769D Off-Highway Trucks: Suspension Cylinder (Rear) - Purge and Charge

Perform Testing and Adjusting, "Visual Inspections" 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. Check the suspension cylinders against the dimensions from the last time that you performed the charging procedure. The suspension height will be different for each machine.

When the rear suspension cylinders are properly charged, the left rear suspension cylinder will not show as much chrome as the right rear suspension cylinder shows. This is due to the rigid frame and 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.

(1) Valve cap(2) Charging valve



1. Remove valve caps (1) from the charging valves (2) that are located on each of the rear 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 7S-5106 Chucks. The charging hoses will be used to drain oil into an approved container.

NOTICE
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.Dispose of all fluids according to local regulations and mandates.



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 the 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) Reference line on the cylinder (5) Reference line for the oil charging procedure (6) Reference line for the nitrogen charging procedure(7) Reference line for the nitrogen charging procedure



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 can also be mounted with the clamps that are used to mount the dust boot. 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 cylinder head. Put a corresponding reference line (4) on the edge of the cylinder head.

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) .

4. Measure the difference between the outside ambient temperature and the temperature of the service shop. If this temperature difference is less than 11°C (20°F), use Table 2 to create guidelines for the nitrogen charging procedure. Table 2 shows the distance between the reference line that is indicated and reference line (3).

   Table 2

   Reference line (6)	128 mm (5.0 inch)
   Reference line (7)	140 mm (5.5 inch)

5. 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 need to change the location of the reference lines. Add 2.54 mm (0.10 inch) of distance 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)
   Additional length for temperature compensation
   50°C (90°F) × 2.54 mm (0.10 in) ÷ 5.5°C (10°F) = 23.1 mm (.90 in)
   Corrected guidelines for the nitrogen charging procedure
   128 mm (5.0 mm) + 23.1 mm (0.90 in) = 151.1 mm (5.90 in)
   140 mm (5.5 mm) + 23.1 mm (0.90 in) = 163.1 mm (6.40 in)

Oil Charging Procedure

Table 3

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.

Typical example of the setup for the oil charging procedure

Correct oil level (3) Reference line (4) Reference line on the cylinder (5) Reference line for the oil charging procedure (6) Reference line for the nitrogen charging procedure(7) Reference line for the nitrogen charging procedure

Note: Use SAE 10W oil with a service classification of CH 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 reference line (5) lines up with reference line (4) on the cylinder.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 reference line (4) on the cylinder 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 4

Tools Needed	Qty
5P-8610 Auxiliary Fitting Group	1
7S-5437 Nitrogen Charging Group	1

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).

Typical example of the setup for the nitrogen charging procedure

Correct nitrogen charge (3) Reference line (4) Reference line on the cylinder (5) Reference line for the oil charging procedure (6) Reference line for the nitrogen charging procedure(7) Reference line for the nitrogen charging procedure

1. Attach the 7S-5437 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 2413 kPa (350 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) .

4. Allow nitrogen into the suspension cylinder until the reference line (4) on the cylinder is between reference line (6) and reference line (7) .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 to the proper length, close both of the shutoff valves. Turn the check valves on the 7S-5106 Chucks counterclockwise. This closes charging valves (2) .

6. Turn off the nitrogen pressure at the supply tank. Remove the 7S-5437 Nitrogen Charging Group. Install the valve caps to the charging valves. Torque the valve caps to 3 to 5 N·m (25 to 45 lb in).

7. 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 rear suspension cylinders.

This is an alternative to Step 7. 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 rear suspension cylinder.

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

If you need more information, You can visit:

http://www.cat.com

769D Off-Highway Trucks: Suspension Cylinder (Rear) - Purge and Charge 2013-01-02T20:39:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown