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Hydraulic expansion machine is a special hydraulic expansion equipment used for the expansion and connection of tubes and tube sheets in the manufacturing of equipment such as heat exchangers, condensers, and high-pressure heaters. The use of hydraulic expansion technology has the advantages of low manufacturing cost, light labor intensity, short manufacturing cycle, uniform and reliable expansion quality, etc. Hydraulic expansion technology has been widely used in the manufacture of heat exchangers in the fields of petrochemicals, electric power, boilers, nuclear power, refrigeration, etc., greatly improving the quality and production efficiency of domestic heat exchanger equipment.

Development background

The connection between heat exchange tubes and tube sheets mainly includes expansion, welding and expansion welding, and the expansion method can be divided into mechanical expansion, hydraulic expansion, rubber expansion and explosive expansion. Domestic enterprises generally adopt mechanical expansion, which has high labor intensity and low work efficiency. When the heat exchanger with a tube sheet exceeding 100mm cannot achieve full thickness expansion, and the actual expansion rate, pull-off force and sealing pressure are not directly related, the operator mainly determines the expansion tightness based on experience, and the expansion quality is greatly affected by human factors. In addition, the lubricating medium used in expansion will penetrate into the gap between the tube and the tube sheet, which will have an adverse effect on the subsequent welding quality.

In response to the above problems, Krips et al. developed hydraulic expansion 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 sets an O-ring at each end of the mandrel to seal the expansion medium. The expansion pressure is directly applied to the surface of the heat exchange tube through the center hole of the mandrel, causing the heat exchange tube to undergo plastic deformation and connect with the tube sheet. The method developed by Krips et al. belongs to the O-ring method. Due to the poor dimensional accuracy of domestic heat exchange tubes, the wall thickness deviation of the tube can reach ±10%. Foreign O-ring expansion technology cannot expand domestic heat exchange tubes, and the cost of importing high-precision heat exchange tubes from abroad is too high, which limits the promotion of this technology in China. Liquid bag hydraulic expansion technology uses elastic hydraulic bags to isolate the expansion medium from the heat exchange tube. The expansion pressure acts on the inner wall of the heat exchange tube through the liquid bag, avoiding the contamination of the tube mouth by the O-ring expansion technology during the expansion process.

The domestic liquid bag hydraulic expansion technology aims at the deficiency of large dimensional deviation of domestic heat exchange tubes. It absorbs foreign technology and continuously innovates to develop a new generation of hydraulic tube expanders suitable for my country's national conditions. It has been widely used in the manufacture of heat exchangers in petrochemical, electric power, boiler, nuclear power, refrigeration and other fields.