ASTM D5374-22a

Standard Test Methods for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation

SIGNIFICANCE AND USE
4.1 Ovens used for thermal evaluation of insulating materials are to be capable of maintaining uniform conditions of temperature and air circulation over the extended periods of time that are required for conducting these tests. Specification D5423 specifies the permissible variations from absolute uniformity that have been accepted internationally for these ovens. These test methods include procedures for measuring these variations and other specified characteristics of the ovens.
SCOPE
1.1 These test methods cover procedures for evaluating the characteristics of forced-convection ventilated electrically-heated ovens, operating over all or part of the temperature range from 20 °C above the ambient temperature to 500 °C and used for thermal endurance evaluation of electrical insulating materials.  
1.2 These test methods are based on IEC Publication 60216-4-1, and are technically identical to it. This compilation of test methods and an associated specification, D5423, have replaced Specification D2436.  
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.  
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: 31-Aug-2022
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.17 - Fire and Thermal Properties

Relations

• Refers: ASTM D1711-24 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Mar-2024
• Refers: ASTM D1711-15 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2015
• Refers: ASTM D1711-14a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2014
• Refers: ASTM D1711-14 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2014
• Refers: ASTM D1711-13 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2013
• Refers: ASTM D1711-11a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Aug-2011
• Refers: ASTM D1711-08 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2008
• Refers: ASTM D5423-93(2005) - Standard Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation (Withdrawn 2014)
• Effective Date: 01-Sep-2005
• Refers: ASTM D1711-02 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 10-Mar-2002
• Refers: ASTM D1711-99 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 10-Oct-1999
• Refers: ASTM D5423-93(1999) - Standard Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation
• Effective Date: 10-Mar-1999

Overview

ASTM D5374-22a specifies standardized test methods for evaluating the performance of forced-convection laboratory ovens used in the thermal endurance testing of electrical insulating materials. These ovens, which are ventilated and electrically heated, must maintain uniform temperature and air circulation over extended periods, ensuring accurate and consistent results essential for materials testing in the electrical and electronics industries.

The standard covers ovens operating from 20°C above ambient temperature up to 500°C. Designed to align with international practices, ASTM D5374-22a is technically identical to IEC 60216-4-1, supporting globally recognized procedures for insulation test reliability. The document establishes detailed procedures for verifying oven ventilation, temperature uniformity, gradients, fluctuations, and thermal lag time. It also references related ASTM standards and specifications, such as D5423, for acceptable oven performance criteria.

Key Topics

ASTM D5374-22a includes test methods that address the following essential aspects:

• Ventilation Rate: Procedures for calculating air change rate to ensure consistent oven atmosphere during accelerated aging tests.
• Temperature Uniformity: Evaluation of temperature variation, gradient, and fluctuation throughout the oven chamber using multiple thermocouples.
• Thermal Lag Time: Measurement of the time delay for thermal equilibrium when a test specimen is introduced or removed.
• Instrumentation and Apparatus: Requirements for calibrated thermocouples, data loggers, and temperature recording equipment to enable precise monitoring.
• Data Reporting: Instructions for recording test parameters, such as oven identification, temperatures, ventilation rates, and thermal lag results.
• Safety and Compliance: Guidance emphasizing the responsibility of users to address local safety, health, and environmental regulations.

Applications

ASTM D5374-22a is highly relevant across sectors where thermal evaluation of electrical insulation is critical:

• Quality Assurance: Manufacturers of electrical insulating materials and components use these test protocols to qualify production ovens and verify product integrity.
• Research & Development: Material scientists employ these methods to study thermal aging and performance limits of insulation under controlled environments.
• Standards Compliance: Laboratories seeking accreditation or alignment with international best practices incorporate these methods for equipment calibration and process validation.
• Routine Calibration: Ovens in continuous use undergo regular performance checks according to these test methods, ensuring ongoing accuracy and compliance.

Uniform oven performance, as validated through ASTM D5374-22a, is foundational to generating reliable data for insulation life prediction, safety assessments, and product certification.

Related Standards

To facilitate comprehensive thermal endurance testing of electrical insulation, reference these related documents:

• ASTM D5423 - Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation (sets uniformity criteria and acceptable tolerances)
• IEC 60216-4-1 - Guide for the Determination of Thermal Endurance Properties of Electrical Insulating Materials, Part 4: Aging Ovens, Section 1: Single-Chamber Ovens (basis of ASTM D5374-22a’s methods)
• ASTM D1711 - Terminology Relating to Electrical Insulation (glossary of industry terms)
• Withdrawn: ASTM D2436 - Historical reference previously used for forced-convection ovens (replaced by D5374 and D5423)

By following ASTM D5374-22a, organizations ensure their laboratory ovens maintain the required environmental conditions for effective insulation testing, enhancing both product performance and compliance with international quality standards.

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: D5374 − 22a
Standard Test Methods for
Forced-Convection Laboratory Ovens for Evaluation of
Electrical Insulation
This standard is issued under the fixed designation D5374; 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 2.2 Other Document:
IEC Publication 60216-4-1 Guide for the Determination of
1.1 These test methods cover procedures for evaluating the
Thermal Endurance Properties of Electrical Insulating
characteristics of forced-convection ventilated electrically-
Materials, Part 4—Aging Ovens, Section 1—Single-
heated ovens, operating over all or part of the temperature
Chamber Ovens
rangefrom20 °Cabovetheambienttemperatureto500 °Cand
used for thermal endurance evaluation of electrical insulating
3. Terminology
materials.
3.1 Refer to the terminology section of Specification
1.2 ThesetestmethodsarebasedonIECPublication60216-
D5423. For other terms related to electrical and electronic
4-1, and are technically identical to it. This compilation of test
insulating materials issues, refer to Terminology D1711.
methods and an associated specification, D5423, have replaced
Specification D2436.
4. Significance and Use
1.3 This standard does not purport to address all of the
4.1 Ovens used for thermal evaluation of insulating materi-
safety concerns, if any, associated with its use. It is the
als are to be capable of maintaining uniform conditions of
responsibility of the user of this standard to establish appro-
temperature and air circulation over the extended periods of
priate safety, health, and environmental practices and deter-
time that are required for conducting these tests. Specification
mine the applicability of regulatory limitations prior to use.
D5423 specifies the permissible variations from absolute
1.4 This international standard was developed in accor-
uniformity that have been accepted internationally for these
dance with internationally recognized principles on standard-
ovens. These test methods include procedures for measuring
ization established in the Decision on Principles for the
thesevariationsandotherspecifiedcharacteristicsoftheovens.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
5. Apparatus
Barriers to Trade (TBT) Committee.
5.1 Multi-PointRecordingPotentiometer, having provisions
for at least nine iron-constantan or chromel-alumel
2. Referenced Documents
thermocouples, with scale readings to 0.1 °C or less. Use of a
2.1 ASTM Standards:
data processor or a data logger is helpful in reducing the
D1711 Terminology Relating to Electrical Insulation
number of calculations required.
D2436 Specification for Forced-Convection Laboratory Ov-
5.2 Calibrated Iron-Constantan or Chromel-Alumel
ens for Electrical Insulation (Withdrawn 1994)
Thermocouples, using 0.5 mm diameter or smaller wire and
D5423 Specification for Forced-Convection Laboratory Ov-
having a junction size not over 2.5 mm long.
ens for Evaluation of Electrical Insulation
5.2.1 If calibrated thermocouples are not available, use
thermocouples made from a single spool of thermocouple wire
that gives values for temperature that do not differ from each
These test methods are under the jurisdiction of ASTM Committee D09 on
other by more than 0.2 °C when placed within 10 mm of each
Electrical and Electronic Insulating Materials and are the direct responsibility of
Subcommittee D09.17 on Fire and Thermal Properties.
other without touching inside an oven chamber at 200 °C.
Current edition approved Sept. 1, 2022. Published October 2022. Originally
5.3 It is acceptable to use a temperature measuring system
approved in 1993. Last previous edition approved in 2022 as D5374 – 22. DOI:
10.1520/D5374-22A.
other than thermocouples and a potentiometer, provided that
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the sensitivity, accuracy, and response time are equivalent to
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.
3 4
The last approved version of this historical standard is referenced on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
www.astm.org. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5374 − 22a
that of the equipment described above, and that the objectives
P = average power consumption, with no ventilation, ob-
of 6.2.3 relative to minimization of heat conduction effects are
tained by dividing the energy consumption determined
met.
from the watt-hour meter readings by the duration of
the test in hours, W,
5.4 Thermal Lag Time Specimen, consisting of a solid brass
P = average power consumption during ventilation, calcu-
cylinder, 10 mm in diameter and 55 mm long, with one
lated in the same manner, W,
junction of a differential thermocouple soldered to the surface
V = total volume of air circulated within the oven, m (see
midway between the ends. The other junction of the thermo-
Note 1),
couple must be capable of being moved at least 80 mm away 3
ρ = density of the ambient room air during the test, kg/m
from the brass cylinder. An appropriate temperature indicator
(see Note 2), and
(as in 5.1, or other) must be provided for indication of
∆T = difference in temperature between the oven and the
temperature differences to the nearest 0.1 °C as measured by
ambient room temperature, °C.
the differential thermocouple.
NOTE 1—This volume includes space outside the testing chamber. The
amount of this additional space depends on the physical design of the
5.5 Watt-Hour Meter, of the appropriate voltage and phase,
oven.
capable of reading to the nearest 1.0 Wh or less.
NOTE 2—The density of air is dependent on ambient temperature and
pressure; at one atmosphere and 20 °C it is 1.205 kg/m .
6. Procedures
6.1.9 If the rate of ventilation is not within the specified
6.1 Rate of Ventilation: limits for the oven, adjust the vents and dampers and repeat
6.1.7 through 6.1.8.
6.1.1 Summary of Test Method—The rate of ventilation is
6.1.10 Repeat 6.1.2 through 6.1.9, except heat the oven to
calculated using determinations of (1) the average power
required to maintain the oven at a given temperature with its the maximum temperature at which the oven is used.
ports open and (2) the average power required to maintain the 6.1.11 Report the following information:
oven at the same temperature with its ports closed. The test is
6.1.11.1 Identification of the oven,
conducted at 100 °C and at the maximum temperature at which
6.1.11.2 Date and location of test,
the oven is used.
6.1.11.3 Test temperatures, and
6.1.2 Seal all openings into the oven, including, but not
6.1.11.4 Rate of ventilation at each temperature.
necessarily limited to, the vent ports, door, thermometer ports,
6.2 Temperature Variation, Gradient, and Fluctuation:
and the space around the blower shaft (if the blower motor is
6.2.1 Summary of Test Method—Simultaneous temperature
mounted externally).
measurements are made at nine points in the oven chamber
6.1.3 Install a watt-hour meter, as described in 5.5,inthe
overaperiodoftimetodeterminethetimeandspacevariations
oven electrical supply line.
of temperature. The temper
...

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: D5374 − 22 D5374 − 22a
Standard Test Methods for
Forced-Convection Laboratory Ovens for Evaluation of
Electrical Insulation
This standard is issued under the fixed designation D5374; 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 These test methods cover procedures for evaluating the characteristics of forced-convection ventilated electrically-heated
ovens, operating over all or part of the temperature range from 20 °C above the ambient temperature to 500 °C and used for thermal
endurance evaluation of electrical insulating materials.
1.2 These test methods are based on IEC Publication 60216-4-1, and are technically identical to it. This compilation of test
methods and an associated specification, D5423, have replaced Specification D2436.
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.
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.
2. Referenced Documents
2.1 ASTM Standards:
D1711 Terminology Relating to Electrical Insulation
D2436 Specification for Forced-Convection Laboratory Ovens for Electrical Insulation (Withdrawn 1994)
D5423 Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation
2.2 Other Document:
IEC Publication 60216-4-1 Guide for the Determination of Thermal Endurance Properties of Electrical Insulating Materials, Part
4—Aging Ovens, Section 1—Single-Chamber Ovens
3. Terminology
3.1 Refer to the terminology section of Specification D5423. For other terms related to electrical and electronic insulating
materials issues, refer to Terminology D1711.
These test methods are under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and are the direct responsibility of Subcommittee
D09.17 on Fire and Thermal Properties.
Current edition approved Jan. 1, 2022Sept. 1, 2022. Published February 2022October 2022. Originally approved in 1993. Last previous edition approved in 20132022 as
D5374 – 13.D5374 – 22. DOI: 10.1520/D5374-22.10.1520/D5374-22A.
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.
The last approved version of this historical standard is referenced on www.astm.org.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5374 − 22a
4. Significance and Use
4.1 Ovens used for thermal evaluation of insulating materials are to be capable of maintaining uniform conditions of temperature
and air circulation over the extended periods of time that are required for conducting these tests. Specification D5423 specifies the
permissible variations from absolute uniformity that have been accepted internationally for these ovens. These test methods include
procedures for measuring these variations and other specified characteristics of the ovens.
5. Apparatus
5.1 Multi-Point Recording Potentiometer, having provisions for at least nine iron-constantan or chromel-alumel thermocouples,
with scale readings to 0.1 °C or less. Use of a data processor or a data logger is helpful in reducing the number of calculations
required.
5.2 Calibrated Iron-Constantan or Chromel-Alumel Thermocouples, using 0.5-mm0.5 mm diameter or smaller wire and having
a junction size not over 2.5 mm long.
5.2.1 If calibrated thermocouples are not available, use thermocouples made from a single spool of thermocouple wire that gives
values for temperature that do not differ from each other by more than 0.2 °C when placed within 10 mm of each other without
touching inside an oven chamber at 200 °C.
5.3 It is acceptable to use a temperature measuring system other than thermocouples and a potentiometer, provided that the
sensitivity, accuracy, and response time are equivalent to that of the equipment described above, and that the objectives of 6.2.3
relative to minimization of heat conduction effects are met.
5.4 Thermal Lag Time Specimen, consisting of a solid brass cylinder, 10 mm in diameter and 55 mm long, with one junction of
a differential thermocouple soldered to the surface midway between the ends. The other junction of the thermocouple must be
capable of being moved at least 80 mm away from the brass cylinder. An appropriate temperature indicator (as in 5.1, or other)
must be provided for indication of temperature differences to the nearest 0.1 °C as measured by the differential thermocouple.
5.5 Watt-Hour Meter, of the appropriate voltage and phase, capable of reading to the nearest 1.0 Wh or less.
6. Procedures
6.1 Rate of Ventilation:
6.1.1 Summary of Test Method—The rate of ventilation is calculated using determinations of (1) the average power required to
maintain the oven at a given temperature with its ports open and (2) the average power required to maintain the oven at the same
temperature with its ports closed. The test is conducted at 100°C100 °C and at the maximum temperature at which the oven is used.
6.1.2 Seal all openings into the oven, including, but not necessarily limited to, the vent ports, door, thermometer ports, and the
space around the blower shaft (if the blower motor is mounted externally).
6.1.3 Install a watt-hour meter, as described in 5.5, in the oven electrical supply line.
6.1.4 Install a temperature sensor, such as a thermometer, 2 m to 3 m 2 m to 3 m away from the oven, at least 1 m away from
any solid object, and approximately level with the oven air intake. Use the oven temperature indicator to measure the internal
temperature of the oven.
6.1.5 Raise the oven temperature to 100 6 2 °C. When the temperature of the oven has stabilized, measure the consumption of
power over a measured period of 30 to 40 min. Begin and end the measuring period at corresponding points of the cyclic
temperature fluctuation; for example, the moment when the heaters are switched on by the thermostat in the case of an “on/off”
control. Measure and record the room temperature, which must not vary by more than 2 °C during the test.
6.1.6 Remove the seals to restore the oven to its normal operating condition. If necessary, adjust the vents and dampers to positions
estimated to provide the specified rate of ventilation.
D5374 − 22a
6.1.7 Repeat 6.1.5. The average ambient air temperature must be within 2 °C of the average ambient temperature measured in
6.1.5.
6.1.8 Calculate the rate of ventilation in the oven using the following equation:
N 5 3.59 P 2 P / V·ρ·ΔT (1)
~ ! ~ !
2 1
where:
N = number of air changes per hour,
P = average power consumption, with no ventilation, obtained by dividing the energy consumption determined from the
watt-hour meter readings by the durat
...