IT28G Integrated Toolcarrier and 928G Wheel Loader Hydraulic System Caterpillar

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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.

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Personal injury or death can result from improper accumulator charging. Dry Nitrogen is the only gas approved for use in the accumulator. Charging the accumulator with oxygen will cause an explosion. This danger will not happen if nitrogen cylinders with standard CGA (Compressed Gas Association, Inc.) Number 580 connections are used. When ordering nitrogen gas, be sure that the cylinders are equipped with CGA Number 580 connections. Do not use color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders Never use an adapter to connect your nitrogen charging group to a valve outlet used on both nitrogen, oxygen, or other gas cylinders. BE SURE YOU USE DRY NITROGEN (99.8% purity).

Pilot Accumulator

The following procedure can be used in order to test the pilot accumulator. The pilot accumulator maintains pressure in the pilot hydraulic system. The accumulator allows you to lower the boom, and the work tools with a stopped engine.

When you test or you charge the pilot accumulator, the pressure in the pilot hydraulic system must be released. The temperature of the nitrogen gas must also be taken into account. The pressure and volume of nitrogen gas varies with temperature.

Discharging the Accumulator

1. Ensure that the oil in the hydraulic system is at normal operating temperature. Park the machine on a smooth, level surface.

2. Install the steering frame lock. Block the wheels. Stop the engine.

3. Turn the engine start switch to the ON position. Move the joystick, the third function lever and the fourth function control through the full range of travel.

   Note: Moving the joystick and moving the levers will release the pressure in the pilot hydraulic system.

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Illustration 1	g00902710

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Illustration 2	g00902707

4. Remove the access panels (A) under the platform on the right side of the machine in order to access the pilot accumulator (B) .

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Illustration 3	g00282181

5. Remove guard (1) which protects nitrogen charging valve (2) .

6. Remove the protective cap on nitrogen charging valve (2) .

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Illustration 4	g00282185
(3) Nipple. (4) Coupling assembly. (5) Pressure gauge. (6) Hose assembly. (7) Coupling assembly. (8) Nipple. (9) Valve. (10) Pressure gauge. (11) Regulator assembly. (12) Pressure regulating screw. (13) Chuck for the nitrogen cylinder valve. (14) Valve handle. (15) Nitrogen charging chuck. (16) Hose assembly. (17) Tee.

7. Identify the correct nitrogen charging chuck.

   Note: For a nitrogen charging valve with a .305 inch -32 THD, use a 1S-8938 Nitrogen Charging Chuck and a 1U-5551 Extension Assembly. For a nitrogen charging valve with a .482 inch -26 THD, use a 7S-5106 Nitrogen Charging Chuck and a 7S-5439 Extension Assembly .

8. Attach hose assembly (16) to nitrogen charging chuck (15) .

9. Turn the valve handle (14) on nitrogen charging chuck (15) all the way in the counterclockwise direction. This will ensure that nitrogen charging valve (2) will not be opened when nitrogen charging chuck (15) is attached to the nitrogen charging valve.

10. Attach nitrogen charging chuck (15) and hose assembly (16) to nitrogen charging valve (2) .

11. Attach nitrogen charging chuck (15) and hose assembly (16) to nitrogen charging valve (2) .

12. Place the open end of hose assembly (16) away from the work area and away from other personnel.

13. Turn valve handle (14) on nitrogen charging chuck (15) all the way in the clockwise direction in order to open nitrogen charging valve (2). This will release all of the compressed gas from the accumulator through hose assembly (16). Now, the accumulator can be removed from the machine.

14. Disconnect the hydraulic lines for servicing, as needed.

Nitrogen Charging Procedure

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Illustration 5	g00107133
Nitrogen Charging Group (1) Nipple. (2) Coupling assembly. (3) Pressure gauge. (4) Hose assembly. (5) Coupling assembly. (6) Nipple. (7) Valve. (8) Pressure gauge. (9) Regulator assembly. (10) Pressure regulating screw. (11) Chuck for the nitrogen cylinder valve. (12) Valve handle. (13) Chuck. (14) Hose assembly.

1. Ensure that valve (7) is closed. Install chuck (13) onto the pilot accumulator. Turn valve handle (12) completely in the clockwise direction.

2. If the reading on pressure gauge (8) is too high, slowly open valve (7) in order to lower the pressure. If the reading on the pressure gauge is too low, use the following procedure to charge the accumulator:

   1. Connect a hose from the nitrogen cylinder to chuck (11) .

   2. Open the valve on the nitrogen cylinder. Adjust screw (10) on regulator assembly (9) until pressure gauge (3) is at the correct charging pressure.

   3. Slowly open valve (7) and charge the accumulator. Charge the accumulator to 862 ± 35 kPa (125 ± 5 psi) at a temperature of 21 °C (70 °F). Then, close valve (7). If pressure gauge (8) and pressure gauge (3) show the same reading and the readings do not change, the accumulator has the correct charge.

      If the pressure reading on gauge (8) decreases, open valve (7) and allow more nitrogen to fill the accumulator.

      Perform this procedure until pressure gauge (8) and pressure gauge (3) show the same reading. Make sure that neither reading changes when valve (7) is closed.

3. Close valve (7). Close the valve on the nitrogen cylinder.

4. Turn valve (12) on chuck (13) outward in the counterclockwise direction. Remove the test equipment.