Groove welding symbols are used to show how butt joints are prepared for welding and to detail how the weld is to be applied. When two pieces of metal, other than sheet metal or thin sections, are butted together for welding they usually have some form of a groove to allow the weld to penetrate into or through the joint.
The groove is formed by preparing the edges to be welded with a bevel edge, chamfer edge, double bevel edge, J groove edge or double j groove edge.
When the butt joint has no edge preparation it is referred to as a square groove.
The typical edge preparations are shown below:
The edge preparations may be assembled as either open root, with a backing bar or by utilizing the back weld or backing weld application.
The open root assembly allows penetration through the joint, while the backing bar is used for easier welding. The backing bar may be removed or may be a part of the joint.
The backing weld is applied before welding and acts as a backing bar, while the back weld is applied after welding to finish the back side of the joint. Before applying the back weld a grinder or other method may be used to prepare a V.
The edge preparations may be assembled in any configuration to form the groove for welding from either one side or both sides. The most common configurations and their basic symbols are shown below.
KEY POINT: If two imaginary lines are drawn parallel to the horizontal line in the above symbols they show the joint shape, this is true for most of the symbols. This can be helpful to remember since symbols on a blueprint do not show the actual joint shape or edge preparation.
KEY POINT: The Groove welding symbols have the same placement relevance on the reference line as the fillet weld. Symbols on the bottom of the reference line mean weld the side of the joint the arrow is touching or pointing to, while symbols on the top of the reference line mean weld the opposite side of where the arrow is touching or pointing to.
If it is not clear always ask someone; reworking welds is costly and time consuming.