Turning gear

Upon unit startup, the turning gear motor can continue to rotate... 

Tail gas expander without or with adjustable inlet guide vanes (14) and 22 guide vane seltirig motor (15), labyrinth shaft seals wnth air scaling Turning gear... 

Tail gas expander with or without adjustable inlet guide vanes (17) and guide vane setting motor (18), labyrinth shaft seals with air sealing Turning gear... 

For gas turbines, especially the more advanced high-temperature gas turbines, the oil of choice should be synthetic oil, since synthetic oils have a high flash point. Gas turbine lubrication systems should be run for about 20 minutes after shutdown since maximum temperatures are reached after 10 minutes of shutdown especially in the bearing area. Most gas turbines are also on turning gear to avoid sagging in the shaft. Mineral oils can be used for the compressor. It is not uncommon to have two types of oil in a petrochemical plant. Mineral oil costs much less than the synthetic oil. 

If left on turning gear, it will continue until the turbine exhaust temperature decreases to 150 °F (66 °C), and a suitable amount of time (up to 60hrs) has elapsed. At this point, the turning gear and auxiliary lube oil pump will stop and the shutdown sequence is complete. On recognition of a shutdown condition, various contact status and analog values are saved (frozen) for display, if desired. 

Other applications, e.g., fan drives, starter drives, turning gears... 

The clutch automatically engages at the instant the input speed tends to overtake that of the output shaft. Conversely, the clutch will disengage also fully automatically when the output shaft speed exceeds the speed of the input shaft. A full range of turning gear clutches is available. 

FIG. P-64 Automatic turning gear clutch type MS-8-T installed In gearbox between turning gear and pinion shaft. (Source MAAG Gear Company.)... 

Optional turning gear prior to startup and shutdown for large bearing span rotors can be supplied for automatic or manual operation. 

This system incorporates a modern overrunning automatic clutch that engages automatically when the rotor reaches turning gear speed, and it automatically disengages when that speed is exceeded. See Fig. T-63. 

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