1、Designation:D674306 (Reapproved 2011) Designation: D6743 11Standard Test Method forThermal Stability of Organic Heat Transfer Fluids1This standard is issued under the fixed designation D6743; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the thermal stability of unused organic heat transf
3、er fluids. The procedure isapplicable to fluids used for the transfer of heat at temperatures both above and below their boiling point (refers to normal boilingpoint throughout the text unless otherwise stated). It is applicable to fluids with maximum bulk operating temperature between260C (500F) an
4、d 454C (850F). 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 thethermal stability threshold (the temperature at which
5、volatile oil fragments begin to form), but instead will indicate bulkfragmentation occurring for a specified temperature and testing period. Because potential decomposition and generation of highpressure gas may occur at temperatures above 260C (500F), do not use this test method for aqueous fluids
6、or other fluids whichgenerate 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 regar
7、ded 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 responsibilityof the user of this standard to establish appropriate safety and health practices and determine
8、 the applicability of regulatorylimitations prior to use. For specific warning statements, see 7.2, 8.8, 8.9, and 8.10.2. Referenced Documents2.1 ASTM Standards:2D2887 Test Method for Boiling Range Distribution of Petroleum Fractions by Gas ChromatographyD4175 Terminology Relating to Petroleum, Petr
9、oleum Products, and Lubricants Terminology Relating to Petroleum, PetroleumProducts, and LubricantsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method2.2 DIN Norms:351528 Determination of the Thermal Stability of Unused Heat Transfer Fluids3. Terminology
10、3.1 Definitions:3.1.1 thermal stability, nthe resistance to permanent changes in properties caused solely by heat. D41753.2 Definitions of Terms Specific to This Standard:3.2.1 decomposition products that cannot be vaporized, nmaterials from the thermally stressed heat transfer fluid, from whichthos
11、e fractions that can be vaporized are removed by distillation procedures, that are quantitatively determined as residues in a bulbtube distillation apparatus.3.2.2 fluid within the unstressed fluid boiling range, nany fluid components with boiling point between the initial boiling pointand final boi
12、ling point of the unstressed fluid.3.2.3 gaseous decomposition products, nmaterials with boiling points below room temperature, at normal pressure, such ashydrogen and methane, that escape upon opening the test cell and that can be determined by measuring the mass immediatelythereafter.3.2.4 high bo
13、iling components, nmaterials from the thermally stressed heat transfer fluid, with boiling points above the final1This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.L0.06on Non-Lubricating Process
14、 Fluids.Current edition approved MayDec. 1, 2011. Published August 2011.February 2012. Originally approved in 2001. Last previous edition approved in 20062011 asD674306(2011). DOI: 10.1520/D6743-06R11.10.1520/D6743-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact A
15、STM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3Available from Deutsches Institut fur Normung e.V.(DIN), Burggrafenstrasse 6, 10787 Berlin, Germany, http:/www.din.de.1This document is not
16、an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate.
17、 In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.boi
18、ling point of the unstressed heat transfer fluid, but which can still be separated by distillation from the heat transfer fluid bymeans of classical separation procedures.3.2.5 low boiling components, nmaterials from the thermally stressed heat transfer fluid, with boiling points below the initialbo
19、iling point of the unstressed heat transfer fluid.3.2.6 mass percentage of high boiling components, nthe percentage of thermally stressed heat transfer fluid with a boilingpoint above the final boiling point of the unstressed fluid.3.2.7 mass percentage of low boiling components, nthe percentage of
20、thermally stressed heat transfer fluid with a boilingpoint below the initial boiling point of the unstressed fluid.3.2.8 test cell, nan ampoule constructed from stainless steel tubing and sealed with compression fittings at each end.3.2.9 thermally stressed, adjsubjected to heating, as described in
21、this test method.4. Summary of Test Method4.1 Charge the test fluid in a thermal stability test cell purged with nitrogen and tightly seal the test cell to remove and precludeintroduction of oxygen and water from the atmosphere. Heat the fluid in an oven at a given temperature and for a given period
22、of time. Determine the boiling range of the heated fluid by gas chromatography (GC) analysis and compare it to the boiling rangeof pure, unused fluid.5. Significance and Use5.1 Heat transfer fluids degrade when exposed to sufficiently high temperatures. The amount of degradation increases as thetemp
23、erature increases or the length of exposure increases, or both. Due to reactions and rearrangement, degradation products canbe formed. Degradation products include high and low boiling components, gaseous decomposition products, and products thatcannot be evaporated. The type and content of degradat
24、ion products produced will change the performance characteristics of a heattransfer fluid. In order to evaluate thermal stability, it is necessary to quantitatively determine the mass percentages of high andlow boiling components, as well as gaseous decomposition products and those that cannot be va
25、porized, in the thermally stressedheat transfer fluid.5.2 This test method differentiates the relative stability of organic heat transfer fluids at elevated temperatures in the absenceof oxygen and water under the conditions of the test.5.3 The user shall determine to his own satisfaction whether th
26、e results of this test method correlate to field performance. Heattransfer fluids in industrial plants are exposed to a variety of additional influencing variables. Interaction with the plants materials,impurities, heat build-up during impaired flow conditions, the temperature distribution in the he
27、at transfer fluid circuit, and otherfactors can also lead to changes in the heat transfer fluid. The test method provides an indication of the relative thermal stabilityof a heat transfer fluid, and can be considered as one factor in the decision-making process for selection of a fluid.5.4 The accur
28、acy of the results depends very strongly on how closely the test conditions are followed.5.5 This test method does not possess the capability to quantify or otherwise assess the formation and nature of thermaldecomposition products within the unstressed fluid boiling range. Decomposition products wi
29、thin the unstressed fluid boiling rangemay represent a significant portion of the total thermal degradation.6. Apparatus6.1 Test CellThe test cell shall be a new, clean ampoule made from ASTM A-269 grade 316L stainless steel tubing, 25 mm(1 in.) outside diameter, 2 mm (0.083 in.) wall thickness. The
30、 test cell shall be 0.152 6 0.003 m (6 6 0.125 in.) in length and sealedwith compression fittings at each end.NOTE 1Where tubing with SI dimensions is not readily available, the use of tubing with inch-pound dimensions is acceptable.6.2 Heating OvenThe oven shall be capable of being controlled withi
31、n 6 1C (6 1.8F) at test temperature. The testtemperature selected will typically be between 260C (500F) and 427C (800F), depending on the fluid being tested.6.3 Bulb Tube Distillation ApparatusThis apparatus shall be capable of heating to at least 250C (482F) and pressure downto at least 0.1 mm Hg.6
32、.4 Dewar FlaskThe flask is used to hold the test cells during cooling after removal from the heating oven.6.5 BalanceThe balance shall be capable of measuring mass to the nearest 0.01 g.7. Preparation of Apparatus7.1 Test CellThe test cell used shall always be a clean, new ampoule. Reuse of ampoules
33、 is not permitted.7.2 Cleaning of Test CellAnew test cell shall be cleaned by washing with a suitable volatile solvent such as acetone and dried.(WarningUse adequate safety precautions with all solvents and cleaners.)8. Procedure8.1 Determine the initial boiling point (IBP) and final boiling point (
34、FBP) of the unstressed heat transfer fluid by GC, inaccordance with Test Method D2887 with the following requirements: the column shall be wall-coated open tubular type of 7.5to 10 m length with a 100 % polydimethylsiloxane film thickness of 0.88 m, the detector shall be flame ionization type, the i
35、nitialD6743 112oven temperature shall be set to 35C (95F) eliminating cryogenic cooling, the calibration mixture shall cover the boiling rangefrom n-C5to n-C60. The following GC parameters are recommended: oven temperature rate 10C (18F) per minute, oven finaltemperature 375C (707F), time at oven fi
36、nal temperature 3 min, injector initial temperature 100C (212F), injector temperaturerate 10C (18F) per minute, injector final temperature 375C (707F), detector temperature 375C (707F).8.2 Measure the mass of a clean, dry test cell including compression fittings to the nearest 0.01 g. Pour the unstr
37、essed heattransfer fluid into the clean, dry test cell in a vertical position. The quantity of heat transfer fluid transferred to the test cell shallbe 27 g 6 0.2 g. Invert the test cell in a vertical position and allow it to drain until all free-flowing material has been removed.More viscous fluids
38、 may require as long as 15 min to drain completely.At the end of the draining period, tap the test cell to removea drop clinging to the open end of the test cell do not wipe away any fluid. Measure the mass of the test cell and its remainingcontents including compression fittings to the nearest 0.01
39、 g.NOTE 2The intent is to perform this step only once for each heat transfer fluid being tested at this time.8.3 Measure the mass of a clean, dry test cell including compression fittings to the nearest 0.01 g. Introduce high purity nitrogenusing tubing at the bottom of the clean, dry test cell for 2
40、 min at 60 to 70 mL/min.NOTE 3To ensure accurate results, at least three test cells containing samples of the same heat transfer fluid should be heated simultaneously.8.4 Pour the thermally unstressed heat transfer fluid into the clean, dry test cell. The quantity of heat transfer fluid transferredt
41、o the test cell shall be 27 g 6 0.2 g.8.5 Completely displace the air remaining in the gas space in the test cell by introducing high purity nitrogen using tubing justabove the liquid surface of fluid inside the test cell at 30 to 35 mL/min for 12 min at ambient temperature.8.6 Carefully seal the te
42、st cell and measure its mass to the nearest 0.01 g.8.7 Insert the test cell vertically in the oven. Adjust the heating oven to the proper test temperature. The time to achieve propertest temperature should be approximately 3 h. The test temperature shall be maintained throughout the entire test dura
43、tion andcontrolled in such a way that the temperature of the test liquid does not deviate by more than 61C (61.8F) at any location,including the heated wall. Temperature shall be measured and recorded throughout the test at least once per day. If test cellscontaining different fluids are tested at t
44、he same time, the test cells shall be distributed symmetrically inside the oven to minimizethe effect of oven temperature variation on the results. The test duration shall be the time from attaining the test temperature tothe time the heat supply is cut off. The test duration at the specified test t
45、emperature shall be a minimum of 500 h. The preferredtest duration is 500 6 1 h, however, a longer test duration may be used. Thermal degradation cannot be assumed to be linear withtime. Therefore, the stability of two fluids can only be compared at the same test temperature and test duration.8.8 Pr
46、otect the oven from heat transfer fluid that may spill in case of damage by placing a collecting pan under the test cell.(WarningIf fluid leaks out due to improper sealing of the test cell, there may be the potential of flammable vapors inside theoven. The oven design and installation should conside
47、r this possibility. )8.9 At the conclusion of the heating period, shut off the oven. Do not immediately remove the test cell. Leave the oven closedand allow the oven and the test cell to cool to ambient temperature to reduce the internal pressure. (WarningPressure inside thetest cell may reach sever
48、al thousand kPa during the test.)8.10 Remove the test cell from the oven. (Warning Use adequate safety precautions when removing the test cells from theoven in case some portion of the equipment is still hot.)8.11 Carefully measure the mass of the test cell to the nearest 0.01 g. If the evaporation
49、loss of gaseous decomposition productsis calculated at greater than 0.5 mass %, the test should be repeated since this would indicate tube leakage.8.12 Place the test cell in a Dewar flask containing a cooling mixture of acetone or isopropanol and dry ice. Allow the test cellto cool to at least 55C (67F). The duration of cooling is approximately 5 to 10 min. Stand the test cell in a vertical positionand allow it to reach ambient temperature, then exercise care to remove any condensed water on the exterior of the test cel
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