ABSTRACT
The steam turbine is used as the prime mover for driving equipment such as blowers, pumps and compressors, but its predominant use is to drive alternators and generators for the production of electricity. The main bearings of a steam turbine are plain white metal journal bearings and are lubricated hydrodynamically by the formation of a high-pressure wedge of oil between the shaft and white metal. Because of the load on the bearings of large turbines at start-up, hydrostatic pressure lubrication is used to lift the shaft from the bottom of the bearing. This facilitates the formation of a hydrodynamic film and prevents wear. The control system of a steam turbine may be mechanical, hydraulic or electro-hydraulic. Except in the smallest units, which are wholly mechanically operated, the governor response is transmitted to relay or servo valves by oil pressure. Protective devices such as trip and unloading gear are also hydraulically operated.
