ASME sect VIII nozzle reinforcement calc.

[jeff3300]

Quick question when calculating area supplied by the repad towards nozzle compensation:

Formula from UG.37.1
A5= (Dp-d-2tn)tefr4

I have been using the inside (corroded) diameter of the nozzle as "d"
but my answer key is showing "d" as being the origional outside diameter of the nozzle?Which is correct?

 

[fegenbush]

Per UG-37,

d = finished diameter of circular opening or finished dimension (chord length at midsurface of thickness excluding excess thickness available for reinforcement) of nonradial opening in the plane under consideration, in. (mm) [see Figs. UG-37.1 and UG-40]

To answer your question, neither one is correct. You may view the OD of the nozzle as the dimension, but it is, in fact, the ID of the shell cutout.

 

[doct9960]

jeff3300,

Your answer is correct.

Go look into some of the example problems in PTB-4 and Appendix L-7.4 (pre-2013 Code edition).

 

[Duwe6]

ASME hairsplitting [and I have been makeing good $$ doing that]:

The area that requires reinforcement is indeed the as-corroded ID of the nozzle.
However, the question is asking what the repad contributes to that reinforcement. After the full-penn weld, the effective inner limit of your repad is the OD of whatever nozz you are working on.

 

[SnTMan]

Notice the 2tn term. d is as defined, diameter of the finished opening. 2tn accounts for the nozzle wall, i.e. nozzle OD = d+2tn. So, Dp-(d+2tn)....

But also see UG-40 for various configurations.

jeff3300, you've got an answer key? How nice. I could sure use one for the design I'm currently on

Regards,

Mike

 

[jeff3300]

Thanks for the feedback everyone, it was very helpful.
Appendix L-7.4 was an excellent resource I had overlooked.