Non-destructive testing of steam distribution cylinders
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For a steam distribution cylinder with a tubular shell, it is not necessary to provide inspection holes. Designed in accordance with the new specifications, is it feasible to use a 20% rate for non-destructive testing? Regarding this issue, how should clause 3.18(12) of the new regulatory standards be understood? For pressure vessels for which it is not possible or unnecessary to provide inspection holes, the design unit shall propose specific technical measures, such as increasing the number of inspection items or the proportion of inspections during manufacturing, and shall also specify the key inspection items and methods to be used for regular inspections during the equipment’s operation.
No inspection holes will be provided; 100% non-destructive testing of the welds will be carried out, and the calculated thickness of the shell will be indicated for reference by the inspection department.
A 20% ratio for non-destructive testing is sufficient
Using pipes as the cylinder for the steam distribution cylinder eliminates the need for inspection holes, and it is entirely feasible to use a 20% ratio for non-destructive testing. If a header closure is used, there is no problem at all without Class A or B welds ； If a head structure is used, and double-wall single-projection radiographic testing is employed, a 20% ratio also meets the requirements of the Code. Furthermore, the design only specifies product requirements and does not outline specific technical measures or processes.
Thank you to the previous speakers for their answers. What I mean is, in accordance with new code requirement 3.18(12) and the requirements for energy conservation and consumption reduction, what should be the ultrasonic testing rate for DN426 drum vessels without manholes: 20%, 50%, or 100%?
Let’s ask a new question: For example, if this pressure vessel lacks inspection holes and, as a result, the proportion of non-destructive testing required in its design is set at 100%, then should the weld coefficient and the acceptable level for non-destructive testing be based on 1.0/ⅡAB for 100% NDT, or 0.85/ⅢAB for 20% NDT?
20% is sufficient; indicate the calculated thickness on the drawing
May I ask why? Is there any evidence? Thank you
The last edit to this post was made by wanlirn on 2021-4-13 at 14:26; increasing it to 100% still results in a score of 0.85, meaning the film is considered qualified for Grade III ； For steam distribution cylinders made of seamless tubes, our company uses a thickness of 0.85. Choosing a thickness of 1 would be too complicated. For grade II components, the tube diameter is always small and the curvature is low, which means many more tests are required. The savings from using a thinner wall thickness aren’t enough to cover the cost of additional tests and labor. In any case, it’s necessary to consult with the manufacturer directly. How much can a steam distribution cylinder possibly cost?