For alkali stress corrosion cracking, which part needs heat treatment?
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This post was last edited by Aoki_EXZM on 2024-4-24 at 14:26. I’ve recently been dealing with the issue of alkali stress corrosion. A caustic solution tank was built, and the equipment specifications are shown in the image below: https://bbs.hcbbs.com/forum.php?mod=image&aid=3557001&size=300x300&key=e8f8765453fc73dd&nocache=yes&type=fixnone The temperature and NaOH concentration are located at the edges of areas A and B; this equipment underwent overall heat treatment at the end. When checking the standards, some minor issues were found: the temperature and NaOH concentration are in Zone A. When the equipment is equipped with heating pipelines, which parts exactly need to be heat-treated? https://bbs.hcbbs.com/forum.php?mod=image&aid=3556998&size=300x300&key=ec7df9e9373606cb&nocache=yes&type=fixnone The text indicates that it is necessary to handle the pipeline. https://bbs.hcbbs.com/forum.php?mod=image&aid=3557000&size=300x300&key=b195b6d9f3c6ef5b&nocache=yes&type=fixnone The section explaining the revisions suggests that it is necessary to deal with the equipment. Everyone, take a look
When dealing with the issue of alkali stress corrosion cracking, special attention is usually required for those parts that are exposed to high temperatures and alkaline environments such as NaOH, especially when these conditions are near or within the material’s brittle critical region (such as Zone A you mentioned). If the device has undergone overall heat treatment, it is usually to reduce the stresses introduced during manufacturing or previous use, and at the same time improve the microstructure of the material, thereby enhancing its resistance to stress corrosion. Based on your description, if the temperature and NaOH concentration are in Zone A, and there are heat tracing pipelines, these areas are likely to be the ones that require the most attention. Heated pipelines may be more susceptible to alkaline solutions due to local temperature increases, thereby increasing the risk of stress corrosion cracking. Therefore, it is crucial to carry out focused heat treatment on these parts or check for any unresolved stress. In terms of specific procedures, the following points can be considered: 1. **Check the heat treatment process**: Verify that the overall heat treatment covers all critical areas, especially the heat tracing pipelines. 2. **Stress testing**: Conduct stress testing to check whether the stress in all components has been reduced to safe levels. 3. **Material inspection**: Check whether the materials used have sufficient resistance to alkaline environments; if necessary, consider replacing them with more durable corrosion-resistant materials. 4. **Regular maintenance and inspection**: Establish a schedule for regular checks, with more frequent inspections in high-risk areas. Finally, it is recommended to consult engineers or experts with relevant experience in order to obtain more specific and targeted advice and solutions. .
Heat treatment should be applied to the welds of the heat tracing pipelines as well as those in the areas affected by them
The maximum operating temperature has reached 80°C; the housing must undergo heat treatment； Heat-traced pipelines have higher temperatures and also require heat treatment.