Page 293 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Power Transmission Gears 273

Figure 6-34. Continued.

3. Mechanical spray: This is intermittent lubrication usually per-
formed by an automatic timer where the oil is supplied to the gears
or bearings in limited amounts at certain intervals.

Lubrication of High Speed Units
The oil furnished to high speed gears has a dual purpose: lubrication of
the teeth and bearings, and cooling. Usually, only 10 to 30 percent of the
oil is used for lubrication and 70 to 90 percent is used for cooling.
For high speed gear units, a turbine-type oil with rust and oxidation
inhibitors is preferred. This oil must be kept clean (filtered to 40 microns
maximum, preferably to 25 microns), must be cooled, and must have the
correct viscosity. Synthetic oils should not be used without the manufac-
turer’s approval.
For some reason, the high speed gear unit makes all the compromises
when the oil viscosity for the machine system is determined. Usually a