1、Designation: C 795 03Standard Specification forThermal Insulation for Use in Contact with AusteniticStainless Steel1This standard is issued under the fixed designation C 795; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript 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. Scope1.1 This specification covers non-me
3、tallic thermal insula-tion for use in contact with austenitic stainless steel piping andequipment. In addition to meeting the requirements specified intheir individual material specifications, issued under the juris-diction of ASTM Committee C16, these insulations must passthe preproduction test req
4、uirements of Test Method C 692, forstress corrosion effects on austenitic stainless steel, and theconfirming quality control, chemical requirements, when testedin accordance with the Test Methods C 871.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with i
5、ts use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 168 Terminology Relating to Thermal InsulationC 390 Practice for Sam
6、pling and Acceptance of PreformedThermal Insulation LotsC 692 Test Method for Evaluating the Influence of ThermalInsulations on the External Stress Corrosion CrackingTendency of Austenitic SteelC 871 Test Methods for Chemical Analysis of ThermalInsulation Materials for Leachable Chloride, Fluoride,S
7、ilicate, and Sodium Ions3. Terminology3.1 DefinitionsTerminology C 168 applies to the termsused in this specification.3.2 Definitions of Terms Specific to This Standard:3.2.1 basic material specificationany of the materialspecifications for homogeneous insulation covered in any ofthe pertinent Annua
8、l Book of ASTM Standards.3.2.2 lota lot shall be defined in accordance with PracticeC 390 by agreement between the purchaser and the manufac-turer.3.2.3 stress corrosion crackingthe failure of metal, takingthe form of cracks that potentially occur under the combinedinfluence of certain corrosive env
9、ironments and applied orresidual stresses.3.2.4 wicking-type insulationinsulation material that, byvirtue of its physical characteristics, permits a wetting liquid toinfiltrate it by capillary attraction.4. Significance and Use4.1 Stress corrosion cracking of austenitic stainless steel is ametallurg
10、ical phenomenon. One cause of stress corrosioncracking is the presence of contaminants in water solution,which can be concentrated at the stressed surface by evapora-tion of the water.4.2 There is an apparent correlation between stress corro-sion cracking of austenitic stainless steel and the use of
11、insulation which either contains water-leachable chloride or, byreason of its water absorptivity, acts as a vehicle through whichchlorides from outside the system are concentrated at thesurface of the stainless steel.3,4,54.3 Studies have shown that insulation containing certainwater-soluble compoun
12、ds may retard or prevent chloride-induced stress corrosion. Numerous materials thought to in-hibit stress corrosion cracking have been tried with varyingdegrees of success. An inhibiting compound commonly used issodium silicate. Present knowledge indicates that the sodiumsilicate dissociates in the
13、presence of water, leaving the silicate1This specification is under the jurisdiction of ASTM Committee C16 onThermal Insulation and is the direct responsibility of Subcommittee C16.20 onHomogeneous Inorganic Thermal Insulations.Current edition approved Nov. 1, 2003. Published November 2003. Original
14、lyapproved in 1977. Last previous edition approved in 1998 as C 795 92 (1998)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page
15、onthe ASTM website.3Schaffer, 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., November1, 1961.4Dana, A. W., Jr., “Stress-Corrosion Cra
16、cking of Insulated Austenitic StainlessSteel,” ASTM Bulletin, October 1957.5Louthan, M. R., Jr., “Initial Stages of Stress Corrosion Cracking in AusteniticStainless Steels,” Corrosion, NACE, September 1965.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428
17、-2959, United States.ion to form a protective mechanism that inhibits or prevents thechloride ion from attacking the stainless steel. Under adverseenvironmental conditions, this protective agent will possibly beleached from the product with time and permanent protectionis not afforded.4.4 Test Metho
18、d C 692 contains a procedure for determiningwhether or not chloride-induced stress corrosion cracking willoccur with a given thermal insulation. The procedure is used toevaluate insulation materials that may in themselves be pas-sive, or actively contribute to stress corrosion cracking ofaustenitic
19、stainless steels.5. Ordering Information5.1 The requirements of this specification shall be stated bythe purchaser for the particular insulation and material appli-cation specified. The purchaser shall specify the type, grade,class, dimensions, quantity, and other requirements as availablein the bas
20、ic material specification for a particular insulation.6. Composition6.1 The material shall conform to the established require-ments of the basic material specification.7. Physical and Chemical Requirements7.1 The physical requirements shall conform to the require-ments of the basic material specific
21、ation. The chemical require-ments shall conform to the requirements of Section 13 of thisspecification.8. Dimensions and Permissible Variations8.1 The dimensions and permissible variations shall con-form to the requirements of the basic material specification.9. Workmanship, Finish, and Appearance9.
22、1 The workmanship, finish, and appearance shall conformto the requirements of the basic material specification.10. Sampling10.1 The unit sample shall be of sufficient size to performthe preproduction corrosion test and chemical analysis testsspecified in this specification. The samples shall be of s
23、ufficientsize to ensure an acceptable level of confidence that the testresults represent the characteristics of the product beingpurchased. Sample size shall be in accordance with PracticeC 390.11. Acceptance and Retests11.1 AcceptanceAll specimens in a lot sampling shallmeet the chemical requiremen
24、ts of this specification. If theaverage analysis of the two specimens taken from any samplefails to conform to the requirements of this specification, the lotrepresented by that sample shall be rejected.11.2 RetestAt the option of the supplier, each individualunit of supply (that is, carton, bag, ro
25、ll, sheet, drum, and soforth) in rejected lots are allowed to be retested, in accordancewith Test Methods C 871, at the suppliers expense, by testingsamples taken at random from the unit of supply in accordancewith this specification. Unless otherwise agreed upon betweenthe purchaser and the manufac
26、turer, the resubmitted materialshall require the same number of samples to be tested asrequired for the initial submittal. If the average analysis of thetwo specimens taken from each sample fails to conform to therequirements of this specification, the unit of supply repre-sented by that sample shal
27、l be rejected. For other than chemicalanalysis or stress corrosion tests, the number of tests and retestsshall be as specified in the basic material specification.12. Preproduction Corrosion Test12.1 A corrosion test shall be performed as a preproductiontest by each manufacturer. The production lot
28、from which thesample is taken shall be of the same formulation, made by thesame production processes and from the same kind, nature, andquality of ingredients as those that will be employed forproduction of thermal insulation under this specification.12.2 The corrosion test shall be conducted in acc
29、ordancewith the method presented in Test Method C 692. At the end ofthe test time, none of the prepared coupons of stainless steelshall show a crack when examined in accordance with TestMethod C 692.12.3 The test procedure need not be repeated for subsequentorders using the same production process a
30、nd the same kind,nature, and quality of ingredients unless so required. Themanufacturer shall keep records of actual numerical results ofthe tests available for review on request by those concerned.13. Chemical Analysis13.1 A chemical analysis shall be performed on the insula-tion material in accord
31、ance with Test Methods C 871 and, inaddition, the manufacturer shall demonstrate that his currentproduct has passed the preproduction corrosion test in accor-dance with Test Method C 692.13.1.1 An acceptable proportion of sodium plus silicate ionsto the chloride ions as found by leaching from the in
32、sulation isshown in Fig. 1 and was arrived at empirically. Other insulationcompositions, whose chemical analysis falls outside of theacceptance area shown in Fig. 1, are possibly acceptable;however, their efficacy shall be determined in accordance withTest Method C 692 and subsequently monitored in
33、accordancewith Test Methods C 871.13.2 pHThe pH of the leach water shall be measured, inaccordance with Test Methods C 871, from the specific mate-rial supplied, and shall be greater than 7.0 but not greater than11.7 at 77F (25C), except for insulating or finishing cement,or both, which may have a p
34、H no greater than 12.5.13.3 The specific material supplied shall be analyzed inaccordance with Test Methods C 871 for the following leach-able ions: chloride, sodium, and silicate. The “plot point” ofthese analyses shall fall in the acceptable area of Fig. 1.13.4 The minimum allowable value of sodiu
35、m plus silicateshall be 50 ppm. There is no limit on chloride. Extrapolatingthe chloride level below 10 ppm on Fig. 1 is considered to bein the acceptable are when the sodium and silicate is above 50.14. Handling and Application14.1 See applicable ASTM specifications for handling andapplication.C795
36、03215. Keywords15.1 austenitic stainless steel; chloride; fluoride; pH; sili-cate; sodium; stress corrosion cracking; thermal insulationASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this stan
37、dard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and
38、if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, w
39、hich you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959
40、,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).FIG. 1 Acceptability of Insulation Material on the Basis of the Plot Points of the Cl and the (Na + SiO3) Analyses.C795033
