Issues with new GB150 steel pipes
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This post was last edited by Linglingqi on 2024-12-30 at 16:30. Regarding the issue of operating temperature for pipes: it is required by clause 6.1.5(d) of GB150.2-2024. Can it be understood in this way: those with an outer diameter of less than 76 and a wall thickness of less than 6.5 cannot be used for impact testing, or pipes with a diameter greater than 76 mm but a thin wall thickness cannot have impact samples taken from them; can they still be used at -20°C?
Yes, in accordance with clause 6.1.5 d) of GB150.2-2024, pipes whose outer diameter is less than 76 mm and wall thickness is less than 6.5 mm, or those whose diameter is greater than 76 mm but have such thin walls that it is not possible to obtain impact test samples, can also be used at -20°C. .
I think it is inappropriate to understand this article in this way. Those that can undergo impact testing at -20°C in accordance with the specifications can be used for such testing; they are suitable for use at -20°C. Those that cannot be tested at -20°C can only be used at 0°C℃
Furthermore, the additional -20°C impact test should theoretically not be the one conducted by the equipment manufacturer upon delivery for re-inspection; rather, it should be the -20°C impact test carried out by the steel pipe manufacturer in accordance with the terms of the contract.
Floor 3 agrees, Floor 4 disagrees. Is there any difference in the -20°C impact tests for steel pipe factories and manufacturing plants?
There’s a big difference: what the steel pipe factory produces is a document certifying the quality of the material at the time of shipment, while what the manufacturing plant produces is related to re-inspection; the responsible parties are different
It can be understood in this way according to the meaning of the provisions. But if this is done, the small-diameter 20-mm pipes cannot be used at -20°C, while the larger-diameter ones can; this can easily lead to confusion, isn’t it creating problems for the designers?
There is a difference: when it’s the steel pipe factory that performs the impact test at -20 degrees Celsius, it is because your purchase requirements specify that the steel pipe factory must carry out this impact test, and this result needs to be included in the material warranty certificate. When the manufacturer conducts the impact test, it is part of the reinspection of the material. As for the final result, in both cases an impact test has been performed
As I understand it, for 20 Number steel, it is required that an impact test be conducted before the lower limit on the operating temperature can be reduced; regardless of the size, if the size being used does not meet the requirements, then it cannot be used at all.
Unable to take a sample? The pipes that are to be taken over have provisions made for that, right? It’s totally possible to conduct experiments, isn’t it? If not done, it should not default to -20°C. Based on my understanding, the length of the sample to be retained from the tube ends of shell-and-tube exchangers is 150-250 mm
20# steel that has not been subjected to -20°C impact testing cannot be used in design conditions at -20°C. It’s fine to take advantage of loopholes in the rules, but if anything goes wrong, it will land you in trouble and forcing you to rely on public funds.