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8.0 WELDING SYMBOLS
A weld joint can be represented on an engineering drawing by means of a detailed sketch showing every detail and dimension of the joint preparation - as shown below.
While this method of representation gives comprehensive information, it can be time consuming and can also ‘overburden’ the drawing.
An alternative method is to use a symbolic representation to specify the required information - as shown below for the same joint detail.
Symbolic representation has following advantages:
• simple and quick to put on the drawing
• does not over-burden the drawing
• no need for an additional view - all welding symbols can be put on the main
assembly drawing
Symbolic representation has following disadvantages:
• it can only be used for standard joints (e.g., BS EN ISO 9692)
• there is not a way of giving precise dimensions for joint details
• some training is necessary in order to interpret the symbols correctly
R
1-4mm
1-3mm
Single-U preparation
8.1 STANDARDS FOR SYMBOLIC REPRESENTATION OF WELDED
JOINTS ON DRAWINGS
There are two principal standards that are used for welding symbols, namely:
European Standard EN22553 – Welded, brazed & soldered joints – Symbolic representation on drawings
American Standard AWS A2.4 – Standard Symbols for Welding, Brazing, & Non-destructive Examination
These standards are very similar in many respects, but there are also some major differences that need to be understood to avoid misinterpretation.
Details of the European Standard are given in the following sub-sections with only brief information about how the American Standard differs from the European Standard.
Elementary Welding Symbols
Various types of weld joint are represented by a symbol that is intended to help interpretation by being similar to the shape of the weld to be made.
Examples of symbols used by EN 22553 are shown on following pages.
8.2 ELEMENTARY WELDING SYMBOLS
8.3 COMBINATION OF ELEMENTARY SYMBOLS
For symmetrical welds made from both sides, the applicable elementary symbols are combined – as shown below.
Designation Illustration of joint preparation Symbol
Double-V butt weld (X weld)
Double-bevel butt weld (K weld)
Double-U butt weld
Double-J butt weld
8.4 SUPPLEMENTARY SYMBOLS
Weld symbols may be complemented by a symbol to indicate the required shape of the weld.
Examples of supplementary symbols and how they are applied are given below. Designation Illustration of joint preparation Symbol
Flat (flush) single- V butt weld
Convex double-V butt weld
Concave fillet weld
Flat (flush) single- V butt weld with flat (flush) backing run
Single-V butt weld with broad root face and backing run
Fillet weld with both toes blended smoothly
Note: If the weld symbol does not have a supplementary symbol then the shape of the weld surface does not need to be indicated precisely.
The schematic below illustrates these principles.
There are some conventions about the arrow line, namely:
it must touch one end of the joint line it joins one end of the continuous reference line such that it forms an angle with it
In case of a non-symmetrical joint , such as a single bevel joint, the arrow line must point towards the joint member that will have the weld preparation put on to it (as shown below)
An example of how a single-bevel butt joint should be represented is shown below.
8.7 POSITION OF THE REFERENCE LINE AND POSITION OF THE
WELD SYMBOL
The reference line should, wherever possible, be drawn parallel to the bottom edge of the drawing (or perpendicular to it).
For a non-symmetrical weld it is essential that the arrow side and other side of the weld be distinguished. The convention for doing this is as follows:
symbols for the weld details required on the arrow side must be placed on the continuous line
‘arrow side’
‘arrow side’
arrow line
‘other side’ arrow line
‘other side’
arrow line
‘other side’ ‘arrow side’
arrow line
‘arrow side’ ‘other side’
symbols for the weld details on other side must be placed on the dashed line
This convention is illustrated below for a single-V joint with a backing run.
arrow side
arrow side
other side
other side
or
8.9 DIMENSIONING OF WELDS
General rules Dimensions may need to be specified for some types of weld and EN 22553 specifies a convention for this.
dimensions for the cross-section of the weld are written on the left-hand side of the symbol
length dimensions for the weld are written on the right-hand side of the symbol
the absence of any indication to the contrary, all butt welds are full penetration welds
8.9.1 SYMBOLS FOR CROSS-SECTION DIMENSIONS
The following letters are used to indicate dimensions:
a fillet weld throat thickness Z fillet weld leg length s penetration depth (applicable to partial penetration butt welds & deep penetration fillets)
Some examples of how these symbols are used are shown below.
10mm
Partial penetration single-V butt weld
s
8mm
Z Fillet weld with 8mm leg
8.9.2 SYMBOLS FOR LENGTH DIMENSIONS
To specify weld length dimensions and, for intermittent welds the number of individual weld lengths (weld elements), the following letters are used: -
l length of weld
(e) distance between adjacent weld elements
n number of weld elements
The use of these letters is illustrated for the intermittent double-sided fillet weld shown below.
a Fillet weld with 6mm throat
6mm
8
150mm
100mm
PLAN VIEW END VIEW
Note: dashed line not required because it is a symmetrical weld
Z8 (^3) 150 (100) Z z (^) z nn (^) l (e)l (e)
(^3) 150 (100) z z z n n l (e) l (e)
(^) n l (e)
z n l (e)
8.10 INDICATION OF THE WELDING PROCESS
If required, the welding process is to be symbolised by a number written between the two branches of a fork at the end of the reference line – as shown below.
8.11 OTHER INFORMATION IN THE TAIL OF THE REFERENCE LINE
In addition to specifying the welding process, other information can be added to an open tail (shown above) such as the NDT acceptance level the working position and the filler metal type and EN 22553 defines the sequence that must be used for this information.
A closed tail can also be used into which reference to a specific instruction can be added – as shown below.
8.12 WELD SYMBOLS IN ACCORDANCE WITH AWS 2.
Many of the symbols and conventions that are specified by EN 22553 are the same as those used by AWS.
The major differences are:
only one reference line is used (a continuous line)
symbols for weld details on the arrow side go underneath the reference line
symbols for weld details on the other side go on top of the reference line
Some Welding Process Designations
111 = MMA 121 = SAW 131 = MIG 135 = MAG 141 = TIG
WPS 014
These differences are illustrated by the following example.
arrow side
other side
