Single Nozzles

Vessel and nozzle stiffnesses – for more realistic system calculations

The realistic representation of vessel nozzles is crucial for reliable piping and vessel calculations. Instead of idealized, rigid connections, the creation of stiffness matrices for vessel nozzles enables precise recording of the actual deformation and load transfer behaviour in the transition area between the nozzle and the vessel shell or bottom.

Based on the realistic geometry (diameter, wall thicknesses, embedment length, reinforcements), the material properties, and all relevant load components, we determine the elastic properties of the pipe connection using analytical methods based on calculation algorithms described in international standards.

In the event of a failure to comply with the valid ranges, we first use the finite element method (FEM) in accordance with the proven, internationally recognized substructure method to determine a 6×6 stiffness matrix that describes the complete linear force-displacement behavior of the sleeve in all six degrees of freedom.

From the diagonal elements of the matrix, we derive the six practical nozzle stiffnesses directly
• axial stiffness
• two radial stiffnesses
• two bending stiffnesses
• one torsional stiffness

With these six nozzle stiffness values determined by us, you can easily integrate your pipes into piping and overall models in accordance with standards. If required, we can take coupling effects between forces and moments into account or simplify them in consultation with you to suit the specific application.

With the nozzle stiffness values we have determined, you obtain
more realistic deformations, which you can use to determine, for example

• adjustment loads and travel reserves of spring and constant hangers and
• compensator movements
  

(especially in thin-walled systems) more accurately.

The stresses calculated using nozzle stiffnesses are also significantly more realistic and enable more reliable assessments of strength, fatigue, creep, vibration, stability, and structural integrity, as well as the determination of (remaining) service life, and should therefore lead to more economical designs for your systems. In addition, previous safety reserves become transparent and overconservatism is avoided. The stiffness values we determine are compatible with common calculation programs and regulations such as EN 13445, AD 2000 or ASME.

Your added benefit: reliable connection data, improved system models, and greater planning reliability—from detailed analysis to overall calculation.