ASTM D831-94(1999)e1

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e1
Designation:D 831–94 (Reapproved 1999)
Standard Test Method for
Gas Content of Cable and Capacitor Oils
This standard is issued under the fixed designation D 831; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Editorial changes were made in March 1999.
1. Scope of these fluids. It is customary to degas these oils prior to use,
and this test method provides a means of determining the gas
1.1 This test method covers the determination of the gas
content before and after degassing.
content of electrical insulating oils of low and medium
viscosities in the general range up to 190 cSt at 104°F (40°C),
5. Apparatus (see Fig. 1)
such as are used in capacitors and paper-insulated electric
5.1 Degassing Chamber—Degassing chamber, A, made of
cables and cable systems of the oil-filled type. The determina-
heat-resistant glass (with calibrated oil well at bottom),
tion of gas content is desirable for any insulating oil having
havingafixedtotalspacevolumeofabout175to300mL.The
these properties and intended for use in a degassed state.
oil well shall have a maximum capacity of 50 mLand shall be
NOTE 1—Fortestinginsulatingoilswithviscositiesof19cStat40°Cor
calibrated in 0.2-mL divisions.
below, see Test Method D2945.
5.2 Stopcocks—Glass stopcocks, B and C, which shall have
1.2 This standard does not purport to address all of the
large-diameter barrels and a mirror finish to ensure against
safety concerns, if any, associated with its use. It is the
leakage. Use stopcock grease on all stopcocks and ground-
responsibility of the user of this standard to establish appro-
glass joints.
priate safety and health practices and determine the applica-
5.3 Atomizer—Glass pipet, D, placed to drop oil on the side
bility of regulatory limitations prior to use.
of the degassing chamber, or
5.3.1 Fritted Disk (Alternative)—Capacity 30 mm,
2. Referenced Documents
medium-porosity.
2.1 ASTM Standards:
NOTE 2—Some experience has shown improvement in the atomization
D2945 Test Method for Gas Content of Insulating Oils
process, particularly for oils of medium viscosity above 95 cSt at 40°C, if
a 30-mm medium-porosity fritted disk is substituted for the pipet.
3. Summary of Test Method
5.4 PressureGage—Pressuregage,E,ofmodifiedMcLeod
3.1 This test method consists essentially of feeding the oil
type. Include the volume of this gage in the over-all volume
into an evacuated chamber in such a manner that the oil is
of the apparatus (Note 3). This is essential and must also
thoroughlyexposedtothevacuum,allowingfreeescapeofany
include the volume of the gage-connecting tubing.
dissolvedgas.Fromthevolumeofoiladmittedtothechamber,
the temperature, the pressure produced, and volume occupied
NOTE 3—The volume of the gage may be obtained from the manufac-
by the released gas, the gas volume under standard conditions turer or measured.
of pressure and temperature may be calculated as a percentage
5.5 Oil Trap, F, having a capacity of 250 mL.
by volume of oil.
5.6 Thermometer, T, room ambient.
5.7 Cold Trap, J, employed to eliminate possible error due
4. Significance and Use
to presence of condensable vapors.
4.1 Thegascontentofcableandcapacitoroilsisconsidered
5.8 Oven, K, employed to enhance the atomization process.
to be important, since the evolution of gas in the form of
The oven shall enclose the degassing chamber, A, between
bubbles can have an adverse effect on the insulating properties
stopcocks B and C, and point L. Provide suitable means for
reading, maintaining, and regulating temperature in a range
This test method is under the jurisdiction of ASTM Committee D-27 on
Electrical Insulating Liquids and Gasesand is the direct responsibility of Subcom- Borosilicate glass has been found to be satisfactory for this purpose.
mittee D27.03 on Analytical Tests. A stopcock grease equivalent to No. 15521. A vacuum sealing compound,
Current edition approved July 15, 1994. Published September 1994. Originally Central Scientific Co., Chicago, IL, has been found satisfactory for this purpose.
e1 5
published as D831–45. Last previous edition D831–84(1989) . The Flosdorf modification, manufactured by the F. J. Stokes Co., Philadelphia,
Annual Book of ASTM Standards, Vol 10.03. PA, has been found satisfactory for this purpose.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 831
FIG. 2 Apparatus for Sampling Oils
num piston “floats” on the oil as the level varies due to
temperaturechangesorremovaloftestspecimensandprevents
FIG. 1 Apparatus for Determination of Gas Content of Cable and
contamination by absorption and diffusion. Fit the piston
Capacitor Oils
accurately so it moves down freely with decreasing oil level to
prevent voids forming under the piston which would allow
from 30 to 150°C. Measure temperature by means of a
rapid absorption of air by the top oil. Draw the test specimen
thermocouple fastened to the oil chamber at the 25-mL mark
continuously from the cylinder, weight the piston to ensure
and suitably shielded to eliminate radiation errors. maintenance of contact with the oil. Wide variations in the
result are possible in two test specimens from the same source
6. Sampling
unlessthegreatestcareistakeninthesamplingprocedure.This
phase of the test is so involved with the details of what
6.1 Whenconvenient,connectthedegassingchamberofthe
constitutes correct practice that ability to procure consistent
measuring equipment directly to the container from which the
representative test specimens depends, to a great extent, on
oilistobesampled.Thisisusuallynotconvenientandisoften
wide experience. The chief precaution to the procurement of
impossible. The method of sampling described in 6.2 is
representative test specimens involves a complete flushing of
recommended as an alternative.
all piping and hose between the sample container and sample
6.2 Use the sample container as shown in Fig. 2, which
source, such as pothead, joint, cable, oil reservoir, etc., imme-
consists of a stainless steel cylinder 2 ⁄4 in. (5.7 cm) in inside
diately preceding collection of the sample. Eliminate all long
diameterand9 ⁄2in.(24cm)inlength,closedatthebottom.An
sampling pipe lines.After taking the test specimen, ensure that
aluminumpiston,accuratelymachinedforaneasyslidingfit,is
the piston always remains in contact with the oil prior to and
inserted in the bore of the cylinder. Two nipples, diametrically
during withdrawal of the test specimen.
opposite each other, are inserted at the extreme bottom of the
cylinder. Each nipple has a screw plug at the end with a gasket
7. Calibration of Apparatus
for sealing. Make all connections to the measuring equipment
fromthesamplecontainerusingglassormetaltubing.Connect 7.1 Calibration and conditioning of the apparatus are often
butted joints using short sections of heavy-walled rubber done by the manufacturer. If this has not been done, or if a
tubing. Coat the tubing thoroughly with suitable sealing check is desired, the following procedures may be used:
compound. Take all samples under slight oil pressure, with the 7.1.1 Clean the glass assembly with a cleaning solution,
following sequence
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