ASTM D7684-11(2020)
(Guide)Standard Guide for Microscopic Characterization of Particles from In-Service Lubricants
Standard Guide for Microscopic Characterization of Particles from In-Service Lubricants
SIGNIFICANCE AND USE
5.1 The objective of particle examination is to diagnose the operational condition of the machine sampled based on the quantity and type of particles observed in the oil. After break-in, normally running machines exhibit consistent particle concentration and particle types from sample to sample. An increase in particle concentration, accompanied by an increase in size and severity of particle types, is indicative of initiation of a fault. This guide describes commonly found particles in in-service lubricants, but does not address methodology for quantification of particle concentration.
5.2 This guide is provided to promote improved and expanded use of particulate debris analysis with in-service lubricant analysis. It helps overcome some perceived complexity and resulting intimidation that effectively limits particulate debris analysis to the hands of a specialized and very limited number of practitioners. Standardized terminology and common reporting formats provide consistent interpretation and general understanding.
5.3 Without particulate debris analysis, in-service lubricant analysis results often fall short of concluding likely root cause or potential severity from analytical results because of missing information about the possible identification or extent of damaging mechanisms.
5.4 Caution shall be exercised when drawing conclusions from the particles found in a particular sample, especially if the sample being examined is the first from that type of machine. Some machines, during normal operation, generate wear particles that would be considered highly abnormal in other machines. For example, many gear boxes generate severe wear particles throughout their expected service life, whereas just a few severe wear particles from an aircraft gas turbine oil sample may be highly abnormal. Sound diagnostics require that a baseline, or typical wear particle signature, be established for each machine type under surveillance.
SCOPE
1.1 This guide covers the classification and reporting of results from in-service lubricant particulate debris analysis obtained by microscopic inspection of wear and contaminant particles extracted from in-service lubricant and hydraulic oil samples. This guide suggests standardized terminology to promote consistent reporting, provides logical framework to document likely or possible root causes, and supports inference associated machinery health condition or severity based on available debris analysis information.
1.2 This guide shall be used in conjunction with an appropriate wear debris analysis sample preparation and inspection technique including, but not limited to, one of the following:
1.2.1 Ferrography using linear glass slides,
1.2.2 Ferrography using rotary glass slides,
1.2.3 Patch analysis using patch makers (filtration through membrane filters),
1.2.4 Filter debris analysis,
1.2.5 Magnetic plug inspection, or
1.2.6 Other means used to extract and inspect particulate debris from in-service lubricants.
1.3 This standard is not intended to evaluate or characterize the advantage or disadvantage of one or another of these particular particle extraction and inspection methods.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
- Status
- Published
- Publication Date
- 31-Oct-2020
- Technical Committee
- D02 - Petroleum Products, Liquid Fuels, and Lubricants
Relations
- Effective Date
- 01-Feb-2024
- Refers
ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants - Effective Date
- 15-Dec-2023
- Refers
ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants - Effective Date
- 01-Jul-2023
- Effective Date
- 01-May-2020
- Effective Date
- 01-Nov-2015
- Effective Date
- 01-Jun-2015
- Effective Date
- 01-Feb-2015
- Effective Date
- 01-Jun-2013
- Effective Date
- 01-May-2012
- Effective Date
- 01-Jan-2011
- Effective Date
- 01-Dec-2010
- Effective Date
- 01-Jul-2010
- Effective Date
- 01-Jul-2010
- Effective Date
- 01-May-2010
- Effective Date
- 01-Jan-2010
Overview
ASTM D7684-11(2020), Standard Guide for Microscopic Characterization of Particles from In-Service Lubricants, is a comprehensive standard developed by ASTM International. This guide provides industry professionals with best practices for the classification and reporting of debris particles extracted from lubricants and hydraulic fluids during in-service analysis. By enabling the consistent microscopic examination and characterization of wear and contaminant particles, the standard helps diagnose the operational condition and potential faults of machinery based on oil sample analysis.
This guide promotes the regular and expanded use of particulate debris analysis within routine in-service lubricant analysis, introducing standardized terminology and reporting formats that produce more reliable and actionable results. While the standard outlines how to identify and document particle types, it does not prescribe methods for quantifying particle concentration.
Key Topics
- Particle Characterization: Provides methods for classifying particles based on morphology, composition, and probable origin, allowing for the detection of early warning signs of machinery faults such as wear, corrosion, and contamination.
- Consistent Reporting: Promotes the use of common terminology and standardized grids or tables for consistent data recording and interpretation across organizations and industries.
- Sample Preparation Techniques: Lists approved ways to extract and prepare debris from oil samples, including:
- Analytical ferrography on linear or rotary glass slides
- Patch analysis using membrane filtration
- Filter debris analysis
- Magnetic plug inspection
- Diagnostic Value: Emphasizes the importance of establishing baseline wear particle signatures for each monitored machine type, acknowledges normal vs. abnormal particle generation across machine types, and distinguishes among common wear mechanisms.
- Practical Framework: Introduction of decision grids and severity rankings (normal, low alert, high alert, low fault, high fault) to assess machinery health and the urgency of maintenance actions based on debris findings.
- Terminology Standardization: Harmonizes definitions for wear-related terminology (such as abrasive wear, fatigue wear, fretting, and spalling) to ensure clarity in reporting and communication.
- Safety and Regulatory Considerations: Includes a reminder that safety, health, and environmental practices must be established by users, as the standard does not address all safety concerns.
Applications
ASTM D7684-11(2020) is commonly used in a variety of industries where in-service lubricant condition monitoring is critical, especially in power generation, aviation, heavy machinery, marine, manufacturing, and automotive sectors. Its practical applications include:
- Routine Condition Monitoring: Early detection of abnormal wear and potential faults, enabling predictive and preventive maintenance, reducing unexpected downtime, and extending equipment life.
- Root Cause Analysis: Facilitating identification of wear mechanisms by linking specific particle types to probable failure modes, supporting targeted corrective actions.
- Reporting and Trending: Establishing a systematic and comparable approach to data collection, storage, and cross-machine or historical analysis for improved maintenance planning.
- Staff Training: Serving as a foundational reference for cross-training laboratory analysts and maintenance teams in best practices for lubricant debris analysis.
Related Standards
ASTM D7684-11(2020) is designed to be used alongside other standards in lubricant analysis and wear particle characterization, including:
- ASTM D7690: Practice for Microscopic Characterization of Particles from In-Service Lubricants by Analytical Ferrography
- ASTM D7596: Test Method for Automatic Particle Counting and Particle Shape Classification of Oils
- ASTM D7647: Test Method for Automatic Particle Counting of Lubricating and Hydraulic Fluids
- ASTM D7416: Practice for Analysis of In-Service Lubricants Using Integrated Testers
- ASTM D4175 / G40: Terminology relating to petroleum products, wear, and erosion
- ISO 11171: Calibration of automatic particle counters for liquids
By adhering to ASTM D7684-11(2020), organizations ensure a reliable, standardized approach to the microscopic characterization of wear particles in lubricants, supporting more effective equipment maintenance strategies and asset reliability programs.
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Frequently Asked Questions
ASTM D7684-11(2020) is a guide published by ASTM International. Its full title is "Standard Guide for Microscopic Characterization of Particles from In-Service Lubricants". This standard covers: SIGNIFICANCE AND USE 5.1 The objective of particle examination is to diagnose the operational condition of the machine sampled based on the quantity and type of particles observed in the oil. After break-in, normally running machines exhibit consistent particle concentration and particle types from sample to sample. An increase in particle concentration, accompanied by an increase in size and severity of particle types, is indicative of initiation of a fault. This guide describes commonly found particles in in-service lubricants, but does not address methodology for quantification of particle concentration. 5.2 This guide is provided to promote improved and expanded use of particulate debris analysis with in-service lubricant analysis. It helps overcome some perceived complexity and resulting intimidation that effectively limits particulate debris analysis to the hands of a specialized and very limited number of practitioners. Standardized terminology and common reporting formats provide consistent interpretation and general understanding. 5.3 Without particulate debris analysis, in-service lubricant analysis results often fall short of concluding likely root cause or potential severity from analytical results because of missing information about the possible identification or extent of damaging mechanisms. 5.4 Caution shall be exercised when drawing conclusions from the particles found in a particular sample, especially if the sample being examined is the first from that type of machine. Some machines, during normal operation, generate wear particles that would be considered highly abnormal in other machines. For example, many gear boxes generate severe wear particles throughout their expected service life, whereas just a few severe wear particles from an aircraft gas turbine oil sample may be highly abnormal. Sound diagnostics require that a baseline, or typical wear particle signature, be established for each machine type under surveillance. SCOPE 1.1 This guide covers the classification and reporting of results from in-service lubricant particulate debris analysis obtained by microscopic inspection of wear and contaminant particles extracted from in-service lubricant and hydraulic oil samples. This guide suggests standardized terminology to promote consistent reporting, provides logical framework to document likely or possible root causes, and supports inference associated machinery health condition or severity based on available debris analysis information. 1.2 This guide shall be used in conjunction with an appropriate wear debris analysis sample preparation and inspection technique including, but not limited to, one of the following: 1.2.1 Ferrography using linear glass slides, 1.2.2 Ferrography using rotary glass slides, 1.2.3 Patch analysis using patch makers (filtration through membrane filters), 1.2.4 Filter debris analysis, 1.2.5 Magnetic plug inspection, or 1.2.6 Other means used to extract and inspect particulate debris from in-service lubricants. 1.3 This standard is not intended to evaluate or characterize the advantage or disadvantage of one or another of these particular particle extraction and inspection methods. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
SIGNIFICANCE AND USE 5.1 The objective of particle examination is to diagnose the operational condition of the machine sampled based on the quantity and type of particles observed in the oil. After break-in, normally running machines exhibit consistent particle concentration and particle types from sample to sample. An increase in particle concentration, accompanied by an increase in size and severity of particle types, is indicative of initiation of a fault. This guide describes commonly found particles in in-service lubricants, but does not address methodology for quantification of particle concentration. 5.2 This guide is provided to promote improved and expanded use of particulate debris analysis with in-service lubricant analysis. It helps overcome some perceived complexity and resulting intimidation that effectively limits particulate debris analysis to the hands of a specialized and very limited number of practitioners. Standardized terminology and common reporting formats provide consistent interpretation and general understanding. 5.3 Without particulate debris analysis, in-service lubricant analysis results often fall short of concluding likely root cause or potential severity from analytical results because of missing information about the possible identification or extent of damaging mechanisms. 5.4 Caution shall be exercised when drawing conclusions from the particles found in a particular sample, especially if the sample being examined is the first from that type of machine. Some machines, during normal operation, generate wear particles that would be considered highly abnormal in other machines. For example, many gear boxes generate severe wear particles throughout their expected service life, whereas just a few severe wear particles from an aircraft gas turbine oil sample may be highly abnormal. Sound diagnostics require that a baseline, or typical wear particle signature, be established for each machine type under surveillance. SCOPE 1.1 This guide covers the classification and reporting of results from in-service lubricant particulate debris analysis obtained by microscopic inspection of wear and contaminant particles extracted from in-service lubricant and hydraulic oil samples. This guide suggests standardized terminology to promote consistent reporting, provides logical framework to document likely or possible root causes, and supports inference associated machinery health condition or severity based on available debris analysis information. 1.2 This guide shall be used in conjunction with an appropriate wear debris analysis sample preparation and inspection technique including, but not limited to, one of the following: 1.2.1 Ferrography using linear glass slides, 1.2.2 Ferrography using rotary glass slides, 1.2.3 Patch analysis using patch makers (filtration through membrane filters), 1.2.4 Filter debris analysis, 1.2.5 Magnetic plug inspection, or 1.2.6 Other means used to extract and inspect particulate debris from in-service lubricants. 1.3 This standard is not intended to evaluate or characterize the advantage or disadvantage of one or another of these particular particle extraction and inspection methods. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
ASTM D7684-11(2020) is classified under the following ICS (International Classification for Standards) categories: 75.100 - Lubricants, industrial oils and related products. The ICS classification helps identify the subject area and facilitates finding related standards.
ASTM D7684-11(2020) has the following relationships with other standards: It is inter standard links to ASTM D7647-24, ASTM D4175-23a, ASTM D4175-23e1, ASTM D7416-09(2020), ASTM G40-15, ASTM D7416-09(2015), ASTM D4130-15, ASTM G40-13, ASTM G40-12, ASTM D7690-11, ASTM G40-10b, ASTM D7647-10, ASTM G40-10a, ASTM D7596-10, ASTM G40-10. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
ASTM D7684-11(2020) is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7684 − 11 (Reapproved 2020)
Standard Guide for
Microscopic Characterization of Particles from In-Service
Lubricants
This standard is issued under the fixed designation D7684; 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 ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This guide covers the classification and reporting of
mendations issued by the World Trade Organization Technical
results from in-service lubricant particulate debris analysis
Barriers to Trade (TBT) Committee.
obtained by microscopic inspection of wear and contaminant
particles extracted from in-service lubricant and hydraulic oil
2. Referenced Documents
samples. This guide suggests standardized terminology to
2.1 ASTM Standards:
promote consistent reporting, provides logical framework to
D4130 Test Method for Sulfate Ion in Brackish Water,
documentlikelyorpossiblerootcauses,andsupportsinference
Seawater, and Brines
associated machinery health condition or severity based on
D4175 Terminology Relating to Petroleum Products, Liquid
available debris analysis information.
Fuels, and Lubricants
1.2 This guide shall be used in conjunction with an appro-
D7416 Practice for Analysis of In-Service Lubricants Using
priate wear debris analysis sample preparation and inspection
a Particular Five-Part (Dielectric Permittivity, Time-
technique including, but not limited to, one of the following:
Resolved Dielectric Permittivity with Switching Magnetic
1.2.1 Ferrography using linear glass slides,
Fields, Laser Particle Counter, Microscopic Debris
1.2.2 Ferrography using rotary glass slides,
Analysis, and Orbital Viscometer) Integrated Tester
1.2.3 Patch analysis using patch makers (filtration through
D7596 Test Method for Automatic Particle Counting and
membrane filters),
Particle Shape Classification of Oils Using a Direct
1.2.4 Filter debris analysis,
Imaging Integrated Tester
1.2.5 Magnetic plug inspection, or
D7647 Test Method for Automatic Particle Counting of
1.2.6 Other means used to extract and inspect particulate
Lubricating and Hydraulic Fluids Using Dilution Tech-
debris from in-service lubricants.
niques to Eliminate the Contribution of Water and Inter-
1.3 This standard is not intended to evaluate or characterize
fering Soft Particles by Light Extinction
the advantage or disadvantage of one or another of these
D7690 Practice for Microscopic Characterization of Par-
particular particle extraction and inspection methods.
ticles from In-Service Lubricants by Analytical Ferrogra-
phy
1.4 The values stated in SI units are to be regarded as
G40 Terminology Relating to Wear and Erosion
standard. No other units of measurement are included in this
2.2 ISO Standard:
standard.
ISO11171 Hydraulicfluidpower–Calibrationofautomatic
1.5 This standard does not purport to address all of the
particle counters for liquids
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3. Terminology
priate safety, health, and environmental practices and deter-
3.1 Definitions:
mine the applicability of regulatory limitations prior to use.
3.1.1 abrasive wear, n—wear due to hard particles or hard
1.6 This international standard was developed in accor-
protuberances forced against and moving along a solid surface.
dance with internationally recognized principles on standard-
G40
This guide is under the jurisdiction of ASTM Committee D02 on Petroleum
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
mittee D02.96.06 on Practices and Techniques for Prediction and Determination of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Microscopic Wear and Wear-related Properties. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2020. Published December 2020. Originally the ASTM website.
approved in 2011. Last previous edition approved in 2016 as D7684 – 11 (2016). Available from International Organization for Standardization (ISO), 1, ch. de
DOI: 10.1520/D7684-11R20. la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, www.iso.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7684 − 11 (2020)
3.1.2 abrasion, n—wear by displacement of material caused 3.1.18 wear, n—damagetoasolidsurface,usuallyinvolving
by hard particles or hard protuberances. D4175 progressive loss or displacement of material, due to relative
motion between that surface and a contacting substance or
3.1.3 break-in, n—see run-in. G40
substances. D4175, G40
3.1.4 fatigue wear, n—wear of a solid surface caused by
3.2 Definitions of Terms Specific to This Standard:
fracture arising from material fatigue. G40
3.2.1 abrasive wear particles, n—longwire-likeparticlesin
3.1.5 fretting, n—in tribology, small amplitude oscillatory
the form of loops or spirals that are generated due to hard,
motion, usually tangential, between two solid surfaces in
abrasive particles present between wearing surfaces of unequal
contact.
hardness; sometimes called cutting wear particles or ribbons.
3.1.5.1 Discussion—Here the term fretting refers only to the
3.2.2 analytical ferrography, n—technique whereby par-
nature of the motion without reference to the wear, corrosion,
ticles from an oil sample deposited by a ferrograph are
orotherdamagethatmayensue.Thetermfrettingisoftenused
identified to aid in establishing wear mode inside an oil-wetted
to denote fretting corrosion and other forms of fretting wear.
path of a machine.
Usage in this sense is discouraged due to the ambiguity that
3.2.3 chunks, n—free metal particles >5 µm with a shape
may arise. G40
factor (major dimension to thickness ratio) of <5:1.
3.1.6 fretting wear, n—wear arising as a result of fretting
3.2.4 contaminant particles, n—particles introduced from
(see fretting). G40
an extraneous source into the lubricant of a machine or engine.
3.1.7 lubricant, n—any material interposed between two
3.2.5 corrosive wear debris, n—usually, extremely fine
surfaces that reduces the friction or wear between them. D4175
partially oxidized particles caused by corrosive attack. Par-
3.1.8 lubricating oil, n—liquid lubricant, usually compris-
ticles can become quite large in cases of extreme corrosion.
ing several ingredients, including a major portion of base oil
3.2.6 debris, n—in tribology, solid or semi-solid particulate
and minor portions of various additives. D4175
matter introduced to lubricant through contamination or de-
3.1.9 rolling, v—motion in a direction parallel to the plane tached from a surface due to a wear, corrosion, or erosion
of a revolute body (ball, cylinder, wheel, and so forth) on a
process.
surface without relative slip between the surfaces in all or part
3.2.7 ferrograph, n—apparatus that magnetically separates
of the contact area. G40
and deposits wear and contaminant particles onto a specially
prepared glass microscope slide.
3.1.10 rolling contact fatigue, n—damage process in a
triboelement subjected to repeated rolling contact loads, in-
3.2.8 fibers, n—long, thin, nonmetallic particles.
volving the initiation and propagation of fatigue cracks in or
3.2.9 filter debris analysis, n—in tribology, a process for
under the contact surface, eventually culminating in surface
extracting and inspecting debris accumulated on the filter
pits or spalls. G40
media taken from an in-line circulating lubrication system.
3.1.11 run-in, n—in tribology, an initial transition process
3.2.10 filter patch analysis, n—in tribology, a process using
occurring in newly established wearing contacts, often accom-
a filter patch maker to extract solid or semi-solid matter from
panied by transients in coefficient of friction or wear rate, or
a liquid and subsequently analyzing the extracted solid or
both,thatareuncharacteristicofthegiventribologicalsystem’s
semi-solid matter.
behavior. Syn. break-in and wear-in. G40
3.2.11 filter patch maker, n—in tribology, apparatus to
3.1.12 rust, n—of ferrous alloys, a corrosion product con-
extract solid or semi-solid matter from liquid by drawing a
sisting primarily of hydrated iron oxides. D4175
volume of solid-containing-liquid through a filter patch having
pores of prescribed dimension sufficient to retain the solid or
3.1.13 sliding wear, n—wear due to the relative motion in
semi-solid matter while allowing the liquid to pass through.
the tangential plane of contact between two solid bodies. G40
3.2.12 normal, n—in a five level severity ranking, a one-of-
3.1.14 sludge, n—precipitate or sediment from oxidized
five relative severity rating commonly associated with undam-
mineral oil and water. D4130
aged or as-new condition having reasonable wear or expected
3.1.15 spalling, n—in tribology, the separation of macro-
operational condition; see also low alert, high alert, low fault,
scopic particles from a surface in the form of flakes or chips,
and high fault severity conditions.
usuallyassociatedwithrollingelementbearingsandgearteeth,
3.2.13 low alert, n—in a five level severity ranking,a
but also resulting from impact events. G40
two-of-five level relative severity commonly associated with
3.1.16 three-body abrasive wear, n—form of abrasive wear
some deterioration from normal condition, however interven-
in which wear is produced by loose particles introduced or
tion is not yet recommended; see also normal, high alert, low
generated between the contacting surfaces.
fault, and high fault severity ranking.
3.1.16.1 Discussion—In tribology, loose particles are con-
3.2.14 high alert, n—in a five level severity ranking,a
sidered to be a “third body.” G40
three-of-five level relative severity commonly associated with
3.1.17 two-body abrasive wear, n—form of abrasive wear in significant deterioration from normal condition closely ap-
whichthehardparticlesorprotuberancesthatproducethewear proachingneedforintervention;seealso normal, low alert, low
of one body are fixed on the surface of the opposing body. G40 fault, and high fault severity ranking.
D7684 − 11 (2020)
3.2.15 low fault, n—in a five level severity ranking,a 3.2.27 severe sliding wear, n—in tribology,slidingwearthat
four-of-fiverelativeseveritycommonlyassociatedwithsignifi- removes subsurface metal; also called abnormal sliding wear.
cant deterioration from alert condition, and intervention is
3.2.28 severe sliding wear particles, n—in tribology, severe
recommended now; see also normal, low alert, high alert,
slidingwearparticlesare>15 µmandseveraltimeslongerthan
andhigh fault severity ranking.
theyarewide.Someoftheseparticleshavesurfacestriationsas
a result of sliding and they frequently have straight edges.
3.2.16 high fault, n—in a five level severity ranking,a
Their major dimension-to-thickness ratio is approximately
five-of-five relative severity commonly associated with signifi-
10:1.
cant deterioration from alert condition, and intervention is both
recommended and overdue; see also normal, low alert, high
3.2.29 severe wear particles, n—in tribology, free metal
alert, and low fault severity ranking.
particles >15 µm with major dimension-to-thickness ratios
between 5:1 and 30:1.
3.2.17 magnetic plug inspection—process for inspecting
and, if necessary, extracting ferrous alloy debris from in-
3.2.30 spheres, n—in tribology, metal spheres may be the
service lubricants using a magnetic object placed in the oil
result of incipient rolling contact fatigue or they may be
compartment, typically associated with a drain plug.
contaminant particles from welding, grinding, coal burning,
and steel manufacturing. Spheres may also be caused by
3.2.18 nonmetallic particles, n—in tribology, particles com-
electro-pitting.
prised of compounds, organic material, sand, dirt, glasses, and
so forth, that often demonstrate some element of translucence 3.2.31 wear particles, n—particles generated from a wear-
under microscopic backlight. ing surface of a machine.
3.2.19 platelets, n—flat metal particles with a length more-
4. Summary of Guide
or-less equal to their width, and a major dimension-to-
thickness ratio in the range of approximately 5:1 to 10:1 or 4.1 Periodic in-service lubricant samples are collected from
more (see rolling contact fatigue particles). a machine as part of a routine condition monitoring program.
The sample is prepared to separate particles from the sample
3.2.20 red oxide particles, n—rust particles present as poly-
fluid. The separated particles are subsequently examined using
crystalline agglomerates of Fe O appearing orange in re-
2 3
an optical microscope to identify the types of particles present
flected white light. These are usually due to water in the
to aid in identifying the wear mode occurring in the oil-wetted
lubricating system.
path of the machine.
3.2.21 reworked particles, n—large, very thin, free metal
4.2 In usual practice of a routine condition monitoring
particles often in the range of 20 to 50 µm in major dimension
program, particle separation and examination is not done for
with the frequent occurrence of holes consistent with the
every sample taken, but may be done when routine tests such
explanation that these are formed by the passage of a wear
as spectrometric analysis, particle counting, or ferrous debris
particle through a rolling contact.
monitoring indicate abnormal results.
3.2.22 ribbons, n—see abrasive wear particles.
4.3 This guide is to be used with a sample preparation
3.2.23 rolling contact fatigue particles, n—flat platelets,
method that extracts particulate debris from in-service lubri-
with a length more-or-less equal to their width, with smooth
cant systems for subsequent microscopic examination.
surfaces, random, jagged and irregularly shaped
4.4 The user of this guide should employ consistent termi-
circumferences, and a major dimension-to-thickness ratio in
nology to achieve accepted and understandable interpretations
the range of approximately 5:1 to 10:1 or more.
when communicating instructions and findings based on par-
3.2.24 rolling contact fatigue wear, n—in tribology, fatigue
ticle analysis.
wear caused by loaded rolling contact typically between roller
4.5 Aprocessissuggestedinstandardizedformattoidentify
and race in bearings or between gear teeth in the vicinity of the
and further classify multiple distinct groups of particulate
pitch line, typically forming spall-type pitting and releasing
debris extracted from an in-service machinery lubricating
rolling contact fatigue particles (see 3.2.23); also called rolling
sample.
fatigue wear or subsurface spalling.
4.6 A grid format is suggested in which the user of this
3.2.25 rubbing wear particles, n—particles generated as a
guide can present findings and report possible root causes
result of sliding wear in a machine, sometimes called mild
along with an assessment of associated machinery health
adhesive wear. Rubbing wear particles are free metal platelets
condition or severity based on available debris analysis infor-
with smooth surfaces, from approximately 0.5 to 15 µm in
mation.
major dimension and with major dimension-to-thickness ratios
from about 10:1 for larger particles to about 3:1 for smaller 4.7 An alternate classification scheme is suggested that is
particles. Any free metal particle <5 µm is classified as a consistent with Practice D7690.
rubbing wear particle regardless of shape factor unless it is a
sphere. 5. Significance and Use
3.2.26 scoring, n—in tribology, a consequence of severe 5.1 The objective of particle examination is to diagnose the
sliding wear characterized by formation of extensive grooves operational condition of the machine sampled based on the
and scratches in the direction of sliding; also called striation. quantity and type of particles observed in the oil. After
D7684 − 11 (2020)
break-in,normallyrunningmachinesexhibitconsistentparticle 7.2 Use a desired particulate extraction technique to prepare
concentration and particle types from sample to sample. An a specimen for microscopic wear debris analysis. Specimens
increase in particle concentration, accompanied by an increase are prepared using an apparatus that effectively extracts solid
in size and severity of particle types, is indicative of initiation particles from liquid samples and deposits the particles on a
of a fault. This guide describes commonly found particles in relatively flat supporting surface that can be placed on the
in-service lubricants, but does not address methodology for viewing stage of an optical microscope.
quantification of particle concentration.
7.3 Prepare specimens using one of the following particle
extraction techniques:
5.2 This guide is provided to promote improved and ex-
7.3.1 Analytical ferrography using ferrograph to produce
panded use of particulate debris analysis with in-service
lubricant analysis. It helps overcome some perceived complex- linear glass slides in accordance with Practice D7690,
7.3.2 Analytical ferrography using ferrograph to produced
ity and resulting intimidation that effectively limits particulate
debris analysis to the hands of a specialized and very limited rotary glass slides,
7.3.3 Filter patch analysis using filter patch makers,
number of practitioners. Standardized terminology and com-
mon reporting formats provide consistent interpretation and 7.3.4 Filter debris analysis,
general understanding. 7.3.5 Magnetic plug inspection, or
7.3.6 Other means used to extract and inspect particulate
5.3 Without particulate debris analysis, in-service lubricant
debris from in-service lubricants.
analysis results often fall short of concluding likely root cause
7.4 Inspect the specimen using an optical microscope and
or potential severity from analytical results because of missing
classify particles using the following procedures. It is common
information about the possible identification or extent of
for a single specimen to carry multiple kinds of particles so
damaging mechanisms.
classification is normally done for a group of particles by
5.4 Caution shall be exercised when drawing conclusions
characterizing individual particles representative of that group.
fromtheparticlesfoundinaparticularsample,especiallyifthe
7.5 Therefore, the first step when inspecting a specimen
sample being examined is the first from that type of machine.
normally involves scanning the entire specimen to identify
Some machines, during normal operation, generate wear par-
particle types that are of interest by group. Next, each group is
ticles that would be considered highly abnormal in other
characterized in a logical sequence. An atlas of example
machines. For example, many gear boxes generate severe wear
images is typically used to provide consistency and to assist
particles throughout their expected service life, whereas just a
with cross-training between operators. One such atlas is
few severe wear particles from an aircraft gas turbine oil
described in the Wear Particle Atlas.
sample may be highly abnormal. Sound diagnostics require
that a baseline, or typical wear particle signature, be estab-
7.6 For each group of particles the user should apply
lished for each machine type under surveillance.
consistent characterization criteria. Two example approaches
are given below in 7.7 and 7.8 that outline processes and
6. Reagents
format for analyzing and recording wear debris analysis
classification findings.
6.1 Use reagents of type and purity following specifications
from the manufacturer of the wear debris analysis sample
7.7 For the first example of a particle classification
preparation apparatus. Use reagents and solvents that do not
approach, see Table 1, which shows a tabular grid a user may
contribute significant particles to the sample.
constructtoguideinspectionanddocumentationofweardebris
analysis findings from a specimen. This kind of tabular grid
7. Procedure
may be printed out for note taking or it may be set up as a
computerized form that an operator can click, check, or mark
7.1 Particulate matter extracted from in-service lubricants
for ease of recording and database entry. An advantage of
are displayed on a relatively flat surface such as a filter patch,
computerized record keeping using this sort of particle char-
glass slide, or other substrate for microscopic inspection. The
acterization is that a body of knowledge may be used together
procedure normally involves the
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