ASTM E2412-23a

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: E2412 − 23a
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* 1.3 Spectra and distribution profiles presented herein are for
illustrative purposes only and are not to be construed as
1.1 This practice covers the use of FT-IR in monitoring
representing or establishing lubricant or machinery guidelines.
additive depletion, contaminant buildup and base stock degra-
dation in machinery lubricants, hydraulic fluids and other fluids
1.4 This practice is designed as a fast, simple spectroscopic
used in normal machinery operation. Contaminants monitored
check for condition monitoring of in-service lubricants and can
include water, soot, ethylene glycol, fuels and incorrect oil.
be used to assist in the determination of general machinery
Oxidation, nitration and sulfonation of base stocks are moni-
health through measurement of properties observable in the
tored as evidence of degradation. The objective of this moni-
mid-infrared spectrum such as water, oil oxidation, and others
toring activity is to diagnose the operational condition of the
as noted in 1.1. The infrared data generated by this practice is
machine based on fault conditions observed in the oil. Mea-
typically used in conjunction with other testing methods. For
surement and data interpretation parameters are presented to
example, infrared spectroscopy cannot determine wear metal
allow operators of different FT-IR spectrometers to compare
levels or any other type of elemental analysis. The practice as
results by employing the same techniques.
presented is not intended for the prediction of lubricant
physical properties (for example, viscosity, total base number,
1.2 This practice is based on trending and distribution
total acid number, etc.). This practice is designed for monitor-
response analysis from mid-infrared absorption measurements.
ing in-service lubricants and can aid in the determination of
While calibration to generate physical concentration units may
general machinery health and is not designed for the analysis of
be possible, it is unnecessary or impractical in many cases.
lubricant composition, lubricant performance or additive pack-
Warning or alarm limits (the point where maintenance action
age formulations.
on a machine being monitored is recommended or required)
can be determined through statistical analysis, history of the
1.5 The values stated in SI units are to be regarded as
same or similar equipment, round robin tests or other methods
standard. No other units of measurement are included in this
in conjunction with correlation to equipment performance.
standard.
These warning or alarm limits can be a fixed maximum or
minimum value for comparison to a single measurement or can
1.6 This standard does not purport to address all of the
also be based on a rate of change of the response measured
safety concerns, if any, associated with its use. It is the
(1). This practice describes distributions but does not preclude responsibility of the user of this standard to establish appro-
using rate-of-change warnings and alarms.
priate safety, health, and environmental practices and deter-
NOTE 1—It is not the intent of this practice to establish or recommend mine the applicability of regulatory limitations prior to use.
normal, cautionary, warning or alert limits for any machinery. Such limits
1.7 This international standard was developed in accor-
should be established in conjunction with advice and guidance from the
dance with internationally recognized principles on standard-
machinery manufacturer and maintenance group.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum
Barriers to Trade (TBT) Committee.
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
mittee D02.96.03 on FTIR Testing Practices and Techniques Related to In-Service
Lubricants.
Current edition approved Nov. 1, 2023. Published November 2023. Originally
approved in 2004. Last previous edition approved in 2023 as E2412 – 23.
DOI:10.1520/E2412-23A.
The boldface numbers in parentheses refer to the 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
E2412 − 23a
2. Referenced Documents 3.2.2 in-service oil, n—as applied in this practice, a lubri-
3 cating oil that is present in a machine which has been at
2.1 ASTM Standards:
operating temperature for at least one hour.
D445 Test Method for Kinematic Viscosity of Transparent
3.2.2.1 Discussion—Sampling a in-service oil after at least
and Opaque Liquids (and Calculation of Dynamic Viscos-
one hour of operation will allow for the measurement of a base
ity)
point for later trend analysis.
D2896 Test Method for Base Number of Petroleum Products
3.2.2.2 Discussion—Any subsequent addition of lubricant
by Potentiometric Perchloric Acid Titration
(for example, topping off) may change the trending baseline,
D4057 Practice for Manual Sampling of Petroleum and
which may lead to erroneous conclusions.
Petroleum Products
3.2.3 machinery health, n—a qualitative expression of the
D4175 Terminology Relating to Petroleum Products, Liquid
operational status of a machine sub-component, component or
Fuels, and Lubricants
entire machine, used to communicate maintenance and opera-
D5185 Test Method for Multielement Determination of
tional recommendations or requirements in order to continue
Used and Unused Lubricating Oils and Base Oils by
operation, schedule maintenance or take immediate mainte-
Inductively Coupled Plasma Atomic Emission Spectrom-
nance action.
etry (ICP-AES)
D6304 Test Method for Determination of Water in Petro-
3.2.4 new oil, n—an oil taken from the original manufactur-
leum Products, Lubricating Oils, and Additives by Cou-
er’s packaging, prior to being added to machinery.
lometric Karl Fischer Titration
3.2.5 reference oil, n—see new oil.
D8321 Practice for Development and Validation of Multi-
3.2.6 trend analysis, n—as applied in this practice, moni-
variate Analyses for Use in Predicting Properties of
toring of the level and rate of change over operating time of
Petroleum Products, Liquid Fuels, and Lubricants based
measured parameters (1).
on Spectroscopic Measurements
E131 Terminology Relating to Molecular Spectroscopy
4. Summary of Practice
E168 Practices for General Techniques of Infrared Quanti-
4.1 Periodic samples are acquired from the engine or
tative Analysis
E1421 Practice for Describing and Measuring Performance machine being monitored. An infrared absorbance spectrum of
the sample is acquired, typically covering the range of
of Fourier Transform Mid-Infrared (FT-MIR) Spectrom-
–1 –1
eters: Level Zero and Level One Tests 4000 cm to 550 cm , with sufficient signal-to-noise (S/N)
ratio to measure absorbance areas of interest. Exact data
2.2 ISO Standard:
ISO 13372 Condition monitoring and diagnostics of acquisition parameters will vary depending on instrument
manufacturer but most systems should be able to collect an
machines—Vocabulary
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:
3.1.1 For definitions of terms used in this practice, refer to fuel, antifreeze, additive, degradation, and so forth) are mea-
sured and reported. Condition alerts and alarms can then be
Terminology D4175.
3.1.2 For definitions of terms relating to infrared spectros- triggered according to both the level and the trends from the
monitored system.
copy used in this practice, refer to Terminology E131.
3.1.3 Fourier transform infrared (FT-IR) spectrometry, n—a
5. Significance and Use
form of infrared spectrometry in which an interferogram is
obtained; this interferogram is then subjected to a Fourier
5.1 Periodic sampling and analysis of lubricants have long
transform to obtain an amplitude-wavenumber (or wavelength)
been used as a means to determine overall machinery health.
spectrum. E131
Atomic emission (AE) and atomic absorption (AA) spectros-
copy are often employed for wear metal analysis (for example,
3.2 Definitions of Terms Specific to This Standard:
Test Method D5185). A number of physical property tests
3.2.1 condition monitoring, n—a field of technical activity
complement wear metal analysis and are used to provide
in which selected physical parameters associated with an
information on lubricant condition (for example, Test Methods
operating machine are periodically or continuously sensed,
D445, D2896, and D6304). Molecular analysis of lubricants
measured and recorded for the interim purpose of reducing,
and hydraulic fluids by FT-IR spectroscopy produces direct
analyzing, comparing and displaying the data and information
information on molecular species of interest, including
so obtained and for the ultimate purpose of using interim result
additives, fluid breakdown products and external contaminants,
to support decisions related to the operation and maintenance
and thus complements wear metal and other analyses used in a
of the machine (ISO 13372).
condition monitoring program (1, 2-6).
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6. Apparatus
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
6.1 Required Components:
the ASTM website.
6.1.1 Fourier Transform Infrared Spectrometer (FT-IR)—
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. Instrument is configured with a source, beamsplitter and
E2412 − 23a
detector to adequately cover the mid-infrared range of 6.2.1 Sample Pumping System—A pumping system capable
–1 –1
4000 cm to 550 cm . Most work has been done on systems of transporting the sample to the transmission cell, emptying
the cell and flushing the cell between samples may be used.
using a room temperature deuterated triglycine sulfate (DTGS)
Many commercial vendors offer various configurations of
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.
6.1.2 Infrared Liquid Transmission Sampling Cell—
6.2.3 Sealed Sample Compartment—The system configura-
Sampling cells can be constructed of zinc selenide (ZnSe),
tion should be consistent with preventing harmful, flammable
barium fluoride (BaF ), potassium bromide (KBr), or other
or explosive vapors from reaching the IR source.
suitable window material, with a pathlength of 0.1 mm
6.2.4 Hydrocarbon Leak Alarm—When a sample pumping
(100 μm), parallel (<0.5° variance) cell spacer. Acceptable
system is used, an independent flammable vapor sensor and
pathlength ranges are from 0.080 mm to 0.120 mm. Outside
alarm system should be used to alert the operator when a leak
this range, poor sensitivity or data nonlinearity can occur. For
occurs in the tubing, connectors or transmission cell. This
the data provided in this document, the cells used were ZnSe,
alarm system is strongly recommended when a pumping
–1
NaCl, or KBr as the measurements ranged from 4000 cm to
system is used to pump samples and wash solvents into an
–1
700 cm . Some cell material information is given below.
enclosed area.
Transmission
6.2.5 Check Fluid—A check fluid or quality control fluid
Material Comments
–1
Range, cm
can be analyzed as needed for individual laboratory quality
ZnSe see 6.1.2.1 4000 – 550
KBr susceptible to water damage 4000 – 400
control and procedure issues and for comparison to other
NaCl susceptible to water damage 4000 – 650
laboratories. One IR manufacturer has used heptane. A check
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
6.1.2.1 Due to the large refractive index change when the
and cleaning hardware.
infrared beam passes from air into the ZnSe windows, fringe
reduction is necessary to provide consistent results. Fringe
7. Sampling and Sample Handling
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-
8.1 Spectral Acquisition Parameters:
served in later samples.
–1
8.1.1 Spectral Resolution—8 cm or better (lower numeric
6.1.3 Cell Flushing/Cleaning Solvent—The ideal solvent to
value).
flush the cell between samples to minimize carryover should
–1
8.1.2 Data Point Spacing Resolution—4 cm or better
have no significant absorption in the condition monitoring
(lower numeric value).
areas of interest and should dry quickly when air is pumped
–1 –1
8.1.3 Typical Range—4000 cm to 550 cm (see 6.1.2).
through the system. Typical wash solvents used for common
8.1.4 Spectral Format—Absorbance as a function of wav-
petroleum and some synthetic lubricants are technical grade,
enumber.
light aliphatic hydrocarbons such as heptane or cyclohexane.
8.1.5 Other Optical, Electronic Filtering and Interferogram
Other solvents may be required for more specialized synthetic
Computational Parameters—These parameters should be as
lubricants. Health and safety issues on using, storing, and
recommended by the manufacturer or as determined necessary
disposing of these solvents will not be covered here. Local
for adequate measurement quality. Individual parameters and
regulations and Material Safety Data Sheets (MSDS) should be
settings will vary depending on instrument manufacturer but
consulted.
most FT-IR spectrometers should be able to collect an adequate
6.2 Optional Components: spectrum in less than one minute.
E2412 − 23a
NOTE 2—Identical scanning acquisition parameters should be used for
the cell being used. The manufacturer’s suggestions and
all samples to be trended.
recommendations should be considered.
8.2 Background Collection: 9.2.1 Petroleum based lubricants have their maximum ab-
–1 –1
8.2.1 The single-beam background collection (empty sys- sorbance in the 3000 cm to 2800 cm range (or transmit-
tem reference scanned and stored on an FT-IR spectrometer) tance value close to 0 %T).
should be performed frequently enough such that ambient 9.2.2 Ester based lubricants have their maximum absor-
–1 –1
changes in atmospheric water vapor levels and other changing
bance in the 1390 cm to 1090 cm range (or transmittance
ambient conditions do not significantly affect the sample value close to 0 %T).
results (see Practice E1421). The frequency of background
9.3 Sample System Cleaning and Checks—To ensure the
checks should be determined by the individual laboratory
minimum amount of sample cross-contamination or sample
conditions and sampling technique; for example, at the
carry-over, either a minimum volume of the next sample can be
completion of each run when an autosampler is used.
flushed, or a volatile solvent can be flushed through the cell and
8.2.2 Note that changing water vapor levels will have the
the cell dried. If the cell is dried, the amount of absorbance
strongest effect, as water vapor is a strong infrared absorber. A
from either the previous sample or residual wash solvent in the
water vapor check may be included in the software to monitor
sample cell can be checked. This check is performed by the
the intensity of the water vapor in the single-beam background
same spectral analysis operation as described above. The
spectrum. For example, the water vapor bands superimposed
maximum absorbance intensity should be below a preset
–1 –1
on the single-beam spectrum at 1540 cm , 1559 cm , and
threshold in the monitoring region (that is, CH stretch in
–1
1652 cm may be measured relative to the average of baseline
petroleum based fluids). For most petroleum and synthetic
–1 –1
points at 1609 cm to 1582 cm . Acceptable limits for opera-
lubricants and wash solvents, this intensity will be less than 0.2
tion can be set; for example, measured peaks due to water
absorbance units. The optimal threshold will depend upon the
vapor superimposed on the single-beam background should not
specific system configuration, in that some systems are de-
be more than 10 % of the single-beam intensity.
signed to “push-out” the residual oil sample and wash solvent
8.2.3 Most of the research and development work used in
with the next sample. The manufacturer’s suggestions and
the development of this practice used a background collection
recommendations should be considered.
at least every 2 h. Individual parameters and settings will vary
9.4 Data Processing—All spectra will be processed in units
depending on instrument manufacturer but most FT-IR spec-
of absorbance as a function of wavenumber. Calculated data
trometers should be able to collect an adequate spectrum in less
must be corrected to the reference pathlength of 0.100 mm
than one minute.
prior to reporting to account for cell pathlength variation that
8.3 Cell Pathlength Check—A cell pathlength check is
will be seen in commercially available cells. Any other spectral
needed to verify the pathlength consistency of the cell. Results
data treatment should occur prior to calculating results from the
are referenced to 0.100 mm as mentioned in 6.1.2. This check
spectrum.
is particularly important for water-soluble salt cell windows
9.4.1 Spectral data processing results can be trended di-
(for example, KBr). For systems using a fixed flow cell, the
rectly from the in-service oil spectrum (direct trending). The
check can be performed at the same time as the background
only spectral data treatment is the correction of the spectrum or
collection. Different instrument manufacturers may use differ-
results to the 0.100 mm reference pathlength and the applica-
ent techniques for cell pathlength checks that may require the
tion of fringe reduction algorithms to the spectrum, if required.
use of a reference or calibration fluid(s). A fringe-based method
9.4.2 Spectral data processing results can also be obtained
for determining cell pathlength is discussed in the appendix.
by spectral subtraction processing, which requires a reference
Manufacturers’ instructions and recommendations should be
spectrum (spectral subtraction). Where spectral subtraction is
considered.
used, processing of results is done from the difference spec-
trum that is generated by subtracting the appropriate new oil
9. Procedures, Calculation, and Reporting
reference spectrum from the spectrum of the in-service oil
9.1 Sample Introduction—A representative sample is intro-
sample. The in-service oil spectrum and new oil reference
duced into the infrared transmission cell, either manually or by
spectrum must both be corrected to the reference pathlength of
an automatic pumping system. Autosamplers that hold a
0.100 mm prior to subtraction and a 1:1 subtraction factor used.
variety of oil sample container sizes are available from several
The subtracted spectral results can be trended over time and
manufacturers.
treated in a manner similar to those collected using the direct
infrared trending method.
9.2 Sample Integrity Check—To ensure accurate and con-
sistent results, the infrared spectrum of the sample should be 9.4.2.1 The most commonly used reference is a sample of
new oil. If possible, the new oil should be from the same lot
checked to verify that the cell is completely filled and that air
bubbles passing through the cell during data collection are not and drum as the in-service oil. An alternate approach that might
yield a more representative reference would be to take a sample
affecting the results. Multiple, automatic, computerized inter-
pretation methods exist for this procedure. A sample integrity of oil one hour after the oil has reached operating temperatures.
check based on measurement of the absorbance intensity over 9.4.3 Post-analysis data treatment can use simple multipli-
–1 –1
the wavenumber range from 3000 cm to 1090 cm is suit- ers and other scaling techniques; for example, “value × 100” at
able for multiple lubricant types. The exact absorbance inten- the request of maintenance personnel for ease in evaluation and
sity will depend on the spectral resolution and the pathlength of presentation (see Annex A1).
E2412 − 23a
9.5 Spectral Analysis of Sample Data—Selected spectral
regions containing information relevant to condition monitor-
ing are measured and reported. The regions analyzed are
specific to different lubricating fluid types. New oil sample
parameters can be used as the point from which to trend when
initially implementing an analysis process for a lubricant type.
Statistical analysis shown in the annexes also provides ex-
amples. Details of the spectral analysis process can be found in
the annexes to this Practice.
10. Effects of Oil Formulation
10.1 Differences in oil formulations can affect the results
reported for the various measurements described in Annex A1.
For example, Fig. 1 shows spectra of four 10W-30 oils in the
carbonyl region where oxidation is measured for petroleum
lubricants. In this example, absorbances for carbonyl-
containing additives in these unused oil formulations contrib-
ute nearly a factor of 2 difference in the oxidation result
measured by direct trending.
10.2 Results should be:
10.2.1 Interpreted relative to values measured for unused oil
of the same formulation, or
FIG. 1 Example of Carbonyl Containing Components in New Oil
10.2.2 Trended directly from the component sample history.
Formulations
10.3 Distribution profiles for results for different oil formu-
lations should typically not be combined unless justified by
field experience in condition monitoring programs.
fuel; glycol; infrared; IR; lubricating oils; nitration; oxidation;
11. Keywords
petroleum based extreme pressure lubricants; petroleum lubri-
11.1 additive packages; base stock degradation; condition cants; polyol ester synthetic lubricants; soot; sulfates; trend
monitoring; contamination; Fourier transform infrared; FT-IR; analysis; water
ANNEXES
(Mandatory Information)
A1. MEASUREMENT OF MOLECULAR PARAMETERS IN VARIOUS SYSTEMS—DIRECT TRENDING
A1.1 This annex does not purport to discuss all lubricant gasoline is also possible but not as widely applied, as com-
types. Measurement parameters for petroleum lubricants (for paratively few gasoline engines are enrolled in condition
example, crankcase), extreme pressure petroleum lubricants monitoring programs. In addition, monitoring of the zinc
dialkyldithiophosphate (ZDDP) based antiwear component of
and polyol esters are presented. As data becomes available,
the additive package is also possible. The most common FT-IR
other lubricant types can be added to the annex.
condition monitoring parameters for crankcase engines are
NOTE A1.1—It is not the intent of this practice to establish or
presented in Table A1.1, with some spectral measurement
recommend normal, cautionary, warning or alert limits for any machinery
or fluids. Such limits should be established in conjunction with advice and examples presented as a guide in using band areas. Throughout
guidance from the machinery manufacturer and maintenance group.
these examples, the use of integrated band area is preferred as
noted in Practice E168 because it has been “found to be more
A1.2 Petroleum Lubricants (Typically Diesel Engines)—
accurate than peak-height measurements because one is, in
Monitoring of diesel crankcase oil is one of the most common
effect, averaging multipoint data.”
applications of lubricant condition monitoring. Condition
monitoring in these systems is divided into contaminant A1.2.1 Water:
monitoring (typically water, soot, fuel, glycol) and oil degra-
A1.2.1.1 Water contamination is monitored in diesel crank-
dation monitoring (typically oxidation and nitration). Sulfation
case lubricants by measuring the hydrogen-bonded OH stretch
degradation products may arise from lubricant component region given in Table A1.1. An example of varying levels of
breakdown but commonly arise from the by-products of
water contamination is shown in Fig. A1.1. In the following
sulfur–containing diesel fuels. Measuring contamination from examples (except soot) the infrared spectrum is shaded down to
E2412 − 23a
the described baseline, giving a visual example of how the vary. Work is currently active on other IR measurement areas
integrated absorbance area is measured. Measurement of these and techniques. The measurement listed can be used as a
band areas by computer assisted techniques is common in most guideline but is not intended to be the only infrared based fuel
infrared manufacturers’ software packages. For the water contamination measurement. An independent test, such as
measurement in crankcase oils, the area under the curve viscosity change, flash point, or gas chromatography can be
–1 –1
between 3500 cm and 3150 cm is shaded, showing an used to confirm an indication of fuel presence in the FT-IR
example of the measurement described above. spectrum of the oil.
A1.2.1.2 Water Interferences—High soot levels (~10 % w/w
A1.2.5 Glycol Antifreeze Contamination:
solids) may interfere with water measurements in diesel
A1.2.5.1 Glycol contamination is monitored in diesel crank-
engines, but interference has not been seen until the soot limit
case lubricants by measuring the carbon-oxygen stretch region
has been exceeded (that is, > 3 % to 5 % w/w solids). As a
as noted in Table A1.1. Spectral characteristics of glycol
condition limit (soot) has already triggered, action should be
contamination are shown in Fig. A1.6.
taken irrespective of water. Exact quantitative measurement of
A1.2.5.2 Ethylene glycol will interfere with the ability to
soot is difficult (that is, % w ⁄w) due to multiple infrared
accurately quantify water level when present since it also
contributing factors as well as the many different soot mea-
contains hydroxyl groups. However, the converse is not true
surement methods available.
since glycol has other spectral features that are used for
A1.2.2 Soot:
detection and quantification. Therefore, when glycol is present,
A1.2.2.1 Soot loading is measured from the baseline offset
water can be detected but not reliably quantified using FT-IR
–1
at 2000 cm as described in Table A1.1. Fig. A1.2 shows some
spectroscopy. This is not considered a problem because of the
examples of spectra showing low, intermediate, high and very
greater significance the presence of glycol has to engine
high soot loading levels (increasing levels from 1 through 5).
operation. As with fuel, the presence of glycol can be con-
A1.2.2.2 Soot Interference—High water levels have been
firmed by gas chromatography or a colorimetric test, or more
observed to interfere with the measurement of soot in internal
commonly, corroborated using elemental analysis results for
combustion engine crankcases. However, this interference does
sodium and boron.
not become significant until the water level is on the order of
A1.3 Extreme Pressure (EP) Fluids (Typically Petroleum
>5 % (50 000 ppm), levels which will immediately condemn
Gear or Hydraulic Fluids):
the lubricant and require immediate maintenance action irre-
spective of any other indicators.
A1.3.1 In addition to the above crankcase oil analysis,
condition monitoring of gear and hydraulic oil is also widely
A1.2.3 Oxidation, Nitration and Sulfation:
applied. In these systems, the most common parameters
A1.2.3.1 Unlike the previous examples, oxidation, nitration
measured are water contamination and oxidative breakdown of
and sulfation breakdown products in crankcase oils cannot be
the oil, which are presented in Table A1.2.
easily quantified by comparison to pure prepared standards.
Here, there are a large number of different oxidation and
A1.3.2 Water:
nitration compounds that can be produced and gradually build
A1.3.2.1 As water is the most common contaminant in
up in the oil. Fig. A1.3 shows the measurement areas for
crankcase oils, it is also the most common contaminant in
oxidation and nitration product buildup monitoring, with the
gearboxes and hydraulic systems. In these systems, unlike the
sulfation region highlighted in Fig. A1.4.
crankcase oils, however, interactions between water and the EP
A1.2.3.2 Oxidation, Nitration and Sulfation
additives alter the infrared response, and thus water is mea-
Interferences—As in the soot measurement, very high water
sured differently than in the crankcase lubricants. Fig. A1.7
levels can generate false positives for oxidation and nitration.
demonstrates this different response of water. Water contami-
However, water levels of this magnitude will immediately
nation is manifested as a general, horizontal baseline offset of
condemn the lubricant. Very high (>5 %) glycol levels in a
the entire infrared spectrum. Here, the integrated area for the
crankcase oil may start interfering with sulfation measurement,
spectrum representing 3000 ppm (0.3 %) water is shaded.
but again contaminant levels of this magnitude would dictate
While this measurement becomes the principal water measure-
immediate maintenance action. Various additive packages,
ment in EP fluid systems, very high water levels (greater than
such as detergents, dispersants, antioxidants, overbase
2 %) will begin to show a similar hydrogen-bonded OH stretch
additives, etc. may also generate significant absorbance in the
band as seen in the crankcase oils.
condition monitoring regions of interest. Blends of petroleum
A1.3.2.2 Water Interferences—As the principal water mea-
lubricants with significant amounts of ester, whether part of the
surement is based on the integrated absorbance with no local
base-stock package or as an additive, will absorb strongly in
baseline correction, soot, dirt and high concentrations of
the oxidation area. These lubricants are not presented at this
infrared scattering particulates will generate higher than ex-
time.
pected readings for water. However, typical gearboxes and
A1.2.4 Fuel Contamination:
hydraulic systems will not contain particulate levels high
A1.2.4.1 The possibility of fuel contamination may be enough to cause a significant baseline offset and tilt. Wear
indicated in diesel crankcase lubricants by measuring the peak metal analysis, particle counting or other applicable tests
-1
at 810 cm . Spectral characteristics of diesel (Figs. A1.5 and should condemn gear and hydraulic systems that manifest such
A1.6) and other fuels noted in Table A1.1 have been found to extreme particulate levels.
E2412 − 23a
A1.3.3 Oxidation: Fig. A1.10. As this area is closely associated with the water
A1.3.3.1 The oxidative breakdown measurement shown in measurement area, a localized, single–point baseline at
–1
Fig. A1.8 in petroleum EP fluids is the same as in the 3595 cm provides a correction for low levels of water
petroleum-based crankcase fluids discussed in A1.2.3.2. Note buildup (Fig. A1.10).
that while Fig. A1.8 also shows an increase in sulfation
A1.4.3.3 Ester Base-Stock Breakdown II—In addition to the
by-products, not all EP systems will show this effect.
breakdown area I, a second area associated with the traditional
OH stretch (as measured for water in crankcase oils) also
A1.4 Synthetic Polyol Ester Lubricants (Typically Aero-
increases as the lubricant breaks down. This ester base-stock
Derivative Gas Turbines):
breakdown II area is also monitored as a measurement of
A1.4.1 Condition monitoring of high-performance aircraft
degradation of the polyol ester lubricants. The breakdown II
turbine engines is widely applied in both the military and region is also highlighted in Fig. A1.10.
commercial aviation maintenance industries. In addition, many
A1.4.3.4 Ester Base-Stock Breakdown Interferences—As
aero-derivative gas turbines are used in power generation,
noted above in A1.4.2.2 where excessive base-stock break-
marine transport and other non-aeronautical applications. In
down interferes with the water measurement, a similar effect
these systems, the primary lubricant is a synthetic polyol ester
has also been noted with the lubricant breakdown measure-
and is available under a variety of different military specifica-
ment. Excessive water levels may cause the lubricant break-
tions and commercial item descriptions and brand names.
down reading to be higher than the actual level. Once again
Table A1.3 lists the condition monitoring properties of interest
however, water levels of this magnitude will condemn the
measured by FT-IR along with the band measurement area and
lubricant irrespective of the actual breakdown level.
the baseline point(s).
A1.4.4 Antiwear Components:
A1.4.2 Water:
A1.4.4.1 While the antiwear compounds used in crankcase
A1.4.2.1 Just as the infrared measurement for water was
oils and polyol ester lubricants are typically different species,
adjusted to account for the different interactions in the formu-
the most common compounds used for both oils have a
lations in crankcase and EP oils, a different water measurement
phosphate functional group. For this reason, the measurement
area is also required for the polyol esters. Fig. A1.9 shows the
area developed for monitoring levels and trends of ZDDP has
area under the curve that is integrated for the determination of
been found to be equally useful for monitoring tricresyl
water contamination in these systems, with the measurement
phosphate (TCP). Fig. A1.11 shows varying levels of TCP
highlighted for a sample containing 1000 ppm of added water.
blended into a polyol ester lubricant. As previously noted,
Note that the water in these systems shows up as a broad band,
building calibration curves for measurement parameters (when
similar to what is observed for water in the crankcase oils, but
pure or prepared standards are available) is possible. However,
the strongest response occurs at higher frequencies than in the
this is not necessary, as lubricant condition monitoring requires
–1 –1
case of the crankcase oils (~3700 cm to 3600 cm for polyol
only reliable, repeatable measurements. Correlation of FT-IR
–1 –1
esters versus 3500 cm to 3150 cm for crankcase oils).
measurements to physical values is not necessary.
A1.4.2.2 Water Interferences—The most significant interfer-
A1.4.5 Fuel Contamination:
ence found in the determination of water is interference from
A1.4.5.1 Fuel contamination is monitored in polyol ester
the polyol ester lubricant breakdown I (see A1.4.3). Under
–1
lubricants by measuring the peak at 810 cm as given in
severe conditions of lubricant degradation, this band will begin
section A1.2.4.
to overlap and contribute to the integrated water measurement
area. As seen below in Fig. A1.10 however, this effect is only
A1.4.6 Other Fluid Contamination:
seen when the lubricant is already severely degraded, which
A1.4.6.1 In addition to fuel contamination, foreign oils and
dictates maintenance action from the degradation irrespective
hydraulic fluids may contaminate lubricating oils (for example,
of the actual water level.
polyol ester contaminated by a petroleum based fluid). In most
A1.4.3 Ester Base-Stock Breakdown: cases, identifying the presence of a foreign fluid is all that is
A1.4.3.1 As the polyol esters are a different chemical required to generate an appropriate maintenance response. The
system than petroleum based lubricants, degradation of the wide variety of potential contaminants suggests an equally
polyol ester lubricant produces different breakdown products. wide variety of measurement methods may be desirable. In
The most common degradation pathway in ester based lubri- addition, multiple frequency distributions may also be required
cants is the conversion of the ester into organic acids and and are not given here. The measurement areas given in Table
alcohols. A1.3 demonstrate the measurement used to indicate the pres-
A1.4.3.2 Ester Base-Stock Breakdown I—The resulting ence of petroleum oils, phosphate ester oils, or polyalphaolefin
polyol ester degradation products are first seen between (PAO)/diester blend oils contaminating polyol ester oils. Fig.
–1 –1
3595 cm and 3500 cm , and the measurement is noted as A1.12 shows an example of polyol ester oil contaminated by a
polyalphaolefin (PAO)/diester blend oil.
ester base-stock breakdown I in Table A1.3 and highlighted in
E2412 − 23a
TABLE A1.1 Petroleum Lubricant (for example, Crankcase) Condition Monitoring Parameters—Direct Trending
-1 -1 A
Component Measurement Area, cm Baseline Point(s), cm Reporting
Water Area 3500 to 3150 Minima 4000 to 3680 and 2200 to 1900 Report Value as Measured
Soot Loading Absorbance intensity at 2000 None Value × 100
Oxidation Area 1800 to 1670 Minima 2200 to 1900 and 650 to 550 Report Value as Measured
Nitration Area from 1650 to 1600 Minima 2200 to 1900 and 650 to 550 Report Value as Measured
Antiwear Components Area 1025 to 960 Minima 2200 to 1900 and 650 to 550 Report Value as Measured
(Phosphate based, typically ZDDP)
Gasoline Area 755 to 745 Minima 780 to 760 and 750 to 730 Report Value as Measured
B
Diesel (JP-5, JP-8) Area 815 to 805 Minima 835 to 825 and 805 to 795 (Value + 2) × 100
Sulfate by-products Area 1180 to 1120 Minima 2200 to 1900 and 650 to 550 Report value as measured
Ethylene Glycol Coolant Area 1100 to 1030 Minima 1130 to 1100 and 1030 to 1010 Report value as measured
A
Reporting values in absorbance/0.1 mm (see 6.1.2).
B
Spectral characteristics of diesel and other noted fuels have been found to vary. Work is currently active on other IR measurement areas and techniques. The
measurement listed can be used as a guideline but is not intended to be the only infrared based fuel contamination measurement. Checking suspect fuel sources is
suggested to verify presence of indicator absorbance bands.
FIG. A1.1 Example of Integrated Band Measurement Area for Water in Crankcase Oil
E2412 − 23a
FIG. A1.2 Soot Measurement in Diesel Crankcase Oils
FIG. A1.3 Oxidation and Nitration Measurement in Crankcase Oils
E2412 − 23a
FIG. A1.4 Sulfation Measurement in Crankcase Oils
FIG. A1.5 Fuel Measurement in Crankcase Oils
E2412 − 23a
FIG. A1.6 Glycol Contamination Measurement in Diesel Engine Oils
TABLE A1.2 Petroleum Based EP Fluid Condition Monitoring Parameters—Direct Trending
-1 -1 A
Component Measurement Area, cm Baseline Point(s), cm Reporting
Water Area 3400 to 3250 No Baseline Value × 20
Oxidation Area 1800 to 1670 Minima 2200 to 1800 and 650 to 550 Report Value as Measured
A
Reporting values in absorbance/0.1 mm (see 6.1.2).
FIG. A1.7 Water Contamination Measurement in EP Fluids
E2412 − 23a
FIG. A1.8 Oxidation Measurement in EP Fluids
TABLE A1.3 Polyol Ester Fluid Condition Monitoring Parameters—Direct Trending
Measurement Area,
-1 A
Component Baseline Point(s), cm Reporting
-1
cm
Water Area 3700 to 3595 Minima 3950 to 3770 Value x 10
and 2200 to 1900
Ester Base-Stock Breakdown I Area 3595 to 3500 Single point at 3595 Value x 10
Ester Base-Stock Breakdown II Area 3330 to 3150 Minima 3950 to 3770 Value x 10
and 2200 to 1900
Antiwear Components (typically TCP) Area 1025 to 960 Minima 2200 to 1900 Report value as measured
and 650 to 550
B
Fuel (JP-4, JP-5, JP-8) Area 815 to 805 Minima 835 to 825 (Value + 2) x 100
and 805 to 795
Other Contaminants in Polyol Ester Synthetics Area 1425 to 1390 None Report value as measured
C
(for example, Petroleum Lubricants and Hydraulic Fluids) and 1090 to 1030
A
Reporting values in absorbance/0.1 mm (see 6.1.2).
B
Spectral characteristics of noted fuels have been found to vary. Work is currently active on other IR measurement areas and techniques. The measurement listed can
be used as a guideline but is not intended to be the only infrared based fuel contamination measurement. Checking suspect fuel sources is suggested to verify presence
of indicator absorbance bands.
C
Alternate multivariate techniques such as PCR, PLS and factor analysis such as given in Guide D8321 can also be used.
E2412 − 23a
FIG. A1.9 Water Contamination Measurement in Polyol Ester Lubricants
FIG. A1.10 Ester Base-Stock Breakdown Measurements in Polyol Ester Lubricants
E2412 − 23a
FIG. A1.11 Measurement of Antiwear (TCP) in Polyol Ester Lubricants
FIG. A1.12 Polyol Ester Lubricant Contaminated with PAO/Diester Oil
E2412 − 23a
A2. MEASUREMENT OF MOLECULAR PARAMETERS IN VARIOUS SYSTEMS—SPECTRAL SUBTRACTION
A2.1 This annex does not purport to discuss all lubricant A2.2.1.3 Interferences—Ethylene glycol will interfere with
types. Measurement parameters for petroleum lubricants are the ability to accurately quantify water level when present
presented. As data becomes available, other lubricant types can since it also contains hydroxyl groups. However, the converse
be added to the annex. is not true since glycol has other spectral features that are used
for detection and quantification. Therefore, when glycol is
NOTE A2.1—It is not the intent of this practice to establish or
recommend normal, cautionary, warning or alert limits for any machinery
present, water can be detected but not reliably quantified using
or fluids. Such limits should be established in conjunction with advice and
FT-IR. This is not considered a problem because of the greater
...