Procedure for the Repair of Compensator Valves in the Main Hydraulic Control Valve{5051, 5086} Caterpillar


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Procedure for the Repair of Compensator Valves in the Main Hydraulic Control Valve{5051, 5086} [REHS1040]
HYDRAULIC SYSTEM
VALVE GP-CONTROL
Procedure for the Repair of Compensator Valves in the Main Hydraulic Control Valve{5051, 5086}
1.1. Introduction
2.1. Needed Parts
3.1. Release of Hydraulic Pressure in the Hydraulic System
4.1. Rework Procedure
Excavator:
350 (S/N: 2ZL1-UP; 7RK1-UP; 8HK1-UP)
350 L (S/N: 9DK1-UP; 3ML1-UP; 9FL1-UP; 8KZ1-UP)
365B L (S/N: 4XZ1-UP; 9PZ1-UP; 9TZ1-UP; AGD1-UP)
375 (S/N: 8XG1-UP; 8WJ1-UP; 6NK1-UP)
375 L (S/N: 6RL1-UP; 9WL1-UP; 1JM1-UP)
5080 (S/N: 6XK1-UP; 8SL1-UP)

Introduction

This Special Instruction explains the procedure for repairing the main compensator valves that are located in the main hydraulic control valves for the excavators that are listed above. The procedure addresses a lack of hydraulic power complaint. The lack of hydraulic power is caused by a loss of load sensing signal pressure. The loss of load sensing signal pressure occurs between compensator valves that are worn and the main control valve.

Refer to the appropriate Parts Manual, Operation and Maintenance Manual, and Service Manual for the particular machine that is affected. These references provide safety information and information about removal, installation, disassembly, and assembly of the main hydraulic control valve.

Needed Parts

There are oversize spools and check valves that are available in the AVSpare Parts System. Refer to the table in order to cross-reference the former components and the oversize components.

Table 1
Part Name     Former Part Number     Oversize Part Number    
Spool     9T-9828     177-2230    
Check Valve     9T-8305     177-2231    

The diameter for the oversize component is 45.45 mm (1.789 inch). This dimension represents an increase of 1.00 mm (0.039 inch) over the former components. The main hydraulic control valve and the oversize components must be machined and polished in order to provide the correct fit between the components and the control valve.

Release of Hydraulic Pressure in the Hydraulic System

------ WARNING! ------

Personal injury can result from hydraulic oil pressure and hot oil.

Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.

Make sure all of the work tools have been lowered to the ground, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

----------------------


NOTICE

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 Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on AVSpare products.

Dispose of all fluids according to local regulations and mandates.


Perform the following steps in order to release the hydraulic pressure from a single hydraulic circuit of the main hydraulic system.

  1. Position the machine on level ground.



    Illustration 1g00666865

  1. Fully retract the stick cylinder rod. Adjust the position of the bucket so that the bucket is parallel to the ground. Lower the boom until the bucket is flat on the ground. Refer to Illustration 1.

  1. Shut off the engine.

  1. Turn the engine start switch to the ON position without starting the engine.

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

  1. Move only the joysticks or the pedals of the hydraulic circuit that requires service to the FULL STROKE positions. This will release the high pressure only in that single hydraulic circuit. This will also release any pressure that might be present in the pilot hydraulic circuit.

    Note: If the desired hydraulic circuit that requires service requires the activation of a switch for operation, activate the necessary switches for the operation of the hydraulic circuit.

  1. Place the hydraulic activation control lever in the LOCKED position.

  1. Turn the engine start switch to the OFF position.

  1. Slowly loosen the fill/vent plug on the hydraulic tank and release the pressure from the hydraulic tank. Leave the fill/vent plug loose for a minimum of 45 seconds. This will release the pressure that may be present in the return hydraulic circuit.

  1. Tighten the fill/vent plug on the hydraulic tank to the specified torque.

  1. The pressure in the single hydraulic circuit that requires service is now released and lines and components can be disconnected or removed from that hydraulic circuit.

Rework Procedure

Refer to the Disassembly and Assembly section of the Service Manual for the specific machine that will be reworked before the hydraulic circuit is disassembled.

  1. Remove the main hydraulic control valve from the machine.



    Illustration 2g00810884

    Section view of Main Hydraulic Control Valve

    (1) Plug

    (2) Seal

    (3) Spring

    (4) Compensator valve

    (5) Spring

    (6) Check valve

    (A) Attachment valve

    (B) Bucket valve

    (C) Stick valve

    Note: Tighten plug (1) to a torque of 6 ± 2 N·m (53 ± 18 lb in).

    Note: The fit for valve (4) or valve (6) to the internal diameter of the body must be 0.015 to 0.020 mm (0.0006 to 0.0008 inch) loose.

  1. Separate the control valve bank which contains the control function that is being reworked.

  1. Remove the cover for the compensator valves. Disassemble the individual components for the control valve compensator spool that is being reworked.

  1. Measure the diameter of the bores for the compensator valve (4) and the check valve (6) in the body with a suitable gauge in order to determine the amount of wear. Measure the bore with the worst wear.



    Illustration 3g01273653

    Section view of the valve body that is ground oversize

    (D) The finished diameter should be 45.45 mm (1.789 inch) plus 0.20 mm (0.008 inch) minus 0.10 mm (0.004 inch).

    (E) The chamfer is 0.8 ± 0.5 mm (0.03 ± 0.02 inch) by 45 degrees.

    (F) The maximum chamfer that can be allowed is 1.00 mm (0.039 inch) by 45 degrees.

    (G) The reference diameter is 44.0 ± 0.8 mm (1.73 ± 0.03 inch).

    (H) The reference dimension is 101.5 ± 0.3 mm (3.99 ± 0.01 inch).

    (J) The reference dimension is 50.5 ± 0.3 mm (1.99 ± 0.01 inch).

    (K) The reference dimension is 152 mm (5.98 inch).

    Note: The surface finish of Diameter (D) must be 0.8 micrometers (32 microinch). There shall be no tool marks.

    Note: The surface of Diameter (D) must be concentric within 0.003 mm (0.0001 inch) and flat within 0.005 mm (0.0002 inch).

    Note: A maximum taper of 0.005 mm (0.0002 inch) is allowed on Diameter (D) that includes the two lands.

  1. Compare the measurement of the bore to the oversize diameter that is specified in Illustration 3. There must be enough material in the bore in order to resize the bore to the correct dimension. If there is sufficient material, machine the bore diameter to a range of 45.45 + 0.20 mm (1.7894 + 0.008 inch) to 45.45 - 0.10 mm (1.7894 - 0.004 inch). See Illustration 3. The final finish for the surface of the bores should be a minimum of 0.80 micrometer (32 micro inch).

  1. Measure the actual diameter of the oversize compensator valve (4) and the check valve (6) with a suitable micrometer that will achieve a measured accuracy of 0.0010 mm (0.00004 inch). Measure the diameter of the finished bore with the same accuracy as the compensator valve.

  1. The compensator valve (4) and the check valve (6) must have a final diameter that is 0.015 to 0.020 mm (0.0006 to 0.0008 inch) smaller than the final bore diameter. This fit is defined as a loose fit. Finish grind or lap the compensator valve and the check valve in order to obtain the correct loose fit between the valve and the bore. The final surface finish for the valves should be a minimum of 0.80 micrometer (32 micro inch).

  1. Repeat Steps 4 through 7 for worn bores in other compensator valves.

  1. Thoroughly clean any chips and grinding material out of the body before the parts are assembled.

  1. Assemble the parts for the compensator valve into the valve bank. Install the cover. Connect the two valve banks. Install the main control valve on the excavator with the instructions in the Disassembly and Assembly Manual.

  1. Test and adjust all pressures on the excavator according to the specifications that are given.

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