A steel sealed container used for storing liquids or gases is called a storage tank. Storage tank engineering is an essential and important infrastructure in industries such as petroleum, chemical, grain and oil, food, fire protection, transportation, metallurgy, and national defense. Our economic life is always inseparable from various sizes of steel storage tanks, and the important role of steel storage tanks in the development of the national economy is irreplaceable. Steel storage tanks are specialized equipment for storing various liquid (or gas) raw materials and finished products. For many enterprises, normal production cannot occur without storage tanks, especially since the national strategic material reserves rely on various capacities and types of tanks. In our country, oil storage facilities are mainly above-ground tanks, predominantly with metal structures. Commonly used types include dome-top tanks, internal floating roof tanks, and horizontal tanks.

       A steel sealed container used for storing liquids or gases is called a storage tank. Storage tank engineering is an essential and important infrastructure in industries such as petroleum, chemical, grain and oil, food, fire protection, transportation, metallurgy, and national defense. Our economic life is always inseparable from various sizes of steel storage tanks, and the important role of steel storage tanks in the development of the national economy is irreplaceable. Steel storage tanks are specialized equipment for storing various liquid (or gas) raw materials and finished products. For many enterprises, normal production cannot occur without storage tanks, especially since the national strategic material reserves rely on various capacities and types of tanks. In our country, oil storage facilities are mainly above-ground tanks, predominantly with metal structures. Commonly used types include dome-top tanks, internal floating roof tanks, and horizontal tanks.

Standards for storage tanks:

       Commonly used storage tank standards: 1. American Petroleum Institute Standard API650; 2. British Standard BS2654; 3. Japanese Standard JISB8501; 4. German Standard DIN4119; 5. Petroleum Industry Standard SYJ1016-82; 6. Petrochemical Industry Standard SH3046-92.

Materials for storage tanks:

       Polypropylene storage tanks and materials required for storage tank engineering are divided into tank body materials and auxiliary facility materials. Tank body materials can be classified into low-strength steel and high-strength steel based on tensile yield strength (бs) or tensile standard strength (бb). High-strength steel is mostly used for tanks with a capacity of over 5000 cubic meters. Auxiliary facilities (including wind-resistant ring beams, lock openings, ladders, railings, etc.) are made of lower-strength ordinary carbon structural steel, while other components and accessories are made of different materials based on their specific uses. Common domestic steel materials used for manufacturing tank bodies include 20, 20R, 16Mn, 16MnR, Q235 series, and other new materials.

Structure of storage tanks:

       Dome-top tanks refer to a type of steel container with a dome-shaped top and a cylindrical body. Dome-top tanks are simple to manufacture and inexpensive, making them widely used in many industries both domestically and internationally, with the most common volumes ranging from 1000 to 10000m³. The maximum volume of dome-top tanks in the country has reached 30000m³.

       Tank bottom: The tank bottom is assembled from steel plates, with the central steel plate being a middle plate and the surrounding steel plates being edge plates. Edge plates can be strip plates or arc plates. Generally, when the inner diameter of the tank is < 16.5m, strip edge plates are preferred; when the inner diameter is ≥ 16.5m, arc edge plates are preferred.

       Tank wall: The tank wall is formed by welding multiple rings of steel plates together, which can be either sleeve-type or straight-type.

       The sleeve-type tank wall plate uses overlapping for circumferential welds and butt welding for longitudinal seams. This form is commonly used for dome-top tanks, as it facilitates the assembly of each ring wall plate and is safer when constructed using an inverted method. The straight-type tank wall plate uses butt welding for circumferential seams. Its advantage is that the diameter of the tank wall is the same from top to bottom, making it particularly suitable for internal floating roof tanks, but it requires higher assembly installation standards and is more challenging.

       Tank top: The tank top is made up of multiple fan-shaped plates welded together to form a dome shape. The inner side of the tank top is reinforced with flat steel ribs, and the fan-shaped plates are connected with overlapping welds. The entire tank top is welded to the angle steel ring (also known as the lock opening) at the upper part of the tank wall plates.

Floating roof type

       Floating roof tanks consist of a floating roof that rests on the surface of the medium and a vertical cylindrical tank wall. The floating roof rises and falls with the increase or decrease of the medium stored in the tank, and there is an annular sealing device between the outer edge of the floating roof and the tank wall, ensuring that the medium inside the tank is always directly covered by the internal floating roof, reducing medium evaporation.

       Tank bottom: Floating roof tanks generally have a larger volume, and their bottom plates are made of arc edge plates.

       Tank wall: The straight-type tank wall is used, and the butt welds should be ground smooth to ensure a flat inner surface. The upper part of the floating roof tank is open, and to increase the rigidity of the wall plates, wind-resistant ring beams and reinforcement rings should be set at the top of the tank wall according to the wind load in the area.

       Floating roof: Floating roofs can be categorized into single-deck floating roofs, double-deck floating roofs, and buoy-type floating roofs.

       Single-deck floating roof: Composed of several independent compartments forming a ring-shaped floating structure, with a single deck top plate on the inner side of the ring. The bottom of the single deck top plate is reinforced with multiple circular steel rings. Its advantages are low cost and easy maintenance.

       Double-deck floating roof: Composed of an upper deck plate, a lower deck plate, and edge plates of the cabin, divided into several independent annular compartments by radial and circumferential partitions. Its advantages are high buoyancy and good drainage.

Internal floating roof type

       Internal floating roof tanks are formed by adding a floating roof inside a dome-top tank. The addition of a floating roof inside the tank can reduce the evaporation loss of the medium, while the external dome top prevents rainwater, snow, and dust from entering the tank, ensuring the cleanliness of the medium inside. This type of tank is mainly used for storing light oils, such as gasoline and aviation kerosene. Internal floating roof tanks use straight-type tank walls, with butt welding of the wall plates, and the dome top is made according to the requirements of dome-top tanks. Currently, there are two structures of internal floating roofs in the country: one is a steel floating roof similar to that of floating roof tanks; the other is an assembled aluminum alloy floating roof.

Horizontal type

       Horizontal storage tanks generally have a volume of less than 100m³ and are usually used in production processes or gas stations. The circumferential welds of horizontal storage tanks use overlapping, while the longitudinal welds use butt welding. The ring plates are arranged alternately, taking an odd number to ensure the end cover diameters are the same. The end covers of horizontal storage tanks are divided into flat end covers and dish-shaped end covers. Flat end cover horizontal storage tanks can withstand an internal pressure of 40kPa, while dish-shaped end cover horizontal storage tanks can withstand an internal pressure of 0.2Mpa. Underground horizontal storage tanks must be equipped with reinforcement rings, which are made of bent angle steel.