control valve (3) Main relief valve (4) Line relief valve for the stick cylinder head end (5) Line relief valve for the stick cylinder rod end (6) Line relief valve for the bucket cylinder head end (7) Line relief valve for the bucket cylinder rod end (8) Line relief valve for the boom cylinder rod end (9) Line relief valve for the boom cylinder head end

1. Start the engine.

2. Place the hydraulic activation control lever in the UNLOCKED position.

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).

5. Move the joystick for the stick until the stick is at the full STICK OUT position (full retraction of the stick cylinder).

6. Check the main relief valve pressure setting at pressure tap (1) or pressure tap (2) . The main relief valve pressure setting should be 35000 ± 500 kPa (5076 ± 73 psi).

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Illustration 4	g02142898
Main relief valve (standard) (A) Adjustment screw (L) Locknut

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Illustration 5	g02143255
Main relief valve (heavy lift) (A) Adjustment screw (L) Locknut

7. Loosen the locknut. Set the main relief pressure to 37000 ± 500 kPa (5366 ± 73 psi). Tighten the locknut.

   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 adjustments on pressure rise.

8. Verify the temporary main relief pressure setting with a second function. Move the joystick for the boom until the boom is at full BOOM RAISE position (full extension of the boom cylinder). The main relief pressure should be 37000 ± 500 kPa (5366 ± 73 psi).

9. Mark the original position of the line relief for the bucket cylinder head end (6) .

10. Move the joystick for the bucket until the bucket is at the full BUCKET CLOSE position (full extension of bucket cylinder).

11. Check the pressure setting of the line relief for the bucket cylinder head end (6) .

12. Loosen the locknut of the bucket line relief valve. Turn adjustment screw of the bucket line relief valve until the pressure reading pressure tap (1) is 35000 kPa (5076 psi).

13. Move the joystick for the bucket until the bucket is at the full BUCKET CLOSE position (full extension of bucket cylinder).

14. Check the pressure setting of the line relief for the bucket cylinder head end (6) .

15. Turn the adjustment screw of the bucket line relief valve until the pressure reading at pressure tap (1) is 37000 ± 500 kPa (5366 ± 73 psi).

    Note: Always make final pressure adjustments on the pressure rise.

    Note: In order to prevent over setting, the adjustment should be stopped immediately after the pressure becomes within specification.

16. Repeat Step 9 to Step 15 for the following line relief valves:
    • Line relief valve for bucket cylinder rod end (7)

    • Line relief valve for stick cylinder head end (4)

    • Line relief valve for boom cylinder rod end (8)

17. Reset main relief valve pressure setting to the initial main relief valve setting after the completion of the line relief test and adjust.

Boom Cylinder Head End and Stick Cylinder Rod End

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

Illustration 6	g03369529
Main control valve (3) Main relief valve (4) Line relief valve for the stick cylinder head end (5) Line relief valve for the stick cylinder rod end (6) Line relief valve for the bucket cylinder head end (7) Line relief valve for the bucket cylinder rod end (8) Line relief valve for the boom cylinder rod end (9) Line relief valve for the boom cylinder head end

1. Mark the original position of the line relief valve for the stick cylinder rod end (5) .

2. Loosen the locknut for line relief valve (5) . Turn the adjustment screw clockwise by one quarter turn. Tighten the locknut.

3. Start the engine.

4. Place the hydraulic activation control lever in the UNLOCKED position.

5. 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.

6. Increase the hydraulic oil temperature to 55° ± 5°C (131° ± 9°F).

7. Move the joystick for the stick until the stick is at the full STICK OUT position (full retraction of the stick cylinder).

8. Check the main relief valve pressure setting at pressure tap (1) or pressure tap (2) . The main relief valve pressure setting should be 35000 ± 500 kPa (5076 ± 73 psi).

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Illustration 7	g02142898
Main relief valve (standard) (A) Adjustment screw (L) Locknut

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Illustration 8	g02143255
Main relief valve (heavy lift) (A) Adjustment screw (L) Locknut

9. Loosen the locknut. Set the main relief pressure to 40000 ± 500 kPa (5802 ± 73 psi). Tighten the locknut.

   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 adjustments on pressure rise.

10. Mark the original position of the line relief valve for the boom cylinder head end (9) .

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

12. Check the pressure setting of the line relief valve for the boom cylinder head end (9) .

13. Loosen the locknut of the boom line relief valve. Turn adjustment screw of the boom line relief valve until the pressure reading at pressure tap (1) is 38000 kPa (5512 psi).

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

15. Check the pressure setting of the line relief valve for the boom cylinder head end (9) .

16. Turn the adjustment screw of the boom line relief valve until the pressure reading at pressure tap (1) is 40000 ± 500 kPa (5802 ± 73 psi).

    Note: Always make final pressure adjustments on the pressure rise.

    Note: In order to prevent over setting, the adjustment should be stopped immediately after the pressure becomes within specification.

17. Move the joystick for the stick until the stick is at the full STICK OUT position (full retraction of stick cylinder).

18. Check the pressure setting of the line relief for the stick cylinder rod end (5) .

19. Loosen the locknut for the stick line relief valve (5) . Turn adjustment screw of the stick line relief valve counterclockwise until the pressure reading at pressure tap (2) is 38000 kPa (5512 psi).

20. Move the joystick for the stick until the stick is at the full STICK OUT position (full retraction of stick cylinder).

21. Check the pressure setting of the line relief for the stick cylinder rod end (5) .

22. Turn the adjustment screw of the stick line relief valve until the pressure reading at pressure tap (2) is 40000 ± 500 kPa (5802 ± 73 psi).

    Note: Always make final pressure adjustments on the pressure rise.

    Note: In order to prevent over setting, the adjustment should be stopped immediately after the pressure becomes within specification.

23. Reset main relief valve pressure setting to the initial main relief valve setting after the completion of the line relief test and adjust.

Adjustment Procedure

Note: The following adjustment procedure is similar for all functions.

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Illustration 9	g02068598
Line relief valve (L) Locknut (A) Adjustment screw

1. In order to adjust the line relief valve, loosen the locknut on the line relief valve. Turn the adjustment screw until the pressure reading 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.

2. Tighten the locknut on the line relief valve.