Problems with two-phase steel tubes in tubular heat exchangers
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I would like to ask the experts: for bipolar steel heat exchange tube bundles, is it necessary to use seamless tubes, or can bipolar steel welded tubes be used instead? What are the reasons if welded pipes cannot be used?
Where there are welds, welding defects are inevitable. The main reason for choosing duplex stainless steel is its corrosion resistance. The cost of this material is quite high, and it would be a shame if it corroded at the weld areas. In any case, large design firms avoid using welded pipes in their designs; some smaller design firms and manufacturers use welded pipes in order to save costs
Dual-phase steel pipe replacement – it’s the first time I’ve heard this term; I know so little!
Just like ordinary stainless steel, people* usually prefer seamless pipes; actually, welded pipes can be used in some situations, but customers are reluctant to use them
The pressure-bearing capacity of welded pipes is inferior to that of seamless pipes, which is the main difference between the two. Duplex stainless steel refers to a type of material whose main function is corrosion resistance. It doesn’t seem quite right for the original poster to substitute in this way.
Heat exchange tubes should be made of seamless steel pipes, right? If they are welded, then non-destructive testing must be performed on each one. What about tubes with a larger diameter or more tubes in total? How is that handled? How to do it? The cost is far higher than that of using seamless steel pipes
I don’t understand why non-destructive testing is necessary Is a 100% X-ray inspection required? Can eddy current testing be used? 6# sunrisehao
The standards mentioned in 4.4.1 of GB151 4.4 for heat exchange tubes all belong to the seamless steel tube series； 4.4.2 specifies the scope of application for austenitic stainless steel welded pipes that meet the requirements of Appendix C. Dual-phase steel is chosen also for corrosion resistance reasons; as for whether welded pipes can be used, it depends on the design requirements. If stainless steel welded pipes are to be used, eddy current testing must be carried out on each pipe in accordance with GB/T12771, as specified in Appendix C1.8.