How is the proportion of non-destructive testing for pipelines determined, and which specifications are applied in practice?

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How should the proportion of non-destructive testing for petrochemical pipelines be determined? What are the relevant specifications for hydrogen-handling systems, oil and gas pipelines, underground water supply and drainage systems, underground sewage pipelines, etc.? How are these specifications implemented? Are there any conflicts between different standards? SH3533 – Water supply and drainage: For pipes with a design pressure greater than 1 M Pa and less than or equal to 1.6 M Pa, the proportion of weld joints of the same pipeline number that are subjected to non-destructive testing by the same welder must be no less than 5%, with at least one joint undergoing such testing. Pipelines with a design pressure of less than or equal to 1 MPa may be exempted from non-destructive testing. Welded joints subjected to non-destructive testing are evaluated in accordance with JB4730 and are considered qualified at grade III. Unqualified welds should be repaired, with the number of repair attempts preferably not exceeding three