In the verification of reinforcement for nozzle openings, is the outer diameter or the inner diameter of the nozzle used as the basis for calculating its thickness?
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The reinforcement for the opening in a device was checked, and when using SW6 to carry out this verification, it was found that the calculated thickness of the reinforcement in SW6 is based on the inner diameter of the pipe. In contrast, in the calculation documents provided by the design institute, the calculated thickness of the pipe is based on its outer diameter. There are two formulas for calculating the thickness of cylindrical walls in GB150.3; thus, it is clear that the reinforcement calculation in SW6 is carried out using formula (3-1), which is based on the inner diameter, while the design institute uses formula (3-2), which is based on the outer diameter. What we would like to discuss now is: 1. In the verification for reinforcing openings in connections, is the outer diameter or the inner diameter of the connection used as the basis for calculating its thickness? 2. Under what circumstances is the outer diameter used as a reference when calculating wall thickness? Under what circumstances is the inner diameter used as a reference?
The data provided by the current SW6 software is for reference only. When designing training, the instructor asks to use the inner diameter as a reference.
Personally, from a safety perspective, I think calculations should be based on the outer diameter, as this results in a greater wall thickness, which is a more conservative approach； From a cost-saving perspective, the inner diameter should be used as the basis.
If the calculation for the pipe fitting is done manually, I think it’s more appropriate to use the outer diameter as a reference, since the outer diameter of the pipe fitting is a fixed value, while the inner diameter is affected by the wall thickness. But usually, software is used for the calculations; using software to determine the inner diameter is also fine, and there are no safety issues with that
In general, the outer diameter remains unchanged during takeover, so the outer diameter is used as a reference when calculating the wall thickness. For a cylinder with a constant inner diameter, the wall thickness is generally calculated based on the inner diameter. The opening diameter dop for opening reinforcement is calculated based on the given outer diameter (see 6.3.3.1 of GB/T150.3). The original poster should understand why GB/T150-2011 includes a wall thickness calculation formula based on the outer diameter, as well as concepts related to the diameter of openings for reinforcement purposes when there are openings.
The diameter for calculating the opening reinforcement should be the inner diameter minus the corrosion allowance. The equal-area reinforcement requirement stipulates that the reinforcement area must be greater than or equal to the opening area.
This post was last edited by A13562570752 on 2021-3-18 at 16:57, with the inner diameter plus twice the thickness as the basis
What’s the difference? They are all derived from the diameter formula; one is expressed in terms of the inner diameter while the other is expressed in terms of the outer diameter. The essence is the same – use whichever is more convenient. The standards provide two methods, and you can choose whichever one you prefer
The diameter of the opening used for reinforcement and calculating the strength by treating the connecting pipe as a section of cylinder are two different things
The diameter of the opening used for reinforcement and calculating the strength by treating the connecting pipe as a section of cylinder are two different things