Aim
To determine the flash point and the fire point of asphaltic bitumen and fluxed native asphalt, cutback bitumen, and blown type bitumen as per IS: 1209 – 1978.
Principle
Flash Point:- The flash point of a material is the lowest temperature at which the application of test flame causes the vapors from the material to momentarily catch fire in the form of a flash under specified conditions of the test.
Fire Point:- The fire point is the lowest temperature at which the application of test flame causes the material to ignite and burn at least for 5 seconds under specified conditions of the test.
Apparatus
- Pensky-Martens apparatus
- Thermometer- Low Range : -7 to 110 oC, Graduation 0.5 oC
High Range :- 90 to 370 oC, Graduation 2 oC
Sample
The sample should be just sufficient to fill the cup up to the mark given on it.
Procedure
A. Flash point
1. Soften the bitumen between 75 and 100oC. Stir it thoroughly to remove air bubbles and water.
2. Fill the cup with the material to be tested up to the filling mark. Place it in the bath. Fix the open clip. Insert the thermometer of high or low range as per requirement and
also, the stirrer, to stir it.
3. Light the test flame, adjust it. Supply heat at such a rate that the temperature increase, recorded by the thermometer is neither less than 5oC nor more than 6oC per minute.
4. Open flash point is taken as that temperature when a flash first appears at any point on the surface of the material in the cup. Take care that the bluish halo that sometimes
surrounds the test flame is not confused with the true flash. Discontinue the stirring during the application of the test flame.
5. Flash point should be taken as the temperature read on the thermometer at the time the flash occurs.
B. Fire point
1. After the flash point, heating should be continued at such a rate that the increase in the temperature recorded by the thermometer is neither less than 5 oC nor more than 6 oC per minute.
2. The test flame should be lighted and adjusted so that it is of the size of a bead 4 mm in dia.
Results
1. The flash point should be taken as the temperature read on the thermometer at the time of the flame application that causes a distinct flash in the interior of the cup.
2. The fire point should be taken as the temperature read on the thermometer at which the application of test flame causes the material to ignite and burn for at least 5 seconds.
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