Lubricants performance characteristics

However sophisticated such models become, their origins remain in mechanical dynamics and fluid film lubrication analyses. As such they can only perform realistic predictions when provided with component geometry and surface texture after running-in and the local lubricant performance characteristics at the engine running time of interest. Unfortunately such data is not readily available to the engine designer. 

High Water-Base Fluids. These water-base fluids have very high fire resistance because as Httle as 5% of the fluid is combustible. Water alone, however, lacks several important quaUties as a hydrauHc fluid. The viscosity is so low that it has Httle value as a sealing fluid water has Httle or no abiHty to prevent wear or reduce friction under boundary-lubrication conditions and water cannot prevent mst. These shortcomings can be alleviated in part by use of suitable additives. Several types of high water-based fluids commercially available are soluble oils, ie, od-in-water emulsions microemulsions tme water solutions, called synthetics and thickened microemulsions. These last have viscosity and performance characteristics similar to other types of hydrauHc fluids. 

Figure 16-16 shows the performance characteristic of a split-shaft turbine where the only power output limitation is the maximum allowable temperature at the inlet of the turbine section. In actual practice a torque limit, increased exhaust temperature, loss of turbine efficiency, aud/or a lubrication problem on the driven equipment usually preclude operating at very low power turbine speeds. The useful characteristic of the split-shaft engine is its ability to supply a more or less constant horsepower output over a wide range of power turbine speeds. The air compressor essentially sets a power level and the output shaft attains a speed to pnivide the required torque balance. Compressors, pumps, and various mechanical tinvc systems make very good applications for split-shaft designs. 

The performance characteristics of a lubricating oil depend on its origin and on the refining processes employed, and in order to ensure consistent properties these are varied as little as possible. Some aero-engine builders insist on a complete re-evaluation of a lubricant, costing many thousands of pounds, whenever there is a change of source (crude) or refining process. 

NOTE The orientation of surfactant molecules at an interface (water-solvent, water-gas, water-metal) confers performance characteristics on the molecule that permit it to be employed as an emulsifier, demulsifier, wetting agent, antifoam, lubricant, or other agent. 

Recently they have acquired practical importance as so-called multifunctional additives for improving performance characteristics of lubricant oils used in intensive operation engines. 

Betts, S., Dackow, J. and Murray, S.F., Performance Characteristics of Self-Lubricating Polyimide Composites, Proc. 2nd ASLE Inti. Conf. on Solid Lubrication, Denver, Colorado, (15-18 Aug. 1978), ASLE SP-6, p. 195. 

The complete line of NEODOL surfactants consists of some 15 individual products based on alcohols in the C9 to Cl 5 range with distinctive performance characteristics which make them exceptionally effective in various textile applications. NEODOL surfactants can therefore be selected for specific high performance qualities in traditional textile applications such as lubrication, desizing, scouring, mercer-ization, printing and dyeing—as well as for the newer applications such as foam finishing and foam mercerization. 

Another method (ASTM D-893) covers the determination of pentane-and toluene-insoluble constituents in used lubricating oils and can be applied to asphalt. Pentane-insoluble constituents include oil-insoluble materials, and toluene-insoluble constituents can come from external contamination and highly carbonized materials from degradation. A significant change in pentane- or toluene=insoluble constituents indicates a change in asphalt properties that could lead to problems in service. The insoluble constituents measured can also assist in evaluating the performance characteristics of asphalt. 

Polybutenes combine effective viscosity control with the ability to deliver a number of key benefits and performance characteristics to an extensive range of automotive and industrial lubricants. Limitations in volatility and oxidation resistance limit the use of low-viscosity polybutenes in some of the more traditional base oil applications. 

Organophosphorus compounds Phosphites are the main organophosphorus compounds used to control oxidative degradation of lubricants. They eliminate hydroperoxides, peroxy and alkoxy radicals, retard the darkening of lubricants over time and also limit photodegradation. These performance characteristics may be of importance for polyalphaolefins, hydrocracked or severely hydrotreated base stocks and white oils. 

Automatic transmission fluids, ATFs Frictional behaviour is a key performance characteristic of an ATF. During operational lifetime, thermal and oxidation byproducts can form in the lubricant. These have the potential to fill the porous holes found in the surface of the transmission, causing the clutch plates to slip. A dispersant is necessary to keep these by-products suspended in the oil, and typical treat rates vary between 1 and 6%. Additionally, the dispersant can positively affect friction if chosen correctly. A number of reasons for this have been proposed, including... 

Lubricant base oils must meet minimum performance characteristics of viscosity, viscosity index, pour point and volatility, all of which must meet required standards. When dealing with re-refined base oils, additional characteristics such as colour and odour must also be considered. These properties, of dark colour and odour, are readily perceived by customers and consumers as representing deficiencies in quality. Many examples of re-refined base oils have a definite, characteristic, oxidised or cracked odour which may be totally unacceptable in some countries and markets. Table 15.2 gives quality guidelines for the acceptance of re-refined 150 and 500 base oils. 

Both quality and process control should be able to produce a product of known and consistent quality, suitable for use as a lubricant base stock. In past practice, however, oils that can meet the required performance characteristics have tended not to be readily available and have historically been expensive. For these reasons, the use of re-refined oils as a lubricant base oil was not considered to represent a viable alternative to virgin mineral base oils of consistent quality when these are readily available. More recently, the quality of re-refined base oils has increased to a high level, for some cases up to Gp. II quality, and in volume quantity. In addition, the substantially increased price of crude oil, and its associated products, has made re-refining of used lubricant much more economically viable. The alternative route of using the used lubricant as a fuel directly or as a fuel extender is now much more restricted and controlled by environmental legislative authorisations and is also much less viable economically. 

Defined performance standards defined similarly to the tripartite system, where SAL, API and ASTM perform their previous traditional roles. If ASTM cannot achieve consensus, there is provision for ILSAC to take over. The system defines physical, chemical and performance characteristics of engine lubricants for API SX and CX specifications. 

Lubricants produced in a refinery are high-grade products that retain little or no residual metal from the crude oil. The demand for improved performance characteristics for lubricants has been met by... 

Epoxidised allyl soyate resin (a mixture of epoxidised fatty acid esters) copolymerised with the base Shell Epon epoxy resin is used as matrix for glass fibre reinforced composite, which is prepared using a Durapul 6000 Labstar Pultrusion machine. The lubricating quality of soybean oil-based resin significantly reduces the pulling force which improves the structural performance characteristics of the composites. Curing is carried out in an oven at 80°C for one hour, followed by heating to 177 C for 1.5 h. 

The term lubricants is used by a variety of specialists to cover a range of chemicals that are added to plastics to improve a variety of performance characteristics in processing or in final properties. When they are used to improve processing, the field may expand to include other types of processing aids. When they are used to improve final properties, the field may expand to include other properties beyond lubrication. 

From the viewpoint of fundamental research, pure chemical entities should be used as additives. However, taking into account the application of the results obtained, the tendency was to use low-cost lubricating substances having certain performance characteristics. Therefore, the decision was made to use products manufactured on a large industrial scale. Such products are mixtures of compounds of similar structure. This results from the fact that the reactants in the case of such compounds are, for example, vegetable oils whose composition can vary. However, such an approach to investigations requires each time a detailed physicochemical analysis of the compositions obtained. 

Others. Lubricants such as graphite and molybdenum disulfide, used to obtain different performance characteristics. 

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