ASTM D1401-21

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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: D1401 − 19 D1401 − 21
Standard Test Method for
Water Separability of Petroleum Oils and Synthetic Fluids
This standard is issued under the fixed designation D1401; 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.
1. Scope*
1.1 This test method covers measurement of the ability of petroleum oils or synthetic fluids to separate from water. Although
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developed specifically for steam-turbine oils having viscosities of 28.8 mm /s to 90 mm /s at 40 °C, this test method may be used
to test oils of other types having various viscosities and synthetic fluids at other test temperatures. It is recommended, however,
that the test temperature be raised to 82 °C 6 1 °C when testing products more viscous than 90 mm /s at 40 °C. For higher
viscosity oils where there is insufficient mixing of oil and water, Test Method D2711 is recommended. Other test temperatures such
as 25 °C may also be used. A 1 % sodium choloride (NaCl) solution or synthetic seawater may be used in place of distilled water
when testing certain oils or fuels used in marine applications.
1.2 When testing synthetic fluids whose relative densities are greater than that of water, the procedure is unchanged, but it should
be noted that the water will probably float on the emulsion or liquid.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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. For specific warning statements, see Section 7.
1.5 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:
D665 Test Method for Rust-Preventing Characteristics of Inhibited Mineral Oil in the Presence of Water
D1141 Practice for Preparation of Substitute Ocean Water
D1193 Specification for Reagent Water
D2711 Test Method for Demulsibility Characteristics of Lubricating Oils
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.C0 on Turbine Oils.
Current edition approved Nov. 1, 2019Oct. 1, 2021. Published November 2019December 2021. Originally approved in 1964. Last previous edition approved in 20182019
as D1401 – 18b.D1401 – 19. DOI: 10.1520/D1401-19.10.1520/D1401-21.
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
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2.2 ISO Standards:
BS EN ISO 3696:1995 Water for analytical laboratory use—Specification and test methods
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, see Terminology D4175.
3.1.2 emulsion, n—a suspension of fine globules of one or more liquids in another liquid.
3.1.3 interface, n—a common boundary between different phases of a substance.
3.1.4 phase separation, n—the formation of two layers, an aqueous constituent and a hydrophobic constituent, separated by either
a common boundary or a layer of emulsion; typically, the aqueous portion will be the lower phase, but for certain fluids whose
relative densities are greater than that of water, the aqueous portion will be the upper phase.
4. Summary of Test Method
4.1 A test specimen consisting of a 40 mL sample and a 40 mL quantity of distilled water, or 1 % sodium chloride (NaCl) solution
or synthetic seawater are stirred for 5 min in a graduated cylinder at 54 °C or 82 °C, depending upon the viscosity of the test
specimen or sample specification. The time required for the separation of the emulsion thus formed is recorded either after every
5 min or at the specification time limit. If complete separation or emulsion reduction to 3 mL or less does not occur after standing
for 30 min or some other specification time limit, the volumes of oil (or fluid), water, and emulsion remaining at the time are
reported.
5. Significance and Use
5.1 This test method provides a guide for determining the water separation characteristics of oils subject to water contamination
and turbulence. It is used for specification of new oils and monitoring of in-service oils.
6. Apparatus
6.1 Cylinder, 100 mL, graduated in 1.0 mL divisions (divisions starting at 1.0 mL or 5.0 mL), made of glass, heat-resistant glass,
like borosilicate glass, or a chemical equivalent. The inside diameter shall be no less than 27 mm and no more than 30 mm
throughout its length, measured from the top to a point 6 mm from the bottom of the cylinder. The overall height of the cylinder
shall be 225 mm to 260 mm. The graduation shall not be in error by more than 1 mL at any point on the scale.
6.2 Heating Bath, sufficiently large and deep to permit the immersion of at least two test cylinders in the bath liquid up to their
85 mL graduations. The bath shall be capable of being maintained at a test temperature to within 61 °C. The cylinder shall be
secured in a position so that the longitudinal axis of the paddle corresponds to the vertical center line of the cylinder during the
stirring operation. It is recommended that the bath be constructed with at least one transparent side that allows for clear visual
inspection of the oil (fluid), water, and emulsion layer volumes while the cylinder remains immersed in the bath.
6.3 Stirring Paddle, made of chromium-plated or stainless steel and conforming to the following dimensions:
Length, mm 120 ± 1.5
Width, mm 19 ± 0.5
Thickness, mm 1.5 ± 0.15
Radius of curvature of 1.6 max
paddle corners, mm
It is mounted on a vertical shaft of similar metal, approximately 6 mm in diameter, connected to a drive mechanism which rotates
the paddle on its longitudinal axis at 1500 rpm 6 15 rpm. The apparatus is of such design that, when the cylinder is clamped in
position and the paddle assembly is lowered into the cylinder, a positive stop engages and holds the assembly when the lower edge
of the paddle is 6 mm from the bottom of the cylinder. During the operation of the stirrer, the center of the bottom edge of the
paddle shall not deviate more than 1 mm from the axis of rotation. When not in operation, the paddle assembly can be lifted
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://www.iso.ch.
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vertically to clear the top of the graduated cylinder. (Warning—Paddle edges may be very sharp. Handle with care.) (Warning—A
protective shield may be used to cover the rotating shaft of the stirrer.)
NOTE 1—Soldering material used to join the stirrer and paddle may deteriorate or corrode over time and lead to additional emulsion formation (which
may be very stable and impact quality). Careful inspection of the union or use of a stirring paddle and shaft made of a single piece of metal is
recommended.
6.4 Spatula or Wiper, with or without inert rod support, composed of a material such as rubber, that is resistant to the oil or fluid.
7. Reagents
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall 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 Reagent Water—Unless otherwise indicated, reference to water shall be understood to mean distilled, deionized water as
defined by Type I or Type II in Specification D1193 or Grade 3 in BS EN ISO 3696:1995.
7.3 Acetone, (Warning—Health hazard, Flammable.)
7.4 Toluene, (Warning—Flammable.) Solvents with similar cleaning and solvency characteristics may be substituted for toluene.
7.5 Detergent, free rinsing, anionic detergent with a pH of 9.5 to 11.
8. Sampling
8.1 The test is very sensitive to small amounts of contamination. Take samples in accordance with Practice D4057.
9. Preparation of Apparatus
9.1 Clean the graduated cylinder by removing any film of oil (or fluid) with a thorough rinsing with toluene or solvent with similar
cleaning and solvency characteristics followed by a wash first with acetone and then with tap water. Clean the glassware with a
suitable detergent (7.5). Rinse with tap water. Soak the cylinder in the detergent for at least 24 h. Rinse thoroughly with tap water
and then with reagent water.
9.1.1 Check the glassware for cleanliness by adding reagent water to the cylinder and inverting it to drain the water. If the water
drains with a smooth sheeting action and leaves behind no droplets, the glassware is clean for use. An additional soak in a mildly
acidic solution may be necessary.
NOTE 2—Alternatively, new glassware may be used, provided that they are thoroughly rinsed with reagent water and meet the cleanliness defined by the
sheeting action as described in 9.1.1.
9.2 Clean the stirring paddle and shaft with absorbent cotton or tissue wet with toluene or solvent with similar cleaning and
solvency characteristics and air dry. Care shall be taken not to bend or misalign the paddle assembly during the cleaning operation.
10. Procedure
10.1 Heat the bath liquid to 54 °C 6 1 °C, 82 °C 6 1 °C or specified test temperature and maintain it at that temperature
throughout the test. Add reagent water to the graduated cylinder to reach the 40 mL mark when at test temperature. Typically
39.5 mL of water at room temperature will expand to the 40 mL mark once the cylinder is placed in the bath at 54 °C; 39 mL if
heating the sample to 82 °C. Invert the sample several times in the original container. Do not pour, shake, or stir samples to any
ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference Materials, American Chemical Society, Washington, DC. For
suggestions on the testing of reagents not listed by the American Chemical Society, see Analar 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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greater extent than necessary to prevent air entrainment. Pour the oil (or fluid) under test into the same cylinder until the top level
of the oil reaches the 80 mL mark on the cylinder when at test temperature.
10.2 If initial volumetric measurements are made at room temperature, expansion occurring at the elevated test temperature will
have to be considered. For example, there will be a total volumetric expansion of about 2 mL to 3 mL at 82 °C. Corrections to each
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