PD 5500 Annex G Used For Vessel Flexibility Interpretation

[JamesDUK]

Hi,
Trying to make sure I'm not doing something really dumb. Working with pipe support guys to see how a new piping arrangement effects an existing pressure vessel nozzle. Nozzle is on a cylindrical shell, perpendicular to the shell.
Looking to calculate the vessel spring constant (flexibility) for the pipe support guys to use. Can I simply take an arbitrary load, apply it to the nozzle using PD5500 annex G (specifically G.2.4.2) get a deflection, then divide by the original load to get a constant in mm/N?
Seems a little too straight forward, hence the query?

 

[MrPDes]

I wouldn't recommend using PD5500 Appendix G for flexibility without experience or testing.

PD5500 calculates a deflection between half and twenty times what you would get from an FEA analysis (depending on geometry). The enquiry case 5500/137 in the back of PD5500 appears to have allot of detailed work dedicated to nozzle flexibility so may yield accurate results.

WRC 297 is allot more accurate for pipe flexibility but still has certain geometries that are more rigid than FEA.

They are all calculated based no elastic properties of the material, so your method of finding the spring constant seems reasonable.