1、Designation: D6748 02a (Reapproved 2017)Standard Test Method forDetermination of Potential Instability of Middle DistillateFuels Caused by the Presence of Phenalenes andPhenalenones (Rapid Method by PortableSpectrophotometer)1,2This standard is issued under the fixed designation D6748; the number im
2、mediately following the designation indicates the year oforiginal adoption or, in the case of revision, 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. Scope1.1 Th
3、is test method covers a procedure3for the rapiddetermination of phenalenes and phenalenones in middledistillate fuels, including marine, automotive, heating, and gasturbine fuel such as those specified in Specifications D396,D975, D2069, and D2880. Phenalenes and phenalenones affectthe potential ins
4、tability of fuels, leading to fuel degradationproducts during storage, which may cause performance prob-lems.1.2 This test method is applicable to both dyed and undyedfuels at all points in the distribution chain from refinery toend-user. It is not applicable to fuels containing residual oil.The por
5、table apparatus allows the whole test to be conductedon site or in a laboratory and does not require the test sampleto be heated.1.3 This test method is suitable for testing samples with arelative absorbance of up to 5.00 absorbance units (AU).NOTE 1The precision of the test method has been establis
6、hed onrelative absorbance up to 1.00AU. For relative absorbance above 1.00AUthe precision may not apply.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, hea
7、lth, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of Interna
8、tional Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:4D396 Specification for Fuel OilsD975 Specification for Diesel Fuel OilsD2069 Specification for Marine Fuels (Withdrawn 2003)5D288
9、0 Specification for Gas Turbine Fuel OilsD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace ContaminationD4625 Test Method for Middl
10、e Distillate Fuel StorageStability at 43 C (110 F)D5854 Practice for Mixing and Handling of Liquid Samplesof Petroleum and Petroleum ProductsD6468 Test Method for High Temperature Stability ofMiddle Distillate FuelsE131 Terminology Relating to Molecular SpectroscopyE275 Practice for Describing and M
11、easuring Performance ofUltraviolet and Visible Spectrophotometers2.2 Other Standards:6Def Stan 05-50 Methods for Testing Fuels and Lubricantsand Associated Products, Part 40 Storage Stability ofDiesel Fuels1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid
12、 Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.14 on on Stability, Cleanliness and Compatibility of LiquidFuels.Current edition approved Oct. 1, 2017. Published November 2017. Originallyapproved in 2002. Last previous edition approved in 2012 as D674802a (2012).DOI: 10.15
13、20/D6748-02AR17.2This test method is being jointly developed with the Institute of Petroleumwhere it is designated IP 463.3This process is covered by US Patent 5,378,632. Interested parties are invitedto submit information regarding the identification of an alternative(s) to thispatented item to AST
14、M International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee, whichyou may attend.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStan
15、dards volume information, refer to the standards Document Summary page onthe ASTM website.5The last approved version of this historical standard is referenced onwww.astm.org.6Available from United Kingdom Defence Standardization, Room 1138, Kenti-gern House, 65 Brown Street, Glasgow, G2 8EX. United
16、Kingdom.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment
17、of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1Def Stan 914 Fuel, Naval, Distillate NATO Code: F76 JointService, Designation DIESO F763. Terminology3.1 Definitions:3.1.1 For definitions of terms relating to a
18、bsorption spec-troscopy see Terminology E131. Terms of particular signifi-cance are the following:3.1.2 radiant energy, nenergy transmitted as electromag-netic waves.3.1.3 radiant power P, nthe rate at which energy istransported in a beam of radiant energy.3.2 Definitions of Terms Specific to This S
19、tandard:3.2.1 absorbance, A, nthe logarithm to the base 10 of thereciprocal of the transmittance, T. In symbols:A 5 log101/T! 52log10T (1)where:T = transmittance as defined in 3.2.5.3.2.2 absorbance units (AU), nunits of relative absor-bance reported by the portable spectrophotometer.3.2.3 pathlengt
20、h of test portion b, nthe distance in mm,measured in the direction of propagation of the beam of radiantenergy, between the surfaces of the portion on which theradiant energy is incident and the surface of the test portionfrom which it emerges.3.2.4 relative absorbance, nthe difference between theab
21、sorbance (near infrared-visible band results) measured at thetwo wavelengths, and reported in AU.3.2.5 transmittance, T, nthe ratio of the radiant powertransmitted by the test portion in the test cuvette to the radiantpower transmitted by the Reagent 1 control in the cuvette.Expressed in the followi
22、ng equation.T 5 PT/PR1(2)where:PT= radiant power transmitted by the test portion, andPR1= the radiant power transmitted by the Reagent 1control.4. Summary of Test Method4.1 A5 mLvolume of middle distillate fuel is mixed with anequal volume of an immiscible reagent solution. A secondreagent is then a
23、dded, the new blend mixed and allowed tosettle for 30 min. for two phases to separate. The top reagentlayer (darker) is then placed in the portable spectrophotometerand the relative absorbance of near infrared and visible light, atfixed single wavelengths, is measured instantaneously andautomaticall
24、y, and reported in AU.4.2 When mixed with the oil sample containing phenalenes,the oxidizing Reagent 2 oxidizes the phenalenes to phenale-nones which are subsequently converted to colored indolylphe-nalene salts by the acidic Reagent 1. The spectrophotometermeasures the absorbance of light caused by
25、 the colored saltswhile eliminating the effect of the initial color of the fuel. Theabsorbance of light is a measure of the concentration of thecolored salts that are formed.5. Significance and Use5.1 Storage stability depends on complex interactions. Itvaries with feedstock type and source, and the
26、 processing used.The rate of degradation may not change uniformly withtemperature. Chemical reactions may lead to a change in colorfollowed by the formation of soluble gums and insolublesediments. Insoluble sediments may overload filters, and plugnozzles and injectors.5.2 This test method, which doe
27、s not require the test sampleto be heated, uses a portable apparatus and allows tests to becarried out on site or in the laboratory to give a result within35 min.5.3 The potential beneficial effects of stability additives infuels may not be recognized by this test method. Therefore, theactual storag
28、e stability of middle distillate fuels with stabilityadditives may not be correctly indicated by these test results.5.4 The unstable reactive compounds (phenalenes and phe-nalenones) detected by this test method may be present in fuelscontaining catalytically cracked or straight run materials andcan
29、 affect the potential instability of the fuel.5.5 If this test method is used by any party for a rapidassessment of stability, it is the responsibility of partiesconcerned to decide whether or not this procedure yieldsmeaningful results.5.6 Interpretation of results and correlation with other testme
30、thods is given in Appendix X1.6. Apparatus76.1 Spectrophotometer, double beam, capable of measuringabsorbance at one visible wavelength in the range 600 nm to800 nm and one near infrared wavelength in the range 800 nmto 850 nm with a spectral bandwidth of 10 nm 6 2 nm and anaccuracy of 63 nm (see Fi
31、g. 1). The display shall have aresolution of 0.01 ofAU, and a repeatability of measurement of60.02 AU for ranges up to 1.00 AU. See Practice E275.NOTE 2The two wavelengths used are proprietary and are notadjustable.6.1.1 Zero Adjustment, a facility shall be incorporated toallow the absorbance measur
32、ed at the two individual wave-lengths to be set to zero when using Reagent 1 as a control.6.1.2 Absorbance Display, the relative absorbance, in AU,shall be the instantaneous difference between the absorbancemeasured at the two wavelengths. The peak wavelengthrepresents the absorption due to the colo
33、red indolylphenalenesalts which are formed, and the baseline wavelength is fornormalizing the result.6.2 Timer, capable of measuring 35 min to an accuracy of60.2 min.7The equipment, as listed in RR:D02-1522 was used to develop the precisionstatement. The apparatus described in Section 6 and the reag
34、ents listed in Section 7are both supplied by Stanhope-Seta, Chertsey, Surrey KT16 8AP, United Kingdom.To date, no other equipment has demonstrated throughASTM interlaboratory testingthe ability to meet the precision of this test. This is not an endorsement orcertification by ASTM International.D6748
35、 02a (2017)26.3 Dispenser, for Reagent 1 made of polyethylene,polypropylene, or glass and capable of dispensing 5 mL ofreagent with an accuracy of 60.5 mL.6.4 Syringe 1, for test portion, 5 mL, polyethylene,polypropylene, or glass, with an accuracy of 60.25 mL.6.5 Syringe 2, for Reagent 2, preset at
36、 35 L, glass, with anaccuracy of 60.35 L.6.6 Test Tube with Stopper, nominally 15 mL, polyethylene,polypropylene, or glass.6.7 Pipette, 5 mL, polyethylene, polypropylene, or glass.6.8 Test Cuvette, 4.5 mL volume, optical methacrylate,disposable, with two opposite ribbed sides. Dimensions shallbe 45
37、mm high, 12.5 mm by 12.5 mm in width with a testportion pathlength 10 mm 6 0.25 mm.7. Reagents and Materials7.1 Reagent 1, proprietary, methanol solvent containing aLowry-Bronsted acid7(WarningAcidic, flammable, toxic,irritant).7.2 Reagent 2, proprietary solution containing potassiumpermanganate7an
38、oxidizing agent (WarningOxidizingagent, toxic, irritant).7.3 Water, distilled or deionized, for flushing Syringe 2 usedfor Reagent 2.8. Sampling8.1 Field SamplingTake field samples in accordance withPractices D4057, D4177, or other comparable sampling prac-tices. Record the sampling date. Sample bul
39、k fuel above itscloud point and thoroughly mix prior to aliquot sampling. Forshipping field samples, use only epoxy-lined steel cans thathave been cleaned according to Practice D4306.8.2 Store samples at normal room temperature (20 C to25 C) or colder.8.3 Filter samples which contain free water or a
40、 water hazethrough a qualitative filter paper or a loose plug of cotton toremove such water.8.4 Laboratory SubsamplingSample fuel above its cloudpoint and thoroughly mix prior to aliquot sampling. At least5 mL of sample is required for each test. Follow PracticesD4057 and D5854. Use clean amber or c
41、lean borosilicate glasscontainers for laboratory handling. Shield fuel in clear bottlesfrom sunlight to prevent photochemical reactions. Other labo-ratory containers may be used provided they are shown not toaffect the results of the test.8.5 Allow the test sample to reach the local ambienttemperatu
42、re (10 C to 30 C) before commencing the test.9. Preparation and Calibration of Apparatus9.1 For portable use ensure that the battery has beencharged.9.2 Zeroing the SpectrophotometerTurn on the portablespectrophotometer for at least 2 min. Fill a test cuvette withReagent 1, to within 5 mm of its top
43、. Place the filled testcuvette into the spectrophotometer drawer. Zero both wave-lengths individually by separately pressing each select buttonand turning the corresponding zero button until 0.00 AU isdisplayed.9.2.1 Dispose of the cuvette and the aliquot of Reagent 1.Do not reuse the cuvette.NOTE 3
44、The spectrophotometer is correctly calibrated if the twowavelength readings are 0.00 AU 6 0.01 AU.9.3 VerificationA verification fluid is under development.10. Procedure10.1 Pour 5 mL of Reagent 1 into a test tube and add a 5 mLaliquot of the test sample using Syringe 1. Stopper the test tubeand vig
45、orously shake the test tube for 10 s 6 2s.10.2 Remove the stopper and add 35 L of Reagent 2 usingSyringe 2. Stopper the test tube and vigorously shake the testtube for 10 s 6 2 s. Allow to settle for 30 min to 35 min.10.3 Switch on the spectrophotometer at least 2 min beforethe end of the 30 min per
46、iod.10.4 At the end of the 30 min period, use a pipette to drawthe darker reagent layer (at the top) from the test tube and toFIG. 1 SpectrophotometerD6748 02a (2017)3transfer that liquid to the test cuvette. Fill the cuvette to within5 mm of its top. (WarningHold the cuvette using the tworibbed sid
47、es to avoid affecting the optical path.)10.5 Place the cuvette (with the ribbed side towards thedrawer handle) in the spectrophotometer and close the drawer.10.6 Record the results from the digital display every 60 s 65 s until two readings agree within 0.02 AU and report thesecond of these reading
48、as the measured relative absorbance.Record a negative result as zero.11. Report11.1 Report the source, type, and identification of thematerial tested, plus the dates sampled and tested.11.2 Refer to this test method and report any deviation, byagreement or otherwise, from the procedure specified.11.
49、3 Report the result of the test in absorbance units to thenearest 0.01 AU.12. Precision and Bias812.1 The precision of this test method, as determined bystatistical analyses of interlaboratory results, is as follows:12.2 RepeatabilityThe difference between two test resultsobtained by the same operator with the same apparatus underconstant operating conditions, on identical test material would,in the long run, in the normal and correct operation of the testmethod, exceed the following only in one case in twenty.r 5 0.0876 x10.2! AU (3)where:x = averag
