How do we calculate?
ASME B31.3 para. 304.3.3 area replacement method (90° branch): required area A1 = th × d1. Excess thickness in the run pipe A2 = (2d2 − d1)(Th − th − c), excess thickness in the branch A3 = 2L4(Tb − tb − c); L4 = min(2.5(Th − c), 2.5(Tb − c) + Tr). If A2 + A3 < A1, the missing area is provided by a reinforcement pad (A4). A 12.5% mill tolerance is applied to the wall thicknesses.
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