First, what are the problems with the selection standards for thick-walled steel pipes?
1. Standards are formulated based on a standardized system. While there are standards for steel pipes used in engineering projects, there are no corresponding standards for forgings or castings. In reality, forging standards for steel pipe fittings borrow from pressure vessel forging standards, without considering the differences between the two, such as welding and radiographic inspection regulations.
2. The standards for steel pipe fittings vary widely in level, lacking consistency and systematicity, leading to contradictions and inconvenience in use.
3. There are no type testing standards for steel pipe fittings. Only GB12459 and GB13401 standards specify the pressure calculation for burst tests of seamless steel butt-welded steel pipe fittings and steel plate butt-welded steel pipe fittings. Other types of testing standards or implementation standards to ensure the manufacture of steel pipe fittings are lacking.
The formula for the weight of a thick-walled seamless steel pipe is: [(outer diameter - wall thickness) * wall thickness] * 0.02466 = kg/meter (weight per meter).
Second, what are the details regarding the strength grades of thick-walled steel pipes?
1) For steel pipe fittings whose grade is expressed by nominal pressure or specified pressure-temperature rating, the pressure-temperature rating specified in the standard should be used as the basis for their application, such as GB/T17185.
2) For steel pipe fittings whose nominal thickness is only specified in the standard for the straight pipe to which they are connected, the applicable pressure-temperature rating should be determined according to the base steel pipe grade specified in the standard, such as GB14383~GB14626.
3) For steel pipe fittings whose external dimensions are only specified in the standard, such as GB12459 and GB13401, their pressure-bearing strength should be determined through verification tests.
4) For others, the application basis should be determined according to relevant regulations through pressure design or analytical analysis. Furthermore, the strength grade of the steel pipe fittings should not be lower than the pressure under the severe operating conditions that the entire steel pipe system may encounter during operation.
Post time: Feb-04-2026