D6T Track-Type Tractor Systems Pressure Reducing Valve - Test and Adjust Caterpillar


Pressure Reducing Valve - Test and Adjust
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D6T Track-Type Tractor Systems [M0064234]
HYDRAULIC SYSTEM
VALVE GP
D6T Track-Type Tractor Systems Pressure Reducing Valve - Test and Adjust
1.1. Specifications
2.1. Introduction
3.1. Required Tools
4.1. Test Preparation - Pressure Reducing Valve
5.1. Test Procedure - Pressure Reducing Valve
6.1. Adjustment Procedure - Pressure Reducing Valve
7.1. Test Procedure - Relief Valve

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

Hydraulic oil pressure can remain in the hydraulic system on this machine after the engine and pump have been stopped. Serious injury can result if this pressure is not released before any service is done on the hydraulic systems. In order to prevent possible injury, release the hydraulic system pressure before working on any fitting, hose, or hydraulic component.

Lower all attachments to the ground before service is started. If the hydraulic system must be serviced, tested, or adjusted with the attachment in the raised position, the attachments and lift cylinders must be supported properly.

Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.


Specifications

Table 1
D6T Pressure Reducing Valve 
Date  Equipment ID Code 
Valve Tested  Recommended  Actual 
Pressure Reducing Valve at High Idle  3275 ± 175 kPa (475 ± 25 psi)   
Relief Valve  6485 ± 345 kPa (940 ± 50 psi ) (1)   
(1) This pressure is measured at a flow rate of 1 L/min (0.26 US gpm).


Illustration 1g03664120

Table 2
D6T Torque Specifications 
Item  Torque 
Relief Valve (3)  40 ± 4 N·m (30± 3 lb ft) 
Locknut on Pressure Reducing Valve (4)  12 N·m (106 lb in) 

Introduction

The pressure reducing valve reduces the pressure of a portion of the discharge oil from the implement pump for use in the pilot system.

The pressure in the pilot system controls the actuation of the implements. Low pilot pressure produces poor response in the implement control levers. High pilot pressure produces extreme sensitivity in the implement control levers.

The following test procedure will verify whether the pressure setting for the pilot pressure is within the specified limit. The following adjustment procedure will explain the procedure for adjusting the pilot pressure.

Pilot pressure is controlled by the pressure reducing valve, which is located in the pilot manifold.

Required Tools



Illustration 2g02571852
Tooling (A)

Table 3
Tool  Item  Part Number  Description  Qty 
198-4240  Digital Pressure Indicator Gp   
  A1  198-4234  Digital Pressure Indicator 
A2 198-4237  Pressure Sensor (0 to 500 psi) 
A2 198-4239  Pressure Sensor (0 to 6000 psi) 
A3 198-4236  Adapter Cable As 
1U-9358  Test Block Manifold 

Test Preparation - Pressure Reducing Valve

  1. Move the machine to a smooth horizontal location.

  2. Lower all of the implements.

  3. Shut off the engine.

  4. Turn the key to the ON position. Make sure that the implement lockout switch is turned to the UNLOCKED position. Move the implement control levers to all positions several times in order to release any pressure in the hydraulic system.

    Note: The pressure reducing valve is located behind an access door on the right fender that is next to the operator station.



    Illustration 3g03664125
    (1) Accumulator
    (2) Manifold and reducing valve
    (CP) Pilot supply pressure (pressure after pressure reducing valve)
    (3) Relief valve
    (4) Pressure reducing valve

  5. Attach tooling (A) to pressure tap (CP) for pilot pressure on the right fender.

Test Procedure - Pressure Reducing Valve

Note: Low pilot pressure produces poor response at the pilot control levers. High pilot pressure produces extreme sensitivity at the pilot control levers.

  1. Operate the engine at HIGH IDLE and exercise the implement hydraulics. The pilot pressure should be a maximum of 3275 ± 175 kPa (475 ± 25 psi).

  2. If the pilot pressure is not correct, refer to "Adjustment Procedure - Pressure Reducing Valve" in order to adjust the pilot pressure.

Adjustment Procedure - Pressure Reducing Valve

Reference: See "Test Preparation - Pressure Reducing Valve" in order to prepare the machine for adjustment.

  1. Loosen the locknut on the adjustment screw of pressure reducing valve (4). Turn the adjustment screw until the pilot pressure is correct.

    Note: One turn adjusts the pilot pressure by 1380 kPa (200 psi).

  2. Tighten the locknut on the adjustment screw to a torque of 12 N·m (106 lb in).

Test Procedure - Relief Valve

The pressure reducing valve is located behind an access door on the right fender of the operator station.



Illustration 4g03664125
(1) Accumulator
(2) Manifold and reducing valve
(CP) Pilot supply pressure (pressure after pressure reducing valve)
(3) Relief valve
(4) Pressure reducing valve

The relief valve can be removed for a bench test, if necessary. The relief valve is a nonadjustable valve. Test the relief valve in order to ensure proper operation.

  1. Remove relief valve (3).

  2. Install the relief valve (3) in 1U-9358 Test Block Manifold (D) in order to test the relief valve on the test bench. Tighten the relief valve to a torque of 40 ± 4 N·m (30 ± 3 lb ft).

  3. The relief valve should open at 6485 ± 345 kPa (940 ± 50 psi) with the oil flow rate at 1.0 L/min (0.26 US gpm). If the relief valve pressure is correct, then go to Step 4. If the relief valve pressure is not correct, the valve must be replaced.

  4. Install the relief valve in the machine. Tighten relief valve (3) to a torque of 40 ± 4 N·m (30 ± 3 lb ft).

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