Calculations for non-standard disc-type end caps
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This non-standard head has Ri=Di and ri=0.06Di, and it seems that the strength calculations do not meet the requirements specified in SW-6. It seems that GB150 also requires Ri=0.9Di, with ri being 0.1Di... Please provide the method for strength calculation~~~
GB150.3 specifies that the inner radius of the spherical portion of a butterfly head shall not be greater than the inner diameter of the head; generally, Ri is taken as 0.9Di. The inner radius at the corner of the head, r, shall be not less than 0.1 times the inner diameter of the head, and also not less than 3 times the nominal thickness of the bottom. This is a requirement specified by the standard. What the original poster described no longer meets the standard requirements. If calculation must be carried out under the aforementioned conditions, then the analytical design method can only be used. Conventional design cannot solve this problem. The deformation of a butterfly head under internal pressure is similar to that of an elliptical head; when subjected to internal pressure, the butterfly head assumes an elliptical shape, which results in circumferential compressive stresses in the transition zone of the head, posing a risk of instability. This circumferential compressive stress increases as the ratio of the sphere radius to the torus radius increases, thereby increasing the likelihood of instability. It is for this reason that GB150.3 specifies that Ri/r should not exceed 10. As the original poster mentioned, the ratio between the two has reached 16.7, making it more likely to become unstable. I don’t understand why this type of butterfly head is used.
I’m doing this mainly to ensure the overall length; the end cap with a thickness of 0.06 refers to the commonly used disc-shaped end caps specified in clause 4.2 of GB25198-2010
Calculations can be carried out with reference to relevant ASME standards; if the values still exceed the limits, then analytical design should be chosen.