The proper lubrication of gear drives is very important because of the relatively high cost of replacing gears. For treatment purposes, two types of gear drive must be recognized: Fully enclosed oil-tight gears, and open or partially-enclosed gears.
Enclosed Gears
This first type, known as spur & worm or spur & herringbone gears, needs splash oiling, and some larger drives require pump circulation as well. Here are the instructions to follow:
Oil Level: Gauges are provided for checking the level, and inspections should be made regularly. Add oil whenever the level drops ¼” or more below the correct point. Make sure to read the level when the gears are idle; otherwise, you won’t get a true reading.
Oil Changes: Every six months should be sufficient in most cases. Deterioration occurs with time and use due to the effect of oxidation and entrance of impurities.
The timing will be influenced by oil quality, hours of use, temperature condition, the degree of contamination, etc. Laboratory analysis is the only sure way to determine when the oil has become unfit for further use. For small installations, though, visual examination by trained personnel can suffice.
Oil Grade: Good lubricating properties and superior quality are needed in the oil for Enclosed Gears. The oil should resist oxidation and thickening, while sludge or deposits should separate freely from any water which may gain entrance. A viscosity range of 900 to 1,000 SSU will usually give good results. Note: Oils of the extreme pressure type are not needed for this service.
Open or Partially-Enclosed Gears
These types of gear are mostly small and lightly loaded, and lubrication is not always absolutely vital. On the other hand, if you appreciate a quiet operation and a long gear life, a soft grease with good adhesive qualities every week is highly recommended.
For open gears somewhat larger in size (say, over 12” pitch diameter), use a heavy tacky gear lubricant. Normally, there are two choices – one requiring prior warming for easier application by brush or swab, the other pre‐diluted with a solvent to be used as received – the latter having a distinct advantage.