I believe from some guidelines, that failure normally occurs on the asymmetric discontinuity (e.g. branch connection, shoe connection). Normally, it recommends full encirclement reinforcement to make the connection axisymmetric. But on the plain normally, there is no failure (not sure if there is a new development in recent studies). Another recommendation is to use a forged tee and sweepolet for new system. But since it's an existing system, another solution is to weld circumferential rings based on the outcome of a detailed AIV study (I believe using FEA).