Gas Turbine Handbook : Principles and Practices

Accessories 95
incorporate anti-friction bearings, use a synthetic oil. Mineral oils are
manufactured (distilled) from petroleum crude oils and are generally
less expensive than synthetic lubricants. Synthetic lubricants do not
occur naturally but are “built up” by reacting various organic chemicals,
e.g., alcohol’s, ethylene, etc., with other elements. Synthetic
lubricants are used primarily in very high temperature applications
(less than 350°F and 175°C) or where its fire-resistant qualities are
required.
Lubrication Oil Application
Bearings in gas turbines are lubricated, almost without exception,
by a pressure circulating system. Pressure circulating lubrication
consist of a reservoir, pump, regulator, filter, and cooler. Oil in
the reservoir is pumped under pressure through a filter and oil cooler
to the bearings and then returned to the reservoir for re-use (Figure
6-6).
Reservoir
The reservoir is used to store the oil during periods of unit shutdown,
and to deaerate the oil during operation. The reservoir must be
large enough to contain all the oil used in the gas turbine, piping, and
Figure 6-6. Typical lubrication oil schematic.