Table Of ContentN o n - D e s t r u c t i ve T e s t i ng 92
V o l u me I
Proceedings of the 13th World Conference on
Non-Destructive Testing
Sao Paulo, Brazil, 18-23 October 1992
edited by
C. Hallai and P. Kulcsar
Elsevier
Amsterdam - London - New York - Tokyo 1992
Trade edition (ISBN: 0 444 89791 7) will be published by
ELSEVIER SCIENCE PUBLISHERS B.V.
Sara Burgerhartstraat 25
P.O. Box 211,1000 AE Amsterdam, The Netherlands
© 1992 Elsevier Science Publishers B.V. All rights reserved.
No part of this publication 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, Elsevier Science Publishers B.V., Copyright & Permissions Department,
P.O. Box 1991,1000 AM Amsterdam, The Netherlands.
Special regulations for readers in the U.S.A. - This publication has been registered with the Copyright
Clearance Center Inc. (CCC), Salem, Massachusetts. Information can be obtained from the CCC about
conditions under which photocopies of parts of this publication may be made in the U.S.A. All other
copyright questions, including photocopying outside of the U.S.A., should be referred to the copyright
owner, Elsevier Science Publishers B.V., unless otherwise specified.
No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a
matter of products liability, negligence or otherwise, or from any use or operation of any methods, products,
instructions or ideas contained in the material herein.
This book is printed on acid-free paper.
Printed in Brazil
ν
PREFACE
With great pleasure and satisfaction we are presenting these two volumes of
the 13th World Conference on Non-Destructive Testing (WCNDT) Proceedings.
These proceedings are the result of long and hard work by all the organization
staff of this important and historic event in our country.
Technical papers treating the most diverse NDT techniques and correlated
fields are being presented here, providing an up-to-date overview of the main
applications and trends in these important Quality Control techniques. Besides
showing the improvement and development of new techniques and the fast
automatization of Non-Destructive Testing, many papers are pointing out the
recent preoccupation of humanity with the environment, and also the
valorization of professionals involved with inspection jobs is treated.
Non-Destructive Testing (NDT), once again, is confirming its vital role, not
only in the Quality Assurance and Control of the manufactured products, but
also as an instrument of public, environment and industrial safety.
The preparation of these proceedings was only possible because of the
contributions received from all over the world, and also because of the strong
participation of the whole technological Brazilian community, represented by
the authors of the papers here released, as well as by the experts that have
integrated the Conference Commitees and that have brought their valuable
collaboration.
This opportunity is also taken to extend our gratitude to the members of the
Committee in charge of the organization of the event, to the sponsors (AGFA,
SGS and PETROBRAS), to the members of the Brazilian Association of Non-
Destructive Testing (ABENDE), and the whole national and international
technical community.
Promoted by the International Committee on Non-Destructive Testing (ICNDT),
and organized by the Brazilian Association of Non-Destructive Testing
(ABENDE), this event has the following main objectives: to increase the number
of NDT professionals and to promote the technical interchange of their
experiences.
Carlos Hallai Jr.,
President ICDNT/13th WCNDT
vi
FOREWORD
After many years being expected, and after great effort being employed for its
accomplishment, it has been achieved to organise the 13th World Conference on
Non-Destructive Testing (13th WCNDT) in Latin America, and specifically in
Brazil, thus representing a special opportunity to the people of this region
to participate in such an important event.
The total assets of the technical papers that arrived from all over the world
for this very important Conference is being considered of an unestimated
value, not only because of their technical contents but also because of the
efforts of each author contributing to this opportunity to improve the
knowledge in this area of technology.
A fast reading of the papers' contents presented in these Proceedings
demonstrate the remarkable involvement and participation of Non-Destructive
Testing in the industrial development of.the countries.
At this moment when world efforts are being concentrated on improving and
increasing quality and the related productivity, the new information contained
in the papers presented in the 13th WCNDT Proceedings demonstrates the
contribution this Conference is bringing to the development of ideas and
knowledge.
Oswaldo Rossi Jr.,
Vice-Chairman Scientific Committee 13th WCNDT
vii
13th World Conference on Non-Destructive Testing
13th WCNDT
BOARD
Carlos Hallai Jr. G.M. van Dijk
President Past President
Paulo Kulcsar Oswalso Rossi
Vice President Vice President
Joao Antonio Conte
ICNDT Secretary
Officials of the 13th WCNDT
Carlos Hallai Jr. Alejandro Spoerer
WCNDT President Finances
Oswaldo Rossi Jr. Wilson do Amaral Zaitune
Scientific Committee Scientific Committee
Ami 1 ton Carvalhal Marta S. Loewenstein
Exhibition WCNDT General Secretary
Marcia Tellini
WCNDT Assistant Secretary
Sponsors
Hugo Deschaumes Nelson Moczydlower
AGFA PETROBRAS
Hilton Sergio B. Milani
SGS
Consulting Committee
- Aldo Narcisi
Brazilian Association for the Development of Industries
- Carlos Buck Pastorisa
Brazilian Association of the Machine and Equip. Industry
National Sindicate of the Machine Industry
- CI audio L. Froes Raeder
National Institut of Metrology, Standardization and Quality Control
- David Fischel
Brazilian Association of Industrial Engineering
- Jerzy Lepecki
National Power Co. - ELETROBRAS
- Jose L. de Santana Carvalho
Nuclear Energy National Comission
- Jose Paulo Silveira
Ferderal Secretary of Science and Technology
- Antonio Maciel Neto
Federal Ministry of Economy, Treasury and Planning
- Mario Gilberto Cortopassi
Federation of Industries of the State Sao Paulo
- Nelson Moczydlower
National Oil Co. - PETROBRAS
- Mrs. Luiza Erundina
Mayor of the City of Sao Paulo
- Nelson Peixoto Freire
Brazilian Assoc. of the Electric and Electronic Industries
viii
- Plinio Marcel ο Fernandes
Viacao Aerea Riograndense - VARIG S.A.
- Renate Radicella
International Atomic Energy Agency - IAEA
- Roberto Bastos
Brazilian Association of NDT Inspection Companies
- Silvia Mangabeira
Sao Paulo Convention and Visitors Bureau
- Zuhair Warwar
Brazilian Cooperation Agency - Foreign Affairs Ministry
Executive Committee
Alejandro Spoerer Ami 11 ton Carvalhal
Bernardo V. Camilo Oliveira Carlos Hallai Jr.
Denise Fernandes Fernando A.P. de S. Leon
Joao Antonio Conte Jose Efromovich
Jose Florentino Vieira Leal Leo Marcelino
Marta Loewenstein Oswaldo Rossi Jr.
Paulo Kulcsar Wilson do Amaral Zaitune
Scientific Committee
Akira Sakamoto Alan Roberto Chambon
Alexandra Saraiva de Mello Antonio Guilherme Mury
Atilio Bruno Veratti Carlos Gonzalo R. de Cellis
Carlos Soligo Camerini Claudio Soligo Camerini
Cyro Costa Junior Jorge Alberto Vianna
Jose Carlos Paioli Jose Santaella Redorat Jr.
Luiz Batista Muller Luis Marcelo Piotto
Marco Antonio Marchi de Guido Milton Mentz
Mohamed Fawzi M. ALi Mogawer Nazem Nascimento
Nelson Jose de Oliveira Paulo P. de Castelo Branco
Pedro Feres Filho Raimar Eckard Schmidt
Renato dos Santos Pereira Ricardo de 0. Carneval
Ricardo Tadeu Lopes Wilson do Amaral Zaitune
Non-Destructive Testing 92
C. Hallai and P. Kulcsar (Editors)
1992 Elsevier Science Publishers B.V. xxxi
NDT RELIABILITY - A WAY TO GO.
a
G.M. van Dijk and J.Boogaard ^
a
KEMA N.V., P.O.Box 9035, 6800 ET ARNHEM (NL)
b
DSM Research b.v., P.O.Box 18, 6160 MD GELEEN (NL)
SUMMARY.
Proper consideration of NDT reliability can only be achieved if
reliability targets are specified in a relevant and achievable manner. A
general approach in this respect is being presented taking into account
reliability characteristics of NDT inspection systems and different
inspection regimes. Limiting values for the applicable reliability
characteristics are suggested considering a two class system.
1. INTRODUCTION.
Reliability of products determines to a large extent their fitness for
use. Inspection as well during manufacture as in service is an important
tool to ensure this reliability. Proper inspection calls for a
well-balanced inspection programme, i.e. choice of the inspection methods
and the scope of inspection, with due attention to the cost factor. There
is a growing need to assess these choices quantitativily. This is brought
about on the one hand by general quality assurance principles requiring all
relevant matters to be documented and traceable. On the other hand, this
need is a natural consequence of the growing trend towards product
certification, which provides easy-to-use benchmarks for technical product
quality and reliability.
Up until now, the selection criteria for inspection methods have been
limited to the aspects of sensitivity, procedure and qualification. The
aspect of reliability of an inspection method has never been a criterion.
In selecting an inspection system, it is well to aim at, and to quantify,
the eventual overall effectiveness of the individual inspections. This
requires quantification of the inspection reliability also. Although this
may complicate the selection process, it offers important advantages to
manufacturers, users, licensing authorities and inspection organisations.
For licensing authorities, for instance, it provides a better means of
appraisal. To manufacturers and users it provides the possibility of choice
and optimisation, economic or otherwise. Furthermore, it enables inspection
organisations to find economical alternatives by quantifying the value of
the individual inspection procedures. An approach based on inspection
xxxii
effectiveness reveals what technical developments are most worthwile.
This presentation aims to illustrate in which way the aspect of reliability
can be included in the selection of inspection programmes.
2. INSPECTION.
2.1 Objective.
Most usually, product properties show significant variations as a result
of variations in the material properties, manufacturing process and
in-service effects. Inspection aims to minimise the chances of negative
excursions in the quality of a finished product through early detection of
defects. A general distribution curve for the product quality is shown in
Figure 1 (supposing that product quality is inversely proportional to the
size of defects).
Figure 1. Probability of product quality value distribution and
characteristic values.
In this figure the following characteristic values and their
interdependences are important:
R Rationally required quality, that is, the quality that would be just
sufficient if it could be fully assured that the design and usage
conditions are not subject to unknown influences (margins).
S The quality value as set out in the design or specifications. It is more
stringent than R to compensate for uncertainty margins. Thus, there
should be a high probability of the actual product quality being better
than the specified value of S.
D The quality value as set out in the inspection programme. This value
should be somewhat more stringent than the specified value S to
compensate for the uncertainty margins in the inspection results.
F The quality value of finished product. This value, too, should be more
stringent than the specified quality value S and the detection quality
value D because of the spread in the actual product quality as
influenced by material properties and manufacturing process. The
required difference between F and D or S is largely dictated by this
spread in product quality.
Figure 1 shows also the effect of inspection on the eventual product
quality distribution. Apparently, in the example depicted here, it is only
marginal. The quality is largely determined by the materials and the
manufacturing processes employed. Accordingly, inspection will yield only a
limited rejection rate. Inspection will gain importance when the product
quality distribution changes. This may involve a shift in the average
product quality, as shown in Figure 2, because of changes in the
manufacturing parameters or deterioration of bare material properties.
Effect of inspection
Figure 2. Effect on
probability
distribution curve,
due to a decrease in
finished product
quality.
Product quality value
( ^ Defect size)
Inspection will also gain importance with wider spreads in product quality
(Figure 3) as may result from, for instance, wider manufacturing
tolerances.
Effect of inspection Figure 3. Effect on
probability
distribution curve due
to an increase in
manuf ac tur ing
tolerances·
Product quality value
( ^ Defect size)
xxxiv
Inspection should be aimed at maintaining and assuring the quality of the
product as delivered or retested during service. In actual practice, the
defect detection score at the target quality value D often is less than
100% so that the inspection would seem to be inadequate and to fail to meet
its objective.
We shall now discuss whether this conclusion is correct and whether it has
any fuurther implications.
2.2. Inspection regimes.
With inspections for assuring a given specified quality value S broadly
two extreme scopes may be distinguished:
A those which are symptom-oriented, and
Β those which are aimed to satisfy a product specific interest.
Symptom-oriented inspections.
Here, inspection is mainly aimed at consistent detection of relevant
defects to enable initiation of corrective action. A 100% defect detection
score is not necessary. Examples are weld inspections of items that need
not meet any specified rational quality values but where, rather, the
quality is assessed for good workmanship. Inspections in mass production,
usually focussing on process monitoring, fall into this category also.
Another example are in-service inspections aimed at detecting not
immediately critical degradation phenomena such as corrosion.
Characteristics of the inspections within this scope involve the following
aspects:
A constant detection characteristic. The detection score need not
necessarily be 100%. It is essential, however, that the number of
nonconformances observed in consecutive inspections truly reflect the
actual number of nonconformances to enable appropriate corrective
action.
A low false rejection rate. Many inspection methods involve observation
of what are believed to be nonconformances and of nonconformances that
are immaterial to the product quality. A high proportion of good
products being rejected can be costly and may lead to inappropriate
corrective action being taken on false grounds.
Coverage. The inspection must be well able to detect relevant
nonconformances; in other words, specific nonconformances of any
significance must not consistently be overlooked.
Product-oriented inspection.
Here, the primary objective of inspection is to assure a defined minimum
quality level, usually of single products. Examples are in-service
inspections of loaded structures for fatigue cracks and inspections during
manufacture of the wall thickness of parts impairing strength.
