On the scope of application of the equal area method
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I have a question that I would like to ask the experts: The inner diameter of the cylinder is DN3000, while the diameter of the opening is DN1000. An opening is made in the casing. According to clause 6.3.3.1 of GB150.1~4, for oblong holes, the length should be taken as the chord length of the relevant interface dimension plus twice the thickness allowance. Should this chord length be based on the outer diameter or the inner diameter of the pipe? This chord length determines whether the provisions in item a) of clause 6.1.1 apply; if it’s based on the inner diameter, the value is less than 1000 and those provisions can be used, whereas if it’s based on the outer diameter, the value is greater than 1000, in which case analytical methods must be employed along with local reinforcement. In my personal understanding, when it comes to the chord length of an elliptical opening, the inner diameter should be taken into account. As stated in 6.3.3.1, an additional amount equal to twice the thickness needs to be added; this would represent the chord length of the opening as it exists without any account for corrosion allowance or negative deviations
You understand correctly. For circular openings, the diameter of the opening is the inner diameter of the pipe plus twice the thickness addition.
In the stress reinforcement calculations for GB150, the diameter of the openings is calculated based on the inner diameter, not the actual diameter of the hole made in the shell.
Of course it’s the inner string length! It is the same as the definition of the equal area method.
I agree with the view from the second floor. Also, you mentioned an oblong hole – 1. What are the dimensions of the opening? Currently, I only know about DN1000 and 2; how should the orientation of the openings be arranged?