HandBook ASNT vol 4 Chụp ảnh phóng xạ (Radiographic Testing - RT)

Sách Handbook của Hiệp hội kiểm tra không phá hủy Mỹ viết cho phương pháp kiểm tra chụp ảnh phóng xạ (Radiographic Testing - RT) một trong các phương pháp phổ biến nhất dùng để kiểm tra chất lượng mối hàn, chất lượng sản phẩm và rất nhiều ứng dụng phổ biến khác nữa. Đây là cuốn sách gối đầu cho anhem trong lĩnh vực Kiểm tra không phá hủy (NDT)

Nondestructive Testing Handbook, third edition:

Volume 4, Radiographic Testing on CD-ROM

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Volume 4

Copyright © 2002

AMERICAN SOCIETY FOR NONDESTRUCTIVE TESTING, INC.

All rights reserved.

No part of this book may be reproduced, stored in a retrieval system or transmitted, in any form or by any means —electronic, mechanical, photocopying, recording or otherwise — without the prior written permission of the publisher.Nothing contained in this book is to be construed as a grant of any right of manufacture, sale or use in connection withany method, process, apparatus, product or composition, whether or not covered by letters patent or registered

trademark, nor as a defense against liability for the infringement of letters patent or registered trademark

The American Society for Nondestructive Testing, its employees, and the contributors to this volume assume noresponsibility for the safety of persons using the information in this book

Copyright © 2002 by the American Society for Nondestructive Testing, Incorporated All rights reserved ASNT is notresponsible for the authenticity or accuracy of information herein, and published opinions and statements do notnecessarily reflect the opinion of ASNT Products or services that are advertised or mentioned do not carry the

endorsement or recommendation of ASNT

ACCPSM, IRRSPSM, Level III Study GuideSM, Materials EvaluationSM, NDT HandbookSM, Nondestructive Testing HandbookSM,

The NDT TechnicianSMand www.asnt.orgSMare service marks of the American Society for Nondestructive Testing

ASNT®, Research in Nondestructive Evaluation® and RNDE® are registered trademarks of the American Society for

Nondestructive Testing

ASNT exists to create a safer world by promoting the profession and technologies of nondestructive testing

American Society for Nondestructive Testing, Incorporated

Errata if available for this printing may be obtained from ASNT’s Web site, www.asnt.org, or as hard copy by mail from ASNT,

free on request addressed to the NDT Handbook Editor at the address above.

Library of Congress Cataloging-in-Publication Data

Radiographic Testing / technical editors, Richard H Bossi, Frank A Iddings,

George C Wheeler; 3rd ed.

p cm — (Nondestructive testing handbook ; v 4) Includes bibliographic references and index.

ISBN 1-57117-046-6

1 Radiography, industrial I Bossi, R H II Iddings, F.A III Wheeler, G.C.

IV Moore, Patrick O V American Society for Nondestructive Testing.

IV Series: Nondestructive testing handbook (3rd ed.) ; v 4.

620.1’1272 dc21

Published by the American Society for Nondestructive Testing

PRINTED IN THE UNITED STATES OF AMERICA

NOTE:

Information presented on this page (highlighted in gray) is specific for the

printed version of this publication For Library of Congress

Cataloging-in-Publication data pertaining to the CD-ROM edition, please click this link

The twenty-first century has now arrivedand we are aware that technology willcontinue to accelerate at blinding speed.

As these changes occur, adaptation andimplementation by the end user mustkeep pace with proven innovations Asmanagers and engineers we have beenquick to defend the status quo and havebeen slow to change when change isneeded Currently we are seeing asignificant lag in the usage of suchinnovations as digital radiography Thenew challenge for practitioners andregulatory bodies will be the acceptanceand integration of this already proventechnology

The vitality and future of the AmericanSociety for Nondestructive Testing depend

on the creation, improvement andsharing of information so that safety andreliability stay at the forefront of productdevelopment

This volume represents the efforts ofmany dedicated professionals who haveembraced change and given freely of theirtime with the mission of making adifference in their chosen profession

ASNT commends each and everycontributor for their efforts in bridgingtoday’s technology with tomorrow’spossibilities

There were more than 100 individualcontributors and reviewers, representingboth volunteers and staff in an essentialongoing partnership Each has given apiece of themselves that can never berepaid

A special thanks is due to technicaleditors Richard Bossi, Frank Iddings andGeorge Wheeler for their commitment tothis project This job requires an in-depthunderstanding of the component parts ofthe technology The job is long andtedious and must be driven from the heartand the mind

I must also thank the ASNT staff and

NDT Handbook Editor Patrick Moore for

their guidance and continued pursuit ofexcellence Year in and year out they havemade the necessary sacrifices to ensurequality and value

Finally, reflective tribute must go to anindividual who crossed paths with my

ASNT career briefly in 1974 His start inthe NDT profession came as a

radiographer in the Boston ship yards Hisname was Philip Johnson He was thearchitect and founder of this society Hewas the visionary who saw the need todraw upon our collective differences andunite for a common cause

Johnson served as the organization’sSecretary from 1941 to 1965 He alsoassumed the dual role of editor for many

of those years In addition Johnson served

as our Executive Director from 1965through 1974 Phil provided thecontinuity and focus that must sustainany organization in those formative years

As you read through this book rememberthat it was Johnson that made possiblethe process of cooperative collaboration

Stephen P BlackASNT President, 2001-2002

President’s Foreword

Aims of a Handbook

The volume you are holding in your hand

is the fourth in the third edition of the

Nondestructive Testing Handbook Now is a

good time to reflect on the purposes andnature of a handbook

Handbooks exist in many disciplines ofscience and technology, and certainfeatures set them apart from otherreference works A handbook shouldideally give the basic knowledge necessaryfor an understanding of the technology,including both scientific principles andmeans of application

The typical reader may be assumed tohave completed three years of collegetoward a degree in mechanicalengineering or materials science andhence has the background of anelementary physics or mechanics course

Additionally this volume provides apositive reinforcement for the use ofcomputer based media that enhances itseducational value and enlightens all levels

of education and training

Note that any handbook offers a view

of its subject at a certain period in time

Even before it is published, it can begin toget obsolete The authors and editors dotheir best to be current but the

technology will continue to change even

as the book goes to press

Standards, specifications,recommended practices and inspectionprocedures may be discussed in ahandbook for instructional purposes, but

at a level of generalization that isillustrative rather than comprehensive

Standards writing bodies take great pains

to ensure that their documents aredefinitive in wording and technicalaccuracy People writing contracts orprocedures should consult the actualstandards when appropriate

Those who design qualifyingexaminations or study for them draw onhandbooks as a quick and convenient way

of approximating the body of knowledge

Committees and individuals who write oranticipate questions are selective in whatthey draw from any source The parts of ahandbook that give scientific background,for instance, may have little bearing on apractical examination except to providethe physical foundation to assist handling

of more challenging tasks Other parts of

a handbook are specific to a certain

industry This handbook provides acollection of perspectives on its subject tobroaden its value and convenience to thenondestructive testing community.The present volume is a worthyaddition to the third edition The editors,technical editors and many contributorsand reviewers worked together to bringthe project to completion For theirscholarship and dedication I thankthem all

Gary L WorkmanHandbook Development Director

Foreword

Radiographic testing has been apreeminent method of nondestructivetesting since the discovery of X-rays in

1895 Film radiography in particular hasbeen the backbone of industrial

applications of penetrating radiation It isfundamentally a very elegant analogprocess that provides an internalevaluation of solid objects Although filmradiography remains the most widelyused method of radiographic testing,many other penetrating radiationtechniques for nondestructive testinghave been developed In recent years theadvancements in speed and capability ofdigital data processing have increased theapplication of digital methods forpenetrating radiation inspections Thetransition from analog to digitaltechnology will continue into the future

This volume of the Nondestructive

Testing Handbook, third edition, combines

essential information on the traditionalpenetrating radiation testing techniquesand incoming techniques using digitaltechnology Building on material in thefirst edition (1959) and the second edition(1985), the many contributors of thisvolume have assembled the basic body ofknowledge for radiographic testing Much

of the information in the second editionradiography volume has been maintainedand enhanced, while some dated or rarelyused material has been dropped The firstand second editions thus remain usefulreferences — not only for historicalpurposes but for material that could notlonger be included in the present edition

Considerable new information hasbeen added, particularly in the area ofdigital imaging, data processing anddigital image reconstruction Othermaterial has been updated with recentinformation in such areas as radiationsources, standards, interpretation andapplications Techniques such asbackscatter imaging and computedtomography were not covered in earliereditions but have their own chapter inthis edition

The team of contributors has tried toprepare as useful a text as possible Inmany cases, items are discussed inmultiple chapters to keep the continuity

of the discussion in that particularchapter This also provides multiplecontexts for understanding concepts andtechniques In other cases the handbook

may rely on other chapters for details on

a particular concept The reader isencouraged to refer to the index to findinformation on items of interest inmultiple chapters Because of the currentrate of change in technology, it is notpossible to have a handbook that iscompletely up to date This handbookcontains the fundamental, as well as themost recent material available at the time

of its writing Where possible, tables andfigures are used to serve as a quick andready means of finding essential technicalinformation The references for eachchapter should be helpful for the readerseeking additional material Readers arealso encouraged to use the internet andASNT’s Web site to find supplementalmaterial on equipment and topics that aresubject to change with technologicaladvancement

It has been the pleasure of thetechnical editors to work with the authors

and ASNT’s Nondestructive Testing

Handbook staff to provide this third

edition of the radiography handbook Wewish to thank all the contributors,including those named in the currentvolume, those who provided material tothe contributors and may not have beennamed, and those whose contributions toearlier editions have been carried over tothis edition We hope this edition provesuseful as both a quick reference fortechnical details and a source offundamental information forcomprehensive understanding

Richard H BossiFrank A IddingsGeorge C Wheeler

Preface

Radiographic testing was the dominantmethod of nondestructive testing duringthe first two decades of the AmericanSociety for Nondestructive Testing (ASNT),founded in 1941 When this handbookwas first envisioned in the 1940s, it wasprojected to be a single volume devotedentirely to radiography.

In 1959, when the first edition of the

Nondestructive Testing Handbook finally

appeared, a fourth of it was devoted toradiographic testing In the twenty-firstcentury, the first edition still sells scores

of copies every year

A quarter century was to pass beforethat presentation of radiographic testingwas replaced The second edition gave acomplete volume to the method when, in

1985, ASNT published Radiography and

Radiation Testing Much of the volume in

the present third edition is based directly

on that second edition

The process of outlining this thirdedition volume and recruiting volunteersfor it began in 1996 Richard Bossi andGeorge Wheeler deserve the gratitude ofASNT for the planning that launched theproject In 2001 Frank Iddings, who hadalready edited several chapters, wasappointed as the third technical editor

Seven ASNT past Presidentsparticipated in the writing and review ofthis volume, demonstrating ASNT’sstrength as a truly technical society

This series is not a collection of articlesbut a work of collective authorship by

ASNT, so authors are called contributors.

Volunteers whose contributions to thesecond edition have been updated for thisedition are listed if they were able toparticipate and to approve the product

In the list below, people listed ascontributors were also reviewers but arelisted only once, as contributors

It has been an honor to work withASNT’s volunteers, whose technicalexpertise is matched by their generosity insharing it

I would like to thank staff membersHollis Humphries and Joy Grimm fortheir contributions to the art, layout andtext of the book and also thank

Publications Manager Paul McIntire foryears of encouragement

Patrick O Moore

NDT Handbook Editor

Acknowledgments

Handbook Development Committee

Gary L Workman, University of Alabama,Huntsville

Michael W Allgaier, GPU NuclearAlbert S Birks, AKZO Nobel ChemicalsRichard H Bossi, The Boeing CompanyLisa Brasche, Iowa State UniversityWilliam C Chedister, Circle SystemsJames L Doyle, Northwest ResearchAssociates, Inc

Nat Y Faransso, Halliburton CompanyFrançois Gagnon, Vibra-K ConsultantsRobert E Green, Jr., Johns HopkinsUniversity

Matthew J Golis, Advanced QualityConcepts

Gerard K Hacker, Teledyne BrownEngineering

Harb S Hayre, Ceie SpecsFrank A Iddings

Charles N Jackson, Jr

John K Keve, DynCorp Tri-Cities ServicesLloyd P Lemle, Jr., BP Oil CompanyXavier P.V Maldague, University LavalPaul M McIntire, ASNT

Mani Mina, Iowa State UniversityRon K Miller, Physical AcousticsCorporation

Scott D Miller, Saudi AramcoPatrick O Moore, ASNTStanley Ness

Louis G Pagliaro, Technical Associates ofCharlotte

Emmanuel P Papadakis, Quality SystemsConcepts

Stanislav I Rokhlin, Ohio State UniversityFrank J Sattler

Fred Seppi, Williams InternationalAmos G Sherwin, Sherwin IncorporatedKermit S Skeie

Roderic K Stanley, Quality TubingHolger H Streckert, General AtomicsStuart A Tison, Millipore CorporationNoel A Tracy, Universal TechnologyCorporation

Satish S Udpa, Michigan State UniversitySotirios J Vahaviolos, Physical AcousticsCorporation

Mark F.A Warchol, Aluminum Company

of AmericaGlenn A Washer, Federal HighwayAdministration

George C Wheeler

Editor’s Preface

Richard D Albert, Digiray CorporationRichard C Barry, Lockheed MartinMissiles and Space

Garry L Balestracci, Balestracci UnlimitedJohn P Barton

George L BeckerHarold Berger, Industrial Quality,Incorporated

Bruce E Bolliger, Agilent TechnologiesRichard H Bossi, The Boeing Company,Seattle

Lisa Brasche, Iowa State UniversityRoy L Buckrop

Clifford Bueno, General Electric CompanyWilliam D Burnett

Paul Burstein, Skiametics IncorporatedHerbert Chapman

Francis M CharbonnierKenneth W Dolan, Lawrence LivermoreNational Laboratory

C Robert EmighToshiyasu FukuiDonald J HagemaierJerry J Haskins, Lawrence LivermoreNational Laboratory

Charles J Hellier III, Hellier andAssociates

Eiichi HirosawaFrank A IddingsTimothy E Kinsella, CarpenterTechnology CorporationGary G Korkala, Security Defense SystemsAndreas F Kotowski, Rapiscan SecurityProducts

Lawrence R LawsonHarry E Martz, Lawrence LivermoreNational Laboratory

William E.J McKinneyMasahisa NaoeJames M Nelson, The Boeing Company,Seattle

Stig Oresjo, Agilent TechnologiesWilliam B Rivkin

Stanislav I Rokhlin, Ohio State UniversityEdward H Ruescher

Frank J SattlerDaniel J Schneberk, Lawrence LivermoreNational Laboratory

Samuel G SnowGeorge R Strabel, Howmet ResearchCorporation

Holger H Streckert, General AtomicsMarvin W Trimm, WestinghouseSavannah River CompanyGeorge C Wheeler

Gerald C WicksWilliam P Winfree, National Aeronauticsand Space Administration

Mark Branecki, NRay ServicesJack S Brenizer, Pennsylvania StateUniversity

Joseph F Bush, Jr., NDT TrainingRichard E Cameron, General ElectricNuclear Energy

W Dennis Cabe, Duke Energy CompanyEugene J Chemma, Bethlehem SteelCorporation

Thomas N Claytor, Los Alamos NationalLaboratory

Robert L Crane, Air Force ResearchLaboratory

Claude D Davis, Unified Testing ServicesJohn Deboo, The Boeing CompanyDonny Dicharry, Source Production andEquipment

Paul DickLouis J Elliott, Lockheed Martin TacticalDefense Systems

Hugh W Evans, Amersham CorporationJonathan C Fortkamp, ABB AutomationIncorporated

William D Friedman, Lockheed MartinSteven G Galbraith, INEEL, Idaho FallsBryan C Goode, Faxitron X-RayCorporation

Thorsten Graeve, Rad-Icon ImagingCorporation

Joseph N Gray, Iowa State UniversityNand Gupta, Omega InternationalTechnologies

David P Harvey, Oremet-Wah ChangManfred P Hentschel, Federal Institute forMaterials Research and Testing, Berlin,Germany

Michael R Holloway, Eastman KodakCompany

James W Houf, American Society forNondestructive Testing

Bruce G Isaacson, ISAChester W Jackson, WestinghouseJames H Johnson, Varian IndustrialProducts

Thomas S Jones, Howmet ResearchCorporation

Jim F Kelly, Rivest Testing USA/IUOEBradley S Kienlen, Entergy OperationsRichard Kochakian, Agfa CorporationJeffrey Kollgaard, The Boeing CompanyJames R Korenkiewicz, SamsungAerospace, Pratt and WhitneyJoseph L Mackin, International PipeInspectors Association

K Dieter MarkertNick Martinsen, Varian IndustrialProducts

Robert W McClung

Thomas E McConomy, Special MetalsCorporation

Claude H McDanielRobert M McGee, Ford Motor CompanyRichard D McGuire, National Board ofBoiler and Pressure Vessel InspectorsWilliam D Meade, The Boeing CompanyJohn Munro III

Antonio G Pascua, The Boeing Company,Canoga Park

J.A Patsey, US Steel Tubular ProductsPatrick Pauwels, Agfa-Gevaert, MortselThea Philliou, Thermo EberlineDavid H Phillips, Hytec, IncorporatedRobert F Plumstead, Lucius PitkinIncorporated

William C Plumstead, Sr., PQT ServicesRita Pontefract, Yxlon International,Akron

Joergen Rheinlaender, InnospeXion ApS,Hvalsø, Denmark

Wade J Richards, McClellan Air ForceBase

Scott D Ritzheimer, Allegheny LudlumSteel Company

Morteza Safai, FMC FoodTechRobert L Schulte, Digtome CorporationRussell G Schonberg, Schonberg ResearchCorporation

Noel D Smith, NDS ProductsJoel Henebry, Test and MeasurementOrganization

Jana Knezovich, Agilent TechnologiesHabeeb H Saleh, WJE AssociatesFred J Schlieper, TeradynePeter Soltani, Direct RadiographyCorporation

Dennis S Smith, McDonnell DouglasAerospace

Richard C StarkBrian Sterling, TimcoRichard Z Struk, Shellcast Foundries,Montreal, Canada

Barry N Taylor, National Institute ofStandards and TechnologyJay D Thompson, Lockheed MartinMissiles and Space

Michael L Turnbow, Tennessee ValleyAuthority

Ray Tsukimura, Aerotest OperationsJerry A Tucker, Industrial NuclearThomas B Turner, BWX TechnologiesJohn J Veno

Mark F.A Warchol, Alcoa, IncorporatedRandall D Wasberg, Amcast AutomotiveGlenn A Washer, Federal HighwayAdministration

Amy Waters, Varian Industrial ProductsGene A Westenbarger, Ohio UniversityDwight S Wilson, The Boeing Company,Long Beach

Charles B Winfield, Tru-Tec Services,Incorporated

Sik-Lam Wong, Maxwell PhysicsInternational

Daniel A Wysnewski, Agfa Corporation

Additional Acknowledgments

For Chapter 8, “RadiographicInterpretation,” the contributors andeditors gratefully acknowledge thecontributions by Newport NewsShipbuilding and Drydock Company (R.R.Hardison, L.S Morris, D.L Isenhour andR.D Wallace) and by the NationalInstitute of Standards and Technology(G Yonemura) Appreciation is alsoexpressed to Eastman Kodak Company,Electric Power Research Institute, ASTMInternational and the Southwest ResearchInstitute for permission to use

illustrations

The applications presented inChapter 13, “Image Data Analysis,” arethe result of many collaborative efforts.Thanks to Ford Nondestructive EvaluationLaboratory (R McGee and staff); to

Sources of illustrations areacknowledged in a section at the end ofthis book

Chapter 1 Introduction to

Radiographic Testing 1

Part 1 Nondestructive Testing 2

Part 2 Management of Radiographic Testing 12

Part 3 History of Radiographic Testing 21

Part 4 Units of Measure for Radiographic Testing 29

Chapter 2 Radiation and Particle Physics 37

Part 1 Elementary Particles 38

Part 2 Properties of Radioactive Materials 42

Part 3 Electromagnetic Radiation 48

Chapter 3 Electronic Radiation Sources 55

Part 1 Physical Principles 56

Part 2 Basic Generator Construction 59

Part 3 Megavolt Radiography 67

Chapter 4 Isotope Radiation Sources for Gamma Radiography 73

Part 1 Selection of Radiographic Sources 74

Part 2 Source Handling Equipment 79

Chapter 5 Radiation Measurement 89

Part 1 Principles of Radiation Measurement 90

Part 2 Ionization Chambers and Proportional Counters 91

Part 3 Geiger-Müller Counters 96

Part 4 Scintillation Detectors 100

Part 5 Luminescent Dosimetry 102

Part 6 Neutron Detection 104

Part 7 Semiconductors 106

Part 8 Film Badges 108

Chapter 6 Radiation Safety 113

Part 1 Management of Radiation Safety 114

Part 2 Dose Definitions and Exposure Levels 119

Part 3 Radiation Protection Measurements 121

Part 4 Basic Exposure Control 127

Part 5 Shielding 130

Part 6 Neutron Radiographic Safety 134

Chapter 7 Principles of Film Radiography 139

Part 1 Film Exposure 140

Part 2 Absorption and Scattering 152

Part 3 Radiographic Screen 159

Part 4 Industrial X-Ray Films 163

Part 5 Radiographic Image Quality and Detail Visibility 170

Part 6 Film Handling and Storage 177

Part 7 Film Digitization 180

Chapter 8 Radiographic Interpretation 185

Part 1 Fundamentals of Radiographic Interpretation 186

Part 2 Viewing in Radiographic Testing 189

Part 3 Densitometers 194

Part 4 Radiographic Interpretation Reporting 199

Part 5 Radiographic Artifacts 202

Part 6 Discontinuity Indications 207

Chapter 9 Radiographic Film Development 219

Part 1 Radiographic Latent Image 220

Part 2 Chemistry of Film Radiography 230

Part 3 Darkroom 237

Part 4 Processing Technique 241

Part 5 Silver Recovery 247

Chapter 10 Radioscopy 253

Part 1 Fundamentals of Radioscopic Imaging 254

Part 2 Light Conversion 256

Part 3 Image Quality 261

Part 4 Imaging Systems 265

Part 5 Cameras 269

Part 6 Viewing and Recording 275

Part 7 System Considerations 277

Chapter 11 Digital Radiographic Imaging 283

Part 1 Overview of Digital Imaging 284

Part 2 Principles of Digital X-Ray Detectors 286

Part 3 Image Contrast and Signal Statistics 289

Part 4 X-Ray Detector Technology 296

Chapter 12 Computed Tomography 303

Part 1 Introduction to Computed Tomography 304

Part 2 Laminography 306

Part 3 Principles of Computed Tomography 310

Part 4 Resolution and Contrast 316

Part 5 Computed Tomographic Systems 318

Part 6 Applications of Computed Tomography 323

Part 7 Reference Standards for Computed Tomography 328

Chapter 13 Image Data Analysis 345

Part 1 Fundamental Properties of Digital Images and Processing Schemes 346

Part 2 Image Analysis Techniques and Radiographic Tests 353

Part 3 Automated Testing Techniques 354

Chapter 14 Backscatter Imaging 379

Part 1 Physical Principles 380

Part 2 Backscatter Imaging Techniques 388

Part 3 Reconstruction and Image Processing Techniques 392

Part 4 Applications of Backscatter Imaging 394

Chapter 15 Special Radiographic Techniques 403

Part 1 Microfocus Radiographic Testing 404

Part 2 Flash Radiography 409

Part 3 Reversed Geometry Radiography with Scanning Source 414

Part 4 Stereo Radiography 419

Part 5 X-Ray Diffraction and X-Ray Fluorescence 427

Chapter 16 Neutron Radiography 437

Part 1 Applications of Neutron Radiography 438

Part 2 Static Radiography with Thermal Neutrons 440

Part 3 Special Techniques of Neutron Radiography 446

Chapter 17 Radiographic Testing of Metal Castings 453

Part 1 Introduction to Radiographic Testing of Metal Castings 454

Part 2 General Radiographic Techniques for Metal Castings 455

Part 3 Radiographic Indications for Metal Castings 461

Part 4 Radiographic Testing and Process Scheduling 465

Part 5 Problems in Radiographic Testing of Metal Castings 467

Chapter 18 Radiographic Testing of Welds 473

Part 1 Introduction to Radiographic Testing of Welds 474

Part 2 Weld Design 475

Part 3 Discontinuities in Welds 478

Part 4 Technique Development 482

Part 5 Standards and Specifications for Radiographic Testing of Welds 489

Part 6 Radiography of Weld Discontinuities 491

Part 7 In-Process Radioscopy of Arc Welding 502

Part 8 False Indications in Radiographs of Aluminum Alloy Welds 507

Chapter 19 Radiographic Testing in Utility, Petroleum and Chemical Industries 513

Part 1 Overview 514Part 2 Pipe and Tubing

Applications 515Part 3 Vessel and Component

Applications 526Part 4 Nuclear Fuel

Applications 530Part 5 Other Uses for

of Space FlightComponents 550Part 3 Techniques for Advanced

Electronics 578Part 3 Radiographic Testing of

Consumer Goods 584Part 4 Radiographic Testing in

Security Systems 588Part 5 Infrastructure

Applications ofRadiographic Testing 591Part 6 Radiographic Testing in

Conservation of HistoricBuildings and MuseumObjects 594

Chapter 22 Attenuation Coefficients 609

Part 1 Introduction to

AttenuationCoefficients 610Part 2 Attenuation Coefficient

Copyright © 2002

AMERICAN SOCIETY FOR NONDESTRUCTIVE TESTING, INC.

All rights reserved.

No part of this book may be reproduced, stored in a retrieval system or transmitted, in any form or by any means —electronic, mechanical, photocopying, recording or otherwise — without the prior written permission of the publisher.Nothing contained in this book is to be construed as a grant of any right of manufacture, sale or use in connection withany method, process, apparatus, product or composition, whether or not covered by letters patent or registered

trademark, nor as a defense against liability for the infringement of letters patent or registered trademark

The American Society for Nondestructive Testing, its employees, and the contributors to this volume assume noresponsibility for the safety of persons using the information in this book

Copyright © 2002 by the American Society for Nondestructive Testing, Incorporated All rights reserved ASNT is notresponsible for the authenticity or accuracy of information herein, and published opinions and statements do notnecessarily reflect the opinion of ASNT Products or services that are advertised or mentioned do not carry the

endorsement or recommendation of ASNT

ACCPSM, IRRSPSM, Level III Study GuideSM, Materials EvaluationSM, NDT HandbookSM, Nondestructive Testing HandbookSM,

The NDT TechnicianSMand www.asnt.orgSMare service marks of the American Society for Nondestructive Testing

ASNT®, Research in Nondestructive Evaluation® and RNDE® are registered trademarks of the American Society for

Nondestructive Testing

ASNT exists to create a safer world by promoting the profession and technologies of nondestructive testing

American Society for Nondestructive Testing, Incorporated

Errata if available for this printing may be obtained from ASNT’s Web site, www.asnt.org, or as hard copy by mail from ASNT,

free on request addressed to the NDT Handbook Editor at the address above.

Library of Congress Cataloging-in-Publication Data

Radiographic Testing [computer file] / technical editors, Richard H Bossi, Frank

A Iddings, George C Wheeler; 3rd ed.

1 computer optical disc; 4 3/4 in — (Nondestructive testing handbook; v 4) System requirements for Windows: 486 or Pentium PC; 8 MB RAM (16 MB RAM for windows NT); Windows 95/98 or windows NT 4.0 with Service Pack 3

or later; Adobe Acrobat Reader 5.0 (included); CD-ROM drive.

System requirements for Macintosh: Apple Power Macintosh; 4.5 MB RAM;

System 7.1.2 or later; 8 MB free hard disk space; Adobe Acrobat Reader 5.0 (included); CD-ROM drive.

Title from disc label.

Audience: Quality control engineers and inspectors Summary:

ISBN 1-57117-098-7

NOTE:

Information presented on this page is specific for the CD-ROM version of this publication For Library of Congress Cataloging-in-Publication data pertaining to the printed edition, please click this link

M U L T I M E D I A C O N T E N T S

Chapter 4 Isotope Radiation Sources

for Gamma Radiography 73

Movie Isotopic source 74

Movie Collimators 82

Chapter 6 Radiation Safety 113

Movie Radiation injury 114

Movie Survey meters 117

Movie Check equipment 121

Movie Personnel Monitoring Devices 124

Movie Warning tape and signs 128 Chapter 7 Principles of Film Radiography 139

Movie Conventional radiography gives shadow image 140

Chapter 10 Radioscopy 253

Movie Automated wheel inspection 279

Chapter 12 Computed Tomography 303

Movie Second generation (rotate and translate) 319

Movie Third generation (rotate only) 319

Movie Electronic device on turntable 327

Movie Images of electronic device 327

Movie Tomographic data image of electronic device 327

Movie Image slices of device, top to bottom 327

Movie Slices show delaminations in composite fastener hole 327

Movie Transverse image of delaminations in fastener hole 327

Chapter 13 Image Data Analysis 345

Movie Exfoliation corrosion, thin to thick 374

Movie General corrosion, thin to thick 374

Movie Cracks around fasteners 374 Movie Cracks around fasteners, in layers from top 374

Chapter 14 Backscatter Imaging 379

Movie Backscatter scan of undamaged area 397

Movie Moving source and sensor into place 397

Movie Pillowing and corrosion 397 Chapter 20 Aerospace Applications of Radiographic Testing 543

Movie Automated inspection of rocket motor 551

Chapter 21 Other Applications of Radiographic Testing 569

Movie Inspection of printed circuit boards 583

Movie Radiographic inspection of light bulb 587 Movie Cargo scanning 589

Movie Image acquisition and evaluation 589

Movie Images at 3 MV and 6 MV 589

Movie Contraband in water tank 589

Harold Berger, Industrial Quality, Incorporated, Gaithersburg, Maryland (Part 3)

Holger H Streckert, General Atomics, San Diego, California (Part 4)

Marvin W Trimm, Westinghouse Savannah River Company, Aiken, South Carolina (Parts 1 and 2)

1

Introduction to Radiographic Testing

Nondestructive testing (NDT) has been

defined as comprising those test methodsused to examine or inspect a part ormaterial or system without impairing itsfuture usefulness.1The term is generallyapplied to nonmedical investigations ofmaterial integrity

Strictly speaking, this definition ofnondestructive testing includesnoninvasive medical diagnostics X-rays,ultrasound and endoscopes are used byboth medical and industrial

nondestructive testing Medicalnondestructive testing, however, has come

to be treated by a body of learning soseparate from industrial nondestructivetesting that today most physicians do not

use the word nondestructive.

Nondestructive testing is used toinvestigate specifically the materialintegrity of the test object A number ofother technologies — for instance, radioastronomy, voltage and amperagemeasurement and rheometry (flowmeasurement) — are nondestructive butare not used specifically to evaluatematerial properties Radar and sonar areclassified as nondestructive testing whenused to inspect dams, for instance, butnot when they are used to chart a riverbottom

Nondestructive testing asks “Is theresomething wrong with this material?” Incontrast, performance and proof tests ask

“Does this component work?” It is notconsidered nondestructive testing when

an inspector checks a circuit by runningelectric current through it Hydrostaticpressure testing is another form of prooftesting, one that may destroy the testobject

Another gray area that invites variousinterpretations in defining nondestructive

testing is future usefulness Some material

investigations involve taking a sample ofthe inspected part for testing that isinherently destructive A noncritical part

of a pressure vessel may be scraped orshaved to get a sample for electronmicroscopy, for example Although futureusefulness of the vessel is not impaired bythe loss of material, the procedure isinherently destructive and the shaving

itself — in one sense the true test object —

has been removed from servicepermanently

The idea of future usefulness is relevant

to the quality control practice of

sampling Sampling (that is, less than

100 percent testing to draw inferences

about the unsampled lots) is

nondestructive testing if the tested sample

is returned to service If the steel is tested

to verify the alloy in some bolts that canthen be returned to service, then the test

is nondestructive In contrast, even ifspectroscopy used in the chemical testing

of many fluids is inherentlynondestructive, the testing is destructive ifthe samples are poured down the drainafter testing

Nondestructive testing is not confined

to crack detection Other discontinuitiesinclude porosity, wall thinning fromcorrosion and many sorts of disbonds.Nondestructive material characterization

is a growing field concerned with materialproperties including material

identification and microstructuralcharacteristics — such as resin curing, casehardening and stress — that have a directinfluence on the service life of the testobject

Nondestructive testing has also beendefined by listing or classifying thevarious techniques.1-3This sense of

nondestructive testing is practical in that it

typically highlights methods in use byindustry

Purposes of Nondestructive Testing

Since the 1920s, the art of testing withoutdestroying the test object has developedfrom a laboratory curiosity to anindispensable tool of fabrication,construction and manufacturingprocesses No longer is visual testing ofmaterials, parts and complete productsthe principal means of determiningadequate quality Nondestructive tests ingreat variety are in worldwide use todetect variations in structure, minutechanges in surface finish, the presence ofcracks or other physical discontinuities, tomeasure the thickness of materials andcoatings and to determine othercharacteristics of industrial products.Scientists and engineers of manycountries have contributed greatly tonondestructive test development andapplications

The various nondestructive testingmethods are covered in detail in the

P ART 1 Nondestructive Testing 1

literature but it is always wise to considerobjectives before details How is

nondestructive testing useful? Why dothousands of industrial concerns buy thetesting equipment, pay the subsequentoperating costs of the testing and evenreshape manufacturing processes to fit theneeds and findings of nondestructivetesting?

Modern nondestructive tests are used

by manufacturers (1) to ensure productintegrity and, in turn, reliability; (2) toavoid failures, prevent accidents and savehuman life (see Figs 1 and 2); (3) to make

a profit for the user; (4) to ensurecustomer satisfaction and maintain themanufacturer’s reputation; (5) to aid inbetter product design; (6) to controlmanufacturing processes; (7) to lowermanufacturing costs; (8) to maintainuniform quality level; and (9) to ensureoperational readiness

These reasons for widespread andprofitable nondestructive testing aresufficient in themselves but paralleldevelopments have contributed to itsgrowth and acceptance

Increased Demand on Machines

In the interest of greater speed andreduced cost for materials, the designengineer is often under pressure to reduceweight This can sometimes be done bysubstituting aluminum alloys, magnesiumalloys or composite materials for steel oriron but such light parts may not be thesame size or design as those they replace

The tendency is also to reduce the size

These pressures on the designer havesubjected parts of all sorts to increasedstress levels Even such commonplaceobjects as sewing machines, sauce pansand luggage are also lighter and moreheavily loaded than ever before The stress

to be supported is seldom static It often

fluctuates and reverses at low or highfrequencies Frequency of stress reversalsincreases with the speeds of modernmachines and thus parts tend to fatigueand fail more rapidly

Another cause of increased stress onmodern products is a reduction in thesafety factor An engineer designs withcertain known loads in mind On thesupposition that materials andworkmanship are never perfect, a safetyfactor of 2, 3, 5 or 10 is applied However,because of other considerations, a lowerfactor is often used that depends on theimportance of lighter weight or reducedcost or risk to consumer

New demands on machinery have alsostimulated the development and use ofnew materials whose operating

characteristics and performance are notcompletely known These new materialscreate greater and potentially dangerousproblems As an example, an aircraft partwas built from an alloy whose workhardening, notch resistance and fatiguelife were not well known After relativelyshort periods of service some of theseaircraft suffered disastrous failures

Sufficient and proper nondestructive testscould have saved many lives

As technology improves and as servicerequirements increase, machines aresubjected to greater variations and towider extremes of all kinds of stress,creating an increasing demand forstronger or more damage tolerantmaterials

Engineering Demands for Sounder Materials

Another justification for nondestructivetests is the designer’s demand for sounder

F IGURE 1 Fatigue cracks caused damage to aircraft fuselage,

causing death of flight attendant and injury to passengers

(April 1988)

F IGURE 2 Boilers operate with high internal steam pressure.

Material discontinuites can lead to sudden, violent failurewith possible injury to people and property

materials As size and weight decrease andthe factor of safety is lowered, moreemphasis is placed on better raw materialcontrol and higher quality of materials,manufacturing processes and

workmanship

An interesting fact is that a producer ofraw material or of a finished productsometimes does not improve quality orperformance until that improvement isdemanded by the customer The pressure

of the customer is transferred toimplementation of improved design ormanufacturing Nondestructive testing isfrequently called on to deliver this newquality level

Public Demands for Greater Safety

The demands and expectations of thepublic for greater safety are apparenteverywhere Review the record of thecourts in granting high awards to injuredpersons Consider the outcry for greaterautomobile safety, as evidenced by therequired automotive safety belts and thedemand for air bags, blowout proof tiresand antilock braking systems Thepublicly supported activities of theNational Safety Council, UnderwritersLaboratories, the Occupational Safety andHealth Administration and the FederalAviation Administration in the UnitedStates, as well as the work of similaragencies abroad, are only a few of theways in which this demand for safety isexpressed It has been expressed directly

by passengers who cancel reservationsfollowing a serious aircraft accident Thisdemand for personal safety has beenanother strong force in the development

of nondestructive tests

Rising Costs of Failure

Aside from awards to the injured or toestates of the deceased and aside fromcosts to the public (because of evacuationoccasioned by chemical leaks), considerbriefly other factors in the rising costs ofmechanical failure These costs areincreasing for many reasons Someimportant ones are (1) greater costs ofmaterials and labor; (2) greater costs ofcomplex parts; (3) greater costs because ofthe complexity of assemblies; (4) greaterprobability that failure of one part willcause failure of others because ofoverloads; (5) trend to lower factors ofsafety; (6) probability that the failure ofone part will damage other parts of highvalue; and (7) part failure in an integratedautomatic production machine, shuttingdown an entire high speed productionline When production was carried out onmany separate machines, the broken onecould be bypassed until repaired Today,one machine is tied into the production

of several others Loss of such production

is one of the greatest losses resulting frompart failure

Applications of Nondestructive Testing

Nondestructive testing is a branch of thematerials sciences that is concerned withall aspects of the uniformity, quality andserviceability of materials and structures.The science of nondestructive testingincorporates all the technology fordetection and measurement of significantproperties, including discontinuities, initems ranging from research specimens tofinished hardware and products in service

By definition, nondestructive testingmethods are means for examiningmaterials and structures withoutdisruption or impairment of serviceability.Nondestructive testing makes it possiblefor internal properties or hiddendiscontinuities to be revealed or inferred

Classification of Methods

In a report, the National MaterialsAdvisory Board (NMAB) Ad HocCommittee on Nondestructive Evaluationadopted a system that classified

techniques into six major methodcategories: visual, penetrating radiation,magnetic-electrical, mechanical vibration,thermal and chemical/electrochemical.3Amodified version is presented in Table 1.1Each method can be completelycharacterized in terms of five principalfactors: (1) energy source or medium used

to probe object (such as X-rays, ultrasonicwaves or thermal radiation); (2) nature ofthe signals, image or signature resultingfrom interaction with the object(attenuation of X-rays or reflection ofultrasound, for example); (3) means ofdetecting or sensing resultant signals(photoemulsion, piezoelectric crystal orinductance coil); (4) method of indicating

or recording signals (meter deflection,oscilloscope trace or radiograph); and(5) basis for interpreting the results (direct

or indirect indication, qualitative orquantitative and pertinent dependencies)

The objective of each method is toprovide information about the followingmaterial parameters: (1) discontinuitiesand separations (cracks, voids, inclusionsdelaminations and others); (2) structure ormalstructure (crystalline structure, grainsize, segregation, misalignment andothers); (3) dimensions and metrology(thickness, diameter, gap size,

discontinuity size and others); (4) physicaland mechanical properties (reflectivity,conductivity, elastic modulus, sonicvelocity and others); (5) composition andchemical analysis (alloy identification,impurities, elemental distributions andothers); (6) stress and dynamic response(residual stress, crack growth, wear,vibration and others); (7) signatureanalysis (image content, frequencyspectrum, field configuration and others);

and (8) abnormal sources of heat

Terms used in this block are furtherdefined in Table 2 with respect to specificobjectives and specific attributes to bemeasured, detected and defined

The limitations of a method includeconditions required by that method:

conditions to be met for methodapplication (access, physical contact,preparation and others) and requirements

to adapt the probe or probe medium tothe object examined Other factors limitthe detection or characterization ofdiscontinuities, properties and otherattributes and limit interpretation ofsignals or images generated

Classification Relative to Test Object

Nondestructive testing techniques may beclassified according to how they detectindications relative to the surface of a testobject Surface methods include liquidpenetrant testing, visual testing, grid andmoiré testing Surface/near-surfacemethods include tap, potential drop,holography and shearography, magneticparticle and electromagnetic testing

When surface or surface/near-surfacemethods are applied during intermediatemanufacturing processes, they providepreliminary assurance that volumetricmethods performed on the completedobject or component will reveal fewrejectable discontinuities Volumetricmethods include radiography, ultrasonictesting, acoustic emission testing and lesswidely used methods such as

acoustoultrasonic testing and magneticresonance imaging Through-boundarytechniques described include leak testing,some infrared thermographic techniques,airborne ultrasonic testing and certaintechniques of acoustic emission testing

Other less easily classified methods arematerial identification, vibration analysisand strain gaging

No one nondestructive testing method

is all revealing That is not to say that onemethod or technique of a method israrely adequate for a specific object orcomponent However, in most cases ittakes a series of test methods to do acomplete nondestructive test of an object

T ABLE 1 Nondestructive testing method categories.

Basic Categories

Mechanical and optical color; cracks; dimensions; film thickness; gaging; reflectivity; strain distribution and magnitude; surface

finish; surface flaws; through-cracksPenetrating radiation cracks; density and chemistry variations; elemental distribution; foreign objects; inclusions; microporosity;

misalignment; missing parts; segregation; service degradation; shrinkage; thickness; voidsElectromagnetic and electronic alloy content; anisotropy; cavities; cold work; local strain, hardness; composition; contamination;

corrosion; cracks; crack depth; crystal structure; electrical conductivities; flakes; heattreatment; hot tears; inclusions; ion concentrations; laps; lattice strain; layer thickness; moisture content;polarization; seams; segregation; shrinkage; state of cure; tensile strength; thickness; disbonds

Sonic and ultrasonic crack initiaion and propagation; cracks, voids; damping factor; degree of cure; degree of impregnation;

degree of sintering; delaminations; density; dimensions; elastic moduli; grain size; inclusions;

mechanical degradation; misalignment; porosity; radiation degradation; structure of composites; surfacestress; tensile, shear and compressive strength; disbonds; wear

Thermal and infrared anisotropy, bonding; composition; emissivity; heat contours; plating thickness; porosity; reflectivity; stress;

thermal conductivity; thickness; voids; cracks; delaminations; heat treatment; state of cure; moisture;corrosion

Chemical and analytical alloy identification; composition; cracks; elemental analysis and distribution; grain size; inclusions;

macrostructure; porosity; segregation; surface anomalies

Auxiliary Categories

Image generation dimensional variations; dynamic performance; anomaly characterization and definition; anomaly

distribution; anomaly propagation; magnetic field configurationsSignal image analysis data selection, processing and display; anomaly mapping, correlation and identification; image

enhancement; separation of multiple variables; signature analysis

or component For example, if surfacecracks must be detected and eliminatedand the object or component is made offerromagnetic material, then magneticparticle testing would be the obviouschoice If that same material is aluminum

or titanium, then the choice would beliquid penetrant or electromagnetictesting However, for either of these

situations, if internal discontinuities were

to be detected, then ultrasonic testing orradiography would be the selection Theexact technique in either case woulddepend on the thickness and nature ofthe material and the types of

discontinuities that must be detected

T ABLE 2 Objectives of nondestructive testing methods.

Objectives Attributes Measured or Detected

Discontinuites and separations

Surface anomalies roughness; scratches; gouges; crazing; pitting; inclusions and imbedded foreign material

Surface connected anomalies cracks; porosity; pinholes; laps; seams; folds; inclusions

Internal anomalies cracks; separations; hot tears; cold shuts; shrinkage; voids; lack of fusion; pores; cavities; delaminations;

disbonds; poor bonds; inclusions; segregations

Structure

Microstructure molecular structure; crystalline structure and/or strain; lattice structure; strain; dislocation; vacancy;

deformationMatrix structure grain structure, size, orientation and phase; sinter and porosity; impregnation; filler and/or reinforcement

distribution; anisotropy; heterogeneity; segregationSmall structural anomalies leaks (lack of seal or through-holes); poor fit; poor contact; loose parts; loose particles; foreign objectsGross structural anomalies assembly errors; misalignment; poor spacing or ordering; deformation; malformation; missing parts

Dimensions and metrology

Displacement; position linear measurement; separation; gap size; discontinuity size, depth, location and orientation

Dimensional variations unevenness; nonuniformity; eccentricity; shape and contour; size and mass variations

Thickness; density film, coating, layer, plating, wall and sheet thickness; density or thickness variations

Physical and mechanical properties

Electrical properties resistivity; conductivity; dielectric constant and dissipation factor

Magnetic properties polarization; permeability; ferromagnetism; cohesive force

Thermal properties conductivity; thermal time constant and thermoelectric potential; diffusivity; effusivity; specific heat

Mechanical properties compressive, shear and tensile strength (and moduli); Poisson’s ratio; sonic velocity; hardness; temper and

embrittlementSurface properties color; reflectivity; refraction index; emissivity

Chemical composition and analysis

Elemental analysis detection; identification, distribution and/or profile

Impurity concentrations contamination; depletion; doping and diffusants

Metallurgical content variation; alloy identification, verification and sorting

Physiochemical state moisture content; degree of cure; ion concentrations and corrosion; reaction products

Stress and dynamic response

Stress; strain; fatigue heat treatment, annealing and cold work effects; residual stress and strain; fatigue damage and life (residual)Mechanical damage wear; spalling; erosion; friction effects

Chemical damage corrosion; stress corrosion; phase transformation

Other damage radiation damage and high frequency voltage breakdown

Dynamic performance crack initiation and propagation; plastic deformation; creep; excessive motion; vibration; damping; timing of

events; any anomalous behavior

Signature analysis

Electromagnetic field potential; strength; field distribution and pattern

Thermal field isotherms; heat contours; temperatures; heat flow; temperature distribution; heat leaks; hot spots; contrastAcoustic signature noise; vibration characteristics; frequency amplitude; harmonic spectrum and/or analysis; sonic and/or

ultrasonic emissionsRadioactive signature distribution and diffusion of isotopes and tracers

Signal or image analysis image enhancement and quantization; pattern recognition; densitometry; signal classification, separation;

and correlation; discontinuity identification, definition (size and shape) and distribution analysis;

discontinuity mapping and display

Value of Nondestructive Testing

The contribution of nondestructivetesting to profits has been acknowledged

in the medical field and computer andaerospace industries However, inindustries such as heavy metals, thoughnondestructive testing may be reluctantlyaccepted its contribution to profits maynot be obvious to management

Nondestructive testing is sometimesthought of only as a cost item Onepossible reason is industry downsizing

When a company cuts costs, twovulnerable areas are quality and safety

When bidding contract work, companiesadd profit margin to all cost items,including nondestructive testing, so aprofit should be made on the

nondestructive testing However, whenproduction is going poorly and it isanticipated that a job might lose money,

it seems like the first corner thatproduction personnel will try to cut isnondestructive testing This is

accomplished by subtle pressure onnondestructive testing technicians toaccept a product that does not quite meet

a code or standard requirement Theattitude toward nondestructive testing isgradually improving as managementcomes to appreciate its value

Nondestructive testing should be used

as a control mechanism to ensure thatmanufacturing processes are within designperformance requirements It shouldnever be used in an attempt to obtainquality in a product by using

nondestructive testing at the end of amanufacturing process This approach willultimately increase production costs

When used properly, nondestructivetesting saves money for the manufacturer

Rather than costing the manufacturermoney, nondestructive testing should addprofits to the manufacturing process

Overview of Nondestructive Testing Methods

To optimize the use of nondestructivetesting, it is necessary first to understandthe principles and applications of all themethods This book features radiographictesting (Fig 3) — only one of the

nondestructive testing methods Severalother methods and the applicationsassociated with them are briefly describednext

Visual Testing

Principles Visual testing (Fig 4) is the

observation of a test object, either directlywith the eyes or indirectly using opticalinstruments, by an inspector to evaluatethe presence of surface anomalies and theobject’s conformance to specification

Visual testing should be the firstnondestructive testing method applied to

an item The test procedure is to clean thesurface, provide adequate illuminationand observe A prerequisite necessary forcompetent visual testing of an item isknowledge of the manufacturing processes

by which it was made, its service history,potential failure modes and relatedindustry experience

Applications Visual testing provides a

means of detecting and examining avariety of surface discontinuities It is also

F IGURE 4 Visual test using borescope to

view interior of cylinder

F IGURE 3 Representative setup for radiographic test.

Radiation source

Specimen Void

Discontinuity images Image plane

the most widely used method fordetecting and examining for surfacediscontinuities associated with variousstructural failure mechanisms Even whenother nondestructive tests are performed,visual tests often provide a usefulsupplement For example, when the eddycurrent testing of process tubing isperformed, visual testing is oftenperformed to verify and more closelyexamine the surface condition Thisverification process can impact theevaluation process associated with othernondestructive test methods being used.

The following discontinuities may bedetected by a simple visual test: surfacediscontinuities, cracks, misalignment,warping, corrosion, wear and physicaldamage

Liquid Penetrant Testing

Principles Liquid penetrant testing (Fig 5)

reveals discontinuities open to thesurfaces of solid and nonporous materials

Indications of a wide spectrum ofdiscontinuity sizes can be found regardless

of the configuration of the workpiece andregardless of discontinuity orientations

Liquid penetrants seep into various types

of minute surface openings by capillaryaction The cavities of interest can be verysmall, often invisible to the unaided eye

The ability of a given liquid to flow over asurface and enter surface cavities dependsprincipally on the following: cleanliness

of the surface, surface tension of theliquid, configuration of the cavity, contactangle of the liquid, ability of the liquid towet the surface, cleanliness of the cavityand size of surface opening of the cavity

Applications The principal industrial uses

of liquid penetrant testing are finaltesting, receiving testing, in-processtesting and quality control, maintenanceand overhaul in the transportationindustries, in plant and machinerymaintenance and in testing of largecomponents The following are some ofthe typically detected discontinuities:

surface discontinuities, seams, cracks, laps,porosity and leak paths

Magnetic Particle Testing

Principles Magnetic particle testing is a

method of locating surface and slightlysubsurface discontinuities in

ferromagnetic materials It depends on thefact that when the material or part undertest is magnetized, discontinuities that lie

in a direction generally transverse to thedirection of the magnetic field will cause aleakage field to be formed at and abovethe surface of the part The presence ofthis leakage field and therefore thepresence of the discontinuity is detected

by the use of finely divided ferromagneticparticles applied over the surface, withsome of the particles being gathered andheld to form an outline of the

discontinuity This generally indicates itslocation, size, shape and extent Magneticparticles are applied over a surface as dryparticles or as wet particles in a liquidcarrier such as water or oil

Applications The principal industrial uses

of magnetic particle testing are for final,receiving and in-process testing; forquality control; for maintenance andoverhaul in the transportation industries;

for plant and machinery maintenance;

and for testing of large components Some

of the typically detected discontinuitiesare surface discontinuities, seams, cracksand laps

Eddy Current Testing

Principles Based on electromagnetic

induction, eddy current testing (Fig 6) isused to identify or differentiate among a

F IGURE 5 Liquid penetrant indication of

cracking

F IGURE 6 Representative setup for eddy current test.

Coil in eddy current probe Primary electromagnetic field

Direction of primary current

Eddy current strength decreases with increasing depth

Direction of eddy currents Conducting specimen

Induced field

wide variety of physical, structural andmetallurgical conditions in electricallyconductive ferromagnetic and

nonferromagnetic metals and metal parts

The method is based on indirectmeasurement and on correlation betweenthe instrument reading and the structuralcharacteristics and serviceability of theparts being examined

With a basic system, the part is placedwithin or adjacent to an electric coil inwhich high frequency alternating current

is flowing This excitation current

establishes an electromagnetic field

around the coil This primary field causes

eddy current to flow in the part because

of electromagnetic induction Inversely,the eddy currents affected by allcharacteristics (conductivity, permeability,thickness, discontinuities and geometry)

of the part create a secondary magnetic

field that opposes the primary field Theresults of this interaction affect the coilvoltage and can be displayed in a variety

of methods

Eddy currents flow in closed loops inthe part or air Their two most importantcharacteristics, amplitude and phase, areinfluenced by the arrangement andcharacteristics of the instrumentation andtest piece For example, during the test of

a tube the eddy currents flowsymmetrically in the tube whendiscontinuities are not present However,when a crack is present, then the eddycurrent flow is impeded and changed indirection, causing significant changes inthe associated electromagnetic field

Applications An important industrial use

of eddy current testing is on heatexchanger tubing For example, eddycurrent testing is often specified for thinwall tubing in pressurized water reactors,steam generators, turbine condensers andair conditioning heat exchangers Eddycurrent testing is also used often inaircraft maintenance The following aresome of the typical material

characteristics that can be evaluated byeddy current testing: cracks, inclusions,dents and holes; grain size and hardness;

coating and material thickness;

dimensions and geometry; composition,conductivity or permeability; and alloycomposition

Ultrasonic Testing

Principles Ultrasonic testing (Fig 7) is a

nondestructive method in which beams ofsound waves at a frequency too high tohear are introduced into materials for thedetection of surface and subsurfacediscontinuities in the material Theseacoustic waves travel through the materialwith some attendant loss of energy(attenuation) and are reflected atinterfaces The reflected beam is displayed(or reduces the display of transmittedsound) and is then analyzed to define thepresence and locations of discontinuities

or discontinuities

Applications Ultrasonic testing of metals

is widely used, principally for thedetection of discontinuities This methodcan be used to detect internal

F IGURE 7 Representative setups for ultrasonic testing: (a) longitudinal wave technique; (b) shear wave

technique

Transducer

Crack

Bolt Time Crack

Back surface

Crack

Entry surface Crack

Skip distance

discontinuities in most engineeringmetals and alloys Bonds produced bywelding, brazing, soldering and adhesivebonding can also be ultrasonicallyexamined Inline techniques have beendeveloped for monitoring and classifyingmaterials as acceptable, salvageable orscrap and for process control Otherapplications include testing of piping andpressure vessels, nuclear systems, motorvehicles, machinery, structures, railroadrolling stock and bridges and thicknessmeasurement.

Leak Testing

Principles Leak testing is concerned with

the flow of liquids or gases frompressurized or into evacuated components

or systems intended to hold fluids Theprinciples of leak testing involve thephysics of fluid (liquids or gases) flowingthrough a barrier where a pressuredifferential or capillary action exists

Leaking fluids (liquid or gas) canpropagate from inside a component orassembly to the outside, or vice versa, as aresult of a pressure differential betweenthe two regions or as a result ofpermeation through a barrier Theimportance of leak testing depends on thesize of the leak and on the medium beingleaked Leak testing encompasses

procedures that fall into these basicfunctions: leak location, leakagemeasurement and leakage monitoring

Applications Like other forms of

nondestructive testing, leak testing has agreat impact on the safety and

performance of a product Reliable leaktesting decreases costs by reducingnumber of reworked products, warrantyrepairs and liability claims The mostcommon reasons for performing a leaktest are to prevent the loss of costlymaterials or energy; to preventcontamination of the environment; toensure component or system reliability;

and to prevent the potential for anexplosion or fire

Acoustic Emission Testing

Principles Acoustic emissions are stress

waves produced by sudden movement instressed materials The classic source ofacoustic emission is discontinuity relateddeformation processes such as crackgrowth and plastic deformation Suddenmovement at the source produces a stresswave that radiates out into the structureand excites a sensitive piezoelectric sensor

As the stress in the material is raised,emissions are generated The signals fromone or more sensors are amplified andmeasured to produce data for display andinterpretation

The source of acoustic emission energy

is the elastic stress field in the material

Without stress, there is no emission

Therefore, an acoustic emission test(Fig 8) is usually carried out during acontrolled loading of the structure Thiscan be a proof load before service; acontrolled variation of load while thestructure is in service; a fatigue, pressure

or creep test; or a complex loadingprogram Often, a structure is going to beloaded hydrostatically anyway duringservice and acoustic emission testing isused because it gives valuable additionalinformation about the expected

performance of the structure under load

Other times, acoustic emission testing isselected for reasons of economy or safetyand a special loading procedure isarranged to meet the needs of the acousticemission test

Applications Acoustic emission is a

natural phenomenon occurring in thewidest range of materials, structures andprocesses The largest scale eventsobserved with acoustic emission testingare seismic and the smallest are smalldislocations in stressed metals

The equipment used is highly sensitive

to any kind of movement in its operatingfrequency (typically 20 to 1200 kHz) Theequipment can detect not only crackgrowth and material deformation but also

F IGURE 8 Acoustic emission testing setup in which eight

sensors permit computer to calculate location of crackpropagation

Computer Preamplifier

Test object

Acoustic event

such process as solidification, friction,impact, flow and phase transformations.

Therefore, acoustic emission testing is alsoused for in-process weld monitoring,detecting tool touch and tool wear duringautomatic machining, detecting wear andloss of lubrication in rotating equipment,detecting loose parts and loose particles,detecting and monitoring leaks,

cavitation, flow, preservice proof testing,in-service weld monitoring and leaktesting

Infrared and Thermal Testing

Principles Conduction and convection

are the primary mechanisms of heattransfer in an object or system However,electromagnetic radiation is emitted from

a heated body when electrons in thatbody change to a lower energy state

Thermal testing involves themeasurement or mapping of surfacetemperatures when heat flows from, to orthrough a test object Temperaturedifferentials on a surface, or changes insurface temperature with time, are related

to heat flow patterns and can be used todetect anomalies or to determine the heattransfer characteristics of an object Forexample, during the operation of anelectrical breaker, a hot spot detected at

an electrical termination may be caused

by a loose or corroded connection (seeFig 9) The resistance to electrical flow

through the connection produces anincrease in surface temperature of theconnection

Applications There are two basic

categories of infrared and thermal testapplications: electrical and mechanical

The specific applications within these twocategories are numerous Electricalapplications include transmission anddistribution lines, transformers,disconnects, switches, fuses, relays,breakers, motor windings, capacitorbanks, cable trays, bus taps and othercomponents and subsystems Mechanicalapplications include insulation (in boilers,furnaces, kilns, piping, ducts, vessels,refrigerated trucks and systems, tank carsand elsewhere), friction in rotatingequipment (bearings, couplings, gears,gearboxes, conveyor belts, pumps,compressors and other components) andfluid flow (steam lines; heat exchangers;

tank fluid levels; exothermic reactions;

heating, ventilation and air conditioningsystems; leaks above and below ground;

cooling and heating; tube blockages;

systems; environmental assessment ofthermal discharge; boiler or furnace airleakage; condenser; turbine air leakage;

pumps; compressors; and other systemapplications)

Other Methods

There are many other methods ofnondestructive testing, including opticalmethods such as holography,

shearography and moiré imaging; materialidentification methods such as chemicalspot testing, spark testing and

spectroscopy; strain gaging; and acousticmethods such as vibration analysis andtapping

F IGURE 9 Infrared thermography of

automatic transfer switches of emergencydiesel generator Hot spots appear bright inthermogram

Radiography may be considered the mosteffective nondestructive testing methodmerely because of its universal use andacceptance in industry Radiography can

be used to test most types of solidmaterial Exceptions include materials ofvery high or very low density Neutronradiography, however, can often be used

in such cases There is wide latitude both

of material thickness that can be testedand in the techniques that can be used

Usually conditions that result in a twopercent or greater difference inthrough-section thickness can usually bedetected

Radiography has three mainadvantages: (1) detection of internaldiscontinuities, (2) detection of significantvariations in composition and

(3) permanent record of test data

Compared to other nondestructive testmethods, radiography can be expensive

Large capital costs and space allocationsmay be required for radiographicactivities Cost may be reduced ifequipment of smaller size or lower energyrequirement can be used The magnitude

of potential test activities, however, must

be considered before limits are placed onthe test facility

There are three major limiting factorsthat must be considered before

radiography becomes the method ofchoice

1 Discontinuity detection depends onradiation beam orientation In general,radiography can detect only featuresthat have a thickness change in adirection parallel to the radiationbeam

2 Radiography typically involves thetransmission of radiation through thepart or component, in which caseboth sides of the part must beaccessible

3 Radiation safety is always necessary to

a successful operation

In addition, radiographic images (inthe form of film or digital images) mayneed to be stored for years to comply withquality assurance or regulatory

requirements

Management of Radiographic Testing Programs

Management of a radiographic testingprogram will require consideration ofmany items before a program can producethe desired results Six basic questionsmust be answered before a true directioncan be charted They are as follows

1 Are regulatory requirements in placethat mandate program characteristics?

2 What is the magnitude of the programthat will provide desired results?

3 What provisions must be made forpersonnel safety and for compliancewith environmental regulations?

4 What is the performance date for aprogram to be fully implemented?

5 Is there a cost benefit of radiographictesting?

6 What are the available resources inpersonnel and money?

Once these questions are answered, then arecommendation can be made to

determine the best path forward Threeprimary paths are (1) service companies,(2) consultants and (3) in-house programs

Though these are primary paths, someprograms may on a routine or onas-needed bases require support personnelfrom a combination of two or more ofthese sources Before a final decision ismade, advantages and disadvantages ofeach path must be considered Therefore,the following are details that must beconsidered

Service Companies

1 Who will identify the componentswithin the facility to be examined?

2 Will the contract be for time and

materials or have a specific scope of work?

3 If a time and materials contract is

awarded, who will monitor the timeand materials charged?

4 If a scope of work is required, who is

technically qualified to develop andapprove it?

5 What products or documents (testreports, trending, recommendations,root cause analysis and others) will beprovided once the tests are completed?

P ART 2 Management of Radiographic Testing

6 Who will evaluate and accept theproduct (test reports, trending,recommendations, root cause analysisand others) within your company?

7 Do the service company workerspossess qualifications andcertifications required by contract and

by applicable regulations? Will othercontractors be required to take care ofrelated matters such as radiationsafety?

8 Do the service company workersrequire site specific training (confinedspace entry, electrical safety, hazardousmaterials and others) or clearance toenter and work in the facility?

9 If quantitative tests are performed, doprogram requirements mandateequipment calibration?

10 Does the service company retain anyliability for test results?

Consultants

1 Will the contract be for time and

materials or have a specific scope of work?

2 If a scope of work is required, who is

technically qualified to develop andapprove it?

3 Who will identify the requiredqualifications of the consultant?

4 Is the purpose of the consultant todevelop or update a program or is it tooversee and evaluate the performance

7 Who will evaluate the consultant’sperformance (test reports, trending,recommendations, root cause analysisand other functions) within yourcompany?

8 Does the consultant possessqualifications and certificationsrequired by contract and by applicableregulations?

9 Does the consultant require sitespecific training (confined space entry,electrical safety, hazardous materialsand others) or clearance to enter andwork in the facility?

10 Does the consultant retain anyliability for test results?

In-House Programs

1 Who will determine the scope of theprogram? Will the radiation source beisotopes or X-ray machines? Will theimages be recorded on film or ondigital media?

2 What are the regulatory requirements(codes and standards) associated withprogram development and

implementation?

3 Who will develop a cost benefit

analysis for the program?

4 How much time and resources areavailable to establish the program?

5 What are the qualificationrequirements (education, training,experience and others) for personnel?

5 Do program personnel requireadditional training (radiological safety,confined space entry or others) orqualifications?

6 Are subject matter experts required toprovide technical guidance duringpersonnel development?

7 Are procedures required to performwork in the facility?

8 If procedures are required, who willdevelop, review and approve them?

9 Who will determine the technicalspecifications for test equipment?

Test Procedures for Radiographic Testing

The conduct of facility operations(in-house or contracted) should beperformed in accordance with specificinstructions from an expert This istypically accomplished using writteninstructions in the form of a technicalprocedure In many cases codes andspecifications will require the use of atechnical procedure to perform requiredtests

The procedure process can take manyforms, including general instructions thataddress only major aspects of test

techniques Or a procedure may bewritten as a step-by-step process requiring

a supervisor’s initial or signature aftereach step The following is a typicalformat for an industrial procedure

1 The purpose identifies the intent of the

procedure

2 The scope establishes the latitude of

items, tests and techniques coveredand not covered by the procedure

3 References are specific documents from

which criteria are extracted ordocuments satisfied byimplementation of the procedure

4 Definitions are needed for terms and

abbreviations that are not commonknowledge to people who will read theprocedure

5 Statements about personnel requirements

address specific requirements toperform tasks in accordance with theprocedure — issues such as personnelqualification, certification, accessclearance and others

6 Equipment characteristics, calibration

requirements and model numbers ofqualified equipment must be specified

7 Safety issues must be addressed because

of the nature of penetrating radiation

8 The test procedure provides a sequential

process to be used to conduct testactivities

9 Acceptance criteria establish component

characteristics that will identify theitems suitable for service

10 Reports (records) provide the means to

document specific test techniques,equipment used, personnel performingactivity, date performed, test results,compliance with environmentalregulations and safety procedures

11 Attachments may include (if required)

items such as report forms, instrumentcalibration forms, qualified equipmentmatrix, schedules and others

Once the procedure is completed,typically an expert in the subject matterperforms a technical evaluation If theprocedure is deemed adequate (meetingidentified requirements), the expert willapprove it for use Some codes andstandards also require the procedure to bequalified — that is, demonstrated to thesatisfaction of a representative of aregulatory body or jurisdictionalauthority

Test Specifications for Radiographic Testing

A radiographic specification mustanticipate a number of issues that ariseduring testing

Source Selection

The radiation source requirements (energylevel, intensity and physical size) to detectthe target discontinuities must be

determined

1 The selected means of imaging maydictate source energy and intensitylevels

2 The radiation source may need to bemobile for use in various locations

3 The energy level (ability to penetrate)

of the radiation sources affectsradiographic contrast Radiographiccontrast is an element of imagesensitivity

4 The physical size of the radiationemitting surface affects the geometricunsharpness of the radiographicimage

5 High energy levels may increase safetyissues because of increased shieldingrequirements

6 The source intensity (total quantity ofpenetrating rays) will directly affectthe exposure time Increased exposuretime may affect safety requirements

an image in real time

1 The first consideration is the ability todetect discontinuities of interest

2 Examination environment

3 Image handling requirements includeprovisions for processing, evaluationand transmitting of images

Interpretation

Interpretation may be complex Theinterpreter must have a knowledge of thefollowing: (1) the radiographic process(radiation source, exposure technique,image storage system and other meansused to obtain the image); (2) the itembeing examined (its configuration,material characteristics, fabricationprocess, potential discontinuities andother aspects); and (3) the acceptancecriteria

Standards and Specifications for Radiographic Testing

Standards have undergone a process ofpeer review in industry and can beinvoked with the force of law by contract

or by government regulation In contrast,

a specification represents an employer’sinstructions to employees and is specific

to a contract or work place Specificationsmay form the basis of standards through areview process Standards and

specifications exist in three basic areas:equipment, processes and personnel

1 Standards for equipment includecalibrated electronic radiation sourcesand isotope sources Standardizedreference objects such as image qualityindicators (penetrameters), calibrateddensity strips and radiation surveymeters would also fit into thiscategory

2 ASTM International and otherorganizations publish standards fortest techniques Some other standardsare for quality assurance proceduresand are not specific to a test method

or even to testing in general Tables 3and 4 list some of the standards used

in radiographic testing A source fornondestructive testing standards is the

Annual Book of ASTM Standards.5

3 Qualification and certification of testpersonnel are discussed below, withspecific reference to recommendations

of ASNT Recommended Practice No.

SNT-TC-1A.4

Personnel Qualification and Certification

One of the most critical aspects of the testprocess is the qualification of test

personnel Nondestructive testing is

sometimes referred to as a special process.

The term simply means that it is verydifficult to determine the adequacy of atest by merely observing the process orthe documentation generated at itsconclusion The quality of the test islargely dependent on the skills andknowledge of the inspector

The American Society forNondestructive Testing (ASNT) has been aworld leader in the qualification andcertification of nondestructive testingpersonnel for many years By 1999, theAmerican Society for NondestructiveTesting had instituted three majorprograms in place for the qualificationand certification of nondestructive testingpersonnel

1 ASNT Recommended Practice

No SNT-TC-1A provides guidelines for

personnel qualification andcertification in nondestructive testing

This recommended practice identifiesthe specific attributes that should beconsidered when qualifying

nondestructive testing personnel Itrequires the employer to develop and

implement a written practice

(procedure) that details the specificprocess and any limitation in thequalification and certification ofnondestructive testing personnel.4

2 ANSI/ASNT CP-189, Standard for

Qualification and Certification of Nondestructive Testing Personnel

resembles SNT-TC-1A but alsoestablishes specific attributes for thequalification and certification ofnondestructive testing personnel

However, CP-189 is a consensusstandard as defined by the AmericanNational Standards Institute (ANSI) It

is recognized as the American standardfor nondestructive testing It is not

considered a recommended practice; it is

a national standard.6

3 The ASNT Central Certification Program

(ACCP), unlike SNT-TC-1A and

CP-189, is a third party certificationprocess Currently it has identifiedqualification and certificationattributes for Level II and Level IIInondestructive testing personnel TheAmerican Society for NondestructiveTesting certifies that the individual hasthe skills and knowledge for manynondestructive testing methodapplications It does not remove theresponsibility for the final

determination of personnelqualifications from the employer Theemployer evaluates an individual’sskills and knowledge for application ofcompany procedures using designatedtechniques and identified equipmentfor specific tests.7

SNT-TC-1A (For the purpose of thisdiscussion the quantities cited are thosethat address radiographic testing only.)

Scope This recommended practice has

been prepared to establish guidelines forthe qualification and certification ofnondestructive testing personnel whosespecific jobs require appropriateknowledge of the technical principlesunderlying the nondestructive test theyperform, witness, monitor or evaluate

This document provides guidelines for theestablishment of a qualification andcertification program

Written Practice The employer shall

establish a written practice for the controland administration of nondestructivetesting personnel training, examinationand certification The employer’s writtenpractice should describe the responsibility

of each level of certification fordetermining the acceptability of materials

or components in accordance withapplicable codes, standards, specificationsand procedures

Table 3 Some radiographic standards published by ASTM International.

C 638-92 (1997), Standard Descriptive Nonmenclature of Constituents of Aggregates for Radiation-Shielding Concrete

E 94-00, Standard Guide for Radiographic Examination

E 155-00, Standard Reference Radiographs for Inspection of Aluminum and Magnesium Castings

E 170-99e1, Standard Terminology Relating to Radiation Measurements and Dosimetry

E 186-98, Standard Reference Radiographs for Heavy-Walled (2 to 4 1/2-in [51 to 114-mm]) Steel Castings

E 192-95 (1999), Standard Reference Radiographs for Investment Steel Castings of Aerospace Applications

E 242-95 (2000), Standard Reference Radiographs for Appearances of Radiographic Images as Certain Parameters Are Changed

E 272-99, Standard Reference Radiographs for High-Strength Copper-Base and Nickel-Copper Alloy Castings

E 280-98, Standard Reference Radiographs for Heavy-Walled (4 1/2 to 12-in [(114 to 305-mm]) Steel Castings

E 310-99, Standard Reference Radiographs for Tin Bronze Castings

E 390-95, Standard Reference Radiographs for Steel Fusion Welds

E 431-96, Standard Guide to Interpretation of Radiographs of Semiconductors and Related Devices

E 446-98, Standard Reference Radiographs for Steel Castings Up to 2 in (51 mm) in Thickness

E 505-96, Standard Reference Radiographs for Inspection of Aluminum and Magnesium Die Castings

E 592-99, Standard Guide to Obtainable ASTM Equivalent Penetrameter Sensitivity for Radiography of Steel Plates 1/4 to 2 in (6 to 51 mm) Thick

with X Rays and 1 to 6 in (25 to 152 mm) Thick with Cobalt-60

E 666-97, Standard Practice for Calculating Absorbed Dose from Gamma or X Radiation

E 689-95 (1999), Standard Reference Radiographs for Ductile Iron Castings

E 746-02, Standard Test Method for Determining Relative Image Quality Response of Industrial Radiographic Film

E 747-97, Standard Practice for Design, Manufacture and Material Grouping Classification of Wire Image Quality Indicators (IQI) Used for Radiology

E 748-95, Standard Practices for Thermal Neutron Radiography of Materials

E 801 (2001), Standard Practice for Controlling Quality of Radiological Examination of Electronic Devices

E 802-95 (1999), Standard Reference Radiographs for Gray Iron Castings Up to 4 1/2 in [114 mm]) in Thickness

E 803, Standard Test Method for Determining the L/D Ratio of Neutron Radiography Beams

E 975-00, Standard Practice for X-Ray Determination of Retained Austenite in Steel with Near Random Crystallographic Orientation

E 999-99, Standard Guide for Controlling the Quality of Industrial Radiographic Film Processing

E 1000-98, Standard Guide for Radioscopy

E 1025-98, Standard Practice for Design, Manufacture, and Material Grouping Classification of Hole-Type Image Quality Indicators (IQI) Used for Radiology

E 1030-00, Standard Test Method for Radiographic Examination of Metallic Castings

E 1032-95, Standard Test Method for Radiographic Examination of Weldments

E 1114-92 (1997), Standard Test Method for Determining the Focal Size of Iridium-192 Industrial Radiographic Sources

E 1161-95, Standard Test Method for Radiologic Examination of Semiconductors and Electronic Components

E 1165-92 (2002), Standard Test Method for Measurement of Focal Spots of Industrial X-Ray Tubes by Pinhole Imaging

E 1254-98, Standard Guide for Storage of Radiographs and Unexposed Industrial Radiographic Films

E 1255-96, Standard Practice for Radioscopy

E 1320-00, Standard Reference Radiographs for Titanium Castings

E 1390-90 (2000), Standard Guide for Illuminators Used for Viewing Industrial Radiographs

E 1411-95, Standard Practice for Qualification of Radioscopic Systems

E 1441-00, Standard Guide for Computed Tomography (CT) Imaging

E 1453-93 (1996), Standard Guide for Storage of Media That Contains [sic] Analog or Digital Radioscopic Data

E 1475-97, Standard Guide for Data Fields for Computerized Transfer of Digital Radiological Test Data

E 1496-97, Standard Test Method for Neutron Radiographic Dimensional Measurements

E 1570-00, Standard Practice for Computed Tomographic (CT) Examination

E 1647-98a, Standard Practice for Determining Contrast Sensitivity in Radioscopy

E 1648-95 (2001), Standard Reference Radiographs for Examination of Aluminum Fusion Welds

E 1672-95 (2001), Standard Guide for Computed Tomography (CT) System Selection

E 1734-98, Standard Practice for Radioscopic Examination of Castings

E 1735, Standard Test Method for Determining Relative Image Quality of Industrial Radiographic Film Exposed to X-Radiation from 4 to 25 MV

E 1742-00, Standard Practice for Radiographic Examination

E 1814-96, Standard Practice for Computed Tomographic (CT) Examination of Castings

E 1815-96 (2001), Standard Test Method for Classification of Film Systems for Industrial Radiography

E 1894-97, Standard Guide for Selecting Dosimetry Systems for Application in Pulsed X-Ray Sources

E 1931-97, Standard Guide for X-Ray Compton Scatter Tomography

E 1936-97, Standard Reference Radiograph for Evaluating the Performance of Radiographic Digitization Systems

E 1955-98, Standard Radiographic Examination for Soundness of Welds in Steel by Comparison to Graded ASTM E 390 Reference Radiographs

E 2002-98, Standard Practice for Determining Total Image Unsharpness in Radiology

E 2033-99, Standard Practice for Computed Radiology (Photostimulable Luminescence Method)

E 2116-00, Standard Practice for Dosimetry for a Self-Contained Dry-Storage Gamma-Ray Irradiator

F 629-97, Standard Practice for Radiography of Cast Metallic Surgical Implants

F 947-85 (1996), Standard Test Method for Determining Low-Level X-Radiation Sensitivity of Photographic Films

F 1035-91 (1997), Standard Practice for Use of Rubber-Cord Pie Disk to Demonstrate the Discernment Capability of a Tire X-Ray Imaging System

T ABLE 4 Some standards and practices for radiographic testing and for radiation safety.

Issuing Organization Representative Standards and Related Documents

American National Standards Institute ANSI N43.9-1991, Gamma Radiography — Specifications for Design and Test of Apparatus

(revision and redesignation of ANSI N432-1980)

ANSI PH2.8-1975, Sensitometry of Industrial X-Ray Films for Energies up to 3 Million Electron

Volts, Method for.

See also ASME and ASNT

American Society of Mechanical Engineers ANSI/ASME B31.1, Power Piping

ANSI/ASME B31.3, Process Piping ASME Boiler and Pressure Vessel Code: Section I — Power Boilers ASME Boiler and Pressure Vessel Code: Section III — Components ASME Boiler and Pressure Vessel Code: Section V — Power Boilers ASME Boiler and Pressure Vessel Code: Section VIII — Pressure Vessels ASME Boiler and Pressure Vessel Code: Section XI — Inservice Inspection of Nuclear Vessels ASME PTC 19-1, Performance Test Codes, Supplement on Instruction and Apparatus

American Society for Nondestructive Testing ASNT Recommended Practice No SNT-TC-1A

ANSI/ASNT CP-189, ASNT Standard for Qualification and Certification of Nondestructive Testing

American Water Works Association AWWA D100-96, Welded Steel Tanks for Water Storage

American Welding Society AWS D1.1, Structural Welding Code — Steel

AWS D1.5, Bridge Welding Code

Canadian General Standards Board CAN/CGSB-48-GP-2M, Spot Radiography of Welded Butt Joints in Ferrous Materials

CAN/CGSB-48.3-92, Radiographic Testing of Steel Castings CAN/CGSB-48.5-95, Manual on Industrial Radiography CAN/CGSB-48.9712-95, Non-Destructive Testing — Qualification and Certification of Personnel

Deutsche Institut für Normung DIN 6814, Terms and Definitions in the Field of Radiological Techniques

DIN 6832-2, Radiographic Cassettes; Test for Light-Proofness and Test for Contact between

Radiographic Film and Intensifying Screen

DIN 25 430, Safety Marking in Radiation Protection DIN 54 115, Non-Destructive Testing; Radiation Protection Rules for the Technical Application of

Sealed Radioactive Sources

DIN EN 444, Non-Destructive Testing; General Principles for the Radiographic Examination of

Metallic Materials Using X-Rays and Gamma-Rays

DIN EN 12 681, Founding — Radiographic Inspection DIN EN 14 096, Non-Destructive Testing - Qualification of Radiographic Film Digitisation Systems

European Committee for Standardization CEN 584, Non Destructive Testing — Industrial Radiographic Film

EN 12 679, Non-Destructive Testing — Determination of the Size of Industrial Radiographic

Sources — Radiographic Method

International Organization for Standardization ISO 2504, Radiography of Welds and Viewing Conditions for Films — Utilization of

Recommended Patterns of Image Quality Indicators (I.Q.I.)

ISO 7004, Photography — Industrial Radiographic Film — Determination of ISO Speed and

Average Gradient When Exposed to X- and Gamma-Radiation

ISO 3999, Apparatus for Gamma Radiography ISO 9712, Nondestructive Testing — Qualification and Certification of Personnel ISO 9915, Aluminium Alloy Castings — Radiography Testing

ISO 11 699, Non-Destructive Testing — Industrial Radiographic Films

Japanese Standards Association K 7091, Testing Method for Radiography of Carbon Fibre Reinforced Plastic Panels Edition 1

K 7521, Dimensions for Photographic Film in Sheets and Rolls for Medical, Industrial and Dental

Radiography

Z 4560, Industrial Gamma-Ray Apparatus for Radiography

Korean Standards Association A 4907, Film Marker of Radiography

A 4921, Industrial X-Ray Apparatus for Radiography

M 3910, Dimensions for Photographic Film in Sheets and Rolls for Medical, Industrial and Dental

Radiography

National Council on Radiation Protection NCRP 61, Radiation Safety Training Criteria for Industrial Radiography Occupational Safety and Health Administration 29 CFR 1910, Occupational Safety and Health Standards [Code of Federal Regulations:

Title 29, Labor]

Society of Automotive Engineers SAE AMS 2635C, Radiographic Inspection

SAE ARP 1611A, Quality Inspection Procedure, Composites, Tracer Fluoroscopy and Radiography SAE AS 1613A, Image Quality Indicator, Radiographic

SAE AS 7114/4, NADCAP Requirements for Nondestructive Testing Facility Radiography

Education, Training, Experience Requirements for Initial Qualification.

Candidates for certification innondestructive testing should havesufficient education, training andexperience to ensure qualification inthose nondestructive testing methods forwhich they are being considered forcertification Table 5 lists therecommended training and experiencefactors to be considered by the employer

in establishing written practices for initialqualification of Level I and II individualsfor radiographic testing

Training Programs Personnel being

considered for initial certification shouldcomplete sufficient organized training tobecome thoroughly familiar with theprinciples and practices of the specifiednondestructive test method related to thelevel of certification desired and

applicable to the processes to be used andthe products to be tested

Examinations For Level I and II

personnel, a composite grade should bedetermined by a simple averaging of theresults of the general, specific andpractical examinations described below

Examinations administered forqualification should result in a passingcomposite grade of at least 80 percent,with no individual examination having apassing grade less than 70 percent Theexamination for near vision acuity shouldensure natural or corrected near distanceacuity in at least one eye such thatapplicant can read a minimum of jaegersize 2 or equivalent type and size letter at

a distance of not less than 305 mm

(12 in.) on a standard jaeger test chart.This test should be administered annually

Written Examination for NDT Levels I and II The minimum number of

questions that should be administered inthe written examination for radiographictest personnel is as follows: 40 questions

in the general examination and 20 questions in the specific examination The

number of questions is the same for Level

I and Level II personnel

Practical Examination for NDT Level I and II The candidate should demonstrate

ability to operate the necessarynondestructive test equipment, recordand analyze the resultant information tothe degree required At least one selectedspecimen should be tested and the results

of the nondestructive test analyzed by thecandidate

Certification Certification of all levels of

nondestructive testing personnel is theresponsibility of the employer

Certification of nondestructive testingpersonnel shall be based on

demonstration of satisfactory qualification

in accordance with sections on education,training, experience and examinations, asmodified by the employer’s writtenpractice Personnel certification recordsshall be maintained on file by theemployer

Recertification All levels of

nondestructive testing personnel shall berecertified periodically in accordance withthe following: evidence of continuingsatisfactory performance; reexamination

in those portions of examination deemednecessary by the employer’s NDT Level III.Recommended maximum recertificationintervals are three years for Level I andLevel II and five years for Level III.These recommendations fromSNT-TC-1A are cited only to provide aflavor of the specific items that must beconsidered in the development of anin-house nondestructive testing program.However, if an outside agency is

contracted for radiographic test services,then the contractor must have aqualification and certification program tosatisfy most codes and standards

standards bodies Each ISO member body

interested in a subject for which atechnical committee has been established

T ABLE 5 Recommended training and experience for

radiographic testing personnel according to

ASNT Recommended Practice No SNT-TC-1A.4

Radiographic Testing

High school graduatea 39 h 40 h

Two years of collegeb 29 h 35 h

Work experiencec 3 mo 9 mo

Neutron Radiographic Testing

High school graduatea 28 h 40 h

Two years of collegeb 20 h 40 h

Work experiencec 6 mo 24 mo

a Or equivalent.

b Completion with a passing grade of at least two years of engineering or

science study in a university, college or technical school.

c Work time experience per level Note: for Level II certification, the

experience shall consist of time as Level I or equivalent If a person is

being qualified directly to Level II with no time at Level I, the required

experience shall consist of the sum of the times required for Level I and

Level II and the required training shall consist of the sum of the hours

required for Level I and Level II.

has the right to be represented on thatcommittee International organizations,governmental and nongovernmental, inliaison with the International

Organization for Standardization, alsotake part in the work

Technical Committee ISO/TC 135,Non-Destructive Testing Subcommittee

SC 7, Personnel Qualification, preparedinternational standard ISO 9712,

Nondestructive Testing – Qualification and Certification of Personnel.8In its statement

of scope, ISO 9712 states that it

“establishes a system for the qualificationand certification, by a certification body,

of personnel to perform industrialnondestructive testing (NDT) using any ofthe following methods: (a) eddy currenttesting; (b) liquid penetrant testing;

(c) magnetic particle testing; (d)radiographic testing; (e) ultrasonictesting” and that the “system described inthis International Standard may alsoapply to visual testing (VT), leak testing(LT), neutron radiography (NR), acousticemission (AE) and other nondestructivetest methods where independentcertification programs exist.” Theapplicability of ISO 9712 to radiographictesting therefore depends on activity ofthe national certifying body

Safety in Radiographic Testing

To manage a radiographic testingprogram, as with any test program, thefirst obligation is to ensure safe workingconditions The following are components

of a safety program that may be required

or at least deserve serious consideration

1 Identify the safety and operationalrules and codes applicable to the areas,equipment and processes beingexamined before work is to begin

2 Provide proper safety equipment(protective barriers, hard hat, safetyharnesses, steel toed shoes, hearingprotection and others)

3 Provide necessary training in radiationsafety

4 Before the test, perform a thoroughvisual survey to determine all thehazards and identify necessarysafeguards to protect test personneland equipment

5 Notify operative personnel to identifythe location and specific equipmentthat will be examined In addition, adetermination must be made if signs

or locks restrict access by personnel

Be aware of equipment that may beoperated remotely or may started bytime delay

6 Be aware of any potentially explosiveatmospheres Determine whether it issafe to take your equipment into thearea

7 Do not enter any roped off or no entry

areas without permission andapproval

8 When working on or around moving

or electrical equipment, remove pens,watches, rings or objects in yourpockets that may touch (or fall into)energized equipment

9 Know interplant communication andevacuation systems

10 Never let unqualified personneloperate equipment independentlyfrom qualified supervision

11 Keep a safe distance between you andany energized equipment In theUnited States, these distances can befound in documents from theOccupational Safety and HealthAdministration, the National Fire

Prevention Association (National

Electric Code),9the Institute ofElectrical and Electronics Engineers

(National Electrical Safety Code)10andother organizations

12 Be aware of the personnelresponsibilities before entering a

confined space All such areas must be

tested satisfactorily for gas and oxygenlevels before entry and periodicallythereafter If odors are noticed, orunusual sensations such as earaches,dizziness or difficulty in breathing areexperienced, leave the area

immediately

13 Notice that the safety considerationslisted above are applicable to manytest methods Because ionizingradiation can hurt people, additionalprecautions are needed for

radiographic testing and are discussed

in a separate chapter

Most facilities in the United States arerequired by law to follow the

requirements in the applicable standard

Two Occupational Safety and HealthStandards in the United States that should

be reviewed are Occupational Safety and

Health Standards for general industry11and

the Occupational Safety and Health

Standards for the Construction Industry.12Personnel safety is always the firstconsideration for every job

Ensuring Reliability of Test Results

When a test is performed, there are fourpossible outcomes: (1) a discontinuity can

be found when a discontinuity is present;

(2) a discontinuity can be missed evenwhen a discontinuity is present; (3) adiscontinuity can be found when none is

present; and (4) no discontinuity is foundwhen none is present A reliable testingprocess and a qualified inspector shouldfind all discontinuities of concern with nodiscontinuities missed (no errors as incase 2, above) and no false callouts(case 3, above).

To achieve this goal, the probability offinding a discontinuity must be high andthe inspector must be both proficient inthe testing process and motivated toperform a maximum efficiency A recklessinspector may accept parts that containdiscontinuities, with the resultantconsequences of possible inservice partfailure A conservative inspector mayreject parts that contain discontinuitiesbut the inspector also may reject partsthat do not contain discontinuities, withthe resultant consequences of unnecessaryscrap and repair Neither inspector isdoing a good job

Summary

As noted in this discussion, many factorsmust be considered before a program ofradiographic testing can begin at a facility

To manage a nondestructive testingprogram many options must beconsidered The final decision for a pathforward must be based on requirementdocuments (codes, standards orspecifications) and what is best for yourcompany If a person in a position ofresponsibility lacks the expertise for thiscritical decision, the industry has manytalented individuals willing to assist TheAmerican Society for NondestructiveTesting is a place to begin the decisionmaking process

Wilhelm Conrad Röntgen (Fig 10) madehis momentous discovery of X-rays onFriday, 8 November 1895, in hislaboratory at the University of Würzburg

in Germany The importance of this newkind of ray was recognized immediately

The see-through property of X-rays created

a sensation, not only in the scientificcommunity but also in the popular press

By early January 1896, newspapers aroundthe world carried news of these new raysand their ability to pass through flesh andother materials The newspaper accountscorrectly predicted the tremendous impactthat X-rays were to have on medicaldiagnosis Röntgen and other early X-ray

workers showed X-ray images of things:

Röntgen took X-ray images of hisshotgun, a compass and weights in a box

Much experimental work ensued in analmost playful atmosphere, as researchersradiographed hundreds of different kinds

of objects Industrial applications of a sortwere found almost immediately, in thesense that artillery shell casings wereamong the objects so examined It wasdecades before nonmedical uses of X-raysbecame important

Clearly, the practical uses for X-rayshave gone well beyond the early concepts

Immediate medical uses foreseen includedsetting of broken bones and location offoreign objects — bullets, pins, coins andothers Medical applications have nowexpanded to include diagnosis of diseasessuch as tuberculosis, malfunctions such asblockages of the circulatory system andthe detection of many abnormalities such

as tumors and calcium loss in bones

X-rays are now used for medical therapy,

to identify and analyze materials, toinspect industrial materials and, a use allairplane travelers recognize, to inspectbaggage and packages The methodsinclude fluoroscopy and film radiography

— the two methods Röntgen used — andmore modem techniques such as

electronic radioscopy, tomography,backscatter imaging, radiation gaging,diffraction, fluorescence and others

Preliminary Work

Röntgen was a respected scientist beforethe X-ray discovery, having publishedwork on specific heat, optical phenomena

and compressibility of liquids As adirector of the Physical Institute atWürzburg, Röntgen had freedom topursue scientific ideas that were ofinterest to him In 1895, he begancollecting the equipment needed toinvestigate luminescence effects Hestudied early work by people before him

— Faraday, Geissler, Hittorf and Crookes,for example — as well as the more currentwork of fellow German scientist PhilippLenard These scientists and others hadstudied luminescence in gases and solidsusing a partially evacuated tube, popularlyknown as a crookes tube.14This wastypically a pear shaped glass tube,containing two electrodes When a highvoltage was put between the electrodes,the positively charged ions from the gasbombarded the negative electrode,causing the release of electrons, then

called cathode rays The electrons caused

luminescence in the partial gas filling, inthe glass walls of the tube or in othermaterials placed in their path

P ART 3 History of Radiographic Testing 13

F IGURE 10 Wilhelm Conrad Röntgen.

8 November 1895 Röntgen had hiscovered tube and a darkened laboratorywhen he energized the cathode ray tubeand noticed luminescence from a bariumplatinocyanide screen on a table about

2 m (7 ft) away The luminescence wasdefinitely associated with the tube,turning on only when the tube wasenergized Röntgen knew the effect couldnot be cathode rays, because theypenetrate only a short distance in air Hewas intrigued; he investigated

He quickly learned about thepenetrating power of these new rays; theypenetrated paper, wood, metal and flesh

The rays made shadow pictures onfluorescent screens and on film

Nevertheless, he was skeptical about hisdiscovery As he became totally consumed

in a seven week intensive study hecommented to his friend, Theodor Boveri,

“I have discovered something interestingbut I do not know whether or not myobservations are correct.” At the sametime, as a scientist, he was excited Heknew he must report his findings andobtain feedback from fellow scientists

Because the new rays darkened aphotographic plate, he could take picturesand share them with others One of theseearly pictures in December 1895 was a

15 min exposure showing the bones inthe hand of his wife, Bertha Other earlypictures taken with the new rays includedweights in a box, a compass, a piece ofmetal and a shotgun He recognized that

he must publish his results so that theycould be shared with others in thescientific community His first technicalpaper on X-rays, “On a New Kind of Rays:

A Preliminary Communication,” waspublished in the annals of the WürzburgPhysical Medical Society in December

1895.15The reprints were ready by thenew year As he mailed reprints andphotographs to colleagues, Röntgen said

to Bertha, “Now the devil will be to pay,”

clearly a premonition of the comingdrastic change in his life

Fame

Röntgen was apprehensive as he sentreprints and pictures to colleagues inJanuary 1896, but he probably had noidea of what was in store for him Therewas tremendous interest in his new rays,both from the scientific community and

the general public One of his mailed set

of reprints and photographs went to hisfriend Ernst Warburg in Berlin Warburgdisplayed the material as a poster exhibit

at the 50th anniversary meeting of theBerlin Physical Society in 1896 Many sawthe exhibit in one corner of the hall.Another of his private communicationswent to a second college friend, ProfessorFranz Exner in Vienna Exner showed thepictures to several fellow scientists One ofthem, Professor Ernst Lecher visiting fromPrague, was so fascinated by the picturesthat he asked Exner if he could borrowthem overnight Lecher shared thepictures with his father, Z Lecher, editor

of the Vienna Presse newspaper Lecher’s January 1896 article in the Vienna Presse

newspaper extolled the potential of thesenew X-rays, correctly pointing out thebenefits for medical diagnosis The newsquickly spread around the world,appearing in many newspapers within thefollowing week Röntgen received morethan 1000 pieces of mail in the first weekfollowing the press announcement.Within days, scientists everywhere, usingcrookes tubes, were repeating Röntgen’sobservations and confirming his results.Once the news was out, there weremany offers of honors, lectures and visits.However, Röntgen turned down mostsuch overtures One he could not refusewas a royal invitation Röntgen gave ademonstration of X-rays before KaiserWilhelm II and his court in January 1896

As a result of this summons to the court,Röntgen was awarded the Royal Order ofMerit, an award that permits one to use

the title von, as an indication of nobility.

Röntgen never made the formalapplication for the noble rank and refused

to use the term von in his name

Another summons he could not turndown was a call from his own university

In January 1896, he lectured on hisdiscovery before the Physical MedicalSociety in Würzburg and gave the firstpublic demonstration before anoverflowing audience The image ofRöntgen’s lecture was captured in a 1961painting (Fig 11) During the lectureRöntgen radiographed the hand of hisfellow university professor and wellknown anatomist, Albert von Kolliker.Kolliker was so enthused by the discoverythat he announced that the new rays

should be called roentgen rays, as they are

still in Europe and within the medicalcommunity The lecture and

demonstration were greeted withenthusiastic applause It was to beRöntgen’s only formal public lecture onX-rays

The commercial community took note

of Röntgen’s discovery.14,16An Americanindustrial group was said to offer Röntgen

a fortune for rights to his discovery

Röntgen was similarly approached bymany industrial groups, including adocumented overture by Max Levy of aGerman company However, Röntgenremained true to his scientific calling,saying that discoveries and inventionsbelong to humanity and that they shouldnot in any way be hampered by patents,licenses or contracts, nor should they becontrolled by any one group.

Edison, the renowned Americaninventor, was quoted as saying aboutRöntgen’s attitude, “After they havediscovered something wonderful,someone else must look at it from thecommercial point of view One must seehow to use it and how to profit from itfinancially.” Edison was among the first ofmany Americans to investigate X-rays Hequickly designed and built X-ray tubesand a fluorescent screen fluoroscope,making use of the Edison discovery that acalcium tungstate phosphor screen gavevery bright X-ray images Edisonexhibited an X-ray fluoroscope at theNational Electrical Exposition at theGrand Central Palace in New York in May

1896 The Exposition gave the general

public a rare opportunity to see X-ray

pictures

Obviously, with crookes tubes in use inlaboratories around the world, it is clearthat many people before Röntgen hadproduced X-rays Once the discovery wasannounced, many scientists recognizedthat X-rays had been responsible forstrange effects they had noticed (but notfollowed up) from earlier experiments

Crookes was always rejectingphotographic plates because they werefogged, most likely from X-ray exposure

Philipp Lenard, who had helped Röntgenobtain one of his thin window tubes, hadnoticed that an electric charge somedistance away from his lenard tube wasdischarged but he did not investigatefully.17

One well documented early notice ofX-rays occurred in the physics laboratory

of Arthur W Goodspeed at the University

of Pennsylvania.18He was visited inFebruary 1890, by photographer WilliamJennings to do some photography withspark discharges After the young menfinished with the spark equipment,Goodspeed showed Jennings his crookestube equipment in operation Jenningshad several unexposed, coveredphotographic plates on the table duringthe crookes tube demonstration; he hadplaced several coins for his carfare on top

of the stack of plates On returning to hislaboratory, he processed the plates andfound a curious image of several roundobjects He dated and filed the plate, only

to bring it back at Goodspeed’s requestafter the news of the X-ray discovery

They could document that they had made

an X-radiograph five years beforeRöntgen’s discovery Goodspeed andJennings merely brought the radiograph

to public attention, never claiming anycredit for discovering X-rays

Röntgen himself published twoadditional scientific papers about X-rays

“On a New Kind of Rays, Continued,”15was published by the same Würzburgpublication in March 1896 and wasfollowed by “Further Observations on theProperties of X-Rays,”19published inMarch 1897 by the Prussian Academy ofSciences His three scientific paperspresented thorough results about X-rays

His investigations showed thepenetrating power of the new rays asrelated to the density of the absorber andthe effect on fluorescent materials andphotographic film Röntgen took pinholepictures to confirm that the source of theX-ray emission was the point where thecathode rays struck the glass wall or ametal target He recognized thenonuniform distribution of the X-rayemission from the target and found thefundamentals of the inverse square lawfor decreasing X-ray intensity withincreasing distance from the target Hetried without success to deflect the X-raybeam with a magnet or an electric field

His attempts to demonstrate reflectionand diffraction were likewise withoutsuccess His experiments did produceevidence that the new rays causedelectrical conductivity in air and thatheavy metal targets such as platinumproduced more intense X-ray beams than

F IGURE 11 Röntgen demonstrates X-rays in 1896.

glass or aluminum targets His threepapers on X-rays gave the basicinformation about X-rays to the world.20

Early Medical Applications

The medical use of X-rays beganimmediately It was straightforward torecognize the usefulness of X-rays to findforeign objects in the body and to helpset broken bones There are manydocumented instances of suchapplications as early as January andFebruary 1896 The first recorded X-raypicture in the Americas was taken byArthur W Wright of Yale University, inJanuary 1896 This was quickly followed

by X-ray work at other universities

Men recognized for early work in whathas become medical radiology includeFrancis H Williams, a doctor at theBoston City Hospital, and William J

Morton, a New York City physician.21Williams used X-rays to study anatomy,both diseased and normal He usedfluoroscopy and film radiography to studythe thorax, for determining the outline ofthe heart, for diagnosis of tuberculosisand other medical studies Williams hadthe advantage of working with twoMassachusetts Institute of Technologyscientists, Charles Norton and RalphLawrence, whose work advanced earlyX-ray technology Morton’s wide rangingpioneering X-ray work included the

recognition that gas in the body can helpoutline organs, an early concept of acontrast medium

Introduction of Additional Radiation Sources

In 1898 Marie Sklodowska Curie (Fig 12)and Pierre Curie published researchshowing the discovery of two newradioactive elements, polonium andradium, laying the foundation for gammaradiography

The early X-ray tubes were partiallyevacuated glass bulbs Metal targets andcurved cathodes were quickly added toincrease X-ray output Nevertheless, it was

a challenge to operate these early gastubes consistently The gas pressurechanged because of outgassing of thewalls and other heating effects One ofthe first X-ray related patents was for atechnique of controlling the tube gaspressure (issued March 1896 to Siemens)

Among the early uses of radioscopy,fluoroscopes similar to those at today’sairports were used during World War I toinspect packages for contraband

(Fig 13).22

It was in this background that William

D Coolidge (Fig 14) of General Electricintroduced the hard vacuum, hot cathodeX-ray tube, truly a significant advance inX-ray technology.23This new X-ray tubeconcept brought much improvedreproducibility and ease of operation toX-ray technology and prepared the wayfor high energy X-ray use The patent forthis landmark X-ray development wasissued in 1916.24

F IGURE 12 Marie Sklodowska Curie (1928).

F IGURE 13 Radioscopic system for detection of contraband

(circa 1910)