Course: B.Tech. Subject: Engineering Chemistry Unit : V ( B )

1. Course:B.Tech. Subject: EngineeringChemistry Unit:V (B)

2. DEFINITION:LUBRICANTS • A lubricant is substance (often liquid) introduced between two moving surfacesto reduce the friction betweenthem. • Fluid whichisintroduced in between moving parts in order to reduce thefriction, generated heat & wear and tear of machine parts are calledLubricants. • This process of introducing lubricant iscalled • Lubrication.

3. Gear and Transmissionoils AutomotiveOils • Automotive Grease

4. COMPOSITION • Non liquid lubricants containsGrease, powder(dry disulphite), plumbingetc. graphite,Molybdenum Teflontape usedin • Thosenonliquidlubricantsprovide lubricationathighertemp.(upto350 • °C)

5. ADDITIVES USEDIN LUBRICANTS Anti oxidant --- Aromatic amines,Phenols,Sulphides andphosphates Corrosion Inhibitor --- Amino salts andsalts of sulphonicacids Antiwear agents --- Tricresyl phosphate Foam inhibitors ---Glycerols

6. Functions of Lubricants • It acts as a thermal barrier and reduces friction and wear and prevents weldedjoints • Avoids seizure of movingsurfaces • Acts as coolant • Acts as a seal and prevents entry of dust, moisture, & dirt between movingparts • Some lubricants acts as corrosion inhibitors thus reduce operational cost.

7. A good lubricating oilshould • have: • High boilingpoint • AdequateViscosity • Low freezingpoint • High oxidationresist • Non Corrosiveproperties • Good thermalstability 2

8. Types Of Lubrications ThickFilm ThinFilm or Boundary or Extreme Pressure Lubrication FluidFilm or hydrodynamic Lubrication Lubrication

9. This is also calledHydrodynamic • or fluid filmlubrication. • Two sliding metal surfacesare • separated from each other bya o thick film of fluid ( 1000A thick). • The coefficient of friction in such cases is as low as 0.001 to0.03 • Lubricants used : Hydrocarbon Oils. • Provided in delicate instruments such as watches, clocks, light machines like sewing machines, scientific instrumentsetc.

10. • This lubrication is alsocalled BoundaryLubrication. Its used for high load conditions. Very thin film of the lubricant is adsorbed on the surface byphysical or chemical forces orboth. The coefficient of friction is 0.05to 0.15 Lubricants used forboundary • • • • lubrication should have highviscosity index, resistance to heat and oxidation, goodoiliness. Examples are Organic oils, Vegetable oils, Graphite and MoS2, MineralOils etc. •

11. This lubrication is for veryhigh • press/temp/speed slidingsurfaces. • Extreme pressure additives are used along with the lubricants. • Chemicals used are compounds of • Cl, S & P. • These additives form solidsurface films of Cl, S &P. • High melting pointmetal • compounds are goodlubricants. • E.g. graphite is used fordrawing wires made up of mildsteel. • 3

12. Classification of Lubricants Liquid Lubricants SemiSolid Lubricants Synthetic Lubricants Solid Lubricants Eg.MineralOil, Eg.Graphite, Eg.Petroleum jellies PetroleumOil, Molybdenum Disulphideetc. Vegetable Oiletc

13. TYPES OF LUBRICANTS • Solid lubricantse.g Wax, Talc,Mica, Molibdenumdisulphide • Semi solid lubricantse.g. Grease andVaseline • Liquid Lubricantse.g. Mineral oils, Vegetable oils, Animaloils • Synthetic lubricantse.g. Polyglycols,Silicones, • Organic amines, Imines,Amides.

14. FEATURES OF LUBRICANTS • Increase efficiency and reducewear • Dissolving or transporting foreign particlesand distributingheat • Single largest application is in form of Motor Oil, protecting internal combustion engines in motor vehicles and poweredequipments • Another approach is to use ball bearings, roller bearing or air bearings which in turn require internal lubricationthemselves

15. It’s a measure of a fluid’s resistance toflow. • Viscosity of the lubricating oil determines its performance under operatingconditions. • A low viscosity oil is thin and flows easily. • A high viscosity oil is thick and flowsslowly. • As oil heats up it becomes more viscous (Becomesthin) • Too low viscosity of the liquid > Lubricant film cannotbe • maintained between the moving surfaces > Excessivewear. • Too high viscosity of the liquid > Excessivefriction. • Selected Lubricant must be properviscous. • Viscosity is usually expressed in centipoise orcentistoke.

16. Iodine number is the number of Gms equivalent of iodineto amount of ICl absorbed by 100gm ofoil. • Each oil has its specific IodineNumber. • So Iodine Number determines the extent of contaminationof oil. • Low Iodine Number is desirable inoils. • Some oils and their Iodine Numbers are given below: IodineNumber Oil Example >150 Dryingoil Linseed oil, tungoil 100-150 Semidryingoil Castor oil , Soyabeanoil <100 Non-Dryingoil Coconut oil, Oliveoil

17. AnilinepointistheMintempatwhichoilismisciblewithequalamtof • aniline • • Aniline Point is a measure of aromatic content of the lubricatingoil. Low Aniline Point oil have high aromatic content which attacksrubber seals. • • Higher Aniline point means low %age of hydrocarbons(desirable). ThusAnilinePointisusedasanindicationofpossibledeteriorationof rubber sealingetc. Determination of Aniline Point: Homogeneous solution Aniline+ Heated in Testtube sampleoil (equal) Cooled Cloudiness The temperature at which separation of the two phases (Aniline + oil) takesplace is the AnilinePoint.

18. Emulsification is the property of water to get mixed with water easily. • Emulsions can be oil in water emulsion or water in oilemulsion. • A good lubricating oil should form such an emulsion withwater which breaks easily. This property is calleddemulsification. • The time in seconds in which a givenvolumeof oil andwater • separatesoutin distinct layers is called steamdemulsification • number. • A good lubricating oil should have lower demulsificationnumber. • Quicker the oil separates out from the emulsion formed, better is the lubricating oil. • In cutting oils the higher the emulsification number, better the oilis. • This is because the emulsion acts as a coolant as well as alubricant.

19. • Flash Point is the min temp at which the lubricant vaporizes that ignite fora moment when tiny flame is broughtnear. • Fire Point is the Min temp at which the lubricant’s vapours burn constantlyfor 5 seconds when tiny flame is broughtnear. • If flash point < 140°F = Flammableliquids • And if flash point > 140°F =Combustibleliquids. • The flash and fire points are generally determined byusing • Pensky-Marten’sapparatus. • Oil under examination is filled in the oil cup up to themark and heated by the air bath by aburner. • Stirrer is worked b/n tests at a rate of about 1 – 2rev/sec. • Heat is applied so as to raise the oil temp by about5c/min. • The temp at which distinct flash appeared in side the oilcup • is recorded asflashpoint. • The heating is continued to record the firepoint. • 4

20. • Drop Point is the Temperatureat which grease passes from thesemi- solid to the liquid state. So, it determines the upper temp limit for the applicability ofgrease. Determination: • • • Beaker isheated. Temperature israised. Grease sample passes from asemi- solid to a fluidstate. • Temp at which its first dropfalls from the opening is recordedas drop-point. 5

21. Cloud Point is the temp at which the lubricant becomes cloudy or hazy whencooled. • PourPointisthe temp at whichthe lubricant just ceases to flow whencooled. • Both indicates suitability of lubricant in cold conditions and thus must below.

22. It’s the mgs of KOH required to saponify 1 gm ofoil. • Saponification is hydrolysis of an Easter with KOH to give alcohol and Na/K salt ofacid.

23. USES • Other usesare • forcooking, • biomedical applications on human(lubricantsfor • artificialjoints).

24. APPLICATIONS • Automotive Industry-Engine oil,Automatic • transmission fluid, Gearbox fluid, Breakfluids. • Tractor(One lubricant for allsystems) • Other motors(2 stroke engineoil) • Industrial(Hydraulic oils, Air compressor oils, Gas Compressor oils, Gear oils Bearing and circulating system oils, Refrigerator compressor oils) • Aviation • Marine

25. REFERENCES www.motosport.com www.umongo.co.za http://www.vidyarthiplus.in/2012/01/engineering- chemistry1-lubricants.html# www.aimil.com www.machinerylubrication.com Atextbook of Engineering Chemistry byShashi chawla