Why are spherical heads chosen for large-diameter containers? What size counts as large?
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Why do all the large-diameter towers I’ve seen use spherical heads? Is it because the elliptical head has stress concentration zones, which can lead to instability when its size is large? How big does ‘big’ even mean? Is it also related to thickness?
What is the diameter of the large-diameter tower you saw?
Over six meters, over seven meters, and also nine meters
After reviewing several papers, there are roughly the following views: 1. It is difficult to shape large-sized elliptical end caps; one article states that a factory in China is only able to produce ones with a diameter of 6.8 meters, due to limited equipment at that factory. 2. The thickness reduction in the transition zone of the oval head is approximately 10% to 12%, which results in a significant increase in the design thickness. Once this value exceeds the standard limit, overall heat treatment is required; however, it is difficult to carry out overall heat treatment on large-sized heads. 3. The hemispherical head distributes forces evenly, resulting in a lower required thickness and thus material savings; this offers significant economic benefits for large-diameter equipment.
For large-diameter container heads, whether they are elliptical or spherical in shape, they need to be pressed in segments; however, when pressing elliptical heads in segments, moldings are required, which increases the cost. For the segmented pressing of spherical heads, spot pressing is sufficient, eliminating the need for custom dies.
It has little to do with size and is related to thickness; moreover, when the pressure is high, even a thinner layer can withstand more force