Branch Reinforcement

Branch reinforcement

Preliminary. This result needs engineering review before anyone uses it. It is one welded branch under internal pressure. It is not an extruded outlet, and it does not check a second opening nearby.

Formula

t = P × D / (2 × (S × E × W + P × Y))

d1 = (Db − 2 × (Tb × (1 − mill) − c)) / sin β

A1 = th × d1 × (2 − sin β)

d2 = the greater of d1 and (Tb net + Th net + d1 / 2), and not more than Dh

A2 = (2 × d2 − d1) × (Th net − th)

L4 = the smaller of 2.5 × Th net and 2.5 × Tb net + Tr

A3 = 2 × L4 × (Tb net − tb) / sin β × the branch stress ratio

A4 = 2 × pad width inside the zone × (Tr − c) × the pad stress ratio

Equation (3a) gives th for the header and tb for the branch. You enter S, E, W and Y. A blank branch S, E, W or Y uses the header value. Mill undertolerance reduces both nominal walls before c is subtracted. Th net and Tb net are those remainders. β is the smaller angle between the branch axis and the header axis.

The connection passes when A2 + A3 + A4 is at least A1. A4 is the pad only. Fillet welds are not included. The stress ratio is the allowable stress of that part divided by the header allowable stress, and it is not taken above 1. Leave the pad blank to size one when the pipes alone are short. The trial pad thickness is then the header wall after mill and c.

W starts at 1.0. Y starts at 0.4. The mill field starts at 12.5%. Those are starting values, not a completed material specification. Check them.