769D Off-Highway Trucks. Suspension Cylinder (Front) - Purge and Charge

Perform Testing and Adjusting, "Visual Inspection" before you service the suspension cylinders.

The machine must be on level ground when you inspect the suspension cylinder charge. The truck body must be empty. Coast the machine to a gentle stop without using the brakes. Take note of the current ride height of the suspension cylinders. Look up the dimensions for the previous ride height of the suspension cylinders after the last nitrogen charging procedure. Compare the two values. The suspension height will be different for each machine.

When the front suspension cylinders are properly charged, the left front suspension cylinder will not show as much of the chrome as the right front suspension cylinder shows. This is due to the weight of the cab.

Note: Both suspension cylinders must be charged at the same time. If only one suspension cylinder needs servicing, perform the procedure on both suspension cylinders.

Purge the Suspension Cylinder of Oil and of Nitrogen

Table 1

Tools Needed	Qty
9U-5617 Oil Refill Pump	1

WARNING: Personal injury or death can result from sudden suspension cylinder movement. Sudden movement, up or down, can cause the clearance above your head to change rapidly. Read all warning labels on the suspension cylinders before servicing. Do not check the oil in the suspension cylinder until all the nitrogen pressure has been released. Do not, under any condition, remove valves, cover or plugs from the cylinder unless the rod is fully retracted and all the nitrogen pressure is released.Do not stand under the machine when testing or adjusting the suspension cylinders.

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, NENG2500, "Caterpillar Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Caterpillar products.Dispose of all fluids according to local regulations and mandates.

(1) Valve cap(2) Charging valve

1. Remove valve caps (1) from the charging valves (2) that are located on each of the front suspension cylinders. Disconnect the charging hoses from the rest of the 9U-5617 Oil Refill Pump. Turn the check valves on the 7S-5106Chucks counterclockwise in order to ensure that the charging valves will not open during installation. Install the charging hoses to charging valves (2) with the 7S-5106 Chucks. The charging hoses will be used to drain oil into an approved container.

2. Turn the check valves on the 7S-5106 Chucks clockwise. This opens up charging valves (2). This allows oil and nitrogen to flow through charging valves (2). When the suspension cylinders have bottomed completely, leave the check valves in position for five minutes in order to allow the pressure in the suspension cylinders to equalize.

3. After the pressure has equalized, turn the check valves on the 7S-5106 Chucks counterclockwise. This closes charging valves (2) .

4. Remove the charging hoses from charging valves (2). Attach the charging hoses to rest of the 9U-5617 Oil Refill Pump. Place the ends of the charging hoses into an approved container or into the filler tube of the 9U-5617 Oil Refill Pump. Cycle some oil in order to ensure that the charging hoses are full of clean oil. Attach the 7S-5106 Chucks to charging valves (2) .

Setting Up For Measurement

(3) Reference line (4) Top edge of the axle(5) Reference line

1. Position a steel ruler or a thin strip of sheet metal on both of the suspension cylinders in order to measure the rod extension. A magnet can be used in order to mount the measuring tool. Possible magnets include the magnetic plug for the final drive and the magnetic base for a dial indicator. The measuring tool should extend downward. The measuring tool should be parallel to the centerline of the suspension cylinder.

2. Create reference line (3) on the steel ruler. Reference line (3) should line up with the top edge of the axle (4) .

3. Create reference line (5) in order to indicate the guideline for the oil charging procedure. Reference line (5) should be 25.4 mm (1.00 inch) below reference line (3) .

(6) FT1680 Gauge Block

One FT1680 Gauge Block (6) is required for each suspension cylinder. These gauge blocks are required for correct service of the front suspension cylinders.

Measure the difference between the outside ambient temperature and the temperature of the service shop. If this temperature difference is greater than 11°C (20°F), you will also need to use shims. Add 3.2 mm (0.125 inch) of shims for each 5.5°C (10°F) of temperature difference.

Example

Note: Estimate the temperature difference to the nearest 5.5°C (10°F).

Temperature of the service shop ... 10°C (50°F)

Outside ambient temperature ... −40°C (−40°F)

Difference in temperatures

10°C (50°F) − (−40°C (−40°F)) = 50°C (90°F)

Shim thickness:

50°C (90°F) × 3.2 mm (0.125 in) ÷ 5.5°C (10°F) = 29.1 mm (1.125 in)

Dimension for the nitrogen charging procedure

170.0 mm (6.69 in) + 29.1 mm (1.125 in) = 199.1 mm (7.81 in)

Oil Charging Procedure

Table 2

Tools Needed	Qty
9U-5617 Oil Refill Pump	1

WARNING: Personal injury or death can result from sudden suspension cylinder movement. Sudden movement, up or down, can cause the clearance above your head to change rapidly. Read all warning labels on the suspension cylinders before servicing. Do not check the oil in the suspension cylinder until all the nitrogen pressure has been released. Do not, under any condition, remove valves, cover or plugs from the cylinder unless the rod is fully retracted and all the nitrogen pressure is released.Do not stand under the machine when testing or adjusting the suspension cylinders.

Note: Use SAE 10W oil with the current service classification for the oil charging procedure.


1. The charging hoses and the 7S-5106 Chucks should be connected to charging valves (2). Open the shutoff valves. Adjust the air pressure on the regulator. The air pressure must not exceed 860 kPa (125 psi).

2. Turn the check valves on the 7S-5106 Chucks clockwise. This opens up charging valves (2) .

3. Inject the oil into the suspension cylinder until the top edge of the axle (4) lines up with reference line (5) .Note: If one suspension cylinder reaches reference line (5) before the other suspension cylinder, close the shutoff valve for that suspension cylinder. Continue injecting oil into the other suspension cylinder until the top edge of the axle (4) lines up with reference line (5) .

4. Close the shutoff valves. Turn off the air pressure at the regulator. Turn the check valves on the 7S-5106 Chuck counterclockwise. This closes charging valves (2) .

5. After the pressure has returned to zero, use the quick couplers to remove the charging hoses. If the quick couplers are not available, you may need to remove the 7S-5106 Chucks .

Nitrogen Charging Procedure

Table 3

Tools Needed	Qty
175-5507 Nitrogen Charging Group	1
5P-8610 Auxiliary Fitting Group	1
9U-5617 Oil Refill Pump	2

WARNING: Dry nitrogen is the only gas approved for use in the suspension cylinders. Charging the suspension cylinders 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 you order nitrogen gas, be sure that the cylinders are equipped with CGA No. 580 Connections. Do not use color codes or other methods of identification to tell the difference between nitrogen cylinders 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).

1. Attach the 175-5507 Nitrogen Charging Group to the quick couplers or to the charging valves at each suspension cylinder.Note: To prevent oil flow into the charging hoses, do not open the charging valves at this time.

2. On the supply tank, adjust the regulated pressure to 4150 kPa (600 psi).

3. Open the shutoff valves in order to allow nitrogen to flow to the 7S-5106 Chucks. Turn the check valves on the 7S-5106 Chucks clockwise. This opens up charging valves (2). This allows nitrogen to flow to charging valves (2) .

NOTICE
To protect the wiper seals on the front suspension cylinders from damage when the gauge blocks are inserted, make sure the gauge blocks include the chamfer.




4. Allow nitrogen into the suspension cylinder until gauge block (6) and any required shims can be inserted between the axle and the suspension cylinder.Note: If one suspension cylinder has extended to the correct amount before the other suspension cylinder, close the shutoff valve for that suspension cylinder. Continue allowing nitrogen into the other suspension cylinder until the correct extension has been reached.

5. After the suspension cylinders have extended and after the gauge blocks have been inserted, close both of the shutoff valves. Turn the check valves on the 7S-5106 Chucks counterclockwise. This closes charging valves (2) .

6. Disconnect the charging hoses at the quick couplers. Turn the check valves on the 7S-5106 Chucks clockwise. This opens charging valves (2) in order to release nitrogen from the suspension cylinders. Continue to purge nitrogen until the suspension cylinders come down to rest on the gauge blocks. Then, turn the check valves on the 7S-5106 Chucks counterclockwise. This closes charging valves (2) .

7. Connect the charging hoses to the quick couplers. On the supply tank, adjust the regulated pressure to 2400 kPa (350 psi).

8. Open the shutoff valves. Turn the check valves on the 7S-5106 Chucks clockwise. This opens charging valves (2). Allow nitrogen to flow into both suspension cylinders. Leave the charging valves open for approximately five minutes in order to allow the pressure to equalize. Then, turn the check valves on the 7S-5106 Chucks counterclockwise. This closes charging valves (2). Close the shutoff valves. Turn off the nitrogen pressure at the supply tank.

9. Remove the 175-5507 Nitrogen Charging Group. Install the valve caps to the charging valves. Torque the valve caps to 2 to 3 N·m (18 to 27 lb in).

10. Start the engine. To remove the gauge blocks, raise the truck body and turn the steering wheel so that the front wheels move. The suspension cylinders should raise. When the suspension cylinders are not resting on the gauge blocks, remove the gauge blocks.

11. After the suspension cylinders have been properly charged, measure the exposed chrome length of each suspension cylinder. Record this measurement. Use these recorded dimensions as a reference when you inspect the front suspension cylinders.

This is an alternative to Step 11. Operate the machine for several load cycles after the machine has been properly charged. Some of the exposed chrome length will be clean because of the wiper seals. Measure this length for each suspension cylinder. Record this measurement. Use these recorded dimensions as a reference when you inspect the front suspension cylinder.

The normal height of a charged suspension cylinder will be less than the height of the gauge block.

When the front suspension cylinders are properly charged, the left front suspension cylinder will not show as much of the chrome as the right front suspension cylinder shows. This is due to the weight of the cab.

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769D Off-Highway Trucks. Suspension Cylinder (Front) - Purge and Charge 2013-01-02T20:41:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown