Stress indices for ANSI standard B16.11 socket-welding fittings

Stress indices for ANSI standard B16.11 socket-welding tees, 450 elbows, 900 elbows, and couplings are developed for intended use with the Class-1 piping system design rules of Section III--Division 1 of the ASME Boiler and Pressure Vessel Code. Indices are given for the evaluation of appropriate primary stresses, primary-plus-secondary stresses, and peak stresses due to internal pressure, bending-moment loads, and thermal gradients between the fitting and the attached pipe. The proposed indices are based on the dimensional and pressure-burst requirements of the B16.11 standard, the apparent shapes of B16.11 fittings as indicated from a random sampling taken off-the-shelf, the standard pressure-temperature ratings of the fittings, and on current stress indices now in the Code for similar butt-welding fittings. Specific recommendations are made for issuing the new stress indices in a Code case. (auth)