ASTM D6743 Standard Test Method for Thermal Stability of Organic Heat Transfer Fluids
1. Scope
1.1 This test method covers the determination ofthe thermal stability of unused organic heat transfer fluids. The procedure is applicable to fluids used for the transfer of heat at temperatures both above and below their boiling point (refers to normal boiling point throughout the text unless otherwise stated). It is applicable to fluids with maximum bulk operating temperature between 260 °C (500 °F) and 454 °C (850 °F). The procedure shall not be used to test a fluid above its critical temperature. In this test method, the volatile decomposition products are in continuous contact with the fluid during the test. This test method will not measure the thermal stability threshold (the temperature at which volatile oil fragments begin to form), but instead will indicate bulk fragmentation occurring for a specified temperature and testing period. Because potential decomposition and generation of high pressure gas may occur at temperatures above 260 °C (500 °F), do not use this test method for aqueous fluids or other fluids which generate high-pressure gas at these temperatures.
1.2 DIN Norm 51528 covers a test method that is similar to this test method.
1.3 The applicability of this test method to siloxane-based heat transfer fluids has not been determined.
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see 7.2, 8.8, 8.9, and 8.10.
2. Referenced Documents
2.1 ASTM Standards:
D2887 Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
D4175 Terminology Relating to Petroleum, Petroleum Products, and Lubricants
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 DIN Norms:
51528 Determination of the Thermal Stability of Unused Heat Transfer Fluids
3. Terminology
3.1 Definitions:
3.1.1 thermal stability, n - the resistance to permanent changes in properties caused solely by heat.
3.2 Definitions ofTerms Specific to This Standard:
3.2.1 decomposition products that cannot be vaporized, n - materials from the thermally stressed heat transfer fluid, from which those fractions that can be vaporized are removed by distillation procedures, that are quantitatively determined as residues in a bulb tube distillation apparatus.
3.2.2 fluid within the unstressed fluid boiling range, n - any fluid components with boiling point between the initial boiling point and final boiling point of the unstressed fluid.
3.2.3 gaseous decomposition products, n - materials with boiling points below room temperature, at normal pressure, such as hydrogen and methane, that escape upon opening the test cell and that can be determined by measuring the mass immediately thereafter.
3.2.4 high boiling components, n - materials from the thermally stressed heat transfer fluid, with boiling points above the final boiling point of the unstressed heat transfer fluid, but which can still be separated by distillation from the heat transfer fluid by means of classical separation procedures.
3.2.5 low boiling components, n - materials from the thermally stressed heat transfer fluid, with boiling points below the initial boiling point of the unstressed heat transfer fluid.
3.2.6 mass percentage of high boiling components, n - the percentage of thermally stressed heat transfer fluid with a boiling point above the final boiling point of the unstressed fluid.
3.2.7 mass percentage of low boiling components, n - the percentage of thermally stressed heat transfer fluid with a boiling point below the initial boiling point of the unstressed fluid.
3.2.8 test cell, n - an ampoule constructed from stainless steel tubing and sealed with compression fittings at each end.
3.2.9 thermally stressed, adj - subjected to heating, as described in this test method.
