Exploiting Advances in Arc Welding Technology

301 Pages·1999·42.22 MB·English

by  TWI Ltd

International Conference
EXPLOITING
ADVANCES IN
ARC WELDING TECHNOLOGY
Cambridge, UK, 30-31 March 1998
TWI
V!llll
ABINGTON PUBLISHING
Woodhead Publishing Ltd in association with The Welding Institute
Cambridge England
Published by Abington Publishing
Woodhead Publishing Limited, Abington Hall, Granta Park
Great Abington, Cambridge CB21 6AH, UK
www.woodheadpublishing.com
First published 1999
© 1999, Woodhead Publishing Limited
Conditions of sale
All rights reserved. No part of this publication may be reproduced or transmitted in any
form or by any means, electronic or mechanical, including photocopying, recording or
any information storage and retrieval system without permission in writing from the
publisher.
The contributions which appear in this volume have been printed from original copy
submitted to the publisher, and have been reproduced verbatim. Neither the authors, nor
the publisher, nor anyone else associated with this publication, shall be liable for any
loss, damage or liability directly or indirectly caused, or alleged to be caused, by this
book.
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library.
ISBN-13: 978-1-85573-416-6
ISBN-10: 1-85573-416-8
Printed by Victoire Press, Cambridge, UK
Exploiting Advances in Arc Welding Technology
CONTENTS
SESSION 1: Process developments - TIG welding 1
Developments in A-TIG welding
DHOWSE 3
TIG welding with an asymmetric AC power source
A FOSTER 10
Increasing the penetration capability of arc and control of parameters
in TIG welding
C KDATTA 19
The feasibility of generating a microwave powered plasma
G VERHAEGHE, W LUCAS and S WYLIE 29
Weld inspection using laser vision
C REICHERT and T-C HUANG 38
SESSION 2: Process developments - MIG welding 49
Faster with two wire electrodes - Metal Inert-Gas welding of aluminium materials
H HACKL 51
The influence of power source type on welding performance and weld quality
J NIXON, B OGUNBIYI and P CASTLE-SMITH 55
Effect of surface active element on porosity formation by GMA welding
of Zn plated steel for automobile industry
T SHINODA, Y TAKEUCHI and T SHIMIZU 63
Underwater wet welding and cutting using the FCA process
M COOPER and W LUCAS 75
SESSION 3: Consumable developments 87
Consumables for welding of high strength steels
C HIDESJO and L-E SVENSSON 89
Moving contact arc welding
G VERHAEGHE, S FISHER, W M THOMAS, R L JONES and P WOOLlIN 98
Spattering characteristics of low spatter wire in MAG welding
Y HAN, J B LEE and D S UM 105
SESSION 4: Developments in process automation 115
Developments in vision seam tracking for welding
MWILSON 117
Development of a top face penetration controller based on an infrared camera
RJONES 124
Vision systems for automated fusion welding
J S SMITH and J LUCAS 137
Exploiting advances in sensing and control for mechanised welding
RJ BEATTIE 148
SESSION 5: Process application 159
Robust weld quality
J G RAFFERTY 161
Recent developments in the welding of titanium alloy pipe for offshore riser
applications
G HUTT and J SCHLEY 173
The use of mechanisation and the latest cored wire technology in the
construction of a 32 000 tonne production jack-up
C LOCHHEAD and R 0 BEWS 190
The GMAW-STT, an advanced welding process for root pipe and sheet welding
L van NASSAU 209
Pipeshop 2000 - a shopfloor report on exploiting automated gas metal arc
roll welding technology in pipe spool prefabrication
G J TAHASH 221
1 INTRODUCTION AND SCOPE
This following document has been produced by Working Group 2 of
Commission V of the International Institute of Welding and supersedes
previous versions.
1.1 Objectives
The objectives of this document are to give technical guidance and
information on non-destructive testing (NOT) techniques suitable for
use underwater on welded steel constructions.
When properly used, modern underwater NOT techniques are
capable of similar performance to comparable onshore NOT
equipment. However, as with all technologies, the quality of the results
depends on appropriate selection and operation of the equipment. It
is accordingly the primary purpose of this document to assist in the
production of high-quality reliable results from underwater inspection
by promoting what might reasonably be considered good practice
at the time of writing (1997).
This document is not a code and neither is it a statutory instrument
with legal power, nor does it seek to lay down minimum standards.
Nonetheless, a vital constituent of any inspection practice is to
accomplish the work with minimal risk to personnel, and it is expected
that organisational schedules and procedures will consider this aspect
in adequate detail. Notwithstanding the various notes in this
document concerned with safety, nothing in this text should be taken
(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0) as diminishing or removing the onus placed on the individual to adopt
safe working practices and to take the final responsibility for the
consequences of his own actions.
Furthermore, it is not the intention to produce prescriptive
requirements or in any way to restrict underwater inspection by
prohibiting certain practices or by inhibiting the introduction of new
equipment or techniques. However, where in the opinion of the
Working Group, the use of items of equipment in some configurations
may give rise to undesirable consequences, this will be pointed out.
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1.2 Scope
The document is intended for the external inspection of welded steel
constructions used offshore such as oil and gas platforms, pipelines
and risers, harbour installations, ships' hulls, etc, though the practices
discussed should also be suitable for inspection of cast components
with appropriate modifications to reflect the different metallurgical
properties. Testing of parent material as well as welds is covered.
The document applies not only to methods used manually by divers in
water or in a habitat, but also to remotely-controlled or automated
methods used from submersibles, atmospheric chambers, or
remotely-operated vehicles (ROVs) with inspectors remote from the
work site. Only the commonly used NDT methods are described in
detail, with less-commonly used methods being given more superficial
description.
Since this document is concerned with the external inspection of
welded structures underwater, it will not consider inspection in the
splash zone or above water, and it does not cover inspection inside
pipelines by inspection pigs and suchlike. Similarly, information is not
given on diving or operational aspects of underwater inspection
activities. It must, however, be reiterated that, as a minimum, proper
precautions need to be taken with respect to diver safety and
operation, particularly in relation to electrical hazards, implosion of
equipment, and the risk of water penetration into equipment. In
saturation habitats, attention should also be given to helium
penetration into equipment under high external pressure.
The document does not address pre-inspection planning and
(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)
scheduling, or the selection of areas for inspection. Reference should
be made to the appropriate company documentation on these
subjects. In addition, the use of inspection results is not covered. Both
these activities are strongly dependent on a host of factors such as:
construction type and environment, consequences of failure, national
regUlations, agreement between vendor and purchaser, etc. The
choice of the most suitable NDT methods for an application is also
dependent on similar factors and only broad guidelines will be given.
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1.3 Further information
Information in the main part of this document may be expanded
upon in the background text given in Appendix A. Reference should
also be made to other IIW documents and to reports such as those
listed in the Bibliography. Particularly recommended are reports
published by the United Kingdom's Marine Technology Directorate
Ltd: 'Underwater inspection of steel offshore installations:
implementation of a new approach; MTD Ltd Publication 89/104'.
Publications by the UK Health & Safety Executive (HSE) are also a
good source of information for offshore NDT.
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3 COMPONENTS OF NON-DESTRUCTIVE
EXAMINATION
In genera\, in order to perform a non-destructive evaluation the
following elements are necessary:
• Personnel
• Equipment
• Procedures
• Acceptance criteria.
Each of these elements must be adequately taken care of in order to
perform an examination to proper quality standards for the task in
question. The personnel must be sufficiently trained and qualified, the
equipment must meet certain requirements on sensitivity, operability,
etc, and procedures must be clearly recorded and understood to
ensure that the necessary steps are followed.
An essential part of the procedures is to specify clear criteria for the
reporting of findings, to ensure that the utmost benefit is derived from
the inspection. Inspection is not a clear-cut matter and the act of
inspection constantly relies on human judgement and discrimination,
and hence is usually highly affected by the ability and experience of
the inspection team. Thus, in order to ensure consistency, it is
necessary that the procedures address this issue and, in particular,
find the correct balance between excessive reporting of
inconsequential trivia, which results in slow and ineffective inspection,
and the alternative risk of ignoring significant indications. The
specification of what constitutes a reportable indication and
(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0) appropriate follow-up procedures will depend on the policy of the
owners of the installation.
In other words, the actual practice of inspection must take place
against the background of the Operator's IMR (inspection,
maintenance, and repair) philosophy in addition to complying with
any local statutory requirements and regulations.
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2 DEFINITIONS AND GLOSSARY
The following terms are defined for use in this document.
2.1 Definitions
Non-destructive testing (NDT), non-destructive examination (NDE) or
non-destructive inspection - the carrying out of inspection causing
little, if any, damage to the test item, usually by physical test methods
in conjunction with visual assessment, either at the worksite by the
inspector or via a remote telecommunications link. The words testing,
examination and inspection are thoughout this document regarded
synonymous, reflecting the common, and somewhat arbitrary
terminology used in the offshore inspection industry.
Non-destructive evaluation (NDE) - the comprehensive assessment of
the results of NDT, including the assessment of any inspection
indications, which may comprise formal fracture mechanics analysis
and other engineering reliability studies. The overall results and
assessment will normally be drawn together in a formal report.
Indication - a response from the inspection system suggesting the
existence of a flaw.
Flaw - an indication confirmed by use of two or more different
inspection techniques, including close visual inspection. A flaw is
usually, but not always, a crack. The term is used in preference to
'defect' in accordance with European Standards, the designation
(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0) 'defect' being considered as con notating 'defective' or 'unfit for
purpose'. A flaw is a departure from perfection that does not
immediately condemn the article as unacceptable but that
nevertheless should be considered in an assessment of reliability.
Further information may be found in IIW documents.
Spurious indication or false call - a plausible, but discounted,
indication that has, on further investigation, been assessed as not
being a flaw. It would normally still be noted in the records of the
inspection.
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Probability of detection (POD) - a measure of the performance of an
non-destructive testing (NOT) system intended to detect flaws, in terms
of the chance of finding a flaw. It is a complicated variable,
depending on: NOE technique and equipment; skill of the operator;
the inspection conditions; the definition, nature, location, and size of
flaw and other factors. It is often presented in the form of a curve as a
function of flaw size (usually length). Considerable care should be
taken not to mis-apply such curves as their interpretation is far from
clear-cut and demands some knowledge of statistical methods.
Accuracy of sizing (AOS) - a measure of the performance of NOE
equipment in giving an estimate of the size of a flaw. In the important
case of surface-breaking flaws, the depth is quoted as being the
significant variable for causing brittle fracture. Accuracy of sizing is a
complicated concept, being heavily dependent on a number of
factors, some ill-defined. The concept of accuracy of sizing is less well
established than POO but includes systematic and random errors of
size estimates.
2.2 Glossary
Magnetic particle inspection (MPI) or magnetic particle testing (MPT)
- a combined visual and electromagnetic technique relying on the
attraction of minute ferromagnetic particles to magnetic flux diverted
from an applied field by a flaw. The particles emphasise the length of
the defect rendering it more visible to the inspector. The method is
suitable for detecting surface-breaking flaws, but may also have a
limited capability for anomalies very near to the surface. The
magnetic field may be applied by permanent magnets or by
(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0)
electromagnetic induction using coils, a yoke, or prods. In many
ways, MPI can be regarded as a quasi-standard method against
which other NOT methods are often compared, though it is known to
be very sensitive to the skill of the inspector.
Alternating current potential drop (Acpd) - a contacting
electromagnetic technique using the skin effect of the alternating
current from which an assessment of crack depth can be made on
surface breaking defects. ACPO is a sizing technique rather than a
detection method.
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