1、Designation: D 6468 06An American National StandardStandard Test Method forHigh Temperature Stability of 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 revision, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 conditi
3、ons 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 and for grades DMX and DMA in SpecificationD 2069. It is also suitable for similar fuels meeting otherspecifications.1.2 This test method is not suitable for fue
4、ls whose flashpoint, as determined by Test Methods 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.1.4 This standard does
5、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. Referenced Documents2.1 ASTM Standa
6、rds: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 Color Scale)D 2069 Specification for
7、 Marine Fuels3D 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 andPet
8、roleum 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 i
9、n thecourse 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 stabilit
10、ythe resistance 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
11、of fuel 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 filt
12、erable 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 Use45.1 This test method provides an indication of therma
13、loxidative stability of distillate fuels when heated to hightemperatures that simulate those that may occur in some types1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.14 on Stability and Clean
14、liness of Liquid Fuels.Current edition approved May 1, 2006. Published May 2006. Originallyapproved in 1999. Last previous edition approved in 2004 as D 646899(2004).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual B
15、ook of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Henry, C. P., “The du Pont F21 149C (300F) Accelerated Stability Test,”Distillate Fuel Stability and Cleanliness, ASTM STP 751, L. L. Stavinoha and C. P.Henry, Eds., ASTM, 1981, pp. 2
16、2-33.1*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.of recirculating engine or burner fuel delivery systems. Resultshave not been substantially correlated to engine o
17、r burneroperation. 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 stabili
18、ty 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 sat
19、isfactorilywith 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 inso
20、lubles, 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
21、.6.2 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 suc
22、h toenable 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.(Warn
23、ingThe 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 Thermometer, either glass or digital, whose accuracy inthe 140 to 160C range is cer
24、tified or traceable to a certifiedthermometer. Use to monitor the temperature of the heatingbath in 6.2.6.4 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 h
25、azards, an all metal filter holder equipped withgrounding cables is recommended.5Such 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 d
26、o not have uniform 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 m
27、aximum vacuum to 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
28、577 Digital Reflec-tion Meter, complete with search unit Y with a green filter andpolished black glass standard.6NOTE 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
29、 meter equipped withsearch unit W usually gives somewhat lower percent reflectance values.Correlation of these values is discussed in Appendix X1.NOTE 4Older reflection meters, including but not limited to PhotovoltModel 670 analog meter, are satisfactory.7. Reagents and Materials7.1 Purity of Reage
30、ntsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.7Other grades may be used,provided it is firs
31、t ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.2 Acetone, reagent grade. (WarningExtremely flam-mable.)7.3 Adherent Insolubles Solvent (Trisolvent or TAM),amixture of equal parts by volume of reagent grade toluene(W
32、arningFlammable. Vapor harmful), acetone (Warningsee 7.2), and methanol (WarningFlammable. Vapor harm-ful. May be fatal or cause blindness if swallowed or inhaled.Cannot be made nonpoisonous).7.4 Hydrocarbon Solvent, 2,2,4-trimethylpentane (iso-octane), 99.75 % purity minimum (Warningsee 7.2).NOTE 5
33、Heptane is a satisfactory alternative hydrocarbon solvent.However, small differences may be seen due to slightly different solubilitycharacteristics. Iso-octane is specified to be in agreement with thehydrocarbon solvent used in other middle distillate stability test methodssuch as Test Methods D 22
34、74 and D 4625.7.5 Filter Paper (Filter Pad), Whatman No. 1, 47-mmdiameter, or equivalent.NOTE 6Filter papers of 42.5 or 55-mm diameter are technically5The sole source of supply of the apparatus known to the committee at this timeis a suitable filter holder available from Millipore Corporation, 80 As
35、hby 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 will receive careful consideration at a meeting of the responsibletechnical committee,1which you may attend.6The sole source
36、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 you are aware of alternative suppliers, pleaseprovide this information to ASTM International Headquarters. Your comments w
37、illreceive careful consideration at a meeting of the responsible technical committee,1which you may attend.7Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, se
38、e Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D6468062satisfactory. Filters with a diameter of 47 mm permit a small unusedmargin for identifying the sample
39、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.Use only epoxy-lined cans or borosilicate glass bottles. Shieldclear glass bottles from sunlight to prevent photochemicalreactions.8.2
40、When samples are from a fuel or component rundownline, exercise care to ensure that the sampling line and valvingare thoroughly flushed with current mainstream sample.8.3 Because stability of some fuels, as determined in thistest method, changes over time, the sampling date shall berecorded; record
41、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 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 o
42、f sample.8.3.1 After taking the sample out of the cold storage, let itwarm to ambient temperature before the analysis to preventwater condensation.NOTE 7If multiple 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 doin
43、g 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 cloud point of the fuel is above 5C, warm to atemperature 5C higher than the cloud point before dispensing.9. Preparation of Apparatus9.1 Clea
44、ning Aging TubesClean new tubes using adherentinsolubles solvent, then with a mildly alkaline or neutrallaboratory detergent, followed by copious rinsing with deion-ized or distilled water to remove all traces of detergent. Thenrinse with acetone and air dry. Rinse used tubes with adherentinsolubles
45、 solvent, dry, then clean as above for new tubes.Visually inspect tubes before use, and reclean or reject if thereis the slightest trace of contamination.9.1.1 Because of the small sample size and the high surfaceto volume ratio in this test method, carefully avoid carryoverfrom past tests or from c
46、leaning agents. There are especiallystrong effects from traces of copper, strong acids, and strongbases.9.2 Cleaning Membrane Filter HolderRinse with adher-ent insolubles solvent, acetone, and air dry.10. Calibration and Standardization10.1 Turn on the reflection meter and allow at least 30 minfor w
47、arm-up. The gain should be set in LO position for searchunit Y with green filter.10.2 Follow the manufacturers instructions to carry out atwo point calibration of the reflection meter, using the blackstandard and standard plaque supplied with the search unit.NOTE 8The calibration procedure ensures t
48、hat 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 paper 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 adj
49、ust 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 (if necessary) adjust the meter reading to 0 %,using the ZERO control. Recheck the 100 % adjustmentagainst the new filter paper, and continue adjustment until themeter reads both 0 % with the black glass standar
