ASTM D6450 method for flash point by continuously closed cup (CCCFP) tester
4. Summary of Test Method
4.1 The lid of the test chamber is regulated to a temperature at least 18°C below the expected flash point. A 1 +/- 0.1 mL test specimen of a sample is introduced into the sample cup, ensuring that both specimen and cup are at a temperature at least 18°C below the expected flash point, cooling if necessary. The cup is then raised and pressed onto the lid of specified dimensions to form the continuously closed but unsealed test chamber with an overall volume of 4.0 +/- 0.2 mL.
4.2 After closing the test chamber, the temperatures of the test specimen and the regulated lid are allowed to equilibrate to within 1°C. Then the lid is heated at a prescribed, constant rate. For the flash tests, an arc of defined energy is discharged inside the test chamber at regular intervals. After each ignition, 1.5 +/- 0.5 mL of air is introduced into the test chamber to provide the necessary oxygen for the next flash test. The pressure inside the continuously closed but unsealed test chamber remains at ambient barometric pressure, except for the short time during the air introduction and except at a flash point.
4.3 After each arc, the instantaneous pressure increase above the ambient barometric pressure inside the test chamber is monitored. When the pressure increase exceeds a defined threshold, the temperature at that point is recorded as the uncorrected flash point.
5. Significance and Use
5.1 The flash point temperature is one measure of the tendency of the test specimen to form a flammable mixture with air under controlled laboratory conditions. It is only one of a number of properties that must be considered in assessing the overall flammability hazard of a material.
5.2 Flash point is used in shipping and safety regulations to define flammable and combustible materials and classify them. This definition may vary from regulation to regulation. Consult the particular regulation involved for precise definitions of these classifications.
5.3 This test method can be used to measure and describe the properties of materials in response to heat and an ignition source under controlled laboratory conditions and shall not be used to describe or appraise the fire hazard or fire risk of materials under actual fire conditions. However, results of this test method may be used as elements of a fire risk assessment, which takes into account all of the factors that are pertinent to an assessment of the fire hazard of a particular end use.
5.4 Flash point can also indicate the possible presence of highly volatile and flammable materials in a relatively nonvolatile or nonflammable material, such as the contamination of lubricating oils by small amounts of diesel fuel or gasoline.
