Welding Symbols

Objective: SWBAT Identify and explain welding symbols.

Introduction

Welding symbols are used on drawings, project specs, and welding procedure specifications.

They use a series of symbols to indicate the joint configuration and weld type, location, size, and length required.

Welding symbols are part of the language of welding. Welders must be able to understand this language to ensure their welds meet the design specs.

Confused Yet?

Welding Symbol Base

The base for all welding symbols is the always horizontal reference line with and arrow at one end.

The arrow which can come either end of the reference line points to the location for which the welding symbol applies.

Information on the reference line is always read from left to right.

Welding Symbol Base

The opposite end of the arrow, or the tail is used for information that aids in the making of the weld but does not have its owns place on the symbol. The tail can be omitted when not needed.

Symbols for Welds

The weld symbol is used to identify the type of weld to be made, signify a basic type of weld joint, or identify the type of joint preparation needed.

Weld Symbol Locations

The welding symbol distinguishes between the two sides of a weld joint by using the arrow and the space above and below the reference line.

Information appearing above the reference line refers the opposite side of the joint that the arrow is pointing to.

Information appearing below the reference line refers to the side of the joint that the arrow is pointing to.

Weld Symbol Locations

Weld symbols appearing on both sides of the reference line refer to both sides of the weld joint.

Weld Symbol Locations

Groove Preparation

The shape of the groove weld symbol indicates how the groove is to be prepared. In the case of bevel groove, and J-groove weld symbols only one of the joint members to be welded is prepared.

The arrow indicates which member is to be prepared by breaking towards that member.

Combining Weld Symbols

When more than one type of weld is to be made on the same joint, it is necessary to combine weld symbols.

The weld symbol is always placed on top of the groove weld symbol, just as it would be on the actual weld.

Size and Dimensions

Unless defined in a drawing note, the size data for a fillet weld is always shown to the left of the symbol for which it applies.

The length of the weld is always shown to the right of the symbol.

Size and Dimensions

If the weld is to be an intermittent weld, the length (length of each segment) and the pitch (center to center spacing) are shown with a dash.

The length is always shown first and the pitch second.

Size and Dimensions

If the welds are to be on both sides of the welds they can be back to back or they can be staggered.

If the welds are back to back the symbols are lined up evenly on both sides of the reference line.

If the welds are to be staggered the symbols above and below the reference line are offset.

Size and DimensionsA groove weld is a weld made in the groove when one or more of the

members has been beveled.

There are several items to be considered when sizing groove welds.

Groove preparation is the depth to which the groove penetrates into the base metal.

When the groove prep extends all the way through the joint, no prep size needs to be shown.

When the groove prep extends only part of the way through the joint, the depth of groove is shown to the left of the symbol.

Size and Dimensions

If a root opening is required, the root opening dimension of the groove weld is shown inside the groove weld symbol.

Size and Dimensions

The angle for the type of groove is shown above or below the welding symbol, depending on whether the symbol is above or below the reference line.

Supplemental SymbolsSupplemental symbols are used to convey special instructions pertaining to the welding symbol.

Weld-all-around is used when a weld is to extend completely around the weld joint.

Field weld symbol indicates the weld is to be made on location.

When the face of the weld must have a finished shape that is not the as-welded condition a contour symbol is used.

When complete joint penetration is required a melt through symbol is used.

Surfacing Weld Symbols

Surfacing weld symbol always on arrow side

Applies to single or multiple layers

Size (thickness) to left of symbol

Location, direction of welding in tail or a drawing reference

The spot weld symbol may straddle the reference line when there is no side significance, or be placed on either side if significant.

Spot size or strength to left of symbol

Spot Weld Symbols

The back and backing weld symbols are identical. The sequence of welding determines which designation applies.

Back weld made after groove weld

Backing weld made before groove weld

Back and Backing Welds

Weld Symbols Summary

Welding symbols are a language expressed in graphic format and are used to convey precise instructions about how a weld is to be made.

By learning these symbols and the basic rules for applying them, a welder can easily understand how to precisely prepare and make the required welds.

Understanding these symbols is essential when using WPSs and Drawings.