Evaluation of End Fillet Details for Hot Tap Fittings Available to Purchase

Service failures in the welded connections of heavy-walled fittings attached to thin-walled line pipe were found to have been caused in part by inadequate attention to the critical need for dimensional balance in the attachment details associated with such components. The basis for present ASME Code specifications for end bevel and fillet weld dimensions of attached reinforcements was reviewed and evaluated. Nominal stresses in hot tap and stopple tee end fillet weld details were evaluated. Revisions to the ASME Code specifications for hot taps, stopples, and saddle-type branch reinforcements are proposed that are intended to prevent similar service failures.