Features of spherical tanks

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This post was last edited by wangzhwei on 2017-3-15 at 12:00. Spherical containers are widely used in various industries in China; for example, in the petroleum, chemical, metallurgical, and urban gas industries, they are employed for storing materials such as liquefied petroleum gas, liquid oxygen, liquid nitrogen, liquid hydrogen, liquid ammonia, oxygen, nitrogen, natural gas, urban gas, and compressed air； In nuclear power plants, spherical containers are used as nuclear containment structures ； Used as cooking balls in paper mills ； It is also used as reactors, etc., in chemical plants. Therefore, we refer to spherical containers used for storing gaseous or liquid media as spherical storage tanks (abbreviated as “spherical tanks”). Shell structures are mainly divided into three types: football-leaf type, orange-leaf type, and mixed type. Most spherical tanks designed, manufactured, and welded domestically are of the segmental type. The division of the shell in a football-shaped dome is similar to that of a football; all the shell panels are of the same size, which is why it is also called the equal division method. The advantages are that each spherical shell plate has the same size, allowing for standardized cutting and forming; this results in high material utilization and good interchangeability. The assembly welds are short, which reduces the workload associated with welding and inspection. The disadvantages include complex weld arrangements, difficulties in construction and assembly, and high requirements for the manufacturing precision of the spherical shell plates. Due to constraints imposed by steel plate specifications and the structure itself, this method is generally suitable only for manufacturing spherical tanks with a volume of less than 120 m3. The shell division of an orange-slice type spherical tank is similar to that of orange segments, and it represents the most common design format. The advantage is that the weld layout is simple, assembly is easy, and the fabrication of the spherical shell plates is straightforward; the disadvantage is low material utilization. The shell structure of a hybrid spherical tank consists of orange-petal segments in the equatorial and temperate zones, and football-petal segments at the polar plates. By combining the advantages of the orange-petal and football-petal structural forms, it achieves a higher material utilization rate, reduces weld length, decreases the number of shell plates, and is particularly suitable for large spherical tanks. This structure is widely used abroad. With the rapid development of industries such as petroleum, chemicals, and urban gas in our country, many large spherical tanks with hybrid structural designs have been introduced in recent years. Through research and development related to the construction of these imported tanks, China has essentially mastered the design, manufacturing, assembly, and welding techniques for spheres using this type of structural approach. Storage pressure vessels are generally of cylindrical or spherical shape. Spherical tanks are typically composed of components such as a spherical shell, support struts, manway connections, and ladder platforms. Spherical tanks have the following advantages: 1. Compared to cylindrical vessels of the same volume, spherical tanks have the smallest surface area, which results in lower steel usage. 2. The spherical tank is subjected to uniform stress; and at the same diameter and operating pressure, its membrane stress is 1/2 that of a cylindrical vessel, hence its wall thickness is also only 1/2 that of a cylindrical vessel. 3. Since the wind coefficient of spherical tanks is 0.3, whereas that of cylindrical vessels is around 0.7, spherical tanks are safer against wind loads than cylindrical vessels. 4. Compared with cylindrical containers of the same volume, spherical tanks require less floor space and can be built to greater heights, which facilitates the efficient use of land area. In summary, spherical tanks have advantages such as low floor area, thin wall thickness, light weight, reduced material usage, and low cost.