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What problems need to be addressed for the enlargement of spherical tanks? Requirements for high-strength steel. Due to the limitations on plate thickness that prevent on-site heat treatment for large spherical tanks, high-strength steel must be used for such tanks in order to reduce the thickness of their shells ； Welding properties and welding technology issues of high-strength steel. Due to the poorer weldability of high-strength steel compared to ordinary low-carbon steel, as well as its higher sensitivity to cracks, welded joints are prone to hardening, hydrogen embrittlement, and cracking (mainly cold cracking and delayed cracking), as well as angular deformation. The factors affecting hardened cracks are closely related to the composition of the electrode and flux, the shape of the groove, the amount of welding heat input, environmental conditions such as climate, and the direction of the weld bead, etc. Therefore, high standards are required for welding techniques, with strict welding procedures and considerable welding skills being necessary ； The problem of long weld lengths and prolonged operation time in large spherical tanks. Large spherical tanks have very long welds, often stretching for several kilometers; as a result, the required processing time is long and the investment costs are high, making automation essential ； Problems with on-site heat treatment. Residual stresses within welded components can cause deformation in those components and increase the risk of brittle failure. The combination of residual stress and hydrogen in the weld is responsible for the hardening of the heat-affected zone, as well as cold cracks and delayed cracks. Residual stress also plays an important role in the formation of corrosion cracks in corrosive media. Therefore, in practical engineering, various methods should be employed as much as possible to eliminate residual stresses ； On-site construction, assembly, and welding are required. Due to the large diameter of large spherical tanks, they cannot be transported; therefore, components such as spherical shells, struts, and spiral ladders are always manufactured at the factory, and then transported to the site where they are to be used for assembly and welding. The welding quality of high-strength steel is greatly affected by the environment, which leads to various issues related to welding techniques ； Issues related to welding conditions during construction inside the sphere. The welding conditions inside the sphere are extremely harsh. Large spherical tanks have very long welds, resulting in a large amount of welding work; often several workers are needed to carry out the welding simultaneously. However, the air inside the sphere does not circulate, and the sphere itself must be preheated to over 100°C. Therefore, it is necessary to study ways to improve the working conditions inside the sphere as well as to provide special protection for the welders ； Pillar and fundamental issues. Large spherical tanks have numerous supports, each of which is subjected to significant loads; it is difficult to arrange these supports at the same level. Moreover, when the foundation experiences localized settlement, it leads to uneven loading on the supports ； Issues of isolation and shock absorption for earthquakes. Due to the large total weight of large spherical tanks, they have significant mass and inertia. Moreover, since the supports of these tanks are tall, strong earthquakes can cause these supports to experience large bending moments; as a result, large bending stresses are generated at the junctions between the supports and the tank shell, as well as within the shell in those areas