Steam turbine lubricants

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 . 

No moving parts are involved in the combustion process of gas turbines therefore, the turbines make little demand on the lubricant and present few lubrication problems. Gas turbines for industrial applications have evolved from steam turbine practice, thus they are similar in design and lubrication requirements except that operating temperatures are much higher. Accordingly, steam turbine lubricants can often be used in industrial gas turbine lubrication but for particularly high temperatures, synthetic lubricants are required. 

High-quality steam turbine lubricants usually satisfy the demanding requirements of modern, high-output steam turbines, including their geared units, and are also used for industrial gas turbines and water turbines. In addition to turbine oils being used for electric power plant turbines they are also used for turbo-machinery like turbine compressors of chemical plants. Additionally, turbine oils can be used for hydraulic systems as hydraulic oils in these systems. 

Maintenance and Reliability Preventive maintenance requires that all engines be shut down at periodic intervals for inspection and repair. For properly maintained heavy-duty engines availability is over 97 percent, with maintenance costs of 2.50 to 5 per horse-power-year and lubricating-oil consumption of 1 to 2 gal/hp-year. While this represents a high degree of reliability, outages of heavy-duty engines are more frequent than those of electric motors or steam turbines. 

Lubrication skid. The gas turbine lubrication skid is usually independent of the steam turbine skid as the lubrication oil is usually synthetic due to the high temperatures in the gas turbine. Another reason is due to water contamination of the lubrication oil from the steam turbine. It is advisable to have the lubrication system be totally independent. The gas turbine lubrication skid would report to the gas turbine controller. Since the lubrication system is also used for providing cooling, it is usually operated for about 20 minutes after the gas turbine is shutdown. The lubrication skid contains at least three pumps, two pumps in which each can provide the head required and a third pump, which is usually recommended to be a DC drive for emergency use. These pumps and their control fall under the drive level hierarchy. 

The lubricating oil system for a turbine is very important and is nearly always provided with a dual pumping arrangement. One pump can be driven directly off the turbine shaft and the other by separate electric motor or steam turbine. In another arrangement, one pump can be separately electric driven and the other separately steam turbine driven. Twin coolers are often provided in the dual system to... 

The lubricants generally specified for conventional gas turbines invariably fall within the same classification as those used for steam turbines and are often categorized as turbine oils . In those cases where an aircraft type gas turbine has been adapted for industrial use the lubricant is vitally important to their correct operation. Specifications have been rigidly laid down after the most exhaustive tests, and it would be unwise, even foolhardy, to depart from the manufacturers recommendations. No economic gain would result from the use of cheaper, but less efficient, lubricants. 

The compressor speed may be reduced by two-speed electric motors or by electronic variation of the motor speed, down to a lower limit dictated by the inbuilt lubrication system. Many highspeed industrial machines are still driven by steam turbines and this gives the opportunity for speed control within the limits of the prime mover. 

An alternative reaction mechanism to Reactions (4.31) and (4.32) has been suggested concerning how sterically hindered phenols act as antioxidants for lubricants [27]. Based on the fate of 2,6-di-ferft fl/7-butyl-p-cresol in a turbine oil used in a conventional steam turbine, it was concluded that there is a strong possibility that this phenol is consumed not through the inhibition of oxidation, Reactions (4.31) and (4.32), but via direct oxidation with oxygen. Reaction sequence (4.33) ... 

Until the 1990s, any discussion concerning the lubrication of marine engines would have included steam turbines but, due to the rapid escalation of fuel prices in the late 1970s, their use has been virtually discontinued. The improved design and... 

Water in Petroleum Steam Turbine Oils As before, where water was observed to respond differently in high detergent/dispersant petroleum oils when compared to synthetic polyol ester oils, water also shows a different IR response in lubricants and hydraulic oils containing emulsifier additives. The response is typified by a constant... 

R. T. Mookken, D. Saxena, B. Basu, S. Satapathy, S. P. Srivastava, and A. K. Bhatnagar, Dependence of Oxidation Stability of Steam Turbine Oil on Base Oil Composition, Lubrication Engineering, October 19-24 (1997). 

The worldwide annual production of molybdenum amounts to 100000 tons, most of which is used for the production of alloys. The addition of molybdenum to steel alloys increases their strength and thermal resistance, and also reduces their corrosion potential (gas and steam turbines in power generation, missiles, aircraft). Metallic molybdenum enhances the adherence of siliceous material to metals therefore, molybdenum is useful in metal-ceramic composites. Molybdenum compounds are also used in some chemical products (which may lead to wastes) such as catalysts, flame retardants, smoke repressants, lubricants, and molybdenum pigments. 

Compressors, axial 15-stage with steam turbine drive, base plate and lubrication. 

However, metallic detergents, such as calcium sulfonate, are often used as rust inhibitors to prevent or reduce rusting on the metal parts. Moisture due to machine operating conditions, for example in circulating systems of steam turbines, steel mills, and paper machines, may be present either as free water or as entrainment in the lubricant. Rust inhibitors function by formation of a protective oil film on the surfaces [25] the film effectively separates the water from the metal surfaces. 

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... 

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