How should the minimum wall thickness for takeover be determined?

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The nozzles of pressure vessels are subjected not only to internal and external pressures but also to loads from external connections, and they must also meet certain stiffness requirements. Therefore, many standards and specifications set requirements for the minimum wall thickness of pipes. According to ASME VIII-1 UG-45: For inlets, outlets, or inspection holes, such fittings do not experience any end loads; their minimum wall thickness is specified in the diagram. For fittings other than inlets, outlets, or inspection holes, these fittings are subject not only to internal or external pressures but also to end loads, and they must also meet certain stiffness requirements; their minimum wall thickness is indicated in the diagram. UG-45 mentions that, in addition to considering internal and external pressures, end loads must also be taken into account, but no specific values are given in UG-45. The main reason is that the design of pressure vessels and piping is carried out simultaneously; at the initial stage, the manufacturer does not have information on the load conditions at the pipe ends, and under such conditions it is impossible to accurately calculate the impact of these loads on the wall thickness of the pipes. However, many engineering companies have their own experience values, that is, they specify a minimum thickness for the transition wall to account for the effect of the nozzle load on the pipe. The domestic standard GB/T 150-2011 does not specify any requirements regarding the minimum wall thickness of pipes. However, HG/T 20581-2020 has such requirements.