API 653 / 650 Nozzle Local Discontinuity Code Allowable 1

[Engineer Rain]

Hello,

I have a question regarding API 653 / API 650 that I was hoping someone may be kind enough to answer.

With regard to the maximum allowable stress at shell penetrations, is there any up rating factor over and above the stresses listed from table 4.1 of the code?

I am working a stress analysis of a storage tank and was thinking that there may be some allowed increase for nozzle penetrations etc. similar to the 1.5S, 3S system used under ASME VIII div 2.

It seems nearly impossible to have manways etc. by using the API 653 listed stresses from table 4.1

Thanks.

 

[JStephen]

Nozzle reinforcement is based on area-replacement methods, and it would generally be assumed that actual peak stresses might be substantially higher than the average allowable stresses. If the nozzle reinforcement complies with the code requirement, there is no code limitation on the actual stresses that can occur.
Similar issues arise at the chime area (for example, a plastic hinge in the floor plate is assumed, but plastic hinge obviously exceeds the allowable stress).
Annex P of API-650 addresses this somewhat with regard to external loading on nozzles.

 

[Engineer Rain]

Thanks for the response.