1、Designation: D 6748 02aAn 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 designation D 6748;
2、 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 revision or reapproval
3、.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 phenalenonesaffec
4、t 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 fuels containing r
5、esidual 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 of the test metho
6、d 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 to establish appro
7、-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 396 Specification for Fuel Oils4D 975 Specification for Diesel Fuel Oil4D 2069 Specification for Marine Fuels4D 2880 Specification for Gas Turbine F
8、uel Oils5D 4057 Practice for Manual Sampling of Petroleum andPetroleum Products5D 4177 Practice for Automatic Sampling of Petroleum andPetroleum Products5D 4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace Contamination5D 4625 Test Method for Distillate Fuel Storage Stabil
9、ity at43C (110F)5D 5854 Practice for Mixing and Handling of LiquidSamples of Petroleum and Petroleum Products6D 6468 Test Method for High Temperature Stability ofDistillate Fuels7E 131 Terminology Relating to Molecular Spectroscopy8E 275 Practice for Describing and Measuring Performanceof Ultraviole
10、t, Visible and Near-Infrared Spectrophotom-eters82.2 Other Standards:9Def Stan 05-50 Methods for Testing Fuels and Lubricantsand Associated Products, Part 40 Storage Stability ofDiesel FuelsDef Stan 914 Fuel, Naval, Distillate NATO Code: F76Joint Service, Designation DIESO F761This test method is un
11、der the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.14 on Stability and Cleanliness of Liquid Fuels.Current edition approved Dec. 10, 2002. Published February 2003. Originallyapproved in 2002. Last previous edition approv
12、ed in 2002 as D 6748 - 02.2This 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 i
13、tem to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee, whichyou may attend.4Annual Book of ASTM Standards, Vol 05.01.5Annual Book of ASTM Standards, Vol 05.02.6Annual Book of ASTM Standards, Vol 05.03.7Annual Book
14、of ASTM Standards, Vol 05.04.8Annual Book of ASTM Standards, Vol 03.06.9Available 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-
15、2959, United States.3. 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 electromag-netic waves.3.1.3 radiant power P, nthe rate at whi
16、ch 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 = transmittance as defined in 3.2.5.3.2.2 absorbance units (
17、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 which theradiant energy is incident and the surface of
18、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 powertransmitted by the test portion in the test cuvette to
19、 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. Summary of Test Method4.1 A5 mLvolume of middle distillate
20、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 spectrophotometerand the relative absorbance of near infra
21、red 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 subsequently converted to colored indolylphe-nalene
22、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 salts that are formed.5. Significance and Use5.1 Stora
23、ge 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 formation of soluble gums and insolublesediments. Insoluble
24、 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 within 35mins.5.3 The potential beneficial effects of sta
25、bility 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 (phenalenes and phe-nalenones) detected by this test
26、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 of partiesconcerned to decide whether or not this pro
27、cedure yieldsmeaningful results.5.6 Interpretation of results and correlation with other testmethods is given in Appendix X1.FIG. 1 SpectrophotometerD 6748 02a26. Apparatus106.1 Spectrophotometer, double beam, capable of measuringabsorbance at one visible wavelength in the range 600-800 nmand one ne
28、ar infrared wavelength in the range 800-850 nm witha spectral bandwidth of 10 nm 6 2 nm and an accuracy of 63 nm (see Fig. 1). The display shall have a resolution of 0.01of AU, and a repeatability of measurement of 6 0.02 AU forranges up to 1.00 AU. See Practice E 275.NOTE 2The two wavelengths used
29、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 instantaneous dif
30、ference 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 mins to an accuracy of60.2 mins.6.3 Dispe
31、nser, 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, polypro-pylene, or glass, with an accuracy of 6 0.25 mL.6.5 Syringe 2, for Reagent 2, preset at 35 L, glass, with
32、 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 mm high, 12.5 mm b
33、y 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 acid10(WarningAcidic, flammable, toxic,irritant).7.2 Reagent 2, proprietary solution containing potassiumpermanganate10an oxidizing agent
34、(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 D 4057, D 4177, or other comparable samplingpractices. Record the sampling date. Sample bulk fuel above its
35、cloud point and thoroughly mix prior to aliquot sampling. Forshipping field samples, use only epoxy-lined steel cans thathave been cleaned according to Practice 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
36、 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 least 5mL of sample is required for each test. Follow PracticesD 4057 and D 5854. Use clean amber or clean borosilicat
37、eglass containers for laboratory handling. Shield fuel in clearbottles from sunlight to prevent photochemical reactions. Otherlaboratory containers may be 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) bef
38、ore 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 mins. Fill a test cuvette withReagent 1, to within 5 mm of its top. Place the filled t
39、estcuvette 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 3The spectrophotomete
40、r 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 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 tub
41、e 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 to 35 mins.10.3 Switch on the spectrophotometer at least 2 mins beforethe end of the 30 min period.10.4 At the end of the 3
42、0 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 within5 mm of its top. (WarningHold the cuvette using the tworibbed sides to avoid affecting the optical path.)10.5 Place the cuvette (with
43、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 as the measured relative absorbance.Record a negative result as zero.
44、11. Report11.1 Report the source, type, and identification of thematerial tested, plus the dates sampled and tested.10The equipment, as listed in RR: D021522 was used to develop the precisionstatement. The apparatus described in Section 6 and the reagents listed in Section 7are both supplied by Stan
45、hope-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 02a311.2 Refer to this test method and report a
46、ny 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 Bias1112.1 The precision of this test method, as determined bystatistical analyses of interlaboratory results, is as follows:12.2 Repeat
47、abilityThe 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
48、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 normal correct operation of the test met
49、hod,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 spectrophotometerAPPENDIX(Nonmandatory Information)X
