ASTM D4625-21

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Designation: D4625 − 16 D4625 − 21
Standard Test Method for
Middle Distillate Fuel Storage Stability at 43 °C (110 °F)
This standard is issued under the fixed designation D4625; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—The IP designation was removed and footnote 1 was revised editorially in February 2018.
1. Scope*
1.1 This test method covers a method for evaluating the inherent storage stability of distillate fuels having flash points above 38 °C
(100 °F), by Test Methods D93, and 90 % distilled points below 340 °C (644 °F), by Test Method D86.
NOTE 1—ASTM specification fuels falling within the scope of this test method are Specification D396, Grade Nos. 1 and 2; Specification D975, Grades
1-D and 2-D; and Specification D2880, Grades 1-GT and 2-GT.
1.2 This test method is not suitable for quality control testing but, rather it is intended for research use to shorten storage time
relative to that required at ambient storage temperatures.
1.3 Appendix X1 presents additional information about storage stability and the correlation of Test Method D4625 results with
sediment formation in actual field storage.
1.4 The values given in SI units are to be regarded as the standard.
1.4.1 Exception—The values in parentheses are for information only.
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.
2. Referenced Documents
2.1 ASTM Standards:
D86 Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
D93 Test Methods for Flash Point by Pensky-Martens Closed Cup Tester
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricantsand is the direct responsibility of Subcommittee
D02.14 on on Stability, Cleanliness and Compatibility of Liquid Fuels.
Current edition approved Dec. 1, 2016Oct. 1, 2021. Published January 2017November 2021. Originally approved in 1986. Last previous edition approved in 20142016
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as D4625 – 14.D4625 – 16 . DOI: 10.1520/D4625-16E01.10.1520/D4625-21.
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
D4625 − 21
D381 Test Method for Gum Content in Fuels by Jet Evaporation
D396 Specification for Fuel Oils
D975 Specification for Diesel Fuel
D1193 Specification for Reagent Water
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
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 adherent insolubles, n—gums formed during storage that remain tightly attached to the walls of the vessel after fuel has been
flushed from the container.
3.2.2 filterable insolubles, n—solids formed during storage that can be removed from the fuel by filtration.
3.2.3 inherent storage stability, n—of middle distillate fuel—the resistance of the fuel to change during storage in contact with air,
but in the absence of other environmental factors such as water, or reactive metals and dirt.
3.2.4 total insolubles, n—the arithmetic sum of the filterable insolubles plus the adherent insolubles.
4. Summary of Test Method
4.1 Four-hundred (400) mL volumes of filtered fuel are aged by storage in borosilicate glass containers at 43 °C (110 °F) for
periods of 4, 8, 12, 18, and 24 weeks. If desired, perform zero-week analyses on the same day as the other samples are placed in
storage. Zero-week data are used to provide base data and ensure satisfactory technique. After aging for a selected time period,
a sample is removed from storage, cooled to room temperature, and analyzed for filterable insolubles and for adherent insolubles.
5. Significance and Use
5.1 Fuel oxidation and other degradative reactions leading to formation of sediment (and color) are mildly accelerated by the test
conditions compared with typical storage conditions. Test results have been shown to predict storage stability more reliably than
other more accelerated tests. See Appendix X1 for information on the correlation of test results with actual field storage.
5.2 Because the storage periods are long (4 weeks to 24 weeks), the test method is not suitable for quality control testing, but does
provide a tool for research on storage properties of fuels.
5.3 Because environmental effects and the materials and nature of tank construction affect storage stability, the results obtained
by this test are not necessarily the same as those obtained during storage in a specific field storage situation.
6. Apparatus
6.1 Sample Containers, borosilicate glass bottles, nominal capacity 500 mL (Fig. 1). The containers shall have a cap, lid, or cover,
preferably with a polytetrafluoroethylene (PTFE) insert and a hole for a borosilicate glass vent.
6.2 Storage Oven, large enough to contain all of the sample bottles. The oven shall be thermostatically controlled to maintain a
temperature of 43 °C 6 1 °C (110 °F 6 2 °F). It shall be as dark as possible to prevent degradation due to photolytic reactions
and shall also be explosion proof.
6.3 Filter Drying Oven, shall be capable of safely evaporating the solvent at 90 °C 6 5 °C for the drying of filters.
6.4 Filtration System—Arrange the following components as shown in Fig. 2.
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FIG. 1 Sample Storage Container
6.4.1 Funnel and Funnel Base, with filter support for a 47 mm diameter membrane and a locking ring or spring action clip.
6.4.2 Ground/Bond Wire, 0.912 mm to 2.59 mm (No. 10 to No. 19) bare-stranded, flexible stainless steel or copper installed in the
flasks and grounded as shown in Fig. 2.
6.4.3 Receiving Flask, 1.5 L, or larger, borosilicate glass vacuum filter flask, into which the filtration apparatus fits, equipped with
a sidearm to connect to the safety flask.
6.4.4 Safety Flask, 1.5 L, or larger, borosilicate glass vacuum filter flask equipped with a sidearm to connect the vacuum system.
A fuel and solvent resistant rubber hose, through which the grounding wire passes, shall connect the sidearm of the receiving flask
to the tube passing through the rubber stopper in the top of the safety flask.
6.4.5 Vacuum System, either a water-aspirated, or a mechanical, vacuum pump may be used if capable of producing a vacuum of
80 kPa to 100 kPa below atmospheric pressure when measured at the receiving flask.
7. Reagents and Materials
7.1 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.
7.2 Nylon Test and Control Membrane Filters—plain, 47 mm diameter, nominal pore size 0.8 μm. (Membrane filters with a grid
imprinted on their surface may be used as control membrane filters for identification.)
7.3 Hydrocarbon Solvent, 2,2,4-trimethylpentane (iso-octane)—ASTM knock test reference fuel grade or equivalent, prefiltered
through two glass-fiber or nylon membrane filters, nominal pore size 0.8 μm. (Warning—Extremely flammable. Harmful if
inhaled. Vapors may cause flash fire.)
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For Suggestionssuggestions on the testing of reagents not listed by the American Chemical Society, see
AnnualAnalar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial
Convention, Inc. (USPC), Rockville, MD.
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FIG. 2 Schematic of Filtration System
7.4 Adherent Insolubles Solvent (Warning—Extremely flammable. Vapors harmful. May cause flash fire)—Mix equal volumes of
reagent grade acetone (Warning—Extremely flammable. Vapors may cause flash fire), methyl alcohol (Warning—Flammable.
Vapor harmful. May be fatal or cause blindness if swallowed or inhaled. Cannot be made nonpoisonous), and toluene
(Warning—Flammable. Vapor harmful.).
7.5 Purity of Water—Unless otherwise indicated, references to water mean reagent water as defined by Type III of Specification
D1193.
7.6 Liquid or Powder Detergent, water-soluble, for cleaning glassware.
8. Sampling Procedure
8.1 Samples for testing shall be obtained by an appropriate method outlined in Practice D4057 or D4177. Sample containers
should be 1 gal (3.78 L) or larger, epoxy-lined cans. Fill sample cans almost to the top to avoid a significant air space. Purge the
void space with nitrogen. Store the samples at reduced temperature, –7 °C to 4 °C (20 °F to 40 °F), prior to use, where possible.
9. Preparation of Apparatus and Sample Bottles
9.1 Sample Storage Bottles—Scrub each bottle and cap with a detergent solution and rinse it with water. Soak the bottle and cap
overnight in an alkaline laboratory glassware cleaning solution. Rinse the bottle and cap with tap water, then invert them and flush
them with a stream of distilled water. Allow the bottles and caps to dry. Prior to introducing the sample, rinse the bottles with 50 mL
of the fuel sample. Vent the bottles during storage, using a glass tube bent in an upside down “U,” (see Fig. 1), to prevent
contamination of the sample from airborne particulates. Insert the glass tube through a cover, preferably equipped with a
polytetrafluoroethylene (PTFE) insert (see Fig. 1).
9.2 Clean all components of the filtration apparatus as described in 9.2.1 – 9.2.7.
9.2.1 Remove any labels, tags, and so forth.
9.2.2 Wash with warm tap water containing detergent.
9.2.3 Rinse thoroughly with warm tap water.
9.2.4 Rinse thoroughly with deionized water.
9.2.5 Rinse thoroughly with propan-2-ol that has been filtered through a 0.45 μm membrane filter.
9.2.6 Rinse thoroughly with filtered flushing fluid and dry.
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9.2.7 Keep a clean protective cover (the cover may be rinsed with filtered flushing fluid) over the top of the sample container until
the cap is installed. Similarly, protect the funnel opening of the assembled filtration apparatus with a clean protective cover until
ready for use.
9.3 Preparation of Membrane Filters:
9.3.1 Each set of test filters consists of one test membrane filter and one control membrane filter. For fuels containing little
particulate materials, only one set of filters is required. If the fuel is highly contaminated, more than one set of filters may be
required. The two membrane filters used for each individual test shall be identified by marking the petri dishes used to hold and
transport the filters. Clean all glassware used in preparation of membrane filters as described in 9.2.
9.3.1.1 Using forceps, place the test and control membrane filters side by side in a clean petri dish. To facilitate handling, the
membrane filters should rest on clean glass support rods, or watch glasses, in the petri dish.
9.3.1.2 Place the petri dish, with its lid slightly ajar, in a drying oven at 90 °C 6 5 °C and leave it for 30 min.
9.3.1.3 Remove the petri dish from the drying oven, and place it near the balance. Keep the petri dish cover ajar, but keep it such
that th
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