THE APPLICATION OF WELDING SYMBOLS TO WORKING DRAWINGS

The Application Of Welding Symbols To Working Drawings

The following notes are intended to serve as a guide to using the more generally used welding symbols on engineering drawings to represent the more basic types of welded joints. When numerous welds are involved in a complex joint, it is typically easier to detail the structure on different design sheets.

A symbol is assigned to each type of weld in Table 1. It's important to note that the symbol represents the shape of the weld, or edge preparation, rather than any specific welding procedure. It also doesn't define the number of runs to be deposited or whether or not a root gap or backing material should be employed. On a welding procedure schedule for the specific task, these data would be supplied.

Tabel 1. Elementary Weld Symbol

The shape of the weld surface on the drawing may need to be specified as flat, convex, or concave, and a supplementary symbol, illustrated in Table 2, is then appended to the elementary symbol. Table 3 shows an example of each type of weld surface application.

Tabel 2. Supplementary Symbol

Tabel 3. Examples of Application of Supplementary Symbols

A joint can also be constructed using one type of weld on one surface and another on the other, in which case the elementary symbols for each type of weld utilized are put together. The final example in Table 3 is a single-V butt weld with a backing run that requires a flat finish on both surfaces.

A reference line and an arrow line are used to apply a welding sign to a drawing, as shown in Fig. 1. The reference line should be drawn parallel to the drawing sheet's bottom edge, and the arrow line should be drawn at an angle to the reference line. The ‘arrow side' of the joint is closer to the arrow head, whereas the ‘other side' is further away.

Fig. 1

As shown in Table 4, the welding sign should be placed on the reference line.

Tabel 4. Significance of The Arrow An The Position of The Weld Symbol

Sketch (a) Because the exterior surface of the weld is on the arrow side of the joint, the symbol for a single-V butt weld is shown below the reference line.

Sketch (b) Because the weld's exterior surface is on the other side of the joint, the identical symbol is shown above the reference line.

Sketch (c) shows the symbol applied to a double-V butt weld.

Sketch (d) shows fillet welds on a cruciform joint where the top weld is on the arrow side and the bottom weld is on the other side.

For drawings in first or third angle projection, the symbol is positioned in the same way.

As seen in Fig. 2, additional symbols can be added to the reference line.

Fig. 2

Welding might be done at the factory or on-site during the installation of the plant. A flag marks the location of a site weld. A circle at the junction of the arrow and the reference line represents a continuous weld all the way around a joint. Both symbols should be added to the drawing if a continuous weld is to be performed on site.