API 650, APPENDIX P

For given L/2a = 1.0 , Two Graphs are available in Appendix P to calculate Stiffness Co-efficient for Radial Load .

1. Reinforcement on Shell (Fig. P-2A)
2. Reinforcemnt on Neck Only (Fig. P-2G)

Which graph we have to follow & why ????

Reinforcing on the Shell assumes there is a pad. Further the pad thickness is assumed to be equal to the shell thickness and the pad diameter is twice the diameter of the nozzle.

Reinforcing on the nozzle means the nozzle has sufficient material to satisfy "area replacement" requirements without a pad.

These assumptions are implicit in the curves presented in Appendix P.