Brittle failure may occur in the pressure vessel at low temperature. Before brittle failure, the structure of the vessel does 
not appear or only local plastic deformation, and the vast majority of the vessel does not appear overall yield. The low 
temperature brittle fracture cracks are generally caused by material defects, manufacturing defects, geometric shape 
mutations in the design structure or other stress concentrations. 
The following aspects should be considered in the design of cryogenic vessels : 
1, the structure should be as simple as possible, welding parts to reduce the degree of restraint. 
2, each part of the structure section should avoid excessive temperature gradient. 
3. Try to avoid the sudden change of structure shape and the sharp change of stiffness to reduce the local stress concentration. 
4, the various parts of the container components formed by the fillet weld, nozzle and the connection of the shell weld, should 
be at the corner of the grinding into a smooth transition, and the nozzle and flange internal end grinding into a rounded corner. 
5.When the various supports of the container are connected to the container, a padding plate or a reinforcing plate is required 
to avoid direct welding with the container shell. The material of backing plate or reinforcing plate is the same as that of container shell. 
6. Nozzle reinforcement should be as much as possible the use of overall reinforcement or thick-walled tube reinforcement, 
when the specification allows the use of reinforcing ring reinforcement, should be fully welded structure, and weld smooth transition. 
7, container and non-pressure components or accessories connection weld should not be discontinuous welding, should be continuous welding