ASTM D295-99
(Test Method)Standard Test Methods for Varnished Cotton Fabrics Used for Electrical Insulation
Standard Test Methods for Varnished Cotton Fabrics Used for Electrical Insulation
SCOPE
1.1 These test methods cover procedures for the testing of varnished cotton fabrics and varnished cotton fabric tapes (Note 1) to be used as electrical insulation and are directly applicable to both "straight-cut" and "bias-cut" materials, unless otherwise stated in the test method. Note 1-Methods of testing varnished glass fabrics and tapes are given in Test Methods D902.
1.2 The procedures appear in the following order: ASTM Test Procedures Sections Methods Breaking Strength 20 to 27 ... Conditioning 4 ... Dielectric Breakdown Voltage 44 to 47 D 149 Dielectric Breakdown Voltage Under Elongation 48 to 54 D 149 Dissipation Factor and Permittivity 55 to 61 D 150 Elongation 35 to 43 ... Resistance to Oil 69 to 75 D 92 Selection of Test Specimens 3 ... Tear Resistance 28 to 34 D 689 Thickness 5 to 9 D 374 Thread Count 15 to 19 ... Volume Resistance 62 to 68 D 257 Weight 10 to 14 ...
1.3 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of inch-pound units may be approximate.
1.4 This standard does not purport to address all of the safety problems, 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. For specific precautionary statements, see 45.4, 52.1, 59.1, and 66.1.
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An American National Standard
Designation:D295–99
Standard Test Methods for
Varnished Cotton Fabrics Used for Electrical Insulation
This standard is issued under the fixed designation D 295; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope D 92 Test Method for Flash and Fire Points by Cleveland
Open Cup
1.1 These test methods cover procedures for the testing of
D 149 Test Method for Dielectric Breakdown Voltage and
varnished cotton fabrics and varnished cotton fabric tapes
Dielectric Strength of Electrical Insulating Materials at
(Note 1) to be used as electrical insulation and are directly
Commercial Power Frequencies
applicable to both “straight-cut” and “bias-cut” materials,
D 150 Test Methods for AC Loss Characteristics and Per-
unless otherwise stated in the test method.
mittivity (Dielectric Constant) of Solid Electrical Insula-
NOTE 1—Methods of testing varnished glass fabrics and tapes are given 3
tion
in Test Methods D 902.
D 257 Test Methods for DC Resistance or Conductance of
1.2 The procedures appear in the following order:
Insulating Materials
ASTM Test
D 374 Test Methods for Thickness of Solid Electrical Insu-
Procedures Sections Methods
lation
Breaking Strength 20 to 27 .
D 689 Test Method for Internal Tearing Resistance of Pa-
Conditioning 5 .
Dielectric Breakdown Voltage 43 to 46 D 149
per
Dielectric Breakdown Voltage Under Elongation 47 to 53 D 149
D 902 Test Methods for Flexible Resin-Coated Glass Fab-
Dissipation Factor and Permittivity 54 to 60 D 150
rics and Glass Fabric Tapes Used for Electrical Insulation
Elongation 35 to 42 .
Resistance to Oil 68 to 73 D92
D 1711 Terminology Relating to Electrical Insulation
Selection of Test Specimens 4 .
2.2 IEC Standard:
Tear Resistance 28 to 34 D 689
IEC 60394–2 Varnished Fabrics for Electrical Purposes —
Thickness 6 to 10 D 374
Thread Count 15 to 19 .
Part 2: Methods of Test
Volume Resistance 61 to 67 D 257
Weight 11 to 14 .
3. Terminology
1.3 The values stated in inch-pound units are to be regarded
3.1 Definitions: For definitions of terms used in these test
as the standard. The metric equivalents of inch-pound units
methods refer to Terminology D 1711.
may be approximate.
3.2 Definitions of Terms Specific to This Standard:
1.4 This standard does not purport to address all of the
3.2.1 weight—of varnished cloth and varnished cloth tapes,
safety concerns, if any, associated with its use. It is the
the weight per unit area as determined in accordance with this
responsibility of the user of this standard to establish appro-
test method. It is usually expressed in pound per square yard
priate safety and health practices and determine the applica-
for a specified nominal thickness.
bility of regulatory limitations prior to use. For specific
3.2.2 threads per inch—of varnished cloths,thecountofthe
precautionary statements, see 44.4, 51.1, 58.1, and 65.1.
number of warp and filling yarns present in the base cloth per
linear inch of width or length, respectively.
NOTE 2—This standard resembles IEC 60394–2 in title only. The
3.2.3 elongation—the amount of strain observed in a given
content is significantly different.
length of varnished cloth or tape when subjected to prescribed
2. Referenced Documents
loading conditions at prescribed atmospheric conditions. It is
2.1 ASTM Standards: expressed as a percentage of the initial length.
1 2
These test methods are under the jurisdiction of ASTM Committee D-9 on Annual Book of ASTM Standards, Vol 05.01.
Electrical and Electronic Insulating Materials and are the direct responsibility of Annual Book of ASTM Standards, Vol 10.01.
Subcommittee D09.07 on Flexible and Rigid Insulating Materials. Annual Book of ASTM Standards, Vol 15.09.
Current edition approved Oct. 10, 1999. Published November 1999. Originally Available from American National Standards Institute, 11 W 42nd St.,New
published as D 295 – 28 T. Last previous edition D 295 – 94. York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D295–99
3.2.4 oil resistance—of varnished cloth or tape, the ability thickness values are essential because of the importance of
of the varnish film to withstand the attack of oil without space factor in designing electrical equipment.
excessive impairment of its physical and electrical character-
istics when the varnished cloth or tape is immersed in a 7. Test Specimens
specified oil for a prescribed period of time at a given
7.1 In the case of cloths or sheets, cut test specimens 1 in.
temperature.
(25.4 mm) wide across the entire width. In the case of bias-cut
cloth, exclude seams or jointed selvages from the area of test.
4. Selection of Test Specimens
7.2 In the case of tapes or strips, remove specimens 36 in.
4.1 Select specimens for test from portions of material free
(910 mm) long from the sample of material selected in
from defects.
accordance with Section 4.
4.2 In the case of rolls of material other than those packed
in oil, remove the outer two layers of cloth or the outer six
8. Procedure
layers of tape and prepare test specimens from the remaining
8.1 Measure the thickness in accordance with Test Methods
material. In the case of oil-packed tape, remove the outer layer
D 374, with the following modifications:
from each roll to be tested. In the case of sheets and tape strips,
8.1.1 Either Method B or Method C may be used but
remove the outer six layers of material and prepare test
Method C is to be used unless otherwise specified. Method A
specimens from that remaining.
shall not be used.
NOTE 3—In the case of bias-cut materials, exclude seams and jointed 8.1.2 In making thickness measurements, use only one layer
selvage from test areas.
of material.
NOTE 4—If it is desired to test seams and jointed selvages for breaking
8.1.3 In the case of cloths, take ten measurements equally
strength, prepare additional test specimens so that the seams or joints are
spaced across the width of the specimen. The thickness of the
in the center of the specimens.
cloth shall be the average of the ten measurements.
8.1.4 In the case of tapes, unless otherwise specified, take
5. Conditioning
ten measurements equally spaced along the length of each
5.1 Significance and Use—Because the physical and elec-
specimen. The thickness of the tape shall be the average of ten
trical properties of most fabrics change with variation of their
measurements.
moisture content, it is necessary to control this property at the
time of testing in order to attain reasonably good reproducibil-
9. Report
ity of test values. For example, when cotton fabric absorbs
9.1 Report the average, maximum, and minimum thickness
moisture it tends to swell and increase in dimensions.Also, the
in inches (or centimetres).
flexibility, elongation, and tensile strength of the material
normally increase with increased relative humidity, whereas,
10. Precision and Bias
conversely, the electrical properties are depreciated when the
material is subjected to these conditions. The time of exposure
10.1 Thistestmethodhasbeeninuseformanyyears,butno
to the conditioned atmosphere must be long enough to permit
information has been presented to ASTM upon which to base
the moisture content of the test specimen to reach a relatively
a statement of precision. No activity has been planned to
stable value. If the fabric is untreated, a few hours exposure is
develop such information.
sufficient. Treated fabrics like varnished cloth require appre-
10.2 This test method has no bias because the value for
ciably longer time.
thickness is determined solely in terms of this test method
5.2 Where it is desired to test in a controlled atmosphere,
itself.
condition the test specimens for 48 h in the Standard Labora-
tory Atmosphere of 50 6 2 % relative humidity at 23 6 1°C
WEIGHT
(73.4 6 1.8°F). If a conditioning cabinet or chamber is used,
subject the specimens to test immediately upon withdrawal
11. Significance and Use
from the cabinet or chamber, unless otherwise specified.
11.1 Weight values are useful for estimating weight in
5.3 If it is desired to test the material in the condition as
designing electrical equipment containing a constituent part of
received by the purchaser, allow the packages containing the
varnished cloth or tape.
rolls of material from which the specimens are to be taken to
reach room temperature before opening. Open the packages,
12. Procedure
remove the roll and immediately prepare such test specimens
12.1 Prepare either square or rectangular specimens of
as required, unless otherwise specified.
sufficient size to weigh not less than 0.18 oz (5 g). Accurately
5.4 In the case of dispute, the procedure described in 5.2
weigh on an analytical balance. Measure the length and width
shall be the referee method.
dimensions with sufficient precision to be able to compute the
area within 0.3 %. Compute the weight per unit area.
THICKNESS
6. Significance and Use 13. Report
6.1 The thickness test is necessary to determine whether the 13.1 Report a description of the material and the weight in
material meets specified tolerances for thickness. In addition, pounds per square yard or kilograms per square metre.
D295–99
14. Precision and Bias BREAKING STRENGTH
14.1 Thistestmethodhasbeeninuseformanyyears,butno
20. Significance and Use
information has been presented to ASTM upon which to base
20.1 The breaking strength of finished cloth and tape is of
a statement of precision. No activity has been planned to
importance as a measure of its ability to withstand reasonable
develop such information.
pulling without failure while being applied.
14.2 This test method has no bias because the value for
weight per unit area is determined solely in terms of this test
21. Apparatus
method itself.
21.1 Testing machines of the dead-weight pendulum or of
the constant-rate-of-elongation types shall be used, the latter
THREAD COUNT
being preferred.
21.2 The machine shall be graduated to read 0.5 kg or 1 lb,
15. Terminology
or less per scale division for testing specimens breaking at 50
15.1 Definitions of Terms Specific to This Standard:
lb (22.7 kg) or over, and to 0.25 kg, or 0.5 lb, or less for testing
15.1.1 threads per inch—of varnished cloths, the count of specimens breaking under 50 lb.
the number of warp and filling yarns present in the base cloth
22. Test Specimens
per linear inch of width or length, respectively.
22.1 Cut test specimens 1 in. (25.4 mm) in width and not
16. Significance and Use less than 12 in. (305 mm) in length from full-width cloth or
from tapes over 1 in. (25.4 mm) in width. In the case of tapes
16.1 Thread count, together with the weight and width of
having a nominal width of 1 in. (25.4 mm) or less, prepare test
thecloth,isacceptedasthecommonmeansfordesignatingand
specimensnotlessthan12in.(305mm)longusingtheoriginal
identifying cloth constructions.
width.
16.2 Certain of the physical and electrical properties of
wovenfabricsaredependentonthreadcount.Thatis,assuming
NOTE 7—If it is desired to test the seams or jointed selvages of bias-cut
materials for breaking strength, mount specimens obtained as described in
the same size of yarn, an increase in thread count increases the
Note 4, (4.2) in the testing machine so that the seams or jointed selvages
weight, breaking strength, and density of the cloth. Also, the
are midway between the two jaws.
dielectric breakdown voltage and the dissipation factor of the
varnished fabric may be changed by altering the thread count
23. Number of Specimens
of the cloth.
23.1 In the case of straight-cut cloths, cut five specimens in
the direction of the warp threads and five in the direction of the
17. Procedure
filling threads from samples selected in accordance with 4.1
17.1 Determine separately the warp and filling threads per
and 4.2.
inch of cloth by counting in a space of not less than 1 in. (25.4
23.2 In the case of bias-cut cloths, cut five specimens in the
mm) in at least five different places on the specimen. The
direction of the length from samples selected in accordance
average of the five determinations shall be the thread count.
with 4.1 and 4.2.
23.3 In the case of tapes, cut five specimens from each roll
18. Report
selected in accordance with 4.1 and 4.2.
18.1 Report the warp count and the filling count separately
24. Conditioning
as threads per inch (or millimetre).
24.1 Condition specimens in accordance with Section 5.
NOTE 5—The warp threads in straight-cut materials are the threads that
are parallel with the length or machine-direction dimension, while in
25. Procedure
bias-cut materials the warp threads are parallel with the seams or jointed
25.1 Adjust the clearance distance between jaws to be 6 in.
selvages.
(150 mm).
NOTE 6—Beforecountingblackvarnishedmaterialsitwillbenecessary
25.2 Select the rate of travel of the movable jaw to be
to remove the varnish film with a knife blade or other suitable instrument.
constant and preferably 12 in. (305 mm)/min, but it may be
Liquid varnish removers are unsuitable for this purpose as they may cause
aswellingofthefibersandashrinkageofclothwithaconsequentincrease within the limits of 11 and 13 in. (280 and 330 mm)/min,
in threads per inch count; therefore, the films must be removed mechani-
provided it is constant.
cally.
25.3 Reject all readings obtained when the specimens break
at or in the jaws.
19. Precision and Bias
26. Report
19.1 Thistestmethodhasbeeninuseformanyyears,butno
information has been presented to ASTM upon which to base
26.1 Report the following information:
a statement of precision. No activity has been planned to
26.1.1 The average, maximum, and minimum breaking
develop such information.
loads in kilograms or pounds, together with the width of the
19.2 This test method has no bias because the value for specimens and the nominal thickness, and
thread count is determined solely in terms of this test method 26.1.2 The relative humidity and temperature during the
itself. conditioning period, and at the time of the test.
D295–99
26.2 In the case of straight-cut cloths, report the breaking 33. Report
strength of the warp threads and the filling threads separately.
33.1 Report the following:
33.1.1 The average, minimum, and maximum tear resis-
27. Precision and Bias
tance in grams, separately for warp and filler threads,
27.
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