AS PER UW-11(A)(2),
ALL BUTT WELDS WHEN NOMINAL THK. EXCEEDS 38 mm. needs rt.
when designer says that rt -full & thk. is less than 38,vessel is not lethal,
i understands that category A joints only will be tested by 100% rt
category B -no rt
is it correct?

category B joints only in Nozzles or communicating chambers (dia <10") are exempted. other category B joints, such as C seams within the main shell are required to be RT'ed

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Raghuram

I agree, Full RT is full RT of all butt joints as specified in UW-11(a).
Circumferential welds, when type 1 or 2 welds are subject to full RT as well.

This should be RT1 on the nameplate, what the purchaser will look for.

When the purchaser does not require Full RT, maybe RT2 would be acceptable for him. In this case the Category B joints are not required to be full RT, only spot per UW-11a5b.
This is certainly something the designer may select.

However, the designer should clearly specify what he is specifying: Full RT, or full RT of Cat A, and spot of cat. B welds, or whatever.

DK

Attention.
From the content of your question I understand you might have misinterpreted UW-11(a). Please read all the subpara. (2) ......1.1/2 in or exceed thk prescribed in UCS-57, UNF-57, UHA-33, UCL-35 or UCL-36. For example UCS-57 requires PNo.1, RT Full for thk above 1.1/4 in Read other PNos. as well