631K and 637K Wheel Tractor-Scraper Systems Relief Valve (Apron) - Test and Adjust Caterpillar

Specifications

Introduction

This test and adjust is checking the relief valve setting on the apron. The Implement relief pressure is the difference between the pump supply pressure and the implement tank return pressure.

Required Tools

Illustration 1	g01623868

Machine Preparation

1. Move the machine to a smooth, horizontal location. Move the machine away from other operating machines and away from personnel. Place the transmission direction control switch in the NEUTRAL position. Engage the parking brake. Lower the bowl to the ground. Retract the ejector cylinder and disengage the cushion hitch. Shut off the engine and turn the engine start switch to the ON position. Place chocks in front of the wheels and behind the wheels.
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   NOTICE
   Perform the following steps prior to the pilot pressure diminishing. The procedure should be performed no more than 1/2 hour after the engine has been shut off.

2. Move the control levers through the full range of travel. This movement of the levers will relieve any pressure that may be present in the hydraulic system. Turn the engine start switch to the OFF position.

3. Slowly loosen the filler cap for the hydraulic oil tank to release the pressure.
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   Illustration 2	g06217811
   View of the implement control valve supply and return lines. (1) Implement return pressure tap (2) Implement pump pressure tap

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   Illustration 3	g06217844
   View of the top and rear of the implement control valve. (3) Apron raise relief valve (4) Apron lower relief valve

4. Remove the dust cover from pump pressure tap (1) on the implement control valve and connect tooling (B) to the test port.

5. Remove the dust cover from drain to hydraulic tank tap (2) on the hydraulic tank return line and connect tooling (B) to the test port.

Test Procedure

Apron Raise Relief Pressure

1. Connect pressure sensor to pump pressure tap (1) and drain to hydraulic tank tap (2). The relief pressure is the pressure difference between pump pressure tap (1) and drain to hydraulic tank tap (2).

2. Start the engine and bring the engine to normal operating temperature.

3. Slowly raise the apron to the FULLY RAISED position and raise the engine speed to HIGH IDLE. Then hold the joystick in the APRON RAISE position. The apron relief pressure should be 23000 ± 300 kPa (3336 ± 44 psi).

4. If the pressure setting is not correct, then adjust head end pressure relief valve (3). Loosen the lock nut that holds the adjustment screw. Turn the adjustment screw clock wise to increase the relief pressure setting. When the relief pressure is set, hold the adjustment screw and tighten the lock nut.

APRON LOWER Relief Pressure

1. Connect the pressure sensor to pump pressure tap (1) and drain to hydraulic tank tap (2). The relief pressure is the pressure difference between pump pressure tap (1) and drain to hydraulic tank tap (2).

2. Start the engine and bring the engine to normal operating temperature.

3. Slowly lower the apron to the FULL DOWN position and bring the engine to HIGH IDLE. Hold the control joystick in the APRON LOWER position. The apron lower relief pressure should be 26900 ± 300 kPa (3900 ± 44 psi).

4. If the pressure setting is not correct, then adjust head end pressure relief valve (4). Loosen the lock nut that holds the adjustment screw. Turn the adjustment screw clock wise to increase the relief pressure setting. When the relief pressure is set, hold the adjustment screw and tighten the lock nut.

Apron (Lower Line Relief Valve Pressure)

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Illustration 4	g03720964

1. Connect the pressure sensor to apron rod end pressure tap (5).

2. Start the engine and bring the engine to normal operating temperature.

3. With the bowl on the ground slowly lower the apron to the FULL DOWN position and bring the engine to LOW IDLE. Hold the control joystick in the APRON HOLD position. Then slowly raise the bowl against the apron. The rod end pressure is controlled by rod end pressure relief valve (3). The apron rod end line pressure should not exceed 28000 ± 690 kPa (4060 ± 100 psi).