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
vapours 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
i) Pensky-Martens apparatus
ii) Thermometer- Low Range : -7 to 110oC, Graduation 0.5oC
High Range : 90 to 370oC, Graduation 2oC
SAMPLE
The sample should be just sufficient to fill the cup upto the mark
given on it.
PROCEDURE
A) FLASH POINT
i) Soften the bitumen between 75 and 100oC. Stir it thoroughly
to remove air bubbles and water.
ii) Fill the cup with the material to be tested upto the filling
mark. Place it on the bath. Fix the open clip. Insert the
thermometer of high or low range as per requirement and
also the stirrer, to stir it.
iii) 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.
iv) 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.
v) Flash point should be taken as the temperature read on the
thermometer at the time the flash occurs.
B) FIRE POINT
i) After flash point, heating should be continued at such a rate
that the increase in temperature recorded by the
thermometer is neither less than 5oC nor more than 6oC per
minute.
ii) The test flame should be lighted and adjusted so that it is of
the size of a bead 4mm in dia.
REPORTING OF RESULTS
i) 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.
ii) 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