ASTM C692-08e1
(Test Method)Standard Test Method for Evaluating the Influence of Thermal Insulations on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel
Standard Test Method for Evaluating the Influence of Thermal Insulations on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel
SIGNIFICANCE AND USE
An inherent characteristic of some alloys of austenitic stainless steel is their tendency to crack at stress points when exposed to certain corrosive environments. The mechanisms of ESCC are complex and not completely understood but are apparently related to certain metallurgical properties. Chloride ions concentrated at a stress point will catalyze crack formation. It has been reported that other halide ions do not promote ESCC to the same degree as does chloride using the test technology of Test Method C692 (drip test).
Chlorides are common to many environments, so great care shall be taken to protect austenitic stainless steel from chloride contamination.
Most thermal insulations will not, of themselves, cause stress corrosion cracking as shown by qualification tests. When exposed to elevated-temperature (boiling point range), environments containing chlorides, moisture, and oxygen, however, some insulation systems act as collecting media, transmigrating and concentrating chlorides on heated stainless steel surfaces. If moisture is not present, the chloride salts cannot migrate, and stress corrosion cracking because of chloride-contaminated insulation cannot take place.
Insulation materials are available that are specially formulated to inhibit stress corrosion cracking in the presence of chlorides through modifications in basic composition or incorporation of certain chemical additives.
The ability of the 28-day test to measure the corrosion potential of insulation materials is documented by Karnes, whose data appear to have been used for construction of the acceptability curve used in Specification C795 and other specifications.
The metal for all of the coupons used in this test method (C692) shall be qualified (see Section 14) to ascertain that under conditions of the test, chloride ions will cause the metal to crack, and deionized water alone will not cause cracks.
SCOPE
1.1 This test method covers two procedures for the laboratory evaluation of thermal insulation materials to determine whether they contribute to external stress corrosion cracking (ESCC) of austenitic stainless steel due to soluble chlorides within the insulation. This laboratory procedure is not intended to cover all of the possible field conditions that contribute to ESCC.
1.2 While the 1977 edition of this test method (Dana test) is applicable only to wicking-type insulations, the procedures in this edition are intended to be applicable to all insulating materials, including cements, some of which disintegrate when tested in accordance with the 1977 edition. Wicking insulations are materials that wet through and through when partially (50 to 75 %) immersed in water for a short period of time (10 min or less).
1.3 These procedures are intended primarily as a preproduction test for qualification of the basic chemical composition of a particular manufacturer's product and are not intended to be routine tests for ongoing quality assurance or production lot compliance. Test Methods C871, on the other hand, is used for confirmation of acceptable chemical properties of subsequent lots of insulation previously found acceptable by this test method.
1.4 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.
1.5 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.
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Designation:C692 −08
StandardTest Method for
Evaluating the Influence of Thermal Insulations on External
Stress Corrosion Cracking Tendency of Austenitic Stainless
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Steel
This standard is issued under the fixed designation C692; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1
ε NOTE—Fig. 4 was editorially corrected in December 2010.
1. Scope priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This test method covers two procedures for the labora-
tory evaluation of thermal insulation materials to determine
2. Referenced Documents
whether they contribute to external stress corrosion cracking
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(ESCC) of austenitic stainless steel due to soluble chlorides 2.1 ASTM Standards:
withintheinsulation.Thislaboratoryprocedureisnotintended
A240/A240MSpecification for Chromium and Chromium-
to cover all of the possible field conditions that contribute to Nickel Stainless Steel Plate, Sheet, and Strip for Pressure
ESCC.
Vessels and for General Applications
A370Test Methods and Definitions for Mechanical Testing
1.2 Whilethe1977editionofthistestmethod(Danatest)is
of Steel Products
applicable only to wicking-type insulations, the procedures in
C168Terminology Relating to Thermal Insulation
this edition are intended to be applicable to all insulating
C795Specification for Thermal Insulation for Use in Con-
materials,includingcements,someofwhichdisintegratewhen
tact with Austenitic Stainless Steel
testedinaccordancewiththe1977edition.Wickinginsulations
C871Test Methods for ChemicalAnalysis of Thermal Insu-
are materials that wet through and through when partially (50
lationMaterialsforLeachableChloride,Fluoride,Silicate,
to 75%) immersed in water for a short period of time (10 min
and Sodium Ions
or less).
G30 Practice for Making and Using U-Bend Stress-
1.3 Theseproceduresareintendedprimarilyasapreproduc-
Corrosion Test Specimens
tion test for qualification of the basic chemical composition of
a particular manufacturer’s product and are not intended to be
3. Terminology
routine tests for ongoing quality assurance or production lot
3.1 Definitions:
compliance.Test Methods C871, on the other hand, is used for
Refer to Terminology C168 for definitions relating to insu-
confirmation of acceptable chemical properties of subsequent
lation.
lots of insulation previously found acceptable by this test
method.
4. Summary of Test Method
1.4 The values stated in inch-pound units are to be regarded
4.1 The procedures in this test method consist of using a
as standard. The values given in parentheses are mathematical
specimenofinsulationtoconductdistilled(ordeionized)water
conversions to SI units that are provided for information only
by wicking or dripping to an outside surface, through the
and are not considered standard.
insulation, to a hot inner surface of stressedType 304 stainless
1.5 This standard does not purport to address all of the
steelforaperiodof28days.Ifleachablechloridesarepresent,
safety concerns, if any, associated with its use. It is the
they are carried along with the water and concentrated at the
responsibility of the user of this standard to establish appro-
hot surface by evaporation in much the same way as has been
experienced in actual industrial process situations.
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ThistestmethodisunderthejurisdictionofASTMCommitteeC16onThermal
InsulationandisthedirectresponsibilityofSubcommitteeC16.31onChemicaland
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Physical Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2008. Published October 2008. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1971. Last previous edition approved 2006 as C692–06. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C0692-08. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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C692−08
4.2 Exposed stainless steel coupons are examined visually, 6.3 If the test insulation cannot be made to wick in any way
and under 10 to 30× magnification, if necessary, to detect (such as in the case of organic or inorganic closed-cell foams),
ESCC after the prescribed period of exposure. or when heat treatment of a component of the insulation (such
as an attached exterior jacket material) exceeds the manufac-
5. Significance and Use
turer’s recommended maximum temperature for the exterior
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component, then the 1 ⁄2-in. (38-mm) wide test specimen i
...
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