1、Designation: D7418 12Standard Practice forSet-Up and Operation of Fourier Transform Infrared (FT-IR)Spectrometers for In-Service Oil Condition Monitoring1This standard is issued under the fixed designation D7418; the number immediately following the designation indicates the year oforiginal adoption
2、 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.INTRODUCTIONThis practice describes the instrument set-up and operation parameters for u
3、sing FT-IR spectrom-eters for in-service oil condition monitoring. The following parameters are typically monitored forpetroleum and hydrocarbon based lubricants: water, soot, oxidation, nitration, phosphate antiwearadditives, fuel dilution (gasoline or diesel), sulfate by-products and ethylene glyc
4、ol. Measurement anddata interpretation parameters are standardized to allow operators of different FT-IR spectrometers toobtain comparable results by employing the same techniques. Two approaches may be used to monitorin-service oil samples by FT-IR spectrometry: (1) direct trend analysis and (2) di
5、fferential (spectralsubtraction) trend analysis. The former involves measurements made directly on in-service oilsamples, whereas the latter involves measurements obtained after the spectrum of a reference oil hasbeen subtracted from the spectrum of the in-service oil being analyzed. Both of these a
6、pproaches aredescribed in this practice, and it is up to the user to determine which approach is more appropriate.1. Scope1.1 This practice covers the instrument set-up and operationparameters for using FT-IR spectrometers for in-service oilcondition monitoring for both direct trend analysis and dif
7、fer-ential trend analysis approaches.1.2 This practice describes how to acquire the FT-IR spec-trum of an in-service oil sample using a standard transmissioncell and establishes maximum allowable spectral noise levels.1.3 Measurement and integrated parameters for individualin-service oil condition m
8、onitoring components and param-eters are not described in this practice and are described in theirrespective test methods.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 This standard does not purport to address all of
9、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-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4057 Practice for Manual
10、 Sampling of Petroleum andPetroleum ProductsE131 Terminology Relating to Molecular SpectroscopyE168 Practices for General Techniques of Infrared Quanti-tative AnalysisE1421 Practice for Describing and Measuring Performanceof Fourier Transform Mid-Infrared (FT-MIR) Spectrom-eters: Level Zero and Leve
11、l One TestsE1866 Guide for Establishing Spectrophotometer Perfor-mance TestsE2412 Practice for Condition Monitoring of In-Service Lu-bricants by Trend Analysis Using Fourier TransformInfrared (FT-IR) Spectrometry3. Terminology3.1 Definitions:3.1.1 For definitions of terms relating to infrared spectr
12、os-copy used in this practice, refer to Terminology E131.3.1.2 Fourier transform infrared (FT-IR) spectrometry,nform of infrared spectrometry in which an interferogram isobtained; this interferogram is then subjected to a Fourier1This practice is under the jurisdiction of ASTM Committee D02 on Petro
13、leumProducts and Lubricants and is the direct responsibility of Subcommittee D02.96 onIn-Service Lubricant Testing and Condition Monitoring Services.Current edition approved Dec. 1, 2012. Published December 2012. Originallyapproved in 2007. last previous edition approved in 2007 as D7418 07. DOI:10.
14、1520/D7418-12.2For 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 onthe ASTM website.Copyright ASTM International, 100 Barr Harbor D
15、rive, PO Box C700, West Conshohocken, PA 19428-2959. United States1transform calculation to obtain an amplitude-wavenumber (orwavelength) spectrum.3.2 Definitions of Terms Specific to This Standard:3.2.1 condition monitoring, n field of technical activity inwhich selected physical parameters associa
16、ted with an operat-ing machine are periodically or continuously sensed, measuredand recorded for the interim purpose of reducing, analyzing,comparing and displaying the data and information so obtainedand for the ultimate purpose of using interim result to supportdecisions related to the operation a
17、nd maintenance of themachine. (1, 2)33.2.2 direct trend analysis, nmonitoring of the level andrate of change over operating time of measured parameters (2,3) using the FT-IR spectrum of the in-service oil sample,directly, without any spectral data manipulation such as spec-tral subtraction.3.2.3 dif
18、ferential trend analysis, nmonitoring of the leveland rate of change over operating time of measured parametersusing the FT-IR spectra of the in-service oil samples, followingsubtraction of the spectrum of the reference oil.3.2.4 in-service oil, nlubricating oil that is present in amachine that has
19、been at operating temperature for at least onehour.3.2.4.1 DiscussionSampling an in-service oil after a shortperiod of operation will allow for the measurement of a basepoint for trend analysis; the minimum sampling time should beat least one hour after oil change or topping-off.3.2.5 reference oil,
20、 nsample of a lubricating oil whosespectrum is subtracted from the spectrum of an in-service oilfor differential trend analysis.3.2.5.1 DiscussionThe most commonly employed refer-ence oil is a sample of the new oil. It should be noted, however,that the continued use of the same reference oil after a
21、nytop-off of lubricant may lead to erroneous conclusions, unlessthe added lubricant is from the same lot and drum as thein-service oil. This possibility is averted if a sample of thein-service oil is taken after a short period of operationfollowing top-off of the lubricant (see 3.2.4.1) and is emplo
22、yedthereafter as the reference oil.4. Significance and Use4.1 This practice describes to the end user how to collect theFT-IR spectra of in-service oil samples for in-service oilcondition monitoring. Various in-service oil condition moni-toring parameters, such as oxidation, nitration, soot, water,e
23、thylene glycol, fuel dilution, gasoline dilution, sulfate by-products and phosphate antiwear additives, can be measured byFT-IR spectroscopy (5-8), as described in Practice E2412.Changes in the values of these parameters over operating timecan then be used to help diagnose the operational condition
24、ofvarious machinery and equipment and to indicate when an oilchange should take place. This practice is intended to give astandardized configuration for FT-IR instrumentation and op-erating parameters employed in in-service oil condition moni-toring in order to obtain comparable between-instrument a
25、ndbetween-laboratory data.5. Apparatus5.1 Fourier Transform Infrared (FT-IR) SpectrometerAllFT-IR instruments suitable for use in this practice must beconfigured with a source, beamsplitter and detector suitable forspectral acquisition over the mid-infrared range of 4000 to 550cm-1. The standard con
26、figuration includes a room temperaturedeuterated triglycine sulfate (DTGS) detector, an air-cooledsource, and a germanium-coated potassium bromide (Ge/KBr)beamsplitter, although a zinc selenide (ZnSe) beamsplitter mayalso be used. The FT-IR spectrometers IR source and inter-ferometer should be in a
27、sealed compartment to preventharmful, flammable or explosive vapors from reaching the IRsource.NOTE 1Photoconductive detectors such as mercury cadmium telluride(MCT) should not be used owing to inadequate linearity of the detectorresponse.5.2 Sample CellThe sample cell employed for in-serviceoil con
28、dition monitoring is a transmission cell with a fixedpathlength that can be inserted in the optical path of the FT-IRspectrometer. Cell window material and cell pathlength con-siderations are stated below.5.2.1 Cell Window MaterialZnSe is commonly used asthe window material for condition monitoring
29、and is recom-mended because of its resistance to water. Sample cellsconstructed of materials other than ZnSe may be used;however, to address all the various methods associated withcondition monitoring, the window material should transmit IRradiation over the range of 4000 cm-1to 550 cm-1. KCl andKBr
30、 are common cell window materials that meet this require-ment but these are water-soluble salts and should not be usedif oil samples containing moisture are frequently run throughthe cell, as contact with water will cause the windows to fogand erode rapidly. In addition, Coates and Setti (4) have no
31、tedthat oil nitration products can react with KCl and KBrwindows, depositing compounds that are observed in thespectra of later samples. On the basis of this report, KCl andKBr windows should not be used with samples of gasoline ornatural gas engine oils as well as other types of lubricantswhere nit
32、ration by-products may form due to the combustionprocess or other routes of nitration formation.5.2.1.1 When ZnSe is used as the window material, thereflections of the infrared beam that occur at the inner faces ofthe windows cause fringes to be superimposed on the oilspectrum; these must be minimiz
33、ed using physical or compu-tational techniques as presented in Appendix X1. Because KCland KBr have lower refractive indices than ZnSe, the use ofthese window materials avoids observable fringes in the oilspectrum.5.2.2 Cell PathlengthThe standard cell pathlength to beemployed for in-service oil con
34、dition monitoring is 0.100 mm;however, in practical terms, pathlengths ranging from 0.080 upto 0.120 mm are suitable, with values outside this range leadingto either poor sensitivity or non-linearity of detector response,respectively. The actual cell pathlength obtained can be deter-mined from the i
35、nterference fringes in the spectrum recorded3The boldface numbers in parentheses refer to a list of references at the end ofthis standard.D7418 122with an empty cell or by recording the spectrum of a checkfluid; details for calculating cell pathlength are presented inAppendix X2. The reporting units
36、 of the various in-service oilcondition monitoring parameter test methods are based on apathlength of 0.100 mm (see the respective test methods).Accordingly, all data must be normalized to a pathlength of0.100 mm, either by multiplying all data points in the absorp-tion spectra by a pathlength corre
37、ction factor (spectral normal-ization) or by multiplying the results of the respective testmethods by a pathlength correction factor (see 10.2). Thenormalization procedure is usually part of the software pro-vided by instrument manufacturers.5.2.2.1 DiscussionHowever, if sample dilution is em-ployed
38、 (see Appendix X3), longer pathlengths may becomesuitable. For example, for dilution with odorless mineral spirits(OMS) in a 2:1 OMS:oil sample ratio, a pathlength of 0.200mm has proven suitable.NOTE 2For purposes of interlaboratory comparison of results, spectralnormalization should be performed.5.
39、3 Filter (optional)The use of a particulate filter with amesh size of 0.100 mm or less to trap any large particlespresent in the sample is strongly recommended to prevent cellclogging.5.4 Sample Pumping System (optional)A pumping systemcapable of transporting oil to be analyzed into the transmission
40、cell and of emptying and flushing the cell with solvent betweensamples may be used instead of manual cell loading. Commer-cial vendors offer various pumping systems that may differ inthe type of pump, tubing, and transmission cell. Depending onthe sample handling system employed and the viscosity of
41、 theoils analyzed, a wash/rinsing solvent may be run betweensamples to minimize sample-to-sample carryover as well askeep the cell and inlet tubing clean; commercial vendors mayrecommend specific solvent rinse protocols.5.4.1 Hydrocarbon Leak AlarmWhen a sample pumpingsystem is used, an independent
42、flammable vapor sensor andalarm system is strongly recommended The purpose of thisalarm system is to alert the operator when a leak occurs in thetubing, connectors or transmission cell.6. FT-IR Spectral Acquisition Parameters6.1 The spectral acquisition parameters are specified below.Because the spe
43、ctral resolution, data spacing, and apodizationaffect the FT-IR spectral band shapes, these specifications mustbe adhered to:Spectral resolution: 4 cm-1Data spacing: 2 cm-1Apodization: TriangularScanning range: 4000 to 550 cm-1Spectral format: Absorbance as a function of wavenumber6.2 The number of
44、scans co-added and hence the scan timewill depend on the desired spectral noise level (see Section 12),whereby an increase in scan time by a factor of N will decreasethe level of noise by a factor of N1/2.7. Sampling7.1 Sample AcquisitionThe objective of sampling is toobtain a test specimen that is
45、representative of the entirequantity. Thus, laboratory samples should be taken in accor-dance with the instructions in Practice D4057.7.2 Sample PreparationFiltering the sample using a filterdescribed in 5.3 prior to loading the cell with the sample ishighly recommended. An exception to this recomme
46、ndationmay be made when oil samples are diluted (see Appendix X3).8. Preparation and Maintenance of Apparatus8.1 Rinsing, Washing and Check SolventsA variety ofhydrophobic solvents may be used to clean the cell and rinsethe lines between samples as well as serving as a check fluid tomonitor pathleng
47、th. Typical solvents include hexanes,cyclohexane, heptane or odorless mineral spirits (OMS).Health and safety issues on using, storing, and disposing ofcheck or cleaning/wash solvents will not be covered here.Local regulations and Material Safety Data Sheets (MSDS)should be consulted.8.2 Sample Cell
48、 and Inlet FilterThe cell should be flushedwith the designated rinse/wash solvent at the start and end ofanalytical runs to clean the cell. Immediately following flush-ing of the cell, an absorption spectrum of the empty cell (see9.1.2.2) should be recorded to check for build-up of material onthe ce
49、ll windows. If an inlet filter is used, the filter shall also bechecked for particle build-up and its effect on sample flow rate.8.3 Check Fluid and Pathlength MonitoringThe purposeof a check fluid is to verify proper operation of the FT-IRspectrometer/transmission cell combination, as well as anyassociated sample introduction and cleaning hardware. It isrecommended that an absorption spectrum of the check fluid berecorded when a new or re-assembled cell is initially used andarchived to disk as a reference spectrum against which subse-quent spectra of the che
