ASTM D7898-14(2020)

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: D7898 − 14 (Reapproved 2020)
Standard Practice for
Lubrication and Hydraulic Filter Debris Analysis (FDA) for
Condition Monitoring of Machinery
This standard is issued under the fixed designation D7898; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Thepurposeofthispracticeistodescribebestpracticemethodsfortheanalysisoffilterdebrisfrom
machinery lubrication or hydraulic systems primarily for the purpose of machinery condition
monitoring. The purpose of Filter Debris Analysis (FDA) is to determine the health of oil-wetted
machinery by analyzing the size, quantity, morphology, and composition of debris trapped by the
system filter. FDA is emerging as an important condition monitoring technique as fine filtration
becomes more common and the associated reduction of metallic particulates makes traditional
elemental analysis of the lubricant less effective. System filters have an added advantage over
traditional sample-based techniques in that they capture a high percentage of the total system debris
(metallic, non-metallic, and organic particulate contamination) within the size range useful for
machinery condition monitoring.
1. Scope 2. Referenced Documents
1.1 This practice is intended to cover the extraction, 2.1 ASTM Standards:
analysis, and information management pertaining to visible D7684Guide for Microscopic Characterization of Particles
weardebriscollectedfromoilsystemfiltersordebrisretention
from In-Service Lubricants
screens. Further, it is intended that this practice be a practical
D7685Practice for In-Line, Full Flow, Inductive Sensor for
reference for those involved in FDA.
Ferromagnetic and Non-ferromagnetic Wear Debris De-
termination and Diagnostics forAero-Derivative andAir-
1.2 The values stated in SI units are to be regarded as
craft Gas Turbine Engine Bearings
standard. No other units of measurement are included in this
D7720Guide for Statistically Evaluating Measurand Alarm
standard.
Limits when Using Oil Analysis to Monitor Equipment
1.3 This standard does not purport to address all of the
and Oil for Fitness and Contamination
safety concerns, if any, associated with its use. It is the
D7690Practice for Microscopic Characterization of Par-
responsibility of the user of this standard to establish appro-
ticles from In-Service Lubricants by Analytical Ferrogra-
priate safety, health, and environmental practices and deter-
phy
mine the applicability of regulatory limitations prior to use.
F316Test Methods for Pore Size Characteristics of Mem-
1.4 This international standard was developed in accor-
brane Filters by Bubble Point and Mean Flow Pore Test
dance with internationally recognized principles on standard-
G40Terminology Relating to Wear and Erosion
ization established in the Decision on Principles for the
D4175Terminology Relating to Petroleum Products, Liquid
Development of International Standards, Guides and Recom-
Fuels, and Lubricants
mendations issued by the World Trade Organization Technical
2.2 Other Standards:
Barriers to Trade (TBT) Committee.
TTCP-AER-TP3-TR01-2010Guide for Filter DebrisAnaly-
sis
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
mittee D02.96.06 on Practices and Techniques for Prediction and Determination of For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Microscopic Wear and Wear-related Properties. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Nov. 1, 2020. Published December 2020. Originally Standards volume information, refer to the standard’s Document Summary page on
approved in 2014. Last previous edition approved in 2014 as D7898–14. DOI: the ASTM website.
10.1520/D7898-14R20. Published by the Technical Co-operation Program (TTCP), July 2010.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7898 − 14 (2020)
3. Terminology tached from a surface due to wear, corrosion, or erosion
process. D7684
3.1 Definitions:
3.1.7 debris, n—in internal combustion engines, solid con-
3.1.1 abrasive wear, n—wear due to hard particles or hard
protuberancesforcedagainstandmovingalongasolidsurface. taminant materials unintentionally introduced into the engine
or resulting from wear. D4175
D4175
3.1.8 filter debris analysis (FDA), n—intribology,aprocess
3.1.1.1 Discussion—Also called cutting wear in some in-
for extracting and inspecting debris accumulated on the filter
stances such as machining swarf.
media taken from an in-line circulating lubricating system.
3.1.1.2 abrasive wear particles, n—long wire-like particles
D7684
in the form of loops or spirals that are generated due to hard,
abrasiveparticlespresentbetweenwearingsurfacesofunequal 3.1.9 non-ferrous metal particles, n—free metal particle
hardness; sometimes called cutting wear particles or ribbons.
composed of any metal except iron. All common nonferrous
D7684 metals behave nonmagnetically except nickel. D7690
3.1.1.3 three body abrasive wear, n—form of abrasive wear
3.1.10 nonmetallic particles, n—particles comprised of
in which wear is produced by loose particles introduced or
compounds, organic material, glasses, etc. that have bound
generated between the contacting surfaces. D7684
electrons in their atomic structure. D7690
3.1.1.4 two body abrasive wear, n—formofabrasivewearin
3.1.10.1 nonmetallic amorphous particles, n—particles
whichthehardparticlesorprotuberancesthatproducethewear
withoutlongrangeatomicorderthataretransparentandthatdo
ofonebodyarefixedonthesurfaceoftheopposingbody. G40
not appear bright in polarized light. D7690
3.1.2 adhesive wear, n—wear due to localized bonding
3.1.10.2 nonmetallic crystalline particles, n—particles with
between contacting solid surfaces leading to material transfer
long range atomic structure that appear bright in polarized
between the two surfaces or loss from either surface. G40
light. These may be single crystals but are most likely
3.1.2.1 Discussion—Also called sliding wear or rubbing
polycrystalline or polycrystalline agglomerates. D7690
wear.
3.1.11 rolling contact fatigue, n—damage process in a
3.1.2.1 rubbing wear particles, n—particles generated as a
triboelement subjected to repeated rolling contact loads, in-
result of sliding wear in a machine, sometimes called mild
volving the initiation and propagation of fatigue cracks in or
adhesive wear. Rubbing particles are free metal platelets with
under the contact surface, eventually culminating in surface
smooth surfaces, from approximately 0.5 to 15 µm in major
pits or spalls. G40
dimension and with major dimension-to-thickness ratios from
3.1.12 scoring, n—in tribology, a consequence of severe
about ten to one for larger particles to about three to one for
sliding wear characterized by formation of extensive grooves
smaller particles.Any free metal particle <5 µm is classified as
and scratches in the direction of sliding; also called striation.
a rubbing wear particle regardless of shape factor unless it is a
D7684
sphere. D7684
3.1.13 spalling, n—in tribology, the separation of macro-
3.1.2.1 Discussion—Rubbingparticlescanalsobeattributed
scopic particles from a surface in the form of flakes or chips,
tothebenignremovalofasperities(polishing)ofwearsurfaces
usuallyassociatedwithrollingelementbearingsandgearteeth,
during run-in of machine.
but also resulting from impact events. G40
3.1.2.2 severe sliding wear particles, n—intribology,severe
3.1.14 wear particles, n—particles generated from a wear-
slidingwearparticlesare>15µmandseveraltimeslongerthan
ing surface of a machine. D7684
theyarewide.Someoftheseparticleshavesurfacestriationsas
a result of sliding, and they frequently have straight edges.
3.2 Definitions of Terms Specific to This Standard:
Their major dimension-to-thickness ratio is approximately ten
3.2.1 debris, n—particulate recovered from a machine con-
to one. D7684
taining both wear-related, benign (for example, residual over-
3.1.2.1 Discussion—Severe Sliding Particles can be gener-
haul swarf), or organic material, or combinations thereof,
ated as a result of inadequate lubrication, wrong lubricant,
foreign to the system.
extreme loading, or no lubricant. Ferrous particles can often
3.2.2 Feret’s diameter, n—the largest distance between two
exhibitheattintingcolorationontheirsurfaceasaresultofthe
parallellinesthatjusttouchestheedgeofanirregularlyshaped
high frictional temperatures experienced during this process.
particle. Also known as calliper diameter.
3.1.3 asperity, n—a protuberance in the small-scale topo-
3.2.3 ferrous debris, n—metallicdebrisconsistingmainlyof
graphical irregularities of a solid surface. G40
iron (Fe) and exhibiting ferro-magnetic behavior (that is, the
3.1.4 contaminant particles, n—particles introduced from
material is attracted or repelled when exposed to a magnetic
anextraneoussourceintothelubricantofamachineorengine.
field). Recommended abbreviation: Fe.
D7690
3.2.4 filter bypass system, n—a system by which circulating
3.1.5 debris, n—in tribology, particles that have become
fluid can bypass the filter element if the differential pressure
detached in a wear or erosion process. G40
across the filter becomes excessive due to blockage by con-
3.1.6 debris, n—in tribology, solid or semi-solid particulate tamination. Under bypass conditions, fluid can continue to
matter introduced to lubricant through contamination or de- circulate but will be unfiltered.
D7898 − 14 (2020)
3.2.5 filter debris, n—any matter captured in a system filter 4. Summary of Practice
element.
4.1 Lubrication and hydraulic system filters are a rich
3.2.6 filter patch, n—a piece of filter material of known
source of information about system health that are seldom
permeability (mesh opening dimension) used to capture debris
exploited for machinery condition monitoring purposes. This
sized greater than the rated mesh opening; usually specified in
practiceseekstodefinesomeproceduresthatensureconsistent
µm. Also known as membrane patch.
extractionandanalysisoffilterdebrisinordertoassesssystem
3.2.7 filter patch mesh size, n—the diameter of the largest health.
sphere that can pass through the filter patch mesh opening.
5. Significance of Use
3.2.8 fine filtration, n—filtration applied to a lubrication or
hydraulic system that meets or exceeds a Beta ratio of 200 for
5.1 The objective of FDA is to diagnose the operational
5 µm (c) particles (that is, β ≥ 200).
5(c) condition of oil-wetted machinery systems in order to identify
3.2.9 graticule, n—fine lines of known spacing used to
abnormal wear or incipient component failures. Oil system
determine the scaling of microscopic images. filters (typically lubrication system or hydraulic systems)
capture the vast majority of metallic and non-metallic debris
3.2.10 metal map, n—alistofcomponentswithinamachine
generated or contained within a system. The exploitation of
bypartnumberorfunctiontogetherwiththecomponent’salloy
this potential source of information for machinery condition
specificationandcomposition.Alsoknownasmaterialsatlasor
monitoring purposes has been difficult in the past due to the
component material specification list.
absence of a clear automated or manual method for extracting,
3.2.11 parent system, n—themechanicalsystemfromwhich
analyzing, reporting, and archiving the debris. This practice is
the debris sample originated from, for example, helicopter
provided to enable a consistent approach to the analysis of
main rotor gearbox.
in-service debris captured in filters and is intended primarily
3.2.12 particle areas, n—this measurement is used by some
for lubrication or hydraulic systems.
aircraftmanufacturerstodefinethecriticalityofweardebris.It
5.2 Caution shall be exercised when drawing conclusions
is not recommended since it is almost impossible to obtain an
based on particle quantity, composition, and morphology.Any
accurate measurement of an individual particle in the field
maintenance or operational actions shall be carefully consid-
without using appropriate particle image processing software.
ered and take into consideration any extant limits provided by
3.2.13 particle aspect ratio, n—the length of a predomi-
the manufacturer as well as any historical information known
nantly two-dimensional particle divided by its width.
about the subject system.
3.2.14 rolling contact fatigue particles, n—these particles
are generated in a load/unload (cyclic) environment and is a
6. Filter Elements
typical failure mode for rolling element bearings and gears.
6.1 Filter elements may be broadly classified as either
Particles are generated when subsurface cracks, generated by
reusable or disposable. Prior to processing a filter element, it
thesignificantsub-surfaceshearstressassociatedwithHertzian
should be understood whether the element is disposable or
contact stresses, propagate to a point where a spall is liberated
reusable so that appropriate processing techniques can be
fromtheloadsurface.Theseparticlescanbetensofmicronsup
applied.
to millimetres in length. Particles may show evidence of the
machined load-bearing surface on one face and a rough
6.2 This is to ensure disposable elements are not inadver-
crystallinesurface(wherethecrackpropagated)onthereverse.
tently reused following extraction of debris.
Particles may be rolled and reworked by subsequent rolling
6.3 Reusable filter elements are typically made from sin-
elements or gear teeth and may then appear as a flattened flake
tered metal or woven metal fiber (mesh), but can also employ
with characteristic radial cracking from the edges and a
other media types.
fissured or crazed edge. Particles are hard and brittle, not
6.3.1 If a reusable filter is to be reinstalled into a machine,
deformable without cracking when load is applied.
then the filter element should be treated as a serviceable part,
3.2.15 scale bar, n—a reference measurement embedded
and as such the following observed:
into or applied on an image to enable scaling of other objects
6.3.1.1 Anyprocess,solvent,etc.usedtoextractweardebris
present in that image. The units of measurement must be
mustbeinaccordancewiththeapprovedmaintenancemanual.
clearly presented with the scale bar.
This will typically include a predefined cleaning and drying
3.2.16 striations, n—fine parallel lines or scores on a par-
procedure that must be conducted prior to reinstalling the
ticle surface.
element. Failure to follow approved procedures could result in
3.2.17 slurry, n—mixture of debris suspended in solvent.
degraded filter performance or contamination of the oil system
3.2.18 wear debris analysis, n—the analysis of metallic
with residual cleaning solvent, or both. Some filters may
debris with particular emphasis on size, count, morphology,
requireabubblepointtest(forexample,TestMethodsF316)to
and composition. May also provide some indication of the
confirm the integrity prior to reinstallation.
criticality.
6.3.1.2 If the approved maintenance manual does not
3.2.19 wear particle atlas, n—a compilation of high reso- specify a suitable method for cleaning the reusable filter that
lutionimagesshowingthekeyfeaturesofthedifferenttypesof sufficiently extracts debris for analysis, then the filter element
pure wear debris (fatigue, adhesive, and abrasive). manufacturer should be consulted to determine an appropriate
D7898 − 14 (2020)
method. Ultrasonic extraction in particular can cause visually 6.5.3.1 Filter Element—Remove filter element and place it
undetectable damage to some reusable filter media. vertically in a clean tray, allow residual oil to drain off for
6.3.1.3 The number of times a filter can be cleaned and approximately 1 min. The drained filter element may then be
reused should also be determined. Some reusable filter ele- preparedforweardebrisextraction.Ifdebrisextractionistobe
ments will only tolerate a finite number of cleaning processes done off site (for example, in a laboratory) package filter (see
before becoming degraded beyond acceptable performance Note 1), indelibly label, and dispatch to the analyzing labora-
limits. Where a maximum permissible number of cleans is tory with documentation relevant to the parent machine (ma-
determined,thisneedstobetracked(forexample,engravingan chine serial number, aircraft tail number, date the filter was
inspectionmarkingonthefilterelementeachtimeitundergoes removed, hours filter installed, location, and reason for re-
cleaning/debris removal). moval). If debris extraction is to be done on site, carry out
extraction using manual or automated method as appropriate.
6.4 Disposable filters are intended for single use and should
not be reused once removed from the machine for FDA.
NOTE 1—When sending filter elements or oil samples, they must be
packagedinaccordancewithlocalrulestoensureoildoesnotleakoutand
6.4.1 The specific filter media in these types of filter varies
to also prevent ingress of foreign debris. Typically this involves placing
but are typically made of one of the following materials:
the item in two containers and placing absorbent material in the box
(1)Cellulose fiber
around the bagged items.
(2)Fiberglass
6.5.3.2 Residual Oil—Inspect the residual oil drained from
(3)Ceramic
the filter element itself and residual oil in the filter bowl
6.4.2 As disposable filters are not reinstalled in machinery,
assembly (if applicable). If debris is visible, then collect the
any method that best extracts debris may be used.
residual oil/debris in a clean bottle, indelibly label the bottle,
6.4.3 Where screw-on cartridges are used, if manually
anddispatchwiththefilterelementtotheanalyzinglaboratory.
cleaning, the cartridge outer casing may need to be cut open to
If no debris is present, then dispose of residual oil appropri-
reveal the filter element.
ately. Debris greater than 100 µm can appear as scintillating
6.4.3.1 This is best achieved using a dedicated filter cutter
particles in the oil when backlit illumination is applied (for
(Fig. 1) that uses a continuous cutting action similar to a
example, flashlight).
domestic can opener; sawing should be avoided as it generates
substantial swarf that can become intermixed with the true
7. Extraction of Filter Debris
wear debris. Note, there is still the possibility of swarf
contamination from the casing material.
7.1 The exact process to best extract filter debris is some-
what dependant on the filter type, equipment and personnel
6.5 The procedure by which a filter element is removed
available. If filter debris is to be robustly trended, the estab-
fromasystemandpreparedforweardebrissamplingshouldbe
lished method for debris extraction should be applied consis-
defined and consistent.
tently and subject to process controls. Semi and fully auto-
6.5.1 Oftenasignificantamountofoilcontainingdebriscan
mated filter debris extraction equipment can offer significant
drain from the filter element when removed or may remain in
benefits in this regard.
the filter bowl/housing assembly.
6.5.2 The quantity of residual oil will be different for each
7.2 The manual extraction method involves simple equip-
specific system filter assembly design; therefore, it is recom-
ment that can effectively extract debris from a filter element
mended a specified procedure be developed for each type as
and is particularly useful where machinery is employed in
appropriate.
remote localities.
6.5.3 Thefollowingfilterremovalprocessisrecommended:
7.2.1 The manual extraction process is shown in AnnexA1.
7.2.2 The following items (or their equivalent) will be
required to manually extract debris from a filter element:
7.2.2.1 A sealable robust (impact resistant) polypropylene
cylindrical bottle;
7.2.2.2 Rubber stoppers to plug the filter element clean oil
exit port(s);
7.2.2.3 A suitable solvent. This will vary depending on the
oil used.
7.2.2.4 A flusher bottle or tweezers to enable persistent
debris to be removed from the element.
7.2.3 When this method and its associated equipment are
used for filter elements from different machines, a strict
cleaning regime is essential to prevent possible cross-
contamination and subsequent false attribution of FDAresults.
7.2.3.1 To achieve this, all equipment should be cleaned
prior to and following each filter debris extraction (that is, a
double clean). In particular, the sealable bottle should be
cleaned using a small quantity of clean solvent followed by a
FIG. 1 Example of a Filter Element Cutter thorough wipe out using lint-free disposable cloth.
D7898 − 14 (2020)
7.2.3.2 Appropriate personal protective equipment must 8.2 A filter patch is a piece of filter material of known
also be used when handling solvents. porosity that will capture particulate of greater size than the
rated porosity. Filter patches come in a variety of sizes;
7.3 Ultrasonicagitationisaneffectivemethodforextracting
however, typically the filter patches are either 47 mm diameter
debris from a filter element. This method requires the follow-
or 25 mm diameter. Forty seven millimetre diameter patches
ing equipment:
are recommended for FDA.
(1)Ultrasonic bath,
8.2.1 Nylon filter patches in the 20µm to 100 µm range
(2)Clean solvent, and
have been found to be effective at capturing significant debris,
(3)A container to house the element and contain the
while allowing finer particles, particularly oil degradation
subsequent slurry.
products, to pass through and prevent filter patch clogging.
7.3.1 The following provides the recommended minimum
8.2.2 Thefilterpatchporositymayneedtobeacompromise
processing time for ultrasonic bath extraction:
ofsignificantparticleisolationandpreventionofclogging;this
7.3.1.1 Five minutes where entire element is submerged in
canvaryfromsystemtosystemandshouldbedeterminedfrom
solvent and exposed to ultrasonic waves, followed by a further
fleet experience for the actual system to be monitored.
five minutes with the element inverted (vertical orientation).
8.2.3 In general, the following filter patch porosities are
7.3.1.2 Fiveminutespersidewhereonlyhalfoftheelement
recommended to ensure significant debris is retained:
can be submerged in solvent and exposed to ultrasonic waves
(a)60 µm nylon filter patch is for lubricant filter analysis,
(horizontal orientation).
and
7.3.2 Some reusable filter elements cannot be cleaned using
(b)20 µm nylon filter patch for hydraulic filter analysis.
ultrasonic baths as damage to the element filter media may
Sequential filtering of the slurry in decreasing porosity (for
result.
example, 20 µm followed by 5 µm) can also be used to ensure
7.3.2.1 Instead of ultrasonic extraction, an alternative
fine debris is captured. This is typically only required in
method known as sub-sonic (or electro-sonic) extraction may
hydraulic systems where fine component tolerances exist.
be employed.
8.2.4 Wherehighparticulateconcentrationisencountered,a
7.4 Removable diagnostic layers are available that can
vacuum pump (hand or power) may be required to draw the
provideaneffectivemeansofremovingsignificantdebrisfrom
slurry through the filter patch.
a filter element.
8.2.5 Filter patches finer than 20 µm are generally not
7.4.1 Theremovableouterlayerissacrificialandprovidesa
recommended for FDA for the following reasons:
rapid method of extraction.
8.2.5.1 The severity of component wear is approximately
proportional to particle size.
7.5 Typicalfilterelementdesignsuseafoldedpleatelement
8.2.5.2 Experience has shown that generally particles less
design.Duetotheflowpaththroughtheelement,thisresultsin
debris collecting in the valleys of the pleats. Some filter media than approximately 100 µm captured in the filter are of limited
practical use when diagnosing incipient wear-related failures.
typescantrapdebrisinthesevalleys,whichtheabovemethods
cannot always remove. This is particularly the case for ele- 8.2.5.3 However,forsomesystems,itmaybeappropriateto
analyze smaller particles in order to detect failure modes that
ments that do not have metallic wire gauze over the filtration
media. primarily produce “fines;” this is contingent on having equip-
ment available to analyze such small particles as manual
7.5.1 In this case, debris may be extracted by manually
forcingapartadjacentpleatsandusingtweezers,etc.toremove separation of individual particles is impractical.
large debris. 8.2.5.4 Normal non-metallic filter debris (oil degradation
products, sand, grit, etc.) have a propensity to rapidly clog
7.5.2 The filter media can also be removed by circumferen-
tially cutting through the filter media top and bottom with a these fine filter patches and obscure relevant wear particles by
overlaying.
sharp instrument, removing, and flattening out the filter media.
Annex A2 shows this process. 8.2.5.5 Where fine filter patches are made of cellulose, they
can be extremely brittle and removing debris for further
7.5.3 Oncethemediaisremoved,debriscanbeextractedby
immersion in solvent and application of ultrasonic agitation. analysis extremely difficult.
7.5.4 In general, sectioning of filter elements is time con-
8.3 Some equipment can extract debris automatically and
suming and should only be done if necessary or an in-depth
then quantify the size of ferrous and non-ferrous debris for
analysis for a failure investigation is required.
trending.
7.5.5 Careshouldbetakentoensuredebrisgeneratedbythe
8.3.1 The output data from this type of instrument is via an
cutting of the filter element is not mistakenly analyzed as wear
inductive wear debris sensor (see Practice D7685).
debris.
8.3.2 The following particle size bins are recommended:
7.5.6 The filter manufacturer should be consulted prior to
8.3.2.1 Ferrous:
cutting any filter media to identify any hazards associated with
(1)100µm to 250 µm
the filter media.
(2)250µm to 500 µm
(3)500µm to 1000 µm
8. Preparation of Extracted Debris
(4)1000+ µm
8.1 Once the debris has been extracted and contained in a 8.3.2.2 Non-ferrous:
slurry, it must be captured to enable analysis to take place. (1)500µm to 1000 µm
D7898 − 14 (2020)
(2)1000+ µm 8.4.2.6 Care should be taken to avoid contacting the tool
8.3.3 After passing through the inductive sensor, the debris with the surface of the filter patch as this can cause non-
isdepositedonafilterpatchtoallowfurtherelementalanalysis magnetic particles to be inadvertently collected via static or
if required. adhesion.
8.3.4 Some equipment also incorporates elemental analysis
8.4.2.7 For this method to work effectively, the filter debris
capability.
should have no residual oil and must be completely dry. If
residual oil is suspected, then the filter patch may be rewashed
8.4 Since the vast majority of load bearing elements of
using an appropriate solvent and dried.
machinery are made from various alloy steels, the extraction
8.4.2.8 Todryafilterpatch,eitherplaceitinanovenatlow
and quantification of ferrous debris is a very useful step,
temperature (40°C to 60°C) or allow to air dry.Alternatively,
particularly if equipment to quantify ferrous debris (inductive
place the filter patch under a high wattage lamp (250W
sensor) is not available.
minimum) until dry.
8.4.1 Either a wet or dry method can be used for extracting
ferrous debris from the extracted slurry. Both use a magnet to
8.5 The wet method involves externally offering a magnet
attract the ferrous debris and then deposit it on a separate
(with a magnetic strength of no less than 400 Gauss) to the
receptacle for further analysis.
slurry external to the container (usually a glass beaker) and
8.4.2 Thedrymethodinvolvespassingamagnetictoolover
then pour the remaining solvent slurry out while holding the
theparentfilterpatchinordertoattractferrousdebrisoutofthe
magnet in place; the ferrous debris will remain in the beaker
bulk debris.
and can then be extracted onto a dedicated filter patch.
8.4.2.1 One of the simplest tools consists of a permanent
8.5.1 Alternatively, the magnetic tool in its sheath can be
magnet inner stem that fits into an outer non-magnetic sheath
passed through the slurry until all ferrous debris is attracted to
(Fig. 2).
it.
8.4.2.2 The sheath tip is typically made of non-magnetic
8.5.2 The magnetic tool is then removed from the slurry,
polymer.Insertingthestemintothesheathmakesthesheathtip
rinsed with solvent, and the magnet withdrawn allowing the
appear magnetic and enables debris to be attracted. Retracting
ferrous debris to be deposited in a suitable receptacle.
the stem turns the tool off and allows the extracted ferrous
8.6 Due to the size range of significant particles assessed in
debris to be deposited in a separate receptacle.
FDA (100µm to 1000+ µm range), static can influence the
8.4.2.3 Alternatively a hand-held electro-magnet can be
analysis.
used.
8.6.1 In particular, static can cause non-ferrous particles to
8.4.2.4 Toolsusedforthistechniqueshouldhaveamagnetic
inadvertently adhere to the sleeved magnetic tool during
field strength of approximately 400 Gauss or greater.
extraction of the ferromagnetic debris.
8.4.2.5 Whilst the exact height that the tool is passed over
thefilterpatchisnotcritical,itisrecommendedthatthetoolbe 8.6.2 Without access to elemental analysis, non-ferrous
particles could be erroneously counted as ferrous. To avoid
within 3mm to 7mm from the filter patch surface.
FIG. 2 Example of Sheathed Magnetic Tool
D7898 − 14 (2020)
this,itisrecommendedthatisopropylalcoholswabsbeusedto recommended that when using this type of instrument, a
cleanthesleevedmagnetictool(orelectromagnet)andarethen consistent volume of oil and sample/instrument interface area
allowed to dry thoroughly before use. (that is, sample bottle diameter) are used.
8.6.3 Excessive rubbing of the tool tip should be avoided if
9.5.3.5 Whereaninductiveinstrumentdisplaystheoutputin
static is to be avoided.
terms of a physical unit (for example, mg or ppm), the results
should be annotated in reports as inferred (for example, mg
9. Analysis of Filter Debris (inferred), or mg* with a footnote to that effect). This clearly
discriminates between physically measured mass and induc-
9.1 The analysis of debris from a filter can be very time
tively inferred mass.
consumingifusingmanualtechniques;however,thefollowing
9.5.3.6 Some instruments present the results in terms of
guidelines are recommended to efficiently gain meaningful
non-dimensionalnumberstoavoidanyconfusionwithphysical
results.
units; however, these units tend to be less intuitive.
9.2 Some equipment man
...