ASTM D1934-20

Standard Test Method for Oxidative Aging of Electrical Insulating Liquids by Open-Beaker Method

SIGNIFICANCE AND USE
5.1 Open-beaker oxidative aging methods have been used for many years in laboratories of insulating liquid companies, electrical equipment manufacturers, and electric utility companies interested in the stability of electrical insulating liquids under oxidative conditions. They are particularly useful as a check on the continuity of production and shipment of insulating liquids. They are also useful as process and product checks for applicable type insulating liquids.  
5.2 Specification limits for insulating liquids subjected to open-beaker oxidative aging by this method are established by agreement between individual producers and consumers of applicable type insulating liquids. These properties of the insulating liquid involved in specification limits for aging stability may be measured after the oxidative aging (and sometimes before aging) by appropriate test methods such as Test Methods D924, D971, D1169, and D974 or D664. Other test methods such as D445 can be used when deemed appropriate.
SCOPE
1.1 This test method covers two procedures for subjecting electrical insulating liquids to oxidative aging:  
1.1.1 Procedure A, without a metal catalyst, and  
1.1.2 Procedure B, with a metal catalyst.  
1.2 This test method is applicable to insulating liquids used as impregnating or pressure media in electrical power transmission cables if less than 10 % of the insulating liquid evaporates during the aging procedures. It applies and is generally useful primarily in the evaluation and quality control of unused insulating liquids, either inhibited or uninhibited.  
1.3 This test method is applicable to study the long-term behavior of an insulating liquid being considered for free breathing transformers. An unsealed vessel aging procedure, in presence of air or oxygen, allows greatly increased oxidation rate of the liquid. This procedure is rapid and provides a controlled thermal stress assessment.  
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.  
1.5 An open beaked test shall only be carried out on liquids with flash points at or above 130°C or 15°C above the oven temperature. 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 7.5 for a specific warning statement.  
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.

General Information

• Status: Published
• Publication Date: 30-Nov-2020
• ICS: 29.040.10 - Insulating oils
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.06 - Chemical Test

Relations

• Refers: ASTM D445-24 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Apr-2024
• Refers: ASTM D924-23 - Standard Test Method for Dissipation Factor (or Power Factor) and Relative Permittivity (Dielectric Constant) of Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Refers: ASTM D923-15(2023) - Standard Practices for Sampling Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Refers: ASTM D445-23 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Nov-2023
• Refers: ASTM D971-20 - Standard Test Method for Interfacial Tension of Insulating Liquids Against Water by the Ring Method
• Effective Date: 01-Apr-2020
• Refers: ASTM D1169-19a - Standard Test Method for Specific Resistance (Resistivity) of Electrical Insulating Liquids
• Effective Date: 01-Oct-2019
• Refers: ASTM D1169-19 - Standard Test Method for Specific Resistance (Resistivity) of Electrical Insulating Liquids
• Effective Date: 01-Apr-2019
• Refers: ASTM E145-19 - Standard Specification for Gravity-Convection and Forced-Ventilation Ovens
• Effective Date: 01-Mar-2019
• Refers: ASTM D664-11a(2017) - Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration
• Effective Date: 01-May-2017
• Refers: ASTM D445-16 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 15-Dec-2016
• Refers: ASTM D923-15 - Standard Practices for Sampling Electrical Insulating Liquids
• Effective Date: 01-Oct-2015
• Refers: ASTM D974-14e1 - Standard Test Method for Acid and Base Number by Color-Indicator Titration
• Effective Date: 01-Dec-2014
• Refers: ASTM D445-14 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Jul-2014
• Refers: ASTM D445-14e1 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Jul-2014
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014

Overview

ASTM D1934-20: Standard Test Method for Oxidative Aging of Electrical Insulating Liquids by Open-Beaker Method is a widely recognized procedure developed by ASTM International. This standard is essential for evaluating the oxidative aging stability of electrical insulating liquids (also known as transformer oils or dielectric fluids), which play a critical role in the reliability and safety of electrical power equipment. The method covers two procedures - one with and one without the use of a metal catalyst - to simulate and accelerate oxidative aging under laboratory conditions.

The oxidative stability of insulating liquids is vital for the longevity and performance of transformers, cables, and other electrical devices. Using the open-beaker method allows engineers and quality control professionals to detect variations in product quality, production consistency, and shipping stability of insulating liquids.

Key Topics

• Oxidative Aging Assessment: Exposes insulating liquids to elevated temperatures and air or oxygen, simulating accelerated aging conditions relevant to real-world applications.
• Procedure A and B:
  • Procedure A: Aging without a metal catalyst, for baseline oxidative stability assessment.
  • Procedure B: Includes a metal catalyst (such as copper) to accelerate oxidation and evaluate the impact of metals that may be present in electrical equipment.
• Sample Suitability: Applicable to insulating liquids used as impregnating or pressure media in power transmission cables, especially when less than 10% evaporates during testing.
• Rapid, Controlled Testing: Provides a controlled thermal stress environment, allowing for faster evaluation of long-term stability.
• Safety Considerations: Only suitable for liquids with flash points at or above 130°C, or at least 15°C above oven temperature; correct laboratory safety and environmental practices are essential.

Applications

• Quality Control: Ensures consistency across production batches of electrical insulating liquids, helping manufacturers and utilities maintain high equipment reliability.
• Product Development and Selection: Assesses long-term oxidative stability for selecting or formulating new dielectric fluids for use in transformers, switchgear, and power cables.
• Specification Compliance: Used in agreements between suppliers and customers to set performance specifications for insulating liquids, verifying compliance through standardized oxidative aging results.
• Process Monitoring: Supports routine checks during production and prior to shipment, identifying potential issues that could affect performance in service (such as corrosion, sludge formation, or dielectric breakdown).
• Transformer and Cable Evaluation: Particularly useful for evaluating liquids intended for free-breathing transformers, where exposure to air is a significant factor in aging.

Related Standards

Users of ASTM D1934-20 often complement their aging tests with additional analyses of electrical and chemical properties. Relevant referenced standards include:

• ASTM D924: Test Method for Dissipation Factor and Relative Permittivity of Electrical Insulating Liquids - crucial for dielectric property assessment.
• ASTM D971: Test Method for Interfacial Tension of Insulating Liquids Against Water - important for evaluating contamination or degradation.
• ASTM D1169: Test Method for Specific Resistance (Resistivity) of Electrical Insulating Liquids - indicating electrical integrity.
• ASTM D974 and D664: Test Methods for Acid and Base Number - provide insight on chemical changes due to aging.
• ASTM D445: Test Method for Kinematic Viscosity - sometimes used for additional property checks.
• ASTM D923: Practices for Sampling Electrical Insulating Liquids - ensures representative and contamination-free sample collection.

Conclusion

ASTM D1934-20 is a critical standard for laboratories, manufacturers, and users in the electrical power industry. By applying the open-beaker oxidative aging test, stakeholders can maintain quality, ensure regulatory compliance, and optimize the performance and lifespan of electrical insulating liquids. For best results, combine this method with related ASTM test methods that provide a comprehensive profile of fluid stability and suitability for demanding electrical applications.

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: D1934 − 20
Standard Test Method for
Oxidative Aging of Electrical Insulating Liquids by Open-
Beaker Method
This standard is issued under the fixed designation D1934; 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
1.1 This test method covers two procedures for subjecting
2.1 ASTM Standards:
electrical insulating liquids to oxidative aging:
D445 Test Method for Kinematic Viscosity of Transparent
1.1.1 Procedure A, without a metal catalyst, and
and Opaque Liquids (and Calculation of Dynamic Viscos-
1.1.2 Procedure B, with a metal catalyst.
ity)
D664 Test Method for Acid Number of Petroleum Products
1.2 This test method is applicable to insulating liquids used
by Potentiometric Titration
as impregnating or pressure media in electrical power trans-
D923 Practices for Sampling Electrical Insulating Liquids
mission cables if less than 10 % of the insulating liquid
D924 Test Method for Dissipation Factor (or Power Factor)
evaporates during the aging procedures. It applies and is
and Relative Permittivity (Dielectric Constant) of Electri-
generally useful primarily in the evaluation and quality control
cal Insulating Liquids
of unused insulating liquids, either inhibited or uninhibited.
D971 Test Method for Interfacial Tension of Insulating
1.3 This test method is applicable to study the long-term
Liquids Against Water by the Ring Method
behavior of an insulating liquid being considered for free
D974 Test Method for Acid and Base Number by Color-
breathing transformers.An unsealed vessel aging procedure, in
Indicator Titration
presence of air or oxygen, allows greatly increased oxidation
D1169 Test Method for Specific Resistance (Resistivity) of
rate of the liquid. This procedure is rapid and provides a
Electrical Insulating Liquids
controlled thermal stress assessment.
E145 Specification for Gravity-Convection and Forced-
1.4 The values stated in SI units are to be regarded as
Ventilation Ovens
standard. The values given in parentheses are for information
E177 Practice for Use of the Terms Precision and Bias in
only.
ASTM Test Methods
1.5 An open beaked test shall only be carried out on liquids
with flash points at or above 130°C or 15°C above the oven 3. Terminology
temperature. This standard does not purport to address all of
3.1 Definitions of Terms Specific to This Standard:
the safety concerns, if any, associated with its use. It is the
3.1.1 metal catalyst—any metal (for example, copper) that
responsibility of the user of this standard to establish appro-
eitherincreasestherateofoxidationoftheliquidorreactswith
priate safety, health, and environmental practices and deter-
the oxidation products to increase insulating liquid dielectric
mine the applicability of regulatory limitations prior to use.
loss.
See 7.5 for a specific warning statement.
1.6 This international standard was developed in accor- 3.1.2 oxidative aging—exposure of insulating liquid to oxy-
dance with internationally recognized principles on standard- gen under certain specified conditions.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 4. Summary of Test Method
mendations issued by the World Trade Organization Technical
4.1 A300 mLvolume of insulating liquid, contained in 400
Barriers to Trade (TBT) Committee.
mL beaker is aged for 96 h in a circulating-air oven controlled
at 115°C, either with or without the presence of catalyst.
This test method is under the jurisdiction of ASTM Committee D27 on
Electrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-
mittee D27.06 on Chemical Test. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 1, 2020. Published December 2020. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1962. Last previous edition approved in 2012 as D1934 – 95 (2012). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D1934-20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1934 − 20
5. Significance and Use means for oxidation of the liquid with or without a copper
catalyst. The approximate dimensions of a suitable beaker are
5.1 Open-beaker oxidative aging methods have been used
100 mmindepthand70mminsidediameter.Cleanthebeakers
for many years in laboratories of insulating liquid companies,
used in the aging test, and thoroughly dry before use. One
electrical equipment manufacturers, and electric utility compa-
recommended cleaning procedure is as follows: Remove re-
nies interested in the stability of electrical insulating liquids
sidual insulating liquid from the beaker by rinsing in mineral
under oxidative conditions. They are particularly useful as a
spirits or equivalent. Rinse thoroughly with an acid cleaning
check on the continuity of production and shipment of insu-
solution consisting of 3 parts nitric acid (HNO ) to 1 part
lating liquids. They are also useful as process and product
sulfuric acid (H SO ). Remove traces of cleaning solution by
2 4
checks for applicable type insulating liquids.
carefully rinsing with distilled water followed by rinsing with
5.2 Specification limits for insulating liquids subjected to
acetone and air drying. (Ammonium persulfate is also a
open-beaker oxidative aging by this method are established by
suitable cleaning reagent.)
agreement between individual producers and consumers of
applicable type insulating liquids. These properties of the
7. Reagents and Materials
insulating liquid involved in specification limits for aging
7.1 Purity of Reagents—Use reagent grade chemicals in all
stability may be measured after the oxidative aging (and
tests.Unlessotherwiseindicated,itisintendedthatallreagents
sometimes before aging) by appropriate test methods such as
shall conform to the specifications of the Committee on
Test Methods D924, D971, D1169, and D974 or D664. Other
Analytical Reagents of theAmerican Chemical Society, where
test methods such as D445 can be used when deemed appro-
such specifications are available.
priate.
7.2 Hydrochloric Acid, 10 % volume solution from concen-
6. Apparatus
trated hydrochloric acid.
6.1 Oven, electrically heated, thermostatically controlled,
7.3 Nitric Acid—Concentrated nitric acid (HNO ).
capable of maintaining a constant temperature of 115 6 1°C
7.4 Sulfuric Acid—Concentrated sulfuric acid (H SO ).
2 4
(239 6 2°F). Use an oven with a testing chamber large enough
7.5 Metal Catalyst with 15 cm of clean surface available
to test the anticipated number of test specimens at one time.A
for exposure to the insulating liquid for use in Procedure B. If
uniformity of temperature within 61 % of the differential
the metal catalyst is copper wire, it is convenient to wind an
between oven and ambient temperatures is required. (See Note
appropriate length into a loose hank which is then cleaned to
1.) Circulate air in the chamber with a low velocity fan during
remove insulating liquid, oxide, and the other extraneous
the aging period. The volume and condition of the circulated
matter. The metal catalyst may also be used in the form of
air is not considered to be critical enough to be recorded. It is
strips, but the strips require special attention to maintain the
recommended that the oven provide several air changes per
desired amount of exposed surface. One good method of
hour, and that vap
...

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: D1934 − 95 (Reapproved 2012) D1934 − 20
Standard Test Method for
Oxidative Aging of Electrical Insulating Petroleum Oils
Liquids by Open-Beaker Method
This standard is issued under the fixed designation D1934; 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
1.1 This test method covers two procedures for subjecting electrical insulating oilsliquids to oxidative aging:
1.1.1 Procedure A, without a metal catalyst, and
1.1.2 Procedure B, with a metal catalyst.
1.2 This test method is applicable to oils insulating liquids used as impregnating or pressure media in electrical power transmission
cables if less than 10 % of the oil insulating liquid evaporates during the aging procedures. It applies and is generally useful
primarily in the evaluation and quality control of unused oils, insulating liquids, either inhibited or uninhibited.
1.3 This test method is applicable to study the long-term behavior of an insulating liquid being considered for free breathing
transformers. An unsealed vessel aging procedure, in presence of air or oxygen, allows greatly increased oxidation rate of the
liquid. This procedure is rapid and provides a controlled thermal stress assessment.
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.5 An open beaked test shall only be carried out on liquids with flash points at or above 130°C or 15°C above the oven
temperature. 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. See 7.5 for a specific warning statement.
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:
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D664 Test Method for Acid Number of Petroleum Products by Potentiometric Titration
D923 Practices for Sampling Electrical Insulating Liquids
This test method is under the jurisdiction of ASTM Committee D27 on Electrical Insulating Liquids and Gasesand is the direct responsibility of Subcommittee D27.06
on Chemical Test.
Current edition approved Feb. 1, 2012Dec. 1, 2020. Published February 2012December 2020. Originally approved in 1962. Last previous edition approved in 20052012
as D1934 – 95 (2005).(2012). DOI: 10.1520/D1934-95R12.10.1520/D1934-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1934 − 20
D924 Test Method for Dissipation Factor (or Power Factor) and Relative Permittivity (Dielectric Constant) of Electrical
Insulating Liquids
D971 Test Method for Interfacial Tension of Insulating Liquids Against Water by the Ring Method
D974 Test Method for Acid and Base Number by Color-Indicator Titration
D1169 Test Method for Specific Resistance (Resistivity) of Electrical Insulating Liquids
E145 Specification for Gravity-Convection and Forced-Ventilation Ovens
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 metal catalyst—any metal (for example, copper) that either increases the rate of oxidation of the oilliquid or reacts with the
oxidation products to increase oil insulating liquid dielectric loss.
3.1.2 oxidative aging—exposure of oil insulating liquid to oxygen under certain specified conditions.
4. Summary of Test Method
4.1 A 300 mL volume of oil, insulating liquid, contained in 400 mL beaker is aged for 96 h in a circulating-air oven controlled
at 115°C, either with or without the presence of catalyst.
5. Significance and Use
5.1 Open-beaker oxidative aging methods have been used for many years in laboratories of oil insulating liquid companies,
electrical equipment manufacturers, and electric utility companies interested in the stability of electrical insulating oilsliquids under
oxidative conditions. They are particularly useful as a check on the continuity of production and shipment of insulating oils.liquids.
They are also useful as process and product checks for applicable type oils.insulating liquids.
5.2 Specification limits for oils insulating liquids subjected to open-beaker oxidative aging by this method are established by
agreement between individual producers and consumers of applicable type oils. insulating liquids. These properties of the oil
insulating liquid involved in specification limits for aging stability may be measured after the oxidative aging (and sometimes
before aging) by appropriate test methods such as Test MethodMethods D924, D971Test Method , D1169, and TestD974 Methodor
D664. Other test methods such as D445 can be used when deemed appropriate.
6. Apparatus
6.1 Oven, electrically heated, thermostatically controlled, capable of maintaining a constant temperature of 115 6 1°C (239 6
2°F). Use an oven with a testing chamber large enough to test the anticipated number of test specimens at one time. A uniformity
of temperature within 61 % of the differential between oven and ambient temperatures is required. (See Note 1.) Circulate air in
the chamber with a low velocity fan during the aging period. The volume and condition of the circulated air is not considered to
be critical. critical enough to be recorded. It is recommended that the oven provide several air changes per hour, and that vapors
and fumes be removed if present.
NOTE 1—Refer to Specification E145 for the measurement of the temperature uniformity of the oven.
6.1.1 Procedure A—For test specimens aged in the absence of a metal catalyst the choice of a suitable oven design is not critical.
Either fixed- or rotating-shelf stage ovens of satisfactory thermal quality may be used, although a rotating-shelf oven is preferred.
If a fixed-shelf oven is used, it is recommended that test specimen positions within the oven be changed periodically (for example,
at daily intervals) to minimize the effects of any temperature differentials that may exist.inter-sample differentials.
6.1.2 Procedure B—When a metal catalyst, such as copper, is used, the rate of oxidation usually is increased, and the procedure
becomes sensitive to movement of the oil insulating liquid past the metal surface. An aging oven equipped with a slowly rotating
shelf has been adopted for uniformity when a metal catalyst is used. Other oven designs having satisfactory thermal quality and
a rotating shelf may be used.
A suitable type oven is described in “Life Test for Transformer Oils,” Appendix to Report of Committee D09 on Electrical and Electronic Insulating Materials,
Proceedings, ASTM, Vol 27, Part I, 1927 pp. 541–549.
D1934 − 20
6.2 Beaker, borosilicate glass, low-form, of 400-mL capacity. A watch-glass cover over the beaker is required, which prevents
particles from dropping into the liquid sample. A watch-glass top on a beaker still allows exchange of air as the means for oxidation
of the liquid with or without a copper catalyst. The approximate dimensions of a suitable beaker are 100 mm in depth and 70 mm
inside diameter. Clean the beakers used in the aging test, and thoroughly dry before use. One recomme
...