A question regarding the flaw detection of manhole rolling sections
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This post was last edited by KmFstyle on 2017-12-18 at 13:17. In pressure vessels, when the manhole diameter is over 400, the cylinder sections are generally rolled, which results in a weld seam. Regarding the non-destructive testing of this weld seam at 150 pressure levels, the most relevant statement is as follows: However, my understanding of this statement is that it refers to the circumferential seams between pipes or between pipes and flanges; whereas the weld seam on a flanged cylinder section is a longitudinal seam. How should radiographic testing be carried out in such cases? The equipment rating is 20%/AB/III. How should the seam ratio and the acceptable quality level be determined? Everyone, please offer some advice or discuss this with me; thank you all!
Everyone, please offer some advice or discuss this with me; thank you all!
The non-destructive testing requirements for the longitudinal seams of manhole sections are the same as those for the main design welds. In your case, if the tube sections are not long and one X-ray image is sufficient, it’s fine to indicate 100% RT; the quality level will be the same as that of the main structure.
Yes, if it’s not long, it’s definitely 100%. Anyway, it’s a waste not to use a film even if it’s not needed. I’m wondering what ratio or level should be used if the length is greater Are there any standard regulations or other bases?
In accordance with 10.3.2 of GB/T150.4: For local radiographic or ultrasonic testing of the equipment, since the manholes are not subjected to external loads, local radiographic or ultrasonic testing can be employed, with a compliance level of Grade III.
Consistent with the inspection requirements for weld joints to the equipment body
Generally, the length of the pipe sections for ordinary applications is less than 300 mm, so one negative is sufficient. The qualification level is consistent with the inspection requirements for the weld joints to the main body of the equipment.
Components such as manhole sections and large pipes, along with their rolled welds, are not very long; conducting 100% non-destructive testing on them does not result in significant cost increases, while it also ensures safety. The required quality standard for these components is the same as that for the main structure.
Check the requirements on the drawing. If the drawing specifies requirements for this weld, follow those specifications. If not specified, follow the testing requirements for the cylinder body.
The requirements for manhole segments and the longitudinal welds of the equipment are the same.
The acceptable grade for the longitudinal seam shall be determined according to the design calculations; since the welding joint coefficient for this pipe fitting in the calculations is 1, the acceptable grade should be Grade II