Sealed welding refers to the welding that guarantees the sealing performance of the heat exchange tube and the tube sheet. Seal welding effectively seals the connection between the heat exchange tube and the tube sheet, and strengthens the weld penetration with appropriate welding methods and welding process parameters to achieve a certain weld strength.
When the heat exchange tube and the tube sheet are welded, the processing is simple, the manufacturing process is simple, the sealing is good, and the welding, visual inspection and maintenance are very convenient, and the current shell-and-tube heat exchanger is convenient. The medium heat exchange tube and the tube sheet are the most widely used one.
When the welded joint is used, there is a strength weld which ensures the sealing property and the tensile strength of the welded joint, and a seal weld which only ensures the sealing property of the heat exchange tube and the tube sheet. There is a limit to the performance of the strength weld, which is only suitable for applications with less vibration and no crevice corrosion.
When welding is used, the distance between the heat exchange tubes should not be too close. Otherwise, the quality of the welds is not easily ensured by heat, and the pipe ends should be kept at a certain distance to reduce the welding stress between them. The length of the heat transfer tube extending from the tube sheet must meet the specified requirements to ensure its effective bearing capacity.
In the welding method, according to the material of the heat exchange tube and the tube sheet, welding by arc welding, TIG welding, CO2 welding or the like may be employed. For heat exchangers with high requirements for connection between heat exchange tubes and tube sheets, TIG welding should be used for heat exchangers and thin tube sheet heat exchangers with large design pressure, high design temperature, large temperature variation, and alternating load.