ASTM D117-22 Standard Guide for Sampling, Test Methods, and Specifications for Electrical Insulating Liquids

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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: D117 − 22

Standard Guide for
Sampling, Test Methods, and Speciﬁcations for Electrical
Insulating Liquids1

This standard is issued under the ﬁxed designation D117; 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 Category Section ASTM Standard
Dielectric Breakdown Voltage 17 D877, D1816, D3300
1.1 This guide describes methods of testing and speciﬁca- Dissipation Factor and Rela- 18 D924
tions for electrical insulating liquids intended for use in
electrical cables, transformers, liquid-ﬁlled circuit breakers, tive Permittivity (Dielectric 19 D7150
and other electrical apparatus where the liquids are used as Constant)
insulating, or heat transfer media, or both. Gassing Characteristic 20 D2300
Under Thermal Stress 21 D1169
1.2 The purpose of this guide is to outline the applicability Gassing Tendency
of the available test methods. Where more than one is available Resistivity 22 D1534
for measuring a given property, their relative advantages are Chemical Tests: 23 D2140
described, along with an indication of laboratory convenience, Acidity, Approximate 24 D3455
precision, (95 % conﬁdence limits), and applicability to spe- Carbon-Type Composition
ciﬁc types of electrical insulating liquids. Compatibility with Construc- 25 D3635
tion Material 26 D7151
1.3 This guide is classiﬁed into the following categories: Copper Content
Sampling Practices, Physical Tests, Electrical Tests, Chemical Elements by Inductively 27 D5837
Tests, and Speciﬁcations. Within each test category, the test Coupled Plasma (ICP-AES)

methods are listed alphabetically by property measured. A list Furanic Compounds in 28 D3612
of standards follows: Electrical Insulating Liquids 29 D831, D1827, D2945
Dissolved Gas Analysis
Category Section ASTM Standard Gas Content of Cable and 30 D664, D974
Sampling: 3 D923 Capacitor Liquids
Physical Tests: Neutralization (Acid and 31 D2668, D4768
4 D611 Base) Numbers 32 D1934, D2112, D2440
Aniline Point Oxidation Inhibitor Content 33 D4059
Coefficient of Thermal Ex- 5 D1903 Oxidation Stability
Polychlorinated Biphenyl 34 D1275
pansion 6 D1500 Content (PCB) 35 D1533
Color Sulfur, Corrosive
Examination: Visual Infrared 7 D1524, D2144, D2129 Water Content 36 D3487
Flash and Fire Point Speciﬁcation:
Interfacial Tension 8 D92 Mineral Insulating Liquid for 37 D5222
Pour Point of Petroleum Electrical Apparatus
9 D971 Less Flammable Electrical 38 D4652
Products Insulating Liquids
Particle Count in Mineral 10 D97, D5949, D5950 Silicone Fluid used for Electrical 39 D6871
Insulation
Insulating Oil 11 D6786 Natural (Vegetable Oil) Ester
Refractive Index and Speciﬁc Fluids used in Electrical
12 D1218 Apparatus
Optical Dispersion
Relative Density (Speciﬁc 13 D287, D1217, D1298, D1481, 1.4 The values stated in SI units are to be regarded as
standard. The values stated in parentheses are provided for
Gravity) D4052 information only.
Speciﬁc Heat
Thermal Conductivity 14 D2766
Viscosity

Electrical Tests: 15 D2717

16 D445, D2161, D7042 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1 This guide is under the jurisdiction of ASTM Committee D27 on Electrical responsibility of the user of this standard to establish appro-
Insulating Liquids and Gases and is the direct responsibility of Subcommittee priate safety, health, and environmental practices and deter-
D27.01 on Mineral. mine the applicability of regulatory limitations prior to use.

Current edition approved May 1, 2022. Published June 2022. Originally 1.6 This international standard was developed in accor-
published as D117 – 21 T. Last previous edition approved in 2018 as D117 – 18. dance with internationally recognized principles on standard-
DOI: 10.1520/D0117-22. ization established in the Decision on Principles for the

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States

1

D117 − 22

Development of International Standards, Guides and Recom- D1534 Test Method for Approximate Acidity in Electrical
mendations issued by the World Trade Organization Technical Insulating Liquids by Color-Indicator Titration
Barriers to Trade (TBT) Committee.
D1816 Test Method for Dielectric Breakdown Voltage of
2. Referenced Documents Insulating Liquids Using VDE Electrodes

2.1 ASTM Standards:2 D1827 Test Method for Gas Content (Nonacidic) of Insulat-
D92 Test Method for Flash and Fire Points by Cleveland ing Liquids by Displacement with Carbon Dioxide (With-
drawn 2009)3
Open Cup Tester
D97 Test Method for Pour Point of Petroleum Products D1903 Practice for Determining the Coefficient of Thermal
D287 Test Method for API Gravity of Crude Petroleum and Expansion of Electrical Insulating Liquids of Petroleum

Origin, and Askarels
Petroleum Products (Hydrometer Method)
D445 Test Method for Kinematic Viscosity of Transparent D1934 Test Method for Oxidative Aging of Electrical Insu-
lating Liquids by Open-Beaker Method
and Opaque Liquids (and Calculation of Dynamic Viscos-
ity) D2112 Test Method for Oxidation Stability of Inhibited
D611 Test Methods for Aniline Point and Mixed Aniline Mineral Insulating Oil by Pressure Vessel
Point of Petroleum Products and Hydrocarbon Solvents
D664 Test Method for Acid Number of Petroleum Products D2129 Test Method for Color of Clear Electrical Insulating
by Potentiometric Titration Liquids (Platinum-Cobalt Scale)
D831 Test Method for Gas Content of Cable and Capacitor
Oils D2140 Practice for Calculating Carbon-Type Composition
D877 Test Method for Dielectric Breakdown Voltage of of Insulating Oils of Petroleum Origin
Insulating Liquids Using Disk Electrodes
D923 Practices for Sampling Electrical Insulating Liquids D2144 Practices for Examination of Electrical Insulating
D924 Test Method for Dissipation Factor (or Power Factor) Oils by Infrared Absorption
and Relative Permittivity (Dielectric Constant) of Electri-
cal Insulating Liquids D2161 Practice for Conversion of Kinematic Viscosity to
D971 Test Method for Interfacial Tension of Insulating Saybolt Universal Viscosity or to Saybolt Furol Viscosity
Liquids Against Water by the Ring Method
D974 Test Method for Acid and Base Number by Color- D2300 Test Method for Gassing of Electrical Insulating
Indicator Titration Liquids Under Electrical Stress and Ionization (Modiﬁed
D1169 Test Method for Speciﬁc Resistance (Resistivity) of Pirelli Method)
Electrical Insulating Liquids
D1217 Test Method for Density and Relative Density (Spe- D2440 Test Method for Oxidation Stability of Mineral
ciﬁc Gravity) of Liquids by Bingham Pycnometer Insulating Oil
D1218 Test Method for Refractive Index and Refractive
Dispersion of Hydrocarbon Liquids D2668 Test Method for 2,6-di-tert-Butyl- p-Cresol and 2,6-
D1250 Guide for the Use of the Joint API and ASTM di-tert-Butyl Phenol in Electrical Insulating Oil by Infra-
Adjunct for Temperature and Pressure Volume Correction red Absorp

Factors for Generalized Crude Oils, Reﬁned Products, and
Lubricating Oils: API MPMS Chapter 11.1 D2717 Test Method for Thermal Conductivity of Liquids
D1275 Test Method for Corrosive Sulfur in Electrical Insu- (Withdrawn 2018)3
lating Liquids
D1298 Test Method for Density, Relative Density, or API D2766 Test Method for Speciﬁc Heat of Liquids and Solids
Gravity of Crude Petroleum and Liquid Petroleum Prod- (Withdrawn 2018)3
ucts by Hydrometer Method
D1481 Test Method for Density and Relative Density (Spe- D2864 Terminology Relating to Electrical Insulating Liq-
ciﬁc Gravity) of Viscous Materials by Lipkin Bicapillary uids and Gases
Pycnometer
D1500 Test Method for ASTM Color of Petroleum Products D2945 Test Method for Gas Content of Insulating Oils
(ASTM Color Scale) (Withdrawn 2012)3
D1524 Test Method for Visual Examination of Used Elec-
trical Insulating Liquids in the Field D3300 Test Method for Dielectric Breakdown Voltage of
D1533 Test Method for Water in Insulating Liquids by Insulating Liquids Under Impulse Conditions
Coulometric Karl Fischer Titration
D3455 Test Methods for Compatibility of Construction Ma-
2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or terial with Electrical Insulating Oil of Petroleum Origin
contact ASTM Customer Service at For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on D3487 Speciﬁcation for Mineral Insulating Oil Used in
the ASTM website. Electrical Apparatus

D3612 Test Method for Analysis of Gases Dissolved in
Electrical Insulating Oil by Gas Chromatography

D3635 Test Method for Dissolved Copper In Electrical
Insulating Oil By Atomic Absorption Spectrophotometry

D4052 Test Method for Density, Relative Density, and API
Gravity of Liquids by Digital Density Meter

D4059 Test Method for Analysis of Polychlorinated Biphe-
nyls in Insulating Liquids by Gas Chromatography

D4652 Speciﬁcation for Silicone Liquid Used for Electrical
Insulation

D4768 Test Method for Analysis of 2,6-Ditertiary-Butyl

3 The last approved version of this historical standard is referenced on
www.astm.org.

2

D117 − 22

Para-Cresol and 2,6-Ditertiary-Butyl Phenol in Insulating placed in a tube and mixed mechanically. The mixture is heated
Liquids by Gas Chromatography at a controlled rate until the two phases become miscible. The
D5185 Test Method for Multielement Determination of mixture is then cooled at a controlled rate, and the temperature
Used and Unused Lubricating Oils and Base Oils by at which the two phases separate is recorded as the aniline
Inductively Coupled Plasma Atomic Emission Spectrom- point.
etry (ICP-AES)
D5222 Speciﬁcation for High Fire-Point Mineral Electrical 4.3 Signiﬁcance and Use—The aniline point of an insulating
Insulating Oils liquid indicates the solvency of the liquid for some materials
D5837 Test Method for Furanic Compounds in Electrical that are in contact with the liquid. A higher aniline point
Insulating Liquids by High-Performance Liquid Chroma- implies a lower aromaticity and a lower degree of solvency for
tography (HPLC) some materials.
D5949 Test Method for Pour Point of Petroleum Products
(Automatic Pressure Pulsing Method) 5. Coefficient of Thermal Expansion
D5950 Test Method for Pour Point of Petroleum Products

(Automatic Tilt Method) 5.1 Scope—Practice D1903 covers the determination of the
D6786 Test Method for Particle Count in Mineral Insulating coefficient of thermal expansion of electrical insulating liquids
Oil Using Automatic Optical Particle Counters of petroleum origin.
D6871 Speciﬁcation for Natural (Vegetable Oil) Ester Fluids
Used in Electrical Apparatus 5.2 Deﬁnition:
D7042 Test Method for Dynamic Viscosity and Density of 5.2.1 coeffıcient of thermal expansion—the change in vol-
Liquids by Stabinger Viscometer (and the Calculation of ume per unit volume per degree change in temperature. It is
Kinematic Viscosity) commonly stated as the average coefficient over a given
D7150 Test Method for the Determination of Gassing Char- temperature range.
acteristics of Insulating Liquids Under Thermal Stress
D7151 Test Method for Determination of Elements in Insu- 5.3 Summary of Practice—The speciﬁc gravity of insulating
lating Oils by Inductively Coupled Plasma Atomic Emis- liquids is determined at two temperatures below 90 °C and
sion Spectrometry (ICP-AES) separated by not less than 5 °C nor more than 14 °C. Test
2.2 ASTM Adjunct:4 methods used may be D287, D1217, D1298, or D1481. The
Adjunct to D1250 Guide for Petroleum Measurement Tables calculation of average coefficient of thermal expansion over
(API MPMS Chapter 11.1) this temperature range is given in Practice D1903.

SAMPLING 5.4 Signiﬁcance and Use—A knowledge of the coefficient of
expansion of a liquid is essential to compute the required size
3. Sampling of a container to accommodate a volume of liquid over the full
temperature range to which it will be subjected. It is also used
3.1 Accurate sampling, whether of the complete contents or to compute the volume of void space that would exist in an
only parts thereof, is extremely important from the standpoint inelastic device ﬁlled with the liquid after the liquid has cooled
of evaluation of the quality of the product sampled. Obviously, to a lower temperature.
careless sampling procedure or contamination in the sampling
equipment will result in a sample that is not truly representa- 6. Color
tive. This generally leads to erroneous conclusions concerning
quality and incurs loss of the time, effort, and expense involved 6.1 Scope—Test Method D1500 covers the visual determi-
in securing, transporting, and testing the sample. nation of color of a wide variety of liquid petroleum products,
including mineral insulating liquids.

3.2 Sample the insulating liquid in accordance with Prac-
tices D923 as appropriate. 6.2 Summary of Test Method:
6.2.1 Test Method D1500—The test specimen is placed in a
PHYSICAL PROPERTIES glass sample jar (an ordinary 125-mL test specimen bottle is
satisfactory for routine tests). The color of the sample by
4. Aniline Point transmitted light is compared with a series of tinted glass
standards. The glass standard matching the sample is selected,
4.1 Scope—Test Method D611 covers the determination of or if an exact match is not possible, the next darker glass is
the aniline point of petroleum products, provided that the selected. The results are reported numerically on a scale of 0.5
aniline point is below the bubble point and above the solidiﬁ- to 8.0.
cation point of the aniline-sample mixture.
6.3 Signiﬁcance—A low color number is an essential re-
4.2 Summary of Test Method: quirement for inspection of assembled apparatus in a tank. An
4.2.1 Test Method D611—Equal volumes of aniline and test increase in the color number during service is an indicator of
specimen or aniline and test specimen plus n-heptane are deterioration or contamination of the insulating liquid.

4 Available from ASTM International Headquarters. Order Adjunct No. ADJ- 7. Examination: Visual/Infrared
ADJD1250. Original adjunct produced in 1983.
7.1 Scope:
7.1.1 Both visual examination and qualitative infrared ab-
sorption are described in this section. The test methods are:

3

D117 − 22

7.1.2 Test Method D1524—This is a visual examination of (9 °F ⁄min to 11 °F ⁄min) and apply the test ﬂame every 2 °C (or
mineral insulating liquids that have been used in transformers, 5 °F) until a ﬂash occurs. Continue heating and testing every
liquid-ﬁlled circuit breakers, or other electrical apparatus as 2 °C (or 5 °F) until the liquid continues to burn for at least 5 s.
insulating or cooling media, or both. The procedure is described in Test Method D92.

7.1.3 Practices D2144—The infrared absorption from 2.5 to 8.4 Signiﬁcance and Use—The ﬂash point and ﬁre point
25 µm (4000 to 400 cm−1) is recorded as a means of (a) tests give an indication of the ﬂammability of a liquid. They
establishing continuity by comparison with the spectra of may also be used to provide a qualitative indication of
previous shipments by the same supplier, (b) for the detection contamination with more ﬂammable materials. In the latter
of some types of contaminants, (c) for the identiﬁcation of context, the ﬂash point test is more sensitive.
liquids in storage or service. This practice is not intended for
the determination of the various constituents of a liquid. 9. Interfacial Tension

7.2 Summary of Test Methods: 9.1 Scope—These test methods cover the measurement,
7.2.1 Test Method D1524—The condition of the test speci- under nonequilibrium conditions, of the interfacial tension of
men is estimated by observation of cloudiness, foreign insulating liquids against water. These test methods have been
particles, or suspended matter in the sample by reﬂected light. shown by experience to give a reliable indication of the
By use of this test method and Test Methods D1500 or D2129, presence of hydrophilic compounds.
the color and condition of a test specimen of electrical
insulating liquid may be estimated during a ﬁeld inspection, 9.2 Deﬁnition:
thus assisting in the decision as to whether or not the sample 9.2.1 interfacial tension—the molecular attractive force be-
should be sent to a central laboratory for full evaluation. tween unlike molecules at an interface. It is usually expressed
7.2.2 Practices D2144—The infrared spectrum is recorded in millinewtons per meter.
from 2.5 to 25 µm (4000 to 400 cm−1) either as the absorption
spectrum itself, or as the differential between the test specimen 9.3 Summary of Test Methods:
and reference liquid. The spectra are compared with reference 9.3.1 Test Method D971—Interfacial tension is determined
spectra to establish the identity of the liquid. by measuring the force necessary to detach a platinum wire
upward from the oil water interface. To calculate the interfacial
7.3 Signiﬁcance and Use: tension, the force so measured is corrected by an empirically
7.3.1 Practices D2144—The infrared spectrum of an elec- determined factor which depends upon the force applied, the
trical insulating liquid indicates the general chemical compo- densities of both oil and water, and the dimensions of the ring.
sition of the sample. Because of the complex mixture of The measurement is completed within 1 min of the formation
compounds present in insulating liquids, the spectrum is not of the interface.
sharply deﬁned and may not be suitable for quantitative

estimation of components. The identity of the liquid can be 9.4 Signiﬁcance and Use—Interfacial tension measurements
quickly established as being the same or different from on electrical insulating liquids provide a sensitive means of
previous samples by comparison with the reference spectra. detecting small amounts of soluble polar contaminants and
products of oxidation. A high value for new mineral insulating
8. Flash and Fire Point liquid indicates the absence of most undesirable polar contami-
nants. The test is frequently applied to service-aged liquids as
8.1 Scope: an indication of the degree of deterioration.
8.1.1 Test Method D92 covers the determination of ﬂash
and ﬁre points of all petroleum products except fuel oil and 10. Pour Point of Petroleum Products
those having an open cup ﬂash below 79 °C (175 °F).
8.1.2 This test method should be used solely to measure and 10.1 Scope—The pour point is applicable to any petroleum
describe the properties of materials in response to heat and liquid.
ﬂame under controlled laboratory conditions and should not be
used for the description, appraisal, or regulation of the ﬁre 10.2 Deﬁnition:
hazard of materials under actual ﬁre conditions. 10.2.1 pour point—the lowest temperature, expressed as a
multiple of 3 °C at which the liquid is observed to ﬂow when
8.2 Deﬁnitions: cooled and examined under prescribed conditions.
8.2.1 ﬂash point—the temperature at which vapors above
the liquid surface ﬁrst ignite when a small test ﬂame is passed 10.3 Summary of Test Methods:
across the surface under speciﬁed conditions. 10.3.1 After preliminary heating, the test specimen is
8.2.2 ﬁre point—the temperature at which liquid ﬁrst ignites cooled at a speciﬁed rate and examined at intervals of 3 °C for
and burns for at least 5 s when a small test ﬂame is passed ﬂow characteristics. The lowest temperature at which move-
across the surface under speciﬁed conditions. ment of the liquid is observed within 5 s is reported as the pour
point. The procedure is described in Test Method D97.
8.3 Summary of Test Method—Fill the test cup to the 10.3.2 Test Method D5949 covers the determination of pour
speciﬁed level with the test specimen. Heat the sample initially point of petroleum products by an automatic instrument that
at 14 °C ⁄min to 17 °C ⁄min (25 °F ⁄min to 30 °F ⁄min) until the applies a controlled burst of nitrogen gas onto the specimen
temperature is 56 °C (100 °F) below the expected ﬂash point. surface while the specimen is being cooled and detects
Reduce the rate of temperature change to 5 °C ⁄min to 6 °C ⁄min movement of the surface of the test specimen with an optical
eye.

4

D117 − 22

10.3.3 Test method D5950 covers the determination of pour 12.1.1 Test Method D1218—Describes a precise method for
point of petroleum products by an automatic instrument that determining refractive index accurate to 0.00006 and refractive
tilts the test jar during cooling and detects movement of the dispersion accurate to 0.00012. The liquid must be transparent,
surface of the test specimen with an optical eye. no darker than ASTM 4.0 color (see Test Method D1500) and
have a refractive index between 1.33 and 1.50. The speciﬁc
10.4 Signiﬁcance and Use: optical dispersion is calculated by dividing the refractive
10.4.1 The pour point of an insulating liquid gives an dispersion value by the speciﬁc gravity of the liquid.
indication of the temperature below which it may not be
possible to pour or remove the liquid from its container. 12.2 Deﬁnitions:
10.4.2 In connection with liquid for use in cable systems, 12.2.1 refractive index—the ratio of the velocity of light in
the pour point may be useful to indicate the point at which no air to its velocity in the substance under test.
free movement will take place in the cable or to indicate the 12.2.2 speciﬁc optical dispersion —the difference between
temperature at which partial separation of wax may occur. the refractive indexes of light of two different wave lengths,
10.4.3 The pour point of an electrical insulating liquid is both indexes measured at the same temperature, the difference
important as an index of the lowest temperature to which the being divided by the speciﬁc gravity also measured at the test
material may be cooled without seriously limiting the degree of temperature. For convenience, the speciﬁc dispersion value is
circulation of the liquid. Some materials are sensitive to multiplied by 104.
temperature cycling or prolonged storage at low temperatures,
and their pour points may not adequately predict their low 12.3 Summary of Test Method:
temperature ﬂow properties. 12.3.1 The two methods differ in the accuracy of the
refractometer used. After adjusting the instrument temperature
11. Particle Count in Mineral Insulating Oil Using to 25°C, apply the test specimen to the refracting prism, read
Automatic Optical Particle Counters the refractive index, and read the compensator dial reading.
From the correlation tables supplied with the instrument obtain
11.1 Scope—Test Method D6786 covers the determination the refractive dispersion. Calculate the speciﬁc optical disper-

of particle concentration and particle size distribution in sion by dividing refractive dispersion by the speciﬁc gravity of
mineral insulating liquid. It is suitable for testing liquids the liquid.
having a viscosity of 6 to 20 mm2/s at 40 °C. The test method
is speciﬁc to liquid automatic particle analyzers that use the 12.4 Signiﬁcance and Use:
light extinction principle. 12.4.1 Refractive Index of an insulating liquid varies with
its composition and with the nature and amount of contami-
11.2 Summary of Test Method: nants held in solution. Where the refractive index of an
11.2.1 Samples are taken in particle-clean bottles that are insulating liquid when new is known, determinations made on
suitable for particle analysis. The sample bottle is agitated to the same liquid after periods of service may form a basis for
redistribute particles in the liquid, then the liquid is placed in estimating any change in composition or the degree of con-
an automatic particle counter, where the number of particles tamination acquired through service.
and their size distribution are determined by the light extinction 12.4.2 Speciﬁc Optical Dispersion serves as a quick index
principle. to the amount of unsaturated compounds present in a liquid. As
11.2.2 As particles pass through the sensing zone of the the dispersion values for paraffinic and naphthenic compounds
instrument, the quantity of light reaching the detector is are nearly the same and are essentially independent of molecu-
obscured. This signal is translated to an equivalent projected lar weight and structural differences, values above a minimum
area diameter based on calibration with a NIST-traceable liquid of about 97 bear a direct relationship to the amount of aromatic
(ISO Medium Test Dust suspension). compounds present in insulating liquid.

11.3 Signiﬁcance and Use: 13. Relative Density (Speciﬁc Gravity)
11.3.1 Particles in insulating liquid can have a detrimental
effect on the dielectric properties of the liquid, depending on 13.1 Scope:
the size, concentration, and nature of the particles. The source 13.1.1 The methods used to measure relative density (spe-
of these particles can be external contaminants, liquid degra- ciﬁc gravity) may use a hydrometer, pycnometer, or an
dation byproducts, or internal materials such as metals, carbon, oscillating tube.
or cellulose ﬁbers. 13.1.1.1 Test Method D287—Uses an API hydrometer and is
11.3.2 Particle counts provide a general degree of contami- limited to liquids having a Reid vapor pressure of 180 kPa (26
nation level and may be useful in assessing the condition of psi) or less.
speciﬁc types of electrical equipment. Particle counts can also 13.1.1.2 Test Method D1217—Covers the use of a pycnom-
be used to determine ﬁltering effectiveness when processing eter to measure the relative density (speciﬁc gravity) of

liquid. petroleum fractions.
11.3.3 If more speciﬁc knowledge of the nature of the 13.1.1.3 Test Method D1298—Covers the use of a hydrom-
particles is needed, other tests such as metals analysis or ﬁber eter to measure relative density (speciﬁc gravity) directly or the
identiﬁcation and counting must be performed. measurement of API gravity followed by conversion to relative
density (speciﬁc gravity). This test method is limited to liquids
12. Refractive Index and Speciﬁc Optical Dispersion having a Reid vapor pressure of 179 kPa (26 psi) or less. This

12.1 Scope:

5

D117 − 22

test method is most suitable for use with mobile transparent neous single body of liquid. Such conditions have caused
liquids, although it can also be used with viscous liquids if serious overheating of self-cooled apparatus. Suitable precau-
sufficient care is taken in the measurement. tions should be taken to ensure mixing.

13.1.1.4 Test Method D1481—Covers the determination of 14. Speciﬁc Heat
the densities of liquids more viscous than 15 mm2/s at 20 °C.
The liquid should not have a vapor pressure greater than 13 kPa 14.1 Scope—Test Method D2766 covers determination of
(100 mm Hg) at the test temperature. To measure the density of the speciﬁc heat of electrical insulating liquids of petroleum
less viscous liquids more accurately than permitted by the origin.
hydrometer method, Test Method D1217 is available.
14.2 Deﬁnition:
13.1.1.5 Test Method D4052—Covers the measurement of 14.2.1 speciﬁc heat (or heat capacity) of a substance—a
relative density (speciﬁc gravity) by the measurement of thermodynamic property that is a measure of the amount of
change in oscillation frequency of a vibrating glass tube ﬁlled energy required to produce a given temperature change within
with test liquid. a unit quantity of that substance. The standard unit of heat
capacity is J/(kg·°C) at some deﬁned temperature.
13.2 Deﬁnition:

13.2.1 relative density (speciﬁc gravity)—the ratio of the 14.3 Summary of Test Method—The speciﬁc heat is deter-
mass (weighed in vacuum) of a given volume of liquid at 15 °C mined by Test Method D2766. The measurement is made by
(60 °F) to the mass of an equal volume of pure water at the heating a test specimen at a known and ﬁxed rate. Once
same temperature. When reporting results, explicitly state the dynamic heating equilibrium is obtained, the heat ﬂow is
reference temperature, for example, speciﬁc gravity 15/15 °C. recorded as a function of temperature. The heat ﬂow normal-
ized to specimen mass and heating rate is directly proportional
13.3 Summary of Test Method: to the specimen’s speciﬁc heat capacity.
13.3.1 API gravity may be measured at the liquid tempera-
ture using a hydrometer (Test Methods D287 or D1298) or 14.4 Signiﬁcance and Use—A knowledge of the speciﬁc
Digital Density Meter (Test Method D4052) and converting to heat is helpful in designing adequate heat transfer properties
15 °C or 60 °F using adjunct to Guide D1250.4 for electrical apparatus. A higher speciﬁc heat value indicates a
13.3.2 Relative density (speciﬁc gravity) may be measured more efficient heat transfer medium.
at the liquid temperature using a hydrometer (Test Method
D1298) or by Digital Density Meter (Test Method D4052) and 15. Thermal Conductivity
converted to 15 °C or 60 °F using adjunct to Guide D1250.4
13.3.3 Test Method D1481—The liquid is drawn into the 15.1 Scope—Test Method D2717 covers the determination
bicapillary pycnometer through the removable siphon arm and of the thermal conductivity of electrical insulating liquids of
adjusted to volume at the temperature of test. After equilibra- petroleum origin.
tion at the test temperature, liquid levels are read; and the
pycnometer is removed from the thermostated bath, cooled to 15.2 Deﬁnition:
room temperature, and weighed. Density or relative density 15.2.1 thermal conductivity—the ability of a substance to
(speciﬁc gravity), as desired, is then calculated from the transfer energy as heat in the absence of mass transport
volume at the test temperature, and the weight of the sample. phenomena. The standard unit of thermal conductivity is as
The effect of air buoyancy is included in the calculation. follows:

13.4 Signiﬁcance and Use: W/ ~m·°C!
13.4.1 Electrical insulating liquids are usually sold on the
basis of volume delivered at 15 °C (60 °F). Delivery is often 15.3 Summary of Test Method—The thermal conductivity is
made on the basis of net weight of product in drums, and the determined by Test Method D2717. This test method measures
speciﬁc gravities often are measured at temperatures other than the temperature gradient produced across the liquid by a known

15 °C. The values of relative density (speciﬁc gravity) at 15 °C amount of energy introduced into the test cell by an electrically
must be known to calculate the volume at 15 °C of the liquid heated platinum element.
delivered.
13.4.2 The relative density (speciﬁc gravity) of a mineral 15.4 Signiﬁcance and Use—A knowledge of thermal con-
insulating liquid inﬂuences the heat transfer rates and may be ductivity is helpful in designing adequate heat transfer prop-
pertinent in determining suitability for use in speciﬁc applica- erties for electrical apparatus. A high value indicates a good
tions. In certain cold climates, ice may form in de-energized heat transfer efficiency property for the liquid.
electrical equipment exposed to temperatures below 0 °C, and
the maximum speciﬁc gravity of the liquid used in such 16. Viscosity
equipment should be at a value that will ensure that ice will not
ﬂoat in the liquid at any temperature the liquid might attain. 16.1 Scope:
13.4.3 When making additions of insulating liquid to appa- 16.1.1 Test Method D445—This test method speciﬁes a
ratus in service, a difference in relative density (speciﬁc procedure for the determination of the kinematic viscosity of
gravity) may indicate a tendency of the two bodies of liquid to liquid petroleum products, both transparent and opaque, by
remain in separate layers rather than mixing into a homoge- measuring the time for a volume of liquid to ﬂow under gravity
through a calibrated glass capillary viscometer. The dynamic
viscosity can be obtained by multiplying the kinematic viscos-
ity by the density of the liquid.

6

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16.1.2 Practice D2161—Provides tables or equations for the 17.1.3 Test Method D1816—This test method covers the
conversion of centistokes into Saybolt Universal Seconds or determination of the dielectric breakdown voltage of insulating
Saybolt Furol Seconds at the same temperatures. liquids (liquids of petroleum origin, silicone liquids, high
ﬁre-point mineral electrical insulating liquids, synthetic ester
16.2 Summary of Test Methods: liquids and natural ester liquids). This test method is applicable
16.2.1 Test Method D445—The time is measured in seconds to insulating liquids commonly used in cables, transformers,
for a ﬁxed volume of liquid to ﬂow under gravity through the liquid-ﬁlled circuit breakers, and similar apparatus as an

capillary of a calibrated viscometer under a reproducible insulating and cooling medium. Refer to Terminology D2864
driving head and at a closely controlled temperature. The for deﬁnitions used in this test method.
kinematic viscosity is the product of the measured ﬂow time
and the calibration constant of the viscometer. 17.1.4 Test Method D3300—Applicable to any liquid com-
16.2.2 Practice D2161—The Saybolt Universal viscosity monly used as an insulating and cooling medium in high-
equivalent to a given kinematic viscosity varies with the voltage apparatus subjected to impulse conditions, such as
temperature at which the determination is made. The basic transient voltage stresses arising from such causes as nearby
conversion values are given in Table 1 of this practice for lightning strikes and high-voltage switching operations.
37.8 °C (100 °F). Factors are given for converting units at
other temperatures. The Saybolt Furol viscosity equivalents are 17.2 Deﬁnition:
given in Table 3 of this practice for 50.0 °C and 98.9 °C 17.2.1 dielectric breakdown voltage—the potential differ-
(122 °F and 210 °F) only. ence at which electrical failure occurs in an electrical insulating
16.2.3 Test Method D7042—This test method covers and material or insulation structure, under prescribed test condi-
speciﬁes a procedure for the concurrent measurement of both tions.
the dynamic viscosity, η, and the density, ρ, of liquid petroleum
products and crude oils, both transparent and opaque. The 17.3 Summary of Test Methods:
kinematic viscosity, ν, can be obtained by dividing the dynamic 17.3.1 Test Method D877—The insulating liquid is tested in
viscosity, η, by the density, ρ, obtained at the same test a test cup between two 25.4-mm (1-in.) diameter disk elec-
temperature. trodes spaced 2.54 mm (0.100 in.) apart. A 60-Hz voltage is
applied between the electrodes and raised from zero at a
16.3 Signiﬁcance and Use: uniform rate of 3 kV/s. The dielectric breakdown voltage is
16.3.1 The fundamental and preferred method for measur- recorded, prior to the occurrence of disruptive discharge, when
ing kinematic viscosity is by use of Test Method D445. the voltage across the specimen has dropped to less than 100 V.
16.3.2 Viscosity of electrical insulating liquids inﬂuences In the referee procedure, one breakdown test is made on each
their heat transfer properties, and consequently the temperature of ﬁve ﬁllings of the test cup, and the average and individual
rise of energized electrical apparatus containing the liquid. At values of breakdown voltage are reported.
low temperatures, the resulting higher viscosity inﬂuences the 17.3.2 Test Method D1816—The liquid is tested in a test cell
speed of moving parts, such as those in power circuit breakers, between spherically capped (VDE) electrodes spaced either 1
switchgear, load tapchanger mechanisms, pumps, and regula- mm (0.040 in.) or 2 mm (0.080 in.) apart. The liquid is stirred
tors. Viscosity controls insulating liquid processing conditions, before and during application of voltage by means of a

such as dehydration, degassiﬁcation and ﬁltration, and liquid motor-driven stirrer. A 60-Hz voltage is applied between the
impregnation rates. High viscosity may adversely affect the electrodes and raised from zero at a uniform rate of 0.5 kV/s.
starting up of apparatus in cold climates (for example, spare The voltage at which the current produced by breakdown of the
transformers and replacements). Viscosity affects pressure liquid reaches the range of 2 to 20 mA, tripping a circuit
drop, liquid ﬂow, and cooling rates in circulating liquid breaker, is considered to be the dielectric breakdown voltage.
systems, such as in pipe-type cables and transformers. In the procedure, ﬁve breakdown tests are made on one ﬁlling
of the test cell. If the ﬁve breakdowns fall within the statistical
ELECTRICAL PROPERTIES requirements, the average value is reported. If not, ﬁve
additional breakdowns are required with the average of the ten
17. Dielectric Breakdown Voltage values reported.
17.3.3 Test Method D3300—The electrode system consists
17.1 Scope: of either: (1) two 12.7-mm (0.5-in.) diameter spheres spaced
17.1.1 There are two standard test methods for determining 3.8 mm (0.15 in.) apart or (2) a 12.7-mm (0.5-in.) diameter
the dielectric breakdown voltage of electrical insulating liquids sphere and a steel phonograph needle of 0.06-mm radius of
at commercial power frequencies, D877 and D1816, and one curvature of point, spaced 25.4 mm (1.0 in.) apart. The polarity
standard test method for determining the dielectric breakdown of the needle with respect to the sphere can be either positive
voltage of insulating liquids under impulse conditions, D3300. or negative. The electrodes are immersed in the liquid in a test
17.1.2 Test Method D877—Applicable to petroleum liquids, cell. An impulse wave of 1.2 by 50 µs wave shape (times to
hydrocarbons, and askarels commonly used as insulating and reach crest value and to decay to half of crest value, respec-
cooling media in cables, transformers, liquid-ﬁlled circuit tively) is applied at progressively higher voltages until break-
breakers, and similar apparatus. The suitability of Test Method down occurs.
D877 for testing liquids having viscosities exceeding 900
mm2/s at 40 °C (104 °F) has not been determined. 17.4 Signiﬁcance and Use:
17.4.1 Power Frequencies (Test Methods D877 and
D1816)—The dielectric breakdown voltage of an insulating

7

D117 − 22

liquid at commercial power frequencies is of importance as a 18.1.1 Test Method D924 covers new electrical insulating
measure of the liquid’s ability to withstand electric stress. It is liquids as well as liquids in service or subsequent to service in
the voltage at which breakdown occurs between two electrodes cables, transformers, liquid-ﬁlled circuit breakers, and other
under prescribed test conditions. It also serves to indicate the electrical apparatus.
presence of contaminating agents, such as water, dirt, moist
cellulosic ﬁbers, or conducting particles in the liquid, one or 18.1.2 This test method provides a procedure for making
more of which may be present when low dielectric breakdown referee and routine tests at a commercial frequency of approxi-
values are found by test. However, a high dielectric breakdown mately 60 Hz.
voltage does not indicate the absence of all contaminants. See
Appendix X1 of either test method for other inﬂuences that 18.2 Summary of Test Method:
affect the dielectric breakdown voltage of a liquid. 18.2.1 The loss characteristic is commonly measured in
terms of dissipation factor (tangent of the loss angle) or of
17.4.1.1 The ability of an insulating liquid to resist break- power factor (sine of the loss angle). For values up to 0.05,
down under the test conditions is an indication of the ability of dissipation factor and power factor values are equal to each
the insulating liquid to perform its insulating function in other within about one part in one thousand and the two terms
electrical apparatus. The average breakdown voltage is com- may be considered interchangeable.
monly used in speciﬁcations for the qualiﬁcation and accep- 18.2.2 Test Method D924—The liquid test specimens are
tance of insulating liquids. It is also used as a control test for tested in a three-terminal or guarded electrode test cell main-
the reﬁning of new or reclaiming of used insulating liquids. tained at the desired test temperature. Using a bridge circuit,
Because of the complex interactions of the factors affecting measure the loss characteristics and capacitance following the
dielectric breakdown voltage the values obtained cannot be instructions appropriate to the bridge being used. For routine
used for design purposes. tests, a two-electrode cell may be used.

17.4.1.2 The square-edged disk electrodes of Test Method 18.3 Signiﬁcance and Use:
D877 are relatively insensitive to dissolved water in concen- 18.3.1 Dissipation Factor (or Power Factor)—This prop-
trations below 60 % of the saturation level. This method is erty is a measure of the dielectric losses in a liquid, and hence,
recommended for acceptance tests on unprocessed insulating of the amount of energy dissipated as heat. A low value of
liquids received from vendors in tank cars, tank trucks, and dissipation factor (or power factor) indicates low dielectric
drums. It also may be used for the routine testing of liquids losses and a low level of soluble polar ionic or colloidal
from selected power systems apparatus. contaminants. This characteristic may be useful as a means of

quality control and as an indication of liquid changes in service
17.4.1.3 The more uniform electric ﬁeld associated with resulting from contamination and liquid deterioration.
VDE electrodes employed in Test Method D1816 is more 18.3.2 Relative Permittivity (Dielectric Constant)—
sensitive to the deleterious effects of moisture in solution, Insulating liquids are used in general either to insulate com-
especially when cellulosic ﬁbers are present in the liquid, than ponents of an electrical network from each other and from
is the ﬁeld in Test Method D877. Test Method D1816 can be ground, alone or in combination with solid insulating materials,
used for processed or as received liquids. Filtering and dehy- or to function as the dielectric of a capacitor. For the ﬁrst use,
drating the liquid may increase Test Method D1816 dielectric a low value of relative permittivity is often desirable in order
breakdown voltages substantially. to have the capacitance be as small as possible, consistent with
acceptable chemical and heat transfer properties. However, an
17.4.2 Impulse Conditions (Test Method D3300): intermediate value of relative permittivity may sometimes be
17.4.2.1 This test method is most commonly performed advantageous in achieving a better voltage distribution be-
using a negative polarity point opposing a grounded sphere tween the liquid and solid insulating materials with which the
(NPS). The NPS breakdown voltage of fresh unused liquids liquid may be in series. When used as the dielectric in a
measured in the highly divergent ﬁeld in this conﬁguration capacitor, it is desirable to have a higher value of relative
depends on liquid composition; decreasing with increasing permittivity so the physical size of the capacitor may be as
concentration of aromatic, particularly polyaromatic, hydrocar- small as possible.
bon molecules.
17.4.2.2 This test method may be used to evaluate the 19. Gassing Characteristics of Insulating Liquids Under
continuity of composition of a liquid from shipment to ship- Thermal Stress at Low Temperature
ment. The NPS impulse breakdown voltage of a liquid can also
be substantially lowered by contact with materials of 19.1 Scope:
construction, by service aging, and by other impurities. Test 19.1.1 Test Method D7150 describes the procedures to
results lower than those expected for a given fresh liquid may determine the low temperature (120°C) gassing characteristics
also indicate use or contamination of that liquid. of insulating liquids speciﬁcally and without the inﬂuence of
17.4.2.3 Although polarity of the voltage wave has little or other electrical apparatus materials or electrical stresses. This
no effect on the breakdown strength of an liquid in uniform test method was primarily designed for insulating mineral
ﬁelds, polarity does have a marked effect on the breakdown liquid. It can be applied to other insulating liquids in which
voltage of an liquid in nonuniform electric ﬁelds. dissolved gas-in-liquid analysis (Test Method D3612) is com-
monly performed.

18. Dissipation Factor and Relative Permittivity 19.1.2 This test method is particularly suited for detection
(Dielectric Constant) of the phenomenon sometimes known as “stray gassing” and is

18.1 Scope:

8

D117 − 22

also referred to in CIGRE TF11 B39. 1.3 This test method is one that is sealed from the outside atmosphere. Liquids sparged
performed on electrical insulating liquids to determine the with air generally produce much more hydrogen as a percent-
propensity of the liquid to produce certain gases such as age of the total combustible gas content as compared to liquids
hydrogen and hydrocarbons at low temperatures. sparged with nitrogen as these produce more hydrocarbons in
relation to hydrogen.
19.1.3 This test method details two procedures:
19.1.3.1 Method A describes the procedure for determining 20. Gassing Tendency
the gassing characteristics of a new, unused insulating liquid,
as received, at 120 °C for 164 h. 20.1 Scope—Test Method D2300 describes a procedure to
19.1.3.2 Method B describes the procedure for processing measure the rate at which gas is evolved or absorbed by
the insulating liquid through an attapulgite clay column to insulating liquids when subjected to electrical stress of suffi-
remove organic contaminants and other reactive groups that cient intensity to cause ionization. The liquid test specimen is
may inﬂuence the gassing behavior of an insulating liquid, initially saturated with a selected gas (usually hydrogen) at
which is suspected of being contaminated. This procedure atmospheric pressure.
applies to both new and used insulating liquids.
20.2 Summary of Test Method:
19.2 Summary of Test Method: 20.2.1 Test Method D2300—After being saturated with a
19.2.1 Method A—Insulating liquid is ﬁltered through a gas (usually hydrogen) the liquid is subjected to a radial
mixed cellulose ester ﬁlter. A portion of the test specimen is electrical stress at a controlled temperature. The gas space
sparged for 30 min with dry air. A test specimen is then placed above the liquid is ionized due to the electrical stresses; and
into a glass syringe, capped and aged at 120 °C 6 2 °C for 164 therefore, the liquid surface at the liquid-gas interface is

h. The test is run in duplicate. The other portion of the test subjected to ion bombardment. The evolution or absorption of
specimen is sparged for 30 min with dry nitrogen. A test gas is measured with a gas burette and reported in µL/min.
specimen is then placed into a glass syringe, capped and aged
at 120 °C 6 2 °C for 164 h. The test is run in duplicate. After, 20.3 Signiﬁcance and Use—This test method indicates
the test specimens have cooled, dissolved gas-in-liquid analy- whether insulating liquids are gas absorbing or gas evolving
sis is then performed according to Test Method D3612. under the test conditions. Numerical results obtained in differ-
19.2.2 Method B—Insulating liquid is passed through a ent laboratories may differ signiﬁcantly in magnitude, and the
heated (60 °C to 70 °C) attapulgite clay column at a rate of 3 results of this test method should be considered as qualitative
mL to 5 mL per minute. The insulating liquid is contacted with in nature.
the attapulgite clay at a ratio of 1 g clay to 33 mL (range: 30
mL to 35 mL) of insulating liquid (0.25 lb clay: 1 gal of 20.3.1 For certain applications when insulating liquid is
insulating liquid). The insulating liquid is collected and sub- stressed at high voltage gradients, it is desirable to be able to
jected to the testing as outlined in 19.2.1. determine the rate of gas evolution or gas absorption under
speciﬁed test conditions. At the present time, correlation of
19.3 Signiﬁcance and Use: such test results with equipment performance is limited.
19.3.1 Generation of combustible gases is used to determine
the condition of liquid-ﬁlled electrical apparatus. Many years 21. Resistivity
of empirical evidence has yielded guidelines such as those
given in IEEE C 57.104, IEC 60599 and IEC 61464. Industry 21.1 Scope:
experience has shown that electric and thermal faulted in 21.1.1 Test Method D1169 covers the determination of
liquid-ﬁlled electrical apparatus are the usual sources that speciﬁc resistance (resistivity) applied to new electrical insu-
generate gases. Experience has shown that some of the gases lating liquids, as well as to liquids in service, or subsequent to
could form in the liquid at low temperatures or as a result of service, in cables, transformers, liquid-ﬁlled circuit breakers,
contamination, without any other inﬂuences. and other electrical apparatus.
19.3.2 Some severely hydro-treated electrical equipment 21.1.2 This test method covers a procedure for making
insulating liquids subjected to thermal stress and liquids that referee and routine tests with dc potential.
contain certain types of contamination may produce speciﬁc
gases at lower temperatures than normally expected for their 21.2 Deﬁnition:
generation and hence, falsely indicate abnormal operation of 21.2.1 speciﬁc resistance (resistivity)—of a liquid, the ratio
the electrical apparatus. Some new liquids have produced large of the dc potential gradient in volts per centimeter paralleling

amounts of gases, especially hydrogen, without the inﬂuence of the current ﬂow within the test specimen, to the current density
other electrical apparatus materials or electrical stresses. This in amperes per square centimeter at a given instant of time and
renders interpretation of the dissolved gas analysis more under prescribed conditions. This is numerically equal to the
complicated. resistance between opposite faces of a centimeter cube of a
19.3.3 Heating for 164 h has been found to be a sufficient liquid. It is measured in ohm centimeters.
amount of time to reach a stable and characteristic gassing
pattern. 21.3 Summary of Test Method:
19.3.4 This method uses both dry air and dry nitrogen as the 21.3.1 Test Method D1169—The liquid test specimen is
sparging gas. This is to reﬂect either a electrical apparatus tested in three-terminal, or guarded-electrode test cell main-
preservation system that allows oxygen to contact the liquid or tained at the desired test temperature. A dc voltage is applied of
such magnitude that the electric stress in the liquid is between
200 and 1200 V/mm. The current ﬂowing between the high-
voltage and guarded measuring electrode is measured at the

9

D117 − 22

end of 1 min of electriﬁcation and the resistivity calculated intercept are calculated. Using these two computed values,
using speciﬁed equations appropriate to the method of mea- percentage of aromatic carbons, naphthenic carbons, and
surement used. A two-electrode cell may be used for routine paraffinic carbons are estimated from a correlation chart.
tests.
23.3 Signiﬁcance and Use—The primary purpose of this
21.4 Signiﬁcance and Use—The resistivity of a liquid is a practice is to characterize the carbon-type composition of a
measure of its electrical insulating properties under conditions liquid. It is also applicable in observing the effect on liquid
comparable to those of the test. High resistivity reﬂects low constitution of various reﬁning processes, such as solvent
content of free ions and ion-forming particles and normally extraction, acid treatment, and so forth. It has secondary
indicates a low concentration of conductive contaminants. application in relating the chemical nature of a liquid to other
phenomena that have been demonstrated to be related to liquid
CHEMICAL PROPERTIES composition.

22. Acidity, Approximate 24. Compatibility with Construction Material

22.1 Scope—Test Method D1534 covers the determination 24.1 Scope—This test method covers screening for the
of the approximate total acid value of used electrical insulating compatibility of materials of construction with electrical insu-
liquids, in general, those having viscosities less than 24 mm2/s lating liquid for use in electrical equipment. Solid materials
at 40°C. It is a simple procedure that can be applied in the ﬁeld. that can be tested for compatibility include varnishes, dip
Where a quantitative neutralization value is required, use Test coatings, core steel, core steel coatings, gaskets, and wire
Method D664 or D974. These test methods should be applied enamels.
in the laboratory.
24.2 Summary of Test Method:
22.2 Summary of Test Method: 24.2.1 Test Methods D3455—The electrical insulating liquid
22.2.1 Test Method D1534—To determine whether the acid- and the material whose compatibility is being tested are aged
ity is greater or less than a ﬁxed arbitrary value, a ﬁxed volume for 164 h at 100 °C. Changes in the liquid and compatibility
of liquid to be tested is added to the test bottle or graduated sample are observed and appropriate tests conducted.
cylinder, together with a small amount of indicator (phenol-
phthalein) and the appropriate quantity of standard potassium 24.3 Signiﬁcance and Use:
hydroxide solution. The mixture is shaken and allowed to 24.3.1 The magnitude of the change in the electrical prop-
separate. The color of the aqueous layer at the bottom of the erties of the insulating liquid is of importance in determining
container when testing mineral liquids, or at the top when the contamination of the liquid by the test specimen.
testing askarels, determines whether the acidity is less than or 24.3.2 Physical and chemical changes in the liquid such as
greater than the arbitrary value chosen. color, interfacial tension, and acidity also indicate solubility or
other adverse effects of the test specimen on the liquid.
22.3 Signiﬁcance and Use: 24.3.3 The physical changes of the test specimen, such as
22.3.1 The approximate acidity of used electrical insulating hardness, swelling, and discoloration, show the effect of the
liquids is an estimate of the total acid value of the liquid. As liquid on the test specimen and are used to determine the
acid values increase, usually due to oxidation of the liquid in suitability of the material for use in insulating liquid.
service, the impairment of those liquid qualities, important to 24.3.4 A material meeting the criteria recommended does
proper functioning of speciﬁc apparatus, increases. In general, not necessarily indicate suitability for use in electrical equip-
acidic by-products produce increased dielectric loss, increased ment. Other properties must also be considered. Additionally,

corrosivity, and may cause thermal difficulties attributable to certain materials containing additives may meet the require-
insoluble components called “sludge.” This test method is ments of this procedure, yet be unsatisfactory when subjected
adapted to a speciﬁc volume of liquid; total acid values of 0.05 to longer term evaluations.
to 0.5 mg of potassium hydroxide per gram of liquid is a range
which is functionally signiﬁcant. 25. Copper Content

23. Carbon-Type Composition 25.1 Scope:
25.1.1 Test Method D3635—Covers the determination of
23.1 Scope—This practice covers the determination of copper in new or used electrical insulating liquid. For ﬂame
carbon-type composition of insulating liquids by correlation atomization, the lower limit of detectability is of the order of
with basic physical properties. Carbon-type composition is 0.1 mg/kg. For nonﬂame atomization, the lower limit of
expressed as percentage of aromatic carbons, percentage of detectability is less than 0.01 mg/kg.
naphthenic carbons, and percentage of paraffinic carbons.
Viscosity, relative density (or speciﬁc gravity), and refractive 25.2 Summary of Test Method:
index are the only measurements required for use of this test 25.2.1 Test Method D3635—The test specimen of liquid is
method. ﬁltered and diluted with an appropriate organic solvent and
analyzed in an atomic absorption spectrophotometer. Alterna-
23.2 Summary of Test Method: tive procedures are provided for instruments employing ﬂame
23.2.1 Practice D2140—The viscosity, density and speciﬁc and nonﬂame atomization. Concentration is determined by
gravity, and refractive index of the liquid are measured. From means of calibration curves prepared from standard samples.
these values, the viscosity-gravity constant and refractivity

10

D117 − 22

25.3 Signiﬁcance and Use—Electrical insulating liquid may It can also be used to detect contamination such as from
contain small amounts of dissolved metals derived either silicone liquids (via silicon) or from dirt (via silicon and
directly from the base oil or from contact with metals during aluminum).
reﬁning or service. When copper is present, it acts as a catalyst

in promoting oxidation of the liquid. This test method is useful 26.3.3 This test method can be used to indicate the effi-
for research and to assess the condition of service-aged liquids. ciency of reclaiming used insulating liquid.

26. Elements in Insulating Oils by Inductively Coupled 27. Furanic Compounds in Electrical Insulating Liquids
Plasma Atomic Emission Spectrometry (ICP-AES)
27.1 Scope—Test Method D5837 covers the determination,
26.1 Scope: in electrical insulating liquids, of the products of the degrada-
26.1.1 This test method describes the determination of tion of cellulosic materials such as paper, pressboard, and
metals and contaminants in insulating liquids by inductively cotton material typically found as insulating materials in
coupled plasma atomic emission spectrometry (ICP-AES). The electrical equipment. These degradation products are substi-
speciﬁc elements are listed in Table 1 of Test Method D7151. tuted furan derivatives, commonly referred to as furanic
This test method is similar to Test Method D5185, but differs compounds or furans.
in methodology, which results in the greater sensitivity re-
quired for insulating liquid applications. 27.1.1 The commonly identiﬁed furans that may be identi-
26.1.2 This test method uses oil-soluble metals for calibra- ﬁed by this method include: 5-hydroxymethyl-2-furaldehyde ,
tion and does not purport to quantitatively determine insoluble furfuryl alcohol, 2-furaldehyde , 2-acetylfuran, and 5-methyl-
particulates. Analytical results are particle size dependent, and 2-furaldehyde .
low results are obtained for particles larger than several
micrometers. 27.2 Summary of Test Method—Furanic compounds in elec-
26.1.3 This test method determines the dissolved metals trical insulating liquids are extracted from a known volume of
(which may originate from overheating) and a portion of the test specimen by means of a liquid/liquid extraction or solid-
particulate metals (which generally originate from a wear phase extraction. A method for direct introduction of liquid into
mechanism). While this ICP method detects nearly all particles the chromatograph is also described. An aliquot of the extract
less than several micrometers, the response of larger particles is introduced into a High Performance Liquid Chromatography
decreases with increasing particle size because larger particles (HPLC) system equipped with a suitable analytical column and
are less likely to make it through the nebulizer and into the UV detector. Furanic compounds in the test specimen are
sample excitation zone. identiﬁed and quantiﬁed by comparison to standards of known
26.1.4 This test method includes an option for ﬁltering the concentration.
liquid sample for those users who wish to separately determine
dissolved metals and particulate metals (and hence, total 27.3 Signiﬁcance and Use—Furanic compounds are gener-

metals). ated by the degradation of cellulosic materials used in solid
26.1.5 Elements present at concentrations above the upper insulation systems of electrical equipment. Furanic compounds
limit of the calibration curves can be determined with which are liquid soluble to an appreciable degree will migrate
additional, appropriate dilutions and with no degradation of into the insulating liquid. High concentrations or unusual
precision. increases in the concentration of furanic compounds in liquid
may indicate cellulose degradation from aging or incipient
26.2 Summary of Test Method: fault conditions.
26.2.1 A weighed portion of a thoroughly homogenized
insulating liquid is diluted 2.5:1 by weight with kerosine or 28. Dissolved Gas Analysis
other suitable solvent. Standards are prepared in the same
manner. An internal standard is added to the solutions to 28.1 Scope:
compensate for variations in test specimen introduction effi- 28.1.1 This test method covers three procedures for the
ciency. The solutions are introduced to the ICP instrument by extraction and measurement of gases dissolved in electrical
a peristaltic pump. If free aspiration is used, an internal insulating liquid having a viscosity of 20 mm2/s or less at
standard must be used. By comparing emission intensities of 40 °C (104 °F), and the identiﬁcation and determination of the
elements in the test specimen with emission intensities mea- individual component gases extracted.
sured with the standards, the concentrations of elements in the 28.1.2 The individual component gases that may be identi-
test specimen are calculated. ﬁed and determined include: hydrogen, oxygen, nitrogen,
carbon monoxide, carbon dioxide, methane, ethane, ethylene,
26.3 Signiﬁcance and Use: acetylene, propane, and propylene.
26.3.1 This test method covers the rapid determination of 12
elements in insulating liquids, and it provides rapid screening 28.2 Summary of Test Methods:
of used liquids for indications of wear. Test times approximate 28.2.1 Method A (Test Method D3612)—Dissolved gases are
several minutes per test specimen, and detectability is in the extracted from a sample of liquid by introduction of the liquid
10-100 µg/kg range. sample into a pre-evacuated known volume. The evolved gases
26.3.2 This test method can be used to monitor equipment are compressed to atmospheric pressure and the total volume
condition and help to deﬁne when corrective action is needed. measured.
28.2.2 Method B (Test Method D3612)—Dissolved gases
are extracted from a sample of liquid by sparging the liquid
with the carrier gas on a stripper column containing a high

surface area bead.

11

D117 − 22

28.2.3 Method C (Test Method D3612) —The sample is reservoir, the pressure is returned to atmospheric, and the
brought in contact with a gas phase in a sealed vial and the volume of the evolved gases is measured. No correction is
dissolved gases are allowed to equilibrate with the gas phase. made for atmospheric pressure or ambient temperature.
The headspace above the liquid is sampled and analyzed. The
amount of dissolved gasses in the liquid is calculated from 29.4 Signiﬁcance and Use:
predetermined partition coefficients for each gas. 29.4.1 Some types of electrical equipment require use of
electrical insulating liquids of low gas content. Capacitors and
28.2.4 There may be some differences in limits of detection certain types of electrical cable, particularly where used at high
and precision and bias between Methods A, B, and C for the voltages, may suffer from the formation of gas bubbles with
various gases. consequent gaseous ionization if gas content is not sufficiently
reduced. In ﬁlling electrical apparatus, a low gas content
28.2.5 A portion of the extracted gases (Methods A and C) reduces foaming and also reduces available oxygen in sealed
or all of the gases extracted (Method B) are introduced into a equipment, increasing the service life of the insulating liquid.
gas chromatograph equipped with suitable adsorption col- 29.4.2 These tests are not intended for use in purchase
umn(s). The composition of the sample is calculated from its speciﬁcations because the liquid is customarily degassed im-
chromatogram by comparing the area of the peak of each mediately before use. These test methods can be used,
component with the area of the peak of the same component on however, as a factory control test and a control and functional
a reference chromatogram made on a standard mixture of test in installation and maintenance work by utilities. These
known composition. tests require care in manipulation and the availability of
trained, careful personnel.
28.3 Signiﬁcance and Use:
28.3.1 Liquid and liquid-immersed electrical insulating ma- 29.5 Precision:
terials may decompose under the inﬂuence of thermal and 29.5.1 The precisions of two of the test methods are given in
electrical stresses and in doing so generate gaseous decompo- the table below. Refer to the original test methods for the

sition products of varying composition, which dissolve in the conditions under which these precision values are applicable.
liquid. The nature and amount of the individual component
gases that may be recovered and analyzed may be indicative of Test Method Unit Repeatability Reproducibility
the type and degree of the abnormality responsible for the gas D831 Gas Content % (if 0.1 %) ... ±0.02
generation. The rate of gas generation and changes in concen- D1827 Gas Content % (0.1 to ... ±0.05
tration of speciﬁc gases over time are also used to evaluate the 15 %)
condition of the electric apparatus.
30. Neutralization (Acid and Base) Number
29. Gas Content of Cable and Capacitor Liquids
30.1 Scope:
29.1 Scope: 30.1.1 The two procedures available determine the acidic or
29.1.1 Test Method D831—Electrical insulating liquids of basic constituents in petroleum products. Because the titration
low and medium viscosities up to 190 mm2/s at 40 °C, end points of these methods differ, results may differ between
including liquids used in capacitors and paper-insulated elec- the test methods.
tric cables and cable systems of the liquid-ﬁlled type. 30.1.2 Test Method D664—Resolves the constituents into
weak-acid and strong-acid components, provided the dissocia-
29.2 Deﬁnition: tion constants of the more highly ionized compounds are at
29.2.1 gas content of an liquid by volume—The total vol- least 1000 times that of the next weaker group. Because the end
ume of gases, corrected to 101 kPa (760 mm Hg) and 0 °C, point is determined potentiometrically, this test method is
contained in a given volume of liquid, expressed as a percent- suitable for use with very dark samples.
age. 30.1.3 Test Method D974—Applicable for the determination
of acids or bases whose dissociation constants in water are
29.3 Summary of Test Methods: larger than 10−9. Constituents are classiﬁed as strong acid,
29.3.1 Test Method D831—The liquid is fed slowly into a weak acid, or strong base. Excessively dark-colored liquids
degassing chamber, located in an oven and initially evacuated cannot be tested by this test method due to obscuration of the
to a pressure below 13 Pa (0.1 Torr) with a vacuum pump, so color indicator end point.
that the liquid is thoroughly exposed to the vacuum. Condens-
able gases are removed from the system by a cold trap. The gas 30.2 Deﬁnitions:
volume is calculated from the increase in pressure in the 30.2.1 total acid number—the number of milligrams of
degassing chamber, measured by a McLeod gage. KOH required to neutralize all acidic constituents present in 1

29.3.2 Test Method D1827—A small liquid sample is purged g of test specimen. When neutralization number is speciﬁed
of dissolved gases with pure carbon dioxide gas. The gas without further qualiﬁcation, total acid number is implied.
stream is then led into a gas burette containing a potassium 30.2.2 strong acid number—the number of milligrams of
hydroxide solution. The carbon dioxide and any other acidic KOH required to neutralize the strong acid constituents present
gases are completely absorbed, and the volume of the remain- in 1 g of test specimen.
ing gas is measured.
29.3.3 Test Method D2945—The liquid sample is allowed to 30.3 Summary of Test Methods:
ﬂow as a thin ﬁlm into a chamber evacuated by the lowering of 30.3.1 Test Method D664—The test specimen is dissolved in
a connecting mercury reservoir. By raising the mercury a mixture of toluene and isopropyl alcohol containing a small
amount of water and titrated potentiometrically with alcoholic

12

D117 − 22

potassium hydroxide or hydrochloric acid solution, using a 31.3 Signiﬁcance and Use—The quantitative determination
glass-indicating electrode and a calomel reference electrode. of 2,6-ditertiary-butyl para-cresol or 2,6-ditertiary-butyl phe-
The meter readings are plotted against the respective volumes nol measures the amount of this material that has been added
of titrating solution, and the end points are taken at the to new electrical insulating liquid as protection against oxida-
inﬂections in the resulting curve. When no deﬁnite inﬂections tion or the amount remaining in a used liquid. These test
are obtained, end points are taken at meter readings corre- methods are also suitable for manufacturing control and for use
sponding to those found for standard nonaqueous acidic and as speciﬁcation acceptance tests.
basic buffer solutions.
32. Oxidation Stability
30.3.2 Test Method D974—To determine the total acid or
strong base number, the test specimen is dissolved in a mixture 32.1 Scope:
of toluene and isopropyl alcohol containing a small amount of 32.1.1 Three oxidation test methods are applied to insulat-
water, and the resulting single-phase solution is titrated at room ing liquid:
temperature with standard alcoholic base or alcoholic acid 32.1.2 Test Method D1934—Covers two procedures for
solution, respectively, to the end point indicated by the color subjecting electrical insulating liquids to oxidative aging:

change of the added p-naphtholbenzein solution. To determine Procedure A, without a metal catalyst, and Procedure B, with a
the strong acid number, a separate portion of the sample is metal catalyst.
extracted with hot water, and the aqueous extract is titrated 32.1.2.1 This test method is applicable to liquids used as
with potassium hydroxide solution, using methyl orange as an impregnating or pressure media in electrical power transmis-
indicator. sion cables as long as less than 10 % of the liquid evaporates
during the aging procedures. It applies and is generally useful
30.4 Signiﬁcance and Use: primarily in the evaluation and quality control of unused
30.4.1 A low total acid content of an insulating liquid is liquids, either inhibited or uninhibited.
necessary to minimize electrical conduction and metal corro- 32.1.2.2 The precision statement for Test Method D1934
sion and to maximize the life of the insulation system. should be the standard deviation of the logarithm of the
30.4.2 In used insulating liquids, an increase in total acid dissipation factor ratios rather than the coefficient of the
number from the value of the unused product indicates variation of the ratios.
contamination by substances with which the liquid has been in 32.1.3 Test Method D2112—Is intended as a rapid method
contact or a chemical change in the liquid from processes such for the evaluation of the oxidation stability of new mineral
as oxidation. An increase in total acid number may indicate the insulating liquids containing oxidation inhibitor. This test is
desirability of replacing used with fresh liquid, provided considered of value in checking the oxidation stability of new
suitable rejection limits have been established and other tests mineral insulating liquids containing synthetic oxidation in-
conﬁrm the need for the change. hibitor in order to control the continuity of this property from
shipment to shipment. The applicability of this procedure for
31. Oxidation Inhibitor Content use with inhibited insulating liquids of more than 12 mm2/s at
40°C has not been established.
31.1 Scope: 32.1.4 Test Method D2440—Covers the evaluation of the
31.1.1 These test methods cover the determination of the acid- and sludge-forming tendency of new mineral transformer
weight percent of 2.6–ditertiary-butyl paracresol (DBPC, insulating liquids. It is considered of value in studying the acid-
BHT) and 2,6-ditertiary-butyl phenol (DBP) in new or used and sludge-forming propensity of a new grade of mineral
electrical insulating liquid in concentrations up to 0.5 %. Two transformer insulating liquid before commercial application.
test methods are available for the determination of the com-
monly used inhibitors. 32.2 Summary of Test Methods:
31.1.2 Test Method D2668—Determines the concentration 32.2.1 Test Method D1934—This test method consists of
of either inhibitor, or their mixtures, in concentrations up to 0.5 exposing for 96 h 300 mL of liquid in a 400 mL beaker to

mass %, by measuring the infrared absorbance of the liquid at moving air in an oven controlled at 115 °C, with or without 15
selected frequencies. cm2 of metal catalyst. Changes in such properties as color, total
31.1.3 Test Method D4768—This test measures the concen- acid number, power factor, and resistivity of the aged liquid
tration of either inhibitors or their mixtures, in concentrations can be used to determine the oxidative deterioration of the
up to 0.5 % mass, by gas chromatographic separation and liquid.
quantitation to a suitable standard. 32.2.2 Test Method D2112—The test specimen is agitated
by rotating axially at 100 rpm at an angle of 30° from the
31.2 Summary of Test Methods: horizontal under an initial oxygen pressure of 620 kPa (90 psi)
31.2.1 Test Method D2668—The infrared absorbance of the in a pressure vessel with a glass sample container and copper
test specimen is measured at the frequencies appropriate to catalyst coil, in the presence of water, at a bath temperature of
2,6-ditertiary-butyl para-cresol and 2,6-ditertiary-butyl phenol 140 °C. The time for an liquid to react with a given volume of
and the concentrations calculated from a calibration curve. oxygen is measured; completion of the test is indicated by a
31.2.2 Test Method D4768—A column clean-up is em- 172 kPa (25 psi) drop in pressure.
ployed to remove interfering substances, followed by a gas 32.2.3 Test Method D2440—The test liquid is charged to a
chromatographic separation and concentration measured by glass oxidation tube containing copper wire catalyst. The tube
comparison to suitable standards.

13

D117 − 22

is placed in a oil bath at 110 °C, and oxygen is bubbled through 34.1.1 Unused and in-service insulating liquids may contain
separate liquid samples for 72 and 164 h. The n-heptane elemental sulfur or sulfur compounds, or both, that cause
insoluble sludge and total acid number of the aged liquid is corrosion under certain conditions of use. This test method is
measured to determine the extent of oxidation. designed to detect the presence of, or the propensity to form,
free (elemental) sulfur and corrosive sulfur compounds by
32.3 Signiﬁcance and Use: subjecting copper or silver to contact with an insulating liquid
32.3.1 The development of liquid sludge and acidity result- under prescribed conditions.
ing from oxidation during storage, processing, and long service
life should be held to a minimum. This minimizes electrical 34.2 Summary of Test Method:

conduction and metal corrosion, maximizes insulation system 34.2.1 Test Method D1275:
life and electrical breakdown strength, and ensures satisfactory 34.2.1.1 Copper Corrosion—220 mL of insulating liquid is
heat transfer. aged in a sealed heavy walled bottle for 48 h at 150°C in the
32.3.2 The oxidation stability tests described in Section 32 presence of a copper strip.
may be used to evaluate the tendency to form sludge or acids 34.2.1.2 Silver Corrosion—220 mL of insulating liquid is
under oxidizing conditions, to ensure the continuity of quality aged in a sealed heavy walled bottle for 48 h at 150°C in the
of mineral insulating liquid shipments, and for speciﬁcation presence of a silver strip.
purposes. A low tendency to form sludge and acid in laboratory
tests is desirable, although the liquid showing the least dete- 34.3 Signiﬁcance and Use—In most of their uses, insulating
rioration in the laboratory is not necessarily the best in service. liquids are continually in contact with metals that are subject to
32.3.3 The oxidation stability Test Methods D2112 and corrosion. The presence of elemental sulfur or corrosive sulfur
D2440 are used in the Speciﬁcations D3487 and D5222 for compounds will result in deterioration of these metals and
insulating liquids. cause conductive or high resistive ﬁlms to form. The extent of
deterioration is dependent upon the quantity and type of
33. Polychlorinated Biphenyl Content (PCB) corrosive agent and time and temperature factors. Detection of
these undesirable impurities, even though not in terms of
33.1 Scope: quantitative values, is a means for recognizing the hazard
33.1.1 Test Method D4059—Describes a quantitative tech- involved.
nique for determining the concentration of polychlorinated
biphenyls (PCBs) in electrical insulating liquids by gas chro- 34.3.1 Two methods are provided, one for copper and one
matography. for silver corrosion. Copper is slightly less sensitive to sulfur
corrosion than silver but the results are easier to interpret and
33.2 Deﬁnition: less prone to error. The silver corrosion procedure is provided
33.2.1 PCB concentration—is normally expressed in units especially for those users who have applications where the
of parts per million (ppm) on a weight by weight basis, insulating liquid is in contact with silver surface.
speciﬁcally in mg/kg. Standard chromatograms of Aroclors 5
1242, 1254, and 1260 are used to determine the concentration 35. Water Content
of PCB in the sample.
35.1 Scope—Test Method D1533 covers the determination
33.3 Summary of Test Method—Following dilution of the of water present in insulating liquids, in concentrations most

test specimen in a suitable solvent, the solution is treated to commonly below 200 ppm.
remove interfering substances. A small portion is then injected
into a gas chromatographic column where the components are 35.2 Summary of Test Method:
separated and their presence measured by an electron capture 35.2.1 This test method is based on the reduction of iodine
or halogen-speciﬁc electrolytic conductivity detector. The test in accordance with the traditional Karl Fischer reaction.
method is made quantitative by comparing the response of a 35.2.2 Test Method D1533 electrochemically generates the
sample to that of a known quantity of one or more standard iodine required for Karl Fischer titration.
Aroclors obtained under the same conditions. 35.2.3 This automatic coulometric titration procedure re-
quires the use of an instrument that is designed and calibrated
33.4 Signiﬁcance and Use—National, state and local regu- to deliver a known electrical current which generates sufficient
lations require that electrical apparatus and electrical insulating iodine to neutralize a known weight of water per minute. The
liquids containing PCB be handled and disposed of through the two-part titration solution is ﬁrst brought to near a zero dryness
use of speciﬁc procedures as determined by the PCB content of by iodine produced by the generator when the controls are
the insulating liquid. The results of this test method can be placed in the “standby” setting. The test specimen is added; and
useful in selecting appropriate handling and disposal proce- the titration begun, allowing the test specimen to be automati-
dures. cally titrated by producing iodine at the generator anode until
the equivalent point is reached and the titration is complete.
34. Sulfur, Corrosive Water content is read directly on the meter in micrograms (or
parts per million).
34.1 Scope—This test method covers the detection of cor-
rosive sulfur compounds (both organic and inorganic) in 35.3 Signiﬁcance and Use—A low water content of insulat-
electrical insulating liquids. ing liquid is necessary to achieve adequate electrical strength
and low dielectric loss characteristics, to maximize the insula-
5 Registered trademark of Monsanto Co. tion system life, and to minimize metal corrosion. Water in

14

D117 − 22

solution cannot be detected visually and must be determined by application. The material described in this speciﬁcation may

other means. This test shows the presence of water that may not not be miscible with electrical insulating liquids of non-
be evident from electrical tests. petroleum origin. The user should contact the manufacturer of
the high ﬁre point insulating liquid for guidance in this respect.
SPECIFICATIONS
37.1.4 This speciﬁcation applies only to new insulating
36. Mineral Insulating Liquid for Electrical Apparatus material, liquid as received prior to any processing. Informa-
tion on in-service maintenance testing is available in appropri-
36.1 Scope: ate guides. The user should contact the manufacturer of the
36.1.1 Speciﬁcation D3487—The physical, chemical, and equipment if questions of recommended characteristics or
electrical properties of two types of unused mineral insulating maintenance procedures arise.
liquid of petroleum origin for use as an insulating and cooling
medium in new and existing power and distribution electrical 38. Silicone Fluid used for Electrical Insulation
apparatus, such as transformers, regulators, reactors, liquid-
ﬁlled circuit breakers, switchgear, and attendant equipment are 38.1 Scope:
given in this speciﬁcation. 38.1.1 Speciﬁcation D4652 covers silicone ﬂuid for use in
36.1.2 Type I liquid has a maximum oxidation inhibitor transformers, capacitors, and electronic assemblies as an insu-
content of 0.08 mass % and Type II liquid a maximum of 0.3 lating or cooling medium, or both.
mass %. Except for the inhibitor content and oxidation stability 38.1.2 Silicone ﬂuid covered by this speciﬁcation is poly-
requirements, the two liquids have similar performance prop- dimethylsiloxane having a normal viscosity of 50 cSt at 25 °C
erties. and a ﬁre point of 340 °C or greater. This speciﬁcation applies
36.1.3 Speciﬁcation D3487 is intended to deﬁne a mineral only to new silicone ﬂuid. Information on in-service mainte-
insulating liquid that is functionally interchangeable with nance testing is available in appropriate guides.
existing liquids, is compatible with existing apparatus and with
appropriate ﬁeld maintenance, and will satisfactorily maintain 39. Natural (Vegetable Oil) Ester Fluids used in
its functional characteristics in its application in electrical Electrical Apparatus
equipment. This speciﬁcation applies only to new insulating
liquid prior to introduction into apparatus. 39.1 Scope:
39.1.1 Speciﬁcation D6871 covers a less ﬂammable natural
37. Less Flammable Electrical Insulating Liquids vegetable ester insulating liquid for use as a dielectric and
cooling medium in new and existing power and distribution

37.1 Scope: electrical apparatus such as transformers and attendant equip-
37.1.1 Speciﬁcation D5222 describes a less ﬂammable min- ment.
eral based insulating liquid, for use as a dielectric and cooling 39.1.2 This speciﬁcation is intended to deﬁne a natural
medium in new and existing power and distribution electrical vegetable ester electrical insulating liquid that is compatible
apparatus, such as transformers and switchgear. with typical materials of construction of existing apparatus and
37.1.2 Less ﬂammable insulating liquid differs from con- will satisfactorily maintain its functional characteristic in this
ventional mineral insulating liquid by possessing a ﬁre-point of application. The material described in this speciﬁcation may
at least 300 °C. This property is necessary in order to comply not be miscible with some synthetic electrical insulating
with certain application requirements of the National Electric liquids. The user should contact the manufacturer of the natural
Code (Article 450-23) or other agencies. The material dis- ester insulating liquid for guidance in this respect.
cussed in this speciﬁcation is miscible with other petroleum 39.1.3 This speciﬁcation applies only to new insulating
based insulating liquids. Mixing high ﬁre-point liquids with liquid as received prior to any processing. The user should
lower ﬁre-point hydrocarbons insulating liquids (for example, contact the manufacturer of the equipment or liquid if ques-
Speciﬁcation D3487 mineral liquid) may result in ﬁre points tions of recommended characteristics or maintenance proce-
less the 300 °C. dures arise.
37.1.3 This speciﬁcation is intended to deﬁne a less ﬂam-
mable electrical mineral insulating liquid that is compatible 40. Keywords
with typical material of construction of existing apparatus and
will satisfactorily maintain its functional characteristic in its 40.1 chemical properties; electrical insulating liquids; elec-
trical properties; measured; physical properties; properties;
sampling; speciﬁcation

15

D117 − 22

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16

ASTM D117-22 Standard Guide for Sampling, Test Methods, and Specifications for Electrical Insulating Liquids

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