ASTM D3277-95
(Test Method)Standard Test Methods for Moisture Content of Oil-Impregnated Cellulosic Insulation
Standard Test Methods for Moisture Content of Oil-Impregnated Cellulosic Insulation
SCOPE
1.1 These test methods cover the determination of the weight percent of water in new or aged, oil-impregnated electrical insulation. These test methods depend on solvent extraction of the water at room temperature. The range from 0.1 to 7.0% water has been explored.
1.2 There are four test methods, A, B, C, and D. Methods A and B for thin paper and dense materials, respectively, are manual methods for solvent extraction of water from the specimens. Titration is used to determine the amount of water. Method C uses automatic titration to determine the amount of water. Method D is a direct automated method for extraction and detection of the water.
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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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
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Designation: D 3277 – 95
Standard Test Methods for
Moisture Content of Oil-Impregnated Cellulosic Insulation
This standard is issued under the fixed designation D 3277; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4.2 When cellulosic insulation such as paper and pressboard
are impregnated with and immersed in oil, there is an inter-
1.1 These test methods cover the determination of the
change of moisture between the cellulose and oil until they
weight percent of water in new or aged, oil-impregnated
attain equilibrium with respect to their relative saturations with
electrical insulation. These test methods depend on solvent
moisture.
extraction of the water at room temperature. The range from
4.3 Considerable care should be taken in using these test
0.1 to 7.0 % water has been explored.
methods to measure the water content of dry (<0.5 %) paper
1.2 There are four test methods,A, B, C, and D. MethodsA
and board. Contamination of material by water from the
and B for thin paper and dense materials, respectively, are
surroundings during sampling and handling may be both rapid
manual methods for solvent extraction of water from the
andsignificantinthecaseofdrytestspecimens.Thisisaneven
specimens. Titration is used to determine the amount of water.
greater concern with cellulose insulation prior to oil impreg-
Method C uses automatic titration to determine the amount of
nation.
water. Method D is a direct automated method for extraction
and detection of the water.
5. Apparatus
1.3 This standard does not purport to address all of the
5.1 Karl Fischer Electrometric Titration Apparatus.
safety concerns, if any, associated with its use. It is the
5.2 Magnetic Stirrer and TFE-Fluorocarbon Coated Stir-
responsibility of the user of this standard to establish appro-
ring Bars.
priate safety and health practices and determine the applica-
5.3 Erlenmeyer Flasks, glass-stoppered, 250-mL.
bility of regulatory limitations prior to use.
5.4 Graduate, glass, 100-mL.
2. Referenced Documents 5.5 Büchner Funnel, small porcelain.
5.6 Micro-Syringe, total capacity 0.2 mL, 0.01-mL divi-
2.1 ASTM Standards:
sions.
D 1533 Test Methods for Water in Insulating Liquids (Karl
5.7 Blender, industrial type.
Fischer Reaction Method)
5.8 Syringe, 10 mL, ground glass.
3. Summary of Test Methods 5.9 Drying Oven,1106 5°C.
5.10 Laboratory Desiccator.
3.1 These test methods depend on solvent extraction of the
5.11 Analytical Balance.
moisture at room temperature and Karl Fischer titration (see
Test Methods D 1533). For paper insulation 0.010 in. (0.25
6. Reagents
mm) thick and less, extraction is accomplished by stirring the
6.1 Karl Fischer Reagent—Commercially available stabi-
solvent with small pieces of insulation. In the special case of
lized solution, diluted from approximately 5 mg of water per 1
dense, thick sections, such as pressboard, the extraction rate is
mL to 2.5 to 3.0 mg of water per 1 mL by adding absolute
increased by delaminating thick sections and pulping the
acetone-free methanol (MethodsAand B). For Methods C and
sample in a blender.
D, prepare commercially available solutions for use in auto-
4. Significance and Use matic titrators in accordance with the manufacturer’s instruc-
tions.
4.1 Moisture has an adverse effect on the dielectric strength,
6.2 Titration Solvent—Mix 2 volumes of acetone-free
dielectric loss, d-c resistivity, and aging characteristics of
methanol and 1 volume of dry chloroform. Keep the solution
oil-impregnated cellulosic insulating materials.
tightly capped to prevent moisture absorption from the atmo-
sphere.
These test methods are under the jurisdiction of ASTM Committee D-27 on
6.3 Purity of Reagents—Use reagent grade chemicals in all
Electrical Insulating Liquids and Gases and are the direct responsibility of
tests. Unless otherwise indicated, it is intended that all reagents
Subcommittee D27.06 on Chemical Test.
shall conform to the Committee on Analytical Reagents of the
Current edition approved June 15, 1995. Published August 1995. Originally
published as D 3277 – 73. Last previous edition D 3277 – 94. American Chemical Society, where such specifications are
Annual Book of ASTM Standards, Vol 10.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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.
D 3277 – 95
available. Other grades may be used, provided that it is first 8.7 Calculate the water equivalent of the Karl Fischer
ascertained that the reagent is of sufficiently high purity to reagent (grams of water per millilitre of Karl Fischer reagent)
permit its use without lessening the accuracy of the determi- bydividingtheweightofwateradded,ingrams,bythevolume
nation. in millilitres of Karl Fischer reagent required for titration of the
added water.
6.4 Methanol, acetone-free with no more than 0.001 %
acetone.
9. Procedure
7. Sampling
9.1 Test MethodA(0.010 in. (0.254 mm) or Thinner Paper):
9.1.1 Proceed in accordance with 8.1.
7.1 The sampling procedure is not defined since it would be
9.1.2 Dry the solvent containing more than 50 ppm of water
different for different apparatus, whether the samples were new
by weight, which may be achieved by numerous techniques.
or aged. Sample storage may also vary depending upon
Onetechniqueistopassthesolventthrougha30by1 ⁄2-in.(76
expected water content and time between sampling and testing.
by4-cm)columncontaining3Amolecularsievedriedat250°C
The assumption is made that the sample is representative of the
under vacuum for at least 4 h. Purging with dry nitrogen
condition the analyst is attempting to assess.
instead of using a vacuum and the use of other temperatures
7.1.1 Dried cellulose absorbs moisture at an extremely fast
can also achieve properly prepared molecular sieve material.
rate. Precautions such as using polyethylene gloves for han-
Regardless of the test method used, test the dried solvent using
dling sample materials, and flushing the sample bottles with
a Karl Fischer apparatus to verify that the water content is less
nitrogen during sampling have been found to be good prac-
than 50 ppm by weight. Store the dried solvent under nitrogen.
tices, especially when testing for low levels of moisture in
9.1.3 Add 100 mL of titration solvent to each of two
cellulose. Drying the sample bottle may cause a slight negative
Erlenmeyer flasks which have previously been pre-dried for a
bias, but this would be expected to be much smaller than the
minimum of 4 h at 125°C. Place a dry TFE-fluorocarbon
positive bias that would occur if moist air were left in a sample
1 5
coated stirring bar (about 1 ⁄2 in. (38 m) long by ⁄16 in. (8 mm)
container. Other practices, such as placing the paper immedi-
in diameter) in each flask.
ately into a bottle containing the oil from the apparatus from
9.1.4 To one flask, add 2 to3gof paper sample to be
which it was taken, leaving little or no air space and a high
1 1
analyzed,cutintostrips ⁄2by1 ⁄2in.(13by38mm)orsmaller.
solid to liquid weight ratio, have been found to preserve the
9.1.5 Insert a stopper in each flask and agitate contents for
water content. The time element during which the paper
40 to 50 min.
sample is exposed to ambient conditions must be minimized
9.1.6 Decant the solvent from the flask containing the paper
and kept under several minutes when low (<1 %) water
strips into the titration chamber of the Karl Fischer apparatus
contents are expected.Another method of preservation that has
and titrate.
been used is to wrap large sections of paper in plastic wrap
9.1.7 Place the paper strips in a weighing dish, dry for at
followed by a layer of foil wrap.
least 4 h at 110°C, cool to room temperature in a desiccator,
andweigh.Thisweight,minusthetare,isthespecimenweight.
8. Standardization of Reagent by Distilled Water (Test
9.1.8 Repeat 9.1.6 for the flask that did not contain any
Methods A and B)
paper. This is the blank.
8.1 Add about 100 mL of solvent (chloroform-methanol) to
9.1.9 Determine percent weight of water in the paper as
the clean titration flask. Turn on the indicating circuit and
follows:
magnetic stirrer and adjust the potentiometer to maximum
Water, wt % 5 [~F! 3 100]/W (1)
deflection. (Check the battery every day.) Then add the Karl
Fischer reagent in large amounts to neutralize the water present
where:
in the solvent. At first the needle will deflect due to local
1.03 = correction factor for the loss of solvent during this
concentrations of the unreacted reagent about the electrodes,
analytical procedure due to adsorption of solvent
but will fall back to near the original position.As the end point
into the paper,
isreached,theneedlewillfallbackmoreandmoreslowlyafter
V = Karl Fischer reagent required for titration of the
each addition of Karl Fischer reagent. The end point is reached
solvent from the flask containing the paper strips,
when, after addition of a single drop of reagent, the needle
mL,
remains at rest near the position of maximum deflection for 30
V = Karl Fischer reagent required for titration of the
s.
solvent from the flask containing no paper, mL,
8.2 Partially fill a small-volume syringe (such as a Gilmont
F = water equivalent of the Karl Fischer reagent (grams
micrometer syringe of 0.2-mL capacity) with distilled water.
of water per millilitre of Karl Fischer reagent), and
8.3 Weigh the syringe and its contents to the nearest 0.1 mg
W = specimen weight, g.
on an analytical balance.
9.1.10 Standardize the Karl Fischer reagent daily in accor-
8.4 Deliver from 0.03 to 0.05 mL of water into the neutral-
dance with Section 8.
ized solvent. 9.2 TestMethodB(DenseCellulosicMaterialsThickerthan
8.5 Reweigh the syringe to determine the exact weight of
0.010 in. (0.254 mm)):
water added to the neutralized titration solvent. 9.2.1 P
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