How should the heat exchange tubes of a heat exchanger be repaired?

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Leakage points: In pressure vessels, leaks in the heat exchange tubes generally occur in two places – at the joints of the tubes and within the tubes themselves. Treatment of leaks at pipe joints. There are mainly three methods for connecting pipes to tube sheets: expansion bonding, welding, and a combination of welding and expansion bonding. Due to fluctuations in temperature and pressure, as well as uneven thermal deformation, expansion joints can cause the tubes to pull away from the tube sheet and become loose, resulting in leaks. The leak can be resolved by performing additional expansion operations; if this does not work, the process can be repeated. However, more than three such expansions should not be carried out, as this will cause cold hardening of the material at the tube sheet holes, preventing proper tightening. If inflation does not work, the pipe needs to be replaced or welding should be used. It should be noted that after welding, the surrounding tubes need to be expanded again, as thermal expansion and contraction of the tube sheet after welding can cause leaks at the expansion joints of the other tubes around it. If the weld between the tube and the tube sheet is leaking, it can be repaired by grinding and re-welding. Treatment of tube leakage: Heat exchange tubes often develop cracks and perforations due to corrosion, abrasion, erosion, deposition corrosion, and other factors, which leads to leakage. Leaks in the pipes themselves are generally unreparable. If there are not many pipes that are leaking, the ends of those pipes can be sealed using conical metal plugs; if the pressure in the pipes is high, it is more reliable to seal them first and then weld them in place. The length of the metal plug is generally twice the inner diameter of the pipe; the diameter at the smaller end should be 85% of the inner diameter, with a taper of 1:10. The hardness of the plug material should be lower than or equal to that of the pipe. When using plug pipes to eliminate leaks, the number of plug pipes shall not exceed 10%. When one end of a stainless steel heat exchange tube is damaged, the tube drawing repair method can also be used. This is because the elongation rate of stainless steel tubes is 40%~45%, and the tube can be drawn multiple times as long as the total elongation does not exceed 12%.