1Assessment of the Capabilities of Long-Range Guided-Wave Ultrasonic InspectionsHouston, TexasFebruary 14, 20122Ultrasonic Inspection was developed in the 190s!Ti"e o# Fli$ht% o# an ultrasonic wave is directly proportional to the thic&ness o# the "aterial "easured'ie(oelectric crystal oscillated by )F si$nal*Conventional UT measures the wall thicness at a spot! while Guided Wave Ultrasonics can identif" locations of metal loss along a length of the pipe+eld,etal loss,etal lossFlan$eConventional Ultrasonic Test+eld,etal loss,etal lossGuided Wave#$$% InspectionLocali&ed InspectionConventional ultrasonic inspection provides a local thickness measurementGWUT Inspection provides detection of both internal and external corrosion typically for 100 or more don the pipe!4'ome of the differences between conventional ultrasonic waves and guided waves are(Guided waves are bulk waves; therefore the entire volume of the pipe is inspectedFrequencies used in guided wave inspection are much lower than conventional ultrasonic testing; therefore the wave lengths are much longer and are scattered instead of reflected from changes in the dimension of the wave guideThe pipe acts as a wave guide, permitting the waves to travel long distancesThe waves can be introduced at a single location:+hen introduced with pie(oelectric crystals an array o# transducers are used- .oils o# wire are used to create vibrations in the pipe via the "a$netostrictive e##ect exhibited by #erro"a$netic "aterials

LongitudinalTorsionalFlexuralGuided Wave Ultrasonics rel" on the use and interpretation of far more comple) waves than the compression waves used in conventional UT testing/0uided waves, typically between *0 1 2 3H(, are introduced into the pipe by one o# two syste"s45n array o# pie(oelectric crystals are positioned in "odules that typically hold two transducers each-The "odules are spaced around the pipe under an air bladder which when pressuri(ed #orces the units a$ainst the sur#ace-The individual crystals oscillate at the #re6uency at which they are excited and trans"it the wave into the pipe-.oils o# insulated wire are wrapped around the pipe-5n alternatin$ current is passed throu$h the coils, and an oscillatin$ "a$netic #ield is produced-7ue to the "a$netostrictive e##ect o# #erro"a$netic "aterials, this produces a wave in the pipe which can be a"pli#ied by usin$ a nic&el or cobalt strip bonded to the pipe under the coil-2The power and durability o# today8s electronics has "ade it possible to #ield the 0+UT syste" in a co"pact pac&a$e'ressuri(ed bladder containin$ the array o# pie(oelectric crystals9aptop co"puterField electronicsU"bilical cable connectin$ electronics to transducers:'ome Advantages of Guided Wave Ultrasonic Testing.an test lon$ distances o# pipe #ro" a sin$le access pointHas developed into an e##ective screenin$ tool use#ul in locatin$ and ran&in$ areas o# corrosion; thereby "ini"i(in$ the a"ount o# #ollowwall loss, lon$itudinal len$th, pro#ile? cannot be directly deter"ined@i$ni#icant corrosion can be "issed, especially locali(ed da"a$eThe scattered si$nal cannot be directly e6uated to a speci#ic area or volu"e o# loss due to a lac& o# an absolute calibration standard,any #ield conditions exist that li"it the distances that can be e##ectively inspected and that cause arti#acts which can co"plicate analysis-1*Axa"ples o# conditions that can li"it the distance o# a pipin$ se$"ent that can be reliably inspectedvarious coatin$ such as coal tar epoxies, asphalt