Bearings steam turbines

Steam turbine considerations. The speed at whieh the turbine must operate and the steam eonditions available influenee the operating effieieney of the unit. Double-ended steam turbines require speeial eonsideration of thrust bearing sizing, overspeed proteetion, and governing systems. 

King, T.F., and Capitao, J.W., Impact on Recent Tilting Pad Thrust Bearing Tests on Steam Turbine Design and Performance, Proceedings of the 4th Turbomachinery Symposium, Texas A M University, October 1975, pp. 1-8. 

The system should have an aeeumulator to maintain suffieient oil pressure while the standby pump aeeelerates from an idle eondition. An aeeumulator beeomes a must if a steam turbine drives the standby pump. Overhead tanks are speeified by many users to assure flow to eritieal maehinery eomponents. The sizing of the tanks varies depending on the applieation. In some gas turbine applieations, the bearings reaeh maximum temperature as long as 20 minutes after shutdown. 

Other items unique to steam turbines that must be considered are water carryover and fouling. Carryover can leave deposits on the blading, causing loss in performance and increased thrust loads. If carried to an extreme, thrust bearing failure could occur. If a large amount of water is carried over as a slug of liquid, catastrophic failure can occur. 

It is important to seal the glands on the turbine shaft, and a typical arrangement is illustrated in Figure 14-24. Thrust bearing failures can be serious problems for steam turbines and other mechanical drives, as well as the bearings used on the driven equipment. 

Figure 43.6 illustrates the periodic motion time-domain curve of a steam turbine bearing pedestal. Displacement is plotted on the vertical, or Y-axis, and time on the horizontal, or X-axis. The curve shown in Figure 43.6 is the sum of all vibration components generated by the rotating element and bearing-support stmcture of the turbine. 

Steam-turbine lubricants Lubricants in steam turbines are not exposed to such arduous conditions as those in engines. The main requirement is for high oxidation stability. However, they may be exposed to aqueous condensate or, in the case of marine installations, to sea water contamination, so they have to be able to separate from water easily and to form a rustpreventing film on ferrous surfaces, and it is usual to employ rust inhibitors. The problem of tin oxide formation on white-metal bearings is associated with the presence of electrically conducting water in lubricants and can be over-come by keeping the lubricant dry . 

Pb bearing efficiency or uncorrected steam-turbine efficiency... 

Steam turbine used for the generation of electricity Turbine overspeeding [load disconnection suddenly] /[trip throttle valve stuck] /control valve fault//[extrac-tion valve fault]. Bearings damaged" [turbine overspeeding] /[lube oil] /exces-sive vibration/no lube oil/bearing temperature too hot/insuffident oil because of dogged lines/flow of parasitic currents. 

Valves, piping, and vessels Pumps, compressors, fans, and blowers Steam turbines and motors Heat exchangers and cooling towers Boilers and furnaces Reactors and distillation columns Instrumentation Basic hand tools Lubrication, bearings, and seals Flares, mixers, and steam traps... 

Steam turbines are used as drivers to turn pumps, compressors, and electric generators. High-pressure steam is directed into buckets designed to turn a rotor and provide rotational energy. Steam turbines serve the same function as electric motors. A typical motor is composed of stator windings, rotor and shaft, bearings and seals, conduit box, frame, fan, lubrication system, and shroud. Steam turbines and motors are two of the most popular devices used by industry as drivers. 

Lubrication systems provide a constant source of clean oil to pump and compressor bearings, gearboxes, steam turbines, and rotating or moving equipment. A typical lubrication system includes a lubricant reservoir, pump, valves, heat exchanger, and piping. Figure 9-5 illustrates how an industrial lubrication system operates. 

F.D. "Performance of large steam turbine journal bearings", ASLE Trans., 13, 1970, 262-268. 

MICHELL BEARING FOR A STEAM TURBINE DESIGNED BY H.T. NEWBIGIN AND TESTED BY HIM AT MESSRS. BELLIS AND MORCOM LIMITED, BIRMINGHAM, JUNE 1910. 

BAHR, H.C. Recent improvements in load capacity of large steam turbine thrust bearings, Trans ASME Jrn. of Engr. for Power,, 130-136, Jan. 1961. 

The hot side of steam turbines and the blades of feed water pumps are made from 12% chromium steels, also wear resistant components such as bearings and pump shafts and valve spindles, which are sometimes hard chrome plated. Support grids for fuel rod elements are also made from chromium steel. The corrosion loss of these materials in demineralised water at 260 °C is 0.007 mm/a at pH 7 and 0.11 mm/a at pH 10 [72]. 

A typical example is a steam turbine. A turbine must be supported by auxiliary running gear during startup or shutdown to prevent damage to the sleeve bearings. The lower speeds during the startup and shutdown phase... 

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