1、Designation: D6743 06 (Reapproved 2011)Standard 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 revision, the year of
2、 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. Scope1.1 This test method covers the determination of the thermalstability of unused organic heat transfer fluids. The procedu
3、reis applicable to fluids used for the transfer of heat at tempera-tures both above and below their boiling point (refers to normalboiling point throughout the text unless otherwise stated). It isapplicable to fluids with maximum bulk operating temperaturebetween 260C (500F) and 454C (850F). The pro
4、cedureshall not be used to test a fluid above its critical temperature. Inthis test method, the volatile decomposition products are incontinuous contact with the fluid during the test. This testmethod will not measure the thermal stability threshold (thetemperature at which volatile oil fragments be
5、gin to form), butinstead will indicate bulk fragmentation occurring for a speci-fied temperature and testing period. Because potential decom-position and generation of high pressure gas may occur attemperatures above 260C (500F), do not use this test methodfor aqueous fluids or other fluids which ge
6、nerate high-pressuregas at these temperatures.1.2 DIN Norm 51528 covers a test method that is similar tothis test method.1.3 The applicability of this test method to siloxane-basedheat transfer fluids has not been determined.1.4 The values stated in SI units are to be regarded asstandard. The values
7、 given in parentheses are for informationonly.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regul
8、atory limitations prior to use. For specificwarning statements, see 7.2, 8.8, 8.9, and 8.10.2. Referenced Documents2.1 ASTM Standards:2D2887 Test Method for Boiling Range Distribution ofPetroleum Fractions by Gas ChromatographyD4175 Terminology Relating to Petroleum, PetroleumProducts, and Lubricant
9、s2.2 DIN Norms:351528 Determination of the Thermal Stability of UnusedHeat Transfer Fluids3. Terminology3.1 Definitions:3.1.1 thermal stability, nthe resistance to permanentchanges in properties caused solely by heat. D41753.2 Definitions of Terms Specific to This Standard:3.2.1 decomposition produc
10、ts that cannot be vaporized,nmaterials from the thermally stressed heat transfer fluid,from which those fractions that can be vaporized are removedby distillation procedures, that are quantitatively determined asresidues in a bulb tube distillation apparatus.3.2.2 fluid within the unstressed fluid b
11、oiling range, nanyfluid components with boiling point between the initial boilingpoint and final boiling point of the unstressed fluid.3.2.3 gaseous decomposition products, nmaterials withboiling points below room temperature, at normal pressure,such as hydrogen and methane, that escape upon opening
12、 thetest cell and that can be determined by measuring the massimmediately thereafter.3.2.4 high boiling components, nmaterials from the ther-mally stressed heat transfer fluid, with boiling points above thefinal boiling point of the unstressed heat transfer fluid, butwhich can still be separated by
13、distillation from the heattransfer fluid by means of classical separation procedures.3.2.5 low boiling components, nmaterials from the ther-mally stressed heat transfer fluid, with boiling points below theinitial boiling point of the unstressed heat transfer fluid.3.2.6 mass percentage of high boili
14、ng components, nthepercentage of thermally stressed heat transfer fluid with aboiling point above the final boiling point of the unstressedfluid.3.2.7 mass percentage of low boiling components, nthepercentage of thermally stressed heat transfer fluid with aboiling point below the initial boiling poi
15、nt of the unstressedfluid.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.L0.06 on Non-Lubricating Process Fluids.Current edition approved May 1, 2011. Published August 2011. Originallyapproved
16、in 2001. Last previous edition approved in 2006 as D674306. DOI:10.1520/D6743-06R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary p
17、age onthe ASTM website.3Available from Deutsches Institut fur Normung e.V.(DIN), Burggrafenstrasse 6,10787 Berlin, Germany, http:/www.din.de.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.8 test cell, nan ampoule constructed fro
18、m stainlesssteel tubing and sealed with compression fittings at each end.3.2.9 thermally stressed, adjsubjected to heating, as de-scribed in this test method.4. Summary of Test Method4.1 Charge the test fluid in a thermal stability test cellpurged with nitrogen and tightly seal the test cell to remo
19、ve andpreclude introduction of oxygen and water from the atmo-sphere. Heat the fluid in an oven at a given temperature and fora given period of time. Determine the boiling range of theheated fluid by gas chromatography (GC) analysis and com-pare it to the boiling range of pure, unused fluid.5. Signi
20、ficance and Use5.1 Heat transfer fluids degrade when exposed to suffi-ciently high temperatures. The amount of degradation in-creases as the temperature increases or the length of exposureincreases, or both. Due to reactions and rearrangement, degra-dation products can be formed. Degradation product
21、s includehigh and low boiling components, gaseous decompositionproducts, and products that cannot be evaporated. The type andcontent of degradation products produced will change theperformance characteristics of a heat transfer fluid. In order toevaluate thermal stability, it is necessary to quantit
22、ativelydetermine the mass percentages of high and low boilingcomponents, as well as gaseous decomposition products andthose that cannot be vaporized, in the thermally stressed heattransfer fluid.5.2 This test method differentiates the relative stability oforganic heat transfer fluids at elevated tem
23、peratures in theabsence of oxygen and water under the conditions of the test.5.3 The user shall determine to his own satisfaction whetherthe results of this test method correlate to field performance.Heat transfer fluids in industrial plants are exposed to a varietyof additional influencing variable
24、s. Interaction with the plantsmaterials, impurities, heat build-up during impaired flowconditions, the temperature distribution in the heat transferfluid circuit, and other factors can also lead to changes in theheat transfer fluid. The test method provides an indication ofthe relative thermal stabi
25、lity of a heat transfer fluid, and can beconsidered as one factor in the decision-making process forselection of a fluid.5.4 The accuracy of the results depends very strongly onhow closely the test conditions are followed.5.5 This test method does not possess the capability toquantify or otherwise a
26、ssess the formation and nature ofthermal decomposition products within the unstressed fluidboiling range. Decomposition products within the unstressedfluid boiling range may represent a significant portion of thetotal thermal degradation.6. Apparatus6.1 Test CellThe test cell shall be a new, clean a
27、mpoulemade from ASTM A-269 grade 316L stainless steel tubing, 25mm (1 in.) outside diameter, 2 mm (0.083 in.) wall thickness.The test cell shall be 0.152 6 0.003 m (6 6 0.125 in.) in lengthand sealed with compression fittings at each end.NOTE 1Where tubing with SI dimensions is not readily available
28、, theuse of tubing with inch-pound dimensions is acceptable.6.2 Heating OvenThe oven shall be capable of beingcontrolled within 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 Dist
29、illation ApparatusThis apparatus shallbe capable of heating to at least 250C (482F) and pressuredown to at least 0.1 mm Hg.6.4 Dewar FlaskThe flask is used to hold the test cellsduring cooling after removal from the heating oven.6.5 BalanceThe balance shall be capable of measuringmass to the nearest
30、 0.01 g.7. Preparation of Apparatus7.1 Test CellThe test cell used shall always be a clean,new ampoule. Reuse of ampoules is not permitted.7.2 Cleaning of Test CellA new test cell shall be cleanedby washing with a suitable volatile solvent such as acetone anddried. (WarningUse adequate safety precau
31、tions with allsolvents and cleaners.)8. Procedure8.1 Determine the initial boiling point (IBP) and finalboiling point (FBP) of the unstressed heat transfer fluid by GC,in accordance with Test Method D2887 with the followingrequirements: the column shall be wall-coated open tubulartype of 7.5 to 10 m
32、 length with a 100 % polydimethylsiloxanefilm thickness of 0.88 m, the detector shall be flame ionizationtype, the initial oven temperature shall be set to 35C (95F)eliminating cryogenic cooling, the calibration mixture shallcover the boiling range from n-C5to n-C60. The following GCparameters are r
33、ecommended: oven temperature rate 10C(18F) per minute, oven final temperature 375C (707F), timeat oven final temperature 3 min, injector initial temperature100C (212F), injector temperature rate 10C (18F) perminute, injector final temperature 375C (707F), detectortemperature 375C (707F).8.2 Measure
34、the mass of a clean, dry test cell includingcompression fittings to the nearest 0.01 g. Pour the unstressedheat transfer fluid into the clean, dry test cell in a verticalposition. The quantity of heat transfer fluid transferred to thetest cell shall be 27 g 6 0.2 g. Invert the test cell in a vertica
35、lposition and allow it to drain until all free-flowing material hasbeen removed. More viscous fluids may require as long as 15min to drain completely. At the end of the draining period, tapthe test cell to remove a drop clinging to the open end of thetest cell do not wipe away any fluid. Measure the
36、 mass of thetest cell and its remaining contents including compressionfittings to the nearest 0.01 g.NOTE 2The intent is to perform this step only once for each heattransfer fluid being tested at this time.8.3 Measure the mass of a clean, dry test cell includingcompression fittings to the nearest 0.
37、01 g. Introduce high puritynitrogen using tubing at the bottom of the clean, dry test cellfor 2 min at 60 to 70 mL/min.NOTE 3To ensure accurate results, at least three test cells containingsamples of the same heat transfer fluid should be heated simultaneously.D6743 06 (2011)28.4 Pour the thermally
38、unstressed heat transfer fluid into theclean, dry test cell. The quantity of heat transfer fluid trans-ferred to the test cell shall be 27 g 6 0.2 g.8.5 Completely displace the air remaining in the gas spacein the test cell by introducing high purity nitrogen using tubingjust above the liquid surfac
39、e of fluid inside the test cell at 30 to35 mL/min for 12 min at ambient temperature.8.6 Carefully seal the test cell and measure its mass to thenearest 0.01 g.8.7 Insert the test cell vertically in the oven. Adjust theheating oven to the proper test temperature. The time toachieve proper test temper
40、ature should be approximately 3 h.The test temperature shall be maintained throughout the entiretest duration and controlled in such a way that the temperatureof the test liquid does not deviate by more than 61C (61.8F)at any location, including the heated wall. Temperature shall bemeasured and reco
41、rded throughout the test at least once perday. If test cells containing different fluids are tested at thesame time, the test cells shall be distributed symmetricallyinside the oven to minimize the effect of oven temperaturevariation on the results. The test duration shall be the time fromattaining
42、the test temperature to the time the heat supply is cutoff. The test duration at the specified test temperature shall bea minimum of 500 h. The preferred test duration is 500 6 1h,however, a longer test duration may be used. Thermal degra-dation cannot be assumed to be linear with time. Therefore, t
43、hestability of two fluids can only be compared at the same testtemperature and test duration.8.8 Protect the oven from heat transfer fluid that may spill incase of damage by placing a collecting pan under the test cell.(WarningIf fluid leaks out due to improper sealing of thetest cell, there may be
44、the potential of flammable vapors insidethe oven. The oven design and installation should consider thispossibility.)8.9 At the conclusion of the heating period, shut off theoven. Do not immediately remove the test cell. Leave the ovenclosed and allow the oven and the test cell to cool to ambienttemp
45、erature to reduce the internal pressure. (WarningPressure inside the test cell may reach several thousand kPaduring the test.)8.10 Remove the test cell from the oven. (WarningUseadequate safety precautions when removing the test cells fromthe oven in case some portion of the equipment is still hot.)
46、8.11 Carefully measure the mass of the test cell to thenearest 0.01 g. If the evaporation loss of gaseous decomposi-tion products is calculated at greater than 0.5 mass %, the testshould be repeated since this would indicate tube leakage.8.12 Place the test cell in a Dewar flask containing a cooling
47、mixture of acetone or isopropanol and dry ice. Allow the testcell to cool to at least 55C (67F). The duration of coolingis approximately 5 to 10 min. Stand the test cell in a verticalposition and allow it to reach ambient temperature, thenexercise care to remove any condensed water on the exterior o
48、fthe test cell. Stand the test cell in a vertical position and openthe top of the test cell. Then measure the mass of the test cellincluding compression fittings and its contents to the nearest0.01 g. Put a portion of the fluid into sample bottles foranalytical evaluation and store the remainder for
49、 additionalmeasurement in a glass bottle that is hermetically sealed. Invertthe test cell and allow it to drain until all free-flowing materialhas been removed. More viscous fluids may require as long as15 min to drain completely. At the end of the draining period,tap the test cell to remove a drop clinging to the open end of thetest cell do not wipe away any fluid. Measure the mass of thetest cell and its remaining contents including compressionfittings to the nearest 0.01 g.8.13 Visually observe the appearance of the
