Unit 16 Groove Welds 209 Joint spacers are metal parts inserted in the joint root as backing and to maintain the root opening during welding, Figure 16-26. Joint spacers are sometimes used, especially if the weld is in thick material and the mini- mum possible V-angle is specified. In such welds, the root must be gouged out completely, including the spacer bar, before the second side of the groove is welded. Runoff weld tabs provide an extension of the groove beyond the pieces being joined when a full-length groove weld is specified, Figure 16-27. Runoff tabs provide a place to strike the arc and material at the end of the weld to eliminate the weld crater. The angle or contour of the runoff weld tab must be identical to that of the groove. Since welding symbols give no indication of the backing, spacer, or extension bar requirements, note that unless covered by reference to AWS prequalified joints or fabricators’ standards, special sketches of the weld profile are provided. Flare-Groove Welds Flare-groove welds are used to join round or formed metal parts. The groove that is formed when curved surfaces are placed together does not have straight sides on one or both members. Two round steel bars laid side-by-side, such as reinforcing rod, have sides that are curved. The joint that is formed does not have straight sides like a V-groove weld. Figure 16-28 shows an example of a flare-V- groove weld. Either two round parts (members) or two formed parts (members) can be used to form the V-groove. The symbol for the flare-V-groove weld can be placed on a single side, or the symbol can indicate that the weld should be made on both sides. The depth dimension for a flare-V-groove weld is given as the distance from the top of the member to the point of tangency (where it touches the other member or part). Figure 16-29 shows a dimension of .31 to the point of tangency and a weld size of .25. Notice that the weld size is placed in parentheses. The weld size is the distance from the surface of the part to the root of the weld. Figure 16-26. Joint spacers may be specified when thick sections are welded. In such welds, the root and joint spacers are gouged out before the second side of the groove is welded. Specifications are shown in the reference line tail. Figure 16-27. A runoff weld tab is used when a full-length groove weld is specified. Specifications in the reference line tail or sketches on the drawing may be used to indicate a runoff weld tab. Runoff bar Runoff tab Runout plate or backing extension Desired weld Joint Symbol SPEC. 35A Figure 16-28. A flare-V-groove weld applied to a joint formed by two round parts. 1.00 .75 1.00 (.75)