allowable loads at for API650 tank with tank diameter lower than 36m (120ft)

[GioviSAN]

Hello to everybody!
API650 Appendix P is applicable in order to estimate expansion and rotation at nozzles and then check allowable loads at nozzles "for tanks larger than 36m in diameter, and only when specified by Purchaser for tanks 36m in diameter and smaller".
I have a question...
How do you proceed if the tank diameter is lower than 36m? What procedure for nozzle loads check do you apply?

Thanks for your cooperation.

 

[JStephen]

Several years ago, I was reading the technical papers that Appendix P was based on. One of the simplifying assumptions made was that shell thickness was proportional to pressure. For larger tanks this is true, to a fair extent, with some allowance for plate thicknesses being rounded up. For smaller tanks, this is not true. I sent an inquiry in to API, perhaps others did as well, and that statement about using it only on tanks over 120' was added at that time.

Assuming that the 120' limitation was in fact a reflection of that assumption, the key factor would be whether shell thickness for your tank is controlled by calculated thickness or by the minimum thickness. If it's controlled by calculated thickness, I would think you could go ahead and use it.

 

[inammanj123]

For tank smaller than 36 m nozzle loadings can be checked using WRC 297, you can use "CODECALC" for this purpose. You an also use ANSYS workbench, but WRC 297 is a better option, as it will take less time than ANSYS.Also alot of EPC clients are asking for WRC 297.

Regards,
Inam

 

[Soave]

Other question about this calculation:

If the ration of Nozzle Diameter / Nozzle Thickness is smaller than 20 (WRC 297 Limit), How Can I proceed with calculations?? Only FEA is accepted calculation?

Thank you!

 

[fegenbush]

It is possible to use WRC 107 or WRC 537 to calculate these allowable loads. WRC 537 is the most recent version of this report.

 

[Soave]

fegenbush thank you for your advice,


but unfortunately my tank is large to its thickness, the ratio Rm/T is greater than 300. (WRC 107 Limit)
At WRC 537 this value can be greater?


Thank you again.