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How to identify excessive expansion of heat exchange tubes: As an important device in industrial production, the quality of the expansion joining of the heat exchange tubes in a heater directly affects the device’s performance and service life. Over-expansion is a common quality defect during the installation of heat exchange tubes, and it requires accurate assessment from multiple perspectives. Tube sheet deformation detection method: After thoroughly cleaning the surface of the tube sheet, high-precision measuring tools (such as straight edges, dial indicators, etc.) are used to check the surface flatness. When local bulging, depression, or warping of the tube sheet is detected, especially in the area near the expansion joints of the heat exchange tubes, this is often a clear sign of over-expansion. Visual inspection of the heat exchange tubes: Carefully examine the condition of the tube wall at the expansion joints. If defects such as thinning of the tube wall, wrinkling, or visible cracks are found, it can generally be determined that there is an issue with excessive expansion. These damages usually result from the force applied during crimping exceeding the tube’s tolerance limit. Application of professional testing methods: Sealing performance testing is carried out using specialized equipment such as halogen leak detectors or helium mass spectrometer leak detectors to assess the sealing quality of flanges. When a medium leak is detected, in addition to loose expansion joints, material damage caused by excessive expansion is also an important factor. Dimension measurement comparison: The dimensions of the butt-welded area of the heat exchange tubes are measured before and after butt welding; if the measured values exceed the upper limit of the allowable range, it can be determined that there is over-butting. Measure simultaneously the gap between the tube sheet holes and the heat exchange tubes; if a negative gap occurs (the outer diameter of the heat exchange tubes is greater than the inner diameter of the tube sheet holes) and this value exceeds the design limits, it is also clear evidence of over-expansion. In-depth material analysis; hydraulic testing for verification – Hydraulic testing is carried out in accordance with standard requirements to check for leaks at the flanged areas. Leakage at the expanded joint can be caused not only by quality issues with the expansion process, but also damage to the joint resulting from excessive expansion. Microstructure inspection: The metallographic structure of the expansion joint area is observed through metallographic section analysis. If signs of excessive plastic deformation such as grain deformation, sliding, or twinning are observed, or if microcracks are present, it indicates that the heat exchange tube was subjected to excessive stress during the expansion joining process. Hardness change testing: Equipment such as a Rockwell hardness tester is used to measure the hardness of the expansion joint area. Excessive swelling can cause work hardening of the material; if test results show a hardness significantly higher than the material’s original value and beyond the normal range of variation, this can be used as an indicator of excessive swelling. How to scientifically control the expansion force: Process parameter optimization. During mechanical expansion, it is necessary to select the parameters of the expansion rod (diameter, taper, length, etc.) appropriately based on the pipe diameter and material properties. When the pipe diameter is large or the material is hard, the expansion rod parameters should be increased appropriately, but a reasonable range must be determined based on experimental data. Hydraulic expansion jointing requires precise setting of pressure and holding time. Equipment and tool selection: High-precision expansion joining equipment is used to ensure that pressure control accuracy is at the lowest possible level, while stroke control accuracy is on the millimeter scale. Regularly calibrate and maintain the equipment to ensure the performance of key components. At the same time, select appropriate expansion tools based on the characteristics of the piping, and inspect and replace them regularly. Material quality control: Thoroughly inspect the material properties of pipes and tube sheets before expansion welding to ensure they meet the design requirements. Special attention should be paid to ensuring that the hardness of the pipe is slightly lower than that of the tube sheet, as this helps to control expansion force and ensure the strength of the expansion joint. Operator training: Strengthen the professional skill training of operators to ensure they have a thorough grasp of the expansion joining process and equipment operation. At the same time, strengthen quality awareness education to ensure strict adherence to operating procedures and proper documentation of the process. Through the detection methods of the above system and scientific control measures, the problem of excessive expansion of heat exchange tubes can be effectively avoided, ensuring the manufacturing quality and performance of the heat exchanger.