ASTM D7157-12(2018)
(Test Method)Standard Test Method for Determination of Intrinsic Stability of Asphaltene-Containing Residues, Heavy Fuel Oils, and Crude Oils (n-Heptane Phase Separation; Optical Detection)
Standard Test Method for Determination of Intrinsic Stability of Asphaltene-Containing Residues, Heavy Fuel Oils, and Crude Oils (<emph type="ital">n</emph >-Heptane Phase Separation; Optical Detection)
SIGNIFICANCE AND USE
5.1 This test method describes a sensitive method for estimating the intrinsic stability of an oil. The intrinsic stability is expressed as S-value. An oil with a low S-value is likely to undergo flocculation of asphaltenes when stressed (for example, extended heated storage) or blended with a range of other oils. Two oils each with a high S-value are likely to maintain asphaltenes in a peptized state and not lead to asphaltene flocculation when blended together.
5.2 This test method can be used by petroleum refiners to control and optimize the refinery processes and by blenders and marketers to assess the intrinsic stability of blended asphaltene-containing heavy fuel oils.
SCOPE
1.1 This test method covers a procedure for quantifying the intrinsic stability of the asphaltenes in an oil by an automatic instrument using an optical device.
1.2 This test method is applicable to residual products from thermal and hydrocracking processes, to products typical of Specifications D396 Grades No. 5L, 5H, and 6, and D2880 Grades No. 3-GT and 4-GT, and to crude oils, providing these products contain 0.5 % by mass or greater concentration of asphaltenes (see Test Method D6560).
1.3 This test method quantifies asphaltene stability in terms of state of peptization of the asphaltenes (S-value), intrinsic stability of the oily medium (So) and the solvency requirements of the peptized asphaltenes (Sa).
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: D7157 − 12 (Reapproved 2018)
Standard Test Method for
Determination of Intrinsic Stability of Asphaltene-Containing
Residues, Heavy Fuel Oils, and Crude Oils (n-Heptane
Phase Separation; Optical Detection)
This standard is issued under the fixed designation D7157; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers a procedure for quantifying the
D396 Specification for Fuel Oils
intrinsic stability of the asphaltenes in an oil by an automatic
D2880 Specification for Gas Turbine Fuel Oils
instrument using an optical device.
D4057 Practice for Manual Sampling of Petroleum and
1.2 This test method is applicable to residual products from
Petroleum Products
thermal and hydrocracking processes, to products typical of
D4175 Terminology Relating to Petroleum Products, Liquid
Specifications D396 Grades No. 5L, 5H, and 6, and D2880
Fuels, and Lubricants
Grades No. 3-GT and 4-GT, and to crude oils, providing these
D4177 Practice for Automatic Sampling of Petroleum and
products contain 0.5 % by mass or greater concentration of
Petroleum Products
asphaltenes (see Test Method D6560).
D4870 Test Method for Determination of Total Sediment in
Residual Fuels
1.3 This test method quantifies asphaltene stability in terms
D6560 Test Method for Determination ofAsphaltenes (Hep-
of state of peptization of the asphaltenes (S-value), intrinsic
tane Insolubles) in Crude Petroleum and Petroleum Prod-
stabilityoftheoilymedium(So)andthesolvencyrequirements
ucts
of the peptized asphaltenes (Sa).
D6792 Practice for Quality Management Systems in Petro-
1.4 The values stated in SI units are to be regarded as
leum Products, Liquid Fuels, and Lubricants Testing
standard. No other units of measurement are included in this
Laboratories
standard.
3. Terminology
1.5 This standard does not purport to address all of the
3.1 Definitions:
safety concerns, if any, associated with its use. It is the
3.1.1 For definitions of some terms used in this test method,
responsibility of the user of this standard to establish appro-
refer to Terminology D4175.
priate safety, health, and environmental practices and deter-
3.1.2 asphaltenes, n—(rarely used in the singular), in petro-
mine the applicability of regulatory limitations prior to use.
leum technology, represent an oil fraction that is soluble in a
1.6 This international standard was developed in accor-
specified aromatic solvent but separates upon addition of an
dance with internationally recognized principles on standard-
excess of a specified paraffinic solvent.
ization established in the Decision on Principles for the
3.1.2.1 Discussion—In this test method, the aromatic sol-
Development of International Standards, Guides and Recom-
vent is toluene and the paraffinic solvent is n-heptane.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. 3.1.3 compatibility, n—of crude oils or of heavy fuel oils,
the ability of two or more crude oils or fuel oils to blend
together within certain concentration ranges without evidence
of separation, such as the formation of multiple phases.
This test method is under the jurisdiction of Committee D02 on Petroleum
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
mittee D02.14 on Stability, Cleanliness and Compatibility of Liquid Fuels. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 1, 2018. Published June 2018. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2005. Last previous edition approved in 2012 as D7157 – 12. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D7157-12R18. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7157 − 12 (2018)
3.1.3.1 Discussion—Incompatible heavy fuel oils or crude aromaticsolventtothearomaticplusparaffinicsolventmixture
oils, when mixed or blended, result in the flocculation or having the same peptizing power as the oil.
precipitation of asphaltenes. Some oils may be compatible
3.2.5 solvent aromaticity, n—of a binary mixture of a
within certain concentration ranges in specific mixtures, but
paraffınic and an aromatic solvent, the solvency power of the
incompatible outside those ranges.
binary mixture.
3.2.5.1 Discussion—For the purpose of this test method,
3.1.4 flocculation, n—of asphaltenes from crude oils or
solvent aromaticity is defined as a ratio by volume of the
heavy fuel oils, the aggregation of colloidally dispersed as-
aromaticsolvent(toluene)totheparaffinicsolvent(n-heptane).
phaltenes into visible larger masses which may or may not
settle.
3.3 Symbols:
3.1.5 peptization, n—of asphaltenes in crude oils or heavy
FR = flocculation ratio
oils, the dispersion of asphaltenes to produce a colloidal
FR = maximum flocculation ratio
max
dispersion.
S = the intrinsic stability of an oil
Sa = the peptizability of an asphaltene
3.1.6 stability reserve, n—in petroleum technology, the
So = the peptizing power of an oil
property of an oil to maintain asphaltenes in a peptized state
X = paraffinic solvent consumption of undiluted oil, in
min
and prevent flocculation of asphaltenes.
mL/g of oil
3.1.6.1 Discussion—An oil with a low stability reserve is
likelytoundergoflocculationofasphalteneswhenstressed(for
4. Summary of Test Method
example, extended heated storage) or blended with a range of
4.1 Thistestmethodusesanintegratedautomatedanalytical
other oils.Two oils each with a high stability reserve are likely
measurement system with an optical probe for the detection of
to maintain asphaltenes in a peptized state and not lead to
asphaltene precipitation from a toluene solution of the sample.
flocculation when blended together.
4.2 Three test specimens are dissolved in three different
3.2 Definitions of Terms Specific to This Standard:
quantities of toluene. The three specimen/toluene solutions are
3.2.1 intrinsic stability (S-value), n— of refinery residual
automatically and simultaneously titrated with n-heptane to
streams, residual fuel oils and crude oils, an indication of the
cause precipitation of the asphaltenes. The optical probe
stability or available solvency power of an oil with respect to
monitors the formation of flocculated asphaltenes during the
precipitation of asphaltenes.
titration. Flocculated asphaltenes will alter the detected light
3.2.1.1 Discussion—Sincetheequationdefining S-valueis S
intensity. Start of flocculation is interpreted when the optical
=(1+ X ), where X is the minimum volume (in mL) of
probe detects a significant and sustained decrease in rate-of-
min min
paraffinic solvent, n-heptane, to be added to1gofoilto result
change of the light intensity.
in flocculation of asphaltenes, the smallest S-value is 1, which
4.3 A computer routine calculates stability parameters and
means the oil is unstable and can precipitate asphaltenes
subsequently the intrinsic stability of the oil from the added
without addition of any paraffinic solvent. A higher S-value
n-heptane at the inversion point, the mass of specimen, and the
indicates that an oil is more stable with respect to flocculation
volume of toluene, for the three specimen/toluene solutions.
of asphaltenes. S-value by this test method relates specifically
to toluene and n-heptane as the aromatic and paraffinic 5. Significance and Use
solvents, respectively.
5.1 This test method describes a sensitive method for
estimating the intrinsic stability of an oil.The intrinsic stability
3.2.2 inversion point, n—point in the n-heptane titration
is expressed as S-value. An oil with a low S-value is likely to
curve, where the onset of asphaltene flocculation leads to
undergo flocculation of asphaltenes when stressed (for
inversion of the light intensity.
example, extended heated storage) or blended with a range of
3.2.2.1 Discussion—At the first stage of the addition of
other oils. Two oils each with a high S-value are likely to
n-heptane to a dilution of specimen and toluene, light intensity
maintain asphaltenes in a peptized state and not lead to
increases through dilution. When asphaltenes start to
asphaltene flocculation when blended together.
flocculate, there will be a point where the increase in light
intensity through dilution matches the light intensity decrease
5.2 This test method can be used by petroleum refiners to
(inversion)asaresultofcoagulatedasphaltenesobstructingthe controlandoptimizetherefineryprocessesandbyblendersand
light beam.
marketerstoassesstheintrinsicstabilityofblendedasphaltene-
containing heavy fuel oils.
3.2.3 Sa, n—the S-value of an asphaltene, which is the
peptizability or ability of an asphaltene to remain in a colloidal
6. Interferences
dispersion.
6.1 High content of insoluble inorganic matter (sediment)
3.2.3.1 Discussion—Sa can also be described as one minus
has some interference in this test method. In this case, the
the ratio of So to S. Sa is linked to the length and number of
insoluble matter shall be removed by filtration according to
aromatic chains within the asphaltenes.
Test Method D4870.
3.2.4 So, n—the S-value of an oil.
6.2 Free water present in the oil can cause difficulties with
3.2.4.1 Discussion—So can also be described as the aro- the optical detector and should be removed by any suitable
matic equivalent of the oil expressed as the ratio of the means (for example, centrifugation) prior to testing.
D7157 − 12 (2018)
7. Apparatus 7.3 Dispenser, capable of delivering up to 10 mLof toluene
with an accuracy of 60.1 mL.
7.1 General—(See Fig. 1) This test method uses an inte-
3,4
grated automated analytical measurement system comprised 7.4 Condenser, double surface with a tapered ground-glass
of a PC-based computer and three titration stations. joint (male) at the bottom to fit the top of the titration cell.
7.1.1 Computer, PC-based computer with associated
7.5 Magnetic Stirrer/Hotplate, stirrer speed adjustable from
software, capable of controlling up to three independent
100 r⁄min to 1000 r⁄min.
titrationstations,controllingtestsequencing,andacquisitionof
7.6 Stirring Bar, magnetic, PFTE-coated, 20 mm in length.
optical probe signal data. The associated software also pro-
vides for processing calculations and automatically produces a
8. Reagents and Materials
report of important test parameters.
8.1 Purity of Reagents—Reagent grade chemicals shall be
7.1.2 Titration Stations:
used in all tests. Unless otherwise indicated, it is intended that
7.1.2.1 Titration Unit, automatic computer controlled, ad-
all reagents conform to the specifications of the Committee on
justable motor-driven ceramic piston pump, capable of deliv-
Analytical Reagents of the American Chemical Society where
ering solvent at a rate of 0.01 mL⁄s to 0.5 mL⁄s, with a volume
such specifications are available. Other grades may be used,
dispensing accuracy of 60.01 mL.
provided it is first ascertained that the reagent is of sufficiently
7.1.2.2 Magnetic Stirrer, adjustable from 200 r⁄min to
high purity to permit its use without lessening the accuracy of
400 r⁄min.
the determination.
7.1.2.3 Optical Probe, consisting of a system of three areas
8.1.1 Toluene. (Warning—Flammable. Health hazard. Va-
of light emitters (880 nm) and three areas of light receivers.
por may cause flash fire.) (See Annex A1.)
The analytical measurement system will automatically select
8.1.2 n-Heptane. (Warning—Flammable. Vapor harmful.
the optimum area, based on the level of translucency of the
Vapor may cause flash fire.) (See Annex A1.)
sample.
7.1.2.4 Titration Cell, of borosilicate glass, flat bottom,
8.2 Quality Control Sample—A stable and homogeneous
outside diameter 30 mm 6 2 mm, volume 95 mL 6 15 mL,
residual fuel oil having physical and chemical properties
fitted with a tapered ground glass joint (female).
similar to those of typical sample fuels routinely tested.
7.2 Balance, capable of reading to 0.1 mg or better.
9. Sampling and Test Specimens
9.1 Sampling:
The sole source of supply of the apparatus (Automated Stability Analyser)
known to the committee at this time is Rofa France, 6 Rue Raymond Poincare,
F-25300,LesAllies,France.Ifyouareawareofalternativesuppliers,pleaseprovide
Reagent Chemicals, American Chemical Society Specifications, American
this information to ASTM International Headquarters. Your comments will receive
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
careful consideration at a meeting of the responsible technical committee, which
listed by the American Chemical Society, see Annual Standards for Laboratory
you may attend.
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
The Rofa stability analyzer is covered by a patent; INPI, date 18/05/04,
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
registrationnumber04.05406;RofaFrance,6RueRaymondPoincare,F-25300,Les
MD.
Allies, France.
FIG. 1 Schematic Drawing of the Integrated Automated Stability Analyser System
D7157 − 12 (2018)
9.1.1 Obtain representative samples in accordance with 10. Preparation of Apparatus
recognized sampling procedures such as Practices D4057 or
10.1 Prepare and set up the instrument for operation accord-
D4177.
ing to the manufacturer’s manual. (Refer to Fig. 1.)
9.1.2 Samples of very viscous materials may be warmed
10.2 Plug the optical probes into their connectors and place
until they are reasonably fluid before they are sampled.
them in their stand by position.
9.1.3 Store samples prior to taking test specimens at ambi-
ent temperatures.
10.3 Ensure that the reagent vessel contains sufficient
n-heptane to run the tests (minimum 200 mL).
9.2 Test Specimen Preparation:
9.2.1 Sample Temperature—If necessary, warm viscous
10.4 CleaningInstructions—Performthefollowingcleaning
samples until they can be mixed readily before opening the
procedure after the test procedure (see 12.1.8).
storage container. For fuels with a high wax content (high pour
10.4.1 Carefully remove the dosing tube and the optical
point) the temperature must be at least 15 °C above the pour
probe from the titration cell. Clean the optical probe with an
point.
appropriate solvent (toluene) (see 8.1.1).
9.2.2 Manually shake the sample thoroughly. If the sample
10.4.2 Remove the stirr
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7157 − 12 D7157 − 12 (Reapproved 2018)
Standard Test Method for
Determination of Intrinsic Stability of Asphaltene-Containing
Residues, Heavy Fuel Oils, and Crude Oils (n-Heptane
Phase Separation; Optical Detection)
This standard is issued under the fixed designation D7157; 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*Scope
1.1 This test method covers a procedure for quantifying the intrinsic stability of the asphaltenes in an oil by an automatic
instrument using an optical device.
1.2 This test method is applicable to residual products from thermal and hydrocracking processes, to products typical of
Specifications D396 Grades No. 5L, 5H, and 6, and D2880 Grades No. 3-GT and 4-GT, and to crude oils, providing these products
contain 0.5 mass% 0.5 % by mass or greater concentration of asphaltenes (see Test Method D6560).
1.3 This test method quantifies asphaltene stability in terms of state of peptization of the asphaltenes (S-value), intrinsic stability
of the oily medium (So) and the solvency requirements of the peptized asphaltenes (Sa).
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to useuse.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D396 Specification for Fuel Oils
D2880 Specification for Gas Turbine Fuel Oils
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D4870 Test Method for Determination of Total Sediment in Residual Fuels
D6560 Test Method for Determination of Asphaltenes (Heptane Insolubles) in Crude Petroleum and Petroleum Products
D6792 Practice for Quality Management Systems in Petroleum Products, Liquid Fuels, and Lubricants Testing Laboratories
3. Terminology
3.1 Definitions:
3.1.1 For definitions of some terms used in this test method, refer to Terminology D4175.
3.1.2 asphaltenes, n—(rarely used in the singular), in petroleum technology, represent an oil fraction that is soluble in a specified
aromatic solvent but separates upon addition of an excess of a specified paraffinic solvent.
3.1.2.1 Discussion—
This test method is under the jurisdiction of Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee D02.14
on Stability Stability, Cleanliness and CleanlinessCompatibility of Liquid Fuels.
Current edition approved Nov. 1, 2012June 1, 2018. Published February 2013June 2018. Originally approved in 2005. Last previous edition approved in 20092012 as
D7157D7157 – 12.–09. DOI: 10.1520/D7157-12.10.1520/D7157-12R18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7157 − 12 (2018)
In this test method, the aromatic solvent is toluene and the paraffinic solvent is n-heptane.
3.1.3 compatibility, n—of crude oils or of heavy fuel oils, the ability of two or more crude oils or fuel oils to blend together
within certain concentration ranges without evidence of separation, such as the formation of multiple phases.
3.1.3.1 Discussion—
Incompatible heavy fuel oils or crude oils, when mixed or blended, result in the flocculation or precipitation of asphaltenes. Some
oils may be compatible within certain concentration ranges in specific mixtures, but incompatible outside those ranges.
3.1.4 flocculation, n—of asphaltenes from crude oils or heavy fuel oils, the aggregation of colloidally dispersed asphaltenes into
visible larger masses which may or may not settle.
3.1.5 peptization, n—of asphaltenes in crude oils or heavy oils, the dispersion of asphaltenes to produce a colloidal dispersion.
3.1.6 stability reserve, n—in petroleum technology, the property of an oil to maintain asphaltenes in a peptized state and prevent
flocculation of asphaltenes.
3.1.6.1 Discussion—
An oil with a low stability reserve is likely to undergo flocculation of asphaltenes when stressed (for example, extended heated
storage) or blended with a range of other oils. Two oils each with a high stability reserve are likely to maintain asphaltenes in a
peptized state and not lead to flocculation when blended together.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 intrinsic stability (S-value), n— of refinery residual streams, residual fuel oils and crude oils, an indication of the stability
or available solvency power of an oil with respect to precipitation of asphaltenes.
3.2.1.1 Discussion—
Since the equation defining S-value is S = (1 + X ), where X is the minimum volume (in mL) of paraffinic solvent, n-heptane,
min min
to be added to 1 g of oil to result in flocculation of asphaltenes, the smallest S-value is 1, which means the oil is unstable and can
precipitate asphaltenes without addition of any paraffinic solvent. A higher S-value indicates that an oil is more stable with respect
to flocculation of asphaltenes. S-value by this test method relates specifically to toluene and n-heptane as the aromatic and
paraffinic solvents, respectively.
3.2.2 inversion point, n—point in the n-heptane titration curve, where the onset of asphaltene flocculation leads to inversion of
the light intensity.
3.2.2.1 Discussion—
At the first stage of the addition of n-heptane to a dilution of specimen and toluene, light intensity increases through dilution. When
asphaltenes start to flocculate, there will be a point where the increase in light intensity through dilution matches the light intensity
decrease (inversion) as a result of coagulated asphaltenes obstructing the light beam.
3.2.3 Sa, n—the S-value of an asphaltene, which is the peptizability or ability of an asphaltene to remain in a colloidal
dispersion.
3.2.3.1 Discussion—
Sa can also be described as one minus the ratio of So to S.Sa is linked to the length and number of aromatic chains within the
asphaltenes.
3.2.4 So, n—the S-value of an oil.
3.2.4.1 Discussion—
So can also be described as the aromatic equivalent of the oil expressed as the ratio of the aromatic solvent to the aromatic plus
paraffinic solvent mixture having the same peptizing power as the oil.
3.2.5 solvent aromaticity, n—of a binary mixture of a paraffınic and an aromatic solvent, the solvency power of the binary
mixture.
D7157 − 12 (2018)
3.2.5.1 Discussion—
For the purpose of this test method, solvent aromaticity is defined as a ratio by volume of the aromatic solvent (toluene) to the
paraffinic solvent (n-heptane).
3.3 Symbols:
FR = flocculation ratio
FR = maximum flocculation ratio
max
S = the intrinsic stability of an oil
Sa = the peptizability of an asphaltene
So = the peptizing power of an oil
X = paraffinic solvent consumption of undiluted oil, in mL/g of oil
min
4. Summary of Test Method
4.1 This test method uses an integrated automated analytical measurement system with an optical probe for the detection of
asphaltene precipitation from a toluene solution of the sample.
4.2 Three test specimens are dissolved in three different quantities of toluene. The three specimen/toluene solutions are
automatically and simultaneously titrated with n-heptane to cause precipitation of the asphaltenes. The optical probe monitors the
formation of flocculated asphaltenes during the titration. Flocculated asphaltenes will alter the detected light intensity. Start of
flocculation is interpreted when the optical probe detects a significant and sustained decrease in rate-of-change of the light intensity.
4.3 A computer routine calculates stability parameters and subsequently the intrinsic stability of the oil from the added
n-heptane at the inversion point, the mass of specimen, and the volume of toluene, for the three specimen/toluene solutions.
5. Significance and Use
5.1 This test method describes a sensitive method for estimating the intrinsic stability of an oil. The intrinsic stability is
expressed as S-value. An oil with a low S-value is likely to undergo flocculation of asphaltenes when stressed (for example,
extended heated storage) or blended with a range of other oils. Two oils each with a high S-value are likely to maintain asphaltenes
in a peptized state and not lead to asphaltene flocculation when blended together.
5.2 This test method can be used by petroleum refiners to control and optimize the refinery processes and by blenders and
marketers to assess the intrinsic stability of blended asphaltene-containing heavy fuel oils.
6. Interferences
6.1 High content of insoluble inorganic matter (sediment) has some interference in this test method. In this case, the insoluble
matter shall be removed by filtration according to Test Method D4870.
6.2 Free water present in the oil can cause difficulties with the optical detector and should be removed by any suitable means
(for example, centrifugation) prior to testing.
7. Apparatus
3,4
7.1 General—(See Fig. 1) This test method uses an integrated automated analytical measurement system comprised of a
PC-based computer and three titration stations.
7.1.1 Computer, PC-based computer with associated software, capable of controlling up to three independent titration stations,
controlling test sequencing, and acquisition of optical probe signal data. The associated software also provides for processing
calculations and automatically produces a report of important test parameters.
7.1.2 Titration Stations:
7.1.2.1 Titration Unit, automatic computer controlled, adjustable motor-driven ceramic piston pump, capable of delivering
solvent at a rate of 0.010.01 mL ⁄s to 0.50.5 mL mL/s, ⁄s, with a volume dispensing accuracy of 60.01 mL.60.01 mL.
7.1.2.2 Magnetic Stirrer, adjustable from 200200 r ⁄min to 400 400 r r/min.⁄min.
7.1.2.3 Optical Probe, consisting of a system of three areas of light emitters (880 nm) (880 nm) and three areas of light
receivers. The analytical measurement system will automatically select the optimum area, based on the level of translucency of
the sample.
The sole source of supply of the apparatus (Automated Stability Analyser) known to the committee at this time is Rofa France, 6 Rue Raymond Poincare, F-25300, Les
Allies, France. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful
consideration at a meeting of the responsible technical committee, which you may attend.
The Rofa stability analyzer is covered by a patent; INPI, date 18/05/04, registration number 04.05406; Rofa France, 6 Rue Raymond Poincare, F-25300, Les Allies,
France.
D7157 − 12 (2018)
FIG. 1 Schematic Drawing of the Integrated Automated Stability Analyser System
7.1.2.4 Titration Cell, of borosilicate glass, flat bottom, outside diameter 3030 mm 6 2 mm, 2 mm, volume 9595 mL 6 15 mL,
15 mL, fitted with a tapered ground glass joint (female).
7.2 Balance, capable of reading to 0.1 mg 0.1 mg or better.
7.3 Dispenser, capable of delivering up to 10 mL 10 mL of toluene with an accuracy of 60.1 mL. 60.1 mL.
7.4 Condenser, double surface with a tapered ground-glass joint (male) at the bottom to fit the top of the titration cell.
7.5 Magnetic Stirrer/Hotplate, stirrer speed adjustable from 100100 r ⁄min to 1000 1000 r r/min.⁄min.
7.6 Stirring Bar, magnetic, PFTE-coated, 20 mm 20 mm in length.
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such
specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lessening the accuracy of the determination.
8.1.1 Toluene. (Warning—WarningFlammable.—Flammable. Health hazard. Vapor may cause flash fire.) (See Annex A1.)
8.1.2 n-Heptane. (Warning—WarningFlammable.—Flammable. Vapor harmful. Vapor may cause flash fire.) (See Annex A1.)
8.2 Quality Control Sample—A stable and homogeneous residual fuel oil having physical and chemical properties similar to
those of typical sample fuels routinely tested.
9. Sampling and Test Specimens
9.1 Sampling:
9.1.1 Obtain representative samples in accordance with recognized sampling procedures such as Practices D4057 or D4177.
9.1.2 Samples of very viscous materials may be warmed until they are reasonably fluid before they are sampled.
9.1.3 Store samples prior to taking test specimens at ambient temperatures.
9.2 Test Specimen Preparation:
9.2.1 Sample Temperature—If necessary, warm viscous samples until they can be mixed readily before opening the storage
container. For fuels with a high wax content (high pour point) the temperature must be at least 15°C15 °C above the pour point.
9.2.2 Manually shake the sample thoroughly. If the sample contains high content of insoluble inorganic matter, filter the sample
through a 47-mm47 mm diameter glass fiber filter medium (such as Whatman Grade GF/A), using the Test Method D4870 filtration
apparatus. Specimen should be representative of the whole sample.
Reagent Chemicals, American Chemical Society Specifications, America
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