1、Designation: D6728 11D6728 16Standard Test Method forDetermination of Contaminants in Gas Turbine and DieselEngine Fuel by Rotating Disc Electrode Atomic EmissionSpectrometry1This standard is issued under the fixed designation D6728; the number immediately following the designation indicates the yea
2、r 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. Scope*1.1 This test method covers the determination of contamina
3、nts and materials as a result of corrosion in gas turbine or dieselengine fuels by rotating disc electrode atomic emission spectroscopy (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 LowSulfur No. 1-D, Low Sulfur No. 2-D, No
4、. 1-D, No. 2-D, and No. 4-D diesel fuel oils.1.1.1.1 Trace metal limits of fuel entering turbine combustor(s) are given as 0.5 mgkg each for vanadium, sodium + potassium,calcium, and lead in Specification D2880 for all GT grades.1.1.2 This test method provides a rapid at-site determination of contam
5、ination and corrosive elements ranging from fractionsof mg/kg to hundreds of mg/kg in gas turbine and diesel engine fuels so the fuel quality and level of required treatment can bedetermined.1.1.3 This test method uses oil-soluble metals for calibration and does not purport to quantitatively determi
6、ne or detect insolubleparticles.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.The preferred units are mg/kg (ppm by mass).1.3 This standard does not purport to address all of the safety concerns, if any, associated with
7、its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D975 Specification for Diesel Fuel OilsD2880 Specification for Gas Turbi
8、ne Fuel OilsD4057 Practice for Manual Sampling of Petroleum and Petroleum ProductsD4177 Practice for Automatic Sampling of Petroleum and Petroleum ProductsD5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum ProductsD6299 Practice for Applying Statistical Quality Assur
9、ance and Control Charting Techniques to Evaluate Analytical Measure-ment System Performance3. Terminology3.1 Definitions:3.1.1 burn, vtin emission spectroscopy, to vaporize and excite a specimen with sufficient energy to generate spectral radiation.3.1.2 calibration, nthe determination of the values
10、 of the significant parameters by comparison with values indicated by a setof reference standards.1 This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current
11、 edition approved Oct. 1, 2011June 1, 2016. Published November 2011June 2016. Originally approved in 2001. Last previous edition approved in 20062011 asD672801(2006).D6728 11. DOI: 10.1520/D6728-11.10.1520/D6728-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM C
12、ustomer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to
13、 the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summa
14、ry of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.3 calibration curve, nthe graphical or mathematical representation of a relationship between the assigned (known) valuesof st
15、andards and the measured responses from the measurement system.3.1.4 calibration standard, na standard having an accepted value (reference value) for use in calibrating a measurementinstrument or system.3.1.5 detection limit, nthe smallest concentration of an element that can be measured for specifi
16、c analysis conditions and datacollection periods.3.1.6 emission spectroscopy, nmeasurement of energy spectrum emitted by or from an object under some form of energeticstimulation; for example, light, electrical discharge, and so forth.3.2 Definitions of Terms Specific to This Standard:3.2.1 arc disc
17、harge, na self-sustaining, high current density, high temperature discharge uniquely characterized by a cathodefall nearly equal to the ionization potential of the gas or vapor in which it exists.3.2.2 check sample, na reference material usually prepared by a single laboratory for its own use as a m
18、easurement controlstandard, or for the qualification of a measurement method.3.2.3 contaminant, nmaterial in a fuel sample that may cause ash deposition or high temperature corrosion.3.2.4 graphite disc electrode, na soft form of the element carbon manufactured into the shape of a disc for use as an
19、 electrodein arc/spark spectrometers for oil and fuel analysis.3.2.5 graphite rod electrode, na soft form of the element carbon manufactured into the shape of a rod for use as a counterelectrode in arc/spark spectrometers for oil and fuel analysis.3.2.6 profiling, nto set the actual position of the
20、entrance slit to produce optimum measurement intensity.3.2.7 standardization, nthe process of reestablishing and correcting a calibration curve through the analysis of at least twoknown oil standards.3.2.8 uptake rate, nthe amount of oil or fuel sample that is physically carried by the rotating disc
21、 electrode into the arc foranalysis.4. Summary of Test Method4.1 A fuel test specimen is excited by a controlled arc discharge using the rotating disk technique. The radiant energies ofselected analytical lines and a reference are collected and stored by way of photomultiplier tubes, charge coupled
22、devices, or othersuitable detectors.Acomparison is made of the emitted intensities of the elements in the fuel test specimen against those measuredwith calibration standards. The concentration of the elements present in the fuel test specimen are calculated and displayed.5. Significance and Use5.1 O
23、perating experience of gas turbines and diesel engines has shown that some of the ash-forming substances present in a fuelcan lead to high temperature corrosion, ash deposition, and fuel system fouling. Ash-forming materials may be in a fuel asoil-soluble metallo-organic compounds as water-soluble s
24、alts or as solid foreign contamination. Their presence and concentrationvaries with the geographical source of a crude oil and they are concentrated in the residual fractions during the refining process.Although distillate fuel oils are typically contaminant free, ash-forming materials may be introd
25、uced later in the form ofsalt-bearing water or by contact with other petroleum products during transportation and storage. Specifications of gas turbine anddiesel engine fuels and the significance of contamination and trace metals are detailed in Specifications D2880 and D975.5.1.1 Pre-conditioning
26、of the fuel before it reaches the gas turbine or diesel engine has become a prerequisite for installationsthat use heavy petroleum fuel, and also for sites that use light distillate fuel oils. On-site fuel analysis to determine the extent ofcontamination is an integral part of a fuel quality managem
27、ent program. It is used first to determine the extent of the requiredtreatment, and later, the effectiveness of the treatment. It starts with the delivery of the fuel, continues throughout fuel handlingand ends only as the fuel is injected into the turbine or engine.5.1.2 Fuel contamination specific
28、ations vary among the different gas turbine manufacturers. However, without exception, eachrequires that contaminants must be as low as possible. In most power generation installations, it is the owner who has theresponsibility of verifying fuel cleanliness in compliance with the turbine manufacture
29、rs warranty specifications. This leads to anon-site analytical instrument performance requirement of below 1.01.0 mg mg/kg kg for several elements.6. Interferences6.1 SpectralMost spectral interferences can be avoided by judicious choice of spectral lines. High concentrations of someelements can hav
30、e an interfering influence on the spectral lines used for determining trace levels of contaminants. Instrumentmanufacturers usually compensate for spectral interferences during factory calibration. A background correction system, whichsubtracts unwanted intensities on the side of the spectral line,
31、shall also be used for this purpose. When spectral interferencescannot be avoided with spectral line selection and background correction, the necessary corrections shall be made using thecomputer software supplied by the instrument manufacturer.D6728 1626.2 Viscosity EffectsDifferences in viscosity
32、of fuel samples will cause differences in uptake rates. Internal references of theinstrument will compensate for a portion of the differences. Without a reference, the analysis will be adversely affected if the testspecimen has a different viscosity from the calibration samples. The hydrogen 486.10
33、nm 486.10 nm spectral line shall be usedfor light fuels, and the CN 387.10 CN 387.10 nm spectral line shall be used for heavy fuels as an internal reference to compensatefor viscosity effects.6.3 ParticulateWhen large particles over 10 m in size are present, the analytical results will be lower than
34、 the actualconcentration they represent. Large particles may not be effectively transported by the rotating disk electrode sample introductionsystem into the arc, nor will they be fully vaporized.7. Apparatus7.1 Electrode SharpenerAn electrode sharpener to remove the contaminated portion of the rod
35、electrode remaining from theprevious determination. It also forms a new 160 angle on the end of the electrode.7.2 Rotating Disc Electrode Atomic Emission SpectrometerA simultaneous spectrometer consisting of excitation source,polychromator optics, and readout system. Suggested wavelengths are listed
36、 in Table 1. When multiple wavelengths are listed, theyare in the order of preference or desired analytical range.7.3 Heated Ultrasonic Bath (Recommended)An ultrasonic bath to heat and homogenize fuel samples to bring particles intosuspension. The ultrasonic bath shall be used on samples containing
37、large amounts of debris, those that have been in transit or instorage for at least 48 h 48 h and for heavy residual fuels to reduce viscosity effects.7.4 Power MixerA power mixer should be used before a sample is transferred from one container to another to ensure thata homogeneous mixture is create
38、d and maintained until the transfer is complete. Practice D5854 should be consulted for the mixingand handling of liquid samples.8. Reagents and Materials8.1 Base OilA 75 cSt (40C) 75 cSt (40 C) base oil, free of analyte, to be used as a calibration blank or for blendingcalibration standards.8.2 Che
39、ck Sample and Quality Control (QC) SamplesOne or more oil or fuel standards or samples of known concentrationwhich are periodically analyzed as go/no-go samples to confirm the need for standardization based on an allowable accuracy limitas described in Appendix X1.8.3 Cleaning SolutionAn environment
40、ally safe, non-chlorinated, rapid evaporating, and non-film producing solvent to removespilled or splashed oil or fuel sample in the sample stand of the spectrometer.8.4 Counter ElectrodeThe counter electrode is a rod electrode. The counter electrode shall be of high-purity graphite(spectroscopic gr
41、ade). Dimensions of new counter electrodes shall conform to those shown in Fig. 1.8.5 Disc ElectrodeGraphite disc electrode of high-purity graphite (spectroscopic grade). Dimensions of the electrodes shallconform to those shown in Fig. 2.8.6 Glass Cleaning SolutionCapable of cleaning and removing sp
42、lashed oil or fuel sample from the quartz window thatprotects the entrance lens and fiber optic. Ammonia based window cleaner or 70 % isopropyl rubbing alcohol have been found tobe suitable for this purpose.8.7 Organometallic StandardsSingle or multi-element blended standards for use as the high con
43、centration standard forinstrument standardization purposes or for use as a check sample to confirm calibration. Multi-element blends are used for fuelanalysis applications that contain a 3:1 concentration ratio of magnesium to all other metals present. The typical concentration forthe upper calibrat
44、ion point is 1010 mg mg/kg kg for light fuels when ASTM No. 0-GT, No. 1-GT, No. 2-GT, Grade 1-D, Grade2-D, and Grade 4-D fuel samples are analyzed. The typical concentration for the upper calibration point is 100100 mg mg/kg kgfor heavy fuels when No. 3-GT and No. 4-GT fuel samples are analyzed.8.7.
45、1 Standards have a shelf-life and shall not be used to standardize an instrument if they have exceeded the expiration date.TABLE 1 Elements and Recommended WavelengthsElement Wavelength,nmElement Wavelength, nmAluminum 308.21 Magnesium 280.20, 518.36Calcium 393.37 Nickel 341.48Chromium 425.43 Potass
46、ium 766.49Copper 324.75 Silicon 251.60Iron 259.94 Sodium 588.99Lead 283.31 Vanadium 290.88, 437.92Lithium 670.78 Zinc 213.86Manganese 403.07D6728 1638.8 Specimen HoldersAvariety of specimen holders can be used for the analysis of fuel samples. Disposable specimen holdersmust be discarded after each
47、analysis and reusable specimen holders must be cleaned after each analysis. All specimen holdersmust be free of contamination and shall be stored accordingly. Specimen holder covers shall be used on those fuel samples thatmay catch on fire during the analysis.9. Sampling9.1 The fuel sample taken for
48、 the analysis must be representative of the entire system. Good sampling procedures are key togood analyses and samples must be taken in accordance with PracticePractices D4057 or D4177.10. Preparation of Test Specimen10.1 HomogenizationFuel samples may contain particulate matter and free water and,
49、 in order to be representative, mustalways be vigorously shaken prior to pouring a test specimen for analysis.10.2 Ultrasonic HomogenizationSamples that have been in transit for several days, idle in storage or very viscous, shall beplaced in a heated ultrasonic bath to break up clusters of particles and to bring them back into suspension. The samples shall bevigorously shaken with a power mixer after being in the ultrasonic bath and prior to pouring a test specimen for analysis. The bathtemperature shall be 60C60 C for very viscous fue
