In grease lubrication, the lubricating characteristic of grease deteriorates with operating hours, thus requiring relubrication of the bearing at appropriate intervals. Relubrication intervals of grease depend on the type, dimensions, and speed of the bearing, and the type of grease.
A line diagram serving as a rough guide of grease relubrication intervals, is given in the bearing section of the NTN general catalog.
For oil lubrication, oil changing intervals depend on the operating condition of the machine and the type of lubrication system (a rough guide to oil changing intervals and for oil analysis intervals is given in Tables 1 and 2) .
Table 1: Lubrication Oil Properties and Serviceable Limits
| Property | Serviceable limit | Remarks | ||
|---|---|---|---|---|
| Circulating oil | Gear Oil | |||
| Viscosity Deterioration mm2/s | Less than 10% |
25% max., 10 to 15% is preferble |
Caused by oxidation or mixing with different type of oil. | |
| Water content volume % | 0.2 max. |
0.2 max. |
May be reusable after water removal | |
| Insoluable matter Nomal in weight Pentane | Nomal Pentane % |
0.2 max. |
0.2 max. |
Additive carbon particles |
| Benzene % | 0.9 max. |
0.5 max. |
Dust | |
| Sedimentation value ml/10ml | 0.1 max. |
Contaminants such as water and dust, or worn metal particles. | ||
| Total acid value KOH mg/g | 2 to 3 times that of new oil |
Adopt higher value according to additives | ||
| Ash % | - | 0.2 max. | ||
| Iron content in ash % | - | 0.1 max. | ||
Table 2: Frequency of Lubricating Oil Analysis
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| Severe operating conditions means : (1)Severe water condensation or ingress (2)Excessive ingress of dust, gas, etc. (3)Operating temperature exceeding 120 °C |
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|Bearing Temperature|Operating Sound of Bearing|
|Vibration of Bearing|Lubricant Selection|Relubrication|
|Vibration of Bearing|Lubricant Selection|Relubrication|
