Heat exchange tube and tube plate welding problems
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When using the connection method of strength expansion and sealing welding, are there any requirements on the sequence? Should the strength be expanded first and then seal welded, or seal welded first and then strength expanded? What are the advantages and disadvantages of each of the two methods, and how does your company implement them in actual production? Welcome to discuss! ( * * extra points: )).
It should be more appropriate to weld first and then expand. If welding is done first and then expanded, lubricating oil must be used when using a pipe expander to expand the pipes. The oil stains left on the tube plate after expansion are difficult to completely clean. In subsequent welding, the gas generated by these oil stains at high welding temperatures will affect the quality of the weld. Therefore, using welding first and then expansion will eliminate the above phenomenon. However, welding first and then expanding may cause cracks in the weld in the subsequent expansion, so the expansion joint should be some distance away from the weld. Therefore, in the tube sheet structure where expansion welding is used together, the annular groove in the tube hole should be opened 15mm away from the upper surface of the tube sheet.
If it is highly swollen, how should it be constructed if it is required to be fully swollen?
It is recommended not to use mechanical expansion for heat exchangers that are welded first and then expanded. If the baffle spacing is relatively large after mechanical expansion, the tubes will bend. Use hydraulic expansion as much as possible, and the expansion joint quality will be better.
We all expand first and then weld. The main problem is to remove the oil, but I personally think it is more convenient than expanding after welding. At least the welding quality can be guaranteed!
Our company welds first and then expands to avoid the appearance of pores.
Welding first and then expansion or expansion first and then welding. For the welding part, there are two types of difference: seal welding and strength welding.； For the expansion joint, there are differences between strength expansion and sticking expansion. For example, in a structure that combines expansion joints and sealing welding, the expansion joint bears the force, while the sealing welding ensures sealing. The height of the sealing weld is generally 1-2mm, which will not affect the strength of the expansion joint, but the oil at the joint must be cleaned during welding. The structure that combines strength welding with expansion joints (expansion joints) uses the welding to bear the force, and the purpose of expansion joints is only to eliminate the gap between the pipe and the tube sheet to prevent the gap from being eroded by corrosive media. Post-weld expansion and sticking expansion: Post-weld expansion and sticking expansion: Post-weld expansion joints and pasting expansion are generally used on heat exchange equipment with high pressure. The welding part is a reinforced sealing weld. The welding waist height is 2.8mm. The expansion joint bears the force. When the expansion joint fails, the reinforced sealing weld can bear the force. The expansion part is used to eliminate crevice corrosion. Under what conditions should welding first and then expansion or first expansion and then welding be used for expansion welding structures? There is no unified regulation at present, but it generally tends to be better to weld first and then expand. At present, due to the different processing techniques and equipment conditions of each manufacturing plant, all * Get used to our factory’s manufacturing methods!
Our approach is also to weld first and then expand!