Tapered head – when is flanging necessary? Flanging thinning amount

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The conical heads of pressure vessels are primarily classified based on the half-apex angle α of the cone. (For the position of α, please refer to the cover drawing below.) (1) When α > 60°, it is approximately equivalent to a flat cover, and should be designed, analyzed for strength, or subjected to stress analysis as a flat cover. (2) When α≤60°, it is further divided into three different cases at 30° and 45°. When ≤30°, flanging is not required. When it is ≥30° and ≤45°, flanging is required at the larger end. When ≥45°, flanging is required for both the large end and the small end. The method for calculating the thinning amount of flanged cones relies primarily on the formula: Thinning amount = K×t, where K is the flanging coefficient – a value that depends on factors such as the flanging process and the properties of the material. For example, the flanging coefficients differ between hot pressing and cold pressing processes ； t is the wall thickness of the head, that is, the original wall thickness before flanging. Generally speaking, the greater the wall thickness, the greater the amount of thinning that occurs during the flanging process. Using this formula, it is possible to calculate the wall thickness reduction during the flanging process. However, when designing, engineers often lack an accurate value for the flanging coefficient K. Generally, in actual engineering design, the thinning amount is usually controlled at 5% to 10%, which is less than the 13% thinning amount required for processing elliptical end caps. You can refer to this value to determine the thickness of the conical head.