Stiffness of Air-Cooled HEX Nozzles?

[KernOily]

Hi guys. Trying to sharpen my pencil on a piping stress model involving an air-cooled heat exchanger. Looking for reasonable flexibilities/stiffnesses for use in modeling the header box nozzles.

I know an air-cooled HEX is pretty flimsy structurally so I believe the use of a nozzle stiffness is a good improvement to improve accuracy of the stress model. Any of you have any stiffness values that I could use as a starting point before I attempt to cook some up?

Thanks guys! Pete

 

[XL83NL]

Is it a design (similar) to (or based on) API 661? You could use the allowable nozzle loads in there as a starting point.

I don’t have stiffness at hand to provide.

 

[KernOily]

Yes it's an API 661 cooler. (Apologies that I didn't mention that initially.) The design does not meet the 661 allowables and thus we need to refine our stress model to add flexibility. The current stress model assumes the nozzles are rigid which is not true. That's why we can't meet the allowables. Expansion joints are not allowed.