What exactly is the thinning rate for spherical head forming?
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Both GB150 and GB/T 25198 \"Pressure Vessel Heads\" state that the thickness of the head blank should take into account the thickness reduction due to manufacturing processes; the manufacturer shall determine the starting thickness of the head based on the manufacturing process used. Appendix J of GB/T 25198 provides recommended thinning ratios for elliptical and disc-shaped heads, but does not give recommended thinning ratios for stamped hemispherical and spherical cap heads. “The book \"Manufacturing and Maintenance of Pressure Vessels\" in the Practical Technology Series on Pressure Vessels states that thermal stamping of spherical heads results in significant thinning in the range of 20–30° near the bottom, and it provides reference values for the thinning rate of common materials such as carbon steel, low-alloy steel, and Cr-Mo steel at 12%–14%.
It should be determined through consultation with the manufacturing company, as it involves material selection and cost issues!
For spherical heads, it’s necessary to communicate with the manufacturer to clarify the specifications, materials, and heat treatment processes. The price must also be agreed upon, so as to avoid any problems after winning the bid
The manufacturing processes vary from one end cap manufacturer to another, as does the amount of thinning required. It is advisable to consult the end cap manufacturer before starting production and ask for a conservative estimate.