The connection between the heat exchange tube and the tubesheet mainly includes expansion joints, welded expansion joints and combined expansion joints, and the methods of expansion joints can be divided into mechanical expansion joints, hydraulic expansion joints, rubber expansion joints and explosive expansion joints. Domestic enterprises generally adopt mechanical expansion joint method, which is labor intensive and inefficient. When the tube sheet exceeds 100mm, the heat exchanger cannot realize the full-thickness expansion joint, and the actual expansion rate, pull-off force and sealing pressure are not directly related. The operator mainly determines the tightness of the expansion joint according to experience, and the quality of the expansion joint is greatly influenced by human factors. Moreover, the lubricating medium used in the expansion joint will penetrate into the gap between the pipe and the tubesheet, which will adversely affect the subsequent welding quality.

In view of the above problems, Krips et al. developed the hydraulic expansion joint technology in the late 1970s. This technology has formed two differences, one is the O-ring method, and the other is the liquid bag expansion technology. The O-ring method is to set two O-rings at both ends of the mandrel to seal the tube expanding medium, and directly apply the expanding pressure to the surface of the heat exchange tube through the central hole of the mandrel, so that the heat exchange tube is plastically deformed and connected with the tubesheet. Krips et al. developed an O-ring method. Due to the poor dimensional accuracy of domestic heat exchange tubes, the deviation of tube wall thickness can reach 65438 00%. Foreign O-ring expansion joint technology can not expand domestic heat exchange tubes, and the high cost of importing foreign high-precision heat exchange tubes limits the popularization of this technology in China. Liquid bag hydraulic expansion joint technology uses elastic hydraulic bag to isolate the expansion medium from the heat exchange tube, and the expansion pressure acts on the inner wall of the heat exchange tube through the liquid bag, thus avoiding the pollution of O-ring expansion joint technology to the nozzle in the expansion joint process.

In order to solve the problem of large size deviation of domestic heat exchange tubes, domestic liquid bag hydraulic expansion technology absorbs foreign technology and continuously innovates and develops a new generation of hydraulic tube expander suitable for China's national conditions, which has been widely used in heat exchanger manufacturing in petrochemical, electric power, boiler, nuclear power, refrigeration and other fields. Foreign hydraulic tube expander: rubber sleeve type.

Country of production: Italy, Japan, etc.

Its working principle is as shown on the right:

Evaluation of Japanese rubber sleeve hydraulic expander;

Advantages: more tests, high pressure and relatively high cost;

Disadvantages: long manufacturing cycle, troublesome use, long assembly time and low production efficiency.

Domestic hydraulic tube expander: liquid bag type.

Main production address: Changzhou

The main components are: metal mandrel and high-strength fluororubber elastomer (as shown on the right).

Characteristics of hydraulic bag hydraulic tube expander:

Advantages: short manufacturing cycle, simple assembly, high production efficiency and low cost;

Disadvantages: heavy and inconvenient to transport. Model -SHQY-300-A rated expansion pressure Mpa300 maximum test pressure Mpa350 expansion speed times/,mim5- 10 expansion medium-pure water high-pressure pipeline, pressure explosion pressure Mpa280/700 minimum expansion aperture mm greater than 10 equipment weight Kg95 input power supply V220 to drive Kg compressed air, and ≥3 control system (.