Based on the dimensions of high-temperature steam pipe and branch pipe

the temperature casing is taken as an example to establish the model

and the stress and vibration modes at weld toe of the temperature casing with three different structures and materials

namely

the through-hole casing

the step casing and the structure optimized temperature casing

are analyzed. The results show that

the internal overall stress level of weld toe of the throughhole casing and the step casing is similar

which is higher than that in the structure optimized temperature casing. The risk of fatigue fracture of the structure optimized temperature casing is greatly reduced. The maximum stress of weld toes of the three structures is distributed at the highest point of the circumference of the steam main pipe(main pipe)

where the crack is most likely to initiate

and the stress level is symmetrically distributed based on this point. The structure optimized temperature casing has a low response degree to the vibration of the main pipe. Therefore

optimization of the structure and material of the branch pipe can reduce the weld vibration induced by the parent pipe vibration.