Questions regarding opening reinforcement using the equal area method for DN1500 cylinder openings
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This post was last edited by INJQZ on 2019-8-7 at 11:02. There are two devices with diameters of DN1500 and DN1550; the reinforcement via opening calculations is carried out using the equal area method: (1) For DN1500, the maximum opening size is 520 mm; (2) For DN1550, the maximum opening size is 516.6 mm. It is clear that there is an issue with the openings around the DN1500 diameter. As the diameter increases, the maximum opening size according to the equal area method actually decreases. Regarding GB/T150.3, Figure 6-1, the \"upper limit of the applicable range of the equal-area method\" seems to have a problem as well, right? Why is this? Can the opening size for DN1550 be set to 520mm?
A brief explanation of the GB150 standard
Teacher, the explanation doesn’t give an answer! ?
When D ≤ 1500, the maximum opening reinforcement is such that d ≤ 520; when D > 1500, the maximum opening reinforcement is such that d ≤ 1/3D and d ≤ 1000. For equal-area reinforcement, an opening of 520 is permissible.
Do you mean the standard is wrong, or that one doesn’t understand the standard? It will become clear if you look at the origin of the equal-area method
Hehe. Finally, someone has noticed this problem. If a standard is wrong, then it’s wrong; standards are created by humans, and it’s entirely possible that there are mistakes in them.
This post was last edited by wanlirn on 2019-8-12 at 16:21; it wasn’t an oversight； According to American standards, the outer diameter of a DN500 pipe is 508, while the outer diameter of the pipes we commonly use is 530. If we simply apply the American standard values, then pipes with dimensions of 530X10 would not be suitable for use in applications that require equal-area reinforcement. It would also be wasteful to design such pipes with dimensions of 530X20. The value of 520 mm was determined based on actual conditions in China; it was specifically adjusted accordingly. It’s important to study standards in order to understand the reasons behind these specifications. Additionally, I would like to emphasize the need for standardization and serialization in pressure vessel standards – a standard titled “Nominal Diameter of Pressure Vessels” should be established. Insisting on using a diameter of 1510 seems a bit unreasonable
Agreement is not something that constitutes a standard oversight (if it were an oversight, the value would not remain 520 from version 89 to version 2011). Considering the specifications for manholes, if the diameter of the opening is set at 500, it is generally not possible to install a DN500 manhole (with a pipe outer diameter of 530). The diameter of DN1550 mentioned by the poster, or even DN1510, is very rare; such a design is not used unless there are special circumstances.
The key point is that in most manufacturing plants, seamless pipes are hardly considered for openings larger than 400 mm; perhaps I’ve encountered few such manufacturing plants. Taking the DN500 manhole structure as an example, factories generally use steel plates that are rolled into shape directly, with only a short longitudinal seam added; this approach is obviously more cost-effective than purchasing a DN500 seamless pipe directly.
Whether it is rolled by oneself or using seamless tubes, it still needs to be connected to flanges. Flanges are usually standard components that are purchased; under normal circumstances, no one designs flanges on their own for access holes.