Weld Symbols on Drawings

Engineering drawings are descriptions of manufactured objects in terms of shape, surface, finish and material. In many industries it is customary to draw the shape of the component without indicating how that shape is achieved. The drawing is a description of a requirement produced by the designer for the instruction of the manufacturer. In theory, the manufacturer knows best how to produce an object with the resources he has. In practice, of course, the designer compromises and produces designs which are capable of production by the techniques of which he is aware. For example, a round hole can be drilled, bored or punched and can be finished by reaming, but whichever method is used, the lines on the drawing are the same and whichever method is used, the material is not changed in its characteristics.
A welded joint offers a range of considerations which do not arise in other forms of manufacture. Firstly, there are far more techniques for making a welded joint than in many other manufacturing operations. This means that the designer has far less chance of foreseeing the manufacturer's methods. Secondly, the properties and integrity of the joint will depend on the manner in which the weld is made. Despite this, the designer can still indicate the type of joint he requires, provided that he is prepared to accept that he may not be able to completely define the joint in the earlier stages of a design.
In some industries it is customary for the manufacturer to produce shop drawings which contain details of weld preparations and reference to established welding procedures not shown in detail on the designer's drawings. The range of British Standard symbols which can be used on a drawing to indicate a weld detail are described here.

 

Figure 59:  Weld Symbols

 

 

 

 

 

 

 

In practice, the two symbols shown in figure 59 would be used as follows:
Figure 60: Use of Weld Symbols

Note: The arrow points towards the prepared edge.

 

 

 

 

 

 

 

 

 

Fillet
Square butt
Single-V butt
Double-V butt
Single-bevel butt
Double-bevel butt
Single-J butt
Double-J butt
Sealing run
Backing strip
Dressed flush
And a very useful symbol. Full penetration butt weld by a welding procedure to be agreed.

                    
The weld symbol is always drawn the same way round regardless of the layout of the arrow and the reference line. The position of the symbol on the reference line has significance. A symbol below the reference lien means that the weld is made from that side of the joint indicated by the arrow. A symbol above the reference line means that the weld is made from the opposite side of the joint to the arrow.

 

Figure 61: Weld Symbol Positions

 

 

 

 

 

 

 

Figure 62:  Position of the Arrow

 

 

 

 

 

 

 

 

 

 

 

Note: The arrow points towards the prepared edge.
Figure 63:  Weld All Round

 

 

 

 

 

A joint made from both sides has a symbol on each side of the reference line.
Figure 64: Joint made from Both Sides

Weld size can be indicated on the symbol, 6mm fillet weld. The drawing must state whether a throat or leg dimension is quoted.

Unequal leg fillet weld. This must be defined by leg length. A diagram of weld shape is required here.

 

A diagram is not required here because the size of the member indicates the weld orientation.

 

Information other than weld size may be written to the right of the symbol.

Figure 65
17.1 Intermittent Welds
The figure in brackets is the space length. 50 before (100) indicates that the weld is at the beginning. (100) 50 would indicate a space first then a weld although such an arrangement would not represent good practice.

17.2 Weld Positions
1. Flat (down hand) position.
Figure 66

 

 

 

 

 

2.  Horizontal position.
Figure 67

 

 

 

 

 

3.  Overhead Position
Figure 68

 

                                            
4.  Vertical Position.
Figure 69

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5.  Corner Joint (in flat position)
Figure 70

 

 

6.  T Joint (flat position)
Figure 71