ASTM D7624-22
(Test Method)Standard 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
Standard 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
SIGNIFICANCE AND USE
5.1 There is a wide variety of nitration compounds that may be produced and accumulate when oils react with gaseous nitrates formed during the engine combustion process. These nitration products may increase the viscosity, acidity and insolubles in the oil, which may lead to ring sticking and filter plugging. Monitoring of nitration products is therefore an important parameter in determining overall machinery health and should be considered in conjunction with data from other tests such as atomic emission (AE) and atomic absorption (AA) spectroscopy for wear metal analysis (Test Method D5185), physical property tests (Test Methods D445 and D2896), and other FT-IR oil analysis methods for oxidation (Test Method D7414), sulfate by-products (Test Method D7415), and additive depletion (Test Method D7412), which also assess elements of the oil’s condition (1-6).
SCOPE
1.1 This test method covers monitoring nitration in gasoline and natural gas engine oils as well as in other types of lubricants where nitration by-products may form due to the combustion process or other routes of formation of nitration compounds.
1.2 This test method uses FT-IR spectroscopy for monitoring build-up of nitration by-products in in-service petroleum and hydrocarbon-based lubricants as a result of normal machinery operation. Nitration levels in gasoline and natural gas engine oils rise as combustion by-products react with the oil as a result of exhaust gas recirculation or a blow-by. This test method is designed as a fast, simple spectroscopic check for monitoring of nitration in in-service petroleum and hydrocarbon-based lubricants with the objective of helping diagnose the operational condition of the machine based on measuring the level of nitration in the oil.
1.3 Acquisition of FT-IR spectral data for measuring nitration in in-service oil and lubricant samples is described in Practice D7418. In this test method, measurement and data interpretation parameters for nitration using both direct trend analysis and differential (spectral subtraction) trend analysis are presented.
1.4 This test method is based on trending of spectral changes associated with nitration in in-service petroleum and hydrocarbon-based lubricants. For direct trend analysis, values are recorded directly from absorption spectra and reported in units of 100*absorbance per 0.1 mm pathlength (or equivalently absorbance units per centimetre). For differential trend analysis, values are recorded from the differential spectra (spectrum obtained by subtraction of the spectrum of the reference oil from that of the in-service oil) and reported in units of 100*absorbance per 0.1 mm pathlength (or equivalently absorbance units per centimetre). Warnings or alarm limits can be set on the basis of a fixed maximum value for a single measurement or, alternatively, can be based on a rate of change of the response measured (1).2 In either case, such maintenance action limits should be determined through statistical analysis, history of the same or similar equipment, round robin tests or other methods in conjunction with the correlation of nitration changes to equipment performance.
Note 1: It is not the intent of this test method to establish or recommend normal, cautionary, warning or alert limits for any machinery. Such limits should be established in conjunction with advice and guidance from the machinery manufacturer and maintenance group.
1.5 This test method is for petroleum and hydrocarbon-based lubricants and is not applicable for ester-based oils, including polyol esters or phosphate esters.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6.1 Exception—The unit for wave numbers is cm-1.
1.7 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 estab...
General Information
- Status
- Published
- Publication Date
- 30-Sep-2022
- Technical Committee
- D02 - Petroleum Products, Liquid Fuels, and Lubricants
Relations
- Effective Date
- 01-Apr-2024
- Refers
ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants - Effective Date
- 15-Dec-2023
- Effective Date
- 01-Nov-2023
- Refers
ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants - Effective Date
- 01-Jul-2023
- Effective Date
- 01-Apr-2018
- Effective Date
- 15-Dec-2016
- Effective Date
- 01-Jul-2014
- Effective Date
- 01-Jul-2014
- Effective Date
- 01-May-2014
- Effective Date
- 01-May-2013
- Effective Date
- 01-May-2013
- Effective Date
- 15-Apr-2012
- Effective Date
- 01-Nov-2011
- Effective Date
- 01-Oct-2010
- Effective Date
- 01-Mar-2010
Overview
ASTM D7624-22: Standard 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
ASTM D7624-22 provides a standardized approach for monitoring nitration in in-service petroleum and hydrocarbon-based lubricants. By utilizing Fourier Transform Infrared (FT-IR) spectrometry, this method allows for accurate and efficient detection of nitration by-products formed during engine operation. Nitration can adversely impact the physical and chemical properties of lubricants, potentially leading to increased viscosity, oil acidity, and insoluble accumulation, which in turn may cause filter plugging and mechanical wear. The trend analysis of nitration levels serves as a critical tool for predictive maintenance and maximizing equipment reliability.
Key Topics
- Nitration Monitoring: Focus on detecting nitration by-products formed in lubricants as a result of combustion processes, blow-by, or exhaust gas recirculation.
- FT-IR Spectrometry: Application of FT-IR for obtaining and analyzing absorption spectra to quantify nitration levels. Both direct and differential trend analysis methods are described.
- Data Trending: Trending of spectral changes helps track lubricant condition over time, providing valuable insights into engine health and optimal maintenance intervals.
- Interferences: Consideration of factors such as high water content, soot, and aromatic compounds that may interfere with FT-IR measurements.
- Reporting: Nitration values are to be trended and interpreted relative to unused oils of the same formulation, and maintenance actions are to be based on statistical data and equipment history.
Applications
ASTM D7624-22 is widely used in industrial maintenance and equipment reliability programs, specifically for:
- Engine Oil Analysis: Effective in monitoring gasoline and natural gas engine oils for nitration increases during regular operation.
- Predictive Maintenance: Enables early detection of lubrication issues, minimizing downtime by scheduling oil changes and maintenance based on actual lubricant condition rather than fixed intervals.
- Fleet and Equipment Health Monitoring: Supports machinery health analysis in sectors such as transportation, power generation, petrochemical, and manufacturing.
- Integrated Lubricant Analysis: Complements other oil condition monitoring techniques including atomic emission spectroscopy (for wear metals), kinematic viscosity, and base number tests, as well as FT-IR-based assessments for oxidation, sulfation, and additive depletion.
Related Standards
Implementing ASTM D7624-22 often involves cross-referencing or combining with the following lubricating oil and FT-IR analysis standards:
- ASTM D445: Test Method for Kinematic Viscosity of Transparent and Opaque Liquids
- ASTM D2896: Test Method for Base Number Determination of Petroleum Products
- ASTM D5185: Test Method for Multi-Element Determination by ICP-AES in lubricating oils
- ASTM D7412, D7414, D7415: FT-IR-based methods for monitoring phosphate antiwear additives, oxidation, and sulfate by-products, respectively
- ASTM D7418: Practice for Set-Up and Operation of FT-IR Spectrometers for In-Service Oil Monitoring
- ASTM D4175: Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
Practical Value
Adhering to ASTM D7624-22 delivers the following benefits for organizations focused on oil analysis and machinery maintenance:
- Early Detection of Oil Degradation: Helps prevent equipment failures by identifying nitration-induced oil deterioration before major damage occurs.
- Cost Savings: Supports longer oil drain intervals and reduces unscheduled downtime, maintenance costs, and part replacement.
- Standardized Analysis: Ensures consistency and reliability in lubricant condition assessment across laboratories and maintenance operations.
- Comprehensive Machinery Health Insight: When combined with other analytical methods, provides a full picture of machinery and lubricant condition, supporting data-driven maintenance decisions.
Keywords: ASTM D7624-22, FT-IR spectrometry, nitration monitoring, in-service lubricants, petroleum lubricants, trend analysis, condition monitoring, oil analysis, machinery health, lubricant maintenance.
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ASTM D7624-22 - Standard 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
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Frequently Asked Questions
ASTM D7624-22 is a standard published by ASTM International. Its full title is "Standard 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". This standard covers: SIGNIFICANCE AND USE 5.1 There is a wide variety of nitration compounds that may be produced and accumulate when oils react with gaseous nitrates formed during the engine combustion process. These nitration products may increase the viscosity, acidity and insolubles in the oil, which may lead to ring sticking and filter plugging. Monitoring of nitration products is therefore an important parameter in determining overall machinery health and should be considered in conjunction with data from other tests such as atomic emission (AE) and atomic absorption (AA) spectroscopy for wear metal analysis (Test Method D5185), physical property tests (Test Methods D445 and D2896), and other FT-IR oil analysis methods for oxidation (Test Method D7414), sulfate by-products (Test Method D7415), and additive depletion (Test Method D7412), which also assess elements of the oil’s condition (1-6). SCOPE 1.1 This test method covers monitoring nitration in gasoline and natural gas engine oils as well as in other types of lubricants where nitration by-products may form due to the combustion process or other routes of formation of nitration compounds. 1.2 This test method uses FT-IR spectroscopy for monitoring build-up of nitration by-products in in-service petroleum and hydrocarbon-based lubricants as a result of normal machinery operation. Nitration levels in gasoline and natural gas engine oils rise as combustion by-products react with the oil as a result of exhaust gas recirculation or a blow-by. This test method is designed as a fast, simple spectroscopic check for monitoring of nitration in in-service petroleum and hydrocarbon-based lubricants with the objective of helping diagnose the operational condition of the machine based on measuring the level of nitration in the oil. 1.3 Acquisition of FT-IR spectral data for measuring nitration in in-service oil and lubricant samples is described in Practice D7418. In this test method, measurement and data interpretation parameters for nitration using both direct trend analysis and differential (spectral subtraction) trend analysis are presented. 1.4 This test method is based on trending of spectral changes associated with nitration in in-service petroleum and hydrocarbon-based lubricants. For direct trend analysis, values are recorded directly from absorption spectra and reported in units of 100*absorbance per 0.1 mm pathlength (or equivalently absorbance units per centimetre). For differential trend analysis, values are recorded from the differential spectra (spectrum obtained by subtraction of the spectrum of the reference oil from that of the in-service oil) and reported in units of 100*absorbance per 0.1 mm pathlength (or equivalently absorbance units per centimetre). Warnings or alarm limits can be set on the basis of a fixed maximum value for a single measurement or, alternatively, can be based on a rate of change of the response measured (1).2 In either case, such maintenance action limits should be determined through statistical analysis, history of the same or similar equipment, round robin tests or other methods in conjunction with the correlation of nitration changes to equipment performance. Note 1: It is not the intent of this test method to establish or recommend normal, cautionary, warning or alert limits for any machinery. Such limits should be established in conjunction with advice and guidance from the machinery manufacturer and maintenance group. 1.5 This test method is for petroleum and hydrocarbon-based lubricants and is not applicable for ester-based oils, including polyol esters or phosphate esters. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6.1 Exception—The unit for wave numbers is cm-1. 1.7 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 estab...
SIGNIFICANCE AND USE 5.1 There is a wide variety of nitration compounds that may be produced and accumulate when oils react with gaseous nitrates formed during the engine combustion process. These nitration products may increase the viscosity, acidity and insolubles in the oil, which may lead to ring sticking and filter plugging. Monitoring of nitration products is therefore an important parameter in determining overall machinery health and should be considered in conjunction with data from other tests such as atomic emission (AE) and atomic absorption (AA) spectroscopy for wear metal analysis (Test Method D5185), physical property tests (Test Methods D445 and D2896), and other FT-IR oil analysis methods for oxidation (Test Method D7414), sulfate by-products (Test Method D7415), and additive depletion (Test Method D7412), which also assess elements of the oil’s condition (1-6). SCOPE 1.1 This test method covers monitoring nitration in gasoline and natural gas engine oils as well as in other types of lubricants where nitration by-products may form due to the combustion process or other routes of formation of nitration compounds. 1.2 This test method uses FT-IR spectroscopy for monitoring build-up of nitration by-products in in-service petroleum and hydrocarbon-based lubricants as a result of normal machinery operation. Nitration levels in gasoline and natural gas engine oils rise as combustion by-products react with the oil as a result of exhaust gas recirculation or a blow-by. This test method is designed as a fast, simple spectroscopic check for monitoring of nitration in in-service petroleum and hydrocarbon-based lubricants with the objective of helping diagnose the operational condition of the machine based on measuring the level of nitration in the oil. 1.3 Acquisition of FT-IR spectral data for measuring nitration in in-service oil and lubricant samples is described in Practice D7418. In this test method, measurement and data interpretation parameters for nitration using both direct trend analysis and differential (spectral subtraction) trend analysis are presented. 1.4 This test method is based on trending of spectral changes associated with nitration in in-service petroleum and hydrocarbon-based lubricants. For direct trend analysis, values are recorded directly from absorption spectra and reported in units of 100*absorbance per 0.1 mm pathlength (or equivalently absorbance units per centimetre). For differential trend analysis, values are recorded from the differential spectra (spectrum obtained by subtraction of the spectrum of the reference oil from that of the in-service oil) and reported in units of 100*absorbance per 0.1 mm pathlength (or equivalently absorbance units per centimetre). Warnings or alarm limits can be set on the basis of a fixed maximum value for a single measurement or, alternatively, can be based on a rate of change of the response measured (1).2 In either case, such maintenance action limits should be determined through statistical analysis, history of the same or similar equipment, round robin tests or other methods in conjunction with the correlation of nitration changes to equipment performance. Note 1: It is not the intent of this test method to establish or recommend normal, cautionary, warning or alert limits for any machinery. Such limits should be established in conjunction with advice and guidance from the machinery manufacturer and maintenance group. 1.5 This test method is for petroleum and hydrocarbon-based lubricants and is not applicable for ester-based oils, including polyol esters or phosphate esters. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6.1 Exception—The unit for wave numbers is cm-1. 1.7 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 estab...
ASTM D7624-22 is classified under the following ICS (International Classification for Standards) categories: 75.100 - Lubricants, industrial oils and related products; 75.160.20 - Liquid fuels. The ICS classification helps identify the subject area and facilitates finding related standards.
ASTM D7624-22 has the following relationships with other standards: It is inter standard links to ASTM D445-24, ASTM D4175-23a, ASTM D445-23, ASTM D4175-23e1, ASTM D5185-18, ASTM D445-16, ASTM D445-14e1, ASTM D445-14, ASTM E177-14, ASTM E177-13, ASTM E691-13, ASTM D445-12, ASTM E691-11, ASTM E177-10, ASTM E131-10. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
ASTM D7624-22 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
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.
Designation: D7624 − 22
Standard 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
This standard is issued under the fixed designation D7624; 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* lently absorbance units per centimetre). Warnings or alarm
limits can be set on the basis of a fixed maximum value for a
1.1 This test method covers monitoring nitration in gasoline
single measurement or, alternatively, can be based on a rate of
and natural gas engine oils as well as in other types of
change of the response measured (1). In either case, such
lubricants where nitration by-products may form due to the
maintenance action limits should be determined through sta-
combustion process or other routes of formation of nitration
tistical analysis, history of the same or similar equipment,
compounds.
round robin tests or other methods in conjunction with the
1.2 This test method uses FT-IR spectroscopy for monitor-
correlation of nitration changes to equipment performance.
ing build-up of nitration by-products in in-service petroleum
NOTE 1—It is not the intent of this test method to establish or
and hydrocarbon-based lubricants as a result of normal ma-
recommend normal, cautionary, warning or alert limits for any machinery.
chinery operation. Nitration levels in gasoline and natural gas
Suchlimitsshouldbeestablishedinconjunctionwithadviceandguidance
engine oils rise as combustion by-products react with the oil as
from the machinery manufacturer and maintenance group.
a result of exhaust gas recirculation or a blow-by. This test
1.5 This test method is for petroleum and hydrocarbon-
method is designed as a fast, simple spectroscopic check for
based lubricants and is not applicable for ester-based oils,
monitoring of nitration in in-service petroleum and
including polyol esters or phosphate esters.
hydrocarbon-based lubricants with the objective of helping
1.6 The values stated in SI units are to be regarded as
diagnose the operational condition of the machine based on
standard. No other units of measurement are included in this
measuring the level of nitration in the oil.
standard.
1.3 Acquisition of FT-IR spectral data for measuring nitra-
-1
1.6.1 Exception—The unit for wave numbers is cm .
tion in in-service oil and lubricant samples is described in
1.7 This standard does not purport to address all of the
Practice D7418. In this test method, measurement and data
safety concerns, if any, associated with its use. It is the
interpretation parameters for nitration using both direct trend
responsibility of the user of this standard to establish appro-
analysis and differential (spectral subtraction) trend analysis
priate safety, health, and environmental practices and deter-
are presented.
mine the applicability of regulatory limitations prior to use.
1.4 This test method is based on trending of spectral
1.8 This international standard was developed in accor-
changes associated with nitration in in-service petroleum and
dance with internationally recognized principles on standard-
hydrocarbon-based lubricants. For direct trend analysis, values
ization established in the Decision on Principles for the
are recorded directly from absorption spectra and reported in
Development of International Standards, Guides and Recom-
units of 100*absorbance per 0.1 mm pathlength (or equiva-
mendations issued by the World Trade Organization Technical
lently absorbance units per centimetre). For differential trend
Barriers to Trade (TBT) Committee.
analysis, values are recorded from the differential spectra
(spectrum obtained by subtraction of the spectrum of the
2. Referenced Documents
reference oil from that of the in-service oil) and reported in
2.1 ASTM Standards:
units of 100*absorbance per 0.1 mm pathlength (or equiva-
D445 Test Method for Kinematic Viscosity of Transparent
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of The boldface numbers in parentheses refer to a list of references at the end of
Subcommittee D02.96.03 on FTIR Testing Practices and Techniques Related to this standard.
In-Service Lubricants. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2022. Published October 2022. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2010. Last previous edition approved in 2021 as D7624 – 21. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D7624-22. 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
D7624 − 22
and Opaque Liquids (and Calculation of Dynamic Viscos- insolubles in the oil, which may lead to ring sticking and filter
ity) plugging. Monitoring of nitration products is therefore an
D2896 Test Method for Base Number of Petroleum Products important parameter in determining overall machinery health
by Potentiometric Perchloric Acid Titration and should be considered in conjunction with data from other
D4175 Terminology Relating to Petroleum Products, Liquid testssuchasatomicemission(AE)andatomicabsorption(AA)
Fuels, and Lubricants spectroscopy for wear metal analysis (Test Method D5185),
D5185 Test Method for Multielement Determination of physical property tests (Test Methods D445 and D2896), and
Used and Unused Lubricating Oils and Base Oils by other FT-IR oil analysis methods for oxidation (Test Method
Inductively Coupled Plasma Atomic Emission Spectrom- D7414), sulfate by-products (Test Method D7415), and addi-
etry (ICP-AES) tive depletion (Test Method D7412), which also assess ele-
D7412 Test Method for Condition Monitoring of Phosphate ments of the oil’s condition (1-6).
Antiwear Additives in In-Service Petroleum and Hydro-
6. Interferences
carbon Based Lubricants byTrendAnalysis Using Fourier
Transform Infrared (FT-IR) Spectrometry 6.1 Refer to Practice D7418 for a list of common interfer-
D7414 Test Method for Condition Monitoring of Oxidation
ents affecting the quality of all FTIR generated spectra.
in In-Service Petroleum and Hydrocarbon Based Lubri-
6.2 When the sample has increased baseline (soot >2.5 %)
cants byTrendAnalysis Using FourierTransform Infrared
or interferent peak present, follow the optional procedure in
(FT-IR) Spectrometry
Practice D7418 Section 11 depending on measurement accu-
D7415 Test Method for Condition Monitoring of Sulfate
racy needs.
By-Products in In-Service Petroleum and Hydrocarbon
-1
6.3 Some aromatic compounds absorb in the 1600 cm and
Based Lubricants by TrendAnalysis Using Fourier Trans-
-1
1500 cm regions and may interfere with the nitration signal.
form Infrared (FT-IR) Spectrometry
D7418 Practice for Set-Up and Operation of Fourier Trans-
7. Apparatus
form Infrared (FT-IR) Spectrometers for In-Service Oil
7.1 Fourier transform infrared spectrometer equipped with
Condition Monitoring
sample cell, filter (optional), and pumping system (optional) as
E131 Terminology Relating to Molecular Spectroscopy
specified in Practice D7418.
E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
7.2 FT-IR Spectral Acquisition Parameters—Set FT-IR
E691 Practice for Conducting an Interlaboratory Study to
spectral acquisition parameters according to instructions in
Determine the Precision of a Test Method
Practice D7418.
3. Terminology 8. Sampling
3.1 Definitions: 8.1 Obtain a sample of the in-service oil and a sample of the
3.1.1 For definitions of terms relating to infrared spectros- reference oil (required only for differential trend analysis)
copy used in this test method, refer to Terminology E131. For according to the protocol described in Practice D7418.
definition of terms related to in-service oil condition
9. Preparation of Apparatus
monitoring, refer to Practice D7418 and Terminology D4175.
3.1.2 machinery health, n—a qualitative expression of the
9.1 Rinse, flush, and clean the sample cell, inlet lines, and
operational status of a machine sub-component, component or
inlet filter according to instructions in Practice D7418.
entire machine, used to communicate maintenance and opera-
9.2 Monitor cell pathlength as specified in Practice D7418.
tional recommendations or requirements in order to continue
operation, schedule maintenance or take immediate mainte-
10. Procedure
nance action.
10.1 Collect a background spectrum according to the pro-
cedure specified in Section 9 of Practice D7418.
4. Summary of Test Method
10.2 Differential Trend Analysis Only—Collectthespectrum
4.1 This test method uses FT-IR spectrometry to monitor
of a reference oil sample, according to the procedure specified
nitration levels in in-service petroleum and hydrocarbon-based
in Section 9 of Practice D7418.
lubricants. The FT-IR spectra of in-service oil samples are
collected acco
...
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: D7624 − 21 D7624 − 22
Standard 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
This standard is issued under the fixed designation D7624; 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*
1.1 This test method covers monitoring nitration in gasoline and natural gas engine oils as well as in other types of lubricants
where nitration by-products may form due to the combustion process or other routes of formation of nitration compounds.
1.2 This test method uses FT-IR spectroscopy for monitoring build-up of nitration by-products in in-service petroleum and
hydrocarbon-based lubricants as a result of normal machinery operation. Nitration levels in gasoline and natural gas engine oils
rise as combustion by-products react with the oil as a result of exhaust gas recirculation or a blow-by. This test method is designed
as a fast, simple spectroscopic check for monitoring of nitration in in-service petroleum and hydrocarbon-based lubricants with the
objective of helping diagnose the operational condition of the machine based on measuring the level of nitration in the oil.
1.3 Acquisition of FT-IR spectral data for measuring nitration in in-service oil and lubricant samples is described in Practice
D7418. In this test method, measurement and data interpretation parameters for nitration using both direct trend analysis and
differential (spectral subtraction) trend analysis are presented.
1.4 This test method is based on trending of spectral changes associated with nitration in in-service petroleum and
hydrocarbon-based lubricants. For direct trend analysis, values are recorded directly from absorption spectra and reported in units
of 100*absorbance per 0.1 mm pathlength (or equivalently absorbance units per centimetre). For differential trend analysis, values
are recorded from the differential spectra (spectrum obtained by subtraction of the spectrum of the reference oil from that of the
in-service oil) and reported in units of 100*absorbance per 0.1 mm pathlength (or equivalently absorbance units per centimetre).
Warnings or alarm limits can be set on the basis of a fixed maximum value for a single measurement or, alternatively, can be based
on a rate of change of the response measured (1). In either case, such maintenance action limits should be determined through
statistical analysis, history of the same or similar equipment, round robin tests or other methods in conjunction with the correlation
of nitration changes to equipment performance.
NOTE 1—It is not the intent of this test method to establish or recommend normal, cautionary, warning or alert limits for any machinery. Such limits should
be established in conjunction with advice and guidance from the machinery manufacturer and maintenance group.
1.5 This test method is for petroleum and hydrocarbon-based lubricants and is not applicable for ester-based oils, including polyol
esters or phosphate esters.
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 Dec. 1, 2021Oct. 1, 2022. Published January 2022October 2022. Originally approved in 2010. Last previous edition approved in 20182021 as
D7624 – 18.D7624 – 21. DOI: 10.1520/D7624-21.10.1520/D7624-22.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
*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
D7624 − 22
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
-1
1.6.1 Exception—The unit for wave numbers is cm .
1.7 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.8 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:
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D2896 Test Method for Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D5185 Test Method for Multielement Determination of Used and Unused Lubricating Oils and Base Oils by Inductively
Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
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
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
E131 Terminology Relating to Molecular Spectroscopy
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
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms relating to infrared spectroscopy used in this test method, refer to Terminology E131. For definition
of terms related to in-service oil condition monitoring, refer to Practice D7418 and Terminology D4175.
3.1.2 machinery health, n—a qualitative expression of the operational status of a machine sub-component, component or entire
machine, used to communicate maintenance and operational recommendations or requirements in order to continue operation,
schedule maintenance or take immediate maintenance action.
4. Summary of Test Method
4.1 This test method uses FT-IR spectrometry to monitor nitration levels in in-service petroleum and hydrocarbon-based
lubricants. The FT-IR spectra of in-service oil samples are collected according to the protocol for either direct trend analysis or
differential trend analysis described in Practice D7418, and the levels of nitration are measured using the peak height measurements
described herein.
5. Significance and Use
5.1 There is a wide variety of nitration compounds that may be produced and accumulate when oils react with gaseous nitrates
formed during the engine combustion process. These nitration products may increase the viscosity, acidity and insolubles in the
oil, which may lead to ring sticking and filter plugging. Monitoring of nitration products is therefore an important parameter in
determining overall machinery health and should be considered in conjunction with data from other tests such as atomic emission
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.
D7624 − 22
(AE) and atomic absorption (AA) spectroscopy for wear metal analysis (Test Method D5185), physical property tests (Test
Methods D445 and D2896), and other FT-IR oil analysis methods for oxidation (Test Method D7414), sulfate by-products (Test
Method D7415), and additive depletion (Test Method D7412), which also assess elements of the oil’s condition (1-6).
6. Interferences
6.1 Very high water levelsRefer to Practice D7418 can interfere with the nitration measurement. for a list of common interferents
affecting the quality of all FTIR generated spectra.
6.2 Conjugated ketones, quinones, unsaturated carboxylic acids and carboxylic acid salts (formed due to the reaction of acids with
overbased oil additives) are also sources of interference. When the sample has increased baseline (soot >2.5 %) or interferent peak
present, follow the optional procedure in Practice D7418 Section 11 depending on measurement accuracy needs.
-1 -1
6.3 Some aromatic compounds absorb in the 1600 cm and 1500 cm regions and may interfere as well.with the nitration signal.
7. Apparatus
7.1 Fourier transform infrared spectrometer equipped with sample cell, filter (optional), and pumping system (optional) as
specified in Practice D7418.
7.2 FT-IR Spectral Acquisition Parameters—Set FT-IR spectral acquisition parameters according to instructions in Practice
D7418.
8. Sampling
8.1
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