Microcracks.
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This post was last edited by WANGJIABAO on 2016-2-29 at 14:11. I have a gentle question: during the regular inspection of pressure vessels, if there is a tendency for stress corrosion in such equipment and microscopic cracks are detected through metallographic testing, how should this defect be handled in accordance with the regulations for regular inspection of pressure vessels?
Can regular product inspections also include metallographic analysis? How do I take it off? The discovery of cracks is not allowed at any time. It should be repaired.
Isn’t this a regular inspection for pressure vessels? Regular inspections mean conducting tests on the products. . Product inspection: How do you take samples of materials or welds for metallographic analysis?
In-situ metallography: no need to cut test pieces; it can be performed directly at the location.
Metallographic inspection examines the changes in the internal structure of the material; if there are microscopic cracks, it is no longer a matter of repair but rather replacement.
1. Probe to locate all cracks； 2. Add hardness testing to determine whether the hardness exceeds the specified limit ； 3. Grind to remove cracks; determine whether welding repair is needed based on the grinding depth ； 4. Stress corrosion requires three essential conditions (a sensitive alloy, a specific environment, and tensile stress); it is necessary to analyze these conditions carefully and find ways to eliminate or improve one of them as much as possible ； 5. Determine whether it can be used again based on the repair status ； 6. Shorten the inspection cycle, reduce the safety status level, or scrap it directly. In fact, each step is a complex matter; depending on the depth, direction, and distribution of cracks, as well as the owner’s risk tolerance, different conclusions may be reached. Accurate judgments require extensive experience, and certain risks must be taken. Check the competence of the testing agency to see if it is reliable; don’t accept its opinions lightly – you need to make your own clear judgment. (In most cases, grinding it away and shortening the inspection cycle will suffice.) Good luck! ）
It took a tremendous amount of effort to locate all the microcracks. Unlike macrocracks, they cannot be detected by Ut mt pt.
Fortunately, it was possible to detect microcracks through metallographic examination – this is rare; I had thought they were macrocracks and was negligent······ Recommendations: (1) Conduct fluorescent magnetic particle testing on 100% of the welds, areas affected by arc strikes, and scars; (2) Perform multiple hardness tests on areas with T-joints, misalignment, or excessive angles; (3) Analyze the composition of any contaminants on unpolluted surfaces. If there are no issues with the points mentioned above, and under the conditions of stable operation, functional safety accessories, and unchanged medium properties, a testing cycle of 3 years can be proposed initially. Conditions must be created to conduct a re-examination within three years.
To ensure the proper operation of the equipment, all cracks must be identified. Otherwise, it poses a security risk