Interpretation of UG-32(i) ASME F&D Heads

[GinBread]

It seems to me that the standard ASME F&D heads that most head companies offer, where the ICR = 100% OD, would violate UG-32(i) if you were to apply any amount of corrosion allowance to the head in your design calculations. Is my understanding correct? If not, could you please elaborate / point me to other parts of the code to justify?

UG-32(i) states:

(i) The inside crown radius to which an unstayed head
is dished shall be not greater than the outside diameter of
the skirt of the head. The inside knuckle radius of a torispherical
head shall be not less than 6% of the outside
diameter of the skirt of the head but in no case less than
3 times the head thickness.

 

[TGS4]

You've used a number of acronyms that may not be universally understood. Please detail them in your post.

You'll have to forgive me, but I don't particularly follow your point. Is there some math that you can detail out? What do you mean by "most companies"?

 

[cbPVme]

See interpretation VIII-1-86-175

Question (1): Does a torispherical head satisfy Code requirements if the inside crown radius exceeds the outside diameter in the corroded condition but meets the requirement of UG-32(j) in the noncorroded condition?

Reply (1): No; see Appendix 1-4.

Question (2): If the answer to Question (1) above is no, which paragraph of the Code should the thickness of the torispherical head be calculated?

Reply (2): The torispherical head must meet the requirements of UG-32.

 

[GinBread]

See interpretation VIII-1-86-175

Question (1): Does a torispherical head satisfy Code requirements if the inside crown radius exceeds the outside diameter in the corroded condition but meets the requirement of UG-32(j) in the noncorroded condition?

Reply (1): No; see Appendix 1-4.

Question (2): If the answer to Question (1) above is no, which paragraph of the Code should the thickness of the torispherical head be calculated?

Reply (2): The torispherical head must meet the requirements of UG-32.

This pretty much straight up answers it. Thank you.

 

[GinBread]

You've used a number of acronyms that may not be universally understood. Please detail them in your post.

You'll have to forgive me, but I don't particularly follow your point. Is there some math that you can detail out? What do you mean by "most companies"?

Sorry about that!

Here are the acronyms as follows:

F&D: Flanged and Dished
ICR: Inside Crown Radius, synonymous with Dish Radius (DR) in some catalogs
OD: Outside Diameter

The math as I understand UG-32(i) is just: ICR ≤ OD

And by most companies I mean that every single head manufacturer that I've come across that offers ASME F&D heads, from companies like Bethlehem Steel, Fort Worth F&D Head Company, Tank Components Industries, Paul Mueller Company, and so on all state that their "ASME F&D" heads are made to where the ICR = OD.