APP. XI "design for bolted flange of class 2 & 3 " does not cover design for class 1 vessel.What are the code (NB) requirements for bolted flange (Integral ring type) design.Kindly give reference.

regards

I am a new user of Section III code and have browsed the code for the same problem.

I got relatively convinced by going through the clauses NB-3362, NC-3362 and ND-3362 as to why Mandatory Appendix XI has been titled only for Classes 2, 3 and MC.

For Class 1 vessels the flanges shall conform to ASME B16.5. For class 2 and class 3 vessels, the flanges need not always conform to ASME B16.5 and the dimensions can be further optimized but they have to conform to Appendix XI.
Contrary to this, for body to bonnet joints in class 1 valves (NB-3546), bolted flanges can be designed as per Appendix XI and need not always conform to ASME B16.5

So, in a nutshell, my understanding is, for class 2 and class 3 components flanges can always be designed as per Appendix XI but for class 1 components flanges can be designed as per appendix XI only when it is allowed in code Subsection NB. That is why the title of mandatory appendix does not contain class 1.

I am afraid that my explanation is long and boring. Experienced users can review my understanding and comment please.

Isn't the class 1 vessel subject to Stress analysis and all kind of fancy calculations that will replace the old school Appendix Flange calculation?

Where are the experienced RPEs, show your posts and impress us with your bright experience, please.

DK