API 12B Nozzle Loading

[KernOily]

Hi guys. Interested to see what you all have done to handle nozzle loading on API 12B tanks. As far as I know, 12B does not give any guidance regarding allowables. Nozzle loading is significant on this project because the attached piping is hot. We are trying to avoid expansion joints if at all possible.

My initial thought is to use an FEA program such as NozzlePro and then de-rate the calculated allowables by some factor, say 25%, to allow for the presence of the bolts and gasket at the nozzle neck-to-shell connection. 25% is strictly arbitrary and I can't defend that number beyond my seat-of-the-pants.

If this was a 650 tank I would use the full rated FEA allowable since the nozzle neck connection is fully welded to the shell and a repad is usually present, or, if the tank is large enough diameter I use the 650 rules to calculate the allowables. But 12B tanks are bolted, thin shell, el cheapo tanks.

I'd like to hear opinions or thoughts on this or any experience you might have with 12B nozzle loading.

Thanks guys! Pete

 

[Duwe6]

If your 12B nozz will meet the 650 standards - sch80, repad, etc - I'm not sure that I would even derate by 25%. I'd go with the result from NozzPro. Besides being delicate and expensive, expansion joints may require extra maintenance during the tank lifetime. And these joints typically are only rated for about 10K cycles. For Lifetime Cost, or even your 10-year cost, using a large repad or a thickened shell insert will be cheaper than the expansion joint. And a LOT more robust.