Anti-hydrogen steel U-tube bundle
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Anti-hydrogen steel U-tube bundles: I would appreciate it if experts could advise me on any special requirements regarding the materials (forgings and heat exchange tubes). Are heat treatments required for the tube ends and U-tubes? Are there any other things to keep in mind? Thank you
Generally, heat treatment is necessary after the heat exchange tubes are bent into shape. Each one also needs to undergo a hydrostatic test. Since hydrogen-resistant steel tends to develop cracks, the joints formed by welding the heat exchange tubes to the tube sheet require stress-relief heat treatment. However, such joints are prone to defects such as cracks after heat treatment. In such cases, it is possible to weld a layer of stainless steel on the tube sheet; this helps to address the difficulties associated with the welding process and also prevents the formation of large cracks during heat treatment after welding. Personal opinion, for reference only.
Thank you. I found a design from outside, used it as a reference, and carried out heat treatment on the U-shaped tube bend sections as well as hardness testing of the welds at the tube ends
After bending, heat treatment and hydrostatic testing are generally required, and a PT inspection is also needed for the bent section as well as the 150mm straight section.
CRMO alloy tubes are used in the synthesis of ammonia from urea; welding such heat exchangers is rather complicated, and the welding process is not straightforward, which makes cracks prone to occur at the welded areas during use.
For hydrogen-resistant alloy tubes, the first test is essential; after the second bending, heat treatment procedures need to be considered depending on the radius of bending, and testing is also necessary in the end.