ASTM D7686-23

Standard Test Method for Field-Based Condition Monitoring of Soot in In-Service Lubricants Using a Fixed-Filter Infrared (IR) Instrument

SIGNIFICANCE AND USE
5.1 This test method provides a simple field-based technique for condition monitoring of soot in in-service lubricants associated with combustion engines, machinery, and equipment used in industry and by the military. Critical applications should use laboratory-based test methods, such as Thermal Gravimetric Analysis (TGA) described in Test Method D5967, Annex A4. Infrared spectroscopy is a well-established laboratory method for evaluating soot levels in lubricants. This test method can be used to monitor soot build-up in lubricants and can indicate whether soot has accumulated to an extent that could significantly degrade the performance of the oil. High soot content can compromise lubricant performance and cause filter and oil passage blockage. Soot concentration should be considered in conjunction with data from other condition monitoring tests as described in Practice E2412 to determine whether the oil should be replaced to minimize machinery wear or failure, or both.
SCOPE
1.1 This test method pertains to field-based monitoring of soot in diesel crankcase engine oils as well as in other types of engine oils where soot may contaminate the lubricant as a result of a blow-by due to incomplete combustion of fuels. It is applicable to oils having soot levels of up to 12 % by mass.  
1.2 This test method uses filter-based infrared technology for monitoring of soot build-up in in-service petroleum and hydrocarbon-based lubricants as a result of normal machinery operation. Soot levels in engine oils rise as soot particles contaminate the oil as a result of exhaust gas recirculation from blow-by. This test method is designed as a fast, simple, and field-capable spectroscopic check for soot in in-service hydrocarbon-based lubricants with the objective of helping diagnose the operational condition of the machine based on measuring the level of soot in the oil.  
1.3 This test method is intended as a field test only, and should be treated as such. Critical applications should use laboratory based methods, such as Thermal Gravimetric Analysis (TGA) described in Test Method D5967, Annex A4.  
1.4 Acquisition of spectral data for measuring soot in in-service oil and lubricant samples with the use of a fixed-filter IR instrument is described in this test method. Calibration against prepared soot standards is also described.
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 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.  
1.7 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.

General Information

• Status: Published
• Publication Date: 28-Feb-2023
• ICS: 75.100 - Lubricants, industrial oils and related products
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.96.03 - FTIR Testing Practices and Techniques Related to In-Service Lubricants

Relations

• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 15-Dec-2023
• Refers: ASTM D6299-23a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Dec-2023
• Refers: ASTM E2412-23a - Standard Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
• Effective Date: 01-Nov-2023
• Refers: ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Jul-2023
• Refers: ASTM D6299-17b - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Dec-2017
• Refers: ASTM D6299-17a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Nov-2017
• Refers: ASTM D5967-17 - Standard Test Method for Evaluation of Diesel Engine Oils in T-8 Diesel Engine
• Effective Date: 01-May-2017
• Refers: ASTM D6299-17 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Jan-2017
• Refers: ASTM D5967-15a - Standard Test Method for Evaluation of Diesel Engine Oils in T-8 Diesel Engine
• Effective Date: 01-Oct-2015
• Refers: ASTM D5967-15 - Standard Test Method for Evaluation of Diesel Engine Oils in T-8 Diesel Engine
• Effective Date: 01-Apr-2015
• Refers: ASTM D5967-14 - Standard Test Method for Evaluation of Diesel Engine Oils in T-8 Diesel Engine
• Effective Date: 01-Oct-2014
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM D6299-13e1 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Oct-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013

Overview

ASTM D7686-23 establishes a standardized field-based test method for monitoring soot in in-service lubricants, specifically those used in combustion engines, industrial machinery, and military equipment. Utilizing a fixed-filter infrared (IR) instrument, this method provides a rapid, simple, and effective way to assess soot contamination in hydrocarbon-based lubricants such as diesel engine oils. The ability to carry out oil condition monitoring in the field is valuable for maintenance teams aiming to prevent lubricant failure, machinery wear, or costly downtime by timely identifying when soot levels reach critical thresholds.

This test method is intended for field use, with soot concentration results supporting decision-making in ongoing maintenance routines. For highly critical or precise applications, laboratory-based techniques like Thermal Gravimetric Analysis (TGA) are recommended instead.

Key Topics

• Field-Based Soot Detection: The method enables on-site analysis of soot concentration in lubricants, streamlining decision-making for oil replacement or engine service.
• Infrared Spectroscopy: Utilizes filter-based IR technology and horizontal attenuated total reflectance (HATR) to assess soot contamination, leveraging a wavelength range centered around 3.9 to 4.0 μm.
• Soot in Diesel and Engine Oils: Applicable to a variety of lubricants prone to soot contamination due to incomplete combustion or exhaust gas recirculation. The method is suitable for oils with up to 12% soot by mass.
• Operational Condition Assessment: By measuring soot content, maintenance teams can diagnose engine or equipment health and predict potential issues such as oil passage blockage or degraded lubricant performance.
• Calibration and Quality Control: The method outlines calibration against known soot standards and incorporates quality assurance measures using statistical controls to ensure accurate and consistent results.

Applications

ASTM D7686-23 is designed to be a practical diagnostic tool for maintenance professionals in diverse sectors:

• Industrial Engines: Enables routine in-service oil analysis for factory and plant equipment, helping protect against unplanned outages due to lubricant degradation caused by high soot levels.
• Diesel Fleets and Heavy Machinery: Provides a quick means to assess when oil changes are needed to minimize wear and prolong engine life in transport and construction vehicles.
• Military Equipment: Supports field maintenance teams working in remote or mobile settings by offering robust and portable condition monitoring of engines and equipment.
• Oil Analysis Programs: Integrates into broader lubricant condition monitoring strategies, complementing other tests like trend analysis using FT-IR as described in ASTM Practice E2412.

By using a field-capable IR spectrometer, users can instantly determine whether soot levels in lubricants are within acceptable ranges or require corrective action, promoting proactive maintenance and reducing the risk of failure.

Related Standards

The following ASTM standards are closely related and support best practices for lubricant and oil analysis:

• ASTM D5967: Test Method for Evaluation of Diesel Engine Oils (TGA), recommended for critical laboratory-based soot measurement.
• ASTM D4175: Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants.
• ASTM D6299: Practice for Applying Statistical Quality Assurance and Control Charting Techniques.
• ASTM D7418: Practice for Set-Up and Operation of FT-IR Spectrometers for Oil Condition Monitoring.
• ASTM E131: Terminology Relating to Molecular Spectroscopy.
• ASTM E177: Practice for Use of the Terms Precision and Bias in ASTM Test Methods.
• ASTM E691: Practice for Conducting an Interlaboratory Precision Study.
• ASTM E2412: Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using FT-IR Spectrometry.

Keywords: ASTM D7686, field-based soot monitoring, oil condition monitoring, infrared spectroscopy, diesel engine oil, in-service lubricants, hydrocarbon-based lubricants, machinery maintenance, lubricant analysis, equipment reliability.

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: D7686 − 23
Standard Test Method for
Field-Based Condition Monitoring of Soot in In-Service
Lubricants Using a Fixed-Filter Infrared (IR) Instrument
This standard is issued under the fixed designation D7686; 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* priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This test method pertains to field-based monitoring of
1.7 This international standard was developed in accor-
soot in diesel crankcase engine oils as well as in other types of
dance with internationally recognized principles on standard-
engine oils where soot may contaminate the lubricant as a
ization established in the Decision on Principles for the
result of a blow-by due to incomplete combustion of fuels. It is
Development of International Standards, Guides and Recom-
applicable to oils having soot levels of up to 12 % by mass.
mendations issued by the World Trade Organization Technical
1.2 This test method uses filter-based infrared technology
Barriers to Trade (TBT) Committee.
for monitoring of soot build-up in in-service petroleum and
2. Referenced Documents
hydrocarbon-based lubricants as a result of normal machinery
operation. Soot levels in engine oils rise as soot particles
2.1 ASTM Standards:
contaminate the oil as a result of exhaust gas recirculation from
D4175 Terminology Relating to Petroleum Products, Liquid
blow-by. This test method is designed as a fast, simple, and
Fuels, and Lubricants
field-capable spectroscopic check for soot in in-service
D5967 Test Method for Evaluation of Diesel Engine Oils in
hydrocarbon-based lubricants with the objective of helping
T-8 Diesel Engine
diagnose the operational condition of the machine based on
D6299 Practice for Applying Statistical Quality Assurance
measuring the level of soot in the oil.
and Control Charting Techniques to Evaluate Analytical
Measurement System Performance
1.3 This test method is intended as a field test only, and
D7418 Practice for Set-Up and Operation of Fourier Trans-
should be treated as such. Critical applications should use
form Infrared (FT-IR) Spectrometers for In-Service Oil
laboratory based methods, such as Thermal Gravimetric Analy-
Condition Monitoring
sis (TGA) described in Test Method D5967, Annex A4.
E131 Terminology Relating to Molecular Spectroscopy
1.4 Acquisition of spectral data for measuring soot in
E177 Practice for Use of the Terms Precision and Bias in
in-service oil and lubricant samples with the use of a fixed-
ASTM Test Methods
filter IR instrument is described in this test method. Calibration
E691 Practice for Conducting an Interlaboratory Study to
against prepared soot standards is also described.
Determine the Precision of a Test Method
NOTE 1—It is not the intent of this test method to establish or
E2412 Practice for Condition Monitoring of In-Service Lu-
recommend normal, cautionary, warning, or alert limits for any machinery.
bricants by Trend Analysis Using Fourier Transform
Such limits should be established in conjunction with advice and guidance
Infrared (FT-IR) Spectrometry
from the machinery manufacturer and maintenance group.
3. Terminology
1.5 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3.1 Definitions—For definitions of terms used in this test
standard.
method, refer to Terminology D4175.
1.6 This standard does not purport to address all of the
3.2 Definitions—For definitions of terms relating to infrared
safety concerns, if any, associated with its use. It is the
spectroscopy used in this test method, refer to Terminology
responsibility of the user of this standard to establish appro-
E131.
3.3 Definitions—For definition of terms related to in-service
This test method is under the jurisdiction of ASTM Committee D02 on
oil condition monitoring, refer to Practice D7418.
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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2023. Published April 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2011. Last previous edition approved in 2019 as D7686 – 19. Standards volume information, refer to the standard’s Document Summary page on
DOI:10.1520/D7686-23. 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
D7686 − 23
4. Summary of Test Method specifications. Any modifications may result in precision and
or bias that differ from the numbers listed in this test method.
4.1 This test method uses filter-based infrared spectrometry
to monitor levels of soot in in-service petroleum and
8. Reagents and Materials
hydrocarbon-based lubricants. The test method is meant to
serve as a field-based method to provide an indicator of soot 8.1 Calibration Standards—Calibration standards shall con-
level. A well homogenized sample of oil is applied to a sist of unused and soot-free 15w-40 diesel motor oil adulter-
Horizontal Attenuated Total Reflectance (HATR) crystal. In- ated with various concentrations of sub-micron particle size,
frared light is totally internally reflected through the HATR high-structure carbon black dispersed in the oil and mixed
crystal and then passed through a broadband infrared filter thoroughly. The resulting soot concentration shall be deter-
centered on 3.9 μm. The amount of infrared light reaching a mined by Thermal Gravimetric Analysis (TGA) as described in
detector is converted to a soot concentration by means of a Test Method D5967. Five standards uniformly covering a
calibration curve generated from the instrument response on range of approximately 0 % to 12 % by mass soot are required.
various soot standards. Precision information for Thermal Gravimetric Analysis
(TGA) in accordance with Test Method D5967 can be found in
5. Significance and Use Appendix X1.
5.1 This test method provides a simple field-based tech-
9. Sampling, Test Specimens, and Test Units
nique for condition monitoring of soot in in-service lubricants
associated with combustion engines, machinery, and equip- 9.1 General Requirements:
ment used in industry and by the military. Critical applications 9.1.1 It is recommended that in-service oil or lubricant
should use laboratory-based test methods, such as Thermal samples to be analyzed by this test method are sampled using
Gravimetric Analysis (TGA) described in Test Method D5967, procedures outlined in Practice D7418.
Annex A4. Infrared spectroscopy is a well-established labora- 9.1.2 Protect samples from excessive temperatures prior to
tory method for evaluating soot levels in lubricants. This test testing.
method can be used to monitor soot build-up in lubricants and 9.1.3 Do not test samples stored in leaky containers. Discard
can indicate whether soot has accumulated to an extent that and obtain a new sample if leaks are detected.
could significantly degrade the performance of the oil. High
9.2 When analyzing samples using this test method, shake
soot content can compromise lubricant performance and cause
the sample vigorously until the sample is adequately homog-
filter and oil passage blockage. Soot concentration should be
enized and no sediment is adhered to the bottom or sides of the
considered in conjunction with data from other condition
vessel.
monitoring tests as described in Practice E2412 to determine
whether the oil should be replaced to minimize machinery wear
10. Preparation of Apparatus
or failure, or both.
10.1 Before use, the instrument needs to be calibrated
according to the procedure described in Section 11. This
6. Interferences
calibration can be performed by the instrument manufacturer
6.1 Some types of dirt or wear debris may cause a positive
prior to delivery of the instrument to the end user.
bias. In most cases, the bias will be small and will likely also
10.2 Before analyzing samples, the instrument should be
affect Thermal Gravimetric Analysis (TGA) as described in
allowed to warm up for at least 1 h to ensure the analyzer is
Test Method D5967.
stabilized.
6.2 Large amounts of free water in an oil sample may cause
10.3 Before use, the instrument should be qualified by
a positive bias.
running quality control check samples consisting of a known
soot concentration as determined by Test Method D5967 that
7. Apparatus
span the range that the instrument is calibrated in. These
7.1 Filter-Based Infrared Spectrometer:
samples should consist of at least one sample in the bottom
7.1.1 Infrared Spectrometer—The type of apparatus suitable
third of the range, one sample in the middle third of the range
for this test method consists of a tungsten source, a 4 reflection
and one sample in the top third of the range. Apply the control
cubic zirconia horizontal attenuated total reflectance cell, an
charting procedures described in Practice D6299 to establish
infrared filter paired to a pyroelectric detector, an A/D
that the analyzer is in-statistical-control. Any system that is
converter, and a microprocessor capable of storing an internal
found to be out-of-statistical-control cannot be used until the
calibrations and converting instrument response into soot
root cause(s) of out-of-control is identified and corrected.
concentration.
7.1.2 Infrared Filter Specifications—A broadband infrared
11. Calibration and Standardization
filter with a peak wavelength centered between 3.9 μm to
11.1 Calibration Standards—Refer to 8.1 for calibration
4.0 μm, and a filter half width of 0.15 μm 6 0.05 μm shall be
standard description.
used.
7.1.3 Other spectrometer configurations may provide ad- 11.2 Calibration:
equate results; however the precision and bias data listed with 11.2.1 Equilibrate all samples to the temperature of the
this test method was collected based on these apparatus laboratory (15 °C to 27 °C) prior to analysis.
D7686 − 23
11.2.2 Allow the instrument to warm up for at least 1 h 12. Procedure
before attempting a calibration.
12.1 Equilibrate the samples to between 15 °C and 27 °C
11.2.3 Calibration standards shoul
...

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: D7686 − 19 D7686 − 23
Standard Test Method for
Field-Based Condition Monitoring of Soot in In-Service
Lubricants Using a Fixed-Filter Infrared (IR) Instrument
This standard is issued under the fixed designation D7686; 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 pertains to field-based monitoring of soot in diesel crankcase engine oils as well as in other types of engine
oils where soot may contaminate the lubricant as a result of a blow-by due to incomplete combustion of fuels. It is applicable to
oils having soot levels of up to 12 % by mass.
1.2 This test method uses filter-based infrared technology for monitoring of soot build-up in in-service petroleum and
hydrocarbon-based lubricants as a result of normal machinery operation. Soot levels in engine oils rise as soot particles
contaminate the oil as a result of exhaust gas recirculation from blow-by. This test method is designed as a fast, simple, and
field-capable spectroscopic check for soot in in-service hydrocarbon-based lubricants with the objective of helping diagnose the
operational condition of the machine based on measuring the level of soot in the oil.
1.3 This test method is intended as a field test only, and should be treated as such. Critical applications should use laboratory based
methods, such as Thermal Gravimetric Analysis (TGA) described in Test Method D5967, Annex A4.
1.4 Acquisition of spectral data for measuring soot in in-service oil and lubricant samples with the use of a fixed-filter IR
instrument is described in this test method. Calibration against prepared soot standards is also described.
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
1.7 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.
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 July 15, 2019March 1, 2023. Published September 2019April 2023. Originally approved in 2011. Last previous edition approved in 20112019
as D7686 – 11.D7686 – 19. DOI:10.1520/D7686-19.DOI:10.1520/D7686-23.
*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
D7686 − 23
2. Referenced Documents
2.1 ASTM Standards:
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D5967 Test Method for Evaluation of Diesel Engine Oils in T-8 Diesel Engine
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
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
E2412 Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR)
Spectrometry
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, refer to Terminology D4175.
3.2 Definitions—For definitions of terms relating to infrared spectroscopy used in this test method, refer to Terminology E131.
3.3 Definitions—For definition of terms related to in-service oil condition monitoring, refer to Practice D7418.
4. Summary of Test Method
4.1 This test method uses filter-based infrared spectrometry to monitor levels of soot in in-service petroleum and hydrocarbon-
based lubricants. The test method is meant to serve as a field-based method to provide an indicator of soot level. A well
homogenized sample of oil is applied to a Horizontal Attenuated Total Reflectance (HATR) crystal. Infrared light is totally
internally reflected through the HATR crystal and then passed through a broadband infrared filter centered on 3.9 μm. The amount
of infrared light reaching a detector is converted to a soot concentration by means of a calibration curve generated from the
instrument response on various soot standards.
5. Significance and Use
5.1 This test method provides a simple field-based technique for condition monitoring of soot in in-service lubricants associated
with combustion engines, machinery, and equipment used in industry and by the military. Critical applications should use
laboratory-based test methods, such as Thermal Gravimetric Analysis (TGA) described in Test Method D5967, Annex A4. Infrared
spectroscopy is a well-established laboratory method for evaluating soot levels in lubricants. This test method can be used to
monitor soot build-up in lubricants and can indicate whether soot has accumulated to an extent that could significantly degrade
the performance of the oil. High soot content can compromise lubricant performance and cause filter and oil passage blockage.
Soot concentration should be considered in conjunction with data from other condition monitoring tests as described in Practice
E2412 to determine whether the oil should be replaced to minimize machinery wear or failure, or both.
6. Interferences
6.1 Some types of dirt or wear debris may cause a positive bias. In most cases, the bias will be small and will likely also affect
Thermal Gravimetric Analysis (TGA) as described in Test Method D5967.
6.2 Large amounts of free water in an oil sample may cause a positive bias.
7. Apparatus
7.1 Filter-Based Infrared Spectrometer:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
D7686 − 23
7.1.1 Infrared Spectrometer—The type of apparatus suitable for this test method consists of a tungsten source, a 4 reflection cubic
zirconia horizontal attenuated total reflectance cell, an infrared filter paired to a pyroelectric detector, an A/D converter, and a
microprocessor capable of storing an internal calibrations and converting instrument response into soot concentration.
7.1.2 Infrared Filter Specifications—A broadband infrared filter with a peak wavelength centered between 3.9 μm to 4.0 μm, and
a filter half width of 0.15 μm 6 0.05 μm shall be used.
7.1.3 Other spectrometer configurations may provide adequate results; however the precision and bias data listed with this test
method was collected based on these apparatus specifications. Any modifications may result in precision and or bias that differ from
the numbers listed in this test method.
8. Reagents and Materials
8.1 Calibration Standards—Calibration standards shall consist of unused and soot-free 15w-40 diesel motor oil adulterated with
various concentrations of sub-micron particle size, high-structure carbon black dispersed in the oil and mixed thoroughly. The
resulting soot concentration shall be determined by Thermal Gravimetric Analysis (TGA) as described in Test Method D5967. Five
standards uniformly covering a range of approximately 0 % to 12 % by mass soot are required. Precision information for Thermal
Gravimetric Analysis (TGA) in accordance with Test Method D5967 can be found in Appendix X1.
9. Sampling, Test Specimens, and Test Units
9.1 General Requirements:
9.1.1 It is recommended that in-service oil or lubricant samples to be analyzed by this test method are sampled using procedures
outlined in Practice D7418.
9.1.2 Protect samples from excessive temperatures prior to testing.
9.1.3 Do not test samples stored in leaky containers. Discard and obtain a new sample if leaks are detected.
9.2 When analyzing samples using this test method, shake the sample vigorously until the sample is adequately homogenized and
no sediment is adhered to the bottom or sides of the vessel.
10. Preparation of Apparatus
10.1 Before use, the instrument needs to be calibrated according to the procedure described in Section 11. This calibration can be
performed by the instrument manufacturer prior to delivery of the instrument to the end user.
10.2 Before analyzing samples, the instrument should be allowed to warm up for at least 1 h to ensure the analyzer is stabilized.
10.3 Before use, the instrument should be qualified by running quality control check samples consisting of a known soot
concentration as determined by Test Method D5967 that span the range that the instrument is calibrated in. These samples should
consist of at least one sample in the bottom third of the range, one sample in the middle third of the range and one sample in the
top third of the range. Apply the control charting procedures described in Practice D6299 to establish that the analyzer is
in-statistical-control. Any system that is found to be out-of-statistical-control cannot be used until the root cause(s) of
out-of-control is identified and corrected.
11. Calibration and Standardization
11.1 Calibration Standards—Refer to 8.1 for calibration standard description.
11.2 Calibration:
11.2.1 Equilibrate all samples to the temperature of the laboratory (15 °C to 27 °C) prior to analysis.
11.2.2 Allow the instrument to warm up for at least 1 h before attempting a calibration.
D7686 − 23
11.2.3 Calibration standards should be run in a randomized order.
11.2.4 Clean the HATR sample crystal of any residual oil or other contamination
...