What should be done if the pressure in the spherical tank exceeds 6.4 MPa or if the thickness exceeds 50 mm?

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There are many media available now, and discussions are underway to select a solution with a slightly higher pressure level. Such as carbon dioxide, hydrogen, etc. According to standard GB12337, the value shall not exceed 6.4 MPa for spherical tanks supported by columns ； The thickness should not exceed 50 mm. In actual engineering projects, what are the maximum thicknesses that have been achieved?   As far as the editor knows, the maximum thickness achieved in previous years was 54/56 mm (Q370R\15MnNbR), while Jingmen Hongtu has reached a maximum thickness of 57 mm (Q370R). The Luoyang Institute has designed ethylene spheres made of 66mm (09MnNiDR) material; these are likely the thickest spheres ever built to date.        If the thickness is large, then the requirements for the press are also very high. At present, the largest press in China has a capacity of 3,000 tons, and a pressing thickness of around 100 mm should not pose any problems. Minimum thickness requirement: The minimum thickness of the spherical tank shell plates is not specified by standards, unlike the maximum thickness ； For the minimum thickness, as long as it meets the stiffness and transportation requirements of the spherical shell, it is generally acceptable. However, based on years of design experience, if the steel plate is too thin, design institutes generally consider increasing its thickness.      The lower limit of the shell plate wall thickness is primarily determined by the stiffness requirements of the shell.      During the pressing of thin sheets, deformation, bulging, and wrinkling can occur easily; sometimes repeated pressing and straightening are required to achieve good pressing accuracy.      Shell plates are also prone to deformation during transportation, storage, and lifting.       Generally, when the plate is thin, the design institute will divide it into more zones and install more dome plates. In actual engineering projects, what are the smallest thicknesses that have been used?      It is understood that for spherical tanks with a volume of less than 2,000 cubic meters, the minimum wall thickness has been as low as 14–18 mm. For spherical tanks with a volume of 3000 cubic meters or more, the minimum thickness is above 22 mm, and the shell plates are arranged in more zones. Conclusion: Spherical tanks are generally used in medium and low pressure applications, that is, at pressures not exceeding 10 MPa; theoretically, they can be manufactured as such. However, when the pressure exceeds 7.5 MPa, it may be necessary to evaluate the cost-effectiveness of using spherical tanks. The design pressure for spherical tanks is, in principle, not more than 6.4 MPa; however, if it exceeds 6.4 MPa, special approval can be obtained through a separate review process, though this method may take a longer time. There is another approach as follows. Containers with a pressure exceeding 6.4 MPa can be designed in accordance with the standards GB/T 150 and JB/T 4732 for pressure vessels. GB/T 150 applies to pressure vessels whose design pressure is not greater than 35 MPa; it does not specify any requirements regarding the thickness of such vessels. As long as the factory’s manufacturing capabilities and the steel rolling capabilities allow it, such designs are feasible. So, can spherical tanks still be used when the pressure exceeds 6.4 MPa? By giving them a different name, i.e., spherical containers, and using a different standard, it’s still possible to use them.