ASTM C795-08(2023)
(Specification)Standard Specification for Thermal Insulation for Use in Contact with Austenitic Stainless Steel
Standard Specification for Thermal Insulation for Use in Contact with Austenitic Stainless Steel
ABSTRACT
This specification covers non-metallic thermal insulation for use in contact with austenitic stainless steel piping and equipment. The material shall conform to the established requirements of the basic material specification. The physical and chemical requirements shall conform to the requirements of the basic material specification. Preproduction corrosion test and chemical analysis shall be performed to conform to the specified requirements.
SCOPE
1.1 This specification covers non-metallic thermal insulation for use in contact with austenitic stainless steel piping and equipment. In addition to meeting the requirements specified in their individual material specifications, issued under the jurisdiction of ASTM Committee C16, these insulations must pass the preproduction test requirements of Test Method C692, for stress corrosion effects on austenitic stainless steel, and the confirming quality control, chemical requirements, when tested in accordance with the Test Methods C871.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 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.
General Information
Relations
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: C795 − 08 (Reapproved 2023)
Standard Specification for
Thermal Insulation for Use in Contact with Austenitic
Stainless Steel
This standard is issued under the fixed designation C795; 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 C390 Practice for Sampling and Acceptance of Thermal
Insulation Lots
1.1 This specification covers non-metallic thermal insula-
C692 Test Method for Evaluating the Influence of Thermal
tion for use in contact with austenitic stainless steel piping and
Insulations on External Stress Corrosion Cracking Ten-
equipment. In addition to meeting the requirements specified in
dency of Austenitic Stainless Steel
their individual material specifications, issued under the juris-
C871 Test Methods for Chemical Analysis of Thermal Insu-
diction of ASTM Committee C16, these insulations must pass
lation Materials for Leachable Chloride, Fluoride, Silicate,
the preproduction test requirements of Test Method C692, for
and Sodium Ions
stress corrosion effects on austenitic stainless steel, and the
confirming quality control, chemical requirements, when tested
3. Terminology
in accordance with the Test Methods C871.
3.1 Definitions—Terminology C168 applies to the terms
1.2 The values stated in inch-pound units are to be regarded
used in this specification.
as standard. The values given in parentheses are mathematical
3.2 Definitions of Terms Specific to This Standard:
conversions to SI units that are provided for information only
3.2.1 basic material specification—any of the material
and are not considered standard.
specifications for homogeneous insulation covered in any of
1.3 This standard does not purport to address all of the
the pertinent Annual Book of ASTM Standards.
safety concerns, if any, associated with its use. It is the
3.2.2 lot—a lot shall be defined in accordance with Practice
responsibility of the user of this standard to establish appro-
C390 by agreement between the purchaser and the manufac-
priate safety, health, and environmental practices and deter-
turer.
mine the applicability of regulatory limitations prior to use.
3.2.3 stress corrosion cracking (SCC)—the failure of metal,
1.4 This international standard was developed in accor-
taking the form of cracks that potentially occur under the
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the combined influence of certain corrosive environments and
applied or residual stresses.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.2.4 wicking-type insulation—insulation material that, by
Barriers to Trade (TBT) Committee.
virtue of its physical characteristics, permits a wetting liquid to
infiltrate it by capillary attraction.
2. Referenced Documents
2.1 ASTM Standards:
4. Significance and Use
C168 Terminology Relating to Thermal Insulation
4.1 Stress corrosion cracking of austenitic stainless steel is a
metallurgical phenomenon. One cause of stress corrosion
This specification is under the jurisdiction of ASTM Committee C16 on
cracking is the presence of contaminants in water solution,
Thermal Insulation and is the direct responsibility of Subcommittee C16.20 on
Homogeneous Inorganic Thermal Insulations.
which can be concentrated at the stressed surface by evapora-
Current edition approved May 1, 2023. Published June 2023. Originally
tion of the water.
approved in 1977. Last previous edition approved in 2018 as C795 – 08 (2018).
DOI: 10.1520/C0795-08R23.
4.2 There is an apparent correlation between stress corro-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
sion cracking of austenitic stainless steel and the use of
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
insulation which either contains water-leachable chloride or, by
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. reason of its water absorptivity, acts as a vehicle through which
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C795 − 08 (2023)
FIG. 1 Acceptability of Insulation Material on the Basis of the Plot Points of the (Cl + F) and the (Na + SiO ) Analyses
chlorides from outside the system are concentrated at the 4.5 Research has indicated that in addition to the halide ion
3,4,5
surface of the stainless steel. chloride, fluoride ions have the potential to induce SCC in the
absence of inhibiting ions. Two widely used insulation speci-
4.3 Studies have shown that insulation containing certain
fications that are similar to C795 and are specific to SCC allow
water-soluble compounds have the capacity to retard or prevent
the use of the same Test Methods C692 and C871 for
stress corrosion. Numerous materials thought to inhibit stress
evaluation of insulation materials. Both specifications require
corrosion cracking have been tried with varying degrees of
fluoride ions to be included with chloride ions when evaluating
success. An inhibiting compound commonly used is sodium
the extractable ions and plotting them on the Fig. 1 acceptabil-
silicate. Present knowledge indicates that the sodium silicate
ity graph. Fluoride has been added to chloride in Section 13
dissociates in the presence of water, leaving the silicate ion to
and on Fig. 1 to be consistent with the other standards.
form a protective mechanism that inhibits or prevents the
chloride ion from attacking the stainless steel. Under adverse 4.6 Physical and chemical changes can occur when thermal
environmental conditions, this protective agent will possibly be insulation, various binders, or adhesives, or a combinations
leached from the product with time and permanent protection thereof, are heated. Insulation materials are often exposed to
is not afforded. process temperatures that are sufficient to cause changes.
Various compounds thermally decompose increasing the solu-
4.4 Test Method C692 contains a procedure for determining
bility of some ions that leach out when exposed to water. Other
whether or not stress corrosion cracking will occur with a given
compounds have the potential to become less soluble after
thermal insulation. The procedure is used to evaluate insulation
thermal exposure.
materials have the potential to inhibit, to be passive, or actively
contribute to stress corrosion cracking of austenitic stainless 4.7 The inhibitory qualities of sodium silicate compounds
steels. have been found to be different for different molar ratios of
sodium to silicate. The current specifications treat them as
being added together for a total ppm value.
Schaffer, L. D., and Klapper, J. A., “Investigation of the Effects of Wet,
Chloride-Bearing, Thermal Insulation on Austenitic Stainless Steel,” Report No.
ESI-25-(a)-1, Oak Ridge National Laboratory, and Ebasco Services Inc., November
1, 1961. Whorlow, Kenneth M., Woolridge, Edward and Hutto, Francis B., Jr., “Effect
Dana, A. W., Jr., “Stress-Corrosion Cracking of Insulated A
...
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