ASTM_C_795_-_08_2013.pdf

Designation:C79508(Reapproved 2013)Standard Specification forThermal Insulation for Use in Contact with AusteniticStainless Steel1This standard is issued under the fixed designation C795;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript 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.Scope1.1 This specification covers non-metallic 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 requirements of Test Method C692,forstress corrosion effects on austenitic stainless steel,and theconfirming quality control,chemical requirements,when testedin accordance with the Test Methods C871.1.2 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its 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:2C168 Terminology Relating to Thermal InsulationC390 Practice for Sampling and Acceptance of ThermalInsulation LotsC692 Test Method for Evaluating the Influence of ThermalInsulations on External Stress Corrosion Cracking Ten-dency of Austenitic Stainless SteelC871 Test Methods for Chemical Analysis of Thermal Insu-lation Materials for Leachable Chloride,Fluoride,Silicate,and Sodium Ions3.Terminology3.1 DefinitionsTerminology C168 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 Annual Book of ASTM Standards.3.2.2 lota lot shall be defined in accordance with PracticeC390 by agreement between the purchaser and the manufac-turer.3.2.3 stress corrosion cracking(SCC)the failure of metal,taking the form of cracks that potentially occur under thecombined influence of certain corrosive environments andapplied or residual 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 ametallurgical 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 ofinsulation 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 compounds have the capacity to retard or prevent1This 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 May 1,2013.Published May 2013.Originallyapproved in 1977.Last previous edition approved in 2008 as C795 08.DOI:10.1520/C0795-08R13.2For 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 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 Cracking 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 stress corrosion.Numerous materials thought to inhibit stresscorrosion cracking have been tried with varying degrees ofsuccess.An inhibiting compound commonly used is sodiumsilicate.Present knowledge indicates that the sodium silicatedissociates in the presence of water,leaving the silicate ion toform a prot