Nozzle(Large Opening) needs to be welded with 14 mm thk Main shell In this case Cat. "D" type joint req. PHT ?
Does code specify any caluse for disimilar thk .?
I ve read UW-40 But Pl. Somebody can help me in Interpretion.

Nirai,

You should always start with UW-2.

You need to read the applicable paragrahs for the material. If you are looking for ferritic steel, go to UCS-56, the footnotes to the table will tell you.

UW-40 is then the technical details.

Or you ask your Authorized Inspector. he should be able to give you a comprehensive overview of the requirements applicable to your products.

DK