IMPORTANT
TESTS ON AVIATION FUELS
8.1 DISTILLATION TEST
ASTM D-86
SCOPE:
This test is used to check the purity of the fuel. Distillation test is normally carried out for all petroleum products (Liquid fuels).
APPARATUS:
Round bottom flask, stand, burner, graduated receiving cylinder, thermometer, ice box, ice and condenser.
PROCEDURE:
A quantity of the fuel is heated in a glass flask carrying a thermometer and fitted to a condenser and a receiving cylinder. The most volatile compound boils first, turns to vapour, passed up the neck of the flask, over the thermometer bulb, into the condenser where it condenses back to a liquid and flows in the graduated receiver. As the temperature in the flask is increased, the less volatile compounds in their turn distilled, condense and pass into the receiver, until eventually either all the liquid in the flask has been boiled up or only a small quantity remains and can not be distilled over without decomposition.
The temperature at which the first drop of liquid falls into the receiver is recorded as initial boiling point (IBP), and the highest temperature at the end of the distillation as the final boiling point (FBP). The temperatures at which each 10% volume is recovered in the flask are also recorded as well as percentage volume collected at various selected temperatures.
OBSERVATIONS & CALCULATION:
Sample: Jet fuel JP-4 (100ml)
Recovery TempoC
IBP = 65oC
10% =94
20% =110
50% =146
90% =211
FBP =236oC
Total Recovery =98%
Residue =1.0%V
Loss =1.0%V
8.2 FREEZING POINT OF AVIATION FUEL
ASTM D2386-72
SCOPE:
Freezing point is that temperature at which crystals of hydrocarbons formed on cooling disappear when the temperature of the fuel is allowed to rise.
This method covers a procedure for the detection of separated solids in aviation reciprocating engine and turbine engine fuels at any temperature likely to be encountered during flight or on the ground.
APPARATUS:
Jacketed sample tube, gland, collars, stirrer, vacuum flask and thermometer.
PROCEDURE:
Take 25ml fuel in a dry jacketed sample tube. Close the tube tightly with the cork holding the stirrer and thermometer and adjust the thermometer position so that its bulb is in the centre of the fuel sample. Run one drop of alcohol down the stirring rod to wet the packing gland and tighten and gland as much as possible consist with permitting smooth movement of the stirrer without using undue force.
Clamp the jacketed sample to be so that it extends as far as possible into the vacuum flask containing the cooling medium. Add solid carbon dioxide as necessary through out the test to maintain the coolant level in the vacuum flask will above the level of the test sample.
Stire the fuel vigorously and continuously, except when making observation, taking care that the stirrer loops remain below the fuel surface at all times. Record the temperature at which crystals of hydrocarbon appear. Remove the jacketed sample tube from the coolant and allow the sample to warm up slowly, stirring it continuously. Record the temperature at which the hydrocarbon crystals completely disappear. The difference between the two temperatures should be less than 3oc.
RESULT
For Aviation Gasoline : Freezing point = -58OC
For Jet Fuel (JP-1) : Freezing point = -47OC
For Jet Fuel (JP-4) : Freezing point = -58OC
8.3 FLASH POINT TEST
IP-170
SCOPE:
This method determines the closed cup flash points of aviation fuel, whether they give off inflammable vapour below 73oF.
Flash point is the lowest temperature at which a combustible material will give off enough vapour to form an inflammable mixture with air.
APPARATUS:
Abel flash point apparatus, thermometer, metronome
PROCEDURE:
A measure quantity of the product is placed in a cup fitted with a lid carrying a thermometer. The fuel is heated slowly at a uniform rate and a small test flame is directed into the cup at regular intervals. The closed flash point is recorded as the lowest temperature at which a distinct flash occurs inside the cup on applying the flame.
RESULT:
1. Sample : JP-1 Flash point observed: 39oC
8.4 ESTIMATION OF CALORIFIC VALUES
ASTM D - 3338
SCOPE:
This test method is used to estimate the net heat of aviation gasoline and jet engine fuels. The test method is purely emperical and applicable to liquid hydro carbon fuels that conform to the specification for aviation gasoline and jet engine fuels of grades Jet A, Jet A-1, Jet B, JP-4, Jp-5, JP-7 and JP-8.
Calorific value may be defined as the heat liberated when a unit quantity of a fuel is burnt completely under standard conditions, and is a measure of the energy that can be obtained from its use.
APPARATUS:
Calorimeter Bomb, calorimeter vessel, stirrer, water jacket, fuel cup, ignition system, thermometers, thermometer reading eye piece (magnifying type) and oxygen charging equipment.
PROCEDURE:
Take 1gm of sample in a cup, and put it in the bomb. A platinum wire of about 6cm connecting the terminals in such away that it simply touches the sample, not the wall and bottom of the cup by forming U-shape, the bomb is then air tighten and oxygen / air is supply to increase the pressure and to make the combustion easy.
The bomb is then placed carefully in the calorimeter, containing distilled water having thermometer dipped in it. The temperature of the calorimeter should be above 0oc (at present 0oc). Ignite the sample and note the reading from the thermometer until the highest temperature, after which temperature starts following.
OBSERVATION AND CALCULATION:
Weight of sample = M = 0.99 gm (JP-1)
Initial temperature = Ti = 1.03oC
Final temperature = Tf = 5.31oC
Water equivalent of calorimeter = 2450
Correction factor = 0.003
Formulae:
Q = 2450 () - 60
8.5 DETERMINATION OF PEROXIDE NUMBER
ASTM D - 3703
SCOPE:
This test covers the determination of the peroxide content of jet fuels.
The magnitude of the peroxide number is an indication of the quantity of oxidizing constituents. Determination of jet fuel results in the formation of per oxides and other oxygen carrying compounds. Determination of the peroxide number of jet fuel is significant because of the adverse effect of peroxides upon certain elastomers in the fuel systems.
APPARATUS:
Iodine number flask (250ml), glass topper, burette, stand, beaker, and cylindrical jar
REAGENTS:
Distilled water, Acetic acid solution, potassium iodide, starch solution, sodium thiosulphate solution and nitrogen gas.
PROCEDURE:
Take 5l gm sample of the fuel (JP-4), and pass nitrogen gas upto 1 minute then add 20ml acetic acid and 2 ml potassium iodide solution. Shake it well and once again pass the nitrogen gas for five minutes, during this, cover the mouth of the flask to control evaporation of the sample.
After passing nitrogen gas add 100ml of distilled water and 5ml of starch solution and start titration. Sodium thiosulphate acts as a titrating agent. On titration, initially a bringal (violet) colour appears, the titration is continued till the colour disappears and then stopped titration and note the burette reading.
OBSERVATION AND CALCULATION:
Sample = JP-4
Sample weight = S = 51gm.
Distilled water = 100ml.
Burette reading = 4.5 ml
Normality of Na2S2O3 Solution = N = 0.005 N
Burette Initial reading 12ml
Burette Final reading 16.5ml
Volume of Na2S2O3 Solution Consumed = 4.5ml
Formula
Peroxide no. (mg/kg) = [ ]
Peroxide no. =
Peroxide no. = 3.53 mg/kg
CONCLUSION:
The peroxide no. of the sample must be up to 10mg/kg. Since our result is 3.53 mg/kg, so it is ok.
8.6 DOCTOR’S TEST
ASTM - D-1174-83
SCOPE:
This method is intended primarily for the detection of mercaptans in motor fuel, kerosene and similar petroleum products. It is applicable in the presence of more than slight traces of peroxide. The presence of mercaptans or hydrogen sulphide are both is indicated by discolouration of the sulphur floating at the oil-water interface.
APPARATUS:
Graduated cylinder of 50ml capacity and ground glass stopper.
MATERIALS:
Sodium plumbite solution, sulphur, cadmium chloride solution, hydrochloric acid, sodium hydroxide, lead acetate, potassium iodide solution and starch solution.
PROCEDURE:
Take 10ml of the sample and 5ml of sodium plumbite solution into a cylinder and shake them for 15 seconds. If a black precipitate forms immediately, record the presence of hydrogen sulphide, if the solution becomes opalescent and then darkens in color during the shaking period, record the presence of both mercaptan and elementary sulphur. If a brown precipitate is slowly formed, record the presence of peroxide and conform this by shaking a fresh quantity of the sample with 20% of its volume of acidified potassium iodide solution to which a few drops of starch solution have been added. A blue colour in the aqueous layer confirms the presence of peroxide.
Remove hydrogen sulphide from the sample by shaking a fresh quantity of it vigorously with 5% of its volume of the cadmium chloride solution. Separate the treated sample and recommence the test.
To the mixture obtained add a small quantity of sulphur, not more than will just cover the interface between the sample and the sodium plumbite solution, shake the mixture vigorously for 15 sec. & allow it to settle for one minute. If a yellow colour observed after the initial shaking is followed by the formation of a brown or black precipitate on the addition of sulphur record the presence of mercaptan and the absence of H2S and elementary sulphur.
Sample = JP-1
Result :
Report of the test is as follows:
Discoloration of sulphur Result
None Negative
Slight slight positive
Definite Positive
CONCLUSION:
No sulphur is present in the sample JP-1.
8.7 SMOKE POINT TEST
ASTM D-1322
SCOPE:
This method describes a procedure for evaluating jet fuel in respect of its ability to burn with out producing smoke.
The smoke point is defined as the maximum flame height in millimeters at which the fuel will burn without smoking.
APPARATUS:
Smoke point lamp, wick and graduated millimeter scale.
PROCEDURE:
Introduce 20ml of the filtered sample into a clean dry oil container. Extract a piece of wick not less than 125mm in length, with a suitable volatile solvent and dry it for 30 minutes at 100 to 110oC. Soak the wick in the sample under test and place in the wick holder, carefully easing out any twist arising from this operation. It is advisable to resoak the burning end of the wick in the sample. Place the wick holder in the container, screw home and ensure that the air inlet is free from oil. Cut the wick horizontally and trim free of frayed ends, so that 6mm of wick projects from the container. Maintain the oil container at a temperature of 20-25oC for 10 minutes. Insert into the lamp and light the wick. Adjust the wick to give a flame of about 10mm in height and allow to burn for 5 minutes.
Make 5 or 6 determinations of the smoke point by raising the wick until a smoky flame is produced and then lowering it until the smoky tail just disappears. Read in milimeters from the scale the height of the flame at this point, keeping the eye 230mm from the front of the lamp and slightly to one side, so that a reflected image of the flame in seen on the scale on one side of the central vertical white line, the flame it self being seen against the other side of the scale. Record the two readings when they are the same to ensure avoidance of vertical parallax. Remove the oil container from the lamp, clean out with solvent and dry for 30 minutes at 100 – 110oC. Blow out with air, read for a subsequent test.
RESULT:
The mean of the smoke points we calculated for the jet fuels are:
1) For JP-1 = 21mm.
2) For JP-4 = 25mm.
× Ř
|Chemical|
Faisalmurad|Guest book|
Comments|WEBMASTER|D.C.E.T|N.E.D uet|Title|
Certificates|MAIL Us|