Pressure Vessel Nozzle Terminology Reference
Concise reference of nozzle terminology — radial nozzle, non-radial nozzle, reinforcing pad, forged insert, nozzle neck, flange face, flexibility factor.
Nozzle types
- Radial nozzle: nozzle axis perpendicular to the shell surface, passing through the centre
- Non-radial nozzle: nozzle axis at an angle to the shell normal (hill-side, offset)
- Insert nozzle: nozzle forged or machined as an integral part of the shell reinforcement
- Reinforcing pad (compensation plate): a plate welded around the nozzle opening to replace removed material
- Self-reinforced nozzle: nozzle with thickened neck that provides integral reinforcement
Nozzle components
- Nozzle neck: the cylindrical pipe section between the shell and the flange
- Nozzle-to-shell junction: the weld region where the nozzle meets the vessel shell
- Inner corner: the internal intersection of the nozzle and shell — typically the highest stress location
- Outer corner: the external intersection of the nozzle and shell
- Flange face: the machined surface at the nozzle end for the bolted connection
Nozzle flexibility
- Flexibility factor: relates the applied moment to the nozzle rotation, accounting for shell deformation
- A flexible shell reduces the effective nozzle stiffness and the piping loads transmitted to the nozzle
- Flexibility factors are used in pipe stress analysis to account for vessel shell compliance
- Ignoring nozzle flexibility overestimates piping loads on the nozzle