ASTM D923-15(2023)

Standard Practices for Sampling Electrical Insulating Liquids

SIGNIFICANCE AND USE
4.1 Accurate sampling, whether of the complete contents or only parts thereof, is extremely important from the standpoint of evaluating the quality of the liquid insulant sampled. Obviously, examination of a test specimen that, because of careless sampling procedure or contamination in sampling equipment, is not directly representative, leads to erroneous conclusions concerning quality and in addition results in a loss of time, effort, and expense in securing, transporting, and testing the sample.  
4.2 A study of gases and moisture contained in insulating oils from transformers and other electrical power apparatus can frequently give an early indication of abnormal behavior of the apparatus, and may indicate appropriate action be taken on the equipment before it suffers greater damage. Specific gas and moisture content can be determined from oil sampled for this purpose.
SCOPE
1.1 These practices cover sampling of new electrical insulating liquids including oils, askarels, silicones, synthetic liquids, and natural ester insulating liquids as well as those insulating liquids in service or subsequent to service in cables, transformers, circuit breakers, and other electrical apparatus. These practices apply to liquids having a viscosity of less than 6.476 × 10-4 m2/s (540 cSt) at 40 °C (104 °F).  
1.2 Representative samples of electrical insulating liquids are taken for test specimens so that the quality pertinent to their use may be determined. The quality in different portions of a given container, or the average quality of the whole bulk may be ascertained if desired.  
1.3 The values stated in SI units are regarded as the standard where applicable. Inch pound units are used where there is no SI equivalent.  
1.4 These practices also include special techniques and devices for sampling for dissolved gases-in-oil (DGA) (D3612), water (D1533) and particles (D6786).  
1.5 For ease of use, this document has been indexed as follows:    
Section Title  
Section/Paragraph  
Mandatory Conditions and General Information  
Section 5  
Description of Sampling Devices and Containers  
Section 6, Annex A1, Appendix X2  
Most Frequently Used Sampling Techniques for Electrical Apparatus  
Collecting Samples from Electrical Equipment Using Bottles and Cans  
Section 7, Appendix X1, Appendix X2  
Collecting Samples from Electrical Equipment Using Glass Syringes (DGA and Water Analysis)  
Section 8  
Collecting Samples from Electrical Equipment Using Stainless Steel Cylinders (DGA and Water Analysis)  
Section 9  
Sampling of Cans, Drums, Tank Cars, Tank Trucks and Small Electrical Equipment  
Sampling Using the Dip-Type Device (drum thief)  
Section 10  
Sampling Using the Pressure-Type Device  
Section 11, Annex A1.1  
Sampling Using the Tank Car-Type Device  
Section 12, Annex A1.2  
Sampling Cable Feeders  
Mandatory Conditions  
Section 13  
General Considerations  
Section 14  
Sampling Using the Manifold-Type Device  
Section 15, Annex A1.3  
Cleaning, Preparation, Storage, and Handling of Sampling Containers  
Section 16  
Storage, Packaging and Shipping of Samples  
Section 17  
Cleaning and Storage of Sampling Devices  
Section 18  
Sample Information  
Section 19  
Mandatory Information—Construction of Sampling Devices  
Annex A1  
Determination of Electrical Apparatus Temperature  
Appendix X1  
Sample Container Types  
Appendix X2  
1.6 Handle askarels containing polychlorinated biphenyls (PCBs) according to federal and local regulations existing for that country. For example, the federal regulations concerning PCBs in the United States can be found in 40 CFR Part 761.  
1.7 Properly contain, package and dispose of any liquid or material resulting from the use of these practices in a manner that is in accordance with local and state regulations specific to the country in w...

General Information

• Status: Published
• Publication Date: 30-Nov-2023
• ICS: 29.040.10 - Insulating oils
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.07 - Physical Test

Relations

• Replaces: ASTM D923-15 - Standard Practices for Sampling Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Refers: ASTM D6786-15(2023) - Standard Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
• Effective Date: 01-Dec-2023
• Referred By: ASTM D8112-22 - Standard Guide for Obtaining In-Service Samples of Turbine Operation Related Lubricating Fluid
• Effective Date: 01-Dec-2023
• Referred By: ASTM D6786-15 - Standard Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
• Effective Date: 01-Dec-2023
• Referred By: ASTM D2225-20 - Standard Test Methods for Silicone Liquids Used for Electrical Insulation
• Effective Date: 01-Dec-2023
• Referred By: ASTM D924-23 - Standard Test Method for Dissipation Factor (or Power Factor) and Relative Permittivity (Dielectric Constant) of Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Referred By: ASTM D4768-11(2019) - Standard Test Method for Analysis of 2,6-Ditertiary-Butyl Para-Cresol and 2,6-Ditertiary-Butyl Phenol in Insulating Liquids by Gas Chromatography
• Effective Date: 01-Dec-2023
• Referred By: ASTM D1816-12(2019) - Standard Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using VDE Electrodes
• Effective Date: 01-Dec-2023
• Referred By: ASTM D5837-15 - Standard Test Method for Furanic Compounds in Electrical Insulating Liquids by High-Performance Liquid Chromatography (HPLC)
• Effective Date: 01-Dec-2023
• Referred By: ASTM D2668-07(2021) - Standard Test Method for 2,6-<emph type="bold"><emph type="ital">di-tert</emph></emph >-Butyl-<emph type="bold"><emph type="ital"> p</emph></emph>-Cresol and 2,6-<emph type="bold"><emph type="ital">di-tert</emph></emph>-Butyl Phenol in Electrical Insulating Oil by Infrared Absorption
• Effective Date: 01-Dec-2023
• Referred By: ASTM D1275-15 - Standard Test Method for Corrosive Sulfur in Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Referred By: ASTM D2140-23 - Standard Practice for Calculating Carbon-Type Composition of Insulating Oils of Petroleum Origin
• Effective Date: 01-Dec-2023
• Referred By: ASTM D6871-17 - Standard Specification for Natural (Vegetable Oil) Ester Fluids Used in Electrical Apparatus
• Effective Date: 01-Dec-2023
• Referred By: ASTM D5222-23 - Standard Specification for Less Flammable High Molecular Weight Hydrocarbon Mineral Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Referred By: ASTM D7151-15 - Standard Test Method for Determination of Elements in Insulating Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
• Effective Date: 01-Dec-2023

Overview

ASTM D923-15(2023): Standard Practices for Sampling Electrical Insulating Liquids is a widely recognized ASTM standard that establishes best practices for obtaining representative samples of electrical insulating liquids. These liquids include transformer oils, askarels, silicones, synthetic fluids, and natural ester-based liquids in both new and in-service conditions. The document covers essential sampling methods to ensure samples are uncontaminated and accurately reflect the quality of the liquid, aiding in consistent laboratory analysis and reliable monitoring of electrical equipment performance.

Proper sampling is fundamental for evaluating the condition and integrity of electrical insulating liquids. This standard addresses the practical requirements for different types of equipment, sampling devices, containers, and techniques, as well as safety and regulatory considerations. Adhering to ASTM D923-15(2023) ensures the effectiveness of diagnostic tests for dissolved gases, moisture, and contaminant particles, which are critical for predictive maintenance and asset management in the power industry.

Key Topics

• Significance of Representative Sampling: Ensures that laboratory analysis reflects the true condition of insulating liquids, preventing misleading results caused by contamination or improper technique.
• Sampling Scope: Applies to liquids with viscosity below 540 cSt at 40°C, including new and used insulating liquids in transformers, cables, circuit breakers, drums, tank cars, and other apparatus.
• Sampling Devices and Containers:
  • Glass bottles and jars (clear or amber for light sensitivity)
  • Stainless steel cylinders (for dissolved gas analysis and moisture determination)
  • Glass syringes
  • "Dip-type" devices (drum thief)
  • Pressure-type and tank car-type samplers
  • Manifold-type devices for closed system sampling
• Techniques for Different Equipment: Detailed procedures for collecting samples from energized and de-energized electrical equipment, large storage tanks, drums, and cable feeders.
• Handling and Storage: Procedures for cleaning, prepping, storing, and transporting sample containers to avoid contamination and preserve sample integrity.
• Compliance and Safety: Emphasizes adherence to local, national, and international regulations, especially for liquids containing PCBs.
• Special Sampling Considerations: Includes methods for dissolved gas analysis (DGA), water content measurement, and particle count testing.

Applications

The standard addresses practical needs in several core application areas:

• Electrical Power Equipment Maintenance: Routine sampling according to ASTM D923-15(2023) allows for early detection of faults in transformers, circuit breakers, cables, and related apparatus by analyzing key quality indicators such as gas content and moisture.
• Quality Control for New Insulating Liquids: Ensures new insulating oils and fluids sent from manufacturers or delivered to site are contaminant-free and meet required specifications before commissioning.
• In-Service Condition Monitoring: Periodic sampling supports trending of dissolved gases, water, or particulates, providing actionable data for preventive and predictive maintenance.
• Asset Life Extension: By identifying contamination or degradation early, utilities can plan interventions, reducing the risk of equipment failure and extending service life.
• Regulatory Compliance: Provides a framework for complying with regulatory mandates for handling and disposing of insulating liquids, especially those containing hazardous substances such as PCBs.

Related Standards

ASTM D923-15(2023) is closely associated with several other standards and test methods, including:

• ASTM D1533: Test Method for Water in Insulating Liquids by Coulometric Karl Fischer Titration
• ASTM D3612: Test Method for Analysis of Gases Dissolved in Electrical Insulating Oil by Gas Chromatography
• ASTM D6786: Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
• ASTM D4057: Practice for Manual Sampling of Petroleum and Petroleum Products
• ASTM D1933: Specification for Nitrogen Gas as an Electrical Insulating Material

These supporting standards provide laboratory techniques and equipment specifications that complement the sampling practices in ASTM D923-15(2023). For comprehensive oil analysis and transformer monitoring, utilities and laboratories should integrate this standard within a broader quality management and diagnostic framework.

By following ASTM D923-15(2023), organizations ensure accuracy in insulating liquid testing, aligning with industry best practices and regulatory expectations for reliability and safety in electrical power systems.

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: D923 − 15 (Reapproved 2023)
Standard Practices for
Sampling Electrical Insulating Liquids
This standard is issued under the fixed designation D923; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
Section/
Section Title
Paragraph
1.1 These practices cover sampling of new electrical insu-
lating liquids including oils, askarels, silicones, synthetic Sampling of Cans, Drums, Tank Cars, Tank Trucks and
Small Electrical Equipment
liquids, and natural ester insulating liquids as well as those
Sampling Using the Dip-Type Device (drum thief) Section 10
insulating liquids in service or subsequent to service in cables,
Sampling Using the Pressure-Type Device Section 11,
transformers, circuit breakers, and other electrical apparatus. Annex A1.1
Sampling Using the Tank Car-Type Device Section 12,
These practices apply to liquids having a viscosity of less than
Annex A1.2
-4 2
6.476 × 10 m /s (540 cSt) at 40 °C (104 °F).
Sampling Cable Feeders
Mandatory Conditions Section 13
1.2 Representative samples of electrical insulating liquids
General Considerations Section 14
are taken for test specimens so that the quality pertinent to their
Sampling Using the Manifold-Type Device Section 15,
Annex A1.3
use may be determined. The quality in different portions of a
Cleaning, Preparation, Storage, and Handling of Section 16
given container, or the average quality of the whole bulk may
Sampling Containers
be ascertained if desired. Storage, Packaging and Shipping of Samples Section 17
Cleaning and Storage of Sampling Devices Section 18
1.3 The values stated in SI units are regarded as the standard
Sample Information Section 19
where applicable. Inch pound units are used where there is no
Mandatory Information—Construction of Sampling Devices Annex A1
SI equivalent.
Determination of Electrical Apparatus Temperature Appendix X1
Sample Container Types Appendix X2
1.4 These practices also include special techniques and
devices for sampling for dissolved gases-in-oil (DGA)
1.6 Handle askarels containing polychlorinated biphenyls
(D3612), water (D1533) and particles (D6786).
(PCBs) according to federal and local regulations existing for
that country. For example, the federal regulations concerning
1.5 For ease of use, this document has been indexed as
PCBs in the United States can be found in 40 CFR Part 761.
follows:
Section/
1.7 Properly contain, package and dispose of any liquid or
Section Title
Paragraph
material resulting from the use of these practices in a manner
Mandatory Conditions and General Information Section 5 that is in accordance with local and state regulations specific to
Description of Sampling Devices and Containers Section 6,
the country in which the samples are taken.
Annex A1,
Appendix X2
1.8 This standard does not purport to address all of the
Most Frequently Used Sampling Techniques for
safety concerns, if any, associated with its use. It is the
Electrical Apparatus
Collecting Samples from Electrical Equipment Using Bottles Section 7,
responsibility of the user of this standard to establish appro-
and Cans Appendix X1,
priate safety, health, and environmental practices and deter-
Appendix X2
mine the applicability of regulatory limitations prior to use.
Collecting Samples from Electrical Equipment Using Glass Section 8
Syringes (DGA and Water Analysis)
Specific warning statements are given in 1.6, 1.7, Section 5,
Collecting Samples from Electrical Equipment Using Section 9
10.1, 13.2, 15.2.3, Section 16, and 18.2. These practices
Stainless Steel Cylinders (DGA and Water Analysis)
involve close contact with the electrical insulating liquids
being sampled as well as liquids and other materials used to
clean the sampling tools and devices. When required, or as a
matter of diligence to personal safety, use personal protective
These practices are under the jurisdiction of ASTM Committee D27 on
equipment (PPE).
Electrical Insulating Liquids and Gases and are the direct responsibility of
Subcommittee D27.07 on Physical Test.
1.9 This international standard was developed in accor-
Current edition approved Dec. 1, 2023. Published December 2023. Originally
dance with internationally recognized principles on standard-
approved in 1947. Last previous edition approved in 2015 as D923 – 15. DOI:
10.1520/D0923-15R23. 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
D923 − 15 (2023)
Development of International Standards, Guides and Recom- 5. Mandatory Conditions and General Information
mendations issued by the World Trade Organization Technical
5.1 Mandatory Conditions when Sampling Electrical Appa-
Barriers to Trade (TBT) Committee.
ratus:
5.1.1 Energized electrical apparatus being sampled must
2. Referenced Documents
have a positive pressure at the sampling outlet, so as not to
2.1 ASTM Standards: introduce an air bubble into the apparatus during the sampling
process. Refer to 7.2.
D1533 Test Method for Water in Insulating Liquids by
Coulometric Karl Fischer Titration 5.1.2 Do not draw samples from any energized electrical
D1933 Specification for Nitrogen Gas as an Electrical Insu- equipment with a small volume of oil, especially those that
lating Material require the addition of oil to maintain the electric strength of
D3612 Test Method for Analysis of Gases Dissolved in the insulation system. If the proper level or existing level can
Electrical Insulating Oil by Gas Chromatography not be accurately determined do not proceed.
D4057 Practice for Manual Sampling of Petroleum and 5.1.3 Maintain the insulating fluid within the electrical
Petroleum Products
apparatus being sampled at a level that will not reduce the
D6786 Test Method for Particle Count in Mineral Insulating electric strength of the insulation system.
Oil Using Automatic Optical Particle Counters
5.1.4 Do not sample electrical apparatus if only a drain plug
is provided, as it would be difficult to control the flow.
3. Terminology
5.1.5 Do not draw samples from energized instrument
transformers such as CTs and PTs.
3.1 Definitions:
5.1.6 Do not draw samples from an energized switch or the
3.1.1 sampling, v—the obtaining of that amount of a mate-
cable termination compartment of network transformers.
rial which is adequate for making the required tests and which
is representative of that portion of the material from which it is
5.2 General Information:
taken.
5.2.1 Take and handle samples or test specimens in such a
3.1.1.1 Discussion—In most cases the detection of contami-
manner as to avoid the loss or gain of properties for which they
nants that are not ordinarily dispersed uniformly through the are being tested. Some tests are greatly affected by minute
liquid being sampled, such as water or solid particles, neces-
traces of impurities, and it is imperative that utmost precau-
sitates taking samples at specific locations where the contami- tions be taken to prevent contamination when obtaining
nants are likely to be found. For a liquid having a relative samples. Due to the hygroscopic tendency of insulating liquids,
density (specific gravity) less than one, water and some other it is important to minimize exposure to the atmosphere of the
impurities are most likely to be found on or near the bottom. In sample being taken.
the case of a liquid having a specific gravity greater than one,
5.2.2 Take a sufficient quantity of liquid as a sample to
some of these impurities are most likely to be found on or near
cover the requirements of the respective tests to be made. Make
the surface. reference to the procedures governing these tests to ascertain
the quantity of liquid for each test specimen and the number of
4. Significance and Use test specimens required.
5.2.3 When samples are to be taken the temperature of the
4.1 Accurate sampling, whether of the complete contents or
liquid should be equal to or greater than the temperature of the
only parts thereof, is extremely important from the standpoint
surrounding air in order to minimize the possibility of con-
of evaluating the quality of the liquid insulant sampled.
densed moisture from the air being absorbed by the liquid
Obviously, examination of a test specimen that, because of
during the sampling process, particularly in a humid atmo-
careless sampling procedure or contamination in sampling
sphere.
equipment, is not directly representative, leads to erroneous
5.2.4 When taking samples of liquid from large storage
conclusions concerning quality and in addition results in a loss
tanks, transformers, oil-circuit breakers, gravity-fed reservoirs
of time, effort, and expense in securing, transporting, and
on oil-filled cable feeders, and other electrical equipment, the
testing the sample.
electrical equipment drain valve is usually adequate. However,
4.2 A study of gases and moisture contained in insulating
when high relative humidity conditions exist and it is desired to
oils from transformers and other electrical power apparatus can
obtain samples through a closed system, the manifold in Fig.
frequently give an early indication of abnormal behavior of the
10 is recommended.
apparatus, and may indicate appropriate action be taken on the
5.3 General Information when Sampling Electrical Appara-
equipment before it suffers greater damage. Specific gas and
tus:
moisture content can be determined from oil sampled for this
5.3.1 All non-hermetically sealed equipment, filled with
purpose.
insulating liquid having a relative density (specific gravity) less
than 1, should be provided with the sampling outlet located at
the bottom of the tank so that bottom samples of the oil may be
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
obtained.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
5.3.2 All non-hermetically sealed equipment, filled with
Standardsvolume information, refer to the standard’s Document Summary page on
the ASTM website. insulating liquid having a relative density (specific gravity)
D923 − 15 (2023)
greater than 1, should be provided with the sampling outlet de-energized electrical apparatus. This device is especially
located at the top of the tank at the 25 °C (77 °F) liquid level suitable when collecting samples in a glass jar, metal can, or
so that a top sample of the liquid may be obtained. other suitable containers as described in this section.
5.3.3 When make-up liquid is added to any piece of
6.3 Glass Bottle—Used for securing and storing the sample.
electrical equipment or the liquid is filtered, allow sufficient
Amber or clear (see Notes 1 and 2) and may be either
time to lapse to allow for complete mixing before sampling in
glass-stoppered or fitted with screw caps having a pulp-board
order that a representative sample is obtained.
liner faced with tin or aluminum foil, or with a suitable
5.3.4 If samples or test specimens must be taken when the
oil-resistant plastic such as polyethylene, polytetrafluoroethyl-
liquid temperature is below 0 °C (32 °F), high water content
ene (PTFE) or fluoro-elastomers. Do not use any incompatible
may not be detected because of the formation of ice. Ice is a
natural or synthetic rubber materials. Must meet the require-
concern in both energized and de-energized electrical appara-
ments of Section 16. (See Appendix X2.)
tus where insulating oil-filled compartments operate at tem-
NOTE 1—While amber-colored glass bottles are used for storing
peratures below freezing, such as some tap changer compart-
samples as protection against light, clear glass bottles afford better visual
ments and circuit breaker tanks.
inspection of the samples or test specimens for impurities such as water
5.3.5 When retrieving samples from electrical apparatus, and foreign particles. Take samples that are to be subjected to referee tests
in new amber-colored containers that have been cleaned as described in
record the apparatus temperature (°C) along with the identifi-
Section 16.
cation information as required by Section 19. Knowledge of
the apparatus temperature (°C) at the time of sampling aids in 6.4 Other Bottle or Can Containers (Note 2)—Used for
securing and storing the sample. May be constructed from a
the interpretation of results from certain tests (refer to Appen-
dix X1). suitable oil-resistant plastic such as high-density polyethylene
(HDPE) (do not use for long term storage when water content
5.4 General Information when Sampling Liquid-Filled
is to be determined), or metal cans such as those made from
Tanks, Drums, Tank Trucks, Tank Cars and other Similar
aluminum, stainless steel, other appropriate metal, or PTFE
Containers:
lined. Metals cans are to be constructed as fully extruded,
5.4.1 When sampling large outdoor tanks, tank trucks, tank
pressed seams or welded seams. Solder seams may leave a
cars, and de-energized electrical equipment the temperature of
residue that will contaminate the sample. Screw caps and
the liquid to be sampled may be colder than the surrounding
closures must meet the requirements of 6.3. (See Appendix
air. On such an occasion, determine and report the temperature
X2.)
of the liquid and air as well as the relative humidity with the
NOTE 2—It is recommended to retrieve samples for DGA and water
results of tests. It is undesirable to collect samples that are
analysis using only syringes or stainless steel cylinders. If bottles and cans
exposed to the atmosphere when the relative humidity exceeds
are used, gases that are to be measured in the DGA analysis can easily
50 % or under conditions of rain or snow.
escape from these types of containers. Alternatively, environmental gases
5.4.2 Allow containers of new liquid to remain undisturbed can become entrained into the sample. Both situations can alter the results
significantly.
for at least 8 h before samples or test specimens are taken. In
some instances, such as in the case of tank cars, it is not
6.5 Glass Syringe—The device shown in Fig. 1 must be of
practical to wait this prescribed length of time, and samples for
a suitable size terminated with a Luer lock fitting to which is
routine tests may be taken after the liquid has remained
attached a three-way stopcock. It is used for taking samples
undisturbed for as long a period as practicable. For referee
usually from a valve located on an insulating liquid-filled
tests, allow the full 8-h waiting period to elapse before taking
electrical apparatus. Syringes having precision ground barrels
samples or test specimens. Repeat samples or test specimens
and pistons are preferred. This sampling device is the preferred
from tank cars may be taken without waiting an additional 8 h.
mechanism for taking samples for dissolved gases-in-oil and
5.4.3 Unless otherwise specified, take samples of insulating
water content. Refer to Figs. 1–4 for step by step instruction on
liquids having a relative density (specific gravity) of less than
how the device is to be used. (See Appendix X2.)
1 from the bottom of the liquid container. For drums, cans,
6.5.1 Stopcocks used on syringes must be compatible with
small tanks, etc., design the sampling device so that the sample
the insulating liquid being sampled. Polycarbonate and poly-
is obtained a distance of 3 mm from the bottom of the
styrene for example stopcocks are not appropriate.
container, while for large tanks, tank trucks and tank cars, the
6.6 Stainless Steel Sampling Cylinders—The device shown
distance is within 13 mm of the bottom.
in Fig. 5 is equipped with valves on each end may be used for
5.4.4 Unless otherwise specified, take samples of insulating
sampling from a valve located on an insulating liquid-filled
liquids having a relative density (specific gravity) of greater
electrical apparatus. This is an alternative sampling device for
than 1 from the surface layer of the liquid.
taking samples for dissolved gases-in-oil, water content, and
6. Description of Sampling Devices and Containers
areas of excessive environmental contamination.
6.6.1 The materials of construction of the valves used on
6.1 Devices suitable for withdrawing samples of liquid from
stainless steel cylinders must be compatible with the liquid
containers, electrical equipment, cable feeders, and cable joints
being sampled. Valve packing materials such as Nitrile rubber,
are described below, shown in Figs. 1–10 and the Annex, and
fluoro-elastomers and PTFE have been found suitable.
discussed in Appendix X1.
6.2 Electrical Equipment Sampling Drain Valve or Port— 6.7 Dip Type or Drum Thief—The device shown in Fig. 6 is
Used for taking top or bottom samples from energized or used for taking bottom samples from drums, storage tanks, and
D923 − 15 (2023)
small de-energized electrical equipment, that are to be sub- discontinued. If the slug moves away from the electrical
jected to routine tests. It is fabricated of metal, glass or a apparatus, a positive pressure exists, and samples can be
compatible plastic and available from most laboratory supply obtained safely. Close the drain valve and then close the drain
houses. It is not recommended for use under the following valve port. Take extreme care in performing this procedure.
conditions:
7.3 Place a flush-oil container under the main drain valve
6.7.1 When the samples are to be subjected to referee tests,
and remove the drain valve pipe plug. Wipe the inside of the
6.7.2 When the relative humidity of the atmosphere exceeds
valve and threads with a clean lint-free cloth making sure to
50 %,
remove all debris, water and plug sealing materials. Drain at
6.7.3 When the samples are to be tested for dissipation
least 2 L and preferably 4 L of liquid into the flush-oil container
factor, resistivity, or moisture content, and
to flush the drain valve and drain valve extension. One of two
6.7.4 When the viscosity of the liquid to be sampled exceeds
procedures may then be used to prepare the drain valve for
-5 2
2.28 × 10 m /5 (21 cSt) at 40 °C.
sampling.
7.3.1 Procedure A—Install a sample adapter on the drain
6.8 Pressure Type—The device shown in Figs. 7 and 8 is
valve (suitable thread size bushing adapter NPT to ⁄8 in. or
intended primarily for sampling drums of high-viscosity liq-
⁄4 in. bayonet) with a piece of oil-resistant tubing attached (see
uids. However, it is particularly suitable for obtaining samples
Note 3). Stainless steel adapters and tubing have also been
of all electrical insulating liquids in drums where it is desired
found to be practical for this purpose. Flush the valve and
that all contact of the sample with the atmosphere is elimi-
installed sample adapter by flushing at least 1 L of liquid into
nated. When possible, this device should be used for obtaining
the flush-oil container before collecting sample.
samples from drums when these samples are to be subjected to
7.3.2 Procedure B—This is an alternate procedure for purg-
referee tests.
ing the valve when it is not practical to flush oil through the
6.9 Tank Car Type—The device shown in Fig. 9 is used for
drain valve or a flush container or catch pan cannot be placed
taking either top, middle, or bottom samples from containers of
below the valve. Install the drain valve pipe plug. Attach oil
large capacity such as tank cars, tank trucks, and large storage
resistant tubing (see Note 3) to the sample port on the side of
tanks not provided with a sampling-test nipple. This device is
the drain valve and flush at least 2 L of liquid into the flush oil
not recommended for use under the conditions described in
container before collecting the liquid in the sample container.
6.7.1 through 6.7.4.
NOTE 3—A new piece of oil-resistant tubing is to be used every time a
6.10 Manifold—The device shown in Fig. 10 is used for
sample is taken. Be aware that plastic tubing can retain water that can be
taking samples from low-pressure oil-filled cable feeders with
imparted to the sample during sampling. For this reason, flushing the
the use of vacuum and either dry carbon dioxide gas or dry
tubing along with the sample container is necessary to remove that
nitrogen gas. Its use is recommended when high relative moisture.
humidity conditions exist and it is desired to take the samples
7.4 Adequately protect the area from which the sample is
through a closed system.
being drawn from spillage by the use of such countermeasures
as plastic, oil absorbent pads and catch pans.
MOST FREQUENTLY USED SAMPLING
TECHNIQUES FOR ELECTRICAL APPARATUS 7.5 When collecting the sample in a glass jar, bottle or metal
can, hold the sample container so that the liquid will run down
the sides and limit aeration of the liquid. Partially fill the
7. Collecting Samples from Electrical Apparatus Using
sample container 2 to 3 times and gently swirl the liquid around
Bottles and Cans
to warm the container in order to prevent condensation.
7.1 Unrepresentative samples are often obtained when sam-
Discard the liquid after each rinse. The flow of liquid should be
pling electrical apparatus using the sampling ports mounted on
gentle but not interrupted from the start of the flushing of the
drain valves without appropriate preparation. The flow allowed
valve and container to the completion of the final filling of the
by these ports is not adequate to properly flush the drain valve
sample container.
and drain valve extension of the electrical apparatus. Since the
fluid in the drain valve and extension remain quite dormant 7.6 Obtain the sample for evaluation by allowing the liquid
to flow down the sides of the container or from the bottom up,
during the normal operation of the electrical apparatus, con-
tamination with stem packing and moisture must be thoroughly filling the container.
flushed prior to the collection of a sample. 7.6.1 If glass sample containers are used, adequate space
should remain in the container to allow for expansion of the
7.2 Check for positive pressure at a sampling outlet by
liquid. This applies to samples that are collected at tempera-
placing a slug of insulating liquid in a piece of clear oil-
tures below the temperature of the sample storage area. If metal
resistant plastic tubing and attaching it to the sampling port
cans, bottles or cylinders are used fill the container to over-
(also known as sampling cock) located on the side of the drain
flowing. Once the container has been filled to the appropriate
valve. With the valve closed, remove the drain valve pipe plug,
level install the cap immediately.
making sure to catch any waste and debris, and then reinstall
the pipe plug to equalize the pressure. While observing the slug 7.7 Close the drain valve, remove the sample adapter, if
of insulating liquid, open the sampling port and then slowly used, and install the drain valve pipe plug with a non-hardening
open the drain valve. If the slug moves towards the electrical thread sealant. Do not reuse the tubing. Clean the sample
apparatus, a negative pressure exists, and sampling is to be adapter before reusing on other oil-filled compartments or
D923 − 15 (2023)
FIG. 1 Stopcock with Two Open Ports and Flushing of Stopcock
ing. Perform this conditioning procedure at least one and
preferably two more times.
8.5.1 If conditions warrant, the sample collection tubing
may be removed from the syringe during the time the piston is
depressed. In this case the flow of liquid shall continue and
FIG. 2 Conditioning of Syringe, Stopcock Handle in Line with
should be directed into the flush container. Care shall be taken
Flushing Port
not to contaminate the syringe inlet port.
8.6 Turn the stopcock slowly to open the port to the syringe
apparatus. Properly label and identify the sample(s) before
(Fig. 2 handle in line with the flushing port). Allow 10 mL of
leaving the site or going to the next apparatus. Dispose of any
liquid to enter the syringe. Immediately close the port to the
waste materials in the proper manner.
syringe (Fig. 3 handle toward the tubing).
8.7 With the syringe vertical (Fig. 3), the stopcock handle
8. Collecting Samples from Electrical Apparatus Using
up towards the tubing, eject any air bubbles by carefully
Glass Syringes
depressing the syringe piston far enough to leave 1 mL to 2 mL
8.1 Perform the same steps as described in 7.1 – 7.4. Attach
of liquid in the syringe. If all of the liquid is evacuated from the
the oil-resistant tubing to the syringe as shown in Fig. 1
syringe, there is a greater chance of an air leak. Close the
8.2 Before using a syringe make sure that the stopcock is on
stopcock by moving the stopcock handle toward the syringe.
securely and there is no debris or obstruction in the syringe that
8.8 To eliminate any possibility that air may be entrapped in
would prevent its proper use.
the valve, let the liquid flow through the flushing port before
8.3 The handle of the plastic stopcock always points to the
the valve is turned to allow the syringe to be filled.
closed port leaving the other two ports in open communication
8.9 Open the stopcock (Fig. 2), with the handle in line with
(Fig. 1).
flushing port. Allow the liquid pressure to push the piston back
8.4 Adjust the equipment drain valve or the sample port
until the syringe is filled to approximately 80 % full. Do not
valve for a gentle flow of liquid through the tubing with the
pull the piston manually since this can result in bubble
syringe stopcock open (Fig. 1) to permit flushing of the
formation.
stopcock. Position the handle toward the syringe (see Note 3).
8.10 Close the stopcock (Fig. 4), with the stopcock handle
8.5 Turn the stopcock slowly to communicate with the
toward syringe. Separate the syringe from the tubing and
syringe (Fig. 2, handle in line with the flushing port). Allow the
inspect for gas bubbles. If gas is present, discharge oil with the
liquid to fill the syringe to maximum full mark (shown as 40 in
syringe vertical (stopcock up) and obtain another sample.
Fig. 2). Immediately close the port to the tubing (Fig. 3 handle
8.11 Protect the syringe from sunlight after the sample is
taken.
8.12 If, after a syringe has set for a period of time after the
sample has been collected, and a gas bubble forms in the
syringe, do not release this bubble as it contains gases from the
liquid that have come out of solution but are still considered
part of the sample.
8.13 Close the valve and secure the area as described in 7.7.
9. Collecting Samples from Electrical Apparatus Using
Stainless Steel Cylinder
9.1 Perform the same steps as described in 7.1 – 7.4.
FIG. 3 Ejecting Oil from Syringe, Stopcock Handling Towards
Tubing
toward tubing). Slowly depress the syringe piston (also known
as plunger) until all the liquid is evacuated from the syringe to
the flush container or catch pan completing the first condition- FIG. 4 Oil-Filled Syringe with Handle Towards Syringe
D923 − 15 (2023)
9.2 Hold the steel cylinder in a vertical position. Connect SAMPLING OF CANS, DRUMS, TANK CARS, TANK
the oil-resistant tubing to the lower valve port on the stainless TRUCKS, AND SMALL ELECTRICAL EQUIPMENT
steel cylinder and connect a short piece approximately 60 cm
(24 in.) of clear oil-resistant tubing to the upper valve on the 10. Sampling Using the Dip-Type or Drum Thief Device
steel cylinder as shown in Fig. 5 (see Note 3). (Fig. 6)
9.3 While keeping the cylinder in the vertical position, open
10.1 Sampling Procedure—Close the top hole of the device
the electrical apparatus sampling drain valve or the sample port with the thumb and introduce the lower end into the liquid to
valve. Open the lower valve on the stainless steel cylinder.
be sampled to a depth of approximately 300 mm. Remove the
Direct the short piece of plastic tubing towards the flush oil thumb, allowing the liquid to flow into the device. Again, close
container and open the upper valve on the stainless steel
the upper end with the thumb and withdraw the device, holding
cylinder. With all three valves open and the cylinder held in a it in a nearly horizontal position. Shift the position of the
vertical position (see Fig. 5), flush the cylinder. Two (2) litres device so that the liquid will flow back and forth in the tube,
of liquid should pass through the cylinder into the flush oil
rinsing the inside surface. During this operation, take care to
container. avoid handling any portion of the device that will be immersed
in the liquid to be sampled. Discard the liquid used for rinsing.
9.4 If air bubbles are seen in the plastic tubing, the stainless
With the thumb again covering the top hole of the device, insert
steel cylinder may be tapped lightly or shaken to dislodge any
the lower end into the liquid at an angle so that it will come to
bubbles inside the cylinder. Flushing with the insulating liquid
rest on the bottom of the container at the center. Raise the
should be continued until the flow out of the cylinder is free of
device approximately 3 mm off the bottom and then release the
any bubbles.
thumb (Warning—See end of paragraph.). When the device is
9.5 Tightly close the three valves in the following sequence: filled, replace the thumb quickly, withdraw the device, and,
first close the upper cylinder valve; then the bottom cylinder
placing the tip inside the neck close to the side of the sample
valve; followed by the electrical apparatus drain valve or container, release the thumb and allow the contents to fill the
sample port valve. Remove the sample adapter if used, and container. The free hand may be placed at a point above the
reinstall the security plug with a non-hardening thread sealant.
liquid level to guide the tip of the device to its position on the
sample container. When the container is filled, stop the flow of
9.6 As a final
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