Multicylinder Tanks

Abstract

A tank having an outer wall comprising a plurality of intersecting vertical cylindrical segments joined together at the intersection and arranged with their concave surfaces facing inwardly. Webs joined to junctures of the cylindrical segments and extending across the tank to other junctures carry a part of the outward force applied to the outer wall by liquids stored in the tank.

Description

This invention relates to the storage of liquids and more particularly to storage tanks of large capacity for storing liquids at atmospheric pressure.

The increased consumption of petroleum products has made necessary terminals of large capacity. Formerly the terminals consisted of a large number of relatively small flat-bottomed, vertical cylindrical tanks of about 50,000 barrels each. The term "vertical cylindrical" is used to designate tanks of cylindrical shape with the axis of the cylinder vertical. As a safety measure, firewalls are constructed around each of the tanks to prevent flow of burning hydrocarbons from one tank to another if petroleum products in one tank should start burning. The firewalls add substantially to the area required for each tank.

To reduce the space requirements for terminals, the size of the individual tanks has been increased, and at present vertical cylindrical tanks having a capacity as high as approximately 1,000,000 barrels have been constructed. Such tanks have a diameter of approximately 300 feet and a height of the order of 80 feet. The head of liquid in such a tank and the large diameter of the tank have made it necessary for bottom rings of the tank to be as thick as 3 inches to withstand the resulting tensile stresses in the tank wall. The handling of 3-inch steel plate and the welding of plate of such thickness on site during the construction of the tank cause the cylindrical tanks of large capacity to be very expensive.

Recently tankers having a capacity larger than 2,000,000 barrels have come into use. Those tankers are equipped with high-capacity pumps capable of pumping oil at a rate approaching 100,000 barrels per hour. Because of the high pumping rate, tanks of increased capacity are desired to reduce the frequency of switching from one tank to another during the unloading operation, and thereby to reduce the danger of spills.

This invention resides in flat-bottom storage tanks of large capacity adapted to store liquids at atmospheric pressure in which a plurality of vertical cylindrical segments arranged concave inwardly are welded to the bottom and to one another along elements of the cylinders to form the sidewalls of the tank. Webs joined to opposing junctures of cylindrical segments extend across the tank. The webs bear a portion of the tensile stress that would otherwise be borne entirely by the wall of the tank and also provide a support for the tank roof. An important advantage of the tanks of this invention is the flexibility in the shape and size of the tank which allows efficient use of the space available at a terminal.

In the drawings:

FIG. 1 is a horizontal sectional view along section line I--I in FIG. 2 of a tank constructed in accordance with this invention.

FIG. 2 is a vertical sectional view along section line II--II in FIG. 1 of the embodiment of the invention illustrated in FIG. 1.

FIG. 3 is a plan view of a storage tank, with the top removed, illustrating this invention in a multicylinder tank of large capacity.

FIG. 4 is a plan view similar to FIG. 3 of another embodiment of this invention.

FIG. 5 is a plan view similar to FIG. 3 of an L-shaped tank utilizing this invention.

Referring to FIG. 1, a tank indicated generally by reference numeral 10 has four vertical cylindrical segments 12a, 12b, 12c and 12d welded to one another along elements of the cylinders at their lateral edges to form the sidewall of the tank extending for the full periphery of the tank. The cylindrical segments are welded at their lower end to the bottom of the tank and are arranged with their concave surfaces facing inwardly. Cylindrical segments 12a and 12b are welded along elements at juncture 14, 12b and 12c are welded at juncture 16, 12c and 12d are welded at juncture 18, and 12d and 12a are welded at juncture 20.

Welded to cylindrical segments 12a and 12b at juncture 14 is a web 22 which extends across the tank 10 to juncture 18 where web 22 is welded to cylindrical segments 12c and 12d. A similar web 24 is welded at juncture 20 to cylindrical segments 12a and 12d and extends across the tank 10 to juncture 16 where it is welded to segments 12b and 12c. In the manufacture of the tank it is contemplated that the webs 22 and 24 will be erected on the bottom of the tank and the weld at each juncture made to join the cylindrical segments and the webs simultaneously. In actual construction, web 24 will consist of two parts. One part will extend from juncture 20 to the midpoint of web 22 and the other from that midpoint to juncture 16.

As shown in FIG. 2 it is contemplated that the tank walls will be constructed of a series of horizontal bands such as bands 26, 28, 30 and 32. In accordance with conventional practice, the thickness of the bands is largest near the bottom of the tank and decreases toward the top of the tank. Similarly, the webs may be constructed of a series of strips 34, 36, 38, and 40 of successively decreasing thickness. As shown in FIG. 2, the webs have openings 42 near their bottom to permit flow from one portion of the tank to another.

In the tank illustrated in FIGS. 1 and 2, the cylindrical segments 12a, 12b, 12c and 12d should include an arc exceeding 90.degree.. It is preferred that the arc of each of the cylindrical segments be in the range of 110.degree. to 160.degree.. With that arrangement the radius of each of the cylindrical segments is smaller than the radius of a cylinder having the same cross-sectional area as the tank 10. The small radius contributes to the rigidity of the tank and permits more effective use of the space at the terminal because the shape of the tank is more nearly square than is a circle. With the arcs of the cylindrical segments being in the range of 110.degree. to 160.degree., the internal angle between the webs and the tank walls exceeds 90.degree. .

In the embodiment of the invention illustrated in FIG. 3, a tank 50 has corner cylindrical segments 46a, 46b, 46c and 46d welded to the bottom 47 at each of the "corners" of the tank which is of an overall generally rectangular shape. The space between the lateral edges of the corner cylindrical segments is closed by linearly aligned series 48a, 48b, 48c and 48d of widening cylindrical segments 49a, 49b, 49c, and 49d, respectively. Each of the corner cylindrical segments 46a, 46b, 46c, and 46d is welded along the element of the cylinder at each of its lateral edges to the lateral edge of the end widening strip in a series to form junctures 50. Each of the widening strips is welded to the adjacent widening strip in the series to form junctures 52. Webs 54a extend across the tank from juncture 50 to an opposite juncture 50, and webs 54b extend across the tank from a juncture 52 to an opposite juncture 52. As in the embodiment of the invention illustrated in FIG. 2, it is contemplated that the web structure illustrated in FIG. 3 will be constructed on the bottom 47 of the tank, and the joining of the web and the cylindrical segments at each juncture will be made simultaneously. As shown in FIG. 3, all of the cylindrical elements 46 and 49 are arranged with their concave surfaces facing inwardly to form tank sidewalls of lobular shape.

In the embodiment of the invention illustrated in FIG. 3, the corner cylindrical segments 46a, 46b, 46c and 46d preferably include an arc in the range of 110.degree. to 180.degree.. The arc included by the widening strips 49a, 49b, 49c, and 49d, etc., is preferably equal to the number of degrees the corner segments exceed 90.degree. and the radius of curvature of the widening segments is the same as the radius of curvature of the corner segments to give a structure in which the widening cylindrical segments and the corner cylindrical segments have a common tangent. The embodiment of the invention illustrated in FIG. 3 has been shown for a tank of rectangular shape. This invention is advantageous in allowing flexibility in the shape of the tank to allow the tank to fit the site available.

In the storage tank indicated generally by reference numeral 56 illustrated in FIG. 4, a plurality of cylindrical segments 58 are arranged to extend vertically upward from a tank bottom 60. The cylindrical segments 58 are in linear alignment and are joined along an element of the cylinders. Similarly, cylindrical segments 62 are arranged in linear alignment at right angles to the alignment of the cylinders 58 and are welded one to another along their vertical edges. Cylindrical segments 64 are arranged parallel to and spaced from segments 58 and are welded one to another along their vertical edges. Another series of vertical cylindrical segments 66 are arranged in linear alignment parallel to cylindrical segments 62 and are welded one to another along an element in their vertical edges. The free ends of the four series of cylindrical segments are welded together at junctures 68, 70, 72 and 74 to form the completed sidewalls of the tank.

Webs 76 extend across the tank from the junctures 78 of the cylindrical elements 58 to the junctures 80 of the cylindrical elements 64. Similarly, webs 82 extend across the tank and are joined to cylindrical elements 66 at junctures 84 and to cylindrical elements 62 at elements 86. Webs 85 extend diagonally inward from junctures 68, 70, 72, and 74 and are connected to junctures of webs 78 and 82. Webs 76, 82 and 85 and the sidewalls provide support for a roof, not shown in the drawing. The embodiment of the invention illustrated in FIG. 4 is composed of a plurality of cylindrical segments, all of which include an arc of 180.degree.. Since all of the cylindrical segments in the tank illustrated in FIG. 4 are identical, fabrication and erection of the tank is simplified. It will be noted that the tank illustrated in FIG. 4 is of generally rectangular shape but that the corners consist of two cylindrical segments rather than a single cylindrical segment as shown in the embodiment illustrated in FIG. 3.

In the embodiment illustrated in FIG. 5, an L-shaped tank indicated generally by reference numeral 90 is illustrated with corner cylindrical segments 92 at each of the external corners of the tank. The term "external corners" is used to to denote corners at which the external angle of the sidewalls meeting at the corner exceeds 180.degree.. No corner cylindrical element is required at the internal corner at which the two legs of the ell meet. Each of the lateral edges is welded to a series of vertical linearly aligned cylindrical segments 94 welded together to form the sidewalls of the tank. Webs 96 extend across the tank and are connected to the junctures of the cylindrical segments.

The storage tank constructed in accordance with this invention is useful for tanks having a capacity exceeding 500,000 barrels and is particularly advantageous in providing a tank having a capacity in excess of 1,000,000 barrels. Tanks can be constructed using the concept of this invention of unlimited size without excessive wall thicknesses at the lower portion of the tank. Although steel is required for the webs extending across the tank, the webs carry part of the tensile load carried entirely by the tank wall in single cylinder tanks and permit reduction in wall thickness of the tank. Thus, the tank structure requires no more steel than single cylinder tanks and avoids the very thick, difficult to handle wall sections required by vertical single cylinder tanks of large capacity.

An important advantage of this invention is the saving in space at a terminal site required for the storage tanks. The generally rectangular or square shape of the tanks and the very large size of the tanks allow the tanks to occupy a higher percentage of the space within the firewalls. The large tanks constructed according to this invention reduce the amount of switching from one tank to another during the loading of a tanker and thereby reduce the danger of spill or overflowing of tanks.

Claims

I claim:

1. A tank having a capacity of at least 500,000 barrels for the storage of liquid at atmospheric pressure comprising a flat bottom of generally overall polygonal shape with each side substantially perpendicular to sides adjacent thereto, a vertically extending corner cylindrical segment having a circular arcuate-shaped horizontal cross section of 110.degree. to 160.degree. welded to the bottom at each external corner thereof and extending upwardly therefrom, said corner cylindrical segments being arranged concave inwardly, a plurality of series of vertically extending cylindrical segments of circular arcuate-shaped horizontal cross section with the same radius of curvature as that of the corner cylindrical segments and including the number of degrees by which the corner cylindrical segments each exceed 90.degree. welded together in linear alignment along the edge elements thereof and welded to the bottom of the tank to form the sidewalls of the tank with the cylindrical segments concave inwardly, each of said series being welded to a vertical edge of one corner cylindrical segment and extending to and welded to the nearest vertical edge of an adjacent corner cylindrical segment, a single web secured at each juncture of the cylindrical segments and extending inwardly across the tank to a juncture of cylindrical segments in the opposite sidewall of the tank, and a roof supported over the tank by the upper ends of webs.

2. A tank as set forth in claim 1 in which the tank is of general overall rectangular shape in horizontal section.

3. A tank having a capacity of at least 500,000 barrels for the storage of liquid at atmospheric pressure comprising a flat bottom of L-shape with each side substantially perpendicular to sides adjacent thereto, a vertically extending cylindrical segment having a circular arcuate-shaped horizontal cross section welded to the bottom at each external corner thereof and extending upwardly therefrom, said corner cylindrical segments being arranged concave inwardly, a plurality of series of vertically extending cylindrical segments of circular arcuate-shaped horizontal cross section welded together in linear alignment along the edge elements thereof and welded to the bottom of the tank to form the sidewalls of the tank with the cylindrical segments concave inwardly, each of said series being welded to a vertical edge of one corner cylindrical segment and extending to and welded to the nearest vertical edge of an adjacent corner cylindrical segment, a single web secured at each juncture of the cylindrical segments and extending inwardly across the tank to a juncture of cylindrical segments in the opposite sidewall of the tank, two cylindrical elements of two of the series of cylindrical elements being joined together at the internal angle of the L, and a web from this juncture at the internal angle joins and extends inwardly to another web, and a roof supported over the tank by the upper ends of the webs.