1、Designation: D 6728 01 (Reapproved 2006)An American National StandardStandard Test Method forDetermination of Contaminants in Gas Turbine and DieselEngine Fuel by Rotating Disc Electrode Atomic EmissionSpectrometry1This standard is issued under the fixed designation D 6728; the number immediately fo
2、llowing 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.1. Scope1.1 This test met
3、hod covers the determination of contami-nants and materials as a result of corrosion in gas turbine ordiesel engine fuels by rotating disc electrode atomic emissionspectroscopy (RDE-AES).1.1.1 The test method is applicable to ASTM Grades 0-GT,1-GT, 2-GT, 3-GT, and 4-GT gas turbine fuels and Grades L
4、owSulfur No. 1-D, Low Sulfur No. 2-D, No. 1-D, No. 2-D, andNo. 4-D diesel fuel oils.1.1.2 This test method provides a rapid at-site determinationof contamination and corrosive elements ranging from frac-tions of mg/kg to hundreds of mg/kg in gas turbine and dieselengine fuels so the fuel quality and
5、 level of required treatmentcan be determined.1.1.3 This test method uses oil-soluble metals for calibra-tion and does not purport to quantitatively determine or detectinsoluble particles.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for inf
6、ormationonly. The preferred units are mg/kg (ppm by mass).1.3 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-bil
7、ity of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 975 Specification for Diesel Fuel OilsD 2880 Specification for Gas Turbine Fuel OilsD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 5854 Practice for Mixing and Handling of LiquidSamples o
8、f Petroleum and Petroleum ProductsD 6299 Practice for Applying Statistical Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformance3. Terminology3.1 Definitions:3.1.1 burn, vtin emission spectroscopy, to vaporize andexcite a specimen with sufficient energy to generate spectra
9、lradiation.3.1.2 calibration, nthe determination of the values of thesignificant parameters by comparison with values indicated bya set of reference standards.3.1.3 calibration curve, nthe graphical or mathematicalrepresentation of a relationship between the assigned (known)values of standards and t
10、he measured responses from themeasurement system.3.1.4 calibration standard, na standard having an ac-cepted value (reference value) for use in calibrating a measure-ment instrument or system.3.1.5 detection limit, nthe smallest concentration of anelement that can be measured for specific analysis c
11、onditionsand data collection periods.3.1.6 emission spectroscopy, nmeasurement of energyspectrum emitted by or from an object under some form ofenergetic stimulation; for example, light, electrical discharge,and so forth.3.2 Description of Terms Specific to This Standard:3.2.1 arc discharge, na self
12、-sustaining, high current den-sity, high temperature discharge uniquely characterized by acathode fall nearly equal to the ionization potential of the gasor vapor in which it exists.3.2.2 check sample, na reference material usually pre-pared by a single laboratory for its own use as a measurementcon
13、trol standard, or for the qualification of a measurementmethod.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved May 1, 2006. Published June 2006.
14、 Originallyapproved in 2001. Last previous edition approved in 2001 as D 6728 01.2For 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 Summary page
15、 onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.3 contaminant, nmaterial in a fuel sample that maycause ash deposition or high temperature corrosion.3.2.4 graphite disc electrode, na soft form of the elementca
16、rbon manufactured into the shape of a disc for use as anelectrode in arc/spark spectrometers for oil and fuel analysis.3.2.5 graphite rod electrode, na soft form of the elementcarbon manufactured into the shape of a rod for use as acounter electrode in arc/spark spectrometers for oil and fuelanalysi
17、s.3.2.6 profiling, nto set the actual position of the entranceslit to produce optimum measurement intensity.3.2.7 standardization, nthe process of reestablishing andcorrecting a calibration curve through the analysis of at leasttwo known oil standards.3.2.8 uptake rate, nthe amount of oil or fuel sa
18、mple thatis physically carried by the rotating disc electrode into the arcfor analysis.4. Summary of Test Method4.1 A fuel test specimen is excited by a controlled arcdischarge using the rotating disk technique. The radiant ener-gies of selected analytical lines and a reference are collectedand stor
19、ed by way of photomultiplier tubes, charge coupleddevices, or other suitable detectors. A comparison is made ofthe emitted intensities of the elements in the fuel test specimenagainst those measured with calibration standards. The concen-tration of the elements present in the fuel test specimen arec
20、alculated and displayed.5. Significance and Use5.1 Operating experience of gas turbines and diesel engineshas shown that some of the ash-forming substances present ina fuel can lead to high temperature corrosion, ash deposition,and fuel system fouling. Ash-forming materials may be in afuel as oil-so
21、luble metallo-organic compounds as water-solublesalts or as solid foreign contamination. Their presence andconcentration varies with the geographical source of a crude oiland they are concentrated in the residual fractions during therefining process. Although distillate fuel oils are typicallycontam
22、inant free, ash-forming materials may be introducedlater in the form of salt-bearing water or by contact with otherpetroleum products during transportation and storage. Specifi-cations of gas turbine and diesel engine fuels and the signifi-cance of contamination and trace metals are detailed inSpeci
23、fications D 2880 and D 975.5.1.1 Pre-conditioning of the fuel before it reaches the gasturbine or diesel engine has become a prerequisite for instal-lations that use heavy petroleum fuel, and also for sites that uselight distillate fuel oils. On-site fuel analysis to determine theextent of contamina
24、tion is an integral part of a fuel qualitymanagement program. It is used first to determine the extent ofthe required treatment, and later, the effectiveness of thetreatment. It starts with the delivery of the fuel, continuesthroughout fuel handling and ends only as the fuel is injectedinto the turb
25、ine or engine.5.1.2 Fuel contamination specifications vary among thedifferent gas turbine manufacturers. However, without excep-tion, each requires that contaminants must be as low aspossible. In most power generation installations, it is the ownerwho has the responsibility of verifying fuel cleanli
26、ness incompliance with the turbine manufacturers warranty specifi-cations. This leads to an on-site analytical instrument perfor-mance requirement of below 1.0 mg/kg for several elements.6. Interferences6.1 SpectralMost spectral interferences can be avoided byjudicious choice of spectral lines. High
27、 concentrations of someelements can have an interfering influence on the spectral linesused for determining trace levels of contaminants. Instrumentmanufacturers usually compensate for spectral interferencesduring factory calibration. A background correction system,which subtracts unwanted intensiti
28、es on the side of the spectralline, shall also be used for this purpose. When spectralinterferences cannot be avoided with spectral line selection andbackground correction, the necessary corrections shall be madeusing the computer software supplied by the instrument manu-facturer.6.2 Viscosity Effec
29、tsDifferences in viscosity of fuelsamples will cause differences in uptake rates. Internal refer-ences of the instrument will compensate for a portion of thedifferences. Without a reference, the analysis will be adverselyaffected if the test specimen has a different viscosity from thecalibration sam
30、ples. The hydrogen 486.10 nm spectral lineshall be used for light fuels, and the carbon 387.10 nm spectralline shall be used for heavy fuels as an internal reference tocompensate for viscosity effects.6.3 ParticulateWhen large particles over 10 m in sizeare present, the analytical results will be lo
31、wer than the actualconcentration they represent. Large particles may not beeffectively transported by the rotating disk electrode sampleintroduction system into the arc, nor will they be fullyvaporized.7. Apparatus7.1 Electrode Sharpeneran electrode sharpener to removethe contaminated portion of the
32、 rod electrode remaining fromthe previous determination. It also forms a new 160 angle onthe end of the electrode.7.2 Rotating Disc Electrode Atomic EmissionSpectrometera simultaneous spectrometer consisting of ex-citation source, polychromator optics, and readout system.Suggested wavelengths are li
33、sted in Table 1. When multiplewavelengths are listed, they are in the order of preference ordesired analytical range.7.3 Heated Ultrasonic Bath (Recommended)an ultrasonicbath to heat and homogenize fuel samples to bring particlesinto suspension. The ultrasonic bath shall be used on samplesTABLE 1 El
34、ements and Recommended WavelengthsElement Wavelength, nm Element Wavelength, nmAluminum 308.21 Magnesium 280.20, 518.36Calcium 393.37 Nickel 341.48Chromium 425.43 Potassium 766.49Copper 324.75 Silicon 251.60Iron 259.94 Sodium 588.99Lead 283.31 Vanadium 290.88, 437.92Lithium 670.78 Zinc 213.86Mangane
35、se 403.07D 6728 01 (2006)2containing large amounts of debris, those that have been intransit or in storage for at least 48 h and for heavy residual fuelsto reduce viscosity effects.7.4 Power MixerA power mixer should be used before asample is transferred from one container to another to ensurethat a
36、 homogeneous mixture is created and maintained until thetransfer is complete. Practice D 5854 should be consulted forthe mixing and handling of liquid samples.8. Reagents and Materials8.1 Base Oila 75 cSt (40C) base oil, free of analyte, to beused as a calibration blank or for blending calibration s
37、tan-dards.8.2 Check Sample and Quality Control (QC) Samplesoneor more oil or fuel standards or samples of known concentra-tion which are periodically analyzed as go/no-go samples toconfirm the need for standardization based on an allowableaccuracy limit as described in Appendix X1.8.3 Cleaning Solut
38、ionan environmentally safe, non-chlorinated, rapid evaporating, and non-film producing solventto remove spilled or splashed oil or fuel sample in the samplestand of the spectrometer.8.4 Counter ElectrodeThe counter electrode is a rodelectrode. The counter electrode shall be of high-purity graph-ite
39、(spectroscopic grade). Dimensions of new counter elec-trodes shall conform to those shown in Fig. 1.8.5 Disc Electrodegraphite disc electrode of high-puritygraphite (spectroscopic grade). Dimensions of the electrodesshall conform to those shown in Fig. 2.8.6 Glass Cleaning Solutioncapable of cleanin
40、g and re-moving splashed oil or fuel sample from the quartz windowthat protects the entrance lens and fiber optic. Ammonia basedwindow cleaner or 70 % isopropyl rubbing alcohol have beenfound to be suitable for this purpose.8.7 Organometallic Standardssingle or multi-elementblended standards for use
41、 as the high concentration standardfor instrument standardization purposes or for use as a checksample to confirm calibration. Multi-element blends are usedfor fuel analysis applications that contain a 3:1 concentrationratio of magnesium to all other metals present. The typicalconcentration for the
42、upper calibration point is 10 mg/kg forlight fuels when ASTM No. 0-GT, No. 1-GT, No. 2-GT, Grade1-D, Grade 2-D, and Grade 4-D fuel samples are analyzed. Thetypical concentration for the upper calibration point is 100mg/kg for heavy fuels when No. 3-GT and No. 4-GT fuelsamples are analyzed.8.7.1 Stan
43、dards have a shelf-life and shall not be used tostandardize an instrument if they have exceeded the expirationdate.8.8 Specimen HoldersA variety of specimen holders canbe used for the analysis of fuel samples. Disposable specimenholders must be discarded after each analysis and reusablespecimen hold
44、ers must be cleaned after each analysis. Allspecimen holders must be free of contamination and shall bestored accordingly. Specimen holder covers shall be used onthose fuel samples that may catch on fire during the analysis.9. Sampling9.1 The fuel sample taken for the analysis must be repre-sentativ
45、e of the entire system. Good sampling procedures arekey to good analyses and samples must be taken in accordancewith Practice D 4057.10. Preparation of Test Specimen10.1 HomogenizationFuel samples may contain particu-late matter and free water and, in order to be representative,must always be vigoro
46、usly shaken prior to pouring a testspecimen for analysis.10.2 Ultrasonic HomogenizationSamples that have beenin transit for several days, idle in storage or very viscous, shallbe placed in a heated ultrasonic bath to break up clusters ofparticles and to bring them back into suspension. The samplessh
47、all be vigorously shaken with a power mixer after being inthe ultrasonic bath and prior to pouring a test specimen foranalysis. The bath temperature shall be 60C for very viscousfuels and below the flash point of non viscous fuels. The totalagitation time for a sample should be at least 2 min.10.3 S
48、pecimen HoldersFuel samples and oil standardsshall be poured into a specimen holder of at least 1 mLcapacityprior to analysis. Exercise care to pour the sample consistentlyto the same level in the specimen holders.10.4 Specimen TableThe specimen table shall be adjustedso that when it is in the full
49、raised position, at least one-thirdof the disc electrode diameter is immersed in the oil testspecimen.11. Preparation of Apparatus11.1 Warm-up BurnsIf the instrument has been idle forseveral hours, it may be necessary to conduct warm-up burns tostabilize the excitation source. The warm-up procedure can beperformed with any fuel sample or standard. Consult themanufacturers instructions for specific warm-up requirements.FIG. 1 Graphite Counter ElectrodeD 6728 01 (2006)311.2 Optical ProfilePerform the normal optical profileprocedure called for
