Updated Lubricants.pdf

EN3BS09 Engineering Chemistry Syllabus Unit-I Lubricants Introduction, Classification of lubricants, Mechanism of lubrication, Properties and Testing of lubricating oils (Flash and Fire point, Cloud and Pour point, Viscosity and Viscosity Index, Neutralization number, Saponification Number, Steam Emulsification Number, Aniline Point, Iodine Value), Numerical problems based on testing methods. Unit -II Polymer Introduction and Classification of polymer, Preparation, Properties and Uses of the following- Polythene, PVC, Teflon, Nylon 66, Bakelite, Silicone resin, Natural and Synthetic Rubber, Vulcanization of Rubber, Biopolymers, Biodegradable polymers. Unit -III New Engineering Materials Introduction, Properties and Applications of - Superconductors, Optical Fiber, Fullerenes, Graphene, Carbon nanotubes, Nanowires. Syllabus Unit -IV Instrumental Techniques in Chemical Analysis Spectroscopy, Electromagnetic spectrum, Beer & Lambert's Law and its limitations, Principle, Instrumentation and Applications of- UV-Visible Spectroscopy, IR Spectroscopy, Gas Chromatography. Unit- V Electrochemistry Concept of Enthalpy, Entropy and Free energy, EMF, Applications of EMF measurements, Corrosion- Definition, Types, Causes and Protection from corrosion. Text Books – Preeti Jain, Anjali Soni, Jeetendra Bhawsar, A text book of Engineering Chemistry, 1st edition, Manthan Publication, 2016. – Preeti Jain, S L Garg, Engineering Chemisty, 4th edition, Variety Publication. – Shashi Chawla, Engineering Chemistry, 11th edition, Dhanpat Rai Publications. Reference Books P C Jain, Monika Jain, Engineering Chemistry, Dhanpat Rai Publications. S. S. Dara, A Text Book of Engineering Chemistry, S. Chand & Company. Lubricants By Dr. Deepti Pal Assistant Professor MGI, Indore What is Lubrication In any machines, the surface of rolling part or moving part or sliding part rub against each other and this produces friction. As a result of which the surface of the rolling/moving part gets heated up. This cause a lot of wear and tear on the surface of the moving part and thus causes the loss in the working efficiency of machine. Thus to reduce the ill-effect of friction, a thin layer of suitable substance (fluid) is introduced between the moving part. Definition The fluid substance introduced between the moving or sliding parts of a machine in order to reduce the friction are named as Lubricant. The process of reducing the friction and minimizing the energy loss by the application of lubricants in between the moving parts of machine is known as Lubrication. Why lubrication is required Friction/wear. Heat generation. Increasing the life of machines. Reduces energy consumption. Materials protection. Sealing. Function of lubricant Reduces the friction. Avoids direct contact b/w the rubbing surfaces, thus reduces surface deformation, wear and tear, minimize heavy damages. Reduces heat energy loss and hence act as a coolant. Reduces waste of energy as a result the efficiency and the life of the machine increases. Reduces expansion of metal occurred by local frictional heat. Function of lubricant Lubricant keeps out dirt, entraps the foreign particles of dirt and prevents damage of smooth surface. Act as a cleaning agent and as a scavenger, to wash off and transport solid particles produced in combustion & wear. Act as a seal- when applied b/w piston and cylinder wall (internal combustion engine). Prevents rust and corrosion and therefore reduces running and maintenance cost of the machines. Decreases the liberation of frictional heat and hence avoid seizure. Characteristic of lubricant Viscosity – for upright cushioning and smooth operation, good viscosity is required. Film strength – good film strength avoids metal contact and scoring b/w the gear teeth. Lubricity (oiliness) – necessary to reduce friction. Adhesion – helps and prevent loss of lubrication, due to throw-off associated with gravity or centrifugal forces especially at high rate. Temperature – normal oil operating temp. ranges from 50-550C above ambient. Oils operating at high temp. requires good viscosity and high resistance to oxidation and foaming. Chemical stability and oxidation resistance – prevents thickening 7 formation of varnish or sludge. Extreme pressure protection – provides additional galling and welding protection for heavily leaded gears, when lubricant film thickness fails. Mechanism of lubrication Classified into three types 1. Fluid film/hydrodynamic/thick film lubrication 2. Boundary lubrication/thin film lubrication 3. Extreme pressure lubrication 1. Hydrodynamic Lubrication Also called as thick film or fluid film lubrication. The lubricant in this type of mechanism are viscous and produces liquid pressure in the lubricant wedge, which keeps the two surfaces separated. A thick film (at least 1000Å) of liquid fluid separates the two moving/sliding surfaces. The load is taken completely by the oil film. The lubricant fills the irregularities of the sliding/moving surfaces and thus prevents direct contacts b/w the metal surfaces and hence wear is minimized. The coefficient of friction in such cases is as low as 0.001 to 0.03 Conditions where HDL is used Temperature – Room temperature Pressure – Atmospheric pressure Load – Low Speed – Slow Application Delicate instruments like watches. Light machines like sewing machines. Scientific instruments. Clocks, guns etc. Types of lubricant used Lubricants used are hydrocarbon oil blended with selected long chain polymer. Anti-oxidants like amino phenols are added to maintain suitable viscosity. Organometallic detergents are added to keep away the carbon particles in hydrodynamic lubrication. Hydrodynamic lubrication is an excellent method of lubrication since the coefficient of fraction is as low as 0.001 and there is no wear b/w the moving/sliding parts. 2. Boundary Lubrication Also known as thin film lubrication. The lubricant molecules adsorbs on an interface b/w the two asperities by physical and chemical force. They react with the metal surface and convert the metals surface to metal oxides. Used for high load condition, where the load is carried by the lubricant by both the metal surfaces. Coefficient of friction is 0.05 to 0.15. Conditions where boundary lubrication is used Temperature – High/moderate temperature Pressure – High/moderate pressure Load – Moderate Speed – Fast/moderate. Application In low speed cases or starting and stopping of rotating or sliding motion (hinge joints, low speed sleeve bearing etc.). In high temp. cases (steam engine or IC engine cylinder). In high pressure cases (in roller bearing, gears etc.). Types of lubricant used Graphite and MoS2 (Molybdenum disulphide) Mineral oils mixed with 0.1-0.5% of boundary agents like fatty acid, alcohol, and amines. Vegetable and animal oils and their soap. The most common and widely used boundary lubricant is Grease – as it has most desirable properties of boundary lubricant. It dissipate heat easily, form a protective barrier for the surface, prevent dirt, dust and act as a corrosive agent. Best boundary lubricants are solid with long chains of high inter-chain attraction, low shear resistance (so as to slip easily) and a high temp. tolerance. These lubricant forms a thin film (1-2 molecule thickness) over the metal surfaces and adhere strongly to the surface. It provides enough protection to prevent metal-metal contact. Some examples In low speed cases or starting and stopping of rotating or sliding motion (like hinge joints, low speed sleeve bearing etc.). In high temperature cases (like steam engine or IC engine cylinder). In high pressure cases (in roller bearing, gears etc.). 3. Extreme Pressure Lubrication When the moving or sliding surfaces are under very high pressure and speed, a high local temp. is attained and under such circumstances, the liquid lubricants fail to stick and may decompose, or even vaporize. If the load or pressure is too high, the contact b/w the metal surfaces increases. If the temp. is too high, deformation, seizures, welding etc. takes place to a large scale. Therefore, to over come this extreme pressure situations some special additives are added to the lubricants (mineral oil) and are known extreme pressure additives. Conditions under which EPL is used Temperature – Very high temperature (more than 800℃). Pressure – Very high pressure. Load – Heavy load. Speed- Fast. Important additives are organic compounds having active radicals or groups such as Chlorine (as in chlorinated ester), Sulphur (as in sulphurized oil), or Phosphorus (as in tri cresyl phosphate). Importance of Extreme pressure additive These compounds react with metallic surface, at prevailing high temp., to form metallic chlorides, sulphides or phosphides. These metallic compounds possess high melting points (e.g. iron chloride and iron sulfide melts at 650℃ and 1,100℃ respectively) and act as good lubricant. These additives forms a more durable film on the metal surfaces and thus capable of hold out against (withstand) high pressure and high temperature. Some examples of extreme pressure additives are (1) compds. containing oxygen (fatty acids, ketones, esters etc., (2) compounds containing sulphur or sulphur & oxygen, (3)chlorinated wax, (4) sulphurized fats, (5) sulphurized olefins, (6) organic compds. Containing both chlorine and sulphur. Some examples Wire drawing of titanium requires chloride containing additive – which react with the stable oxide film on the metal surface. In cutting fluids, lubricant used may contain a hydrocarbon, small amount of fatty acids of organic chloride or sulphide. In heavy duty automobiles, automotive hypoid gears – high pressure and rubbing actions are encountered. In the axles boxes of train. CLASSIFICATION OF LUBRICANTS Classified into 4 types depending upon physical state. (A) Liquid lubricant (C) Solid lubricant (1) Animal/vegetable oil. (1) Structural lubricant (2) Mineral oil. (2) Mechanical Lubricant (3) Blended oil (3) Soap (4) Chemically active lubricant (B) Semisolid lubricant (5) Refractories, ceramics and glass (1) Calcium based grease. (2) Soda based grease. (D) Synthetic lubricants (3) Lithium based grease. (4) Axle grease. (A) Liquid Lubricant or Lubricating Oil Further classified as (a) Animal/Vegetable oil, (b) Mineral oil, & (c) Blended oil. A good lubricating oil posses:- 1. High boiling point 2. High freezing point. 3. Adequate viscosity for particular work. 4. High resistance to heat. 5. High resistance to corrosion. 6. Must be stable to decompose at high temperature. (a) Animal / Vegetable oil These are primarily triglyceride esters, derived from animals and plants. For lubricant base oil use, vegetable derived materials are preferred. Common ones for vegetable oils are – high oleic palm oil (delicte scientific instruments), sunflower seed oil, rapeseed oil, castor oil (racing cars)etc. Common ones for animal oil are – tall oil, lard oil, neet foot oil, sperm oil (used in ordinary machine parts, sewing machines etc.). These oil possess oiliness and hence they stick to the surface of machine parts ; under high temperature and load. Many vegetable oils are often hydrolyzed to yield the acids which are subsequently combined selectively to form special synthetic esters. Limitations of animal/vegetable oil They are costly. They get oxidized easily and form acids and gummy compounds. They get thickened in the presence of air. They get hydrolyzed in the presence of water and moisture. Preparation of Animal oil and Vegetable oil Animal oils are extracted from crude fat by rendering process in which the tissue is broken down by treatment with steam or combined action of steam & water. Vegetable oils are obtained by crushing the seeds and by rendering process. Before use, both animal and vegetable oil requires further treatment. (b) Mineral or Petroleum oils These are basically lower molecular wt. hydrocarbons with 12-50 carbon atoms. Their viscosity increases with the length of the hydrocarbon. Crude petroleum oil contains impurities like wax, asphalt etc., which must be removed before application. Otherwise these impurities may create a number of problems like – wax raises the pour point and makes lubricant unfit for low temp. use. Asphalt undergoes decomposition at high temperature and causes carbon deposition and sludge formation. Certain constituents get oxidized under working conditions and form sludge. (c) Blended oils or compound oils To produce the desired characteristics in lubricant, numerous additives are added in certain amount. The oil thus obtained are known as blended or compound oil. Two types of additives are available Chemically active additives – reacts chemically and from metal protective films (a) anti oxidants – prevent oxidation (thiols, polyphenols, aromatic amines), (b) corrosion inhibitor- stops or slow downs corrosion of metal (hexamine, sodium nitrate, chromates, phosphates etc.), (c) anti wear/extreme pressure agents – prevent metal-metal contact (zinc, phosphorous compound), (d) friction modifiers – reduces surface friction (glycerol mono-oleate, phosphoric acid esters, organic fatty acids), (e) dispersants – keep insoluble contaminants dispersed in lubricants (alkyl thio phosphonate), (f) anti foamants – prevents foam formation (silicon polymers), (g) Metal deactivators – used to stabilized fluids by deactivating metal ions (N, N’-disalicylidene-1,2- propanediamines -used in jet fuels) Chemically inert additives – improves physical properties of lubricant (i)Viscosity modifier – improves viscosity (polymers and co-polymers of olefins). (ii) Pour point depressants – reduce interlocking, enables lubricant to flow at low temperature (polymethacrylates, phenolic polymers, alkylated naphthalene). (B) Semi solid Lubricant or Grease When a thickening agent is added to lubricating oil, the substance so achieved is called as Grease. The lubricating oil may be petroleum oil or synthetic oil and the thickener may consist of soap of sodium, calcium, barium, aluminium or lithium etc. Non-soapy thickeners are carbon black, silica gel, poly urea, synthetic polymer, bentonite clay etc. which improves the heat resistance of a lubricant. Grease are prepared by saponification of fat with alkali (like caustic soda, lime etc.)followed by mixing hot lubricating oil. Consistency of finished grease is determined by total amount of the mineral oil. Properties and application of Grease It gives higher shear or fractional resistance than oils- can support much heavier loads at lower speed. Coefficient of friction of grease is more than oil, its better to use oil instead of greases. Greases normally work at low temp. and they cannot dissipate heat effectively from bearings. Thus grease lubricated bearings works at relatively low temperature as compared to the oil lubricated bearing. Applications Used where oil cannot retain its place due to high load, low speed, intermittent operation, sudden jerks etc., e.g. Rail axel box. In bearings and gears that work at high temperature. Grease are more resistant to contamination by dirt or moisture. They are used when bearing needs to be sealed against entry of dust, dirt etc. Used where dripping or spurting of oil is undesirable e.g. paper, textile, edible etc. Classification of Grease On the basis of soap used, grease are classified into four types. 1. Soda based grease- prepared by adding sodium soap in petroleum oil. It is water soluble, can be used up to 175℃, mostly used in ball bearings. 2. Calcium based grease – prepared by adding calcium hydroxide to hot oil. Most economic grease, resistant to water, used up to 80℃, used in caterpillar treads, tractors, water pumps. 3. Lithium based grease – prepared by mixing lithium soaps in petroleum oil. Resistant to water, can work at high temp., stable on storage, high oxidation and mechanical stability, used in aircrafts at extreme height and low temp. (-55℃), high melting points (150℃). 4. Axle grease – prepared by adding lime to resin and fatty oil. Filler like mica, talc are added to grease. Have water resistance property, used for equipment's working at low speeds and high loads. (C) Solid Lubricants Solid lubricants are used in such conditions where Machines are operating at very high loads and low speed. Where a liquid or a semi solid lubricant film cannot be maintained. Contamination of lubricating oil is undesirable as in the case of commutator blades of electric motor and generators. Where the lubricated parts are not easily accessible. Where the operating temperature and pressures are too high. These are used either in dry powder from or mixed with water or oil. The coefficient of friction is between 0.005-0.01. five types if solid lubricant are available. Types of Solid Lubricants (i) Structural lubricants – widely used, includes graphite, MoS2, talc, vermiculite. Their property is due to layer lattice structure. Used in air compressor, lathes, general machine shop work, food stuff industry, railway track joints, open gear chains, IC engines, etc. (ii) Mechanical lubricants – include plastics and metals. (iii)Soaps – forms compounds with metal surface by the fatty acids and metal (iv)Chemically active lubricants – includes extreme pressure additive and other chemicals. (v) Refractories, ceramics and glass – works at higher temperature, mostly used in rocketry and defense programs. (D) Synthetic Lubricants Synthetic lubricants alone can meet the most drastic and sever conditions such as those existing in aircraft engines, in which the same lubricants may have to be used in the temperature range of -500C and 2500C. Posses low freezing point, high viscosity-index. Thermally stable at high operating temp. Chemically stable in corrosive environments. Having high flash point and non-inflammable. Significant reduction in friction and wear. Optimum performance at extended temp. i.e. extreme cold & hot. Applications Polymerized hydrocarbons like poly alkylene oxides, poly glycidyl ethers – used at high temp. in roller bearing of sheet glass machinery. Di-2 ethyl sebacate (Diester) works at -500C to 2500C – used in turbo-jets. Silicons are not oxidized below 2000C above that forms gel and posses high viscosity index – used in clock timer and electronic devices. Flurinated tubes/ fluorocarbons are chemically & thermally stable – used un submarines. Poly alkylene glycols (PAGs) are thermally stable, anti-corrosive, stable at high rates of mechanical shear – used in aircrafts turbines. GAS LUBRICATION Lubrications for extreme conditions and for special application. Gas lubrication bearings are resistant towards high speed and extreme temp. Air, hydrogen, argon, helium, nitrogen, oxygen, CO2, and uranium hexa-fluoride are used in gas lubrication bearings. Gas lubricated bearings have various advantages over liquid and solid lubricants, it is virtually frictionless, silent and vibrationless. Used in spindles, motor-driver or turbine driver, circulations, fans, gyroscopes, compressors, turbo machinery etc. Due to low viscosity of gases, limited to a load of 15-30 Kpa. Caution is required to minimize the entry of dust particles, moisture and wear debris. Selection of Lubricants The selection of industrial lubricant requires the consideration of equipment used, available methods for handling, application of the lubricant itself and environmental conditions. In selecting a lubricant for a given application, it is essential to consider the various properties of the lubricant required in relation to the service conditions. It is better to use the lubricants recommended by the manufacturers of the equipment. Before using the lubricant, it is essential to know about the effect of load, temp. and speed at which the elements operate and also the contaminants which may affect the performance of the lubricants. Properties of Lubricating oils Viscosity- Viscosity is a measure of resistance of a fluid to deform under stress. It is commonly perceived as “thickness” or resistance to flow. It describes a fluid’s internal resistance to flow and may be thought of as a measure of fluid friction. Thus, water is “thin” having a lower viscosity, while vegetable oil is “thick” having a higher viscosity. Viscosity denotes opposition to flow. “Viscosity is defined as the force in dynes necessary for the movement of 1sq.cm layer of a fluid with a velocity of 1cm/sec. past another parallel layer 1cm away.” Types of viscosity There are two types of viscosity 1. Absolute viscosity – Absolute Viscosity is the force needed by a fluid to overcome its own internal molecular friction so that it can flow freely. In the field of fluid mechanics absolute viscosity is also known as dynamic viscosity. Defined as the tangential force per unit area which is required to maintain the unit velocity gradient b/w the two parallel layers and is denoted by η (Eta) /µ (mu). 2. Kinematic viscosity ν – Kinematic viscosity is a measure of a fluid's internal resistance to flow under gravitational forces. It is determined by measuring the time in seconds, required for a fixed volume of fluid to flow a known distance by gravity through a capillary within a calibrated viscometer at a closely controlled temperature. It directly influences the fuel atomization quality and size of the fuel droplet in the spray. It is denoted by ν (nu). Unit of viscosity Unit of viscosity (dynamic/absolute viscosity)η or µ :- 1. The IUPAC (International Union of Pure and Applied Chemistry) symbol for viscosity is the Greek symbol eta (η) and dynamic viscosity is referred with Greek symbol mu (µ). 2. The SI (International System of Units) physical unit of dynamic viscosity is pascal-second (Pa·s) which is identical to 1Kg·m−1·s−1. 3. The CGS (Centimeter–gram–second system) physical unit for dynamic viscosity is the poise as centipoise (cP). The centipoise is commonly used. 4. 1P = 1g·m−1·s−1 Unit of viscosity Unit of Kinematic viscosity ν :- 1. Denoted by Greek symbol nu (ν), SI unit is m2·s−1 2. CGS (Centimeter–gram–second) physical unit is strokes (St). 1 stokes = 100 centistokes = 1 cm2·s−1 = 0.0001 m2·s−1 1 centistokes = 1 mm²/s Dynamic vs Kinematic viscosity :- Conversion b/w dynamic and kinematic viscosity is given by νρ = η. ρ(rho) Effects of temp. & pressure on viscosity and Viscosity test Viscosity is inversely proportional to temperature, with increasing temperature viscosity decreases. It happens due to the decrease in intermolecular attraction b/w the lubricating oil. Viscosity is directly proportional to pressure, with increasing pressure viscosity increases. This is due to the increase in intermolecular attraction b/w the lubricating oil. Viscosity Test :- Four viscometers are used to measure the viscosity of the fluids 1. Redwood Viscometer 2. Engler’s Viscometer 3. Saybolt Viscometer 4. Kinematic Viscometer Redwood viscometer Presented by Sir Boventon Redwood in 1885. In this, 50ml of sample at a temp. of 38℃ is passed through a orifice of diameter 1.62 mm and 10mm length, time recorded in seconds. It is essential to maintain temperature, preventing spatter and gentle stirring. Description of apparatus The Redwood viscometer consist of a cylindrical brass oil cup (90 mm height & 46.5mm diameter) to hold the test sample. The bottom of the oil cup is fitted with a polished agate discharge tube, containing an orifice of the specified dimensions. the oil cup is surrounded by water bath for adjusting temperature. A calibrated receiving flask (Kohlrausch flask) is provided for receiving oil from polished agate discharge tube. When the sample reached test temperature, the time for 50 ml of the sample to flow through the orifice is measured. Results are reported in seconds stating the test temperature and viscometer types. For more viscous fluid and to prevent some minor deficiencies, Redwood No. 2 model was introduced Difference between Redwood viscometer 1 and 2 Redwood viscometer 1 Redwood viscometer 2 Dimension of Orifice is 10mm Dimension of Orifice is 50mm height and 1.62 mm diameter. height and 3.80 mm diameter. Useful for low viscous oil. Useful for high viscous oil. Receiving flask has smaller Receiving flask has larger mouth. mouth. Also called as Universal Also called as Admiralty Viscometer viscometer. Other viscometers 1. Engler’s Viscometer:- Used to compare the viscosity of oil with water. It is stated in Degree Engler (oE). 2. Kinematic Viscometer:- Used to determine kinematic viscosity. It is a U-type of glass apparatus having one and two bulbs at its two sides. 3. Saybolt Viscometer:- also used to determine kinematic viscosity. It contains digital thermometer therefore reading are more accurate. Viscosity can be directly compared for two or more liquids. Viscosity Index (VI) VI is a petroleum industry term, it is a lubricating oil quality indicator. It is an arbitrary, unitless scale to measure the rate of change of viscosity with respect to temperature. The viscosity of liquids decreases as temperature increases. The viscosity of a lubricant is closely related to its ability to reduce friction. The temperature chosen arbitrarily for reference are 100oF (38℃) and 210oF (100℃). The original scale stretches b/w VI=0 (worst oil) and VI=100 (best oil), but better oil have been produced leading to VI greater than 100. Now a days improvers and high quality base oils are used to increase the VI beyond 100. The VI of synthetic fluids ranges from 80 to over 400. Determination of Viscosity Index Viscosity index was derived by Mr. E.W. Bean and Mr. G.H.B. Davis of U.S.A in 1929. For this purpose they used two types of standard oil 1. Paraffinic base Pennsylvanian oil (VI =100) viscosity changing very slowly with temp. 2. Naphthenic base Gulf oil (VI = 0) viscosity changing rapidly with temp. Viscosity Index can be measured as Where L = viscosity in centistokes at 100oF (38℃) of an oil having zero VI and having the same viscosity at 210oF (100℃), as the test oil will have at 210oF (Gulf oil). H = Viscosity in centistokes at 100oF (38℃) of an oil having 100 VI and having the same viscosity at 210oF (Pennsylvanian oil). U = Viscosity in centistokes at 100oF (38℃) of a test oil as that of the sample oil. The higher is the viscosity index, better is the viscosity temperature characteristics. Numerical Q - An oil sample under test has Saybolt universal viscosity same as that of standard Gulf oil (low viscosity std.) and Pennsylvanian oil (high viscosity std.) at 210oF. The saybolt universal viscosity at 100oF is 550s, 750s, 450s respectively. Calculate the V.I. of the oil sample. Ans- Here L = 750, H = 450, U = 550 V. I. = 750 - 550 x 100 750 - 450 V. I. = 66.66 Flash Point and Fire Point Flash Point - The flash point of a flammable liquid is the minimum temperature at which the lubricant vaporizes, and when a tiny flame is brought near it, it will ignite for a moment. Flash point is often used as a descriptive characteristic of liquid fuel, but also used to describe liquids that are intentionally not used as fuel. Fire Point – Fire point is the minimum temperature at which the lubricant's vapors burns constantly for more than 5 sec after being ignited. None of these parameters are related to the temperature of the ignition source or of the burning liquid (which is much higher). Significance Flash point and fire point, both are important parameters for petroleum products for safety reasons. Low flash point oils are more volatile oils and if used in applications involving high temp. operations, higher rate of oil consumption may take place. Both should be higher than the maximum temperature of the country (for transportation). For domestic purpose, flash point above 50℃ is not desirable. A good lubricant should have flash point at least above the temperature at which it is to be used. If flash point under 30℃ (100oF) = Flammable liquids If flash point over 30℃ (100oF) = Combustible liquids. Measurement of flash point and fire point 1. Cleveland open cup apparatus- Used to determine the flash point and fire point of petroleum products (having the flash and fire point between 120℃ -250℃). The apparatus consist of a cylindrical brass cup a mark showing a level up to which the oil should be filled. The cup is supported by metal plate. An elaborate heating device is provided in such a way that the cup can be uniformly heated without any local super heating. A clamp is provided to hold the standard thermometer (0-400oC) supplied with the apparatus (2)Penskey Marten’s closed cup apparatus Used to determine flash point of lubricating oils, combustible oils, solvents, solvents containing materials and suspension of soilds, except cut-back asphalt. It contains brass cup and best used for oil having flash point b/w 50℃-370℃. Cup is provided with 4 openings for stirrer, thermometer, an air inlet and a device for introducing the standard flame and the cup is supported by its flange over a heating vessel. The shutter provided at the top of the cup has a lever mechanism. (3)Abel’s Closed Cup Apparatus Used to determine flash point of fuel oil, organic solvents, valuable compounds etc. Best used for oils having flash point b/w -30℃ to 70℃. Sample is placed in oil cup and heated at the rate of 2℃/min. The heating vessel is filled to overflowing with warm water. A small test flame is directed into the cup at regular interval and the lowest temp. at which application of test flame causes the vapour above the sample to ignite with distinct flame inside the cup, is recorded as Abel’s flash point. Cloud and Pour Points The temperature at which paraffin wax starts to crystallize to separate out from the oil when cooled under specified condition is known as cloud point. The temperature at which the lubricant becomes cloudy or hazy when cooled. The pour point of the oil is the lowest temperature at which the oil ceases to flow. Cloud and Pour point indicate the solubility of lubricants in cold conditions. Significance – useful in measuring the relative amount of wax in oil. Pour point values of petroleum and non-petroleum lubricants are significant, as many operations must function in sub freezing conditions. Generally pour point of the oils is lower than minimum ambient temp. at the place of application, so that the oil will readily flow at all time in the engine oil pumps or in the system. Apparatus for Cloud Point and Pour point In test jar, the oil is cooled at 25oF above cloud point. The cooling bath should maintain b/w 15oF and 30oF. At different time intervals, the test jar is taken from the bath without disturbance to the oil. A distinct cloudiness or haziness at the bottom of the jar appears, this temp. is recorded as the cloud point. For pour point, first of all the wax is dissolved at 115oF and cooled to 90oF before test. And then carried out in the same way as cloud point measurement. Bath should be held b/w 15 -30oF. At regular interval of 5oF, the test jar is taken out and tilted to make sure if the oil will flow or move. If it shows no movement when the jar is held horizontal for 5 sec, it is treated as solid point. Above 5oF, this solid point is known as pour point. Saponification Value Saponification Value or saponification number is referred to as “sap” in short. It represents the number of milligrams of KOH or NaOH required to saponify 1g of fat under the specified conditions. It is a measure of the average molecular weight (or chain) of all the fatty acids present. As most of the mass of a fat/tri-ester is in the 3 fatty acids, it allows for comparison of the average fatty acid chain length. Saponification is the alkaline hydrolysis of ester (generally of fats or oils) to give alcohol and soap’s (sodium or potassium salts of fatty acid). CH2- O- CO – C17 H35 CH2OH | | CH – O – CO–C17 H35 + 3KOH CHOH + 3C17H35COOK | | CH2 – O – CO–C17 H35 CH2OH Stearic acid Pot. Hydroxide Glycerol Potassium stearate Saponification value Significance – Animal and vegetable oils are used as additives in mineral oil and these oils posses their own characteristic sap value. Saponification number gives an indicator of the amount of animal and vegetable oils added to the mineral oils to improve its oiliness. Any deviation from this value gives the extent of adulteration. This test gives the information regarding the oil under study is animal/vegetable or mineral/compound oil. Numerical Q. 1.55 gm. of oil is saponified with 20 mL of N/2 KOH sol. after refluxing the mixture, it requires 15 mL of N/2 HCl sol. Find saponification value of oil. The volume of HCl used for blank reading was 20 ml. Ans. Wt. of oil = 1.55gm, Vol. of HCl for blank = 20 mL, Vol. of HCl for sample = 15 mL, Normality of HCl = N/2 = 0.5 N. Sap Value = (B-S) x Normality HCl x 56 Weight of KOH used = (20-15) x 0.5 x 56 1.55 = 90.32 mgs of KOH Neutralization Number Neutralization number determines the acidity or alkalinity of oil. It is no way indicates the corrosive attack of the used oil in service. It is also known as corrosion number. Acidity/acid value/acid number is the mass of KOH (milligrams) required to neutralize 1g of oil sample. Alkalinity/base value/base number is the mass of acid HCl (milligrams) required to neutralize 1g of oil sample. Acidity and alkalinity of lubricating oil are determined by neutralization number. It represent either Total Acid Number or Total Base Number. Significance of Neutralization Number It gives the value of relative change in oil due to oxidation. TAN and TBN when compared with new oil/fresh oil will indicate the formation of harmful products or the depletion of additives. Higher acid number indicates the oxidation of oil which leads to corrosion along with gummy compound and sludge formation. As the Neutralization point of oil increases, age of oil decreases. Iodine Value Iodine value/Iodine adsorption number/Iodine number is the mass of Iodine in grams that is consumed by 100 grams of a chemical substance. Iodine solution is yellow/brown in colour and any chemical group in the substance that reacts with iodine will make the colour disappear at a precise concentration. The amount of iodine solution required to keep the solution yellow/brown is a measure of the amount of Iodine sensitive reactive groups. When the oil is exposed to air and heat, it combines with oxygen and forms certain chemical compounds which are unsuitable for use as lubricants. Significance Iodine value gives the amount of unsaturated compound present in oil. It also shows the tendency of fatty oil to absorb oxygen. Acids and Gummy sludge are the products of oxidation. Each oil has its specific Iodine value. It determine the extent of contamination. Low Iodine value is desirable in oil, i.e. a good oil must have low Iodine value. Drying Oil like Linseed oil, Tung Oil have I.V. > 150. Semidrying Oil like Castor oil, soyabean oil have I.V. = b/w 100 – 150. Non drying Oil like coconut oil, Oilve oil have I.V. < 100. Aniline Point It is defined as the minimum equilibrium solution temperature for equal volume of aniline and lubricating oil sample. Or it is the minimum temperature here equal volume of aniline and lubricating oil get separated. Aniline point is used to characterize pure hydrocarbons and to indicate the aromatic content of hydrocarbon mixture. Equal volumes of aniline and oil sample or sample plus n-heptane are stirred together while being heated at a controlled rate. After the two phases become miscible, the mixture is cooled at a controlled rate and the temp. at which the two phases separate out is known as the Aniline point or mixed aniline point of the sample. Significance It gives the amount of aromatic comp. present in lubricating oil. Aromatic compounds have a tendency to dissolve natural rubber and certain types of synthetic rubber. Aromatic hydrocarbons exhibit the lowest aniline points and paraffinic hydrocarbons exhibit the highest values. Cycloparaffins and olefins exhibit values b/w paraffin and aromatics. In a homologous series, the aniline point increases with increasing molecular weight. Significance A product of high aniline point will be low in aromatics and naphthenes and therefore, high in paraffin. Aniline point is often specified for spray oils, cleaning solvents and thinners, where effectiveness depends upon aromatic content. The aniline point may be used to calculate the net heat of combustion for aviation fuels. Higher Aniline point means low percentage of hydrocarbons (desirable) Aniline point is used as an indication of possible deterioration of rubber sealing etc. Steam Emulsion Number SEN or demulsification number is defined as the time in seconds in which oil and water emulsion separate out into distinct layers. When water enters in an oil system, turbulence is caused by high volume flow resulting in the formation of emulsions. Some oil forms emulsion with water more easily than others. Due to the formation of emulsion, abrasion and wearing out of the lubricated parts of the machinery occur. Hence, it is essential that the lubricating oil should form such an emulsion with water which breaks off readily. The quicker the oil separates out from the emulsion, the lower is the steam emulsion number and better is the lubricating oil. Steam at 100oC is bubbled through a test tube containing 20 ml of oil sample till the volume becomes 40ml, temperature increases to 90C and the time is noted when the oil and water separate out in distinct layer. Significance To avoid corrosion of polished steel surfaces, it is important to check the speed of water and oil separation A good lubricating oil should have lower demulsification number. In cutting oils the higher the SEN, better the oil is. This is because the emulsion acts as a coolant as well as lubricant. Thank you

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