TIRE & RIM AR 2278206 - Caterpillar

Caterpillar EquipmentThe Scheduled Oil Sampling (S.O.S.) program is an important tool to find the condition of the oil in the hydraulic system. The amount of wear metals in the oil can give an early indication of when repairs to the hydraulic system components are necessary, so a major failure can be prevented.
The S.O.S. equipment (infrared analysis) can also be used to determine when the hydraulic oil must be changed. The Lubrication and Maintenance Guides recommend that the hydraulic oil be changed every 2000 hours or one year. This change interval gives acceptable performance during normal operation. Some conditions, such as coolant leakage into the hydraulic oil or oil that gets too hot, will make an earlier change necessary. The S.O.S. tests will show if the earlier change is needed.
The oil can also be tested at the 2000 hours or one year interval to determine if the change period can be extended. The tests will give an indication of the level of contamination and other oil properties (characteristics). The results of these tests will show if the oil quality is acceptable for reuse.
For the hydraulic oil to be used beyond the normal change interval, several conditions must be met. First, all test results must be within the acceptable limits of the S.O.S. specifications. There must not be any indication that the oil was too hot during operation. There must be no indication of coolant in the oil.
The tests that follow will give the necessary information to find the condition of the oil.
1. Contamination tests: ... for silicon and wear metals
Use the atomic absorption test to determine the concentration of these wear particles. Remember, a filter change may give a reduction in these particles.
... for water
If this water is caused by the normal "breathing" of the hydraulic tank, there is no practical way to prevent it. The amount of water can be checked by differential infrared spectroscopy or by the sputter test.
... for coolant
Cooler leaks can let coolant enter the hydraulic system. Differential infrared spectroscopy can be used to find coolant in the hydraulic oil. Another test procedure is to use the sputter test to find water in the oil and the chemical test for the anti-freeze.
2. Tests