1、Designation: D 6468 08An American National StandardStandard Test Method forHigh Temperature Stability of Middle Distillate Fuels1This standard is issued under the fixed designation D 6468; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revi
2、sion, 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 relative stability of middledistillate fuels under high temperature aging c
3、onditions withlimited air exposure. This test method is suitable for all No. 1and No. 2 grades in Specifications D 396, D 975, D 2880, andD 3699. It is also suitable for similar fuels meeting otherspecifications.1.2 This test method is not suitable for fuels whose flashpoint, as determined by Test M
4、ethods D56, D93,orD 3828,is less than 38C. This test method is not suitable for fuelscontaining residual oil.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3.1 ExceptionThe maximum vacuum includes inch-pound units in 6.5
5、and 11.2.1.4 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 regulatory limitations prior to use.2. Ref
6、erenced Documents2.1 ASTM Standards:2D56 Test Method for Flash Point by Tag Closed Cup TesterD93 Test Methods for Flash Point by Pensky-MartensClosed Cup TesterD 396 Specification for Fuel OilsD 975 Specification for Diesel Fuel OilsD 1500 Test Method for ASTM Color of Petroleum Prod-ucts (ASTM Colo
7、r Scale)D 2274 Test Method for Oxidation Stability of DistillateFuel Oil (Accelerated Method)D 2880 Specification for Gas Turbine Fuel OilsD 3699 Specification for KerosineD 3828 Test Methods for Flash Point by Small Scale ClosedCup TesterD 4057 Practice for Manual Sampling of Petroleum andPetroleum
8、 ProductsD 4625 Test Method for Middle Distillate Fuel StorageStability at 43C (110F)D 5452 Test Method for Particulate Contamination in Avia-tion Fuels by Laboratory Filtration3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 adherent insolublesmaterial that is produced in thec
9、ourse of stressing distillate fuel and that adheres to theglassware after fuel has been flushed from the system.3.1.2 filterable insolublesmaterial that is produced in thecourse of stressing distillate fuel and that is capable of beingremoved from the fuel by filtration.3.1.3 inherent stabilitythe r
10、esistance to change whenexposed to air, but in the absence of other environmentalfactors such as water, reactive metal surfaces, and dirt.3.1.4 storage stabilitythe resistance of fuel to formationof degradation products when stored at ambient temperatures.3.1.5 thermal stabilitythe resistance of fue
11、l to formationof degradation products when thermally stressed.4. Summary of Test Method4.1 Two 50-mL volumes of filtered middle distillate fuel areaged for 90 or 180 min at 150C in open tubes with airexposure. After aging and cooling, the fuel samples are filteredand the average amount of filterable
12、 insolubles is estimated bymeasuring the light reflectance of the filter pads. The 100 and0 % extremes of the reflectance rating range are defined by anunused filter pad and a commercial black standard, respec-tively.5. Significance and Use35.1 This test method provides an indication of thermaloxida
13、tive stability of distillate fuels when heated to hightemperatures that simulate those that may occur in some typesof recirculating engine or burner fuel delivery systems. Results1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct r
14、esponsibility of SubcommitteeD02.14 on Stability and Cleanliness of Liquid Fuels.Current edition approved July 1, 2008. Published August 2008. Originallyapproved in 1999. Last previous edition approved in 2006 as D 646806.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontac
15、t ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Henry, C. P., “The du Pont F21 149C (300F) Accelerated Stability Test,”Distillate Fuel Stability and Cleanliness, ASTM STP 751, Stavinoha,
16、 L. L. andHenry, C. P., Eds., ASTM International, 1981, pp. 22-33.1*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.have not been substantially correlated to engine or b
17、urneroperation. The test method can be useful for investigation ofoperational problems related to fuel thermal stability.5.2 When the test method is used to monitor manufacture orstorage of fuels, changes in filter rating values can indicate arelative change in inherent stability. Storage stability
18、predic-tions are more reliable when correlated to longer-term storagetests, for example, Test Method D 4625, or other lowertemperature, long-term tests. When fuel samples are freshlyproduced, aging for 180 min, instead of the traditional 90-mininterval, tends to give a result correlating more satisf
19、actorilywith the above methods (see Appendix X2).5.3 The test method uses a filter paper with a nominalporosity of 11 m, which will not capture all of the sedimentformed during aging but allows differentiation over a broadrange. Reflectance ratings are also affected by the color offilterable insolub
20、les, which may not correlate to the mass of thematerial filtered from the aged fuel sample. Therefore, noquantitative relationship exists between the pad rating and thegravimetric mass of filterable insolubles.6. Apparatus6.1 Aging Tubes,253 200 mm, heavy wall test tubes madeof borosilicate glass.6.
21、2 Heating Bath, with liquid heating medium, thermostati-cally controlled to maintain the sample in the aging tube within1.5C of 150C. It must be large enough to hold aging tubesimmersed in the heating liquid to a depth above the level ofsamples in the tubes. The bath and its location shall be such t
22、oenable shielding of the samples from direct light during aging.The volume of bath and its heat recovery rate shall be such thatthe temperature of the medium does not drop more than 5Cwhen the maximum number of aging tubes are inserted, andrecovery to 150C shall not require more than 15 min.(Warning
23、The flash point of the liquid heating medium mustbe at least 180C. Bath vapors and oil sample vapors shall beproperly vented. Exposed hot surfaces on the apparatus and hotheating medium can cause severe burns.)6.3 Bath Thermometer, either glass or digital measuringtemperature measuring device, whose
24、 accuracy in the 140 to160C range is certified or traceable to a certified thermometer.6.4 Membrane Filter Holder, to fit 47-mm membrane filters,fitted to a heavy-walled 500-mL or 1-L vacuum flask.NOTE 1Several types of membrane filter holders are available. Toreduce electrostatic hazards, an all me
25、tal filter holder equipped withgrounding cables is recommended.4Such an apparatus and correctgrounding practices are described in Test Method D 5452. A fritted glassfilter holder is less preferred because of a tendency to become partiallyclogged during use so that filter pads that do not have unifor
26、m deposits areobtained. Glass filter holders that use a 75-m (200-mesh) screen tosupport the filter are available; however, since the screen can be anunbonded electrostatic charge collector, these are not recommended foruse with flammable liquids.6.5 Vacuum Source, that limits the maximum vacuum to
27、27kPa (200 mm Hg) below atmospheric pressure. The vacuumshould rise to 27 kPa within 10 to 15 s after the sample is addedto the filtration funnel.NOTE 2Use of reduced vacuum improves retention of particulate onthe relatively porous filter media.6.6 Reflection meter, Photovolt Model 577 Digital Refle
28、c-tion Meter, complete with search unit Y with a green filter andpolished black glass standard.5NOTE 3Other reflection meters or search units, or both, can be used,but they are likely to provide only similar (not identical) results. Forexample, Photovolt Model 577 digital reflection meter equipped w
29、ithsearch unit W usually gives somewhat lower percent reflectance values.Correlation of these values is discussed in Appendix X1.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to th
30、e specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.6Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determinati
31、on.7.2 Acetone,(WarningExtremely flammable.)7.3 Adherent Insolubles Solvent (Trisolvent or TAM),amixture of equal parts by volume of reagent grade toluene(WarningFlammable. Vapor harmful), acetone (Warningsee 7.2), and methanol (WarningFlammable. Vapor harm-ful. May be fatal or cause blindness if sw
32、allowed or inhaled.Cannot be made nonpoisonous).7.4 Hydrocarbon Solvent, 2,2,4-trimethylpentane (iso-octane), 99.75 % purity minimum (Warningsee 7.2).NOTE 4Heptane is a satisfactory alternative hydrocarbon solvent.However, small differences may be seen due to slightly different solubilitycharacteris
33、tics. Iso-octane is specified to be in agreement with thehydrocarbon solvent used in other middle distillate stability test methodssuch as Test Methods D 2274 and D 4625.7.5 Filter Paper (Filter Pad), Whatman No. 1, 47-mmdiameter, or equivalent.NOTE 5Filter papers of 42.5 or 55-mm diameter are techn
34、icallysatisfactory. Filters with a diameter of 47 mm permit a small unusedmargin for identifying the sample and fit all filtration apparatuses.8. Sampling8.1 When samples of a fuel batch are obtained to determinestability, obtain samples in accordance with Practice D 4057.4The sole source of supply
35、of the apparatus known to the committee at this timeis a suitable filter holder available from Millipore Corporation, 80 Ashby Rd.,Bedford, MA 01730; Catalog No. XX20 047 20. If you are aware of alternativesuppliers, please provide this information to ASTM International Headquarters.Your comments wi
36、ll receive careful consideration at a meeting of the responsibletechnical committee,1which you may attend.5The sole source of supply of the apparatus known to the committee at this timeis available from UMM Electronics Inc., Photovolt Instruments, 6911 HillsdaleCourt, Indianapolis, IN 46250-2062. If
37、 you are aware of alternative suppliers, pleaseprovide this information to ASTM International Headquarters. Your comments willreceive careful consideration at a meeting of the responsible technical committee,1which you may attend.6Reagent Chemicals, American Chemical Society Specifications , America
38、nChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC),
39、 Rockville,MD.D6468082Use only epoxy-lined cans or borosilicate glass bottles. Shieldclear glass bottles from sunlight to prevent photochemicalreactions.8.2 When samples are from a fuel or component rundownline, exercise care to ensure that the sampling line and valvingare thoroughly flushed with cu
40、rrent mainstream sample.8.3 Because stability of some fuels, as determined in thistest method, changes over time, the sampling date shall berecorded; record time and date if sample is from a fuel orcomponent rundown line. Samples should be stored at tem-peratures below 5C. If storage for more than a
41、 few days isexpected, oxygen should be removed from the fuel by subsur-face purging with a stream of nitrogen; for example, bybubbling nitrogen for 1 min/L of sample.8.3.1 If samples are taken out of cold storage, warm them toambient temperature and thoroughly mix prior to aliquotsampling.NOTE 6If m
42、ultiple analyses are to be performed on a sample, it is nota good practice to warm the whole sample repeatedly for this purpose.One way of doing this would be to pour an aliquot of the cold sample intoa graduated cylinder, cap, allow to warm, and then dispense into the agingtube for analysis. If the
43、 cloud point of the fuel is above 5C, warm to atemperature 5C higher than the cloud point before dispensing.9. Preparation of Apparatus9.1 Cleaning Aging TubesClean new tubes using adherentinsolubles solvent, then with a mildly alkaline or neutrallaboratory detergent, followed by copious rinsing wit
44、h deion-ized or distilled water to remove all traces of detergent. Thenrinse with acetone and air dry. Rinse used tubes with trisolvent,dry, then clean as above for new tubes. Visually inspect tubesbefore use, and reclean or reject if there is the slightest trace ofcontamination.9.1.1 Because of the
45、 small sample size and the high surfaceto volume ratio in this test method, carefully avoid carryoverfrom past tests or from cleaning agents. There are especiallystrong effects from traces of copper, strong acids, and strongbases.NOTE 7Clean test tubes carefully to avoid carryover from past tests or
46、from cleaning agents. As a result of the small sample size evaluated andthe high surface to volume ratio inherent to the test method, the resultsobtained can be greatly influenced by the presence of trace contaminantssuch as copper, strong acids, or strong bases.9.2 Cleaning Membrane Filter HolderRi
47、nse with trisol-vent, then with acetone, and air dry.10. Calibration and Standardization10.1 Turn on the reflection meter and allow at least 30 minfor warm-up. Set the gain to LO position for search unit Y withgreen filter.10.2 Follow the manufacturers instructions to carry out atwo point calibratio
48、n of the reflection meter, using the blackstandard and standard plaque supplied with the search unit.NOTE 8The calibration procedure ensures that the instrument isworking properly. It also indirectly sets a nominal 100 % reflectancesetting that is subsequently reset in 10.3.10.3 Place a new filter p
49、aper on top of a stack of at least tenunused Whatman No. 1 filters of the same size. Place thesearch unit on the center of the filter, and adjust the meterreading to 100 %, using the sensitivity control.NOTE 9Such adjustment, which sets the test method 100 % reflec-tance point, alters the reflectance scale; as a result, the reflection meter willno longer read the recited reflectance of the standard plaque.10.4 Place the search unit on the center of the black glassstandard, and adjust the meter reading to 0 %, using the ZEROcontrol. Recheck the
