1、Designation: D6743 11 (Reapproved 2015)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 260 C (500 F) and 454 C (850 F). The
4、 procedureshall 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 fragment
5、s begin 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 260 C (500 F), do not use this testmethod for aqueous fluids or other fluids wh
6、ich generatehigh-pressure gas 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
7、values 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
8、 regulatory 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 of Pe-troleum Fractions by Gas ChromatographyD4175 Terminology Relating to Petroleum, PetroleumProducts, and L
9、ubricantsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 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 c
10、aused 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 which those fractions that can be vaporized are removedby distillation procedures, that are quantitative
11、ly determined asresidues in a bulb tube distillation apparatus.3.2.2 fluid within the unstressed fluid boiling 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
12、points below room temperature, at normal pressure,such as hydrogen and methane, that escape upon opening 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
13、 above thefinal boiling point of the unstressed heat transfer fluid, but1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.L0.06 on Non-Lubricating Process Fluids.Current edition app
14、roved July 1, 2015. Published July 2015. Originally approvedin 2001. Last previous edition approved in 2011 as D6743 11. DOI: 10.1520/D6743-11R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
15、 volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Deutsches Institut fur Normung e.V.(DIN), Burggrafenstrasse 6,10787 Berlin, Germany, http:/www.din.de.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-295
16、9. United States1which can still be separated by 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 t
17、ransfer fluid.3.2.6 mass percentage of high boiling 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
18、with aboiling point below the initial boiling point of the unstressedfluid.3.2.8 test cell, nan ampoule constructed from 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 Meth
19、od4.1 Charge the test fluid in a thermal stability test cellpurged with nitrogen and tightly seal the test cell to remove 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
20、theheated fluid by gas chromatography (GC) analysis and com-pare it to the boiling range of pure, unused fluid.5. Significance 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 e
21、xposureincreases, or both. Due to reactions and rearrangement, degra-dation products can be formed. Degradation products includehigh and low boiling components, gaseous decompositionproducts, and products that cannot be evaporated. The type andcontent of degradation products produced will change the
22、performance characteristics of a heat transfer fluid. In order toevaluate thermal stability, it is necessary to quantitativelydetermine the mass percentages of high and low boilingcomponents, as well as gaseous decomposition products andthose that cannot be vaporized, in the thermally stressed heatt
23、ransfer fluid.5.2 This test method differentiates the relative stability oforganic heat transfer fluids at elevated temperatures 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
24、 field performance.Heat transfer fluids in industrial plants are exposed to a varietyof additional influencing variables. Interaction with the plantsmaterials, impurities, heat build-up during impaired flowconditions, the temperature distribution in the heat transferfluid circuit, and other factors
25、can also lead to changes in theheat transfer fluid. The test method provides an indication ofthe relative thermal stability 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
26、closely the test conditions are followed.5.5 This test method does not possess the capability toquantify or otherwise assess the formation and nature ofthermal decomposition products within the unstressed fluidboiling range. Decomposition products within the unstressedfluid boiling range may represe
27、nt a significant portion of thetotal thermal degradation.6. Apparatus6.1 Test CellThe test cell shall be a new, clean ampoulemade from ASTM A-269 grade 316L stainless steel tubing,25 mm (1 in.) outside diameter, 2 mm (0.083 in.) wall thick-ness. The test cell shall be 0.152 m 6 0.003 m (6 in. 60.125
28、 in.) in length and sealed with compression fittings ateach end.NOTE 1Where tubing with SI dimensions is not readily available, theuse of tubing with inch-pound dimensions is acceptable.6.2 Heating OvenThe oven shall be capable of beingcontrolled within 61C(61.8 F) at test temperature. The testtempe
29、rature selected will typically be between 260 C (500 F)and 427 C (800 F), depending on the fluid being tested.6.3 Bulb Tube Distillation ApparatusThis apparatus shallbe capable of heating to at least 250 C (482 F) and pressuredown to at least 0.1 mm Hg.6.4 Dewar FlaskThe flask is used to hold the te
30、st cellsduring cooling after removal from the heating oven.6.5 BalanceThe balance shall be capable of measuringmass 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 is not permitted.7.2 Cleaning of Test CellA new
31、test cell shall be cleanedby washing with a suitable volatile solvent such as acetone anddried. (WarningUse adequate safety precautions 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
32、 accordance with Test Method D2887 with the followingrequirements: the column shall be wall-coated open tubulartype of 7.5 m to 10 m length with a 100 % polydimethylsilox-ane film thickness of 0.88 m, the detector shall be flameionization type, the initial oven temperature shall be set to35 C (95 F)
33、 eliminating cryogenic cooling, the calibrationmixture shall cover the boiling range from n-C5to n-C60. Thefollowing GC parameters are recommended: oven temperaturerate 10 C (18 F) per minute, oven final temperature 375 C(707 F), time at oven final temperature 3 min, injector initialtemperature 100
34、C (212 F), injector temperature rate 10 C(18 F) per minute, injector final temperature 375 C (707 F),detector temperature 375 C (707 F).8.2 Measure the mass of a clean, dry test cell includingcompression fittings to the nearest 0.01 g. Pour the unstressedD6743 11 (2015)2heat transfer fluid into the
35、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 verticalposition and allow it to drain until all free-flowing material hasbeen removed. More viscous fluids may require as long as15 min to dra
36、in completely. At the end of the draining period,tap the test cell to remove a drop clinging to the open end of thetest celldo not wipe away any fluid. Measure the mass of thetest cell and its remaining contents including compressionfittings to the nearest 0.01 g.NOTE 2The intent is to perform this
37、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 0.01 g. Introduce high puritynitrogen using tubing at the bottom of the clean, dry test cellfor 2 min at 60 mL min to 70 mL min.NOTE 3To en
38、sure accurate results, at least three test cells containingsamples of the same heat transfer fluid should be heated simultaneously.8.4 Pour the thermally 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
39、 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 surface of fluid inside the test cell at30 mL min to 35 mL min for 12 min at ambient temperature.8.6 Carefully seal the test cell and measure its mass t
40、o 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 temperature should be approximately 3 h.The test temperature shall be maintained throughout the entiretest duration and controlled in such a way
41、that the temperatureof the test liquid does not deviate by more than 61C(61.8 F) at any location, including the heated wall. Tempera-ture shall be measured and recorded throughout the test at leastonce per day. If test cells containing different fluids are testedat the same time, the test cells shal
42、l be distributed symmetri-cally inside the oven to minimize the effect of oven tempera-ture variation on the results. The test duration shall be the timefrom attaining the test temperature to the time the heat supplyis cut off. The test duration at the specified test temperatureshall be a minimum of
43、 500 h. The preferred test duration is500 h 6 1 h, however, a longer test duration may be used.Thermal degradation cannot be assumed to be linear with time.Therefore, the stability of two fluids can only be compared atthe same test temperature and test duration.8.8 Protect the oven from heat transfe
44、r 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 the potential of flammable vapors insidethe oven. The oven design and installation should consider thispossibility. )8.9 At the con
45、clusion 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 ambienttemperature to reduce the internal pressure. (WarningPressure inside the test cell may reach several thousand kPaduring the test.)8.10
46、 Remove the test cell from the oven. (Warning Useadequate safety precautions when removing the test cells fromthe oven in case some portion of the equipment is still hot.)8.11 Carefully measure the mass of the test cell to thenearest 0.01 g. If the evaporation loss of gaseous decomposi-tion products
47、 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 coolingmixture of acetone or isopropanol and dry ice. Allow the testcell to cool to at least 55 C (67 F). The duration of coolingis appr
48、oximately 5 min to 10 min. Stand the test cell in avertical position and allow it to reach ambient temperature,then exercise care to remove any condensed water on theexterior of the test cell. Stand the test cell in a vertical positionand open the top of the test cell. Then measure the mass of thete
49、st cell including compression fittings and its contents to thenearest 0.01 g. Put a portion of the fluid into sample bottles foranalytical evaluation and store the remainder for 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 celldo no
