ASTM D2532-22

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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: D2532 − 17 D2532 − 22
Standard Test Method for
Viscosity and Viscosity Change After Standing at Low
Temperature of Aircraft Turbine Lubricants
This standard is issued under the fixed designation D2532; 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 the determination of the kinematic viscosity of aircraft turbine lubricants at low temperature, and the
percent change of viscosity after a 3 h and a 72 h standing period at low temperature.
2 2
1.1.1 The range of kinematic viscosities covered by this test method is from 7700 mm /s to 14 000 mm /s at –40 °C and from 7000
2 2
mm /s to 17 500 mm /s at –51 °C. The precision has only been determined for those materials, kinematic viscosity ranges, and
temperatures as shown in the precision section. Kinematic viscosities and percent change of viscosity may be measured and
reported at other temperatures and other thermal soak period intervals as agreed by the contracting parties.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
2 2 -6 2
1.2.1 The SI unit used in this test method for Kinematic Viscosity is mm /s. For user reference, 1 mm /s = 10 m /s = 1 cSt.
1.3 Warning—Mercury has been designated by many regulatory agencies as a hazardous materialsubstance that can cause central
nervous system, kidney and liver damage. serious medical issues. Mercury, or its vapor, may has been demonstrated to be
hazardous to health and corrosive to materials. Caution should be taken Use caution when handling mercury and mercury
containing mercury-containing products. See the applicable product Material Safety Data Sheet (MSDS) for details and EPA’s
website—http://www.epa.gov/mercury/faq.htm—for additional information. Users should be aware (SDS) for additional informa-
tion. The potential exists that selling mercury and/or mercury containing products into your state or country may be prohibited by
law.or mercury-containing products, or both, is prohibited by local or national law. Users must determine legality of sales in their
location.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For specific hazard 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.
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
D02.07 on Flow Properties.
Current edition approved May 1, 2017Dec. 1, 2022. Published May 2017December 2022. Originally approved in 1966. Last previous edition approved in 20162017 as
D2532 – 16.D2532 – 17. DOI: 10.1520/D2532-17.10.1520/D2532-22.
*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
D2532 − 22
2. Referenced Documents
2.1 ASTM Standards:
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D446 Specifications and Operating Instructions for Glass Capillary Kinematic Viscometers
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and
Lubricants
E1 Specification for ASTM Liquid-in-Glass Thermometers
E563 Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
E644 Test Methods for Testing Industrial Resistance Thermometers
E1137 Specification for Industrial Platinum Resistance Thermometers
E1750 Guide for Use of Water Triple Point Cells
E2593 Guide for Accuracy Verification of Industrial Platinum Resistance Thermometers
E2877 Guide for Digital Contact Thermometers
2.2 Other Documents:
MIL-PRF-7808 Lubricating Oil, Aircraft Turbine Engine, Synthetic Base
MIL-PRF-23699 Lubricating Oil, Aircraft Turbine Engine, Synthetic Base, NATO Code Number O-156
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.1.2 digital contact thermometer (DCT), n——anan electronic device consisting of a digital display and associated temperature
sensing probe.
3.1.2.1 Discussion—
This device consists of a temperature sensor connected to a measuring instrument; this instrument measures the temperature-
dependent quantity of the sensor, computes the temperature from the measured quantity, and provides a digital output. This digital
output goes to a digital display and/or recording device that may be internal or external to the device. These devices are sometimes
referred to as “digital thermometers.”
3.1.2.2 Discussion—
PET is an acronym for portable electronic thermometers, a subset of digital contact thermometers (DCT).
4. Summary of Test Method
4.1 Kinematic viscosity and percent change is determined at low temperature using apparatus defined in Test Method D445 and
Specifications D446 at time intervals of 3 h and 72 h following an initial measurement at 35 min.
5. Significance and Use
5.1 Aircraft turbine lubricants, upon standing at low temperatures for prolonged periods of time, may show an increase in
kinematic viscosity. This increase may cause lubrication problems in aircraft engines. Thus, this test method is used to ensure that
the kinematic viscosity does not exceed the maximum kinematic viscosity in certain specifications for aircraft turbine lubricants.
6. Apparatus
6.1 Viscometers, drying tubes, low-temperature bath, thermometer, timer, secondary viscosity standard, filter, and cleaning
supplies are described in detail in Test Method D445.
6.2 Viscometer—The viscometer shall meet the requirements of Test Method D445 and Specifications D446 and be of the type in
which the sample can be rerun without cleaning the viscometer. Suitable holders should be used. For convenience it is
recommended that the viscometer size be chosen to keep the efflux time between 200 s and 1000 s.
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D2532 − 22
NOTE 1—Consult Specifications D446 regarding calibration constant correction for the actual test temperature when using Specifications D446
viscometers that are not suspended level types.
6.3 Drying Tubes—Fit the viscometer openings with drying tubes filled with indicating silica gel, using cotton at top and bottom
to hold the loosely packed desiccant in place. Provide a cross-connection on the viscometer side of the drying tubes (which can
be closed by a pinch clamp or stopcock while liquid is being drawn into the efflux bulb) so that the restriction to air flow will not
cause error. Replace the silica gel when a lavender color is noticeable.
6.4 Viscosity Temperature Bath—The constant-temperature bath must be capable of holding several viscometers at once. It must
have adequate stirring of the liquid medium (Note 2) and balance between heat losses such that the bath temperature can be
maintained at the required temperature 60.03 °C.
NOTE 2—Isopropanol or other clear, low-freezing point liquid may be used as a bath liquid.
6.5 Temperature Measuring Device—Use either a digital contact thermometer as described in 6.5.2 with equal or better accuracy
or a calibrated ASTM Kinematic Viscosity Test Thermometer such as 73C (–40 °C) or 74C or 43C (–51 °C) conforming to the
requirements as prescribed in Specification E1 which have an accuracy after correction of 60.03 °C or better. The ASTM 74C
thermometer has a specification between –55.4 °C and –52.6 °C but is available from some suppliers with the scale expanded to
cover –51 °C. The 43C thermometer is only graduated in 0.1 °C increments so interpretation at midpoints between the lines may
be required.
6.5.1 When using liquid-in-glass thermometers, use a magnifying device to read the thermometer to the nearest ⁄5 division (for
example, 0.02 °C on thermometers graduated in 0.1 °C increments) to ensure that the required test temperature and temperature
control capabilities are met.
6.5.1.1 Check the thermometer’s ice point at least annually using an ice bath or a constant temperature bath against a reference
thermometer. If the corrected temperature reading error is greater than the temperature tolerance, then the thermometer must be
recalibrated.
6.5.2 When using a digital contact thermometer (DCT), the following requirements shall apply:
Criteria Minimum Requirements
DCT E2877 Class A
Display resolution 0.01 °C, recommended 0.001 °C
Display accuracy ±30 mK (±0.03 °C) for combined probe and
sensor
Sensor type RTD, such as a PRT or thermistor
Drift less than 10 mK (0.01 °C) per year
Response time less than or equal to 6 s as defined in Speci-
fication E1137
Linearity 10 mK over range of intended use
Calibration Report The DCT shall have a report of temperature
calibration traceable to a national calibration
or metrology standards body issued by a
competent calibration laboratory with demon-
strated competency in temperature calibra-
tion. An ISO 17025 accredited laboratory with
temperature calibration in its accreditation
scope would meet this requirement.
Calibration Data The calibration report shall include at least 3
calibration temperatures at least 5 °C apart
which are appropriate for its intended use.
6.5.2.1 For a constant temperature bath employed, the DCT probe shall be immersed by more than its minimum immersion depth
in a constant temperature bath so that the center of the probe’s sensing region is at the same level as the lower half of the working
capillary provided the probe’s minimum immersion depth is met and is no less than indicated on the calibration certificate. The
end of the probe sheath shall not extend past the bottom of the viscometer. It is preferable for the center of the sensing element
to be located at the same level as the lower half of the working capillary as long as the minimum immersion requirements are met.
NOTE 3—With respect to DCT probe immersion depth, a procedure is available in Test Methods E644, Section 7 (Minimum Immersion Length Test), for
determining
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