For fixed-tube-sheet heat exchangers that require post-weld heat treatment, the feasibility of leaving one end of the tube end unwelded before the heat treatment and welding it afterward
Thread Content
For shell-side welding in fixed-tube-sheet heat exchangers, heat treatment is required after welding. When considering overall heat treatment, different materials have varying coefficients of thermal expansion, which can affect the quality of the joints between the heat exchange tubes and the tube sheet. Local heat treatment, on the other hand, is relatively more time-consuming and energy-intensive. Currently, the approach being considered is to leave one end of the tube open before heat treatment, to weld it after heat treatment, and then only perform local heat treatment on that end. As for the feasibility of this approach…
It is possible to do this; there are advantages and disadvantages to it, and the uniformity of local heat treatment is not as good as that achieved in a furnace
Well-thought out, good perspective, learned a lot
One tube sheet is equivalent to two heat treatment processes, plus multiple welding heating cycles; how can one determine whether the material properties have degraded?
The tube sheet itself is a forged piece, supplied in the normalized or normalized+tempered condition. This approach involves performing stress-relief heat treatment on one side of the tube sheet only; stress relief reduces the tensile strength of the material, but multiple stress-relief treatments are sufficient to ensure that the required strength levels for equipment design are met. Unless the tensile strength of the materials used itself is at the lower limit specified by the material standards, the commonly used materials generally maintain their properties within the standard range even after multiple heat treatments.
In such cases, our previous approach was to add a simulated test piece, so as to provide a factual basis for this equipment
The heat treatment of heat exchangers has always been a problematic issue, especially when special media are involved and heat treatment is required
The owner’s solution simply involves performing an additional local stress-relief heat treatment on one side of the tube sheet at the joint where the pipe is welded to it. For the heat treatment of fixed-tube-sheet heat exchangers, this should be a relatively reliable and reasonable heat treatment approach.