ASTM D7596-10
(Test Method)Standard Test Method for Automatic Particle Counting and Particle Shape Classification of Oils Using a Direct Imaging Integrated Tester
Standard Test Method for Automatic Particle Counting and Particle Shape Classification of Oils Using a Direct Imaging Integrated Tester
SIGNIFICANCE AND USE
This test method is intended for use in analytical laboratories including on-site in-service oil analysis laboratories. Periodic sampling and analysis of lubricants have long been used as a means to determine overall machinery health. Atomic emission spectroscopy (AES) is often employed for wear metal analysis (Test Methods D5185 and D6595). A number of physical property tests complement wear metal analysis and are used to provide information on lubricant condition (Test Methods D445, D2896, D6304, and D7279). Molecular spectroscopy (Practice E2412) provides direct information on molecular species of interest including additives, lubricant degradation products and contaminating fluids such as water, fuel and glycol. The direct imaging integrated tester provides complementary information on particle count, particle size, particle type, and soot content.
Particles in lubricating and hydraulic oils are detrimental because they increase wear, clog filters and accelerate oil degradation.
5.3 Particle count may aid in assessing the capability of a filtration system to clean the fluid, determine if off-line recirculating filtration is needed to clean the fluid, or aid in the decision whether or not to change the fluid.
5.4 An increase in the concentration and size of wear particles is indicative of incipient failure or component change out. Predictive maintenance by oil analysis monitors the concentration and size of wear particles on a periodic basis to predict failure.
5.5 High soot levels in diesel engine lubricating oil may indicate abnormal engine operation.
SCOPE
1.1 This test method covers the determination of particle concentration, particle size distribution, particle shape, and soot content for new and in-service oils used for lubrication and hydraulic systems by a direct imaging integrated tester.
1.1.1 The test method is applicable to petroleum and synthetic based fluids. Samples from 2 to 150 mm2/s at 40°C may be processed directly. Samples of greater viscosity may be processed after solvent dilution.
1.1.2 Particles measured are in the range from 4 μm to ≥ 70 μm with the upper limit dependent upon passing through a 100 μm mesh inlet screen.
1.1.3 Particle concentration measured may be as high as 5,000,000 particles per mL without significant coincidence error.
1.1.4 Particle shape is determined for particles greater than approximately 20 µm in length. Particles are categorized into the following categories: sliding, cutting, fatigue, nonmetallic, fibers, water droplets, and air bubbles.
1.1.5 Soot is determined up to approximately 1.5 % by weight.
1.1.6 This test method uses objects of known linear dimension for calibration.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation:D7596 −10
StandardTest Method for
Automatic Particle Counting and Particle Shape
Classification of Oils Using a Direct Imaging Integrated
Tester
This standard is issued under the fixed designation D7596; 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.
1. Scope 2. Referenced Documents
1.1 This test method covers the determination of particle 2.1 ASTM Standards:
concentration, particle size distribution, particle shape, and D445Test Method for Kinematic Viscosity of Transparent
soot content for new and in-service oils used for lubrication and Opaque Liquids (and Calculation of DynamicViscos-
and hydraulic systems by a direct imaging integrated tester. ity)
1.1.1 The test method is applicable to petroleum and syn- D2896TestMethodforBaseNumberofPetroleumProducts
thetic based fluids. Samples from 2 to 150 mm /s at 40°C may by Potentiometric Perchloric Acid Titration
be processed directly. Samples of greater viscosity may be D4057Practice for Manual Sampling of Petroleum and
processed after solvent dilution. Petroleum Products
1.1.2 Particles measured are in the range from 4 µm to≥ 70 D4175 Terminology Relating to Petroleum, Petroleum
µmwiththeupperlimitdependentuponpassingthrougha100 Products, and Lubricants
µm mesh inlet screen. D4177Practice for Automatic Sampling of Petroleum and
1.1.3 Particle concentration measured may be as high as Petroleum Products
5,000,000 particles per mL without significant coincidence D5185TestMethodforDeterminationofAdditiveElements,
error. Wear Metals, and Contaminants in Used Lubricating Oils
1.1.4 Particle shape is determined for particles greater than and Determination of Selected Elements in Base Oils by
approximately 20 µm in length. Particles are categorized into Inductively Coupled Plasma Atomic Emission Spectrom-
the following categories: sliding, cutting, fatigue, nonmetallic, etry (ICP-AES)
fibers, water droplets, and air bubbles. D5967Test Method for Evaluation of Diesel Engine Oils in
1.1.5 Soot is determined up to approximately 1.5 % by T-8 Diesel Engine
weight. D6304Test Method for Determination of Water in Petro-
1.1.6 This test method uses objects of known linear dimen- leum Products, Lubricating Oils, and Additives by Cou-
sion for calibration. lometric Karl Fischer Titration
D6595Test Method for Determination of Wear Metals and
1.2 The values stated in SI units are to be regarded as
ContaminantsinUsedLubricatingOilsorUsedHydraulic
standard. No other units of measurement are included in this
FluidsbyRotatingDiscElectrodeAtomicEmissionSpec-
standard.
trometry
1.3 This standard does not purport to address all of the
D7279Test Method for Kinematic Viscosity of Transparent
safety concerns, if any, associated with its use. It is the
and Opaque Liquids by Automated Houillon Viscometer
responsibility of the user of this standard to establish appro-
E2412Practice for Condition Monitoring of In-Service Lu-
priate safety and health practices and determine the applica-
bricants by Trend Analysis Using Fourier Transform
bility of regulatory limitations prior to use.
Infrared (FT-IR) Spectrometry
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee For referenced ASTM standards, visit the ASTM website, www.astm.org, or
D02.96 on In-Service Lubricant Testing and Condition Monitoring Services. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved May 1, 2010. Published August 2010. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D7596–10. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7596−10
FIG. 1Schematic of Direct Imaging Integrated Tester*
G40Terminology Relating to Wear and Erosion 3.1.4 particle size, circular diameter, µm, n—diameter of a
circlewithanareaequivalenttotheprojectedareaofaparticle
2.2 ISO Standards:
passing through the direct imaging integrated tester flow cell.
ISO 12103-11997 Road vehicles -- Test dust for filter
evaluation -- Part 1: Arizona test dust
3.1.5 soft particles, n—particles present in the sample that
ISO 4406Hydraulic fluid power – Fluids – Method for
arerelatedtoundissolvedoiladditivesoradditiveby-products.
coding level of contamination by solid particles
Withoutdilution,atroomtemperaturetheseparticlesarelikely
2.3 SAE Standards:
tobecountedbyanopticalparticlecounterinasimilarmanner
SAE AS 4059 Aerospace Fluid Power – Cleanliness Clas- to dirt and wear metal particles, air bubbles, and free water
sification for Hydraulic Fluids
droplets. They are not considered contaminants as they are
either purposefully left undissolved, or are not harmful to the
3. Terminology
fluid system, or both.
3.1 Definitions of Terms Specific to This Standard:
3.1.6 soot, n—in internal combustion engines, sub-micron
3.1.1 contaminant particles, n—particles introduced from
size particles, primarily carbon, created in the combustion
anextraneoussourceintothelubricantofamachineorengine.
chamber as products of incomplete combustion. D4175
3.1.2 ISO Codes, n—standardmethodforcodingthelevelof
3.1.7 wear, n—damage to a solid surface, usually involving
contamination by solid particles. This code simplifies the
progressive loss or displacement of material, due to relative
reporting of particle count data by converting the number of
motion between that surface and a contacting substance or
particles per mL into three classes covering ≥ 4 µm, ≥ 6 µm,
substances. D4175, G40
and≥14µm.ISO4406classificationsareusedasanoptionto
3.1.8 wear particles, n—particles generated from wearing
report results for this test method.
surfaces of a machine or engine.
3.1.3 new oil, n—oil taken from the original manufacturer’s
packaging, prior to being added to the machinery. E2412
4. Summary of Test Method
4.1 Lubricant samples are acquired periodically from a
machine or engine being monitored.
Available from International Organization for Standardization (ISO), 1, ch. de
la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
4.2 Particlesarecountedandsizedbydrawingoilthrougha
www.iso.ch.
flow cell. See Fig. 1. The cell is illuminated by a pulsed laser.
AvailablefromSAEInternational(SAE),400CommonwealthDr.,Warrendale,
PA 15096-0001, http://aerospace.sae.org. The duration of the pulse is sufficiently fast to freeze the
D7596−10
motion of the particles in the cell. The pulse frequency is 30 oil samples with known percentage of soot as determined by
Hz. Images of the particles flowing through the cell are thermal gravimetric analysis in accordance with Test Method
magnified by 4 using a lens between the cell and the CCD D5967, Annex A4.
video chip onto which the images of the particles are focused.
4.12 Condition alerts and alarms, based on trend and level,
Software counts and sizes each particle. Sizing is done by
can be issued for the system being monitored according to
comparison to objects of known linear dimension.The number
particle count, size distribution, types of particles recognized
ofparticlespermLisdeterminedbydividingparticlecountsby
and soot content.
the volume of oil examined. Each image taken corresponds to
a small volume of oil equal to the image area, which is 1600 ×
5. Significance and Use
1200 µm, multiplied by the cell thickness, nominally 100 µm.
5.1 This test method is intended for use in analytical
The actual cell thickness, to the closest µm for each cell, is
laboratories including on-site in-service oil analysis laborato-
provided by the manufacturer and is entered into the software
ries. Periodic sampling and analysis of lubricants have long
for the purpose of calculating the volume of oil examined for
been used as a means to determine overall machinery health.
each sample. The total oil volume examined is the volume per
Atomic emission spectroscopy (AES) is often employed for
image multiplied by the number of images collected.
wear metal analysis (Test Methods D5185 and D6595). A
4.3 The direct imaging integrated tester software performs
number of physical property tests complement wear metal
particle shape recognition of all particles ≥ 20 µm by using a
analysis and are used to provide information on lubricant
neural network.An algorithm sorts particles into the following
condition (Test Methods D445, D2896, D6304, and D7279).
categories: cutting, fatigue, severe sliding, nonmetallic, fibers,
Molecular spectroscopy (Practice E2412) provides direct in-
air bubbles and water droplets.Air bubbles and water droplets
formation on molecular species of interest including additives,
≥ 20 µm are eliminated from the particle counting results.
lubricant degradation products and contaminating fluids such
Further information regarding wear particle shape recognition
as water, fuel and glycol. The direct imaging integrated tester
may be found in Anderson’s report. .
providescomplementaryinformationonparticlecount,particle
4.4 Nonmetallic particles are recognized by their partial
size, particle type, and soot content.
transparency. Nonmetallic particles, in thin sections, do not
5.2 Particles in lubricating and hydraulic oils are detrimen-
block light, as do metallic particles. Therefore, particles
tal because they increase wear, clog filters and accelerate oil
displaying transparent interior pixels are classified as nonme-
degradation.
tallic. Nontransparent particles are sorted into one of three
metallic categories, namely, cutting, sliding, and fatigue. 5.3 Particle count may aid in assessing the capability of a
filtration system to clean the fluid, determine if off-line
4.5 Cuttingwearparticlesarerecognizedbytheirelongated,
recirculating filtration is needed to clean the fluid, or aid in the
curved, or curly shape.
decision whether or not to change the fluid.
4.6 Sliding wear particles are recognized by being longer
5.4 An increase in the concentration and size of wear
than wide, often with straight edges.
particles is indicative of incipient failure or component change
4.7 Fatigueparticlesarerecognizedbybeingmoreorlessas
out. Predictive maintenance by oil analysis monitors the
long as they are wide and often with jagged, irregular edges.
concentration and size of wear particles on a periodic basis to
4.8 Fibers are recognized by their elongated shape and by predict failure.
partial transparency indicating nonmetallic composition.
5.5 High soot levels in diesel engine lubricating oil may
4.9 Air bubbles are dark round circles, either completely
indicate abnormal engine operation.
dark or with small bright centers.
6. Interferences
4.10 Water droplets are dark round circles with large bright
centers. The difference in appearance between air bubbles and
6.1 Dirty environmental conditions and poor handling tech-
water droplets is due to the much different refractive index of
niques can easily contaminate the sample. Care must be taken
each.When present in oil, air bubbles refract much of the light
to ensure test results are not biased by introduced particles.
passing through them away from the direction of transmission,
6.2 Air bubbles < 20 µm may be counted as particles giving
whereas water droplets, having a refractive index more nearly
false positive readings. Air bubbles ≥ 20 µm are recognized
equaltothatofoil,allowmuchofthelightincidentuponthem
and automatically eliminated from the count. Mixing or agi-
to transmit through them to the CCD video chip.
tating the sample introduces air bubbles into the oil, but these
4.11 Soot is measured by performing an optical extinction
readily dissipate with ultra-sonication or vacuum degassing.
measurement with reference to new oil. Absorbance of the
6.3 Water droplets < 20 µm may be counted as particles
laserlightiscalculatedandcalibrationismadetodieselengine
giving false positive readings. If water droplets ≥ 20 µm are
detected in a sample by the direct imaging integrated tester,
there is reason to suspect water droplets < 20 µm are present
Anderson, D.P., Wear Particle Atlas (Revised), Prepared for Advanced Tech-
andhavespuriouslyincreasedparticlecount.Smallamountsof
nology Office, Support Equipment Engineering Department, NavalAir Engineering
water in the sample may be negated by the use of water
Center,Lakehurst,NJ,08733,28June1982,ReportNAEC–92–163,approvedfor
public release, distribution unlimited. masking solvent. See Appendix X1.
D7596−10
6.4 Certain additives or additive by-products that are not the counts from a conventional automated light blockage
fully dissolved in the oil, most notably polydimethylsiloxane particle counter. The metal particles, being solid, will block
defoamant additive, are known to be present as soft particles more light proportional to their size than will transparent
thatarenotcontaminantsinthefluidsystem,butarecountedas particles. Therefore, the light blockage particle counter will
particles by the direct imaging integrated tester. These may be overestimate the size of metallic particles.
negated by use of a diluting solvent. See Appendix X1.
7. Apparatus
6.5 Samples with viscosity greater than approximately 150
7.1 Direct Imaging Integrated Tester, a particle counter and
mm /s at 40°C when processed by the direct imaging inte-
shape recognition instrument consisting of flow through cell,
grated tester at room temperature (approximately 20°C) may
peristaltic pump, inlet screen, pulsed laser diode, magnifying
flow through the tester too slowly causing the same particle to
lens, CCD video chip, software, and readout system.
be imaged twice. This effect may be negated by diluting the
sample with clean solvent to lower viscosity. The tester
7.2 Ultrasonic Bath, an ultrasonic bath having a minimum
softwaremakesprovisionforinputofthedilutionfactorsothat
power density of 4000 W/m . The bath is used to coalescence
particle counts are adjusted and reported for undiluted sample.
and remove air bubbles that were introduced during sample
shaking to homogeneously suspend the particles therein.
6.6 Soot levels above approximately 1.5 % by weight cause
insufficient laser light to reach the CCD video detector. The 7.3 Vacuum Degassing Apparatus, capable of pulling a full
software provides an error message and the sample may be
vacuum on the sample container in a vacuum chamber. The
diluted with clear, particle free oil and reprocessed. The tes
...
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