A large storage tank with a plum blossom-shaped cross section

Abstract

The present invention belongs to the technical field of large storage tanks, and particularly relates to a large storage tank with a plum blossom-shaped cross section. A large storage tank with a plum blossom-shaped cross section includes a tank wall, and the cross section of the tank wall is plum blossom-shaped. The plum blossom shape is formed by connecting a plurality of segments of arcs A with openings facing inwards and arcs C with openings facing outwards, the connection points between the arcs A and C are tangent, and the radius of the arc A is greater than the radius of the arc C. The arc C extends out an arc D, and the arc D and the arc C form a full circle, and a liquid medium is injected into the cylindrical space formed by the arc D and the arc C. The present invention is used to solve the problem of excessive stress value of the tank wall at the bottom of a large storage tank by changing the composition structure of the tank wall and reducing the diameter. There is no need to increase the strength and thickness of the steel plate of the lower wall of the large storage tank, and the large storage tank can be manufactured with ordinary low-alloy steel plates with small and medium thicknesses.

Description

Technical Field

[0001] The invention belongs to the technical field of large storage tanks, and in particular relates to a large storage tank with a plum blossom-shaped cross section. Background Art

[0002] Large oil storage tanks refer to large containers for storing crude oil or other petroleum products with a capacity of more than 100 cubic meters, which are composed of tank walls, tank tops, tank bottoms and tank accessories. Large oil storage tanks are containers for storing oil products. They are the main equipment of oil depots and are mainly used in refineries, oil fields, oil depots and other industries. The common standard series of arched roof oil tanks in my country are: 100 cubic meters, 200 cubic meters, 300 cubic meters, 500 cubic meters, 700 cubic meters, 1000 cubic meters, 2000 cubic meters, 3000 cubic meters, 5000 cubic meters, 10000 cubic meters, 20000 cubic meters, 30000 cubic meters, 50000 cubic meters, 100000 cubic meters, 120000 cubic meters.

[0003] The current large storage tank has a volume of 150,000 cubic meters, a diameter of about 100 meters, and a height of 21.5 meters. Assuming that the thickness of the bottom of the tank wall is 30 mm, according to the moment-free theory of a rotating shell under internal pressure, the circumferential membrane stress at the bottom of the tank wall is

[0004]

[0005] Obviously, this stress value has exceeded the allowable stress of most conventional materials. Therefore, large storage tanks have to use high-strength steel plates with a yield limit of 490MPa. Assuming that the material is 12MnNiVR, its allowable stress within the design temperature range is 226MPa, then the thickness is

[0006]

[0007] This thickness requires the use of a large plate rolling machine to roll the plate, and the weld is deep, which poses a great challenge to manufacturing. Summary of the invention

[0008] The purpose of the present invention is to provide a large storage tank with a plum blossom-shaped cross-section, which is used to solve the problem of excessive stress value of the tank wall at the bottom of the large storage tank. There is no need to increase the strength and thickness of the steel plate of the lower wall of the large storage tank. The large storage tank can be manufactured with ordinary low-alloy steel plates with small and medium thickness.

[0009] To achieve the above object, the technical solution adopted by the present invention is:

[0010] A large storage tank with a plum blossom-shaped cross section comprises a tank wall, wherein the cross section of the tank wall is plum blossom-shaped.

[0011] Furthermore, the plum blossom shape is formed by connecting a plurality of arcs A opening inwards and arcs C opening outwards, and the connection point between the arcs A and C is tangent.

[0012] Furthermore, the radius of the arc A is greater than the radius of the arc C.

[0013] Furthermore, the arc C extends into an arc D, and the arc D and the arc C form a closed figure.

[0014] Furthermore, the arc D and the arc C form a full circle.

[0015] Furthermore, liquid medium is injected into the cylindrical space formed by the arc D and the arc C.

[0016] Furthermore, the ratio of the radius of the circumscribed circle of the tank wall to the radius of the arc A is k, and k>2.

[0017] Furthermore, the ratio of the cross section of the plum blossom-shaped tank wall to the cross section of its circumscribed circle is k1, and k1>0.85.

[0018] Furthermore, the k is greater than or equal to 3 and less than or equal to 4.

[0019] Furthermore, the height of the arc D is 0.5-0.75 times the height of the tank wall.

[0020] The beneficial effects of the present invention are as follows: the present invention solves the problem of excessive stress value of the tank wall at the bottom of a large storage tank by changing the tank wall composition structure and reducing the diameter. It is not necessary to increase the strength and thickness of the steel plate of the lower wall of the large storage tank, and ordinary low-alloy steel plates with small and medium thicknesses can be used to manufacture the large storage tank. After adopting the structure of the present invention, ordinary low-alloy steel plates with small and medium thicknesses can be used to manufacture large storage tanks, which reduces the difficulty of manufacturing large storage tanks, while greatly reducing the quality of the oil tank and saving investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic cross-sectional view of a large storage tank having a plum blossom-shaped cross-section.

[0022] Figure 2 It is a schematic diagram of the longitudinal section of a large storage tank with a plum blossom-shaped cross section.

[0023] Figure 3 for Figure 1 A partial enlarged schematic diagram of the middle arc.

[0024] In the figure: 1-existing circular tank wall; 2-arc D; 3-arc C; 4-arc A, 5-oil, 6-water. DETAILED DESCRIPTION

[0025] In order to better understand the present invention, the technical solution of the present invention is further described below in conjunction with embodiments and drawings.

[0026] A large storage tank with a plum blossom-shaped cross section comprises a tank wall, wherein the tank wall has a plum blossom-shaped cross section. The plum blossom shape is formed by connecting a plurality of arcs A with openings facing inwards and arcs C with openings facing outwards, wherein the connection points between the arcs A and C are tangent. The radius of the arc A is greater than the radius of the arc C.

[0027] In a preferred embodiment, the arc C extends into an arc D, the arc D and the arc C form a closed figure (such as a full circle), and the cylindrical space formed by the arc D and the arc C is injected with a liquid medium.

[0028] Design principle:

[0029] According to the stress formula described in the background technology, stress is proportional to the diameter and height of the tank wall. The main method to reduce stress is to reduce the diameter and height. The solution proposed by the present invention is: reduce the diameter of the cylinder, arrange multiple smaller arcs with the same diameter along the existing circular tank wall in a circle, and set a smaller arc C between the two small arcs to connect. Under the hydraulic pressure of the oil medium, arc A is subject to internal pressure, and arc C is subject to external pressure. In order to avoid the appearance of external pressure, arc C can be completed into a full circle outside the arc string composed of arcs A and C. This arc segment is called arc D. Liquid medium, such as tap water, is injected into the cylindrical space formed by arcs D and C to resist the hydraulic pressure of the oil, so that arc C is basically not subject to external pressure.

[0030] like Figure 1 As shown, assuming that the radius of the existing circular tank wall (i.e., the circumscribed circle of the plum blossom-shaped tank wall) is r1, the radius of arc A is r2, and the ratio of the two is k. The cross-sectional area of ​​the plum blossom formed by arc A and arc C is smaller than the cross-sectional area of ​​the existing circular tank wall, and the ratio of the two is k1. In order to keep the volume unchanged, the height must be increased. The ratio of the height of this design to that of the existing tank is 1 / k1. Then the medium pressure at the bottom of the tank wall of this design also increases to 1 / k1 times the original. The ratio of the stress at any point on arc A to the stress of the existing design tank is

[0031]

[0032] In the formula, k1>0.85, k>2, it can be seen that the stress energy can be greatly reduced.

[0033] Design parameter determination principles and thickness calculation:

[0034] When designing, k=3~4. The arc material of each section of the lower tank wall plate controlled by strength is Q345R, and the arc material of each section of the upper tank wall plate controlled by stiffness is Q235B. Q235B can be used to complete the arc D. The height of the arc D is (0.5-0.75) times the tank wall height; its radius r3 is reasonably determined by drawing, and its value should be less than r2.

[0035] The thickness of each arc is calculated according to the following formula

[0036]

[0037] In the formula, P is the liquid pressure at the corresponding point.

[0038] The cylindrical oil tank of this cross section can still use the existing sealing technology, or U-shaped membrane sealing technology, and the floating plate can also use the existing technology. The manufacturing and installation methods of the cylindrical oil tank wall of this cross section are basically the same as those of the current oil tank.

[0039] Tank wall forming:

[0040] In order to avoid the longitudinal welds of the upper and lower ring plates being aligned (collinear), the wall panels of arc C can be a whole piece on some ring panels (there can be a spliced ​​longitudinal seam in the middle, and it should also be noted that the longitudinal welds of the upper and lower wall panels are staggered), such as Figure 3 That is, point A and point B are the locations of the longitudinal welds, and the wall panel radius of the entire arc C is r3. The wall panel can also be bent into shape at the installation site.

[0041] On other ring plates, the weld between arc C and arc A must avoid points A and B. Point A becomes point A', point B becomes point B', and the radius of arcs AA' and BB' is r2. Figure 3 . Panel AA'C and panel CBB' have two curvature radii, and the bending directions are opposite. Their butt weld can be selected at point C. Panel AA'C and panel CBB' are bilaterally symmetrical, and their actual shapes are the same. Panel AA'C is divided into two large pieces, and the butt weld is at point H. The HC arc plate is bent on site, while HA' can be pressed and formed in the factory with a hydraulic press. The positions of points A' and H are determined by the following formula.

[0042]

[0043]

[0044] The upper and lower molds can be made of steel plates with higher strength and thickness, and then punched and bent and processed on a planer.

[0045] Embodiment 1

[0046] Take the 150,000 cubic meter oil tank in the background technology as an example.

[0047] Assume r1 = 50 meters, then r2 can be 12.5 meters and r3 can be 3.14 meters.

[0048] The area s of the quincunx cross section consisting of 10 arcs 4 and 10 arcs 3 is

[0049] s=2500×3.14-10×s1=7850-792=7058m 2

[0050] Where s1 is Figure 1 The area of ​​the shaded part in the figure accounts for 89.9% of the original cross-sectional area. To keep the volume unchanged, the height is increased to 1.112 times of the original height. Q345R steel plate is used, and its allowable stress is 189MPa.

[0051]

[0052] It can be seen that the thickness is greatly reduced.

[0053] Figure 1 Points A and B are the theoretical connection points of arc C and arc A. In actual operation, they should be changed appropriately to avoid the situation where the longitudinal joint welds of the upper and lower ring plates overlap (collinearity). It is also necessary to avoid the connection of arc D and arc C at points A and B. The radius of arc D can be appropriately increased, such as increasing it by 500mm, so that the connection points become points D and E.

[0054] The following is a calculation of the change in steel mass between this design and the existing design, considering only the first and second ring plates at the bottom. G1 is the mass of the first ring plate (thickness 43mm) and the second ring plate (thickness 40mm) of the existing design, G2 is the mass of arc A, and G3 is the mass of arc D. The thickness of the first and second ring plates of this design are 15 and 12mm respectively. The height of the ring plate is 2m, and the density of the steel plate is 7.85 tons / m 3 .

[0055] ΔG=G1-(G2+G3)

[0056] G'1=(100+0.043)×3.14×2×0.043×7.85×1000=212072kg

[0057]

[0058] G'2=(339.9+0.015×3.14)×2×0.015×7.85×1000=80057kg

[0059]

[0060] Assume that the thickness of arc D is 8 mm, there are 10 arc D pieces, and the height is 20 meters. Its weight is

[0061] G3=13.383×0.008×20×7.85×1000×10=168090kg

[0062] ΔG=97155kg

[0063] It can be seen that the new oil tank saves considerable steel.

[0064] The above description is only an application embodiment of the present invention, and certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention still fall within the protection scope of the present invention.

Claims

1. A large storage tank with a plum blossom-shaped cross section, comprising a tank wall, characterized in that: The cross section of the tank wall is plum blossom shaped; The plum blossom shape is formed by connecting a plurality of arcs A with openings facing inwards and arcs C with openings facing outwards, and the connection points between the arcs A and C are tangent; The arc C extends into an arc D, the arc D and the arc C form a closed figure, and the arc D and the arc C form a full circle; Liquid medium is injected into the cylindrical space formed by the arc D and the arc C; The ratio of the radius of the circumscribed circle of the tank wall to the radius of the arc A is k, k>2, and the ratio of the cross section of the plum blossom-shaped tank wall to the cross-sectional area of ​​its circumscribed circle is k1, k1>0.

85.

2. A large storage tank with a plum blossom-shaped cross section according to claim 1, characterized in that: The radius of the arc A is greater than the radius of the arc C.

3. A large storage tank with a plum blossom-shaped cross section according to claim 1, characterized in that: The k is greater than or equal to 3 and less than or equal to 4.

4. A large storage tank with a plum blossom-shaped cross section according to claim 1, characterized in that: The height of the arc D is 0.5-0.75 times the height of the tank wall.

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