Lubricant is the ammunition of the maintainer in the war on wear. How much and proper placement is critical in the effectiveness of the lubricant. Both are critical.
Typical design methods for applying lubrication to the system components application systems depend mainly on the running speed of the bearing. These methods can vary in gearboxes/reducers but usually follow the following guidelines:
- Oil bath and splash systems – low and medium speeds.
- Circulating systems – medium speeds.
- Spray or mist – high speeds.
In oil bath or splash systems, the oil level in the gearbox is maintained so that the teeth of the bottom gear just dips into the oil. Alternatively a pressure circulating system may be used in which oil is sprayed on the teeth close to the point of engagement and is re-circulated either directly from the bottom of the gearbox or by the way of the oil tank.
In an oil bath or splash system, overfilling a gearbox sump can be just as damaging as under- filling. Overfilling may cause air entrainment and foam, overheated oil and leakage due to overflow. Over time oxidation may occur due to increased temperatures and exposure to air. Marginal lubrication can also result in pitting because oil film does not spread the contact (cushion) over a sufficiently wide area. This can result in metal-to-metal contact in the load zone.
Level gauges and viewing windows allow for visual inspection of the fluid levels and oil condition (cloudy, dark, foaming etc.) and should be recorded and trended along with top-up activities. These results can be used to determine changing conditions and increased or decreased monitoring / testing activities.