Discussion on non-destructive testing for large-diameter vessels
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How to understand 3.2.10.2.4(1) of the major code: The non-destructive testing methods, testing ratios, and acceptance criteria for the welded joints of pressure vessel nozzles with a nominal diameter of 250 mm or greater are the same as those required for the welded joints of the pressure vessel shell. This sentence? ? ? ? Do welds of categories C and D also require non-destructive testing? ? ? ? ? ? Seek guidance from experts! ! ! !
In my opinion, the connections with DN>=250 and their flanges are also the main pressure-bearing components; that is why the standards specify that these connections of categories C and D must also be inspected, on the same basis as those of categories A and B. For devices that undergo 100% testing for Class AB, we generally also require UT testing for Class CD components with larger connections, while those Class CD components with smaller connections are subjected to surface testing. (Of course, whether devices of this type can be classified as Class C is another matter.) For those of Classes AB that are only subject to partial testing, follow the procedures outlined above.
This one is written in standard language; the secretaries’ writing skills are too poor. . . . Another one that can be understood in multiple ways. . .
That makes sense. Similar words can be found on page 335 of 150. However, it is specified in 150 that they are either a coupling joint between pipes, or a coupling joint between a pipe and a high-neck flange, and both of these joints belong to Class B. So what I’m curious about is, if it’s not a mating connector but an ordinary Class D connector, is non-destructive testing still required? I work in design; when encountering such a situation, how should I indicate it in the drawings?
Classes C and D correspond to the joints between the take over and the shell, and RT or UT is generally not performed on them, unless specifically required by the design. As mentioned in 150, the handling of the joint connections is to be carried out in accordance with the requirements of the housing. However, based on my understanding of what is stated in 150, this applies only to Class B welds; if the pipe fitting is rolled, it would be Class A, but this aspect isn’t specified there. The term \"tolerance specification\" can be understood as including categories A and B. The standards represent the minimum requirements; when designing, we can set stricter testing requirements than those specified by the standards, based on the actual operating conditions.
This means that connectors with a diameter greater than 250 mm also need to be inspected using the non-destructive testing methods applicable to the shell. Moreover, the weld joints of the pressure vessel connections are of type A/B welds, not type CD welds. In fact, what this sentence means is that if the diameter of the nozzle is 250 mm or more and there are welds on the nozzle, those welds must be subject to non-destructive testing.
The national standards specify only the minimum requirements; generally, CDE-type welds do not require radiographic or ultrasonic testing. Refer to clauses 150.4-10.4-a) and b); there are requirements for testing for CDE categories. These are merely **things that are required by regulations. For example, regarding the containers you create, if you think that certain CDE-type welds need to be inspected, you can indicate in the drawings the inspection standards you require. It is essential to understand what Class AB welds are and what Class CD welds are.