WRC 297 for an 4" nozzle on the Vessel

[MOHAMMED89]

Dear All,

While i running vessel design calculation in PV Elite, For 4" Nozzle the calculation shows Dn/Tn is < 20 . Which is beyond the limitation of WRC 297.

My concerns are:-
1. Whether FEA analysis required for this 4 inch nozzle.??
2. Since the Dn/Tn is less than 20, So no need to perform FEA??
3. WRC 107 run for this same nozzle and it is passing with no warning and error, So is that enough conclude the nozzle are same for the external load etc.??


Your response are highly appreciated.

 

[pdiculous963]

WRC 297 evaluates the stress in the nozzle and in the shell. WRC 107 evaluates the stress in the vessel only. So by running a WRC 107 you are not sure about the stress in the nozzle at the shell to nozzle junction.

My response to your concerns:
1. What does the client require (assuming you are a fabricator)?
2. No, the Dn/Tn ratio does not exempt your from performing FEA.
3. As noted above, the shell is okay, the nozzle may not be.

If you are not a fabricator, but the owner user, this is where some engineering judgement is required. What are the risks involved if the nozzle fails? How high are the nozzle loads? I assume PVElite extrapolates the WRC 297 curves to give you a result. You may be able to justify not performing FEA if the results from the extrapolated curves are relatively low.

 

[DSB123]

Sounds like you are nervous about the results and do not fully understand the basis of WRC297. As such you are asking for advice. In order to be comfortable with your assessment you firstly need to understand fully the limitations of WRC297 and WRC107 and then make an educated judgement of the results from PVElite. As pdiculous963 says "are the results of the PVElite low" such that you can accept them even though the feometry is outside the limits?