ASTM D7889-21

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 the previous version. Because
it 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 version
of the standard as published by ASTM is to be considered the official document.
Designation: D7889 − 13 D7889 − 21
Standard Test Method for
Field Determination of In-Service Fluid Properties Using IR
Spectroscopy
This standard is issued under the fixed designation D7889; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 This test method describes the use of a grating spectrometer to analyze properties of an in-service fluid sample which are
indicative of the status of that fluid and related machinery.
1.2 This test method provides a means for the assessment of in-service fluid properties using infrared spectroscopy. It describes
a methodology for sampling, performing analysis, and providing key in-service fluid properties with a self-contained unit that is
meant for field use. It provides analysis of in-service fluids at any stage of their useful life, including newly utilized fluid.
1.3 In particular, these key in-service fluid properties include oxidation, nitration, sulfation, soot, and antiwear additives. They are
applicable for hydrocarbon type (API Group I-IV) fluids from machinery lubricants, including reciprocating engine oils, turbine
oils, hydraulic oils, and gear oils.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
-1
1.4.1 Exception—The unit for wavenumbers is in cm .
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D7412 Test Method for Condition Monitoring of Phosphate Antiwear Additives in In-Service Petroleum and Hydrocarbon Based
Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
D7414 Test Method for Condition Monitoring of Oxidation in In-Service Petroleum and Hydrocarbon Based Lubricants by
Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.96.03 on FTIR Testing Practices and Techniques Related to In-Service Lubricants.
Current edition approved Oct. 1, 2013July 1, 2021. Published October 2013August 2021. Originally approved in 2013. Last previous edition approved in 2013 as
D7889 – 13. DOI: 10.1520/D7889-13.10.1520/D7889-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7889 − 21
D7415 Test Method for Condition Monitoring of Sulfate By-Products in In-Service Petroleum and Hydrocarbon Based
Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
D7418 Practice for Set-Up and Operation of Fourier Transform Infrared (FT-IR) Spectrometers for In-Service Oil Condition
Monitoring
D7624 Test Method for Condition Monitoring of Nitration in In-Service Petroleum and Hydrocarbon-Based Lubricants by Trend
Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
D7669 Guide for Practical Lubricant Condition Data Trend Analysis
D7720 Guide for Statistically Evaluating Measurand Alarm Limits when Using Oil Analysis to Monitor Equipment and Oil for
Fitness and Contamination
D7844 Test Method for Condition Monitoring of Soot in In-Service Lubricants by Trend Analysis using Fourier Transform
Infrared (FT-IR) Spectrometry
E131 Terminology Relating to Molecular Spectroscopy
E168 Practices for General Techniques of Infrared Quantitative Analysis
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E932 Practice for Describing and Measuring Performance of Dispersive Infrared Spectrometers
E1655 Practices for Infrared Multivariate Quantitative Analysis
E2412 Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR)
Spectrometry
E2617 Practice for Validation of Empirically Derived Multivariate Calibrations
3. Terminology
3.1 For definitions of terms relating to infrared spectroscopy used in this test method, refer to Terminology E131. For definition
of terms related to infrared-based in-service fluid condition monitoring, refer to Practice D7418.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 absorbance units (AU), n—units of measurement of the raw absorbance spectrum which is obtained using the definition
described in Section 8 (Theory for a Single Compound Analysis) of Practice E168, which is not normalized for pathlength.
3.2.2 cell background, n—a single-beam spectrum that is obtained on a clean, empty wipe-clean transmission cell.
3.2.3 mid-infrared grating spectrometer, n—a spectrometer which operates in the mid-infrared spectral range, between at least
-1 -1
960 cm and 3040 cm and creates an infrared spectrum by means of a reflective diffraction grating.
3.2.3.1 Discussion—
Such a grating spectrometer may be of any of a variety of designs and optical configurations. Example designs include
monochrometer-type systems wherein the grating is rotated to a single point infrared detector, or array-type systems which utilize
an infrared detector array at the output and a fixed grating. Example optical configurations include Rowland-Circle and
Czerny-Turner systems. Typical infrared detectors are uncooled thermal detectors such as thermopile or pyroelectric-based sensors.
3.2.4 reporting units, n—specifies the reporting units of the fluid analysis property.
3.2.5 self-contained field apparatus, n—a mid-infrared grating spectrometer which is of the form factor to allow it to operate as
an independent device suitable for field use.
3.2.6 wipe-clean transmission cell, n—an infrared transmission cell which is specifically tailored for field use.
3.2.6.1 Discussion—
In particular, the cell may be utilized and cleaned with a towel or rag and without the use of reagents or chemicals of any sort,
making it convenient for use as a field device. Such transmission cells may accomplish this using mechanisms for quick open/close
of the cell such as by means of a mechanical lever, demountable screw or press fit, or magnetic coupling. To correct for any cell
fringing effects, the cell utilizes a wedged design both on the interior faces and exterior faces of the cell windows: The cell
windows themselves are wedged at an angle of less than 0.5 degrees. The spacing between the two windows is wedged at an angle
of approximately 0.013 degrees. The cell is designed to be nominally 100 μm in pathlength, with ZnSe windows.
D7889 − 21
4. Summary of Test Method
4.1 This test method utilizes a self-contained field apparatus to provide detailed information concerning the condition status of
in-service fluids. In particular, it provides readings of oxidation, antiwear additive, sulfation, nitration and soot levels in
hydrocarbon type (API Group I-IV) fluids.
4.1.1 An absorbance spectrum of the sample under test is obtained. For the background spectrum, the cell background is used.
4.1.1.1 Test Methods have been developed for Fourier-transform infrared (FTIR) devices using absorbance spectra obtained using
Practice D7418. Particular Test Methods developed for in-service monitoring of hydrocarbon type (API Group I-IV) fluids include
those established for Oxidation (Test Method D7414, Procedure A), Antiwear Additive (Test Method D7412, Procedure A),
Sulfation (Test Method D7415, Procedure A), Nitration (Test Method D7624, Procedure A), and Soot (Test Method D7844,
Procedure A). These test methods have served to establish the signature infrared spectroscopic behavior associated with key
in-service monitoring properties. This test method provides property values based on the examination of each property’s signature
infrared spectroscopic behavior. The essence of this test method is to capture the underlying chemical trends associated with each
property for in-service fluid analysis using a self-contained field apparatus and coupled wipe-clean transmission cell.
4.1.2 From the infrared absorbance spectrum obtained with the self-contained field apparatus, properties of the in-service fluid are
calculated. In particular, those properties in Table 1 are calculated by the device and presented to the user on the display. Additional
properties using infrared calibration methods may be calculated and displayed depending on the particular fluid being analyzed and
availability of calibrations for that fluid.
4.1.2.1 Infrared spectra generated by the described instrument type can be used to provide a further set of properties of interest
to in-service fluid analysis of hydrocarbon type (API Group I-IV) fluids. Such properties must be calibrated to the particular fluid
blend, and may be generated using ASTM guidelines which govern the creation of such calibrations. Such calibrations may be built
from either standard regression methods as described in Practice E168 or as described in Practice E2412. Further, they may also
be multivariate calibrations, described in Practice E1655 and Practice E2617. Example properties include Acid Number (AN), Base
Number (BN), water contamination, ethylene glycol, fluid mixture content, and antioxidant depletion. It should be noted that, due
to the fact that these calibrations are sample-specific, this test method does not provide a prescription for calculating such
properties.
4.2 The results of the test method can be compared against pre-defined or user-defined limits so as to judge the condition of the
in-service lubricant. Warning and alarm limits exceedences which may be pre-defined or set by the user are indicated by the
property and associated value being highlighted using coding established in Guide D7720, with either green (favorable alarm level
designation showing acceptable condition), yellow (intermediate level alarm designation warning a fault condition is present and
will likely need attention in the future), or red (high level alarm designation showing significant deterioration) indicated by the
self-contained field apparatus.
5. Significance and Use
5.1 This test method provides a means for obtaining useful in-service fluid analysis properties in the field. It is not to be confused
with laboratory or portable FTIR devices which provide measurements per the existing Test Methods listed in 4.1.1.1. Each of these
monitored properties has been shown over time to indicate either contamination in the fluid system or a particular breakdown
modality of the fluid, which is critical information to assess the health of the fluid as well as the machinery. By utilizing the field
device, it is possible for those operating machinery, in locations and situations where it is not practical to gather a sample for the
laboratory, to obtain quality in-service fluid analysis. This may be due to the need to have an analysis done in real-time, on-the-spot
to maximize the operational hours of equipment, or to have the analysis performed at a location where no laboratory analysis is
available.
TABLE 1 In-Service Lubricant Properties Reported by the Test
Method
Property Reporting Units
Oxidation Abs/0.1 mm
Antiwear Additive Abs/0.1 mm
Sulfation Abs/0.1 mm
Nitration Abs/cm
Soot Abs/cm
D7889 − 21
6. Interferences
6.1 Spectral interferences due to very high levels of external contamination in the fluid can yield errors with these measurements.
Common contaminants include the presence of API Group V lubricants at levels exceeding 5 % and antifreeze mixes at similar
levels.
7. Apparatus
7.1 A self-contained mid-infrared grating spectrometer with a coupled wipe-clean transmission cell as defined in Section 3.
7.2 This spectrometer shall have specific performance characteristics indicated in 7.3 – 7.5, with a Spectral Format in the form
-1
of absorbance as a function of wavenumber reported at a digital resolution of 2 cm .
7.3 Signal-to-Noise Ratio (S/N)—shall be adequate to provide the desired precision as indicated in Section 17. Practically, this
means that, over the range of measurement, the standard deviation of the obtained absorbance should be less than 0.001 AU. Based
on the capabilities of the spectrometer system, this may be achieved by co-adding a number of scans to improve the S/N as needed.
7.4 Spectral Resolution—shall be approximately 1.5 % of frequency being measured across the measurement range. For example,
-1 -1
at 1000 cm , the spectral resolution should be 15 cm . In order to qualify this resolution, a simple test using a 40 micron film of
polystyrene, a standard reference material for grating instruments as discussed in Practice E932 may be performed. The absorbance
-1
spectrum of this material measured with the spectrometer should show a peak at band number 12 (1028 cm ) of approximately
-1
0.29 AU and a peak at band number 2 (2924 cm ) of approximately 0.56 AU. Other spectral resolutions may provide accurate
results as well but the calculation parameters listed in Table 2 and Section 17 may be different from those listed.
7.5 Spectral Range—shallShall cover the frequencies necessary for calculation of all properties described in the method, which
-1 -1
is 960 cm to 3040 cm .
8. Reagents and Materials
8.1 The only materials required to make a measurement are either a shop rag or lint-free paper towel to clean the wipe-clean
transmission cell. No other materials or reagents are necessary.
9. Hazards
9.1 The apparatus utilizes a certified Li-Ion battery.
10. Sampling, Test Specimens, and Test Units
10.1 A sample of in-service fluid should be obtained. A minimum quantity of approximately 50 μL is needed to obtain one set of
TABLE 2 Specification for Calculation of Each In-Service Fluid
Property
Property Measurement, Baseline(s), Reporting
-1 -1
(cm ) (cm ) Units
Oxidation Average Average Abs/0.1 mm
1800–1670 1815 to 1805
Antiwear Additive Average Average Abs/0.1 mm
1025–960 1060 to 1030 and
1812 to 1803
Sulfation Average Average Abs/0.1 mm
1180–1120 1210 to 1200 and
1115 to 1105
Nitration 100·Single Average Abs/cm
Point at 1630 1607 to 1597 and
1847 to 1837
Soot 100·Single None Abs/cm
Point at 2000
D7889 − 21
measurements as defined in Table 2. The sample should be representative of the system. If such equipment is available, the sample
is preferably obtained as described in Practice D4057.
11. Preparation of Apparatus
11.1 A quality collection of the infrared absorbance spectrum is assured by several internal quality checks, which include check
fluid, pathlength, clean cell, and loaded cell monitoring.
11.1.1 Check fluid and pathlength monitoring (described in Practice D7418) are performed on a periodic basis according to
manufacturer’s recommendations.
11.1.2 In order to verify that the wipe-clean transmission cell is empty and clean, a cell background is taken in real-time and a
raw absorbance spectrum is calculated using a previously archived, known, empty, and clean cell background.
-1 -1 -1
11.1.2.1 By measuring the maximum peak height between 3000 cm and 2800 cm relative to a baseline at 2700 cm , it can be
determined whether the cell is clean. When the absorbance value is greater than a pre-set limit of 0.2 AU, the cell is considered
not clean.
11.1.2.2 This check is performed before any cell background to be used in the calculation of fluid properties is obtained, and the
user is warned if the check fails.
11.1.3 A cell loading check (as described in Practice D7418) is performed on each loaded sample to ensure that the cell is fully
loaded. Such a check is performed according to manufacturer’s recommendations.
11.1.3.1 If the cell is determined to not be fully loaded, a message that the cell is not fully loaded is displayed alongside the results
of the analysis. It should be noted that due to the nature of the design for field use, the wipe clean transmission cell has no need
for fringe correction.
11.2 Ensure that wipe-clean transmission cell is clean by visual inspecti
...