789C Off-Highway Truck Steering System Steering Accumulator - Test and Charge Caterpillar

Show/hide table

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 gas 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).

Do not use an adapter to connect the nitrogen charging equipment to a valve that can be used on oxygen cylinders or gas cylinders. Use dry nitrogen.

Check that the engine has not been running for at least five minutes. This will allow the oil level in the steering accumulators to decrease. The accumulator bladder must be on the bottom of the cylinder. This will ensure that the pressure of the nitrogen charge is correct.

The steering accumulator has a dry charge of 5515 ± 345 kPa (800 ± 50 psi).

Checking the Nitrogen Charge

Illustration 1	g00834546
Nitrogen charging group (Tool (A)) (1) 162-4147 Hose As (2) 8S-4600 Fitting (3) 8S-1506 Coupling (4) 162-4146 Regulator (5) 1S-8938 Chuck (6) 7S-5106 Chuck (7) 8T-0859 Pressure Gauge (8) 8S-4599 Coupling (9) 2S-5244 Fitting (10) 1S-8937 Needle Valve (11) 2D-7325 Pipe Tee (12) 1S-8941 Hose As

1. Remove the cap from the top of the accumulator. Install Tool (B) on the accumulator valve.

2. Install chuck (5) on Tool (B). If the chuck does not fit properly, use Tool (B).

   Note: Do not connect the hose to valve (10). Make sure that valve (10) is closed.

3. Turn the valve on chuck (5) clockwise.

4. Use 16000 kPa (2321 psi) pressure gauge (7) to check the nitrogen charge in the accumulator.
   Show/hide table

   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, PERJ1017, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products. Dispose of all fluids according to local regulations and mandates.

5. The pressure on the gauge must be within the tolerances that are listed in Table 2.

6. If the pressure reading on the gauge is too high, lower the pressure by slowly opening valve (10).

7. If the pressure reading on the gauge is too low, charge the accumulator.

Charging the Accumulator

Show/hide table

Illustration 2	g00912484
(13) Accumulator (14) Bladder (15) Poppet

Show/hide table

NOTICE
Charging the accumulator too rapidly after rebuild can cause bladder (14) to rupture. Set the regulator to 69 kPa (10 psi).

Note: Before you tighten the stem nut, allow the bladder to precharge slowly. The precharge for bladder (14) is 69 kPa (10 psi). Tighten the stem nut.

1. Close valve (10).

2. Connect the hose from valve (10) to regulator (7). The hose is part of Tool (A).

3. Open the valve on the nitrogen cylinder. Adjust the screw on regulator (4) until the gauge on regulator (4) is at the pressure that will charge the accumulator. Use Table 2 as a reference for the correct charging pressure.

4. Open valve (10) and charge the accumulator.

5. When the pressure reading on gauge (7) and the pressure reading on the gauge on regulator (4) are identical, shut valve (10). Allow a waiting period of ten minutes for the temperature of the nitrogen inside the accumulator to stabilize.

6. If there is a decrease in pressure on gauge on regulator (4), open valve (10). This allows more nitrogen to enter the accumulator.

7. Repeat Steps 5 and 6 until the following items occur:

   • Pressure readings of gauges on regulator (4) and on gauge (7) are identical.

   • Pressure readings do not change.

8. Close the valve on the nitrogen cylinder.

9. Turn the valve on chuck (5) counterclockwise.

10. Remove the test equipment.
    Show/hide table

    Illustration 3	g00834547
    This is a typical view of the top of an accumulator. (C) Seal (D) Cap

11. Inspect the seal (C) before the cap (D) is installed.

    Note: Replace the seal (B) if the seal is damaged.

Charging a Rebuilt Accumulator

Remove all nitrogen from the end of the accumulator.

After the accumulator is installed on the machine, use the following procedure to charge the accumulator:

1. Use the same equipment that was used to check the nitrogen charge in the accumulator.

2. Connect regulator (4) of Tool (A) to the nitrogen cylinder.

3. Turn the screw on regulator (4) counterclockwise in order to set the pressure to zero.

4. Turn valve (10) clockwise in order to close the valve.
   Show/hide table

   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, PERJ1017, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products. Dispose of all fluids according to local regulations and mandates.

5. Attach chuck (5) to the stem of the gas valve on the accumulator by turning the swivel on the chuck clockwise. Tighten chuck (5) until the chuck is finger tight. Tighten chuck (5) to an additional one quarter turn in order to seat the seal.

   Note: To prevent damage to the valve core for the accumulator, ensure that the tee handle on the chuck is turned completely counterclockwise before the chuck is installed on the valve stem for the accumulator. Do not force the chuck.

6. Connect the hose from valve (10) to regulator (4). The hose is part of Tool (A).

7. Turn the knob on the valve for the nitrogen cylinder clockwise in order to open the valve. The pressure gauge on the pressure regulator will show the pressure in the nitrogen cylinder. The pressure gauge on regulator (4) should show zero.

8. Turn the tee handle on the chuck clockwise until resistance is felt in order to unseat the valve core on the accumulator. Do not force the chuck.

9. Turn the screw on regulator (4) counterclockwise until the indicator needle on the pressure gauge on regulator (4) moves from zero.

10. Crack valve (10) in order to slowly fill the bladder inside the accumulator. Allow the bladder to expand slowly in order to completely fill the inside of the accumulator cylinder.

11. When the pressure reading on pressure gauge (7) and the pressure reading on regulator (4) are equal, shut valve (10).

12. Adjust the screw on regulator (4) until the pressure gauge on regulator (4) is at the pressure that will charge the accumulator. Use Table 2 as a reference for the correct charging pressure.

13. Open valve (10) in order to charge the steering accumulator.

14. Adjust the valves until the pressure reading on gauge (7) and the pressure reading on the gauge on regulator (4) show the correct pressure. Allow a waiting period of ten minutes for the temperature of the nitrogen inside the accumulator to stabilize. If the nitrogen pressure charge is low, adjust the screw on regulator (4) counterclockwise in order to increase the charge pressure.

15. If there is a decrease in pressure on pressure gauge (7), open valve (10). This will allow more nitrogen to enter the steering accumulator.

16. Repeat Step 5 and Step 6 until the following conditions occur.

    • Gauge (7) and the gauge on regulator (4) show equal pressure.

    • Pressure readings do not change.

17. Close the valve on the nitrogen cylinder.

18. Turn the valve handle on chuck (5) counterclockwise or turn the valve handle on Tool (B) counterclockwise.

19. Remove the test equipment.
    Show/hide table

    Illustration 4	g00834547
    This is a typical view of the top of an accumulator. (C) Seal (D) Cap

20. Replace seal (C) before the cap (D) is installed.

    Note: The seal (C) is part of the bladder.

Charging New or Rebuilt Accumulator

To ensure that a new accumulator bladder is not damaged during the charging process, use the following steps when you are charging a new accumulator or a rebuilt accumulator.

Before a new accumulator or a rebuilt accumulator can be installed on a machine, the accumulator needs to be allowed to warm to room temperature. Then, use the following procedure to charge the accumulator.

1. Turn the adjustment knob for the regulator pressure counterclockwise until the needle for the pressure indicator on the pressure gauge moves from 0 kPa (0 psi) to 35 kPa (5 psi).

2. Allow the bladder to expand slowly in order to begin the process of filling the inside of the accumulator cylinder.

3. When the pressure reading on the charging adapter gauge and the pressure regulator gauge are identical, close the accumulator cylinder.

4. Allow a waiting period of five minutes for the temperature of the nitrogen inside the accumulator to stabilize.

5. Turn the adjustment knob for the regulator pressure counterclockwise until the needle for the pressure indicator on the pressure gauge moves to 70 kPa (10 psi).

6. Allow the bladder to expand slowly in order to continue the process of filling the inside of the accumulator cylinder.

7. When the pressure reading on the charging adapter gauge and the pressure regulator gauge are identical, close the accumulator charging valve.

8. Allow a waiting period of five minutes for the temperature of the nitrogen inside the accumulator to stabilize.

9. Repeat Step 5 through Step 8 for 345 kPa (50 psi) and 690 kPa (100 psi).

10. Turn the adjustment knob for the regulator pressure counterclockwise until the needle for the pressure indicator on the pressure gauge moves to the required pressure level for the machine. See the machine specification for the correct pressure.

11. Allow the pressure in the bladder to reach the required pressure level.

12. When the pressure reading on the charging adapter gauge and the pressure regulator gauge are identical, close the accumulator charging valve.

13. Allow a waiting period of five minutes for the temperature of the nitrogen inside the accumulator to stabilize.

14. If there is a decrease in pressure on the gauge for the adapter, open the charging valve. Opening the charging valve will allow more nitrogen to enter the accumulator.

15. Repeat Step 12 through Step 14 until the following items occur:

    • Pressure readings of the gauge on the adapter and gauge on the regulators are identical.

    • Pressure readings do not change after the ten minute stabilizing period.

16. Close the valve on the nitrogen cylinder.

17. Remove the adapter that is for charging from the accumulator.