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Welded joints: The regulations regarding welded joints are as follows: 01 Welded joints of no fully penetrated pipe fittings shall not be used in situations with steep temperature gradients. 02 For containers with a welding joint coefficient of φ=1.0, there shall be no undercutting on the weld surface. 03 For containers with a weld joint coefficient of φ=1.0, Class A and Class B weld joints shall undergo 100% non-destructive testing (RT/UT/TOFD). 04 The longitudinal joints of the layer plates in multi-layer wrapped containers are of Class C. 05 The splicing joints of the sphere tank struts shall be fully welded through. 06 The welds between the shell and the nozzles shall adopt a fully penetrative structure. 07 The welds between the skirt shell and the housing shall be of full penetration type. Welded test pieces: The regulations regarding welded test pieces are as follows: 01 Pressure vessels for which welded test pieces of the product are to be prepared: (1) Low-temperature vessels made of carbon steel or low-alloy steel; (2) Pressure vessels made of low-alloy steel with a minimum specified tensile strength of more than 540 MPa; (3) Pressure vessels used to contain extremely hazardous or highly hazardous media. 02 For pressure vessels that require heat treatment, the welded test pieces of the product must be heat-treated together with the pressure vessels themselves. 03 For containers in which the material properties are improved or restored through heat treatment during the manufacturing process, in the case of longitudinal welded joints of Category A (excluding Category A joints where a ball seal is connected to a cylinder), welding test pieces must be prepared for each individual product. 04 For end caps that are first assembled from panels and then shaped, if heat-treated specimens are required, welding specimens should be prepared first, with the heat-treated specimens being taken from these welding specimens.