Can the four-fold simulated heat treatment of pressure vessels be carried out within a single cycle?
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A Cr-Mo steel vessel requires four times the amount of simulated post-weld heat treatment as specified by the technical requirements. The manufacturer proposes that this can be achieved through a single heat treatment cycle, with the holding time being four times that of the normal heat treatment. I also agree with this approach, but the owner insists that the process of heating, maintaining temperature, and cooling needs to be repeated 4 times each time. I would like to ask experienced sea travelers whether it is necessary to repeat this procedure 4 times; thank you all.
Below is a clause from GB/T 30583-2014 \"Code for Post-Weld Heat Treatment of Pressure Equipment\"; see if it is helpful to you:
Thanks for the discussion from SDHZZM. A similar description is also available in ASME IX. In principle, simulated post-weld heat treatment is intended to prevent a decline in the material’s properties due to excessive heat treatment time; once the required holding time is achieved, the goal is met.
It is not necessary; the effect of heat treatment on Cr-Mo steel can be roughly determined by calculating the LMP based on the accumulation of heat treatment cycles at temperatures above 480°C. This is the basic principle, and GB/T 30583-2014 should establish regulations for all steel grades in accordance with this principle.
In general, it is possible, but if the owner or the design requirements specify it per cycle, then one must follow those requirements. Especially regarding design requirements, the client can sometimes interpret them according to standards; it was acceptable to do so in the past, but if such an interpretation is not possible, compliance with the requirements is still necessary. There’s nothing you can do; in many cases, personal judgment takes precedence over standards, and even stricter than those standards. You can’t say that they’re wrong.