ASTM E2412-10(2018)
(Practice)Standard Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
Standard Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
SIGNIFICANCE AND USE
5.1 Periodic sampling and analysis of lubricants have long been used as a means to determine overall machinery health. Atomic emission (AE) and atomic absorption (AA) spectroscopy are often employed for wear metal analysis (for example, Test Method D5185). A number of physical property tests complement wear metal analysis and are used to provide information on lubricant condition (for example, Test Methods D445, D2896, and D6304). Molecular analysis of lubricants and hydraulic fluids by FT-IR spectroscopy produces direct information on molecular species of interest, including additives, fluid breakdown products and external contaminants, and thus complements wear metal and other analyses used in a condition monitoring program (1,3-2).
SCOPE
1.1 This practice covers the use of FT-IR in monitoring additive depletion, contaminant buildup and base stock degradation in machinery lubricants, hydraulic fluids and other fluids used in normal machinery operation. Contaminants monitored include water, soot, ethylene glycol, fuels and incorrect oil. Oxidation, nitration and sulfonation of base stocks are monitored as evidence of degradation. The objective of this monitoring activity is to diagnose the operational condition of the machine based on fault conditions observed in the oil. Measurement and data interpretation parameters are presented to allow operators of different FT-IR spectrometers to compare results by employing the same techniques.
1.2 This practice is based on trending and distribution response analysis from mid-infrared absorption measurements. While calibration to generate physical concentration units may be possible, it is unnecessary or impractical in many cases. Warning or alarm limits (the point where maintenance action on a machine being monitored is recommended or required) can be determined through statistical analysis, history of the same or similar equipment, round robin tests or other methods in conjunction with correlation to equipment performance. These warning or alarm limits can be a fixed maximum or minimum value for comparison to a single measurement or can also be based on a rate of change of the response measured (1) .2 This practice describes distributions but does not preclude using rate-of-change warnings and alarms.
Note 1: It is not the intent of this practice 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.
1.3 Spectra and distribution profiles presented herein are for illustrative purposes only and are not to be construed as representing or establishing lubricant or machinery guidelines.
1.4 This practice is designed as a fast, simple spectroscopic check for condition monitoring of in-service lubricants and can be used to assist in the determination of general machinery health through measurement of properties observable in the mid-infrared spectrum such as water, oil oxidation, and others as noted in 1.1. The infrared data generated by this practice is typically used in conjunction with other testing methods. For example, infrared spectroscopy cannot determine wear metal levels or any other type of elemental analysis. The practice as presented is not intended for the prediction of lubricant physical properties (for example, viscosity, total base number, total acid number, etc.). This practice is designed for monitoring in-service lubricants and can aid in the determination of general machinery health and is not designed for the analysis of lubricant composition, lubricant performance or additive package formulations.
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 th...
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Designation: E2412 − 10 (Reapproved 2018)
Standard Practice for
Condition Monitoring of In-Service Lubricants by Trend
Analysis Using Fourier Transform Infrared (FT-IR)
Spectrometry
This standard is issued under the fixed designation E2412; 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.
normal, cautionary, warning or alert limits for any machinery. Such limits
1. Scope
should be established in conjunction with advice and guidance from the
1.1 This practice covers the use of FT-IR in monitoring
machinery manufacturer and maintenance group.
additive depletion, contaminant buildup and base stock degra-
1.3 Spectra and distribution profiles presented herein are for
dation in machinery lubricants, hydraulic fluids and other fluids
illustrative purposes only and are not to be construed as
used in normal machinery operation. Contaminants monitored
representing or establishing lubricant or machinery guidelines.
include water, soot, ethylene glycol, fuels and incorrect oil.
Oxidation, nitration and sulfonation of base stocks are moni- 1.4 This practice is designed as a fast, simple spectroscopic
tored as evidence of degradation. The objective of this moni- check for condition monitoring of in-service lubricants and can
toring activity is to diagnose the operational condition of the be used to assist in the determination of general machinery
machine based on fault conditions observed in the oil. Mea- health through measurement of properties observable in the
surement and data interpretation parameters are presented to mid-infrared spectrum such as water, oil oxidation, and others
allow operators of different FT-IR spectrometers to compare as noted in 1.1. The infrared data generated by this practice is
results by employing the same techniques. typically used in conjunction with other testing methods. For
example, infrared spectroscopy cannot determine wear metal
1.2 This practice is based on trending and distribution
levels or any other type of elemental analysis. The practice as
response analysis from mid-infrared absorption measurements.
presented is not intended for the prediction of lubricant
While calibration to generate physical concentration units may
physical properties (for example, viscosity, total base number,
be possible, it is unnecessary or impractical in many cases.
total acid number, etc.). This practice is designed for monitor-
Warning or alarm limits (the point where maintenance action
ing in-service lubricants and can aid in the determination of
on a machine being monitored is recommended or required)
general machinery health and is not designed for the analysis of
can be determined through statistical analysis, history of the
lubricant composition, lubricant performance or additive pack-
same or similar equipment, round robin tests or other methods
age formulations.
in conjunction with correlation to equipment performance.
These warning or alarm limits can be a fixed maximum or
1.5 The values stated in SI units are to be regarded as
minimum value for comparison to a single measurement or can
standard. No other units of measurement are included in this
also be based on a rate of change of the response measured
standard.
(1). This practice describes distributions but does not preclude
1.6 This standard does not purport to address all of the
using rate-of-change warnings and alarms.
safety concerns, if any, associated with its use. It is the
NOTE 1—It is not the intent of this practice to establish or recommend
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum
mine the applicability of regulatory limitations prior to use.
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
1.7 This international standard was developed in accor-
mittee D02.96.03 on FTIR Testing Practices and Techniques Related to In-Service
dance with internationally recognized principles on standard-
Lubricants.
Current edition approved June 1, 2018. Published June 2018. Originally
ization established in the Decision on Principles for the
approved in 2004. Last previous edition approved in 2010 as E2412 – 10.
Development of International Standards, Guides and Recom-
DOI:10.1520/E2412-10R18.
mendations issued by the World Trade Organization Technical
The boldface numbers in parentheses refer to the list of references at the end of
this standard. Barriers to Trade (TBT) Committee.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2412 − 10 (2018)
2. Referenced Documents one hour of operation will allow for the measurement of a base
3 point for later trend analysis.
2.1 ASTM Standards:
3.3.2.2 Discussion—Any subsequent addition of lubricant
D445 Test Method for Kinematic Viscosity of Transparent
(for example, topping off) may change the trending baseline,
and Opaque Liquids (and Calculation of Dynamic Viscos-
which may lead to erroneous conclusions.
ity)
D2896 Test Method for Base Number of Petroleum Products
3.3.3 machinery health, n—a qualitative expression of the
by Potentiometric Perchloric Acid Titration operational status of a machine sub-component, component or
D4057 Practice for Manual Sampling of Petroleum and
entire machine, used to communicate maintenance and opera-
Petroleum Products tional recommendations or requirements in order to continue
D5185 Test Method for Multielement Determination of
operation, schedule maintenance or take immediate mainte-
Used and Unused Lubricating Oils and Base Oils by nance action.
Inductively Coupled Plasma Atomic Emission Spectrom-
3.3.4 new oil, n—an oil taken from the original manufactur-
etry (ICP-AES)
er’s packaging, prior to being added to machinery.
D6304 Test Method for Determination of Water in Petro-
3.3.5 reference oil, n—see new oil.
leum Products, Lubricating Oils, and Additives by Cou-
lometric Karl Fischer Titration 3.3.6 trend analysis, n—as applied in this practice, moni-
E131 Terminology Relating to Molecular Spectroscopy
toring of the level and rate of change over operating time of
E168 Practices for General Techniques of Infrared Quanti- measured parameters (1).
tative Analysis
E1421 Practice for Describing and Measuring Performance
4. Summary of Practice
of Fourier Transform Mid-Infrared (FT-MIR) Spectrom-
4.1 Periodic samples are acquired from the engine or
eters: Level Zero and Level One Tests
machine being monitored. An infrared absorbance spectrum of
E1655 Practices for Infrared Multivariate Quantitative
the sample is acquired, typically covering the range of
Analysis
–1 –1
4000 cm to 550 cm , with sufficient signal-to-noise (S/N)
2.2 ISO Standard:
ratio to measure absorbance areas of interest. Exact data
ISO 13372 Condition monitoring and diagnostics of
acquisition parameters will vary depending on instrument
machines—Vocabulary
manufacturer but most systems should be able to collect an
absorbance spectrum adequate for most measurements in less
3. Terminology
than one minute. Features in the infrared spectrum indicative of
the molecular level components of interest (1,2) (that is, water,
3.1 Definitions—For definitions of terms relating to infrared
spectroscopy used in this practice, refer to Terminology E131. fuel, antifreeze, additive, degradation, and so forth) are mea-
sured and reported. Condition alerts and alarms can then be
3.2 Definitions:
triggered according to both the level and the trends from the
3.2.1 Fourier transform infrared (FT-IR) spectrometry, n—a
monitored system.
form of infrared spectrometry in which an interferogram is
obtained; this interferogram is then subjected to a Fourier
5. Significance and Use
transform to obtain an amplitude-wavenumber (or wavelength)
spectrum. E131
5.1 Periodic sampling and analysis of lubricants have long
been used as a means to determine overall machinery health.
3.3 Definitions of Terms Specific to This Standard:
Atomic emission (AE) and atomic absorption (AA) spectros-
3.3.1 condition monitoring, n—a field of technical activity
copy are often employed for wear metal analysis (for example,
in which selected physical parameters associated with an
Test Method D5185). A number of physical property tests
operating machine are periodically or continuously sensed,
complement wear metal analysis and are used to provide
measured and recorded for the interim purpose of reducing,
information on lubricant condition (for example, Test Methods
analyzing, comparing and displaying the data and information
D445, D2896, and D6304). Molecular analysis of lubricants
so obtained and for the ultimate purpose of using interim result
and hydraulic fluids by FT-IR spectroscopy produces direct
to support decisions related to the operation and maintenance
information on molecular species of interest, including
of the machine (ISO 13372).
additives, fluid breakdown products and external contaminants,
3.3.2 in-service oil, n—as applied in this practice, a lubri-
and thus complements wear metal and other analyses used in a
cating oil that is present in a machine which has been at
condition monitoring program (1,3-2).
operating temperature for at least one hour.
3.3.2.1 Discussion—Sampling a in-service oil after at least
6. Apparatus
6.1 Required Components:
6.1.1 Fourier Transform Infrared Spectrometer (FT-IR)—
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
Instrument is configured with a source, beamsplitter and
Standards volume information, refer to the standard’s Document Summary page on
detector to adequately cover the mid-infrared range of
the ASTM website.
–1 –1
4 4000 cm to 550 cm . Most work has been done on systems
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. using a room temperature deuterated triglycine sulfate (DTGS)
E2412 − 10 (2018)
detector, air-cooled source and Germanium coating on Potas- pump types, tubing and transmission cells for this type of
sium Bromide (Ge/KBr) beamsplitter. Alternate source, beam- application. It should be noted that non-homogeneity might
splitter and detector combinations covering this range are occur if the oils are left standing for too long.
commercially available but have not been investigated for use 6.2.2 Filter—The use of a particulate filter (for example,
in this practice. Other detectors may be suitable but should be 0.090 mm) to trap large particles is strongly recommended to
used with caution. In particular, liquid nitrogen cooled Mer- prevent cell clogging when a pumping system is used. If a
cury Cadmium Telluride (MCT) detectors are known to exhibit particulate filter is not used, the cell should be back-flushed
significant nonlinearities. regularly to prevent clogging.
6.2.3 Sealed Sample Compartment—The system configura-
6.1.2 Infrared Liquid Transmission Sampling Cell—
tion should be consistent with preventing harmful, flammable
Sampling cells can be constructed of zinc selenide (ZnSe),
or explosive vapors from reaching the IR source.
barium fluoride (BaF ), potassium bromide (KBr), or other
6.2.4 Hydrocarbon Leak Alarm—When a sample pumping
suitable window material, with a pathlength of 0.1 mm
system is used, an independent flammable vapor sensor and
(100 µm), parallel (<0.5° variance) cell spacer. Acceptable
alarm system should be used to alert the operator when a leak
pathlength ranges are from 0.080 mm to 0.120 mm. Outside
occurs in the tubing, connectors or transmission cell. This
this range, poor sensitivity or data nonlinearity can occur. For
alarm system is strongly recommended when a pumping
the data provided in this document, the cells used were ZnSe,
–1
system is used to pump samples and wash solvents into an
NaCl, or KBr as the measurements ranged from 4000 cm to
–1
enclosed area.
700 cm . Some cell material information is given below.
6.2.5 Check Fluid—A check fluid or quality control fluid
Transmission
Material Comments
–1
Range, cm can be analyzed as needed for individual laboratory quality
ZnSe see 6.1.2.1 4000 – 550
control and procedure issues and for comparison to other
KBr susceptible to water damage 4000 – 400
laboratories. One IR manufacturer has used heptane. A check
NaCl susceptible to water damage 4000 – 650
BaF ammonium salts can damage 4000 – 850
sample should be a material that provides consistent results
CaF ammonium salts can damage 4000 – 1100
using the methods presented in the annexes to this practice. The
Results should be corrected to 0.100 mm pathlength to
purpose of this quality control fluid is to verify proper
account for cell path variation and improve data comparison to operation of the FT-IR spectrometer/transmission cell
other instruments using this practice.
combinations, as well as any associated sample introduction
and cleaning hardware.
6.1.2.1 Due to the large refractive index change when the
infrared beam passes from air into the ZnSe windows, fringe
7. Sampling and Sample Handling
reduction is necessary to provide consistent results. Fringe
reduction can be achieved electronically, optically or mechani-
7.1 Sample Acquisition—The objective of sampling is to
cally for ZnSe cells. For further explanation, see Appendix X1.
obtain a test specimen that is representative of the entire
Care should be taken in selecting window materials to ensure
quantity. Thus, laboratory samples should be taken in accor-
that the desired parameters can be measured within the
dance with the instructions in Practice D4057.
transmission region of that material and compatibility with the
7.2 Sample Preparation—No sample preparation is re-
specific application; for example, salt windows (KBr, NaCl,
quired. Laboratory samples should be shaken or agitated to
KCl) can be used and may not require fringe correction but are
ensure a representative sample is taken from the bottle.
susceptible to damage from water contamination in the oil.
Coates and Setti (3) have noted that oil nitration products can
8. Instrumentation Preparation
react with salt windows, depositing compounds that are ob-
served in later samples.
8.1 Spectral Acquisition Parameters:
–1
6.1.3 Cell Flushing/Cleaning Solvent—The ideal solvent to 8.1.1 Spectral Resolution—8 cm or better (lower numeric
flush the cell between samples to mini
...
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: E2412 − 10 E2412 − 10 (Reapproved 2018)
Standard Practice for
Condition Monitoring of In-Service Lubricants by Trend
Analysis Using Fourier Transform Infrared (FT-IR)
Spectrometry
This standard is issued under the fixed designation E2412; 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 practice covers the use of FT-IR in monitoring additive depletion, contaminant buildup and base stock degradation in
machinery lubricants, hydraulic fluids and other fluids used in normal machinery operation. Contaminants monitored include water,
soot, ethylene glycol, fuels and incorrect oil. Oxidation, nitration and sulfonation of base stocks are monitored as evidence of
degradation. The objective of this monitoring activity is to diagnose the operational condition of the machine based on fault
conditions observed in the oil. Measurement and data interpretation parameters are presented to allow operators of different FT-IR
spectrometers to compare results by employing the same techniques.
1.2 This practice is based on trending and distribution response analysis from mid-infrared absorption measurements. While
calibration to generate physical concentration units may be possible, it is unnecessary or impractical in many cases. Warning or
alarm limits (the point where maintenance action on a machine being monitored is recommended or required) can be determined
through statistical analysis, history of the same or similar equipment, round robin tests or other methods in conjunction with
correlation to equipment performance. These warning or alarm limits can be a fixed maximum or minimum value for comparison
to a single measurement or can also be based on a rate of change of the response measured (1). This practice describes
distributions but does not preclude using rate-of-change warnings and alarms.
NOTE 1—It is not the intent of this practice 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.
1.3 Spectra and distribution profiles presented herein are for illustrative purposes only and are not to be construed as
representing or establishing lubricant or machinery guidelines.
1.4 This practice is designed as a fast, simple spectroscopic check for condition monitoring of in-service lubricants and can be
used to assist in the determination of general machinery health through measurement of properties observable in the mid-infrared
spectrum such as water, oil oxidation, and others as noted in 1.1. The infrared data generated by this practice is typically used in
conjunction with other testing methods. For example, infrared spectroscopy cannot determine wear metal levels or any other type
of elemental analysis. The practice as presented is not intended for the prediction of lubricant physical properties (for example,
viscosity, total base number, total acid number, etc.). This practice is designed for monitoring in-service lubricants and can aid in
the determination of general machinery health and is not designed for the analysis of lubricant composition, lubricant performance
or additive package formulations.
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 safety, health, and healthenvironmental 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 practice 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 May 1, 2010June 1, 2018. Published June 2010June 2018. Originally approved in 2004. Last previous edition approved in 20042010 as
E2412–04.E2412 – 10. DOI:10.1520/E2412-10.DOI:10.1520/E2412-10R18.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2412 − 10 (2018)
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
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D5185 Test Method for Multielement Determination of Used and Unused Lubricating Oils and Base Oils by Inductively
Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
D6304 Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl
Fischer Titration
E131 Terminology Relating to Molecular Spectroscopy
E168 Practices for General Techniques of Infrared Quantitative Analysis
E1421 Practice for Describing and Measuring Performance of Fourier Transform Mid-Infrared (FT-MIR) Spectrometers: Level
Zero and Level One Tests
E1655 Practices for Infrared Multivariate Quantitative Analysis
2.2 ISO Standard:
ISO 13372 Condition monitoring and diagnostics of machines -- Vocabularymachines—Vocabulary
3. Terminology
3.1 Definitions—For definitions of terms relating to infrared spectroscopy used in this practice, refer to Terminology E131.
3.2 Definitions:
3.2.1 Fourier transform infrared (FT-IR) spectrometry, n—a form of infrared spectrometry in which an interferogram is
obtained; this interferogram is then subjected to a Fourier transform to obtain an amplitude-wavenumber (or wavelength) spectrum.
E131
3.3 Definitions of Terms Specific to This Standard:
3.3.1 condition monitoring, n—a field of technical activity in which selected physical parameters associated with an operating
machine are periodically or continuously sensed, measured and recorded for the interim purpose of reducing, analyzing, comparing
and displaying the data and information so obtained and for the ultimate purpose of using interim result to support decisions related
to the operation and maintenance of the machine (ISO 13372).
3.3.2 in-service oil, n—as applied in this practice, a lubricating oil that is present in a machine which has been at operating
temperature for at least one hour.
3.3.2.1 Discussion—
Sampling a in-service oil after at least one hour of operation will allow for the measurement of a base point for later trend analysis.
3.3.2.2 Discussion—
Any subsequent addition of lubricant (for example, topping off) may change the trending baseline, which may lead to erroneous
conclusions.
3.3.3 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.
3.3.4 new oil, n—an oil taken from the original manufacturer’s packaging, prior to being added to machinery.
3.3.5 reference oil, n—see new oil.
3.3.6 trend analysis, n—as applied in this practice, monitoring of the level and rate of change over operating time of measured
parameters (1).
4. Summary of Practice
4.1 Periodic samples are acquired from the engine or machine being monitored. An infrared absorbance spectrum of the sample
–1 -1–1
is acquired, typically covering the range of 40004000 cm to 550 cm550 cm , with sufficient signal-to-noise (S/N) ratio to
measure absorbance areas of interest. Exact data acquisition parameters will vary depending on instrument manufacturer but most
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.
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
www.iso.org.American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
E2412 − 10 (2018)
systems should be able to collect an absorbance spectrum adequate for most measurements in less than one minute. Features in
the infrared spectrum indicative of the molecular level components of interest (1,2) (that is, water, fuel, antifreeze, additive,
degradation, and so forth) are measured and reported. Condition alerts and alarms can then be triggered according to both the level
and the trends from the monitored system.
5. Significance and Use
5.1 Periodic sampling and analysis of lubricants have long been used as a means to determine overall machinery health. Atomic
emission (AE) and atomic absorption (AA) spectroscopy are often employed for wear metal analysis (for example, Test Method
D5185). A number of physical property tests complement wear metal analysis and are used to provide information on lubricant
condition (for example, Test Methods D445, D2896, and D6304). Molecular analysis of lubricants and hydraulic fluids by FT-IR
spectroscopy produces direct information on molecular species of interest, including additives, fluid breakdown products and
external contaminants, and thus complements wear metal and other analyses used in a condition monitoring program (1,3-2).
6. Apparatus
6.1 Required Components:
6.1.1 Fourier Transform Infrared Spectrometer (FT-IR)—Instrument is configured with a source, beamsplitter and detector to
-1 –1 -1–1
adequately cover the mid-infrared range of 4000 cm4000 cm to 550 cm550 cm . Most work has been done on systems using
a room temperature deuterated triglycine sulfate (DTGS) detector, air-cooled source and Germanium coating on Potassium
Bromide (Ge/KBr) beamsplitter. Alternate source, beamsplitter and detector combinations covering this range are commercially
available but have not been investigated for use in this practice. Other detectors may be suitable but should be used with caution.
In particular, liquid nitrogen cooled Mercury Cadmium Telluride (MCT) detectors are known to exhibit significant nonlinearities.
6.1.2 Infrared Liquid Transmission Sampling Cell—Sampling cells can be constructed of zinc selenide (ZnSe), barium fluoride
(BaF ), potassium bromide (KBr), or other suitable window material, with a pathlength of 0.1 mm (100 μm), 0.1 mm (100 μm),
parallel (<0.5° variance) cell spacer. Acceptable pathlength ranges are from 0.0800.080 mm to 0.120 mm. 0.120 mm. Outside this
range, poor sensitivity or data nonlinearity can occur. For the data provided in this document, the cells used were ZnSe, NaCl, or
-1–1 -1–1
KBr as the measurements ranged from 4000 cm4000 cm to 700 cm700 cm . Some cell material information is given below.
Transmission
Material Comments
-1–1
Range, cm
ZnSe see 6.1.2.1 4000 – 550
KBr susceptible to water damage 4000 – 400
NaCl susceptible to water damage 4000 – 650
BaF ammonium salts can damage 4000 – 850
CaF ammonium salts can damage 4000 – 1100
Results should be corrected to 0.100 mm 0.100 mm pathlength to account for cell path variation and improve data comparison
to other instruments using this practice.
6.1.2.1 Due to the large refractive index change when the infrared beam passes from air into the ZnSe windows, fringe reduction
is necessary to provide consistent results. Fringe reduction can be achieved electronically, optically or mechanically for ZnSe cells.
For further explanation, see Appendix X1. Care should be taken in selecting window materials to ensure that the desired parameters
can be measured within the transmission region of that material and compatibility with the specific application; for example, salt
windows (KBr, NaCl, KCl) can be used and may not require fringe correction but are susceptible to damage from water
contamination in the oil. Coates and Setti (3) have noted that oil nitration products can react with salt windows, depositing
compounds that are observed in later samples.
6.1.3 Cell Flushing/Cleaning Solvent—The ideal solvent to flush the cell between samples to minimize carryover should have
no significant absorption in the condition monitoring areas of interest and should dry quickly when air is pumped through the
system. Typical wash solvents used for common petroleum and some synthetic lubricants are technical grade, light aliphatic
hydrocarbons such as heptane or cyclohexane. Other solvents may be required for more specialized synthetic lubricants. Health
and safety issues on using, storing, and disposing of these solvents will not be covered here. Local regulations and Material Safety
Data Sheets (MSDS) should be consulted.
6.2 Optional Components:
6.2.1 Sample Pumping System—A pumping system capable of transporting the sample to the transmission cell, emptying the cell
and flushing the cell between samples may be used. Many commercial vendors offer various configurations of pump types, tubing
and transmission cells for this type of application. It should be noted that non-homogeneity might occur if the oils are left standing
for too long.
6.2.2 Filter—The use of a particulate filter (for example, 0.090 mm) 0.090 mm) to trap large particles is strongly recommended
to prevent cell clogging when a pumping system is used. If a particulate filter is not used, the cell should be back–flushedback-
flushed regularly to prevent clogging.
6.2.3 Sealed Sample Compartment—The system configuration should be consistent with preventing harmful, flammable or
explosive vapors from reaching the IR source.
E2412 − 10 (2018)
...
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