Flexibility factors for nozzles in the knuckle region of dished pressure vessel heads

Nozzles in the spherical part of pressure vessel heads may be designed according to BS5500 and/or with the solutions based on the work of Bijlaard. However, no solution has been available so far if the nozzle is in the knuckle region of the pressure vessel head. Furthermore the restraint forces and moments at the nozzles and thus the stresses due to them may be reduced if the flexibility of the support at the nozzle is taken into account in the calculation. This paper reports on the flexibilities and how they can be taken into account in the design.