770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System: Hoist Cylinder Performance - Test , Hoist Control - Adjust & Hoist System Enable - Check

Hoist Cylinder Performance - Test

WARNING: Personal injury or death can result from sudden machine movement.Sudden movement of the machine or the release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury before testing and adjusting the hydraulic system, perform the procedure in the Testing and Adjusting, "General Information" section.

1. Start the engine. Operate the engine at high idle.

2. Move the hoist control to the RAISE position. Hold the hoist control in the RAISE position for five seconds after the dump body is fully raised. Then, lower the dump body all the way to the truck frame.

3. Repeat Step 2 until the temperature of the hydraulic oil is above 38°C (100°F).

Lift Time for Hoist Cylinders

1. Lower the dump body to the truck frame.

2. Operate the engine at high idle.

3. Raise the dump body to the fully raised position. Use a stopwatch to measure the required time.

The required time for full extension of the hoist cylinders is approximately 18 seconds.

Cylinder Drift

Note: Perform this test with an empty dump body and hydraulic oil above 38°C (100°F).

1. Move the hoist control to the RAISE position.

2. When the first stage of the hoist cylinders is extended by 305 mm (12 inch), move the hoist control to the HOLD position.

3. The dump body will push the cylinder head of the first stage by 6.40 mm (0.25 inch) onto the second stage of the hoist cylinders. Use a stopwatch and record the required time.

The acceptable time for cylinder drift is relative to the temperature of the hydraulic oil in the hoist cylinders. See the following table.

Table 1

Acceptable Cylinder Drift
Minutes	Oil Temperature	Cylinder Drift
12.4	38°C (100°F)	6.40 mm (0.25 inch)
9.6	43°C (110°F)	6.40 mm (0.25 inch)
7.8	49°C (120°F)	6.40 mm (0.25 inch)
6.4	54°C (130°F)	6.40 mm (0.25 inch)
5.3	60°C (140°F)	6.40 mm (0.25 inch)
4.4	66°C (150°F)	6.40 mm (0.25 inch)
3.8	71°C (160°F)	6.40 mm (0.25 inch)
3.2	77°C (170°F)	6.40 mm (0.25 inch)
2.8	82°C (180°F)	6.40 mm (0.25 inch)

Excessive cylinder drift can be caused by the following conditions:

• Leaks in the lines between the hydraulic tank and the hoist cylinders
• Worn control valve spool
• Worn seals in the hoist cylinders

Hoist Control - Adjust

The hoist valve LOWER position is an adjustable parameter in the Chassis Electronic Control Module (Chassis ECM) by using Electronic Technician (ET). Adjusting the hoist valve compensates for differences in the valve. Adjusting the hoist valve modifies the speed of the lowering of the dump body.

The process for adjustment has two components:

• Adjust the position sensor for the dump body.
• Adjust the hoist lower valve.

Hoist System Enable - Check

The hoist system function is intended to allow the service technician to tell the ECM the desired state of the hoist system. The hoist system function may be changed with the Caterpillar Electronic Technician.

The allowed states for the hoist system function are listed:

"Not installed" - This would be the state if the hoist system was not installed on the machine.

Enabled - This would be the state of a normally operating machine with a hoist system.

Disabled - This would be the state of the machine when the hoist system has been locked in hold.

If the hoist system does not work, verify that the hoist system is enabled. Use the display for the configuration parameter through the service menu in the Caterpillar Electronic Technician.

If you need more information, You can visit:
http://www.cat.com

770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System: Hoist Cylinder Performance - Test , Hoist Control - Adjust & Hoist System Enable - Check 2013-01-22T17:56:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown