Dear all,

I have been said to justify all the welded attachments in a HP steam system of a Combined Cycle Plant (B31.1) by means of Code Cases N-318/N-392. I am facing some problems I am not very sure how to resolve and would be grateful for any help:

- The code cases are intended to use only for attachments to straight pipe but I have some trunnions welded to elbows. Do you think that the method is conservative for elbows or on the contrary if I use it I may understimate the stresses? For example MW Kellogg method is usually used for trunnions on elbows but I think it was created for straight pipes only...
- The Code Cases do not consider any reinforcing pad. As I have pads in some cases. I thought of using a pipe of "equivalent" thickness equal to pipe real thickness+pad thickness. Is there any recommendation about the minimum pad dimensions in order to assure that the local stresses calculated with this "equivalent" thickness will be correct? (I suppose that the pad must cover the whole area affected by the local stresses, which is that area?)


Thank you and best regards,