ASTM_G_70_-_07.pdf

Designation:G 70 07Standard Test Method forRing Bendability of Pipeline Coatings(Squeeze Test)1This standard is issued under the fixed designation G 70;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This method covers testing the relative resistance ofpipeline coatings to cracking and spalling from deformation ofthe pipe by observing the effects of diametral compression ofring samples.The method is limited to thin film coatingshaving an elongation not exceeding 5.0%.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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:2G 12 Test Method for Nondestructive Measurement of FilmThickness of Pipeline Coatings on SteelG 62 Test Methods for Holiday Detection in Pipeline Coat-ings3.Summary of Test Method3.1 The method consists of compressing coated pipe ringsamples in a hydraulic arbor press,universal test machine,orother suitable device.The ring sample is compressed to anapproximate oval shape wherein the minor diameter of the ovalis produced by a bending force that elongates the coating at themetal interface.The coating elongation or stretch as producedin the test by compressing the ring to a gaged dimension can becalculated to produce the same coating elongation or stretch aswould occur in actual bending of the pipe to a given radius.Coating failure in the form of cracking or loss of adhesion isdetected by electrical test for holidays while the test is inprocess.3.2 Compression of coated ring samples is controlled by useof a dial indicator,micrometer,or other suitable distance-measuring device.Dimensions are then corrected to outsidedimensions by subtracting the dial indicator or micrometerreading from the initial pipe diameter.4.Significance and Use4.1 The method will provide information on the ability ofpipeline coatings to resist cracking,spalling,or other mechani-cal damage as a result of bending.If the test is applied tocoated pipe samples from commercial production,the resultscan be used in the selection of similar materials for service.Thetest has application as a quality control method when variationsin coating application or material formulation may affectbending performance.5.Apparatus5.1 Compression ApparatusAn arbor press,universal testmachine,or other device that can apply sufficient force at acontrolled rate of movement.5.2 Film Thickness Gage,as described in Test Method G 12.5.3 Holiday DetectorA high-or low-voltage d-c holidaydetector as specified in Test Methods G 62 shall be used tolocate breaks in the coating film.Low-voltage holiday detec-tors shall be used on coatings 0.51 mm(#20 mils)thick andhigh-voltage holiday detectors shall be used on thicker coat-ings.6.Test Specimens6.1 The test specimens shall be coated ring samples 50 6 5mm(2 6 0.20 in.)in length.6.2 Five samples shall be cut from the same piece of coatedpipe by hand saw,power saw,or lathe with care not to damagethe coating in the holding device.All edges shall be visuallydeburred.More samples may be required depending on thetesting application.6.3 Samples shall have areas of coating removed in accor-dance with Fig.1.6.4 The samples shall be free of obvious coating flaws ordefects.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.48 on Durability of Pipeline Coating and Linings.Current edition approved July 1,2007.Published July 2007.Originally approvedin 1981.Last previous edition approved in 1998 as G 70-81(1998)which waswithdrawn March 2007 and reinstated in July 2007.2For 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.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.Copyright ASTM International Provided by IHS under license with ASTM Licensee=University of Texas Revised Sub Account/5620001114 Not for Resale,12/04/2007 06:25:05 MSTNo reproduction or networking permitted without license from IHS-,-,-7.Conditioning7.1 Where compression testing at room temperature isrequired,the specimen shall be exposed to these conditions fora sufficient time to ensure thermal equilibrium in the pipe andcoating.A temperature in the range from 20 to 2