ASTM D831-94(2004)
(Test Method)Standard Test Method for Gas Content of Cable and Capacitor Oils
Standard Test Method for Gas Content of Cable and Capacitor Oils
SIGNIFICANCE AND USE
The gas content of cable and capacitor oils is considered to be important, since the evolution of gas in the form of bubbles can have an adverse effect on the insulating properties of these fluids. It is customary to degas these oils prior to use, and this test method provides a means of determining the gas content before and after degassing.
FIG. 1 Apparatus for Determination of Gas Content of Cable and Capacitor Oils
SCOPE
1.1 This test method covers the determination of the gas content of electrical insulating oils of low and medium viscosities in the general range up to 190 cSt at 104°F (40°C), such as are used in capacitors and paper-insulated electric cables and cable systems of the oil-filled type. The determination of gas content is desirable for any insulating oil having these properties and intended for use in a degassed state.
1.2 The values stated in inch-pound units are to be regarded as the standard. Note 1-For testing insulating oils with viscosities of 19 cSt at 40°C or below, see Test Method D2945.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D831 − 94(Reapproved 2004)
Standard Test Method for
Gas Content of Cable and Capacitor Oils
This standard is issued under the fixed designation D831; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope bubbles can have an adverse effect on the insulating properties
of these fluids. It is customary to degas these oils prior to use,
1.1 This test method covers the determination of the gas
and this test method provides a means of determining the gas
content of electrical insulating oils of low and medium
content before and after degassing.
viscosities in the general range up to 190 cSt at 104°F (40°C),
such as are used in capacitors and paper-insulated electric
5. Apparatus (see Fig. 1)
cables and cable systems of the oil-filled type. The determina-
5.1 Degassing Chamber—Degassing chamber, A, made of
tion of gas content is desirable for any insulating oil having
heat-resistantglass (withcalibratedoilwellatbottom),having
these properties and intended for use in a degassed state.
afixedtotalspacevolumeofabout175to300mL.Theoilwell
NOTE1—Fortestinginsulatingoilswithviscositiesof19cStat40°Cor
below, see Test Method D2945.
shall have a maximum capacity of 50 mL and shall be
calibrated in 0.2-mL divisions.
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
5.2 Stopcocks—Glass stopcocks, B and C, which shall have
responsibility of the user of this standard to establish appro-
large-diameter barrels and a mirror finish to ensure against
priate safety and health practices and determine the applica-
leakage. Use stopcock grease on all stopcocks and ground-
bility of regulatory limitations prior to use.
glass joints.
2. Referenced Documents
5.3 Atomizer—Glass pipet, D, placed to drop oil on the side
of the degassing chamber, or
2.1 ASTM Standards:
5.3.1 FrittedDisk(Alternative)—Capacity30mm,medium-
D2945Test Method for Gas Content of Insulating Oils
porosity.
(Withdrawn 2012)
NOTE 2—Some experience has shown improvement in the atomization
3. Summary of Test Method
process, particularly for oils of medium viscosity above 95 cSt at 40°C, if
3.1 This test method consists essentially of feeding the oil a 30-mm medium-porosity fritted disk is substituted for the pipet.
into an evacuated chamber in such a manner that the oil is
5.4 Pressure Gage—Pressure gage, E, of modified McLeod
thoroughlyexposedtothevacuum,allowingfreeescapeofany
type. Include the volume of this gage in the over-all volume of
dissolvedgas.Fromthevolumeofoiladmittedtothechamber,
the apparatus (Note 3). This is essential and must also include
the temperature, the pressure produced, and volume occupied
the volume of the gage-connecting tubing.
by the released gas, the gas volume under standard conditions
NOTE 3—The volume of the gage may be obtained from the manufac-
of pressure and temperature may be calculated as a percentage
turer or measured.
by volume of oil.
5.5 Oil Trap, F, having a capacity of 250 mL.
4. Significance and Use
5.6 Thermometer, T, room ambient.
4.1 Thegascontentofcableandcapacitoroilsisconsidered
5.7 Cold Trap, J, employed to eliminate possible error due
to be important, since the evolution of gas in the form of
to presence of condensable vapors.
This test method is under the jurisdiction of ASTM Committee D27 on
5.8 Oven, K, employed to enhance the atomization process.
Electrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-
The oven shall enclose the degassing chamber, A, between
mittee D27.03 on Analytical Tests.
stopcocks B and C, and point L. Provide suitable means for
Current edition approved Oct. 1, 2004. Published December 2004. Originally
´1
reading, maintaining, and regulating temperature in a range
approved in 1945. Last previous edition approved in 1994 as D831–94(1999) .
DOI: 10.1520/D0831-94R04.
from 30 to 150°C. Measure temperature by means of a
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
thermocouple fastened to the oil chamber at the 25-mL mark
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and suitably shielded to eliminate radiation errors.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
The last approved version of this historical standard is referenced on
www.astm.org. Borosilicate glass has been found to be satisfactory for this purpose.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D831 − 94 (2004)
consists of a stainless steel cylinder 2 ⁄4 in. (5.7 cm) in inside
diameterand9 ⁄2in.(24cm)inlength,closedatthebottom.An
aluminumpiston,accuratelymachinedforaneasyslidingfit,is
inserted in the bore of the cylinder. Two nipples, diametrically
opposite each other, are inserted at the extreme bottom of the
cylinder. Each nipple has a screw plug at the end with a gasket
for sealing. Make all connections to the measuring equipment
fromthesamplecontainerusingglassormetaltubing.Connect
butted joints using short sections of heavy-walled rubber
tubing. Coat the tubing thoroughly with suitable sealing
compound.Take all samples under slight oil pressure, with the
following sequence of operations: Remove plugs from both
nipples. Push the piston to the extreme bottom of the cylinder.
Hold the cylinder so that the nipples point in a vertical
direction. Using a rubber tube connection, force oil in through
the nipple in the lowest position and flush a few millilitres out
the opposite nipple to remove any trapped air bubbles. Then
insert the plug in the outlet nipple and allow oil to push the
piston up to fill the cylinder. Hold the piston at the top of the
cylinder with one hand and plug the inlet nipple. The alumi-
num piston “floats” on the oil as the level varies due to
temperaturechangesorremovaloftestspecimensandprevents
contamination by absorption and diffusion. Fit the piston
accurately so it moves down freely with decreasing oil level to
FIG. 1 Apparatus for Determination of Gas Content of Cable and prevent voids forming under the piston which would allow
Capacitor Oils
rapid absorption of air by the top oil. Draw the test specimen
continuously from the cylinder, weight the piston to ensure
maintenance of contact with the oil. Wide variations in the
6. Sampling
result are possible in two test specimens from the same source
unlessthegreatestcareistakeninthesamplingprocedure.This
6.1 Whenconvenient,connectthedegassingchamberofthe
phase of the test is so involved with the details of what
measuring equipment directly to the container from which the
constitutes correct practice that ability to procure consistent
oilistobesampled.Thisisusuallynotconvenientandisoften
representative test specimens depends, to a great extent, on
impossible. The method of sampling described in 6.2 is
wide experience. The chief precaution to the procurement of
recommended as an alternative.
representative test specimens involves a complete flushing of
6.2 Use the sample container as shown in Fig. 2, which
all piping and hose between the sample container and sample
source, such as pothead, joint, cable, oil reservoir, etc., imme-
diately preceding collection of the sample. Eliminate all long
sampling pipe lines.After taking the test specimen, ensure that
the piston always remains in contact with the oil prior to and
during withdrawal of the test s
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