ASTM D6450 method for flash point by continuously closed cup (CCCFP) tester
11. Procedure
11.1 Thoroughly clean and dry the lid together with the arc pins and the sample cup before starting the test. Be sure to remove any solvent used to clean the apparatus. If the expected flash point of a sample is more than 15°C higher than the flash point of the previous sample, heat the lid together with an empty, dry sample cup to a temperature 30°C higher than the expected flash point of the new sample.
NOTE 5 - The dry cup heating procedure will eliminate possible cross contamination from residual vapors.
11.2 Expected Flash Point - Set the initial temperature to at least 18°C below the expected flash point. Set the final temperature to a value beyond the expected flash point.
11.2.1 No Expected Flash Point Available - When testing materials for which no expected flash point temperature is known, set the initial temperature to 10°C and measure the material to be tested in the manner described. This flash point result shall be considered as approximate. The derived value can be used as the expected flash point when a fresh specimen is tested in the standard mode of operation.
11.3 Set the heating rate to 5.5 +/- 0.5°C/min.
11.4 Set the ignition frequency to 1°C.
11.5 Set the air introduction to 1.5 mL.
11.6 Set the pressure threshold for the flash detection to 20 kPa.
11.7 Initiate the test procedure to regulate the lid to the initial temperature. When the initial temperature is reached as indicated by the instrument, prepare to introduce the 1 +/- 0.1 mL specimen of the sample.
11.8 Ensure that the sealed sample and the sample cup are at least 18°C below the expected flash point temperature, cool if necessary. Shake the sample thoroughly before opening the sample container. Extract 1 mL of sample with a pipette or syringe, and close the container. Transfer 1 +/- 0.1 mL of the sample to be tested into the sample cup.
11.9 Insert a stirring magnet into the sample cup to ensure a consistent sample mix.
11.10 Put the sample cup onto the sample cup support of the tester, and start the procedure. Raise and press the sample cup onto the lid, which is at the initial temperature and thus at a higher temperature than the sample cup. While the temperature of the sample cup and the lid are equalizing, apply a precautionary arc at 10°C intervals (see 6.1.7). If a flash is detected at one of these precautionary arcs, discontinue the test, and discard the result. Repeat the test with a fresh specimen and with a lower initial temperature of at least 18°C below the temperature at which the flash was detected.
11.11 After the temperature between the temperature regulated lid and the specimen have equalized to within 1°C, start the actual test for the flash point. Heat the lid with the programmed heating rate, and apply the arc ignition in equidistant temperature steps of 1°C. Monitor the instantaneous pressure increase within 100 ms after the arc. Stop the test when a flash is detected or when the final temperature is reached in the case of no flash point. The flash point temperature is the specimen temperature at which the instantaneous pressure increase, due to the presence of the flash, exceeds 20 kPa.
11.12 When a flash is detected at a temperature that is higher than 26°C above the initial temperature, or when a flash is detected at a temperature that is less than 10°C above the initial temperature, consider the result approximate and repeat the test with a fresh test specimen. Adjust the expected flash point for this next test to the temperature of the approximate result. The initial temperature for this fresh test specimen shall be 18°C below the temperature of the previous approximate result.
11.13 Record the specimen temperature reading at the detected flash point as the uncorrected flash point temperature. If no flash point was detected within the tested temperature range, record flash point is higher than the final temperature.
11.14 At the conclusion of the test, cool the sample cup below 50°C to withdraw it safely.
12. Calculation
12.1 Barometric Pressure Correction - Observe and record the ambient barometric pressure at the time of the test. When the pressure differs from 101.3 kPa, correct the flash point as follows:
Corrected flash point = C + 0.25 (101.3 - p)
where:
C = observed flash point in °C, and
p = ambient barometric pressure in kPa.
Round the corrected value to the nearest 0.5°C. (Warning - The barometric pressure used in this calculation must be the absolute ambient pressure for the laboratory at the time of the test. Many aneroid barometers, such as those used at weather stations and airports, are corrected to give sea level readings: These shall not be used.)
