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TYPES OF LUBRICATION : TYPES OF LUBRICATION FLUID OR HYDRODYNAMIC LUBRICATION THIN FILM OR BOUNDRY LUBRICATION EXTREME PRESSURE LUBRICATION HYDRODYNAMIC : HYDRODYNAMIC Here a thick film of a lubricating oil is interposed between sliding surfaces to avoid direct metal to metal contact BOUNDRY LUBRICATION : BOUNDRY LUBRICATION When a complete fluid film does not develop between potentially rubbing surfaces, the film thickness may be reduced to permit momentary dry contact between wear surface high points or asperities. EXTREME PRESSURE : EXTREME PRESSURE In this case machines operate at high pressure and high temperature and speed hence, ordinary lubricants cannot stick to metal surface so additives which are organic compounds containing sulphur chlorine and phophate TYPES OF LUBRICANTS : TYPES OF LUBRICANTS SOLID LUBRICANTS SEMI-SOLID LUBRICANTS LIQUID LUBRICANTS EMULSION LUBRICANTS SOLID : SOLID GRAPHITE Graphite is best suited for lubrication in a regular atmosphere. Water vapor is a necessary component for graphite lubrication. The adsorption of water reduces the bonding energy between the hexagonal planes of the graphite to a lower level than the adhesion energy between a substrate and the graphite. Because water vapor is a requirement for lubrication, graphite is not effective in vacuum. MOLYBDENUM DI-SULPHIDE MoS2 is a mined material found in the thin veins within granite and highly refined in order to achieve a purity suitable for lubricants. Just like graphite has MoS2 a hexagonal crystal structure with the intrinsic property of easy shear. MoS2 lubrication performance often exceeds that of graphite and is effective in vacuum as well whereas graphite does not. PROPERTIES OF LUBRICANTS : PROPERTIES OF LUBRICANTS VISCOSITY INDEX OILINESS VOLATILITY FLASHAND FIRE POINT CLOUD POINT AND POUR POINT EMULSIFICATON CARBON RESIDUE ANILINE POINT SAPONIFICATION NUMBER VISCOSITY INDEX : VISCOSITY INDEX The viscosity index (V.I.) of an oil is a number that indicates the effect of temperature changes on the viscosity of the oil. A low V.I. signifies relatively large change of viscosity With changes of temperature. In other words, the oil becomes extremely thin at high temperatures and extremely thick at low temperatures. On the other hand, a high V.I. signifies relatively little change in viscosity over a wide temperature range. FLASH POINT AND FIRE POINT : FLASH POINT AND FIRE POINT The flash point is the lowest temperature to which a lubricant must be heated before its vapor, when mixed with air, will ignite but not continue to burn. The fire point is the temperature at which lubricant combustion will be sustained. The flash and fire points are useful in determining a lubricant’s volatility and fire resistance. CLOUD AND POUR POINT : CLOUD AND POUR POINT The pour point is the lowest temperature at which an oil will flow. This property is crucial for oils that must flow at low temperatures. A commonly used rule of thumb when selecting oils is to ensure that the pour point is at least 10°C (20°F) lower than the lowest anticipated ambient temperature. The cloud point is the temperature at which dissolved solids in the oil, such as paraffin wax, begin to form and separate from the oil. As the temperature drops, wax crystallizes and becomes visible. Certain oils must be maintained at temperatures above the cloud point to prevent clogging of filters. THANK YOU : THANK YOU You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.