1、Designation: C 692 08Standard Test Method forEvaluating the Influence of Thermal Insulations on ExternalStress Corrosion Cracking Tendency of Austenitic StainlessSteel1This standard is issued under the fixed designation C 692; the number immediately following the designation indicates the year ofori
2、ginal 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.1. Scope1.1 This test method covers two procedures for the labora-tory eva
3、luation of thermal insulation materials to determinewhether they contribute to external stress corrosion cracking(ESCC) of austenitic stainless steel due to soluble chlorideswithin the insulation. This laboratory procedure is not intendedto cover all of the possible field conditions that contribute
4、toESCC.1.2 While the 1977 edition of this test method (Dana test) isapplicable only to wicking-type insulations, the procedures inthis edition are intended to be applicable to all insulatingmaterials, including cements, some of which disintegrate whentested in accordance with the 1977 edition. Wicki
5、ng insulationsare materials that wet through and through when partially (50to 75 %) immersed in water for a short period of time (10 minor less).1.3 These procedures are intended primarily as a preproduc-tion test for qualification of the basic chemical composition ofa particular manufacturers produ
6、ct and are not intended to beroutine tests for ongoing quality assurance or production lotcompliance. Test Methods C 871, on the other hand, is used forconfirmation of acceptable chemical properties of subsequentlots of insulation previously found acceptable by this testmethod.1.4 The values stated
7、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.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. I
8、t 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:2A 240/A 240M Specification for Chromium andChromium-Nickel Stainless Steel Plat
9、e, Sheet, and Stripfor Pressure Vessels and for General ApplicationsA 370 Test Methods and Definitions for Mechanical Testingof Steel ProductsC 168 Terminology Relating to Thermal InsulationC 795 Specification for Thermal Insulation for Use in Con-tact with Austenitic Stainless SteelC 871 Test Metho
10、ds for Chemical Analysis of ThermalInsulation Materials for Leachable Chloride, Fluoride,Silicate, and Sodium IonsG30 Practice for Making and Using U-Bend Stress-Corrosion Test Specimens3. Terminology3.1 Definitions:Refer to Terminology C 168 for definitions relating toinsulation.4. Summary of Test
11、Method4.1 The procedures in this test method consist of using aspecimen of insulation to conduct distilled (or deionized) waterby wicking or dripping to an outside surface, through theinsulation, to a hot inner surface of stressed Type 304 stainlesssteel for a period of 28 days. If leachable chlorid
12、es are present,they are carried along with the water and concentrated at thehot surface by evaporation in much the same way as has beenexperienced in actual industrial process situations.4.2 Exposed stainless steel coupons are examined visually,and under 10 to 303 magnification, if necessary, to det
13、ectESCC after the prescribed period of exposure.1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.31 on Chemical andPhysical Properties.Current edition approved Oct. 1, 2008. Published October 2008. Originallyap
14、proved in 1971. Last previous edition approved 2006 as C 692 06.2For 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 websi
15、te.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 An inherent characteristic of some alloys of austeniticstainless steel is their tendency to crack at stress points whenexposed to certain corrosive environ
16、ments. The mechanisms ofESCC are complex and not completely understood but areapparently related to certain metallurgical properties. Chlorideions concentrated at a stress point will catalyze crack forma-tion. It has been reported that other halide ions do not promoteESCC to the same degree as does
17、chloride using the testtechnology of Test Method C 692 (drip test).35.2 Chlorides are common to many environments, so greatcare shall be taken to protect austenitic stainless steel fromchloride contamination.5.3 Most thermal insulations will not, of themselves, causestress corrosion cracking as show
18、n by qualification tests. Whenexposed to elevated-temperature (boiling point range), envi-ronments containing chlorides, moisture, and oxygen, how-ever, some insulation systems act as collecting media, trans-migrating and concentrating chlorides on heated stainless steelsurfaces. If moisture is not
19、present, the chloride salts cannotmigrate, and stress corrosion cracking because of chloride-contaminated insulation cannot take place.5.4 Insulation materials are available that are speciallyformulated to inhibit stress corrosion cracking in the presenceof chlorides through modifications in basic c
20、omposition orincorporation of certain chemical additives.5.5 The ability of the 28-day test to measure the corrosionpotential of insulation materials is documented by Karnes,4whose data appear to have been used for construction of theacceptability curve used in Specification C 795 and otherspecifica
21、tions.5.6 The metal for all of the coupons used in this test method(C 692) shall be qualified (see Section 14) to ascertain thatunder conditions of the test, chloride ions will cause the metalto crack, and deionized water alone will not cause cracks.6. Applicability (see also 11.2)6.1 While the orig
22、inal test procedure for the 1977 edition ofthis test method (Dana Test) was limited to “wicking-typeinsulations,” the “drip test procedure” given in this edition isapplicable to all insulations when cut or formed into therequired test specimen.6.2 Heat treatment at some temperature (as recommendedby
23、 the manufacturer) up to the maximum use temperature issometimes necessary to make the insulating material “wick,”and thus testable by either insulation test procedure (seeSections 12 and 13).6.3 If the test insulation cannot be made to wick in any way(such as in the case of organic or inorganic clo
24、sed-cell foams),or when heat treatment of a component of the insulation (suchas an attached exterior jacket material) exceeds the manufac-turers recommended maximum temperature for the exteriorcomponent, then the 112-in. (38-mm) wide test specimen issliced into two34-in. (19-mm) thick segments. The
25、two halvesare held together with wire, pins, or a rubber band, and aretested by dripping into the crack between the two halves, thussimulating the situation where water penetrates the junctionbetween two sections of insulation. Wetting the mating faceson the two half sections facilitates water wicki
26、ng down to thecoupon surface.6.4 Adhesives are tested by gluing together a test block ofthe insulation material to be used with the adhesive. Theadhesive joint must come into contact with the stainless steeltest coupon.6.5 Cements with a clay binder are tested by casting a112-in. (38-mm) thick slab,
27、 drying, and using the drip proce-dure. Such a sample will disintegrate in the Dana test proce-dure.6.6 The drip procedure has the potential to be used for thetesting of coatings applied to the coupon prior to test. Thecorrosive liquids dripped into such a system are limited only bythe imagination o
28、f the researcher.7. Apparatus for Dana Test Procedure7.1 EnclosureIn dusty environments, it is permissible forthe test apparatus to be located in a cabinet or other closedstructure provided with a blower to maintain a positive internalpressure, and equipped with a filter for intake air to minimizedu
29、st or other contamination. The test apparatus is normallyhoused in any suitable clean environment not subject tochloride contamination. The enclosure shall not be so tight asto exclude oxygen from the system, since oxygen is necessaryfor ESCC to occur.7.2 Pyrex Glass Wool.7.3 “Cookie Cutter,” made f
30、rom 114 in. (32 mm) thin wallelectrical conduit (inside diameter 1.38 in. (35 mm) to cut a138-in. (35-mm) diameter plug from 2-in. (51-mm) PyrexGlass Wool.7.4 Specimen Holder, as shown in Fig. 1, or equivalent.7.5 Precision Bender, see Practice G30.7.6 Wet-Grinding Belt Grinder, 80-grit.7.7 Copper L
31、ugs, commercial 2/04/0 solderless, or 2 by12by18 in. (51 by 13 by 3.2 mm) copper tabs.7.8 Silver Solder, and chloride-free flux for use with stain-less steel.7.9 Torch, acetylene or propane.7.10 Bolt, stainless steel,316 in. (5 mm) in diameter and212-in. (65-mm) long with insulating washer and nut f
32、orelectrically insulating the bolt from the U-bend specimen.3Private communication from authors of paper presented at Bal Harbour ASTMC16 Symposium on December 9, 1987. Whitaker, T. E., Whorlow, K. M., and Hutto,F. B., Jr., “New Developments in Test Technology for ASTM C692.”4Karnes, H. F., “The Cor
33、rosion Potential ofWettedThermal Insulation,”AICHE,57th National Meeting, Minneapolis, MN, September 26 through 29, 1965. FIG. 1 Suction Cup Coupon HolderC6920827.11 Hand-Held Magnifier,103 or 303 binocular micro-scope, or both.7.12 Band Saw.7.13 Hole Saw, 2-in. (51-mm) outside diameter (optional).7
34、.14 Crystallizing Dish, of borosilicate glass, 712 in. (190mm) in diameter by 4 in. (100 mm) in depth, or stainless steelpan 912 by 512 by 4 in. (41 by 140 by 102 mm) deep.7.15 Electrical Transformer, isolation-type. (approximately150 mV/150 AMP).7.16 Thermocouple, 28 gage or smaller.7.17 Epoxy Adhe
35、sive, aluminum filled.7.18 Drill Bit,932-in. (7-mm), cobalt steel preferred.7.19 Dye Penetrant and Developer, available at most weld-ing supply houses.8. Apparatus for Drip Test Procedure8.1 Steam Heated PipeA 5-ft (1.5-m) section of 112 in.IPS pipe (inconel or other corrosion-resistant material), i
36、sheated either by a small self-contained steam boiler or byregulated house steam.8.2 Peristaltic PumpA multichannel peristaltic pump isused to supply 250 (625) mL/day to each specimen.8.3 I.V. Bottles, 1 L or equivalent, to individually supplyeach test specimen with test liquid.8.4 Specimen Holder,
37、for grinding. See Fig. 1.8.5 Precision Bender, see Fig. 2 in the 1979 edition ofPractice G30.8.6 Wet-Sanding Belt Sander, with 80-grit belt.8.7 Bolt, stainless steel,316 in. (5 mm) in diameter by212-in. (65-mm) long with nut.8.8 Hole Saw, 2-in. (51-mm) outside diameter.8.9 Band Saw.8.10 Thermocouple
38、, 28 gage or smaller.8.11 Heat Transfer Grease, chloride free.8.12 Kimwipe Tissue,5chloride free.9. Reagents and Materials9.1 Distilled or Deionized Water, containing less than 0.1ppm chloride ions.9.2 Distilled or Deionized Water, containing 1500 ppmchloride ion (2.473 g NaCl/L).9.3 Type 304 Stainl
39、ess Steel Sheet16 gage, meeting thecomposition requirements of Specification A 240/A 240M.Certificates of chemical composition and mechanical proper-ties, including ultimate tensile strength and yield strength bythe 0.2 % offset method are required. Type 304 stainless steelmeeting Specification A 24
40、0/A 240M shall have a carboncontent in the range of 0.050.06 % and shall be solution-annealed.10. Test Coupons10.1 Shear 2 by 7-in. (51 by 178-mm) coupons from16-gage Type 304 stainless sheet, as specified in 9.3, with thelong dimension parallel to the long dimension of the sheet.(Long dimension par
41、allel to sheet-rolling direction.)10.2 Clean coupons with chloride-free liquid soap and waterto remove any grease or other contamination.10.3 Sensitize all coupons before bending by heating at1200F (649C) in an argon (inert) or air (oxidizing) atmo-sphere for three hours. Let cool in the furnace aft
42、er thesensitizing period.6Temperature of the coupons must bemeasured in the stack of coupons, not in the furnace itself, asthe coupon temperatures “lag” the furnace temperature by atleast 50 to 100F (28 to 56C).10.4 Asuggestion for sensitizing in an inert atmosphere is touse a stainless steel box wi
43、th a tight-fitting cover to contain theargon around the coupons during sensitization.10.5 Grip coupon with suction cup holder (see Fig. 1)orother means to facilitate wet grinding on an 80-grit belt grinder.Grind parallel to the long dimension of the coupon using an80-grit wet belt with just enough p
44、ressure to remove the dullfinish and leave the metal bright. Do not overgrind. Thebeltground face is the test surface to be exposed to the thermalinsulation. The test area is the bent coupon surface that actuallycomes into contact with the insulation.10.6 Smooth and round sheared edges to prevent ac
45、cidentalcutting of fingers.10.7 Bend each ground coupon to a 1.00 6 0.01-in. (25.4 60.25-mm) outside radius using a roll bender as shown in Fig. 5of the 1979 edition of Practice G30to produce a U-shape inwhich the “legs” are parallel to within116 in. (1.6 mm).10.8 Drill or punch a932-in. (7-mm) hole
46、 in each end usingthe special jig shown in Fig. 3. Cobalt steel drill bits are usedon 304 stainless steel as other bits dull quickly.10.9 For the Dana test only, silver-solder a 2/04/0 solder-less copper electrical connector to each leg with the hole in theconnector centered on the drilled hole. Whi
47、le it has beenconventional to solder one lug to an inside surface and thesecond to an outside surface, it is acceptable to solder both to5Kimwipe is a trademarked product of Kimberly-Clark Corp., Roswell, GA.6For a discussion of the effect of sensitizing stainless steel and its susceptibilityto stre
48、ss corrosion, refer to “Stress-Corrosion Cracking of Sensitized Stainless Steelin Oxygenated High Temperature Water,” Batelle Columbus Laboratories, ReportNo. BMI 1927, June 1972.FIG. 2 Typical External Stress Corrosion Cracks (53Magnification)C692083outside surfaces for greater convenience. The bod
49、y of thecoupon is shielded from high soldering temperatures byplacing a soaking-wet chloride-free cellulose pad on thecoupon next to the weld area to act as a heat sink. Carefullyremove all flux from the finished coupon by washing with hotwater. The contact surfaces of the copper connector is cleanedby sanding, wire brush, or other means to avoid electricalcontact problems.10.9.1 As an alternate to the 2/04/0 solderless lug, 2 by12by18-in. (50.8 by 13 by 3.2-mm) copper lugs are silver-soldered to diagonally opposite outside corners leaving exactlyh
