Dear members,

In CAESAR II "Application Guide" pp.9-34(Tutorial B),
Some comments on local vessel stresses are described as follow;

"As a very rough guide for evaluating local vessel stresses, one
can check the code defined stress on the pipe connected to the vessel.
If those stresses are below 6000 psi, the vessel stresses should be OK."

My question is
What is the engineering basis of 6000 psi in above sentence?

Is there any code or paper that evaluates the "6000 psi"?

Thank you.

That 6000 psi limit is one of those “rules of thumb” that you find in in-house engineering design manuals. The code-defined (or CAESAR II-calculated) pipe stress at the nozzle provides no definite estimate of the local vessel stresses but, used in this manner, this 6000 psi limit serves as a quick check to eliminate unnecessary analysis. It is a very conservative first check.

Setting maximum loads on a vessel nozzle is another way to avoid detailed analysis of local stresses. If the vessel group accepts responsibility for an agreed-upon set of nominal loads (in all six degrees of freedom), the piping group can design to these loads rather than convert these loads to stress and go through the ASME VIII Div. 2 analysis. I have seen these data based solely on nozzle size and flange rating. Again, it’s not that you know what the attachment stress is; you just know that the attachment loads are not excessive. A little coordination is a whole lot cheaper than analysis.

Further to Mr. David Diehl's reply, to my knowledge the first mention of the 6,000 psi criteria came from a joint ASME paper by Rossheim-Markl in 1940. Title of the paper is called, "The Significance of, and Suggested Limits for, the Stress in Pipe Lines Due to the Combined Effects of Pressure and Expansion." Both authors once worked at M.W. Kellogg Company, and that was the company I believe first made it into its Piping Mechanical Design Manual. Due to the free migration of stress analysts in the last few decades, other engineering companies began to apply it as well. COADE heard of it in like manner, as Mr. Diehl says.