Head plates are called “kagamiita” or “kyohan,” which means mirror plate in Japanese. Various theories seek to explain this. One says that the term “kagamiita” comes from the word used for the lid of a wooden sake barrel, which is “kagamiita.” Another theory explains that a head plate resembles a New Year’s rice cake, “kagamimochi” (mirror rice cake) in shape. Other countries refer to head plates using the following words:
USA: Head plate
UK: End plate
Head plates are widely used as the end faces of various industrial equipment, tanks, and pressure vessels. A head plate is a semispherical part similar in shape to a New Year rice cake. Head plates are currently vital to plants and facilities in various fields, including food processing, chemical refining, power generation, and gas or petroleum storage.
Think of a balloon. Balloons vary in shape. As they are blown up, balloons of various shapes all become spherical. When the inner pressure spreads and stabilizes, a sphere is the optimum shape. This also applies to metal. To withstand internal or external pressures, the part must have the shape of a sphere.