Spherical Tanks vs. Vertical Tanks: Comparison of Structural Differences, Storage Efficiency, and Suitable Media

Spherical Tanks vs. Vertical Tanks: Comparison of Structural Differences, Storage Efficiency, and Suitable Media

Spherical tanks and vertical tanks are two mainstream types of equipment in the industrial storage field. Due to differences in their structural designs, they have distinct roles in terms of storage efficiency and suitable media. The selection of either type must be based on a comprehensive assessment of media characteristics, site conditions, and cost budgets.

Structural differences lie in their core shapes and stress design. Spherical tanks feature a "spherical" core structure, with tank walls assembled from multiple curved steel plates and supported by pillars fixed on a concrete foundation. They have no obvious edges or corners and distribute stress evenly—internal pressure can be uniformly dispersed across the spherical surface, resulting in a tank wall thickness that is only 1/2 to 2/3 that of a vertical tank of the same volume (e.g., for a 1,000 m³ tank, the wall thickness of a spherical tank is approximately 16 mm, while that of a vertical tank is around 24 mm). In contrast, vertical tanks have a "cylindrical + elliptical/flat top" structure, with the tank body placed vertically on an annular foundation. Their walls are straight cylindrical, with a manhole and breather valve on the top and a sewage outlet at the bottom. Stress is concentrated at the junction of the tank wall and the foundation, requiring stiffening rings to enhance wind load resistance and seismic performance. For large-volume vertical tanks (over 5,000 m³), buttress columns must be added to the outer side of the tank wall.

Storage efficiency differences focus on space utilization and media loss. Thanks to their compact spherical structure, spherical tanks occupy only 60% to 70% of the floor space of vertical tanks with the same volume (e.g., a 2,000 m³ spherical tank occupies approximately 50 m², while a vertical tank of the same volume takes up around 80 m²). Additionally, spherical tanks have no dead corners inside, resulting in minimal media residue (residue rate < 0.5%), making them suitable for storing precious metals or high-purity media. However, spherical tanks are relatively tall (typically 10–20 m), requiring strict site clearance height, and it is inconvenient to install agitators or heating devices inside. Vertical tanks, on the other hand, offer flexible height adjustment (3–30 m) and can be customized according to site height. They easily accommodate internal heating coils or agitators, making them ideal for media requiring temperature control or agitation. Nevertheless, vertical tanks occupy more floor space, have a higher media residue rate (approximately 1%–2%), and their vertical walls are prone to swaying under wind loads, necessitating additional reinforcement.

Suitable media must align with the structural characteristics of the tanks. Spherical tanks, with their high pressure resistance (design pressure: 0.8–3.0 MPa) and excellent sealing performance, are preferred for storing high-pressure, flammable, explosive, or volatile media such as liquefied natural gas (LNG), liquid ammonia, and propane. They are particularly suitable for medium-to-large storage capacities (1,000–5,000 m³). Vertical tanks are categorized into atmospheric pressure (design pressure < 0.1 MPa) and low-pressure (0.1–0.8 MPa) types. Atmospheric vertical tanks are suitable for storing atmospheric media like crude oil, diesel, and lubricating oil, while low-pressure vertical tanks can store low-pressure volatile media such as methanol and ethanol. Moreover, vertical tanks have lower manufacturing costs (only 50%–60% of that of spherical tanks), making them more suitable for small-to-medium storage needs (below 1,000 m³). Additionally, highly corrosive media (e.g., hydrochloric acid, sulfuric acid) are better stored in vertical tanks, as their tank walls allow for easy anti-corrosion coating repair—unlike spherical tanks, whose curved walls are more difficult to repair.