ASTM D56 standard test method for flash point by Tag closed cup tester
6. Apparatus (Manual Instrument)
6.1 Tag Closed Tester - The apparatus is shown in Fig. 1 and described in detail in Annex A1.
6.2 Shield - A shield 460 mm (18 in.) square and 610 mm (24 in.) high, open in front, is recommended.
6.3 Temperature Measuring Device - A liquid-in-glass thermometer, as prescribed in Table 1, or an electronic temperature measuring device such as a resistance device or thermocouple. The device shall exhibit the same temperature response as the liquid-in-glass thermometer.
NOTE 2 - Whenever thermometers complying with ASTM requirements are not available, thermometers complying with the requirements for The Institute of Petroleum thermometer IP 15C PM-Low can be used.
7. Sampling
7.1 Erroneously high flash points will be obtained when precautions are not taken to avoid the loss of volatile material. Containers should not be opened unnecessarily to prevent loss of volatile material and possible introduction of moisture. Transfers should not be made unless the sample temperature is at least 10°C (18°F) below the expected flash point. When possible, flash point shall be the first test performed on a sample and the sample must be stored at low temperature.
7.2 Do not store samples in gas-permeable containers since volatile materials may diffuse through the walls of the enclosure. Samples in leaky containers are suspect and not a source of valid results.
7.3 At least 50 mL of sample is required for each test. Refer to sampling information in Practice D4057.
8. Preparation of Apparatus (Manual)
8.1 Support the manual apparatus on a level steady surface, such as a table. Unless tests are made in a draft-free room or compartment, surround the tester on three sides by the shield for protection from drafts. Tests are not to be made in a laboratory draft hood or near ventilators.
8.2 Natural gas and bottled gas flame and electric ignitors have been found acceptable for use as the ignition source. (Warning - Gas pressure supplied to the apparatus must not be allowed to exceed 3 kPa (12 in.) of water pressure.)
8.3 For flash points below 13°C (55°F) or above 60°C (140°F), use as a bath liquid a 1 + 1 mixture of water and ethylene glycol (Warning - Ethylene Glycol - Poison. Harmful or fatal if swallowed. Vapor harmful. Avoid contact with skin.) For flash points between 13°C (55°F) and 60°C (140°F), either water or a water-glycol mixture can be used as bath liquid. The temperature of the liquid in the bath shall be at least 10°C (18°F) below the expected flash point at the time of introduction of the sample into the test cup. Do not cool bath liquid by direct contact with dry ice (solid carbon dioxide).
NOTE 3 - Due to possible difficulty in maintaining the prescribed rate of temperature rise and due to the formation of ice on the lid, results by this test method for samples having flash points below 0°C (32°F) may be unreliable. Trouble due to ice formation on the slide can be minimized by carefully lubricating the slide shutter with high-vacuum silicone lubricant.
8.4 Verify the performance of the manual apparatus (or in 11.2.3, the automated apparatus) at least once per year by determining the flash point of a certified reference material (CRM), such as those listed in Annex A2, which is reasonably close to the expected temperature range of the samples to be tested. The material shall be tested according to the procedure of this test method and the observed flash point obtained in 9.5 shall be corrected for barometric pressure (see Section 13). The flash point obtained shall be within the limits stated in Table A2.1 for the identified CRM or within the limits calculated for an unlisted CRM (see Annex A2).
8.5 Once the performance of the apparatus has been verified, the flash point of secondary working standards (SWSs) can be determined along with their control limits. These secondary materials can then be utilized for more frequent performance checks (see Annex A2).
8.6 When the flash point obtained is not within the limits stated in 8.4 or 8.5, check the condition and operation of the apparatus to ensure conformity with the details listed in Annex A1, especially with regard to tightness of the lid (see A1.1.3), the action of the shutter, the position of the ignition source (see A1.1.3.3), and the angle and position of the temperature measuring device (see A1.1.3.4). After any adjustment, repeat the test in 8.4 using fresh test specimen, with special attention to the procedural details prescribed in the test method.
9. Procedure (Manual)
9.1 Using a graduated cylinder and taking care to avoid wetting the cup above the final liquid level, measure 50 more or less 0.5 mL of the sample into the cup, both the sample and graduated cylinder being precooled, when necessary, so that the specimen temperature at the time of measurement will be 27 more or less 5°C (80 more or less 10°F) or at least 10°C (18°F) below the expected flash point, whichever is lower. It is essential that the sample temperature be maintained at least 10°C (18°F) below the expected flash point during the transfers from the sample container to the cylinder and from the cylinder to the test cup. Destroy air bubbles on the surface of the specimens by use of knife point or other suitable device. Wipe the inside of the cover with a clean cloth or absorbent tissue paper; then attach the cover, with the temperature measuring device in place, to the bath collar.
9.2 Light the test flame, when used, adjusting it to the size of the small bead on the cover. Operate the mechanism on the cover in such a manner as to introduce the ignition source into the vapor space of the cup, and immediately bring it up again. The time consumed for the full operation should be 1 s, allowing equal time periods for the introduction and return. Avoid any hesitation in the operation of depressing and raising the ignition source. When a flash is observed on the initial operation of the mechanism, discontinue the test and discard the result. In this case, a fresh sample shall be cooled an additional 10°C (18°F), below the original specimen installation temperature.
9.2.1 Exercise care when using a test flame, if the flame is extinguished it cannot ignite the specimen and the gas entering the vapor space can influence the result. When the flame is prematurely extinguished the test shall be discontinued and any result discarded.
9.3 Flash Points Below 60°C (140°F) - When the flash point of the sample is known to be below 60°C (140°F), apply and adjust the heat so that the temperature of the portion will rise at a rate of 1°C (2°F)/min more or less 6 s. When the temperature of the specimen in the test cup is 5°C (10°F) below its expected flash point, apply the ignition source in the manner just described in 9.2 and repeat the application of the ignition source after each 0.5°C (1°F) rise in temperature of the specimen.
9.4 Flash Points at 60°C (140°F) or Above - If the flash point of the sample is known to be 60°C (140°F) or higher, apply and adjust the heat so that the temperature of the specimen will rise at a rate of 3°C (5°F)/min more or less 6 s. When the temperature of the specimen in the test cup is 5°C (10°F) below its expected flash point, apply the ignition source in the manner just described in 9.2 and repeat the application of the ignition source each 1°C (2°F) rise in temperature of the specimen.
9.5 When the application of the ignition source causes a distinct flash in the interior of the cup, as defined in 3.1.1, observe and record the temperature of the specimen as the flash point. Do not confuse the true flash with the bluish halo that sometimes surrounds the ignition source during applications immediately preceding the actual flash. (Warning - For certain mixtures containing halogenated hydrocarbons, such as, methylene chloride or trichloroethylene, no distinct flash, as defined, is observed. Instead a significant enlargement of the test flame (not halo effect) and change in color of the test flame from blue to yellowish-orange occurs. Continued heating and testing of these samples above ambient temperature can result in significant burning of vapors outside the test cup, and can be a potential fire hazard. See Appendix X1 and Appendix X2 for more information.)
9.6 Discontinue the test and remove the source of heat. Lift the lid and wipe the temperature measuring device bulb. Remove the test cup, empty, and wipe dry.
9.7 If, at any time between the first introduction of the ignition source and the observation of the flash point, the rise in temperature of the specimen is not within the specified rate, discontinue the test, discard the result and repeat the test, adjusting the source of heat to secure the proper rate of temperature rise, or using a modified "expected flash point", or both, as required.
9.8 Never make a repeat test on the same specimen of sample; always take fresh specimen of sample for each test.
