Efficiency of Lubrication

A survey of the lubrication requirements, usually carried out by the lubricant supplier, can often be the means of significantly reducing the number of oils and greases in a workshop or factory. The efficiency of lubrication may well be increased, and the economies affected are likely to be substantial. 

These solids, when dispersed in lubricating oils, increase the efficiency of lubricants and decrease wear during engine start-up. Particle size must be less than 2 pm in order to pass through the filter and to remain in suspension. 

The effect of lubrication was greatest when clock oils were applied as the lubricant. The poor efficiency of lubrication was found for mineral oil and glycerol. 

Figure 5. Relationship between the efficiency of lubrication and the surface tension of oils for steel/POM microbearings.

The efficiency of lubrication (the ratio of the dry radial wear to the lubricated wear) depends on the surface tension of the lubricants applied. For the POM - based bearings, the relationship is presented in the Figure 5. One can see the very poor efficiency of lubrication with glycerol. This may be due to poor wetting of the polymer material because of the high surface tension of the lubricant and low critical surface tension of the POM material. 

The efficiency of lubrication is better when the surface free energy of the polymer material and the surface tension of the oil are higher. 

Positive di.splaeement pumps normally have some strict tolerance parts. These parts vary with the type and design of the pump. This strict tolerance controls the flow, and the pressure that these pumps can generate. When this tolerance opens or wears by just a few ten thousandths, these pumps lose almost all their efficiency and ability to function. These strict tolerance parts must be changed with a planned certain frequency, ba.sed on the abrasive nature and lubricity of the pumped fluid, to maintain the maximum efficiency of the pump. 

Seal problems can give rise to high leakages and thrust problems. The high leakages reduce the efficiency of the unit and can also lead to contamination of the lubricant. Thrust problems are created by air leakage past seals, causing an unbalance of the thrust forces on the system. 

The plant engineer s objective must be to ensure that plant operates at a profit. If overall efficiency of operation is to be achieved, and the working costs of plant kept within acceptable bounds, time must be set aside for the control and application of lubrication. The evolution of lubricants and their application has continued ever since the beginning of the Industrial Revolution, and as the pattern of industry becomes increasingly more complex, the standard of performance of lubricants becomes progressively more important. 

All machines depend for their accuracy on the strength of their component parts, their bearings and on the type and efficiency of their lubrication systems. Many machine bearings are subjected to extremely heavy shock loads, or intermittent loads, or exposure to unfavorable environmental conditions, yet in spite of this they must always maintain their setting accuracy. 

In piston-type compressors, the oil serves three functions in addition to the main one of lubricating the bearings and cylinders. It helps to seal the fine clearances around piston rings, piston rods and valves, and thus minimizes blow-by of air (which reduces efficiency and can cause overheating). It contributes to cooling by dissipating heat to the walls of the crankcase and it prevents corrosion that would otherwise be caused by moisture condensing from the compressed air. 

Help towards maximum efficiency in the use of lubricants and the equipment in which they are employed ... 

An example of reducing energy consumption in use is found in 4-stroke automobile lubricants.Only about 20-35% of the energy released by the combustion of fuel is turned into useful mechanical work. The rest is lost as heat and friction. Lubricants play an important role in the overall efficiency of the vehicle. 

The first applications of this technique [99] were directed to developing a more sensitive assessment of lubricant efficiency than that offered by the traditional coefficient of lubrication , or R-value (i.e., FL FA ratio). Since then, its use has been extended to provide predictive information on formulation performance [100,101]. Lammens et al. [102] have stressed the importance of ensuring precision and accuracy in such measurements for correct interpretation of the data so produced. 

Other studies have been performed to investigate the effect of surface area and tablet lubricant efficacy. In a comparison study between sodium stearyl fumarate and magnesium stearate, it was found that sodium stearyl fumarate was effective as a lubricant to about the same degree as magnesium stearate [15]. It was also reported that the lubricating properties correlated better to the surface area of the lubricant than to the amount of lubricant used. A micronized lubricant was more efficient than a coarse fraction, and it was suggested that the surface area be standardized to obtain reproducible effects. 

Metal complexes, dialkyl thiophosphates and dialkyl thiocarbamates of Zn, Ni, Ba, and Ca, in particular, are widely used for the stabilization of lubricants [30-32,34]. At moderate temperatures (350 400 K), these inhibitors are less efficient than phenols, but they are more potent at higher temperatures (430 480 K). The sophisticated mechanism of action of these antioxidants involves their reactions with hydroperoxide. The interaction of hydroperoxide with metal dialkyl thiophosphates induces a cascade of reactions [5,66-69],... 

The oxidation of olefins can result in the formation of organic hydroperoxides. These compounds readily decompose to form alcohols, carbonyl compounds, and other oxidized species. These oxidized hydrocarbons can further react to form highly cross-linked, oxygen-rich materials. Some of these species can adhere to metal surfaces to form a hard vamishlike film or coating on metal parts. This varnish can act as a site for further deposition and eventual corrosion of metal. In severe cases, varnish can interfere with the hydrodynamic lubrication of moving metal parts and efficiency of component operation. 

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