ASTM D2112-15(2023)

Standard Test Method for Oxidation Stability of Inhibited Mineral Insulating Oil by Pressure Vessel

SCOPE
1.1 This test method covers and is intended as a rapid method for the evaluation of the oxidation stability of new mineral insulating oils containing a synthetic oxidation inhibitor. This test is considered of value in checking the oxidation stability of new mineral insulating oils containing 2,6-ditertiary-butyl para-cresol or 2,6-ditertiary-butyl phenol, or both, in order to control the continuity of this property from shipment to shipment. The applicability of this procedure for use with inhibited mineral insulating oils of more than 12 cSt at 40 °C (approximately 65 SUS at 100 °F) has not been established.  
1.2 The values stated in SI units are to be regarded as standard except where there is no direct equivalent for hardware designed on the inch-pound unit basis.  
1.3 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. (See warning in 6.7.)  
1.4 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.

General Information

• Status: Published
• Publication Date: 30-Nov-2023
• ICS: 29.040.10 - Insulating oils
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.06 - Chemical Test

Relations

• Replaces: ASTM D2112-15 - Standard Test Method for Oxidation Stability of Inhibited Mineral Insulating Oil by Pressure Vessel
• Effective Date: 01-Dec-2023
• Referred By: ASTM D2440-13(2021) - Standard Test Method for Oxidation Stability of Mineral Insulating Oil
• Effective Date: 01-Dec-2023
• Referred By: ASTM D5222-23 - Standard Specification for Less Flammable High Molecular Weight Hydrocarbon Mineral Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Referred By: ASTM D117-22 - Standard Guide for Sampling, Test Methods, and Specifications for Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Referred By: ASTM D3487-16e1 - Standard Specification for Mineral Insulating Oil Used in Electrical Apparatus
• Effective Date: 01-Dec-2023
• Referred By: ASTM D8180-23 - Standard Specification for Rerefined Mineral Insulating Liquid Used in Electrical Apparatus
• Effective Date: 01-Dec-2023

Overview

ASTM D2112-15(2023), titled Standard Test Method for Oxidation Stability of Inhibited Mineral Insulating Oil by Pressure Vessel, is an international standard developed by ASTM International. This test method provides a rapid and practical approach for evaluating the oxidation stability of new mineral insulating oils that contain synthetic oxidation inhibitors. It is particularly valuable for quality control, ensuring that the oxidation stability of insulating oils remains consistent across production batches.

The standard is essential for manufacturers and users of electrical insulating oils-often used in transformers and high-voltage equipment-to verify product quality before use. Maintaining stable oxidation characteristics ensures the longevity and reliability of insulating oil in critical applications.

Key Topics

• Scope of Application: The method specifically targets new mineral insulating oils formulated with synthetic inhibitors such as 2,6-ditertiary-butyl para-cresol or 2,6-ditertiary-butyl phenol. It is not validated for oils with viscosities greater than 12 cSt at 40°C.
• Test Method Summary: An oil sample is subjected to accelerated aging in a rotating pressure vessel with oxygen, water, and a copper catalyst, under controlled temperature and pressure. The time for a specified pressure drop is measured to evaluate oxidation stability.
• Repeatability and Reproducibility: The method includes criteria for assessing duplicate and interlaboratory results, ensuring that outcomes are consistent and reliable for quality assurance.
• Safety and Environmental Practices: Users must establish appropriate safety, health, and environmental protocols, as the test involves reactive chemicals and pressurized oxygen.
• International Harmonization: Developed in line with WTO Technical Barriers to Trade (TBT) Committee principles, ensuring global recognition and applicability.

Applications

ASTM D2112 supports a range of industries and stakeholders, including:

• Transformer Oil Manufacturers: Enables rapid quality control of mineral insulating oils, ensuring batches meet oxidation stability requirements before shipment.
• Electrical Utilities and Equipment Operators: Assures that only high-stability insulating oil is used, reducing maintenance costs and preventing equipment failures.
• Laboratory and Testing Services: Provides a standard, repeatable test methodology for third-party testing and certification.
• Regulatory and Compliance Departments: Supports adherence to procurement and industry standards for insulating oil performance.

Practical applications include routine screening of new insulating oil shipments, confirming the effectiveness of specific oxidation inhibitors, and maintaining records demonstrating compliance for internal and external audits.

Related Standards

The effectiveness of ASTM D2112 is often complemented by related ASTM standards and industry documents, such as:

• ASTM D3487 - Standard Specification for Mineral Insulating Oil Used in Electrical Apparatus
• ASTM D2440 - Test Method for Oxidation Stability of Mineral Insulating Oil (Gas Evolution Method)
• ASTM D924 - Standard Test Method for Dissipation Factor and Relative Permittivity of Liquid Insulating Materials
• IEC 60296 - Fluids for Electrotechnical Applications-Uninhibited and Inhibited Mineral Insulating Oils

Referencing these related standards can help ensure a holistic approach to insulating oil quality and electrical equipment reliability.

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Keywords: ASTM D2112, oxidation stability, mineral insulating oil, pressure vessel test, synthetic oxidation inhibitor, transformer oil, electrical insulating liquids, oil quality testing, ASTM standards, insulating oil evaluation

Standards Content (Sample)

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.
Designation: D2112 − 15 (Reapproved 2023)
Standard Test Method for
Oxidation Stability of Inhibited Mineral Insulating Oil by
Pressure Vessel
This standard is issued under the fixed designation D2112; 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 E1 Specification for ASTM Liquid-in-Glass Thermometers
1.1 This test method covers and is intended as a rapid
3. Summary of Test Method
method for the evaluation of the oxidation stability of new
3.1 The test specimen is agitated by rotating axially at
mineral insulating oils containing a synthetic oxidation inhibi-
100 r ⁄min at an angle of 30° from the horizontal, under an
tor. This test is considered of value in checking the oxidation
initial oxygen pressure of 620 kPa (90 psi), in a stainless steel
stability of new mineral insulating oils containing 2,6-
or copper vessel (for rapid temperature equilibrium), with a
ditertiary-butyl para-cresol or 2,6-ditertiary-butyl phenol, or
glass test specimen container and copper catalyst coil, in the
both, in order to control the continuity of this property from
presence of water, at a bath temperature of 140 °C. The time
shipment to shipment. The applicability of this procedure for
for an oil to react with a given volume of oxygen is measured;
use with inhibited mineral insulating oils of more than 12 cSt
completion of the test is indicated by a specific drop in
at 40 °C (approximately 65 SUS at 100 °F) has not been
pressure.
established.
1.2 The values stated in SI units are to be regarded as
4. Significance and Use
standard except where there is no direct equivalent for hard-
4.1 This is a control test of oxidation stability of new,
ware designed on the inch-pound unit basis.
inhibited mineral insulating oils for determining the induction
1.3 This standard does not purport to address all of the
period of oxidation inhibitors under prescribed accelerated
safety concerns, if any, associated with its use. It is the
aging conditions. There is no proven correlation between oil
responsibility of the user of this standard to establish appro-
performance in this test and performance in service. However,
priate safety, health, and environmental practices and deter-
the test method may be used to check the continuity of
mine the applicability of regulatory limitations prior to use.
oxidation stability of production oils.
(See warning in 6.7.)
5. Apparatus
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
5.1 Oxidation Vessel—Glass test specimen container with
ization established in the Decision on Principles for the
cover and catalyst coil, pressure gauge, thermometer, test bath,
Development of International Standards, Guides and Recom-
and accessories as described in Annex A1. The assembled
mendations issued by the World Trade Organization Technical
apparatus is shown in Fig. 1, and its design shown schemati-
Barriers to Trade (TBT) Committee.
cally in Fig. 2.
2. Referenced Documents
6. Reagents and Materials
2.1 ASTM Standards:
6.1 Purity of Reagents—Use reagent grade chemicals in all
B1 Specification for Hard-Drawn Copper Wire
tests. Unless otherwise indicated, all reagents shall conform to
the specifications of the Committee on Analytical Reagents of
the American Chemical Society, where such specifications are
This test method is under the jurisdiction of ASTM Committee D27 on
available.
Electrical Insulating Liquids and Gases and is the direct responsibility of Subcom-
mittee D27.06 on Chemical Test.
Current edition approved Dec. 1, 2023. Published December 2023. Originally
approved in 1962. Last previous edition approved in 2015 as D2112 – 15. DOI: ACS Reagent Chemicals, Specifications and Procedures for Reagents and
10.1520/D2112-15R23. Standard-Grade Reference Materials, American Chemical Society, Washington,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or DC. For suggestions on the testing of reagents not listed by the American Chemical
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
Standards volume information, refer to the standard’s Document Summary page on U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
the ASTM website. copeial Convention, Inc. (USPC), Rockville, MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2112 − 15 (2023)
and container to the nearest 0.1 g and record the weight. Wash
the coil by filling the container above the level of the coil with
10 % hydrochloric acid by volume for 30 s. Discard the acid
and rinse the coils three times with tap water followed by three
times with distilled water. Reweigh the coil and container and
determine by difference the water retained in the system. The
coils are now ready for use. This procedure has been found to
be acceptable for treatment of commercially available,
prepackaged, preformed coils that meet the requirement de-
scribed in this test method. Use a new coil for each test
specimen.
8.3 Cleaning of Vessel—Wash the vessel body, lid, and
inside of vessel stem with hot detergent solution and with
water. Rinse inside of stem with 2–propanol and blow dry with
clean dry air. An alternative cleaning solution is the use of a
50/50 volumetric blend of methanol and acetone; it has been
FIG. 1 Rotating Vessel Oxidation Test Apparatus
found to be effective in cleaning sludge from the vessel. If the
vessel body, lid, or inside of stem smells sour after simple
cleaning, wash with alcoholic KOH solution and repeat as
6.2 Hydrochloric Acid, 10 vol %.
before (see Note 1).
6.3 Silicon Carbide Abrasive Cloth, 100-grit with cloth
backing. NOTE 1—Insufficient cleaning of the vessel may adversely affect test
results.
6.4 Acetone, ACS grade.
6.5 2-Propanol, 99 vol %, refined.
9. Procedure
6.6 Liquid Detergent.
9.1 Charging—Weigh 50 g 6 0.5 g of oil sample into the
container, add 5 mL of distilled water, and cover with a 51 mm
6.7 Oxygen, 99.5 %, with pressure regulation above 620 kPa
(2-in.) watch glass or a 57.2 mm (2 ⁄4-in.) PTFE disk with one
(90 psi). (Warning—Oxygen vigorously accelerates combus-
or four holes and retaining spring. If rinse water is present in
tion.)
the container, compensate for it by using less added water
6.8 Potassium Hydroxide, Alcohol Solution (1 mass %)—
based on the water retention determined in 8.2. Add 5 mL of
Dissolve 7.93 g of potassium hydroxide (KOH) pellets in 1 L
distilled water to the vessel and slide the test specimen
of 99 % refined 2-propanol.
container and cover lid into the vessel body (see Note 2). Apply
6.9 Silicone Stopcock Grease.
a thin coating of silicone stopcock grease to the O-ring vessel
seal located in the gasket groove of the vessel lid to provide
6.10 Wire Catalyst—AWG No. 14 (approximately
lubrication, and insert the lid into the vessel body. Place the
1.628 mm diameter) electrolytic copper wire 99.9 % purity,
vessel cap over the vessel stem, and tighten by hand. Cover the
conforming to Specification B1. Soft-drawn copper wire of an
threads of the gauge-nipple with a thin coating of stopcock
equivalent grade may also be used.
grease or TFE-fluorocarbon, or both, and screw the gauge into
the top-center tap of the vessel stem. A pressure transducer can
7. Hazards
also be used. Flush the vessel twice with oxygen supplied to
7.1 Consult Safety Data Sheets for all materials used in this
the vessel at 620 kPa (90 psi) and release to the atmosphere.
test method.
Adjust the regulating valve on the oxygen supply tank to
620 kPa (90 psi) at a room temperature of 25 °C. For each
8. Preparation of Apparatus
2.8 °C above or below this temperature, add or subtract 7 kPa
8.1 Catalyst Preparation—Immediately before use, polish
(1 psi) unit to attain the required initial pressure. Fill the vessel
the copper wire with silicon carbide abrasive cloth and wipe
to this required pressure and close the inlet valve securely by
free from abrasives with a clean dry cloth. Wind approximately
hand. If desired, test the vessel for leaks by immersion in water
3 m of the wire into a coil having an outside diameter of 44 mm
(see Note 3). Prepare a duplicate test specimen in exactly the
to 48 mm and stretched to a height of 40 mm to 42 mm. Clean
same way.
the coil thoroughly with acetone and allow it to air-dry.
NOTE 2—The water between the vessel well and the test specimen
Immediately after air drying, insert the coil with a twisting
container aids heat transfer.
motion into the glass test specimen container. Handle the coil
NOTE 3—If the vessel was immersed in water to check for leaks, dry the
only with clean tongs to avoid contamination. Weigh the coil
outside of the wet vessel by any convenient means such as an air blast or
and the container to the nearest 0.1 g and record the weight.
a towel. Such drying is advisable to prevent subsequent introduction of
Prepare a new coil for each test specimen. free water into the hot oil bath, which would cause sputtering.
8.2 Alternative Method of Catalyst Preparation—Wind ap- 9.2 Oxidation—Bring the heating bath to the test tempera-
proximately 3 m of copper wire into a coil of the dimensions ture of 140 °C while the stirrer is in operation. Insert the
specified in 8.1, and add to the glass container. Weigh the coil vessels into the rotating carriages and note the time. If an
D2112 − 15 (2023)
FIG. 2 Schematic Drawing of Rotary Vessel
the vessels and allows the vessel pressure to reach a plateau within 15 min
auxiliary heater is used, keep it on for the first 5 min of the run
as shown in Curve A o
...