ASTM_A_418_-_A_418M_-_15.pdf

Designation:A418/A418M15Standard Practice forUltrasonic Examination of Turbine and Generator SteelRotor Forgings1This standard is issued under the fixed designation A418/A418M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This practice for ultrasonic examination covers turbineand generator steel rotor forgings covered by SpecificationsA469/A469M,A470/A470M,A768/A768M,and A940/A940M.This standard shall be used for contact testing only.1.2 This practice describes a basic procedure of ultrasoni-cally inspecting turbine and generator rotor forgings.It doesnot restrict the use of other ultrasonic methods such asreference block calibrations when required by the applicableprocurement documents nor is it intended to restrict the use ofnew and improved ultrasonic test equipment and methods asthey are developed.1.3 This practice is intended to provide a means of inspect-ing cylindrical forgings so that the inspection sensitivity at theforging center line or bore surface is constant,independent ofthe forging or bore diameter.To this end,inspection sensitivitymultiplication factors have been computed from theoreticalanalysis,with experimental verification.These are plotted inFig.1(bored rotors)and Fig.2(solid rotors),for a trueinspection frequency of 2.25 MHz,and an acoustic velocity of2.30 105in./s 5.85 105cm/s.Means of converting to othersensitivity levels are provided in Fig.3.(Sensitivity multipli-cation factors for other frequencies may be derived in accor-dance with X1.1 and X1.2 of Appendix X1.)1.4 Considerable verification data for this method have beengenerated which indicate that even under controlled conditionsvery significant uncertainties may exist in estimating naturaldiscontinuities in terms of minimum equivalent size flat-bottom holes.The possibility exists that the estimated mini-mum areas of natural discontinuities in terms of minimumareas of the comparison flat-bottom holes may differ by 20 dB(factor of 10)in terms of actual areas of natural discontinuities.This magnitude of inaccuracy does not apply to all results butshould be recognized as a possibility.Rigid control of theactual frequency used,the coil bandpass width if tunedinstruments are used,and so forth,tend to reduce the overallinaccuracy which is apt to develop.1.5 This practice for inspection applies to solid cylindricalforgings having outer diameters of not less than 2.5 in.64mm nor greater than 100 in.2540 mm.It also applies tocylindrical forgings with concentric cylindrical bores havingwall thicknesses of 2.5 64 mm in.or greater,within the sameouter diameter limits as for solid cylinders.For solid sectionsless than 15 in.380 mm in diameter and for bored cylindersof less than 7.5 in.190 mm wall thickness the transducer usedfor the inspection will be different than the transducer used forlarger sections.1.6 Supplementary requirements of an optional nature areprovided for use at the option of the purchaser.The supple-mentary requirements shall apply only when specified indi-vidually by the purchaser in the purchase order or contract.1.7 This practice is expressed in both inch-pound units andin SI units;however,unless the purchase order or contractspecifies the applicable M specification designation(SI units),the inch-pound units shall apply.The values stated in eitherinch-pound units or SI units are to be regarded separately asstandard.Within the practice,the SI units are shown inbrackets.The values stated in each system may not be exactequivalents;therefore,each system shall be used independentlyof the other.Combining values from the two systems mayresult in nonconformance with the standard.1.8 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 The reference is to the latest issue of these designationsthat appear in the Annual Book of ASTM Standards or areavailable as separate reprints.It shall also apply to productspecifications,which may be issued when specifically refer-enced therein.1This practice is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of SubcommitteeA01.06 on Steel Forgings and Billets.Current edition approved May 1,2015.Published May 2015.Originallyapproved in 1957.Last previous edition approved in 2010 as A418/A418M 10.DOI:10.1520/A0418_A0418M-15.*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 2.2 ASTM Standards:2A469/A