To improve the efficiency of piping, recently the pre-fabrication piping system has been introduced, and much attention has been paid to TBPs which can replace Tee-joint. Forming and forming analysis on TBPs made from Carbon steel pipes for pressure service(KS D 3562 Sch40) and Stainless steel pipes(KS D 3576 20S) have been conducted to determine working pressure. Forming and forming analysis objects are $32A{ imes}25A$, $40A{ imes}25A$, $40A{ imes}32A$, $50A{ imes}25A$, $50A{ imes}32A$, $50A{ imes}40A$ TBPs.