Connecting process of welded heat exchange tube and tube plate on heat exchanger of nuclear power plant with expanding rather than welding

Abstract

The invention discloses a connection process of welded heat exchange tubes and tube plates on heat exchangers in nuclear power plants, which only expands but not welds. Initial positioning of the heat pipe and the tube plate hole; apply low pressure to the welded heat exchange tube, adjust the roundness of the welded heat exchange tube; continue for a period of time until the welded heat exchange tube undergoes plastic deformation, and then remove the low pressure applied to the welded heat exchange tube; Apply high pressure to the welded heat exchange tube to compress the welded heat exchange tube and the tube sheet. By applying low pressure to the welded heat exchange tube, the welded heat exchange tube expands uniformly in the circumferential direction and produces plastic deformation, eliminates the roundness deviation on the welded heat exchange tube, reduces the influence of weld reinforcement, and makes the welded heat exchange tube The heat exchange tube has a better sealing effect with the tube plate hole in the subsequent high-pressure expansion process, and effectively realizes the sealed connection between the welded heat exchange tube and the tube plate hole without slotting the tube plate hole. The invention is applied in the technical field of expansion joints.

Description

technical field [0001] The invention relates to the technical field of expansion joints, in particular to a connection process of welded heat exchange tubes and tube plates on heat exchangers in nuclear power plants that are only expanded but not welded. Background technique [0002] In the manufacturing process of heat exchangers in nuclear power plants, a large number of welded heat exchange tubes are used, and the welded heat exchange tubes need to be sealed and connected to the tube sheet. In the prior art, due to the roundness deviation of the welded heat exchange tube, weld reinforcement and uneven strength have a great influence on the sealing performance of the expansion joint, in order to avoid leakage of the joint between the welded heat exchange tube and the tube sheet, ensure that the equipment In order to ensure the safety, the connection method of sealing welding + strength expansion or strength welding is usually adopted, and the sealing of the joint is realiz...

AI Technical Summary

Problems solved by technology

In the prior art, due to the roundness deviation of the welded heat exchange tube, weld reinforcement and uneven strength have a great influence on the sealing performance of the expansion joint, in order to avoid leakage of the joint between the welded heat exchange tube and the tube sheet, ensure that the equipment In order to ensure the safety, the connection method of sealing welding + strength expansion or strength welding is usually adopted, and the sealing of the joint is realized by welding the welded heat exchange tube and the tube sheet. However, due to the complicated process and the need for sealing welding process, it is often necessary to Tube plate cladding and heat treatment greatly increase the manufacturing cycle and cost

In addition, there is a certain probability of defects in the surfacing welding and sealing welding of the tube sheet, which will lead to joint leakage

Moreover, tiny defects are difficult to be found directly, which also increases the cost of non-destructive testing

In addition, it is more difficult to repair the seal welding

[0003] The existing expansion-not-welding connection technology used in heat exchangers in other industries requires the processing of annular stress grooves in the tube sheet. On the one hand, it introduces the cycle and cost of annular groove processing; After the expansion of the heat exchange tube, the residual stress in the grooved area is very large, which will accelerate the stress corrosion of this part of the heat exchange tube, and the liquid is easy to remain in the annular groove, which will also accelerate the corrosion of the tube sheet

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