U-Stamp vs. PP-Stamp

[BChemE]

I would appreciate any help in clarifying the following:

If a system is to contain a pressure vessel somewhere along it, and I'd like to add a fitting (anywhere from 1/4" to 4" tubing) does the fitting require any sort of stamp in order for the fitting to be welded somewhere along that system. If yes, what kind of stamp?

Also, is it true that only piping that has to be evaluated as coded pipe (PP-stamp?) is that which is on the first weld from pressure vessels?

Thanks.

 

[deanc]

Question 1-"R" stamp.
Question 2- Depends on the boundries of the construction code and the application. A "S" stamp holder can do PP work.