Gear Lubrication Techniques

Proper amount of lubrication is necessary for satisfactory performance of gears and durability of gears. Inadequate lubrication becomes responsible for scoring failure of gears.

Purpose of Gear Lubrication : 

Gear lubrication is used for reducing the power losses, also used to minimize the wear of the teeth.Gear lubricant acts as coolant by dissipating the heat.As much like used in engine, lubricant carries away the worn-out particle.Also to prevent corrosion gear lubrication is used.Minimization of noise, shock, vibrations, etc. can be achieved by use of lubricants.

Lubricants used in Gears :

Different types of lubricants used in gears are given as below:

1.Grease : The open type of gears which are operating at very low pitch line velocities, are lubricated by grease.

2.Motor Oils : The transmission gears which are used in multi-speed gearboxes are lubricated by motor oils. In fact, we can say that they are lubricated with SAE motor oils. The motor oils contains strong additives.
The grades of different motor oils used are SAE 5W, SAE 10W, SAE 20, SAE 30, SAE 40 and SAE 50.

3.Straight Mineral Oils : Normally, straight mineral oils are used for medium duty gears lubrication purpose. No additives are included in it.

4.Gear Oil : Heavy duty gears are lubricated with the help of gear oils. These oils have stronger additives of Extreme Pressure type. The SAE grades of different gear oils used are : SAE 75W, SAE 80W, SAE 90, SAE 140 and SAE 250.

Modes of Gear Lubrication :

1.Grease Lubrication : As discussed above, grease is used as lubricant for very low pitch line velocities. Hence this type of lubrication is used when hydrodynamic action is not possible.
2.Drip-feed Lubrication : For low pitch line velocities, drip-feed lubrication under gravity can be used.
3.Splash Lubrication : This type of lubrication is used for medium pitch line velocities. In this type of lubrication, a portion of gear (running gear) dips into oil sump and oil is splashed. This oil splash lubricates the gear pair.
Note that for spur and helical gears, the lower gear should be dipped by four to six times the module of that gear in the oil bath.
4.Spray or Jet Lubrication : For high pitch line velocities, the pressurised spray lubrication is used.

Sujit Kadus

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