Branch Connection Reinforcement (Area Replacement, ASME B31.1)

The area-replacement check of ASME B31.1 para 104.3.1 (and B31.3 304.3 for process). The metal removed, A_required = t_rh x d1 x (2 - sin beta), is made up by the excess wall in the run (A1) and branch (A2) within the reinforcement zone; a shortfall is the pad area to add. An NPS 6 Sch 40 run with an NPS 2 Sch 40 branch at t_rh 0.10 is adequate on run excess alone (A1 0.37 >= A_req 0.21); raise the required wall and the same opening flips to needing a repad. The required walls come from the pressure design; the engineer of record and the AHJ govern. The area balance, not a stamped branch-connection design.

d1 = (branch_od - 2 x branch_wall) / sin(beta); A_required = run_treq x d1 x (2 - sin beta); d2 = max(d1, branch_wall + run_wall + d1/2); L4 = min(2.5 x run_wall, 2.5 x branch_wall); A1 = (2 d2 - d1)(run_wall - run_treq); A2 = 2 L4 (branch_wall - branch_treq); adequate when A1 + A2 >= A_required, else pad_area = A_required - (A1 + A2).

ASME B31.1 para 104.3.1 branch-connection reinforcement (and B31.3 304.3 for process piping), by name; the area-replacement relations are read from the code's figure.

The area-replacement relations are the standard branch-reinforcement balance, widely republished in piping-design texts; the required wall thicknesses come from the pressure design.

Estimate. AHJ and licensed professional govern.

Field names used by the API: run_od_in, run_wall_in, run_treq_in, branch_od_in, branch_wall_in, branch_treq_in, beta_deg, a_required_in2, a_run_in2, pad_area_in2

• Required walls run and branch required walls come from the pressure design (pipe-pressure-rating), not assumed hereASME B31.1 / B31.3
• Reinforcement zone half-width d2 = max(d1, T_b + T_h + d1/2); height L4 = min(2.5 T_h, 2.5 T_b) (no pad)ASME B31.1 104.3.1
• Governance the area balance is a screening check; the engineer of record and the AHJ govern the branch-connection designASME B31.1