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Description:
Scope: - This method of test is designed for the determination of the closed flash points of cutback bitumen’s of which the flash points do not exceed 230’ F ( 110’ C). Use is made of a modified form of the Abel apparatus.
- The results obtained by this method do not differ appreciably from the minimum flash point of the material under equilibrium conditions of temperature and vapour pressure.
Outline of Method: The sample is place in the cup of an Abel flash point apparatus and heated at a very slow uniform rate with stirring. 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.
Apparatus:
- Flash Point Apparatus- The apparatus to be employed shall be an able flash point apparatus with stirrer, as described in IP 33, Appendix I, but provided with means for mechanical stirring.
- Provision shall also be made for maintaining a good circulation in the water-bath, e.g. by means of a gentle stream of air being introduced through a fine tube entering the bath through a hole bored for the purpose.
- Thermometers – Conforming to the specification IP 43, F or C, and IP 44, F or C.
Sample:
In view of the case with which volatile matter can be lost from some cutback bitumen’s, all possible precautions should be taken against excessive handling of the sample in order to minimize its exposure to the atmosphere. In all cases, samples for the flash point test must be submitted in closed containers and it is strongly recommended, particularly in cases of dispute, that a separate sample (at least 4 oz (100g) should be made available for this test.
Procedure:
- If the sample is too viscous for ease of pouring at laboratory temperature, warm it gently in its closed container in a water-bath taking care not to raise the temperature of the sample higher than 20’ F (11’C) below its flash point.
Calculation and Reporting: - Correct the observed flash point to standard atmospheric pressure using the following rule:
- For each inch (25 mm) below 29.92 inches (760 mm) barometric reading, add 1.6’ F (0.9’C) to the flash point.
- For each inch (25 mm) above 29.92 inches (760 mm) barometric reading, sub tract 1.6’ F (0.9’C) from the flash point.
- Report the corrected flash point to the nearest 1’F (0.5’C) as flash point (Closed) of cutback Bitumen, IP 113.