993K Wheel Loader Electrohydraulic System Caterpillar

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Dry nitrogen is the only gas approved for use in the accumulators. The charging of oxygen gas in an accumulator will cause an explosion. An explosion can be eliminated by using nitrogen gas cylinders with standard CGA (Compressed Gas Association, Inc.) No. 580 connectors. When nitrogen gas is ordered, make sure to order the cylinders with CGA No. 580 connectors. Do not rely on color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders. In any application, 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).

Illustration 1	g01444232
Hitch area Location of ride control accumulators

Illustration 2	g01444235
Control panel Location of ride control switch

Machine Preparation

1. Move the machine to level ground. Lower the bucket onto the ground.

2. Connect the steering frame lock link.

3. Shift the transmission to neutral. Engage the STIC steering control lever and the lever for the transmission lock.

4. Engage the parking brake.

5. Move the lift lever to the FLOAT position. Turn the ride control switch to the ON position.

6. Shut off the machine.

Discharging the Accumulator

Illustration 3	g02606538
Accumulator Valve (1) Guard. (2) Charging Valve. (A) Protective Cap.

1. Remove Guard (1) which protects the nitrogen charging valve (2) .

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

Accumulator equipped with 158-2336 Gas Valve

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Illustration 4	g02606596
158-2336 Gas Valve

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Illustration 5	g02614637
158-2336 Gas Valve

1. Hold the hex nut at location (C) of the nitrogen charging valve with one wrench. Turn the hex nut at location (B) with a second wrench in a counterclockwise direction. Loosening the nut opens the nitrogen charging valve (2) . Three turns will fully open the valve. The compressed gas will be released from the ride control accumulator. Now, the ride control accumulator can be removed from the machine.

Accumulator equipped with 222-2367 Gas Valve Assembly

Illustration 6	g02614762
222-2367 Gas Valve Assembly

Illustration 7	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) Chuck. (16) Hose assembly. (17) Tee.

1. Identify the correct nitrogen charging chuck.

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

3. Turn on the valve handle (14) of the nitrogen charging chuck (15) all the way in the counterclockwise direction.

   Note: Turning the valve handle will ensure that nitrogen charging valve (2) will not be opened when nitrogen charging chuck (15) is attached to nitrogen charging valve (2) .

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

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

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

Testing Procedure for the Accumulator Precharge Pressure

Illustration 8	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) Chuck. (16) Hose assembly. (17) Tee.

Note: Test the accumulator precharge pressure when the machine is not running and the work tool is flat on the ground. The pressure in the hydraulic system must be released. The released pressure will ensure that the accumulator piston has shifted to the oil end of the accumulator.

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

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

3. Identify the correct nitrogen charging chuck.

4. Turn the handle for valve (14) of the nitrogen charging chuck (15) all the way in the counterclockwise direction.

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

6. Attach hose assembly (16) between nitrogen charging chuck (15) and tee (17) . Install needle valve (9) on tee (17) , as shown. Install an 8T-0858 Pressure Gauge in the remaining open port on the tee. The pressure gauge is rated at 0 to 16000 kPa (0 to 2300 psi).

7. Turn the valve handle for needle valve (9) all the way in the clockwise direction. Completely turning the valve handle will ensure that the needle valve (9) is closed.

8. Open nitrogen charging valve (2)
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   Illustration 9	g02606596
   158-2336 Gas Valve

   1. Accumulators equipped with a 158-2336 Gas Valve , hold the hex nut at location (C ) of the nitrogen charging valve with one wrench. Turn the hex nut location (B) with a second wrench in a counterclockwise direction. Loosening the nut opens the nitrogen charging valve (2) . Three turns will fully open the valve.
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   Illustration 10	g02614762
   222-2367 Gas Valve Assembly

   2. Accumulators equipped with a 222-2367 Gas Valve Assembly , turn valve handle (14) in the clockwise direction in order to open accumulator valve (2) .

9. Read pressure gauge (10) in order to determine the charge pressure in the accumulator. The pressure reading should be 5500 kPa (800 psi) at 21 °C (70 °F).

   Note: If the machine has been running for some time, the ambient temperature of the accumulator may be different from the outside air temperature. Refer to Table 2 for the proper pressure.

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   Table 2

   Accumulator Precharge Pressure/Temperature Relationship for a Typical Accumulator with a Precharge of 5500 kPa (800 psi)
   Temperature	Pressure
   -7 °C (20 °F)	5000 kPa (725 psi)
   -1 °C (30 °F)	5105 kPa (740 psi)
   4 °C (40 °F)	5235 kPa (760 psi)
   10 °C (50 °F)	5340 kPa (775 psi)
   16 °C (60 °F)	5420 kPa (785 psi)
   21 °C (70 °F)	5500 kPa (800 psi)
   27 °C (80 °F)	5605 kPa (815 psi)
   32 °C (90 °F)	5735 kPa (830 psi)
   38 °C (100 °F)	5840 kPa (845 psi)
   43 °C (110 °F)	5920 kPa (860 psi)
   49 °C (120 °F)	6000 kPa (870 psi)

10. Proceed to Step 11 if the accumulator precharge pressure is within the specification.

    You will need to charge the accumulator if the pressure is not within the specification. Proceed to the "Charging Procedure" for instructions to charge the accumulator.

11. Close nitrogen charging valve (2) .
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    Illustration 11	g02606737
    158-2336 Gas Valve

    1. Accumulators equipped with a 158-2336 Gas Valve , with a wrench, tighten hex nut at location (B) of the nitrogen charging valve in a clockwise direction to close the nitrogen charging valve (2) . Tighten the hex nut at to a torque of 8.8 ± 2 N·m (6.5 ± 1.5 lb ft)
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    Illustration 12	g02614762
    222-2367 Gas Valve Assembly

    2. Accumulators equipped with a 222-2367 Gas Valve Assembly , turn valve handle (14) in a counterclockwise direction in order to close nitrogen charging valve (2) .

12. Turn on the handle for needle valve (9) in a counterclockwise direction. Turning the handle will allow the pressure in hose (16) to vent.

13. Remove Tool (A) from the machine.

14. Install the protective cap on nitrogen charging valve (2) .

15. Install guard (1) on the accumulator.

Charging Procedure

Illustration 13	g02606538
Accumulator Valve (1) Guard. (2) Charging Valve. (A) Protective Cap.

Illustration 14	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) Chuck. (16) Hose assembly. (17) Tee.

Before proceeding to the test procedure that follows, complete the procedure:

• Testing and Adjusting, "Machine Preparation for Troubleshooting"

1. Perform Step 1 through Step 9 of the "Testing Procedure for the Accumulator Precharge Pressure" for instructions on the installation of the nitrogen charging group.

2. Use Caterpillar Electronic Technician (ET) in order to turn the ride control ON.

   1. Open the software program for the ET.

   2. Select "Transmission ECM".

   3. Select "Override Parameters" from the drop-down menu that is located under "Diagnostics".

   4. Select "Change".

   5. Select "ON" for the "New Value" .

   6. Select "OK".

   7. A window will appear on the screen that will ask you if you want to change the parameter. Select "Yes".

3. Open needle valve (9) .

4. Start the engine.

5. Pull back on the lift control lever in order to raise the boom to full lift.

6. Recenter the lift control lever.

7. Pull back on the lift control lever again. Pulling back on the control lever will cause the lift circuit to reach relief pressure.

8. Close needle valve (9) .

9. Lower the boom in order to place the work tool on the ground.

10. Move the lift control lever into the FLOAT.

11. Attach the open end of hose assembly (6) to needle valve (9) by using coupling (7) and nipple (8) .

12. Attach regulator assembly (11) to a nitrogen tank.

13. Adjust pressure regulating screw (12) in order to obtain a pressure reading of 5500 kPa (800 psi) on gauge (5) .

    Note: 5500 kPa (800 psi) is the appropriate pressure for the accumulator when the ambient temperature is 21 °C (70 °F). If the machine has been running for some time, the temperature of the accumulator may be different from the ambient temperature of the outside air. Refer to Table 2 for the proper pressure.

14. Open needle valve (9) . Measure the amount of time that is required for gauge (10) to obtain the charge pressure. Charging time should take 10 to 20 seconds.

    Note: If the charging time is less than 10 seconds, repeat Step 1 through Step 8 in order to exhaust the nitrogen gas from the accumulator. Repeat Steps 9 through 14 in order to charge the accumulator.

15. Once the accumulator is charged, close the nitrogen charging valve.
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    Illustration 15	g02606758
    158-2336 Gas Valve

    1. Accumulators equipped with a 158-2336 Gas Valve , with a wrench, tighten hex nut at location (B) of the nitrogen charging valve in a clockwise direction to close the nitrogen charging valve (2) . Tighten the hex nut to a torque of 8.8 ± 2 N·m (6.5 ± 1.5 lb ft)

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Illustration 16	g02614762
222-2367 Gas Valve Assembly

16. Accumulators equipped with a 222-2367 Gas Valve Assembly , turn valve handle (14) in a counterclockwise direction in order to close nitrogen charging valve (2) .

17. Close the valve on the nitrogen cylinder.

18. Slowly loosen chuck (15) from accumulator valve (2) and allow the pressure to vent from hose (16) . Observe gauge (10) in order to determine when the pressure has been released from hose (16) .

19. Remove chuck (15) from accumulator valve (2) .

20. Install the protective cap (A) on accumulator valve (2) .

21. Install guard (1) .

22. Use the ET to return the ride control to the automatic mode.

    1. Select "Transmission ECM".

    2. Select "Override Parameters".

    3. Select "Disable Override".

    4. Exit the ET software.

Diverter Valve Test

Note: The following steps are used to determine if the diverter valve is operating correctly. This test should be performed in order to verify that the ride control is being activated.

1. Lift the front wheels off the ground by moving the bucket to the full LOWER position. With the front wheels off the ground, place the lift control lever in the HOLD position.

2. Use Caterpillar Electronic Technician (ET) in order to turn the ride control ON.

   1. Open the software program for the ET.

   2. Select "Transmission ECM".

   3. Select "Override Parameters" that is located in the drop-down menu under "Diagnostics".

   4. Select "Change".

   5. Select "ON" for the "New Value" .

   6. Select "OK".

   7. A window will appear on the screen that will ask you if you want to change the parameter. Select "Yes".

      Note: The ride control will activate when "Yes" is selected. The front wheels should lower to the ground. If the wheels do not lower to the ground, the diverter spool has not shifted to the ON position. The following causes could be the reason that the diverter spool does not move to the ON position:

      • a failure of the ride control switch

      • a failure of the solenoid coil on the diverter valve

      • a failure of the cartridge valve in diverter valve

      • a failure of the spool valve in the diverter valve

      • a blockage in pilot circuit to the diverter valve

Road Test

Note: The pressure of the procedure in Step 9 of the "Testing Procedure for the Accumulator Precharge Pressure" is the recommended pressure for machines with a bucket of typical weight and average payload.

Machines with heavy buckets and large payloads may need an increase in the nitrogen charge pressure. With the ride control switch in the ON position, The increase in nitrogen charge pressure will keep the piston in the accumulator from contacting the stop during normal roading.

Note: Raising the nitrogen charge pressure will result in a stiffer ride.

1. Place a typical payload in the bucket.

2. Move the ride control switch to the ON position.

3. Drive the machine over a fairly rough road surface.

4. If the ride is too soft or a noise is heard from contact between the piston and the stop, the nitrogen charge pressure must be increased.

Note: The ride control accumulators are rated up to 35000 kPa (5100 psi).

5. If the ride is too soft return to Step 9 of the "Testing Procedure for the Accumulator Precharge Pressure" procedure and increase the accumulator charge pressure by 345 kPa (50 psi). Perform the road test again. Add sufficient nitrogen in order to obtain a suitable ride for the payload of the machine.