ASTM C335/C335M-23

Standard Test Method for Steady-State Heat Transfer Properties of Pipe Insulation

SIGNIFICANCE AND USE
4.1 As determined by this test method, the pipe insulation lineal thermal resistance or conductance (and, when applicable, the thermal resistivity or conductivity) are means of comparing insulations which include the effects of the insulation and its fit upon the pipe, circumferential and longitudinal jointing, and variations in construction, but do not include the effects of the outer surface resistance or heat transfer coefficient. They are thus appropriate when the insulation outer-surface temperature and the pipe temperature are known or specified. However, since the thermal properties determined by this test method include the effects of fit and jointing, they are not true material properties. Therefore, properties determined by this test method are somewhat different from those obtained on apparently similar material in flat form using the guarded hot plate, Test Method C177, or the heat flow meter apparatus, Test Method C518.  
4.2 The pipe insulation lineal thermal transference incorporates both the effect of the insulation and its fit upon the pipe and also the effect of the surface heat-transfer coefficient. It is appropriate when the ambient conditions and the pipe temperature are known or specified and the thermal effects of the surface are to be included.  
4.3 Because of the test condition requirements prescribed in this test method, recognize that the thermal transfer properties obtained will not necessarily be the value pertaining under all service conditions. As an example, this test method provides that the thermal properties shall be obtained by tests on dry or conditioned specimens, while such conditions are not necessarily realized in service. The results obtained are strictly applicable only for the conditions of test and for the product construction tested, and must not be applied without proper adjustment when the material is used at other conditions, such as mean temperatures that differ appreciably from those of the test. With these quali...
SCOPE
1.1 This test method covers the measurement of the steady-state heat transfer properties of pipe insulations. Specimen types include rigid, flexible, and loose fill; homogeneous and nonhomogeneous; isotropic and nonisotropic; circular or non-circular cross section. Measurement of metallic reflective insulation and mass insulations with metal jackets or other elements of high axial conductance is included; however, additional precautions must be taken and specified special procedures must be followed.  
1.2 The test apparatus for this purpose is a guarded-end or calibrated-end pipe apparatus. The guarded-end apparatus is a primary (or absolute) method. The guarded-end method is comparable, but not identical to ISO 8497. The ISO method does not use the calculation procedure in Practice C1045.  
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.4 When appropriate, or as required by specifications or other test methods, the following thermal transfer properties for the specimen can be calculated from the measured data (see 3.2):  
1.4.1 The pipe insulation lineal thermal resistance and conductance,  
1.4.2 The pipe insulation lineal thermal transference,  
1.4.3 The surface areal resistance and heat transfer coefficient,  
1.4.4 The thermal resistivity and conductivity,  
1.4.5 The areal thermal resistance and conductance, and  
1.4.6 The areal thermal transference.
Note 1: In this test method the preferred resistance, conductance, and transference are the lineal values computed for a unit length of pipe. These must not be confused with the corresponding areal properties computed on a unit area basis which are more applicable to flat slab geometr...

General Information

• Status: Published
• Publication Date: 28-Feb-2023
• ICS: 91.100.60 - Thermal and sound insulating materials
• Technical Committee: C16 - Thermal Insulation
• Drafting Committee: C16.30 - Thermal Measurement

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C335/C335M − 23
Standard Test Method for
1
Steady-State Heat Transfer Properties of Pipe Insulation
This standard is issued under the fixed designation C335/C335M; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
must not be confused with the corresponding areal properties computed on
1. Scope
a unit area basis which are more applicable to flat slab geometry. If these
1.1 This test method covers the measurement of the steady-
areal properties are computed, the area used in their computation must be
state heat transfer properties of pipe insulations. Specimen reported.
NOTE 2—Discussions of the appropriateness of these properties to
types include rigid, flexible, and loose fill; homogeneous and
particular specimens or materials may be found in Test Method C177, Test
nonhomogeneous; isotropic and nonisotropic; circular or non-
2
Method C518, and in the literature (1).
circular cross section. Measurement of metallic reflective
1.5 This test method allows for operation over a wide range
insulation and mass insulations with metal jackets or other
of temperatures. The upper and lower limit of the pipe surface
elements of high axial conductance is included; however,
temperature is determined by the maximum and minimum
additional precautions must be taken and specified special
service temperature of the specimen or of the materials used in
procedures must be followed.
constructing the apparatus. In any case, the apparatus must be
1.2 The test apparatus for this purpose is a guarded-end or
operated such that the temperature difference between the
calibrated-end pipe apparatus. The guarded-end apparatus is a
exposed surface and the ambient is sufficiently large enough to
primary (or absolute) method. The guarded-end method is
provide the precision of measurement desired. Normally the
comparable, but not identical to ISO 8497. The ISO method
apparatus is operated in closely controlled still air ambient
does not use the calculation procedure in Practice C1045.
from 15 to 30°C, but other temperatures, other gases, and other
1.3 The values stated in either SI units or inch-pound units
velocities are acceptable. It is also acceptable to control the
are to be regarded separately as standard. The values stated in
outer specimen surface temperature by the use of a heated or
each system may not be exact equivalents; therefore, each
cooled outer sheath or blanket or by the use of an additional
system shall be used independently of the other. Combining
uniform layer of insulation.
values from the two systems may result in non-conformance
1.6 The use any size or shape of test pipe is allowable
with the standard.
provided that it matches the specimens to be tested. Normally
1.4 When appropriate, or as required by specifications or
the test method is used with circular pipes; however, its use is
other test methods, the following thermal transfer properties
permitted with pipes or ducts of noncircular cross section
for the specimen can be calculated from the measured data (see
(square, rectangular, hexagonal, etc.). One common size used
3.2):
for interlaboratory comparison is a pipe with a circular cross
1.4.1 The pipe insulation lineal thermal resistance and
section of 88.9-mm diameter (standard nominal 80-mm [3-in.]
conductance,
pipe size), although several other sizes are reported in the
1.4.2 The pipe insulation lineal thermal transference,
literature (2-4).
1.4.3 The surface areal resistance and heat transfer
1.7 The test method applies only to test pipes with a
coefficient,
horizontal or vertical axis. For the horizontal axis, the literature
1.4.4 The thermal resistivity and conductivity,
includes using the guarded-end, the calibrated, and the
1.4.5 The areal thermal resistance and conductance, and
calibrated-end cap methods. For the vertical axis, no experi-
1.4.6 The areal thermal transference.
ence has been found to support the use of the calibrated or
NOTE 1—In this test method the preferred resistance, conductance, and calibrated-end methods. Therefore the method is restricted to
transference are the lineal values computed for a unit length of pipe. These
using the guarded-end pipe apparatus for vertical axis mea-
surements.
1
This test method is under the jurisdiction of ASTM Committee C16 on Thermal
1.8 This test method covers two distinctly different types of
Insu
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C335/C335M − 17 C335/C335M − 23
Standard Test Method for
1
Steady-State Heat Transfer Properties of Pipe Insulation
This standard is issued under the fixed designation C335/C335M; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This test method covers the measurement of the steady-state heat transfer properties of pipe insulations. Specimen types
include rigid, flexible, and loose fill; homogeneous and nonhomogeneous; isotropic and nonisotropic; circular or non-circular cross
section. Measurement of metallic reflective insulation and mass insulations with metal jackets or other elements of high axial
conductance is included; however, additional precautions must be taken and specified special procedures must be followed.
1.2 The test apparatus for this purpose is a guarded-end or calibrated-end pipe apparatus. The guarded-end apparatus is a primary
(or absolute) method. The guarded-end method is comparable, but not identical to ISO 8497. The ISO method does not use the
calculation procedure in Practice C1045.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.4 When appropriate, or as required by specifications or other test methods, the following thermal transfer properties for the
specimen can be calculated from the measured data (see 3.2):
1.4.1 The pipe insulation lineal thermal resistance and conductance,
1.4.2 The pipe insulation lineal thermal transference,
1.4.3 The surface areal resistance and heat transfer coefficient,
1.4.4 The thermal resistivity and conductivity,
1.4.5 The areal thermal resistance and conductance, and
1.4.6 The areal thermal transference.
NOTE 1—In this test method the preferred resistance, conductance, and transference are the lineal values computed for a unit length of pipe. These must
not be confused with the corresponding areal properties computed on a unit area basis which are more applicable to flat slab geometry. If these areal
properties are computed, the area used in their computation must be reported.
1
This test method is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
Measurement.
Current edition approved May 1, 2017March 1, 2023. Published October 2017April 2023. Originally approved in 1954. Last previous edition approved in 20102017 as
ε1
C335/C335M – 10C335/C335M – 17. . DOI: 10.1520/C0335_C0335M-17.10.1520/C0335_C0335M-23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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C335/C335M − 23
NOTE 2—Discussions of the appropriateness of these properties to particular specimens or materials may be found in Test Method C177, Test Method
2
C518, and in the literature (1).
1.5 This test method allows for operation over a wide range of temperatures. The upper and lower limit of the pipe surface
temperature is determined by the maximum and minimum service temperature of the specimen or of the materials used in
constructing the apparatus. In any case, the apparatus must be operated such that the temperature difference between the exposed
surface and the ambient is sufficiently large enough to provide the precision of measurement desired. Normally the apparatus is
operated in closely controlled still air ambient from 15 to 30°C, but other temperatures, other gases, and other velocities are
acceptable. It is also acceptable to control the outer specimen surface temperature by the use of a heated or cooled outer sheath
or blanket or by the use of an additional uniform layer of insulation.
1.6 The use any size or shape of test pipe is allowable provided that it matches the specimens to be tested. Normally the test
method is used with circular pipes; however, its use is permitted with pipes or ducts of noncircular cross section (square,
rectangular, hexagonal, etc.). One common size used for interlaboratory comparison i
...