1、Designation: D 6748 02a (Reapproved 2007)An American National StandardStandard 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 d
2、esignation D 6748; the number immediately 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 (e) indicates an editorial change since the last revi
3、sion or reapproval.1. Scope1.1 This 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 D 396,D 975, D 2069, and D 2880. Phenalenes and
4、 phenalenonesaffect the potential instability of fuels, leading to fuel degra-dation products during storage, which may cause performanceproblems.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
5、fuels containing residual oil.The portable 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
6、 of the test method has been established 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
7、to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:4D 396 Specification for Fuel OilsD 975 Specification for Diesel Fuel OilsD 2069 Specification for Marine Fuels5D 2880 Specification
8、 for Gas Turbine Fuel OilsD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD 4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace ContaminationD 4625 Test Method for Middle Distillat
9、e Fuel StorageStability at 43C (110F)D 5854 Practice for Mixing and Handling of LiquidSamples of Petroleum and Petroleum ProductsD 6468 Test Method for High Temperature Stability ofDistillate FuelsE 131 Terminology Relating to Molecular SpectroscopyE 275 Practice for Describing and Measuring Perform
10、anceof Ultraviolet, Visible, and Near-Infrared Spectrophotom-eters2.2 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 and Lu
11、bricants and is the direct responsibility of SubcommitteeD02.14 on Stability and Cleanliness of Liquid Fuels.Current edition approved Nov. 1, 2007. Published January 2008. Originallyapproved in 2002. Last previous edition approved in 2002 as D 674802a.2This test method is being jointly developed wit
12、h 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 ASTM International Headquarters. Your comments will receivecareful
13、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 ASTMStandards volume information, refer to the standards Document Summar
14、y page onthe ASTM website.5Withdrawn.6Available from United Kingdom Defence Standardization, Room 1138, Ken-tigern House, 65 Brown Street, Glasgow, G2 8EX. United Kingdom.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Def Stan 914 F
15、uel, Naval, Distillate NATO Code: F76Joint Service, Designation DIESO F763. Terminology3.1 Definitions:3.1.1 For definitions of terms relating to absorption spec-troscopy see Terminology E 131. Terms of particular signifi-cance are the following:3.1.2 radiant energy, nenergy transmitted as electroma
16、g-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 Standard: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 = trans
17、mittance 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 pathlength 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 wh
18、ich theradiant energy is incident and the surface of the test portionfrom which it emerges.3.2.4 relative absorbance, nthe difference between theabsorbance (near infrared-visible band results) measured at thetwo wavelengths, and reported in AU.3.2.5 transmittance, T, nthe ratio of the radiant powert
19、ransmitted by the test portion in the test cuvette to the radiantpower transmitted by the Reagent 1 control in the cuvette.Expressed in the following 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. Summar
20、y of Test Method4.1 A5 mLvolume of middle distillate fuel is mixed with anequal volume of an immiscible reagent solution. A secondreagent is then added, 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 spect
21、rophotometerand the relative absorbance of near infrared and visible light, atfixed single wavelengths, is measured instantaneously andautomatically, 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
22、 subsequently converted to colored indolylphe-nalene salts by the acidic Reagent 1. The spectrophotometermeasures the absorbance of light caused by the colored saltswhile eliminating the effect of the initial color of the fuel. Theabsorbance of light is a measure of the concentration of thecolored s
23、alts that are formed.5. Significance and Use5.1 Storage stability depends on complex interactions. Itvaries with feedstock type and source, and the processing used.The rate of degradation may not change uniformly withtemperature. Chemical reactions may lead to a change in colorfollowed by the format
24、ion of soluble gums and insolublesediments. Insoluble sediments may overload filters, and plugnozzles and injectors.5.2 This test method, which does 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 with
25、in 35min.5.3 The potential beneficial effects of stability additives infuels may not be recognized by this test method. Therefore, theactual storage stability of middle distillate fuels with stabilityadditives may not be correctly indicated by these test results.5.4 The unstable reactive compounds (
26、phenalenes and phe-nalenones) detected by this test method may be present in fuelscontaining catalytically cracked or straight run materials andcan 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 o
27、f partiesconcerned to decide whether or not this procedure yieldsmeaningful results.5.6 Interpretation of results and correlation with other testmethods is given in Appendix X1.6. Apparatus76.1 Spectrophotometer, double beam, capable of measuringabsorbance at one visible wavelength in the range 600-
28、800 nmand one near infrared wavelength in the range 800-850 nm witha spectral bandwidth of 10 6 2 nm and an accuracy of 63nm(see Fig. 1). The display shall have a resolution of 0.01 of AU,and a repeatability of measurement of 60.02 AU for ranges upto 1.00 AU. See Practice E 275.NOTE 2The two wavelen
29、gths used are proprietary and are notadjustable.6.1.1 Zero Adjustment, a facility shall be incorporated toallow the absorbance measured 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 instant
30、aneous difference between the absorbancemeasured at the two wavelengths. The peak wavelengthrepresents the absorption due to the colored 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.6
31、.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.7The equipment, as listed in RR: D021522 was used to develop the precisionstatement. The apparatus described in Section 6 and the reagents listed in Section 7
32、are 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.D 6748 02a (2007)26.4 Syringe
33、 1, for test portion, 5 mL, polyethylene, polypro-pylene, or glass, with an accuracy of 60.25 mL.6.5 Syringe 2, for Reagent 2, preset at 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, polyprop
34、ylene, or glass.6.8 Test Cuvette, 4.5 mL volume, optical methacrylate,disposable, with two opposite ribbed sides. Dimensions shallbe 45 mm high, 12.5 by 12.5 mm in width with a test portionpathlength 10 6 0.25 mm.7. Reagents and Materials7.1 Reagent 1, proprietary, methanol solvent containing aLowry
35、-Bronsted acid7(WarningAcidic, flammable, toxic,irritant).7.2 Reagent 2, proprietary solution containing potassiumpermanganate7an oxidizing agent (WarningOxidizingagent, toxic, irritant).7.3 Water, distilled or deionized, for flushing Syringe 2 usedfor Reagent 2.8. Sampling8.1 Field SamplingTake fie
36、ld samples in accordance withPractices D 4057, D 4177, or other comparable samplingpractices. Record the sampling date. Sample bulk 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 Pr
37、actice D 4306.8.2 Store samples at normal room temperature (20 to 25C)or colder.8.3 Filter samples which contain free water or a 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 pr
38、ior to aliquot sampling. At least 5mL of sample is required for each test. Follow PracticesD 4057 and D 5854. Use clean amber or clean borosilicateglass containers for laboratory handling. Shield fuel in clearbottles from sunlight to prevent photochemical reactions. Otherlaboratory containers may be
39、 used provided they are shown notto affect the results of the test.8.5 Allow the test sample to reach the local ambienttemperature (10 to 30C) before commencing the test.9. Preparation and Calibration of Apparatus9.1 For portable use ensure that the battery has beencharged.9.2 Zeroing the Spectropho
40、tometerTurn on the portablespectrophotometer for at least 2 min. Fill a test cuvette withReagent 1, to within 5 mm of its top. Place the filled testcuvette into the spectrophotometer drawer. Zero both wave-lengths individually by separately pressing each select buttonand turning the corresponding ze
41、ro 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 3The spectrophotometer is correctly calibrated if the twowavelength readings are 0.00 6 0.01 AU.9.3 VerificationA verification fluid is under development.10. Procedure10.1 Pour
42、 5 mL of Reagent 1 into a test tube and adda5mLaliquot of the test sample using Syringe 1. Stopper the test tubeand vigorously shake the test tube for 10 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 6 2 s. Allow
43、 to settle for 30 to 35 min.10.3 Switch on the spectrophotometer at least 2 min beforethe end of the 30 min period.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 totransfer that liquid to the test cuvette. Fill the cuvette to w
44、ithin5 mm of its top. (WarningHold the cuvette using the tworibbed sides 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 65 s until two
45、readings agree within 0.02 AU and report thesecond of these reading as the measured relative absorbance.Record a negative result as zero.FIG. 1 SpectrophotometerD 6748 02a (2007)311. Report11.1 Report the source, type, and identification of thematerial tested, plus the dates sampled and tested.11.2
46、Refer to this test method and report any deviation, byagreement or otherwise, from the procedure specified.11.3 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 interlaborato
47、ry 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 o
48、nly in one case in twenty.r 5 0.0876 x 1 0.2! AU (3)where:x = average of results being compared.12.3 ReproducibilityThe difference between two singleand independent results obtained by different operators work-ing in different laboratories on identical test material would, inthe long run, in the nor
49、mal correct operation of the test method,exceed the following only in one case in twenty.R 5 0.1799 x 1 0.2! AU (4)where:x = average of results being compared.12.4 BiasSince there is no accepted reference materialsuitable for determining the bias of the procedures in TestMethod D 6748, bias cannot be determined.13. Keywords13.1 absorbance units; burner fuel; diesel fuel; infrared;infrared spectrophotometer; marine fuel; middle distillate fuel;potential instability; spectrometer; spectrophotometer; storagestability; turbine fuel; visible spectrophoto
