ASTM D7236 Standard Test Method for Flash Point by Small Scale Closed Cup Tester (Ramp Method)
8. Sampling
8.1 Obtain at least a 25 mL sample from a bulk test site in accordance with Practices D4057, D4177, E300 or other comparable sampling practices.
8.2 Store samples in clean, tightly sealed containers at normal room temperature (20 °C to 25 °C) or colder. Ensure that the container is 85 % to 95 % full.
8.3 Do not store samples for an extended period of time in gas permeable containers, such as plastic, because volatile material may diffuse through the walls of the container. Samples in leaky containers are suspect and not a source of valid results.
8.4 Erroneously high flash points can be obtained when precautions are not taken to avoid loss ofvolatile materials. Do not open containers unnecessarily. Do not make a transfer unless the sample temperature is at least 10 °C below the expected flash point. Where possible perform the flash point as the first test on the sample.
8.5 Samples containing dissolved or free water may be dehydrated with calcium chloride. Warming the sample is permitted, but do not heat the sample above a temperature of 10 °C below its expected flash point. (Warning - If the sample is expected of containing volatile components, the treatment as described in 8.5 should be omitted.)
8.6 Cool or adjust the temperature of the sample and its container to at least 10 °C below the expected flash point before opening to remove the test specimen. Ifan aliquot of the original sample is to be stored prior to testing, ensure that the container is filled to between 85 % and 95 % of its capacity. Gently mix the subsample to ensure uniformity while minimizing the possible loss of volatile components and light ends.
NOTE 3 - Results of flash point tests may be affected if the sample volume falls below 85 % of the container's capacity.
9. Preparation of Apparatus
9.1 Support the apparatus (Annex A1) on a level and steady surface in a draft-free position (see Notes 4 and 5).
NOTE 4 - A draft shield (6.5) is recommended to be used when natural protection from drafts does not exist.
NOTE 5 - When testing materials that may produce toxic vapors, the apparatus may be located in a fume hood with an individual control of air flow, adjusted such that the toxic vapors can be withdrawn without causing air currents around the test cup during the test.
9.2 Clean the test cup, cover, and its accessories with an appropriate solvent (7.1) to remove traces of gum or residue from the previous test.
NOTE 6 - A stream ofclean dry air may be used to remove the last traces of solvent used.
NOTE 7 - The filler orifice may be cleaned with a pipe cleaner.
10. Verification of Apparatus
10.1 Verify that the temperature measuring device is in accordance with A1.7.
10.2 Verify the performance of the apparatus at least once per year by determining the flash point of a Certified Reference Material (CRM) that has a certified flash point reasonably close to the expected range of the samples to be tested. Examples of materials that may be used to create CRMs are listed in Appendix X1. The flash point shall be determined using the procedures stated in Section 11. Appendix X1 indicates typical limits in Table X1.1 for a typical CRM and shows how to calculate limits for an unlisted CRM.
10.3 Once the performance of the apparatus has been verified using a CRM, the flash point of Secondary Working Standards (SWS) can be determined along with their control limits. These SWS can then be utilized for more frequent performance checks. (See Appendix X1.)
10.4 When the flash point obtained is not within the limits stated in 10.2 or 10.3 check the condition and operation of the apparatus to ensure conformance to the details listed in Annex A1, especially with regard to the action of the shutter, the position and size of the test flame, the heating rate and the temperature sensor readings. After any adjustment, repeat the test in 10.2 or 10.3 using a fresh test specimen, with special attention to the procedural details prescribed in the test method.
