A full-process solution to the leakage problem of heat exchange tubes in pressure vessels

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The leakage sites can be accurately identified during the operation of pressure vessels. Leaks in the heat exchange tubes mainly occur at two key locations: the tube sheet connections and the tube bodies themselves. According to industry statistics, about 65% of leakage incidents are caused by failures at the connection points, while the remaining 35% are directly related to pipe corrosion. Solutions for leaks at tube sheet connections – Handling failures in the expansion joint process: When it is detected that the tube body becomes loose due to temperature fluctuations or pressure changes at the expansion joint location, it is recommended to adopt a step-by-step approach. The first re-expansion operation should be carried out within 24 hours after shutdown; a second re-expansion should be performed at least 72 hours later. For more than three re-expansion attempts, it is necessary to test the hardness of the tube holes. Key points of welding repair techniques: In cases where re-expansion is ineffective or there are leaks at the welded areas, the TIG remelting process should be used for repair. After repair, preventive expansion joining should be carried out on the three adjacent rows of tubes. The welding parameters should be 10–15% lower than those specified in the original welding standards. Solutions for leaks in the tube body itself – Emergency sealing techniques: When the tube body develops perforations or cracks, it is recommended to use conical alloy plugs. The hardness of the plug material should be ≤ HRB80 according to the Rockwell scale, and the taper should be strictly controlled within a tolerance range of 1:10. After installation, the plug must be sealed using TIG welding. Repair techniques for special materials: For austenitic stainless steel tubes, a stepwise stretching method should be employed (with each stretch being ≤3%). After repair, intergranular corrosion tests should be conducted. Laser cladding technology is recommended for surface strengthening. Key indicators for maintenance management: Maintenance tasks, technical standards, and inspection frequencies: Tightness of expansion joints – GB151-2014; quarterly inspections. Weld penetration – ASME standards; annual evaluations. Wall thickness – tolerance of ±0.2 mm; semi-annual inspections. Precautions in practical applications: The proportion of blocked tubes should be kept within 10% of the total number of heat exchange units. During winter maintenance, attention must be paid to changes in the material’s cold brittleness. Stress simulation calculations should be conducted in advance for composite repair methods. When dealing with high-temperature media, thermal expansion compensation factors must be taken into account. Through systematic maintenance strategies and precise repair techniques, the service life of heat exchange equipment can be extended by more than 30%. It is recommended to establish digital operation and maintenance records to achieve full-life-cycle management.