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Composite/multi-layer containers: The mandatory requirements for composite/multi-layer containers are as follows: 01 The assembled cylinder must undergo stress-relief heat treatment, and this process may be carried out simultaneously with post-welding heat treatment. 02 For multi-layer integral wrapping containers and containers with steel strips wound around the inner cylinder, welding test pieces of the products shall be prepared; welding test pieces shall also be prepared for both the inner cylinder of multi-layer section wrapping containers and the layer plates. 03 For longitudinal Class C joints of the laminate sheets in multi-layer wrapped containers, with a minimum tensile strength standard value of Rm≥540 MPa, 100% magnetic particle or penetrant testing shall be carried out on the surface. 04 Incorrect winding of steel straps around the inner cylinder – Type A and Type B joints; multiple layers of straps are used to wrap the Type A joints on the inner cylinder, while multiple layers are used as a whole to wrap the Type A and Type B joints on the inner cylinder ； Joints between laminated plates, Class A joints for fitting the cylinders of each layer of the container, and welding joints between each layer of laminated plates and the end flanges or spherical heads ； The longitudinal and circumferential joints of the outermost layer of laminates shall be subject to full radiographic or ultrasonic testing. 05. When an explosive bonding plate is used for the tube sheet, it shall meet the requirements of grade B1; when the heat exchange tubes are subjected to circumferential compressive stress, a cladded tube sheet is preferred. 06 Lined composite structures shall not be used in the following situations: (1) design temperature > 300°C; (2) vacuum vessels; (3) media with extreme or high hazards. 07 The strength expansion of composite tube sheets should be achieved by creating grooves in the lining. 08 When a composite tube sheet is used, the tube sheet shall be joined by expansion welding. 09 When welding the composite tube sheet to the heat exchange tubes, the thickness of the clad layer should not be less than 3mm ； When performing strong expansion jointing with the heat exchange tubes, the thickness of the cladding layer should not be less than 10 mm. 10 The surfaces to be surfaced-welded on the tube sheet and tube box flat covers, as well as the surfaces after the surfacing weld layer has been applied, shall undergo surface inspection.