koshy-
Strictly speaking, ASME PCC is a standard, not a code (the second "C" stands for "committee"). And PCC-2 covers nonmetallic repairs as one of several methods. It is a standard which provides guidance, but must be worked within jurisdictional requirements and must be consistent with the original code of construction.
As metengr points out, it would be quite surprising to me if an AI were to approve a nonmetallic repair to a stamped vessel. There's just very little precedent and its difficult to tie metallic materials to the nonmetallic from a Section VIII perspective. In my experience NMR's are primarily used on piping and pipelines.
Having said that, I've seen NMR's on vessels, so clearly it can be and has been done. Physically. Now, the jurisdictional legality of one installation I've seen in a US state was questionable. The jurisdiction with authority over that site is fairly savvy, although understandably conservative. I would consider approaching them for approval for such a repair, and I suspect that upon consideration they might approve. But I would only use this approach as a short term fix, with the expectation that it be repaired "properly" at the next planned shutdown.
If I were approached for a NMR to a vessel, say a thinned boot on a horizontal vessel, I'd certainly entertain the proposal. If it were for one of our overseas operations with minimal or no jurisdictional oversight that would simplify the decision making, but at the end of the day, me or people I know are taking responsible charge for that repair and its safety relative to the people exposed to a potential failure. My company has some decent oversight of NMR's both in terms of situations where they may be used, and on specific products which we've independently tested and vetted. Just keep in mind that a salesman's promises as to the product's characteristics are put forth by somebody with an inherent conflict of interest. Independent testing can weed some poor performers out pretty quickly.
Given that you self-identify as a chemical engineer, and the fact that you are asking for mechanical engineering help not from within your own organization but from an internet forum with anonymous replies, and further that what you are proposing is, while not unheard of, certainly not conventional, I'll suggest that you are probably best off going with a metallic repair designed by competent mechanical engineers and installed by competent craftsmen.
