Designation: D7647 − 10

Standard Test Method for

Automatic Particle Counting of Lubricating and Hydraulic
Fluids Using Dilution Techniques to Eliminate the
Contribution of Water and Interfering Soft Particles by Light
Extinction1
This standard is issued under the fixed designation D7647; 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 priate safety and health practices and determine the applica-
1.1 This test method covers the determination of particle bility of regulatory limitations prior to use.
concentration and particle size distribution in new and in-
service oils used for lubrication and hydraulic purposes. 2. Referenced Documents

1.2 Particles considered are in the range from 4 µm (c) to 200 2.1 ASTM Standards:2
µm (c) with the upper limit being dependent on the specific D4057 Practice for Manual Sampling of Petroleum and
automatic particle counter being used. Petroleum Products
NOTE 1—For the purpose of this test method, water droplets not masked D4177 Practice for Automatic Sampling of Petroleum and
by the diluent procedure are detected as particles, and agglomerated Petroleum Products
particles are detected and reported as a single larger particle. D6786 Test Method for Particle Count in Mineral Insulating
NOTE 2—The subscript(c) is used to denote that the apparatus has been Oil Using Automatic Optical Particle Counters
calibrated in accordance with ISO 11171. This subscript(c) strictly only
2.2 ISO Standards:3

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applies to particles up to 50 µm.
ISO 3722 Hydraulic Fluid Power–Fluid Sample Containers
1.3 Lubricants that can be analyzed by this test method are
–Qualifying and Controlling Cleaning Methods
categorized as petroleum products or synthetic based products,
ISO 4406 Hydraulic Fluid Power–Fluids–Method for Cod-
such as: polyalpha olefin, polyalkylene glycol, or phosphate
ing Level of Contamination by Solid Particles
ester. Applicable viscosity range is up to 1000 mm2/s @ 40°C.
ISO 11171 Hydraulic Fluid Power–Calibration of Automatic
This procedure may be appropriate for other petroleum and
Particle Counters for Liquids
synthetic based lubricants not included in the precision state-
ment.
3. Terminology
1.4 Samples containing visible particles may not be suitable
3.1 Definitions:
for analysis using this test method.
3.1.1 For the purposes of this test method, the following
1.5 Samples that are opaque after dilution are not suitable definitions apply:
for analysis using this test method. 3.1.2 coincidence, n—the presence of more than one particle
1.6 The test method is specific to automatic particle coun- in the sensing zone of a particle analyzer at the same time,
ters that use the light extinction principle and are calibrated causing incorrect sizing and incorrect counting of the particle
according to the latest revision of ISO 11171. present. The coincidence limit of the counter is determined by
the maximum acceptable concentration of particles in the
1.7 The values stated in SI units are to be regarded as
sensing zone and is supplied by the instrument manufacturer.
standard. No other units of measurement are included in this
Refer to Section 3.4 in ISO 11171.
standard.
3.1.3 diluent, n—a solvent listed in Annex A1, Table A1.1,
1.8 This test method does not purport to address all of the
having viscosity less than 10 mm2/s at 40°C that is physically
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
1
This test method is under the jurisdiction of ASTM Committee D02 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee Standards volume information, refer to the standard’s Document Summary page on
D02.96.05 on In-Service Lubricants Particle Counting Practices and Techniques. the ASTM website.
3
Current edition approved July 1, 2010. Published September 2010. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/D7647–10. 4th Floor, New York, NY 10036, http://www.ansi.org.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States

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 D7647 − 10
and chemically compatible with the apparatus used and easily 4.9 Analyze data and conduct validity checks.
soluble at room temperature with the sample lubricant or 4.10 Report results.
hydraulic fluid.
3.1.4 emulsified water, n—water that exists in oil between 5. Significance and Use
the states of fully dissolved and phase-separated. An emulsi-
5.1 This test method is intended for use in analytical
fying agent in the oil causes the two immiscible liquids to
laboratories including onsite in-service oil analysis laborato-
coexist in a heterogeneous mixture.
ries.
3.1.5 free water, n—water that exists in a separate phase in
5.2 Hard particles in lubricating or fluid power systems have
an oil sample. This occurs when the water content of the oil
a detrimental effect on the system as they cause operating
exceeds the water holding capacity of the oil.
components to wear and also accelerate the degradation of the
3.1.6 interfering soft particles, n—an undissolved, dispersed oil. Hard particles in the oil originate from a variety of sources
material (such as an additive) within an oil blend or substance including generation from within an operating fluid system or
that is formed during the service life of an oil blend. contamination, which may occur during the storage and han-
3.1.6.1 Discussion—When these substances are present in a dling of new oils or via ingress into an operating fluid system.
sample and not completely solubilized, they are likely to be
counted by an optical particle counter in a similar manner to 5.3 High levels of contaminants can cause filter blockages
dirt and wear metal particles, air bubbles, and free water and hard particles can have a serious impact on the life of
droplets. pumps, pistons, gears, bearings, and other moving parts by
accelerating wear and erosion.
3.1.7 ISO Codes, n—a standard classification for coding the
level of contamination by solid particles. 5.4 Particle count results can be used to aid in assessing the
3.1.7.1 Discussion—This code simplifies the reporting of capability of the filtration system responsible for cleaning the
particle count data by converting the number of particles per fluid, determining if off-line recirculating filtration is needed to
mL into three classes covering $4 µm (c), $6 µm (c) and $14 clean up the fluid system, or aiding in the decision of whether
µm (c). ISO 4406 classifications are used as an option to report or not a fluid change is required.
results for this test method. 5.5 To accurately measure hard particle contamination
3.1.8 particle size, µm (c), n—diameter of a circle with an levels, it is necessary to negate the particle counts contributed

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area equivalent to the projected area of a particle passing by the presence of small levels of free water. This method
through the detecting cell in accordance with ISO 11171. includes a process by which this can be accomplished using a
water-masking diluent technique whereby water droplets of a
3.1.9 particle size cumulative count, n—total number of
size below the target level are finely distributed.
particles with sizes greater than a specified particle size (for
example, $4 µm (c), $6 µm (c), $10 µm (c), $14 µm (c), $21 5.6 Certain additives or additive by-products that are semi-
µm (c), $38 µm (c), etc.). insoluble or insoluble in oil, namely the polydimethylsiloxane
defoamant additive and oxidation by-products, are known to
NOTE 3—All particle counts are expressed on per 1 mL basis.
cause light scattering in automatic particle counters, which in
3.1.10 soot-in-oil, n—a sub-micron particulate product of turn causes falsely high counts. These and similar materials are
incomplete combustion commonly found in in-service diesel commonly termed “soft particles” (see 3.1.6) and are not
engine crankcase oil. known to directly increase wear and erosion within an operat-
3.1.11 water-masking diluent, n—a particular kind of di- ing system. The contribution of these particles to the particle
luent capable of dissolving otherwise immiscible substances size cumulative count is negated with this method.
such as water or soft particles in the sample lubricant or 5.7 The use of dilution in this test method counteracts
hydraulic fluid. See Annex A1, Table A1.1. viscosity effects for highly viscous oils that impact the accu-
racy of automatic optical particle counting results.
4. Summary of Test Method
4.1 Inspect sample. 6. Interferences
NOTE 4—This section is consistent with the interferences described in
4.2 Agitate sample. Test Method D6786.
4.3 Obtain aliquot from homogeneous sample if not diluting 6.1 Dirty environmental conditions and poor handling tech-
in original container. niques can easily contaminate the sample or test specimen, or
4.4 Dilute with appropriate diluent for the sample type. both. Care shall be taken to ensure test results are not biased by
introduced particles.
4.5 Agitate diluted sample.
6.2 Air bubbles in the oil may be counted as particles giving
4.6 Degas sample. false positive readings. Mixing or agitating the sample intro-
4.7 Begin testing within 90 s (or repeat agitation and duces bubbles into the oil, but these readily dissipate with
degassing). sonication or vacuum degassing.
4.8 Obtain particle counts in triplicate (for sample and 6.3 Suspended or free water in the oil will generally be
method blank). counted as particles.

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NOTE 5—Free or emulsified water interference presented can be 7.5 Liquid Dispensers, fitted with 0.8 µm or finer filter.
negated by using the water-masking diluent as described in this test
method. 7.6 Volumetric Pipette and Bulb, if volumetric dilution or
fluid transfer with a pipette is desired. Pipettes made of
6.4 Excessive concentrations of particles in the oil will
graduated glass or disposable polyethylene. Any glassware
cause coincidence or electronic saturation errors, or both.
used shall be cleaned and verified in accordance with ISO
Limits are determined by ISO 11171 and are generally supplied
3722.
by the instrument manufacturer. These errors may be avoided
by increasing the dilution ratio with the diluent used in this test 7.7 Density Meter, with an accuracy of 0.01 g/cm3, if the
method. mass dilution method is used.
6.5 Odd-shaped particles and fibers may be classified with 7.8 Filter Apparatus, for filtering the diluent. There is no
incorrect calculated particle size, depending on their orienta- requirement for the apparatus itself but it shall be capable of
tion as they pass through the sensing zone of the instrument. producing acceptably clean diluent as necessary. Take appro-
6.6 Dye-in-oil is used by some lubricant manufacturers to priate safety precautions in handling low flash materials.
distinguish certain lubricant types or brands. It is unusual for 7.9 Vacuum Degassing Apparatus, capable of pulling full
that dye to have a discernible impact on particle count data. vacuum on the sample container in a vacuum chamber (per
Nonetheless, it is worthwhile to evaluate possible interferences 12.4.1) or syringe degassing port (per 12.4.3) within time limit
for dye-in-oil by testing a sample of filtered, dyed, lubricant. If specified.
the automatic particle counter yields unusual results or if it 7.10 Glassware, any glassware used shall be cleaned and
reports an optical warning message, then this may be an verified in accordance with ISO 3722.
indication of this type of interference.
7.11 Sample Container, a container used for collecting the
6.7 Excessive soot-in-oil is an interference that makes it neat sample per 9.1 and 9.2, or for diluting sample specimens.
impractical to test in-service diesel engine lubricants, espe- 7.11.1 Sample containers shall not be reused.
cially when soot level exceeds 1 %. This is not normally a 7.11.2 Recommended containers are cylindrical specimen
problem for natural gas and gasoline engine oils. However bottles (or jars) typically made of polypropylene, polystyrene,
heavy duty diesel engine oils typically produce excessive soot PET, or glass with nominally flat bottoms, fitted with a suitable
for most automatic particle counters. The coincident, opaque, non-shedding threaded cap.
soot particles reduce light transmission and produce very high

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7.11.3 The dimensions and capacity of sample containers
false particle counts. depends on specimen requirements and APC design. Sample
6.8 Solid lubricants, such as molybdenum disulfide or containers often have an approximate capacity of 125 mL.
graphite are used in some lubricating oils, especially for However individual specimen requirements and APC design
extreme pressure applications. These materials are typically may call for substantially smaller or much larger sample
used at levels high enough to render the fluid opaque or to containers.
cause coincidence errors due to high particle concentrations in 7.11.4 After performing any cleaning procedures, the
the detector. Even if these factors can be overcome with sample containers shall meet the cleanliness criteria of contrib-
sufficient dilution, increases in particle counts are difficult to uting less than 1 % of the total particles expected in the
determine with adequate precision due to the inherently high cleanest sample.
particle counts in these fluids. 7.11.5 Sample containers shall be compatible with fluid and
6.9 Specimen bottles shall not be reused. This is a source of able to withstand the temperature of the fluid when collecting
cross-contamination interference. the sample. Sample containers with certified cleanliness levels
(for example, “ultra clean”) may be used to collect samples for
7. Apparatus particle counting.
7.1 Liquid Automatic Particle Counter (APC), liquid optical 7.12 Specimen Bottle, or sample specimen bottle, a sample
particle counter based on the light extinction principle. The container used for diluting at least a portion of a sample. A
instrument shall be capable of recording the size and number of specimen bottle shall meet the same criteria as the sample
particles as they pass across the detector. The particle counter container (7.11.1-7.11.5).
shall include a sampling apparatus that automatically delivers 7.13 Filters, to be used with filter apparatus (see 7.8).
a predetermined volume of specimen at a controlled flow rate Recommended filters are cellulose or polycarbonate with a 0.8
to the sensing zone of the analyzer. µm or smaller pore size.
7.2 Analytical Balance, for mass dilution, calibrated, with a 7.14 Disposable, Single-Use Syringes, uncontaminated and
resolution of 100 mg. directly taken from individually sealed pouches are sometimes
7.3 Mechanical Shaker, paint shaker, table shaker, or other used instead of a sample inlet tube to deliver samples to
mechanical device to vigorously agitate sample containers. automatic particle counters.
7.4 Ultrasonic Bath, rated at 3000 to 10 000 W/m2. This
bath aids in the removal of air bubbles generated in the sample 8. Reagents and Materials
during the agitation process while also working to suspend 8.1 Calibration Fluid, a suspension of ISO Medium Test
particles in the sample and slow the settling process. Dust in oil or hydraulic fluid, using either a primary sample

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obtained directly from NIST (SRM 2806) or a secondary ing lower dilution ratio is often evidenced when ISO $4 µm (c)
sample prepared in accordance to ISO 11171 and at least is equivalent to ISO $6 µm (c) indicating unusually small
secondary traceable to NIST. difference in particle counts between these size ranges.
8.2 Diluent, from list in Annex A1, Table A1.1, shall be 9.6.3 For the temporary precision statement of reproducibil-
filtered to ensure it contributes less than 12.5 % of the total ity reported in Section 14, a mass dilution ratio of 25 6 2 %
particles counted in the diluted sample tested according to this sample to 75 6 2 % diluent was consistently used and the
method. diluent was a blend of 33 6 2 % lamp oil with 67 6 2 %
dipropylene glycol n-propyl ether (DPnB) for water-masking.
8.3 Water-Masking Diluent,4from Annex A1, Table A1.1, is
either a volumetric mixture of toluene and 2-propanol (also 9.7 Take appropriate safety precautions when collecting
called isopropanol or isopropyl alcohol), typically in 75:25 samples.
proportions, or dipropylene glycol n-propyl ether.5 The water-
masking diluent shall be filtered to ensure it contributes less 10. Calibration and Verification
than 12.5 % of the total particles counted in the diluted sample 10.1 Calibration:
tested according to this method. 10.1.1 Calibration of the APC shall be done with an
undiluted NIST-traceable calibration fluid in accordance with
9. Sample Collection and Handling ISO 11171.
9.1 Unless otherwise specified, take a representative sample 10.1.2 Calibration of the APC shall be done within the
in accordance with Practices D4057, D4177, or other compa- timeframe indicated by the particle counter manufacturer, or at
rable sampling practices using a clean and appropriate sample least annually if no frequency is specified. Refer to reference in
container. Containers previously holding a sample or any other 10.2.1 to establish calibration frequency.
type of fluid are not considered appropriate containers. 10.2 Verification:
9.2 Ensure that enough sample is collected to perform all 10.2.1 Verify that the APC is holding its calibration by
analysis methods of interest. The container shall not be filled analyzing a primary or secondary calibration fluid allowing for
beyond 80 % of its total capacity to allow volume for sufficient sample-to-sample variation outlined in Annex A2, Table A2.1
agitation. and allowing for calibration fluid batch-to-batch variation.
10.2.2 Verify that the APC is providing internally consistent
9.3 Label the sample according to the expectations of the

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results by analyzing diluent looking for expected results and
analyzing laboratory, including oil type at a minimum.
allowing for sample-to-sample variation outlined in Annex A2,
9.4 Upon receipt at the analyzing laboratory, the sample Table A2.1.
shall be inspected and any non-standard conditions noted. This 10.2.3 Verification checks are recommended on a quarterly
includes inappropriate container, overfilled container, visible basis for instruments analyzing multiple samples regularly
particulates, and free water. Recommend a re-sample if inap- (such as weekly). Checks shall also be performed if an
propriate container or overfilled container is noted. instrument has not been used for over three months or if the
9.5 Determine whether water-masking diluent (see 6.3) or particle counter has been altered in such a way that could
diluent (non water-masking) is to be used for dilution based on impact its calibration.
indication or not of emulsified water-in-oil.
11. Preparation of Apparatus
9.6 Determine the desired dilution ratio. The dilution ratio
may vary depending on the viscosities of the sample and the 11.1 The APC shall be set up according to the instrument
diluent and the range of viscosities that can be accommodated manufacturer’s operating manual.
by the APC. 11.2 Ensure that the ISO 4406 mode of operation is selected
9.6.1 A dilution ratio of ~50 % sample to ~50 % diluent is and displayed. If the APC has printing or electronic data output
acceptable for most applications although a smaller sample-to- capabilities, ensure those are also set to ISO 4406.
diluent ratio is often used.
9.6.2 If the sample is very dark or high particulate contami- 11.3 Set the flow-rate to the setting at which the APC was
nation is suspected, a lower sample to diluent dilution ratio is calibrated.
suggested. This sort of excessively high contamination deserv- 11.4 If the APC is capable of running a pre-set program, set
the APC to flush 10 to 25 mL of sample prior to analysis, then
run three analyses consecutively of at least 5 mL per run. If the
4
A water-masking method for counting light obstructing particles in a test oil APC cannot run a preset flush, set it to run four analyses
sample containing a substantially immiscible fluid, and where the test oil sample is
mixed with a masking fluid that is soluble with the oil and with the substantially consecutively of at least 10 mL per run. When setting the
immiscible fluid, is covered by US Patent 6,064,680 issued May 16, 2000. amount of fluid to be analyzed per run, ensure that the total
5
The sole source of manufacturer of the diluent known to the committee at this volume consumed by the APC does not exceed the volume of
time is DOWANOL DPnB, a registered trademark of Dow Chemical Company,
sample held in the sample specimen bottle.
Abbott Rd., Midland, MI 48640. Dow Chemical Company supplies 1–L bottles of
DOWANOL DPnB through Sigma-Aldrich Corp., St. Louis, MO, www.sigma- 11.5 If the APC has an inlet tube (also called pickup tube)
aldrich.com. If you are aware of alternative suppliers, please provide this informa-
use a clean, low-lint towel, wipe off sample inlet tube or any
tion to ASTM International Headquarters. Your comments will receive careful
consideration at a meeting of the responsible technical committee,1 which you may other materials of the APC that will directly contact the sample
attend. fluid. However do not allow any towel or surface to contact an

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unsealed disposable syringe if using that type APC. sample specimen bottle from 12.1.3 to achieve the dilution
Alternatively, use a solvent wash to clean contaminated sur- ratio determined in 9.6 while not overfilling the sample
faces. container. For a sample specimen bottle that can hold 120 mL
11.6 If the fluid last analyzed by the particle counter was of fluid and a dilution ratio of 50 % sample specimen to 50 %
excessively dirty or of unknown origin, flush or back-flush, or diluent, add approximately 45 mL of sample specimen. If more
both, the unit according to the manufacturer’s instructions with than 90 s elapses after the shaking of the sample container in
clean diluent or other compatible diluent recommended by the 12.1.2 before the addition of the sample specimen into the
APC manufacturer. It is recommended that then a test sequence empty specimen bottle in 12.1.4, then the sample container
with the diluent be performed to confirm the cleanliness level shall be shaken again per 12.1.2 to re-homogenise the bulk
is acceptable. sample before transferring the specimen. Record the volume of
NOTE 6—Excessively dirty is a condition when counts in the particle added sample specimen (Vs) to at least 1 mL (for example, 45
counter at counts/mL $4 µm (c) in excess of either 40 000 particles/mL or mL).
the coincidence error limit, whichever is less. Keep in mind the diluting 12.1.5 Replace the lid and return the sample container to an
factor—in order to have 40 000 particles/mL in the particle counter with appropriate location for storage or further analysis.
1:1 dilution, the in-service lubricant contains approximately 80 000
particles/mL.
12.1.6 Add the appropriate amount of the diluent selected in
9.5 into the specimen bottle of sample filled in 12.1.4 to
11.7 Prior to beginning the procedure in Section 12 or 11.7, achieve the dilution ratio determined in 9.6 while not overfill-
perform any preparatory steps required by the APC such as ing the sample container. For a sample container that can hold
entering the sample name. The APC shall be ready for 120 mL of fluid and a dilution ratio of 50 % sample to 50 %
immediate analysis before beginning the procedure. diluent, add approximately 45 mL of diluent. Record the
11.8 Clean diluent background analysis is performed to volume of added diluent (Vd) to at least one mL (for example,
appropriately subtract particle counts contributed by diluent or 45-mL).
water-masking diluent, or both. 12.1.7 Replace the lid on the specimen bottle containing the
11.8.1 The contributing particles from the diluent are ex- diluted sample.
cluded from the final sample results obtained by this method. A 12.1.8 Use the following formula to calculate the dilution
particle analysis of the diluent shall, at a minimum, be ratio with respect to the sample (Dr,s) and the dilution ratio with
performed at the beginning of each day of testing. respect to the diluent (Dr,d):

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11.8.2 Remove the lid from a clean specimen bottle and fill V s 1V d
with diluent to be used for sample dilution, ensuring the D r,s 5 (1)
Vs
specimen bottle is not filled beyond 80 % of its total capacity.
V s 1V d
The amount of diluent added shall be representative of the D r,d 5 (2)
Vd
diluent to be used for sample dilution and the volume shall be
sufficient to analyze at least three replicates with the APC where:
including one 10-mL or larger flush or additional analysis, Dr,s = dilution ratio with respect to the sample,
depending on the capability of the APC to perform a flush prior Dr,d = dilution ratio with respect to the diluent,
to analysis. Vs = volume of sample, and
11.8.3 Analyze the sample diluent as described in 12.3-12.7. Vd = volume of diluent.
11.8.4 Average the particle size cumulative count results for 12.2 Mass Dilution:
the three analyses (discarding the initial analysis if four are
12.2.1 If glassware is used, it shall conform to 7.10. Pouring
required). Retain this result so that these contributing particles
of sample or diluent, or both, into the specimen bottle used for
can be removed when calculating the number of particles in the
the diluted sample created in this procedure is acceptable to
sample that is diluted with this diluent.
change the mixing ratio.
12.2.2 Homogenize the incoming sample by shaking the
12. Procedure
sample container and its contents in the mechanical shaker. For
12.1 Volumetric Dilution: samples 200 mL or less, shake for 1 min. For samples 200 mL
12.1.1 Use volumetric glassware that conforms to 7.6. or larger, shake for 3 min. (Samples that are provided in
12.1.2 Shake the sample container and its contents in the containers larger than the capacity of the mechanical shaker
mechanical shaker. For samples 200 mL or less, shake for one may be shaken using a lateral shaker or other apparatus that
min. For samples 200 mL or larger, shake for three min. provides sufficient agitation. If an alternate apparatus is used, a
(Samples that are provided in containers larger than the longer agitation time may be required.)
capacity of the mechanical shaker may be shaken using a 12.2.3 If the density of the sample or diluent is unknown,
lateral shaker or other apparatus that provides sufficient agita- determine and record the density using the density meter while
tion. If an alternate apparatus is used, a longer agitation time ensuring that this process does not add contamination to the
may be required.) sample or diluent. Repeat 12.2.2 for the sample before pro-
12.1.3 Remove the lid from a clean specimen bottle that can ceeding to 12.2.4.
hold 120 mL of fluid (typical). 12.2.4 Remove the lid from a clean, empty bottle like the
12.1.4 Remove the lid from the sample container and one that will be used for dilution and place it on the electronic
transfer the appropriate specimen volume of sample into that balance. Tare the balance.

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12.2.5 Remove the lid from the sample container and either observe until bubbles have risen to the surface. Vacuum
weigh the sample container directly or transfer the appropriate degassing shall not exceed 30 s. Vent the vacuum chamber and
volume of sample into a sample specimen bottle used to remove the sample.
achieve the dilution ratio determined in 9.6 while not overfill- 12.4.2 If using an ultrasonic bath, then degas by unscrewing
ing the sample specimen bottle. For example, in a sample 1⁄4 turn or partially open the lid to the specimen bottle and
specimen bottle that can hold 120 mL of fluid and a dilution placing the sample in the ultrasonic bath for 10 to 15 s, or until
ratio of 50 % sample to 50 % diluent, add approximately 40 g visible air bubbles have surfaced to the top of the sample. If
of sample. If more than 90 s elapse after the shaking of the needed, hold the sample in place to ensure it does not tip over
sample container before the addition of the sample into the in the ultrasonic bath. Sonication time shall not exceed 30 s.
specimen bottle, the sample shall be shaken again per 12.2.2 Remove the sample from the ultrasonic bath and wipe dry the
before performing this step. exterior of the specimen bottle.
12.2.6 If dilution is not being done in the original sample
container in which the sample was originally collected, replace NOTE 7—The purpose of partially unscrewing or opening the lid is to
the lid and return the sample container to an appropriate promote quick degassing of the sample. It is acceptable for air bubbles to
location for storage or further analysis. remain near the surface of the sample above the level of water in the
ultrasonic bath. It may be noted that air bubbles appear to be generated on
12.2.7 Reweigh the specimen bottle that now includes the interior walls of the sample specimen bottle while it is being sonicated.
sample from 12.2.4 and record the exact weight once the These created bubbles can continue indefinitely and shall not be of
balance has stabilized. This weight is the weight of the added concern when determining whether or not the sample has been properly
sample (Ms). Tare the balance. agitated.
12.2.8 Add the appropriate amount of the diluent selected in 12.4.3 If using syringe degassing port, open a sealed pack-
9.5 into the specimen bottle of sample filled in 12.1.4 to age containing the syringe, fill the syringe with diluted sample
achieve the dilution ratio determined in 9.6 while not overfill- from the homogenised diluted sample, install a retaining spacer
ing the sample container. For example, in a sample container to prevent syringe plunger from retracting, insert Luer tip of
that can hold 120 mL of fluid and a dilution ratio of 50 % syringe upward into degassing port and initiate vacuum suction
sample to 50 % diluent, add approximately 40 g of diluent. through that port. Observe until bubbles rise to the top portion
12.2.9 Reweigh the sample specimen bottle now containing of the syringe. Vacuum degassing shall not exceed 30 s. After
the sample and diluent and record the exact weight once the degassing, immediately remove the syringe from the degassing

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balance has stabilized. This weight is the weight of the added port, expel accumulated air, invert the syringe, and insert the
diluent (Md).
Luer tip of the syringe into the sample testing port.
12.2.10 Replace the lid on the specimen bottle containing
the diluted sample. 12.5 If necessary, perform any additional steps specific to
12.2.11 Use the following formula to calculate the dilution the APC to be used for analysis, such as transferring the sample
ratio with respect to the sample (Dr,s) and the dilution ratio with into a syringe and then degassing that sub-sample of diluted
respect to the diluent (Dr,d): lubricant in preparation for injection into the APC. Immedi-
Ms Md ately begin the processing of the sample on the APC that has
1 been prepared according to Section 10. If more than 60 s elapse
Ps Pd
D r,s 5 (3) after the shaking of the diluted sample in 12.3 and the start of
Ms
Ps the automated analysis by the APC in 12.6, the procedure shall
be restarted with shaking of sample in step 12.3. This is to
Ms Md
1 ensure that suspended particles do not settle in the diluted
Ps Pd
D r,d 5 (4) sample.
Md
Pd 12.6 Obtain three consecutive qualifying particle count
results. If the APC is not capable of performing consecutive
where:
sampling as described in Section 11, run two or three additional
Dr,s = dilution ratio with respect to the sample, analyses of the same sample, beginning at 12.3. The number of
Dr,d = dilution ratio with respect to the diluent, additional analyses to be run is dependent on the capability of
Ms = mass of sample (in grams),
the APC to perform a flush cycle with the sample prior to the
Md = mass of diluent (in grams),
Ps = density of sample (in g/cm3), and very first analysis. If the unit can be flushed with at least 10 mL
Pd = density of diluent (in g/cm3). of the sample prior to the first analysis, three total analyses are
necessary and are considered qualified particle count results. If
12.3 Manually or mechanically agitate the diluted sample the unit cannot be flushed with at least 10 mL of the sample
vigorously for 30 s. prior to the first analysis, four total analyses are necessary. In
12.4 Immediately degas the diluted sample by using this case, the particle count results from the first sample are to
vacuum chamber or ultrasonic bath or syringe degassing port be discarded and the results from the next three analyses are
or combination: considered qualified particle count results. This is to ensure
12.4.1 If using a vacuum chamber, remove the lid from the that there are three analyses of the sample that do not include
specimen bottle containing the homogenised diluted sample. any cross contamination from a different sample previously
Place it in the vacuum chamber. Evacuate the chamber and analyzed.

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12.7 Compare the particle count to the coincidence error 12.10 At the end of the testing day, flush the particle counter
limit specified by the APC manufacturer. If the sample exceeds with clean diluent or an oil of a known cleanliness approxi-
this limit, the sample requires further dilution. Either a new mately equal to the clean diluent.
sample shall be made from the original neat sample, beginning
at 12.1, or the current sample with a known dilution ratio shall 13. Report
be further diluted beginning at 12.3. 13.1 Report should include the following information:
12.8 Average the particle size cumulative count results for 13.1.1 A reference to this test method.
the three analyses (discarding the initial analysis if four are 13.1.2 The sample identification.
required). For the cumulative particle counts at the $4 µm (c), 13.1.3 The date of the test.
$6 µm (c), $14 µm(c) size ranges, the results shall be rejected 13.1.4 Particle size cumulative counts reported by the in-
if the variation between the counts exceeds the limits in Annex strument (for example, $4 µm (c), $6 µm (c), $14 µm (c), $21
A2. Retest may be performed provided there is sufficient µm (c), $38 µm (c), etc.).
diluted sample specimen remaining beginning either with the 13.1.5 ISO code result, according to ISO 4406 for $4
step to agitate the diluted sample specimen (12.3) or with the µm (c), $6 µm (c), $14 µm (c). (Other classification systems
step to homogenise the neat sample in the original container may also be used, for example, SAE AS4059.)
(12.2). 13.1.6 Any deviation, by agreement or otherwise, from the
specified procedures.
12.9 Calculate the cumulative number of particles per mil-
13.1.7 In cases of dispute also report information related to
liliter at each particle size present in the original sample by
the APC instrument and any settings that deviate from those
using the following formula. Refer to Annex A2 demonstrating
given in this test method.
this calculation:

S
C s,n $ n mm 5 D r,s C t,n 2
Cd
D r,d D (5)
14. Precision and Bias
14.1 A temporary precision statement including preliminary
where: repeatability and Reproducibility standard deviation is reported
n = Particle size range of interest (for example, $4 in Table 1. Data were collected on multiple instruments of the
µm (c)), same type using mass dilution (12.2) and syringe degassing
Cs,n = Cumulative particle counts per millilitre in the origi- (12.4.3). Other instrument types, dilution and degassing op-

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nal sample at particle size range n, tions will be tested so that a final precision will be determined
Dr,s = Dilution ratio with respect to the sample as calculated and available within five years after the publication of this test
in 12.1.8 or 12.2.11, method.6
Ct,n = Resulting cumulative particle counts per millilitre at 14.2 Table 1 reports repeatability calculated from results of
particle size range n µm from 12.8 of the analysis of two samples tested thirty times each in the same laboratory
the diluted sample, within-laboratory variability. This table also reports Reproduc-
Cd = Cumulative particle counts per millilitre in the origi- ibility calculated from the results of thirteen samples tested in
nal diluent at size range n as determined by 11.8.4, seven different field laboratories.
and
Dr,d = Dilution ratio with respect to the diluent as calculated 15. Keywords
in 12.1.8 or 12.2.11.
15.1 automatic particle counter; diluent; emulsified water;
12.9.1 If the contribution of particles from the diluent particle contamination; particle counting; soft particles; water-
exceeds 12.5 % of the total number of particles counted (for masking
example, $4 µm (c)), the sample shall be considered invalid. It
shall either be reanalyzed after additional filtration of the
diluent or a notation of this non-compliance shall be added to 6
Supporting data have been filed at ASTM International Headquarters and may
the report. be obtained by requesting Research Report RR:D02-1646.

TABLE 1 Temporary Precision with 95 % Confidence

Repeatability Reproducibility Data Range Data Range
Parameter Units
2.77 × std dev 2.77 × std dev Low High
Counts $4 µm (c) counts/mL 30 % 113 % 150 110 000
Counts $6 µm (c) counts/mL 30 % 76 % 60 60 000
Counts $14 µm (c) counts/mL 73 % 135 % 6 22 000
ISO $4 µm (c) code value <1 1.7 14 24
ISO $6 µm (c) code value <1 1.2 13 22
ISO $14 µm (c) code value 1.5 2 10 18

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ANNEXES

(Mandatory Information)

A1. TYPICAL DILUENTS

A1.1 Diluent List—See Table A1.1.

TABLE A1.1 Diluent List

NOTE 1—Precision statement for repeatability and reproducibility is based using diluents marked with asterisk (*).
Is this a MSDS MSDS MSDS
Diluent
water-masking diluent? Health Rating Flammability Rating Reactivity Rating
Stoddard solvent, also called no 2 2 1
Type 1 mineral spirits or white spirits

kerosene no 1 2 0

lamp oil* no 1 1 0

25 % 2-isopropanol / 75 % toluene yes 3 3 0

dipropylene glycol n-propyl ether* yes 0 0 0

A2. PROCEDURE FOR VERIFYING ACCEPTABLE ANALYSIS-TO-ANALYSIS VARIABILITY FOR APC SAMPLES

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NOTE A2.1—This procedure and table are consistent with 6.3 of this test
method and Table 8 in ISO 11171. If the total number of particles counted
for the size range being considered is less than 100, this procedure is not
required and the data can be considered valid.
A2.3 Compare the calculated percent differences to those
shown in Table A2.1 for the corresponding average number of
particle counts. If the calculated percent difference is less than
or equal to the maximum allowable percent difference value in
A2.1 Average the three qualifying raw particle counts. Do Table A1.1, the data is considered valid. If the calculated
not perform any calculations to correct for dilution if appli- percent difference exceeds the value given in Table A1.1, the
cable. data shall be rejected and appropriate steps taken to correct for
A2.2 Calculate the percent difference (Dq) between the analytical errors.
highest (Cmax) and lowest (Cmin) measured particle count for
the particle size range (for example, $4 µm(c), $6 µm (c), or
$14 µm (c)).
100~ C max 2 C min!
Dq 5 (A2.1)
H
C

where:
Dq = percent difference,
Cmax = highest cumulative particle count for the size range
obtained in the series of analyses,
Cmin = lowest cumulative particle count for the size range
obtained in the series of analyses, and
C̄ = the average of the cumulative particle count for the
size range obtained in the series of analyses.

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 D7647 − 10
TABLE A2.1 Maximum Allowable Percent Differences in Particle
Counts Between Runs
Average Number of Total
Maximum Allowable
Particles
Percent Difference
Counted per Run, C̄
10 000 # C̄ < ` 11.0
5000 # C̄ < 10 000 11.3
2000# C̄ < 5000 11.9
1000 # C̄ < 2000 13.4
500 # C̄ < 1000 15.6
200# C̄ < 500 19.3
100# C̄ < 200 27.5
50 # C̄ < 100 37.4
20 # C̄ < 50 51.8

A3. EXAMPLE OF VARIABILITY ANALYSIS AND DILUTION CORRECTION CALCULATION OF AN OIL SAMPLE

A3.1 Sample Information A3.1 A3.4.2 Cumulative particles per millilitre in the original
Vs = 45.0-mL sample sample, $4 µm (c) (in accordance with 12.9):
Vd = 45.0-mL diluent
Dilution ratio with respect to the sample, Dr,s = 2.0
Dilution ratio with respect to the diluent, Dr,d = 2.0
S
C s,n $ n mm 5 D r,s C t,n 2
Cd
D r,d D (A3.1)

A3.2 Analysis Information A3.2

15 mL flush followed by three consecutive analyses
S
C s,4 $ 4 mm 5 2.0 1837.07 2
49.93
2.0 D
5 3624.21 counts/mL
Volume/analysis – 10 mL (A3.2)
A3.3 Variability Analysis A3.4.3 Repeating this calculation for all other size ranges
A3.3.1 Sample Results: gives the following:

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Cumulative Counts/mL Total Max Cumulative Counts/mL
Size Size Range
Particles DqB Allowable in the Original Sample
Range Run 1 Run 2 Run 3 Average CountedA DqC
$ 4 µm (c) 3624.2
$ 4 µm (c) 1817.8 1819.7 1874.7 1837.07 18371 3.2 % 11.0 % $ 6 µm (c) 749.5
$ 10 µm (c) 203.8
$ 6 µm (c) 387.5 373.6 395.8 385.63 3856 5.8 % 11.9 % $ 14 µm (c) 82.6
$ 21 µm (c) 21.7
$ 10 µm (c) 106.7 98.9 115.2 106.93 1069 N/A N/A $ 38 µm (c) 2.3
$ 70 µm 1.4
$ 14 µm (c) 41.5 38.9 45.2 41.87 419 15.0 % 19.3 %
A3.4.4 The ISO code result, according to ISO 4406:99 for
$ 21 µm (c) 9.1 12.3 11.8 11.07 111 N/A N/A $4 µm (c), $6 µm (c), $14 µm (c): 19/17/14.
$ 38 µm (c) 1.2 1.3 1.2 1.23 12 N/A N/A
A3.4.5 These numbers are to be reported according to
$ 70 µm 0.6 0.8 0.7 0.70 7 N/A N/A Section 13.
A
Product of average cumulative counts/mL multiplied by the total volume ana-
lyzed (10 mL).
B
Calculated according to A2.2.
C
Determined according to Table A2.1.

A3.4 Dilution Correction Calculation

A3.4.1 Diluent Cleanliness Results in accordance with 11.8:
Size Cumulative Counts/mL
Range Run 1 Run 2 Run 3 Average
$ 4 µm (c) 50.2 48.6 51 49.93
$ 6 µm (c) 22.3 20.7 22.4 21.80
$ 10 µm (c) 10.1 9.6 10.4 10.03
$ 14 µm (c) 1.2 0.9 1.2 1.10
$ 21 µm (c) 0.4 0.3 0.5 0.40
$ 38 µm (c) 0.2 0.1 0.2 0.17
$ 70 µm 0 0 0 0.00

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