Is the national standard correct or is the industry standard correct? . ? ?
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Let’s start with the parameters of our gas-steam combined cycle’s main steam: design/operating pressure = 4.2/3.8 MPa, design/operating temperature = 455/450°C; the diameter of the main steam pipe is DN150, with an outer diameter of 159 mm. During non-destructive testing, the issue of the sampling rate for inspecting the welds in the main steam pipes comes into play. According to DL/T 869-2012 \"Code for Welding Technology in Thermal Power Plants\", the sampling rate should be 50%, as shown in the screenshot below. On the other hand, per Tables 8.1.1 and 8.2.1 of GB 50184-2011 \"Code for Acceptance of Construction Quality of Industrial Metal Piping Projects\", the sampling rate is 20%. See the screenshot below: Why do different standards yield different results? Which standard should be followed after all? Also, is the standard merely a minimum requirement, allowing us to apply stricter standards, such as raising the sampling rate to 100%? Please, experts, offer some advice. Thank you all, fellow sailors.
The first screenshot is from the electrical standards, while the second and third screenshots are from the mandatory standards.
**Standards only specify lower limits; industry standards or local standards can only be stricter than the **standards, but must not violate** them! Also, I can’t remember in which book I read it: there are industry standards, and those should be followed; if no such standards exist, then **the standard** should be applied. Industry standards are those included within **standards
Thank you for your answer, dear. Bye-bye.
The answer is upstairs! National standards are mandatory standards, and industry standards should be greater than or equal to national standards.
Where industry standards exist, those standards shall be followed; where no such standards exist, **standards shall be applied.
If the industry standard requires more than the national standard, follow the higher one rather than the lower one
If the pipeline belongs to the power industry, it must comply with DL standards； If the pipeline is an industrial pipeline, it shall be governed by GB standards. For your reference
By the way: Are the pipes that supply steam for production to other factories considered thermal pipes within public pipelines, or power pipes within industrial pipelines?
Pipes that supply steam for production to other factories are industrial pipes.