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FUELS AND LUBRICANTS LAB MANUAL
DEPARTMENT OF MECHANICAL ENGINEERING
JNTUH COLLEGE OF ENGINEERING JAGTIAL
JNTUH Syllabus ME306ES: FUELS AND LUBRICANTS LAB B.Tech. II Year I Sem.
L 0
T/P/D C 0/3/0 2
Prerequisite: Chemistry Course Objectives: To Understand the fuel and lubricants properties. List of Experiments: 1. Determination of Flash and Fire points of Liquid fuels/Lubricants using: Abels Apparatus 2. Determination of Flash and Fire points of Liquid fuels/Lubricants using: Pensky Martens Apparatus 3. Carbon residue test: Liquid fuels. 4. Determination of Viscosity of Liquid lubricants and Fuels using: Saybolt Viscometer 5. Determination of Viscosity of Liquid lubricants and Fuels using: Redwood Viscometer 6. Determination of Viscosity of Liquid lubricants and Fuels using: Engler Viscometer 7. Determination of Calorific value: of Gaseous fuels using: Junkers Gas Calorimeter. 8. Determination of Calorific value: Solid/Liquid/ fuels using: Bomb Calorimeter. 9. Drop point and Penetration Apparatus for Grease. 10. ASTM Distillation Test Apparatus. 11. Cloud and Pour point Apparatus.
i
Contents JNTUH Syllabus
i
1
Abel’s Flash Point & Fire Point
1
2
Pensky Marten’s Flash and Fire Point
5
3
Saybolt Viscometer
7
4
Redwood Viscometer – I
11
5
Redwood Viscometer -II
15
6
Engler’s Viscometer
19
7
Grease Penetrant Test
23
8
Dropping Point of Lubricating Grease
25
9
Distillation Test
27
iii
1 Abel’s Flash Point & Fire Point 1 . 1 Aim To determine the flash point of the given fuel oil using Abel’s Flash Point & Fire point apparatus.
1.2 Apparatus Abel’s Flash Point Apparatus, Digital Temperature Indicator, given fuel oil to be tested.
1.3 Principle The sample is placed in the cup of the apparatus with the cup top closed and heated at a slow uniform rate. A small test flame is directed into the cup at regular intervals and the flash point is taken as the lowest temperature at which application of the test flame causes the vapour above the sample to ignite with a distinct flash inside the cup.
1.4 Theory Abel's flash-point apparatus is a petroleum-testing apparatus for determining the flash-point. It is used for the purpose of determining the flammable point of a number of petroleum products. Abel's Flash Point Apparatus with oil test jet is heated by Hot plate with Digital Temperature Indicator. This apparatus is suitable for determining the close cup flash point of petroleum and mixture. The fire hazards involved in the storage and handling of fuel oils are indicated by the flash point. Flash point: Flash point is the minimum temperature at which an oil gives off soon after removing the test flame. The flash point test can be summarized as a procedure in which a test specimen is introduced into a temperature-controlled test cup and an ignition source is applied to the vapours produced by the test specimen. The aim of the test is to determine whether the vapour/air mixture is flammable or at what temperature the vapour/air mixture is flammable. Fire point: Fire point is the minimum temperature at which oil starts burning. Fire point may be considered as the lowest temperature of the liquid at which vapour combustion and burning commences (at least for 5secs.). A fire point happens when an ignition source is applied and the heat produced is self-sustaining, as it supplies enough vapours to combine with air and burn even after the removal of the ignition source. The presence of contaminations can have a significant effect on the flash point, particularly if the contaminant is relatively more volatile. For example, pure ethylene glycol has a flash point of 111 °C. However, the flash point is reduced to 29 °C when acetaldehyde at a level of only 2% is present. Another common example would be ethanol; water addition has a significant effect on flammability. For solvents which are immiscible in water, the flash point will be largely unaffected by the addition of water.
1.5 Description A metal cup made of brass is provided with stirrer for maintaining uniform temperature of oil. There is provision to heat the oil cup in a water bath and also provision to measure the temperature of the oil by means of a thermometer.
1
1.6 Procedure 1. All parts of the cup and its accessories are cleaned and dried thoroughly before the test is started. 2. The cup is filled to the level of the pointer with the oil to be tested avoiding splashing. 3. The cover is carefully placed on the cup and pressed down in position and the initial temperature of the oil is noted. 4. Insert the round bulb thermometer in the socket provided so that the scale faces the operator. 5. The water bath thermometer is inserted through the water bath socket, the water bath being filled with water. 6. If oil is used for test flame, moisten the cotton wool in the lamp and the wick with paraffin oil, light the wick and adjust so that the flame is of the size of the head fixed on the cover of the cup. 7. If gas flame is used as test flame, connect with rubber tube to the gas supply through a cock and adjust the flame to the proper size. 8. The water bath is heated and operating the shutter mechanism plus the stirrer (1 rev/s). The flash point is found out by the temperature at which a blue halo is observed. 0
9. The application of flame should be at an interval of 1 C when the expected flash point is approaching.
1.7 Observations
Property tested
Temperature (0C)
Flash Point Fire point
2
1.8 Precautions 1. Cup and accessories are cleaned thoroughly. 2. After determining the fire point, the heating is stopped.
1.9 Results 0
1. The flash point is observed at ____ C 0
2. The fire point is observed at _____ C
3
2 Pensky Marten’s Flash and Fire Point 2.1 Aim To determine the flash and fire points of the given fuel oil using Pensky Marten’s flash and fire point tester.
2 . 2 Apparatus Pensky Marten’s flash and fire point tester, Digital Temperature Indicator and given oil to be tested.
2.3 Theory The fire hazards involved in the storage and handling of fuel oils are indicated by the flash and fire points. However, there is no correlation between flash and fire points of an oil and its ignition temperature. i. ii.
iii. iv.
Flash point: Flash point is minimum temperature at which oil gives off sufficient vapours to form inflammable mixture with air. Indications of flash point: Upon the application of test flame on oil surface a bluish flame with a feeble sound is seen in a confined space (i.e., at a point of application of test flame). This bluish flame goes off soon after removing the test flame. Fire point: Fire point is the minimum temperature at which oil produces a mixture of its vapours and air that will burn continuously once ignited, even after the removal of test flame. Indications of fire point: Upon the application of test flame on the oil surface a bluish flame appears on the entire oil surface. The same continues even after removing the test flame.
Pensky Marten’s flash and fire point testing apparatus is used for oils having flash points above 0
0
120 F/ 49 C. A brass test cup is filled with a test specimen and closed with a lid, through which an ignition source can be introduced periodically. The sample is heated and stirred at specified rates depending on the material that is being tested. This allows the development of equilibrium between the liquid and the air volume. The ignition source is directed into the cup at regular intervals with simultaneous interruption of stirring. The test concludes upon observation of a flash that spreads throughout the inside of the cup. The corresponding temperature is the liquid's flash point.
5
2.4 Description A metal cup made of brass is provided with stirrer for maintaining uniform temperature of oil and a shutter to close the cup. There is a provision to heat the oil cup by means of an electrical coil. There is a knob to set the temperature and provision to measure the temperature of the oil by means of a thermometer.
2.5 Procedure 1. All parts of the cup and its accessories are cleaned and dried thoroughly before the test is started. 2. The cup is fitted with given oil to be tested up to the level indicated by the filling mark. 3. The lid has to be placed on the cup and insert the thermometer of high or low range as required. 4. The electric supply is switched on and the sample is gradually heated. Thermometer of suitable range is introduced into the oil. 0
5. The oil is constantly stirred and test flame is applied at an interval of 1 C increases in temperature. 6. The temperature, at which a distinct flash (which soon subsides) is seen, is noted down. 7. The heating is continued until the oil vapours get ignited and burn on application of test flames, continuously even after removal of test flame. This temperature is called fire point. 8. Then the lid is completely taken out and flash and fire points in lid open condition are noted.
2.6 Observations Temperature 0 C
Property tested Flash point Fire point
2.7 Precautions 1. Care is taken to see that the cup and its accessories are clean and dry. 2. The supply is switched off after ascertaining the fire point.
2.8 Applications For determining the flash point of fuel oils and lubricating oil, bitumen other than cutback bitumen and suspension of solids in liquids, having a flash point above 49°C.
2.9 Results 0
1. The flash point is observed at ____ C 0
2. The fire point is observed at _____ C
6
3 Saybolt Viscometer 3.1
Aim To determine the viscosity of lubricating oil by using a Saybolt viscometer.
3.2 Apparatus Say bolt viscometers, Digital Temperature Indictor and stop watch
3.3 Theory Viscosity of lubricating oil is measured by an instrument known as viscometer. Most of the viscometers are of efflux type. In these, a measured volume of oil at a particular temperature is allowed to efflux through a capillary tube and the time of flow is noted in seconds. The testing procedure is quite similar to the capillary-tube viscometers where efflux time of a specified volume of fluid is measured through fixed orifice at the bottom of a cup to represent the viscosity of the fluid. It has a digital meter to measure temperature and so reading is more accurate and precise. The coils wrap around the container uniformly so uniform temperature can be obtained. Viscosity can be directly compared for two or more liquids. Say bolt viscometer is employed by the oil industry in U.S.A. The units of dynamic viscosity in M.K.S and S.I systems are centipoise and MPa-s respectively. Similarly, the units of kinematic viscosity ‘ν’ in M.K.S and S.I systems are 2
centistokes and m /s respectively. i.
ii.
Viscosity (µ): Viscosity is a measure of resistance to relative translational motion of adjacent layers of a fluid. It is the property of a fluid. The unit of viscosity is poise or centipoise (cp). Specific viscosity: Specific viscosity is the ratio of the viscosity of fluid to the viscosity 0
iii.
0
of water at 20 C. Since the water has a viscosity of 1cp at 20 C. Kinematic viscosity (ν): Kinematic viscosity is defined as the ratio of dynamic viscosity (µ) to the density (ρ) of the fluid.
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3.4 Description It consists of a universal container containing the liquid which is allowed to discharge through a standard orifice in a tip fitted at the centre of the case container. There are two tips, (i) Universal tip and (ii) Furol tip. Furol tip is for less viscous and universal tip for all liquids usually for highly viscous liquids. The bath stirring is fitted with a thermometer collar, knobs for holding and stirring and also provisions for electric heating by means of an electric heating coil and a ‘U’ tube to heat the bath by steam or to cool the bath if need be by water circulation and these are fitted in the bath stirred cover. Bath and stirrer are finished in highly polished chromium plating to facilitate cleaning and are mounted on a stand with levelling feet. A cork is provided at the bottom of the oil cup to cause or prevent flow of oil when it is not in position or when it is in position.
3.5 Procedure 1. Fill the required quantity of water in the water container. 2. Plug the bottom of the orifice by rubber cork and fill the tube with the oil sample. 0
3. Switch on the supply of the bath heater. As the oil temperature reaches 40 C and becomes steady, place the measuring flask and funnel in position to collect the oil. 4. Remove the rubber cork out and start noting the time till the oil level reaches 60 cc mark in the measuring flask. 5. Record the time in second. 6. Repeat the experiment at different temperatures of the oil and record the corresponding timings. 7. Calculate the viscosity of oil for each temperature setting.
3.6 Observations S. No
Temperature of oil (0C)
Time of collection for 60cc, ‘t’ (s)
ν (centistokes)
3.7 Calculations ν = At – B/t centistokes Dynamic viscosity, µ = ν x ρ Where, ρ = density of oil in kg/m
3
t = time in second
A and B are the constants of viscometer For 34 < t < 115, A = 0.224 & B = 185;
For 115 < t < 215, A = 0.223 & B = 115
3.8 Precautions 1. The position of the measuring flask should be such that the oil strike the flared mouth of the funnel and does not drop directly into the flask since this may trap air and cause foaming. 2. The temperature of the oil in the oil – tube should be maintained constant to avoid errors as the viscosity is the function of temperature.
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Limitation of Saybolt viscometer The instrument should be used only where laminar flow exists in the tube, and the time is above 40 seconds for flow of 60cc of oil.
3.9 Graphs 1. Absolute viscosity V/s Temperature 2. Kinematic viscosity V/s Temperature
3.10 Applications For the empirical measurement of Saybolt Viscosity of petroleum products. Efflux cup viscometers are most commonly used for fieldwork to measure the viscosity of oils, syrups, varnish, paints and Bitumen emulsions. 1. Industry: Civil Infrastructure Asphalt / Petroleum/ Bitumen Testing Dams & Tunnels Real Estate Roads, Highways & Bridges Traffic Monitoring 2. Education Building Technology Civil Department Geotechnical Science Colleges 3. Traffic & Transportation Roads, Highways & Bridges
3.11 Conclusion Viscometers are helpful in determining and establishing the degree of viscosity of a fluid at particular time and temperature.
3.12 Result The absolute viscosity of the determined oil is ____ at ____0C
9
4 Redwood Viscometer – I 4 . 1 Aim To determine the absolute and kinematic viscosities of given lubricating oil at various temperatures starting from room temperature.
4 . 2 Apparatus Redwood viscometer – I, Digital Temperature Indicator, stop-watch, measuring flask (50 cc, glass jar) and oil (SAE 20 / SAE 40).
4.3 Theory i. ii.
Viscosity (µ): Viscosity is a measure of resistance to relative translational motion of adjacent layers of a fluid. It is the property of a fluid. The unit of viscosity is poise or centipoise (cp). Specific viscosity: Specific viscosity is the ratio of the viscosity of fluid to the viscosity 0
iii.
0
of water at 20 C. Since the water has a viscosity of 1cp at 20 C. Kinematic viscosity (ν): Kinematic viscosity is defined as the ratio of dynamic viscosity (µ) to the density (ρ) of the fluid.
Effect of temperature on viscosity: Increase in temperature causes a decrease in the viscosity of a liquid, whereas viscosity of gases increases with temperature growth. The viscous forces in a fluid are the outcome of intermolecular cohesion and molecular momentum transfer. In liquids the molecules are comparatively more closely packed, molecular activity is rather small and so the viscosity is primarily due to molecular cohesion. Significance of viscosity measurements: Viscosity is the property of lubricating oil that determines it ability to lubricate and through its film strength, viscosity values are used i. ii. iii.
In evaluating load carrying capacity In denoting the effect of temperature changes and for determining the presence of contaminants in used oil during service Absolute viscosity values are required for use in all bearing design calculations and other lubrication engineering technical design problems.
4.4 Description The redwood viscometer consists of a heavily silver plated oil cup with a dished bottom placed in a bright chrome plated water bath. The water bath is mounted on a stand with levelling screws. The level to which the oil is to be filled into cup is given by and index fixed to the inside wall of the oil cup. A standard size jet of stainless steel is fitted at the centre of the bottom of the cup for the flow out of oil of liquid to be measured. The cylindrical water bath is provided with a tap for emptying.
The bath of liquid is stirred manually by means of a cylinder surrounding the oil cup provided with three vanes, having their upper and lower portions turned in opposite directions. The valve for starting and stopping the flow of the liquid from the oil cup consists of a ball carried on a stiff wire, both heavily silver plated. The oil cup cover is fitted with an insulated handle and has suitable slots for the slots for the oil-cup thermometer and valve rod. The
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circular spirit level is mounted on a plate to fit on the upper end of the oil cup. Diameter 1.62 mm orifice is used in No.1
4.5 Procedure 1. The oil cup is cleaned with a suitable solvent, for example, Carbon tetrachloride and then dry it thoroughly using tissue paper or some similar material which will not leave any fluff. Examine the jet and ensure that it is clean and not obstructed. 2. The viscometer is levelled by using the level feet. The viscometer bath is heated to a few degrees above the desired test temperature. 3. The prepared sample of the oil is poured into the oil cup through a filler of metal gauge not coarser than BS 100 mesh. Mesh size indicates the number of holes divided in one square inch area. 4. The temperature of bath is adjusted until the sample in the cup is maintained at the test temperature. Stirring the contents of the bath and cup during the process be assured, preferably using continuous stirring for both. 5. The sample is stirred during the preliminary period, for example, by means of ball valve, closing the bottom of the jet by suitable means, but not during the actual determination. 6. When the temperature of the sample has become quite steady at the desired value, the liquid level is adjusted by allowing the sample to flow out until the surface of the sample touches the filling point. 7. The oil cup cover is placed and the oil cup thermometer is swung towards the closed end of the curved slot in the cover. 8. The clear, dry, standard 50 cc flask is placed centrally below the jet with the top of the neck a few mm from the bottom of the jet. Redwood viscometer – I is suitable for measurement of viscosity less than 2000 seconds. 9. The flask is not insulated in any way. The ball valve is lifted and simultaneously the time recorder is started.
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10. The time recorder is stopped at the instant the sample reaches the graduation mark of the flask and the final reading of the oil cup thermometer is noted. 11. The procedure is repeated for various temperatures and the time in second is noted at each temperature and the results are tabulated.
4.6 Observations Oil sample: S. No.
Oil temperature ‘t’ 0C
Time taken to collect 50 ml of oil, ‘R’ second
Oil density ‘ρ’ kg/m3
4.7 Calculations Kinematic viscosity = AR – B/R
in centistokes
Where, A & B are viscometer constants A = 0.26
B = 171.5
R = time in second for collection of 50 cc of oil in the flask. Absolute viscosity = Kinematic viscosity x Density (centipoise)
4.8 Applications It is used for low viscous oils, for example, Kerosene oil. Viscosity helps in selecting good lubricating oil Light oils
Heavy Oils
Having low density
High density
Easy flow ability
Low flow ability
Used for; High speed, low pressure
Used for; Low speed, high
& Low temperature
pressure & high temperature
4.9 Graphs 1. Absolute viscosity Vs Temperature 2. Kinematic viscosity Vs Temperature
4.10 Precautions 1. The oil should be filtered thoroughly a muslin cloth to remove solid particles that may clog the jet. 2. The receiving flask should be placed in such a manner that the oil stream from jet strikes the neck of receiving flask and do not cause any foaming. 3. After each reading the oil should be completely drained out of receiving flask.
13
4.11 Conclusion Viscometers are helpful in determining and establishing the degree of viscosity of a particular fluid at particular time and temperature.
4.12 Result The viscosity of given oil sample using Redwood viscometer no.1 at
0C is____
14
5 Redwood Viscometer -II 5 . 1 Aim To determine the absolute and kinematic viscosity of a given lubricating oil at various temperatures starting from room temperature.
5.2
Apparatus
Redwood viscometer, Thermometers, Stop-watch, Measuring flask (50 cc), Glass jar and oil (SAE20 / SAE 40).
5.3 i. ii.
Theory Viscosity (µ): Viscosity is a measure of resistance to relative translational motion of adjacent layers of a fluid. It is the property of a fluid. The unit of viscosity is poise or centipoise (cp). Specific viscosity: Specific viscosity is the ratio of the viscosity of fluid to the viscosity 0
iii.
0
of water at 20 C. Since the water has a viscosity of 1cp at 20 C. Kinematic viscosity (ν): Kinematic viscosity is defined as the ratio of dynamic viscosity (µ) to the density (ρ) of the fluid.
Effect of temperature on viscosity: Increase in temperature causes a decrease in the viscosity of a liquid, whereas viscosity of gases increases with temperature growth. The viscous forces in a fluid are the outcome of intermolecular cohesion and molecular momentum transfer. In liquids the molecules are comparatively more closely packed, molecular activity is rather small and so the viscosity is primarily due to molecular cohesion. Significance of viscosity measurements: Viscosity is the property of lubricating oil that determines it ability to lubricate and through its film strength, viscosity values are used i. ii.
In evaluating load carrying capacity In denoting the effect of temperature changes and for determining the presence of contaminants in used oil during service.
iii.
Absolute viscosity values are required for use in all bearing design calculations and other lubrication engineering technical design problems.
5.4 Description The redwood viscometer consists of a heavily silver plated oil cup with a dished bottom placed in a bright chrome plated water bath. The water bath is mounted on a stand with levelling screws. The level to which the oil is to be filled into cup is given by and index fixed to the inside wall of the oil cup. A standard size jet of stainless steel is fitted at the centre of the bottom of the cup for the flow out of oil of liquid to be measured. The cylindrical water bath is provided with a tap for emptying. The bath of liquid is stirred manually by means of a cylinder surrounding the oil cup provided with three vanes, having their upper and lower portions turned in opposite directions. The valve for starting and stopping the flow of the liquid from the oil cup consists of a ball carried on a stiff wire, both heavily silver plated.
15
The oil cup cover is fitted with an insulated handle and has suitable slots for the slots for the oilcup thermometer and valve rod. The circular spirit level is mounted on a plate to fit on the upper end of the oil cup. The diameter 3.8 mm orifice is used in No.2.
5.5 Procedure 1. The oil cup is cleaned with a suitable solvent, for example, Carbon tetrachloride and then dries it thoroughly using tissue paper or some similar material which will not leave any fluff. Examine the jet and ensure that it is clean and not obstructed. 2. The viscometer is levelled by using the level feet. The viscometer bath is heated to a few degrees above the desired test temperature. 3. The prepared sample of the oil is poured into the oil cup through filler of metal gauge not coarser than BS 100 mesh. Mesh size indicates the number of holes divided in one square inch area. 4. The temperature of bath is adjusted until the sample in the cup is maintained at the test temperature. Stirring the contents of the bath and cup during the process be assured, preferably using continuous stirring for both. 5. The sample is stirred during the preliminary period, for example, by means of ball valve, closing the bottom of the jet by suitable means, but not during the actual determination. 6. When the temperature of the sample has become quite steady at the desired value, the liquid level is adjusted by allowing the sample to flow out until the surface of the sample touches the filling point. 7. The oil cup cover is placed and the oil cup thermometer is swung towards the closed end of the curved slot in the cover.
16
8. The clear, dry, standard 50 cc flask is placed centrally below the jet with the top of the neck a few mm from the bottom of the jet. Redwood viscometer is suitable for measurement of viscosity of oil which has less than 2000 seconds. 9. The flask is not insulated in any way. The ball valve is lifted and simultaneously the time recorder is started. 10. The time recorder is stopped at the instant the sample reaches the graduation mark of the flask and the final reading of the oil cup thermometer is noted. 11. The procedure is repeated for various temperatures and the time in second is noted at each temperature and the results are tabulated.
5.6 Observations Oil sample:
Oil temperature Sl. No. ‘t’ 0C
Time taken to collect 50 ml of oil, ‘R’ second
Oil density ‘ρ’ kg/m3
5.7 Calculations Kinematic viscosity = A x R – B/R in centistokes Where, A & B are viscometer constants A = 0.26
B = 171.5
R = time in second for collection of 50 cc of oil in the flask. Absolute viscosity = Kinematic viscosity x density = γ x ρ i n centipoises
5.8 Graphs 1. Absolute viscosity Vs Temperature. 2. Kinematic viscosity Vs Temperature
5.9 Precautions 1. The oil should be filtered thoroughly a muslin cloth to remove solid particles that may clog the jet. 2. The receiving flask should be placed in such a manner that the oil stream from jet strikes the neck of receiving flask and do not cause any foaming. 3. After each reading the oil should be completely drained out of receiving flask.
5.10 Applications The viscosity of a highly viscous fluid, for example, Fuel oil and mobile oil, is determined using Redwood Viscometer No.2
17
Viscosity helps in selecting good lubricating oil Light oils
Heavy Oils
Having low density
High density
Easy flow ability
Low flow ability
Used for; High speed, low pressure
Used for; Low speed, high
& Low temperature
pressure & high temperature
5.11 Conclusion Viscometers are helpful in determining and establishing the degree of viscosity of a particular fluid at particular time and temperature.
5.12 Result The viscosity of given oil sample using Redwood viscometer no.2 at
0
C is ____
18
6 Engler’s Viscometer 6.1
Aim To find viscosity of given oil specimen by using Engler’s viscometer.
6.2
Apparatus Engler’s viscometer, Digital Temperature Indicator, stop watch and conical flask.
6.3 Theory The viscosity of given oil is determined as the time of flow in Engler’s seconds. The viscosity of a fluid indicates the resistance offered to shear under laminar condition. Dynamic viscosity of a fluid is the tangential force on unit area of either of two parallel planes at unit distance apart when the space between the plates is filled with the fluid and one of the plate’s moves relative to the other with unit velocity in its own plane. The unit of dynamic viscosity is dyne-sec/cm2. Kinematic viscosity of a fluid is equal to the ratio of the dynamic viscosity and density of the fluid. The unit of kinematic viscosity is cm2/s. i.
Viscosity (µ): Viscosity is a measure of resistance to relative translational motion of adjacent layers of a fluid. It is the property of a fluid. The unit of viscosity is poise or centipoise (cp).
ii.
Specific viscosity: Specific viscosity is the ratio of the viscosity of fluid to the viscosity of water at 200 C. Since the water has a viscosity of 1cp at 200 C.
iii.
Kinematic viscosity (ν): Kinematic viscosity is defined as the ratio of dynamic viscosity (µ) to the density (ρ) of the fluid.
Effect of temperature on viscosity: Increase in temperature causes a decrease in the viscosity of a liquid, whereas viscosity of gases increases with temperature growth. The viscous forces in a fluid are the outcome of intermolecular cohesion and molecular momentum transfer. In liquids the molecules are comparatively more closely packed, molecular activity is rather small and so the viscosity is primarily due to molecular cohesion. Engler specific viscosity: Engler specific viscosity is the ratio of time of flow for 50 ml of material in seconds using an Engler viscometer at a selected temperature to the time of flow, in second, for an equal volume of water at 20°C.The usual temperatures for determination of specific viscosity for tar materials are 25°C, 40°C, 50°C, and 100°C, and generally the temperature is so selected that the specific viscosity is not more than 45. Engler’s viscometer which is efflux tube was developed in Germany. The method is basically empirical but it is possible to relate efflux time to absolute viscosity using charts/tables developed by Asphalt institute for this purpose.
6.4 Description The apparatus consists of an oil cup placed centrally in a bath containing water. Inside there are three balancing screws to the level the oil cup the oil is to be poured up to the level marked. There is a standard orifice at the base of oil cup. A bakelite valve stick is provided to close or open the orifice.
19
Surrounding the oil cup is a water bath which can be heated by means of electric heater. The whole apparatus is mounted on a tripod stand which can be levelled by adjusting the levelling screws.
6.5 Procedure Clean the oil cup dry it .Pour water on water bath .Filter the oil and pour in to oil up to the marked level. Carefully and in controlled manner heat the water in water bath. Stir it continuously until the desired temperature is reached. Stop stirring and place the clean flask below the orifice. Lift the valve stick and simultaneously start a stop watch. Note the time taken for collection of 200ml of oil. Repeat the same for other temperatures. Calculate kinematic and absolute viscosity and tabulate the results.
6.6 Observations S. No
Temperature of oil
Time taken to flow of 200ml oil
Density in kg/m3
6.7 Calculations Absolute viscosity of oil = kinematic viscosity x density Kinematic viscosity = At – B/t Where, t = time taken for 200 ml oil flow through orifice at particular temperature A and B are instrument constants A = 0.00264; B = 1.9
for t < 85 sec;
A = 0.00247; B = 0.65
for t