With the advancement of welding technology, most of the titanium heat exchanger tube bundles used in petrochemical industries are connected by welding or expansion welding. The leakage of the welding seam connecting the tube and the tube sheet is a difficult point in the treatment of the leakage of the tube bundle. It is not a good method to use repair welding, because there is a gap between the heat exchanger tube and the tube sheet hole, and impurities will inevitably enter during use, which will cause strong bubbles, slag inclusions, and interlayers during welding. , The stress concentration caused by local welding may crack the nozzle near the repair welding point, resulting in a new leakage point.
Therefore, for the strength welding to connect the titanium heat exchanger tube bundle, the method to prevent the failure of the welding joint:
The first is the reasonable selection of materials, that is, the reasonable selection of tube sheets and heat exchange tubes according to the medium, to prevent electrochemical corrosion between the tube sheets and the tubes. Second, the root of the weld should be fully welded, with a high enough reinforcement height (≥2.5mm). Third, the production practice shows that the strength expansion after welding is a method to ensure that the welding joint of the heat exchanger does not fail.
For pure-strength expansion tubes, if the expansion port leaks, the expansion can be carried out after the pressure is released, and the number of expansion should not be more than three times.
