Page 23 - Quick Guide to Welding and Weld Inspection by S.E. Hughes, Clifford Matthews

A Quick Guide to Welding and Weld Inspection

. Convex fillet welds have sharp toes, which give very poor
fatigue resistance but the excess weld metal they have on
the throat gives maximum design strength (although it will
increase the weight of the weld). The excess weld metal will
also increase cost due to the extra consumables required
and increased welding time. These welds are only used
where strength is paramount and fatigue loading is not an
issue.
Drawing rules and weld symbols
Weld symbols on drawings are a very efficient way to transfer
fabrication information from the designer to the fabricator
by showing the joint and welding information as a symbolic
representation. This reduces the amount of information that
would have to be put on the drawing in written form or as
sketches. An inspector must have a good working knowledge
of weld symbols as a large proportion of inspection time is
spent verifying that the welder is complying with the
approved fabrication drawing. Weld symbols themselves
are similar between the major standards but there are some
differences in how they are presented. It is important to
understand the basic differences between the major standards
and to be able to recognise any drawing standard being used.
Reference should always be made to the applicable standard
for specific symbolic information.
Common standards in use today are BS EN 22553 (which
replaced BS 499) and AWS A2.4. Reference is still made to
BS 499 because many old fabrication drawings will have been
done to this standard. Most drawing standards follow a basic
set of rules or conventions when formulating welding
symbols. A weld symbol is composed of five main
components common to most standards, consisting of an
arrow line, a reference line, the welded joint symbol,
dimensional information and finally any supplementary
information.

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Woodhead Publishing Ltd – A Quick Guide to Welding and Weld Inspection
Data Standards Ltd, Frome, Somerset – 17/9/200901QG Welding chap1.3d Page 8 of 16