ASTM_E_2479_-_11.pdf

Designation:E247911Standard Practice forMeasuring the Ultrasonic Velocity in Polyethylene TankWalls Using Lateral Longitudinal(LCR)Waves1This standard is issued under the fixed designation E2479;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.1.Scope*1.1 This practice covers a procedure for measuring theultrasonic velocities in the outer wall of polyethylene storagetanks.An angle beam lateral longitudinal(LCR)wave is excitedwith wedges along a circumferential chord of the tank wall.Adigital ultrasonic flaw detector is used with sending-receivingsearch units in through transmission mode.The observedvelocity is temperature corrected and compared to the expectedvelocity for a new,unexposed sample of material which is thesame as the material being evaluated.The difference betweenthe observed and temperature corrected velocities determinesthe degree of UV exposure of the tank.1.2 The practice is intended for application to the outersurfaces of the wall of polyethylene tanks.Degradation typi-cally occurs in an outer layer approximately 3.2-mm(0.125-in.)thick.Since the technique does not interrogate the insidewall of the tank,wall thickness is not a consideration other thanto be aware of possible guided(Lamb)wave effects orreflections off of the inner tank wall.No special surfacepreparation is necessary beyond wiping the area with a cleanrag.Inside wall properties are not important since the longitu-dinal wave does not strike this surface.The excitation of Lambwaves must be avoided by choosing an excitation frequencysuch that the ratio of wavelength to wall thickness is one fifthor less.1.3 UV degradation on the outer surface causes a stiffeningof the material and an increase in Youngs modulus and thelongitudinal wave velocity.1.4 The values stated in SI units are to be regarded asstandard.The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.5 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:2E494 Practice for Measuring Ultrasonic Velocity in Materi-alsE543 Specification for Agencies Performing NondestructiveTestingE1316 Terminology for Nondestructive ExaminationsE2373 Practice for Use of the Ultrasonic Time of FlightDiffraction(TOFD)Technique2.2 ASNT Documents:3SNT-TC-1A Recommended Practice for NondestructiveTesting Personnel Qualification and CertificationANSI/ASNT CP-189 ASNT Standard for Qualification andCertification of Nondestructive Testing Personnel2.3 AIA Document:4AIA/NAS-410 Nondestructive Testing Personnel Certifica-tion and Qualification3.Terminology3.1 DefinitionsFor definitions of terms used in thispractice,see Terminology E1316.4.Summary of Practice4.1 The lateral longitudinal wave(henceforth called the LCRwave)used in this practice is selected because it is the fastestwave in the tank wall,and,therefore its arrival at the receiverlocation is free from surrounding spurious indications comingthrough the tank wall.The typical setup is shown in Fig.1where the sending and receiving transducers are connectedwith a link through a pivot joint.The frequency selected is suchthat the wavelength is short compared to the wall thickness,1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.06 onUltrasonic Method.Current edition approved July 1,2011.Published July 2011.Last previousedition approved in 2006 as E2479-06.DOI:10.1520/E2479-11.2For 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.3Available fromAmerican Society for Nondestructive Testing(ASNT),P.O.Box28518,1711 Arlingate Ln.,Columbus,OH 43228-0518,http:/www.asnt.org.4Available from Aerospace Industries Association of America,Inc.(AIA),1000Wilson Blvd.,Suite 1700,Arlington,VA22209-3928,http:/www.aia-aerospace.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 assuring bulk wave velocity.Moreover,since it is a bulk wavethe propagation is not affected by variations in the inside tankwall.Therefore,the velocity measured in the outer tank wall isindicative of the material properties of that region,and notaffected by the inner tank wall conditions.5.Significance