📖[PDF] Welding Symbols On Drawings by E N Gregory | Perlego (2024)

It is sometimes argued that it is unnecessary to specify welds on drawings and that the welder should be relied upon to deposit a suitable weld. This practice can be extremely risky because the type and size of the weld must be appropriate for the parent material and service conditions of the fabrication, and the necessary information and data are normally available only in the design office.

Figure 1.1 illustrates (a) the instruction ‘weld here’ and (b–d) three ways to follow this instruction.

The instruction ‘weld here’, illustrated in Fig. 1.1(a), is rarely seen on a drawing because it is open to a number of different interpretations as shown in Fig.1.1(b), (c) and (d).

Figure 1.1(b) shows a single fillet weld. This weld is simple and therefore cheap to apply but could be seriously deficient in performance.

Figure 1.1(c) shows a double fillet weld, which takes longer to apply. Unless access is available to both sides of the joint, it will be impossible to weld it.

Figure 1.1(d) illustrates a T-butt/groove weld. This weld normally requires edge preparation on a horizontal member, and therefore is more complex and expensive. However, it may be essential for certain service conditions.

It can be seen from the previous examples that major problems will arise unless welded joints are carefully specified by the design office. The situation is particularly critical where, for example, work is placed with a subcontractor and the instructions need to be especially precise.

When it is required to indicate a weld on a drawing, it may seem that the weld can simply be drawn as it will appear. In the majority of cases, symbolic representation can be used to cut down the time needed to complete the drawing and improve clarity.

To save time in drawing the edge preparation for a butt/groove weld or the shape and size of a fillet weld, a set of weld symbols can be used. These symbols are placed on a horizontal reference line. This line is attached to an arrow line which points to the location of the weld (see Fig. 2.1). In the ISO system there are two parallel reference lines, one solid and one dashed. In the AWS system a solid reference line is used.

See Also

Weld Callouts - Welding Standards & Engineering Drawings

Apart from weld symbols placed on the reference line, additional information can be supplied adjacent to the tail which is generally omitted when not required.

The arrow line can point in any direction as shown in Fig. 2.2. This is so that it can locate welds in any welding position, for example flat or overhead. The arrow line is never drawn horizontally because this would make it appear to be a continuation of the reference line, which is always horizontal.

It is conventional practice to refer to the opposite sides of a welded joint as the arrow side and the other side (see Fig. 2.3).

In the ISO system a weld on the arrow side is indicated by placing the weld symbol on the solid reference line and a weld on the other side has the symbol on the dashed line, as shown in Fig. 2.4.

In the AWS system the weld symbol for a weld on the arrow side is placed below the line and for a weld on the other side the symbol is placed above the line.

In the ISO system the dashed line can be drawn above or below the solid line but the symbols on the solid line always refer to the arrow side of the joint. Symbols on the dashed line indicate a weld on the other side. It is recommended that the solid line is always drawn above the dashed line as standard practice. If a weld is made on both sides, as in a double fillet weld, the weld symbol is placed on both sides of the reference line or lines, in which case, in the ISO system, the dashed line can be omitted.

Figure 2.5 (a–f) shows the use of symbols to indicate the type and size of a T-butt weld and a double fillet weld.

Without using weld symbols, Fig. 2.5(a) shows a drawing of a T- butt weld with 6 mm leg length fillet welds and with the edge preparation shown.

Figure 2.5(b) shows the T-butt weld represented by symbols which convey all the information according to the ISO standard.

Figure 2.5(c) shows the T-butt weld indicated by weld symbols for the AWS standard.

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