ASTM D348-00
(Test Method)Standard Test Methods for Rigid Tubes Used for Electrical Insulation
Standard Test Methods for Rigid Tubes Used for Electrical Insulation
SCOPE
1.1 These test methods cover the testing of rigid tubes used in electrical insulation. These tubes include many types made from fibrous sheets of basic materials, such as cellulose, asbestos, glass, or nylon, in the form of paper, woven fabrics, or mats, bonded together by natural or synthetic resins or by adhesives. Such tubes include vulcanized fiber and thermosetting laminates, as well as tubes made from cast, molded, or extruded natural or synthetic resins, with or without fillers or reinforcing materials.
1.2 Tubes tested by these test methods are most commonly circular in cross-section; however, non-circular shapes are also in commercial use. To the extent that the individual methods are compatible with a particular non-circular shape, these test methods are applicable to these other shapes. For tests on non-circular tubes, appropriate comments should be included in the test report, including details of orientation of test specimens with respect to the cross-section of the tube.
1.3 The procedures appear in the following sections: ASTM Method Procedure Sections Reference Compressive Strength (Axial and Diametral) 11 to 16 E4 Conditioning 3 ... Density 19 to 23 ... Dielectric Strength 24 to 31 D 149 Dimensional Measurements 4 D 668 Dissipation Factor and Permitivity 32 to 34 D 150 Tensile Strength 5 to 10 E 4 Water Absorption 17 to 18 D 570
1.4 The values stated in inch-pound units are to be regarded as the standard.
1.5 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. For a specific hazard statement, see 25.1.1.
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An American National Standard
Designation:D348–00
Standard Test Methods for
Rigid Tubes Used for Electrical Insulation
This standard is issued under the fixed designation D 348; 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 2. Referenced Documents
1.1 These test methods cover the testing of rigid tubes used 2.1 ASTM Standards:
in electrical insulation. These tubes include many types made D 149 Test Method for Dielectric Breakdown Voltage and
from fibrous sheets of basic materials, such as cellulose, Dielectric Strength of Solid Electrical Insulating Materials
asbestos, glass, or nylon, in the form of paper, woven fabrics, at Commercial Power Frequencies
or mats, bonded together by natural or synthetic resins or by D 150 Test Methods for A-C Loss Characteristics and
adhesives. Such tubes include vulcanized fiber and thermoset- Permittivity (Dielectric Constant) of Solid Electrical Insu-
ting laminates, as well as tubes made from cast, molded, or lating Materials
extruded natural or synthetic resins, with or without fillers or D 570 Test Method for Water Absorption of Plastics
reinforcing materials. D 668 Test Methods for Measuring Dimensions of Rigid
1.2 Tubes tested by these test methods are most commonly Rods and Tubes Used for Electrical Insulation
circular in cross section; however, noncircular shapes are also D 1711 Terminology Relating to Electrical Insulation
in commercial use. To the extent that the individual methods E 4 Practices for Force Verification of Testing Machines
are compatible with a particular noncircular shape, these test
3. Terminology
methods are applicable to these other shapes. For tests on
noncircular tubes, appropriate comments should be included in 3.1 Definitions— For definitions of terms used in these test
methods, refer to Terminology D 1711.
thetestreport,includingdetailsoforientationoftestspecimens
with respect to the cross section of the tube.
4. Conditioning
1.3 The procedures appear in the following sections:
4.1 In order to eliminate the effects of previous history of
ASTM Test
Method
humidity exposure and to obtain reproducible results (Note 1),
Procedure Sections Reference
the test specimens in all cases of dispute, shall be given a
conditioning treatment for physical tests (Note 2) as follows:
Compressive Strength (Axial and Diametral) 12 to 17 E 4
Conditioning. 4 .
4.1.1 Tensile Strength, Compressive Strength (Axial and
Density 20 to 24 .
Diametral), and Density—Condition the machined specimens
Dielectric Strength 25 to 32 D 149
prior to test by drying in an air-circulating oven for 48 h at 50
Dimensional Measurements 5 D 668
Dissipation Factor and Permittivity 33 to 35 D 150
6 3°C, followed by cooling to room temperature in a desic-
Tensile Strength 6 to 11 E 4
cator. In either case, all specimens shall be tested at room
Water Absorption 18 to 19 D 570
temperature maintained at 23 6 2°C, 50 % relative humidity.
1.4 The values stated in inch-pound units are to be regarded
NOTE 1—Conditioning of specimens may be undertaken: (a) for the
as the standard. SI units in parentheses are for information
purpose of bringing the material into equilibrium with standard laboratory
only.
atmospheric conditions of 23°C and 50 % relative humidity; (b) simply to
1.5 This standard does not purport to address all of the
obtain reproducible results, irrespective of previous history of exposure;
safety concerns, if any, associated with its use. It is the
or (c) to subject the material to abnormal conditions of temperature or
responsibility of the user of this standard to establish appro-
humidity in order to predict its service behavior.
The conditions given here to obtain reproducible results may give
priate safety and health practices and determine the applica-
physical values somewhat higher or somewhat lower than values under
bility of regulatory limitations prior to use. For a specific
equilibrium at normal conditions, depending upon the particular material
hazard statement, see 27.1.1.
and test. To ensure substantial equilibrium under normal conditions of
humidity and temperature, however, will require from 20 to 100 days or
These test methods are under the jurisdiction of ASTM Committee D09 on
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 08.01.
Current edition approved Apr. 10, 2000. Published June 2000. Originally
Annual Book of ASTM Standards, Vol 03.01.
published as D 348 – 32T. Last previous edition D 348 – 95.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D348
more depending upon thickness and type of material and its previous
history. Consequently, conditioning for reproducibility must of necessity
be used for general purchase specifications and product control tests.
NOTE 2—Conditioning of specimens for electrical tests is also neces-
sary to obtain consistent results. In order to secure comparative results,
specimens should be conditioned at the same temperature and humidity.
5. Dimensional Measurements
5.1 Dimensional measurements of tube shall be made in
accordance with Test Methods D 668.
TENSILE STRENGTH
6. Significance and Use
6.1 Tension tests, properly interpreted, provide informa-tion
with regard to the tensile properties of rigid tubing, when
employed under conditions approximating those under which
the tests are made. The tensile strength values may vary with
the size of the tube and with the temperature and atmospheric
conditions. Tension tests may provide data for research and
development and for engineering design, and are useful for
quality control purposes.
7. Apparatus
7.1 Any universal testing machine may be used provided it
is accurate to 1 % of the lowest breaking load to be applied.
Jaws that tighten under load, such as wedge-grip jaws, shall be
FIG. 1 Diagram Showing Location of Tube Tension Test
used with the specimen properly aligned.
Specimen in Testing Machine
7.2 The machine shall be verified in accordance with
Practices E 4.
10.1.1 The average inside and outside diameters of the
8. Test Specimens
specimen expressed to the nearest 0.001 in. (0.03 mm), each
8.1 The test specimens shall be as shown in Fig. 1. The
determined from at least two measurements 90° apart,
length, L, shall be as shown in Table 1. A groove shall be
10.1.2 The average outside diameter of the reduced section
machinedaroundtheoutsideofthespecimenatthecenterofits
expressed to the nearest 0.001 in. (0.03 mm),
length so that the wall section after machining shall be 60 % of
10.1.3 The full wall thickness of the specimen,
the original nominal wall thickness. This groove shall consist
2 2
10.1.4 The net area of the test section, in. or mm ,
of a straight section 2.25 in. (57 mm) in length with a radius of
10.1.5 The breaking load of each specimen, lbf or N,
3 in. (76 mm) at each end joining it to the outside diameter.
10.1.6 The tensile strength of each specimen, psi or MPa,
Steel or brass plugs having diameters such that they will fit
and
snugly inside the tube, and having a length equal to the full jaw
10.1.7 The room temperature.
length plus 1 in. (25 mm) shall be placed in the ends of the
specimen to prevent crushing. They can be located in the tube
11. Precision and Bias
conveniently by separating and supporting them on a threaded
11.1 Precision—This test method has been in use for many
metal rod. Details of plugs and test assembly are shown in Fig.
years, but no information has been presented to ASTM upon
1.
which to base a statement of precision. No activity has been
9. Procedure
planned to develop such information.
11.2 Bias—This test method has no bias because the value
9.1 Test five specimens. Measure the average inside and
for tensile strength is determined solely in terms of this test
outside diameters, determined from at least two measurements
method.
90° apart, at the groove to the nearest 0.001 in. (0.03 mm) and
calculate the cross-sectional area from these dimensions. As-
COMPRESSIVE STRENGTH (AXIAL AND
semble the metal plugs with the tube as shown in Fig. 1. Grasp
DIAMETRAL)
this assembly in the V-notched jaws of the testing machine.
9.2 Speed of Testing—The crosshead speed of the testing
12. Significance and Use
machine shall be such that the load can be accurately weighed,
12.1 Compressive tests, properly interpreted, provide infor-
but shall not exceed 0.05 in./min (1.3 mm/min) when the
mation with regard to the compressive properties of rigid
machine is running idle.
tubing when employed under conditions approximating those
10. Report
under which the tests are made. The compressive strength
10.1 Report the following information: values may vary with the size of the tube, and with temperature
D348
TABLE 1 Dimensions of Tension Specimens, in. (mm)
Total Calculated Minimum Length of Standard Length, L, of Specimen to
Nominal Wall Thickness Length of Radial Sections, 2R.S.
1 A
Specimen be Used for 3 ⁄2-in. (89-mm) Jaws
⁄32 (0.79) 0.547 (13.9) 13.80 (350.0) 15 (381.0)
⁄64 (1.2) 0.670 (17.0) 13.92 (354.0) 15 (381.0)
⁄16 (1.6) 0.773 (19.6) 14.02 (356.0) 15 (381.0)
⁄32 (2.4) 0.946 (24.0) 14.20 (361.0) 15 (381.0)
⁄8 (3.2) 1.091 (27.7) 14.34 (364.0) 15 (381.0)
⁄16 (4.8) 1.333 (33.9) 14.58 (370.0) 15 (381.0)
⁄4 (6.4) 1.536 (39.0) 14.79 (376.0) 15.75 (400.0)
⁄16 (7.9) 1.714 (43.5) 14.96 (380.0) 15.75 (400.0)
⁄8 (9.5) 1.873 (47.6) 15.12 (384.0) 15.75 (400.0)
⁄16 (11.1) 2.019 (51.3) 15.27 (388.0) 15.75 (400.0)
⁄2 (12.7) 2.154 (54.7) 15.40 (391.0) 16.5 (419.0)
A
For other jaws greater than 3 ⁄2 in. (89 mm), the standard length shall be increased by twice the length of the jaws minus 7 in. (178 mm). The standard length permits
1 1
a slippage of approximately ⁄4to ⁄2 in. (6.4 to 12.7 mm) in each jaw while maintaining maximum length of jaw grip.
and atmospheric conditions. Compression tests may provide machine is running idle. In cases of diametral loading of
data for research and development, engineering design, quality certain tubing, especially the larger diameter tubes, it may be
control, and acceptance or rejection under specifications. necessary to operate the crosshead at a speed of loading greater
than 0.050 in./min. In this event the speed should be stated in
13. Apparatus
the report.
13.1 Any universal testing machine may be used provided it
16. Report
is accurate to 1 % of the lowest breaking load to be applied, in
16.1 Report the following information:
accordance with Practices E 4. One end of the specimen for
16.1.1 The average inside and outside diameters of the
axial loading or the side of the specimen for diametral loading
specimen expressed to the nearest 0.001 in. (0.03 mm), each
shall bear upon an accurately centered spherical bearing block,
determined from at least two measurements 90° apart,
located whenever practicable at the top. The metal bearing
16.1.2 The average wall thickness of the specimen ex-
plates shall be directly in contact with the test specimen.
pressed to the nearest 0.001 in. (0.03 mm),
NOTE 3—Off-center loading of the diametral compressive test may
16.1.3 The segment length, if segmental specimens are used
cause the tube to push to one side.
for axial tests,
16.1.4 The direction of application of the load,
14. Test Specimens
16.1.5 Theloadoneachspecimenatthefirstsignofrupture,
14.1 Unless otherwise specified, the material shall be tested
lbf or N, and
in the as-received condition.
16.1.6 The ultimate compressive strength in force per unit
14.2 Test specimens shall consist of 1-in. (25-mm) long
area for axial loading and force for diametral loading.
sections of the tubing.
14.3 Care shall be taken in cutting the test specimens for the
17. Precision and Bias
axialtests,tohavetheendsofthespecimenscutaccuratelyand
17.1 Precision—Same as 11.1.
smoothly at right angles to the axis of the tube.
17.2 Bias—Same as 11.2 except for the property of com-
NOTE 4—Ifthetubingistoolargeindiameter,oristoohighinbreaking pressive strength.
strength to be tested with the available testing equipment, a segment of the
WATER ABSORPTION
test specimen specified in 14.2 and 14.3 may be substituted for axial tests.
Such segments should not be used for testing tubes less than 2 in. (51 mm)
18. Significance and Use
in outside diameter. Unless otherwise specified, use segments having a
circumferential length of 2 in. (51 mm).
18.1 The moisture content of a rigid tube has a definite
influence on the electrical properties, as well as on mechanical
15. Procedure
strength, dimensional stability, and appearance. The effect
15.1 Test five specimens axially, with the load applied
upon these properties of changes in moisture content, due to
perpendicular to the faces or ends of the specimen, or test five
water absorption, depends largely upon the inherent properties
specimens diametrically, with the load applied perpendicular to
of the rigid tube. The rate of water absorption may be widely
the tangent at point of application.
different through each edge and surface. A water absorption
15.2 Discard specimens that break at some obvious fortu-
determination will provide data useful for research and devel-
itousflawandretest,unlesssuchflawsconstituteavariable,the
opment, engineering design, quality control, and acceptance or
effect of which it is desired to study.
rejection under specifications.
15.3 Retain results (on specimens) that deviate markedly
19. Procedure
fromthemeanvalueofalltestsunless15.2applies.Inthiscase
run additional tests, the exact number to be fixed by the desired 19.1 Determine and report the rate of water absorption in
(statistical) significance level. accordance with Test Method D 570, immersing specimens for
15.4 Speed of Testing—The crosshead speed of the testing 24 h in distilled water at 23°C after preliminary conditioning
machine shall be 0.050 in./min (1.3 mm/min) when the for1hat 105°C.
D348
19.2 Forsometypesofmaterials,orforspecialapplications, to testing. After removal from the oven, specimens shall be
it may be desirable to employ longer periods of water immer- permitted to cool to room temperature in a desiccator over
sion in order to evaluate performance. In these cases, the report anhydrous CaCl .
shall indicate the exact conditioning procedure. 26.2 In the case of tubes to be used at
...
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