Safety tip…• Grinding dust from abrasive wheels is madeup of extremely fine particles of the metal andthe wheel and can be very dangerous to yourhealth.Avoid inhaling such abrasive particles as muchas possible.
Definition• Lubrication is the process, or techniqueemployed to diminish friction betweensurfaces in close proximity, and movingrelative to each other, by interposing asubstance between them.• The substance interposed is called lubricant.
Lubricant film thickness1/100th of a paper sheetWithstanding pressure of 10 cars on afinger nail
Types (According to physical state)LubricantsSolid Semi-solid Liquide.g. Graphite e.g. Grease e.g. petroleum oil
• It’s a measure of a fluid’s resistance to flow. Viscosity of the lubricating oildetermines its performance under operating conditions.• Too viscosity oil is thin and cannot stop friction.• Too high viscosity oil is thick and has poor flow properties.Parameters of lubricants1.ViscoityViscosity : application :( at 400C) (indication)10 – 25 cSt low temp, (very) high speed70 – 200 cSt standard applications300 – 1000 cSt (very) heavy load, (very) low speed
VISCOSITY INDEX :• The rate at which viscosity of a lubricant changes withtemperature is measured by a scale called Viscosity Index.• It is the decrease in viscosity of oil per degree rise in tempbetween 38 °C & 99°C.• Higher Viscosity Index means less variation of viscosity withtemperature.Factor affecting Viscosity :• Temperature : Viscosity decreases with increases in temperature.• Load : Viscosity increases with increases in load.• Speed/shear : Viscosity decreases with increases in speed.
Determination of Viscosity Index
Determination of VI (contd.)• First the viscosity of the oil under test is determined at 38 °C Let it be U• Then viscosity of 100 VI reference oil be H• Then viscosity of 0 VI reference oil be L• The values of 100 VI & 0VI oils is obtained from ASTM D2270.
• Iodine number is the number of Grams equivalent of iodine absorbed by 100gmof oil.• Each oil has its specific Iodine Number.• Iodine Number determines the extent of unsaturation present in the oil.Low Iodine Number is desirable in oils.2. Iodine number
• Aniline point of an oil is defined as the minimum temperature at whichequal volumes of aniline(C6H5NH2) and the oil are miscible to form asingle phase upon mixing .• Aniline Point is a measure of aromatic content of the lubricating oil.• Low Aniline Point oil have high aromatic content which attacks rubberseals.• Aniline Point is used as an indication of possible deterioration of rubbersealing etc.A good Lubricants should have higher Aniline point3. Aniline point
• Demulsification number defined as the number of seconds required for an oilto separate from water after it has been emulsified under specifiedconditions.• A good lubricating oil should form such an emulsion with water which breaks easily.This property is called demulsification.• Quicker the oil separates out from the emulsion formed, better is the lubricating oil.A good lubricating oil should have lower demulsification number.4.Demulsification number
• Flash Point is the min temp at which the lubricant’s vapors ignite for a momentwhen tiny flame is brought near.• Fire Point is the Min temp at which the lubricant’s vapours burn constantly for 5seconds when tiny flame is brought near.• Fire point = flashpoint + 5°C to 400 °C• If flash point < 37.8 °C= Flammable liquidsAnd if flash point >37.8 °C =Combustible liquids.For ease of storage and transportation lubricants with higherflash point are preferred.5. Flash point & Fire point
• Drop Point is the Temperature at which grease passes from the semi-solid state tothe liquid state.• It determines the upper temp limit for the applicability of grease.• It is applicable for grease only.Higher Drop point is preferred in grease6. Drop point
7.Neutralisation number• Neutralization number can be either a total acid number (TAN) or totalbase number (TBN)• Total Acid Number is a measure of the amount of potassium hydroxiderequired to neutralize the acid contained in a lubricant.• TAN indicates age and Oxidation extent in the oil.• Total Base Number is a measure of reserve alkalinity in the oil. It ismeasured by mg of KOH per gram of oil.• Alkali is added in the oil as a corrosion inhibitor.TBN indicates corrosionresistivity of the oil.Higher TBN or Lower TAN is preferred in an oil.
• Cloud Point is the temp at which the lubricant becomes cloudy or hazy whencooled.• Lubricating oils used in capillary feed systems should have low cloud points,otherwise impurities will clog the capillary.• Pour Point is the temp at which the lubricant just ceases to flow when cooled.• Pour point of wax can be lowered by dewaxing , addition of suitable pourpoint depressant, by removing the viscous constituent of the oil.Lower Cloud Point and Pour point is preferred in a Lubricant.8.Cloud point and Pour point
Desirable properties• High Chemical stability• High thermal stability• High boiling point• Low freezing point• Non-radioactive• Ease of availability• Economic viability
Additives• Additives are the substances added to a lubricant to enhanceexisting properties, suppress undesirable properties or impartnew properties so as to increase the range of applicability.• These are classified along functional capabilities as :» For chemical stability» For viscosity» For contamination control» For lubricity
Additives for chemical stabilityDetergents Metallo-Organiccompounds of Sodium,Calcium and MagnesiumChemically react withsludge to neutralize themand keep them solubleAnti-Oxidants Aromatic Amines,sulfurized phenolsDecompose peroxides,Terminates free-radicalreactionsRust-inhibitors Metal phenolates Provide protective filmNeutralize corrosive acids
Additives for ViscosityVI improvers Polymers and copolymersof olefinsPolymers expand withincreasing temperaturesThis counteract oil thinningPour pointdepressantsAlkylated naphthalene Modify wax crystalformation to reduceinterlocking
Additives for contamination controlDispersants (anti-coagulants)Alkylsuccinimide Contaminants are bondedby polar attraction todispersant molecules.Prevented fromagglomeratingKept in suspension due tosolubility of dispersantAnti-foaming agents Organic copolymers Reduce Surface tension tospeed collapse of foamSeal swell agents Aromatic hydro carbons Chemical reaction withgasket to cause slight swell,resulting in tight seal
Additives for LubricityAnti Wear Organic Phosphates Chemical reaction withmetal surface and forms afilm. Prevents metal-to-metal contactFriction modifiers Organic fatty acids andamides.Preferential adsorption ofsurface active materialsExtreme pressureagentsorganic sulfur and chlorinecompoundsChemical action to form asurface film
Lubricant NomenclatureFOR LUBRICATING OIL• According to ISO 3448 standards lubricating oils are namedaccording to their Viscosity grades.• The Viscosity grade is suffixedFOR GREASE• Greases are given NLGI number in accordance with ASTM D-217 test.
NLGI Grades as per ASTM D-217 TEST
Lab Tests - for lubricantsASTM D 445ASTM D 2250ASTM D 97ASTM D 92ASTM D 664ASTM D 217Kinematic viscosityViscosity indexPour PointFlash PointTotal Base Number (TBN)NLGI numbers
ExampleSERVOMESH-320• Viscosity :320-350cst(At 40°C)• Viscosity Index : 90• Flash Point : 232 °C• Pour point : -3°CUSES:- Gear boxesSERVOSYSTEM46• Viscosity : 43-48cst (At 40 °C)• Viscosity Index : 98• Flash Point :200°C• Pour point : -15°C• Demulsification no : 20minsUSES :-Pumps