AU2011100901A4

AU2011100901A4 - Improvements in and relating to Fuel Tanks

Info

Publication number: AU2011100901A4
Application number: AU2011100901A
Authority: AU
Inventors: Stephen John Bain; Jeff Brook
Original assignee: Advanced Fuel Tanks Ltd
Current assignee: Fuelchief Ltd
Priority date: 2010-07-23
Filing date: 2011-07-21
Publication date: 2011-09-01
Anticipated expiration: 2019-07-21
Also published as: WO2012011823A1; US20130213969A1

Abstract

The present invention relates to improvements in and relating to fuel tanks such as bunded fuel storage tanks. This invention provides a bunded tank including inner and outer walls, which, when the tank is viewed in transverse cross-section, define a substantially rectangular shape (SRS) wherein each inner or outer wall has an at least partially convex profile. The adjacent sides of the inner and/or outer walls are connected by rounded corners, and the inner and outer walls are arranged with respect to one another to create an inner tank and an outer tank. C) 0 "'TU CAo tL

Description

Improvements in and Relating to Fuel Tanks STATEMENT OF CORRESPONDING APPLICATIONS This application is based on the Provisional specification filed in relation to Australian Patent Application Number 2010903302, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to improvements in and relating to fuel tanks. More specifically to improvements in bunded fuel storage tanks. BACKGROUND ART A large number of styles and configurations of fuel tanks exist. One requirement of fuel tanks is that they include an outer wall, or enclosure, to capture spillage in the event of rupture or leaking from an inner enclosure. This encapsulation is referred to in the industry as bunding. It should be understood that bunding does not involve complete encapsulation of an inner enclosure, rather the outer enclosure should be capable of capturing any spilt fluid. For example, a bunded enclosure could comprise a single layer inner tank, around which is built a walled and open topped structure, such as a surrounding wall. The size and/or shape of a tank can be dictated by a number of different criteria depending upon where the tank is to be located, or whether it is to be built in situ, or transported to its final location. Tanks which require transporting, whilst not restricted to any particular shape or configuration, are typically kept within the bounds of a standard shipping container's dimensions. The reason for this limitation is to allow both ease of transport on a standard container transport or (vessel or vehicle) and also to minimise costs. Transportation of freight is typically based on containerised rates, or the volumetric equivalence of a standard rectangular shipping crate. There are five common standard lengths of container, 20-ft (6.1 m), 40-ft (12.2 m), 45-ft (13.7 m), 48-ft (14.6 m), and 53-ft (16.2 m ), container width is standard across all lengths, at 8-ft (2.44m). 1 In order to maintain structural integrity (rigidity) of a tank in: " an empty form; " a transport ready form; and " a fully laden fuel storage state, the fuel tank body is either shaped to provide the required structural integrity, or external or internal reinforcement is added to the tank to provide additional strength. Both methods of adding external, or internal, reinforcement and/or configuring the shape of the tank, result in significant loss in capacity of the tank. This can best be explained with reference to the following prior art tank embodiments. Rectangular Tanks with External or Internal Reinforcing: It will be appreciated by a person skilled in the art of engineering that any weight applied to the centre of a flat sheet will result in a force acting to pull the sheet in on itself, or conversely bulge outward if the flat sided tank is subjected to an internal pressure such as from fuel stored therein. Due to these structural limitations, flat sided tanks require substantial reinforcing to provide the requisite strength. If the tank is limited to the dimensions of a containerised footprint, the dimensions of any external, or internal, reinforcing will subtract from the available capacity of the tank. A further disadvantage of flat walled fuel tanks is the tendency for water and debris to pool or collect on the top of the tank. This is undesirable as it can result in corrosion and premature failure of the tank, resulting in contamination and further cost. Round or Oval Tank Shapes: Both round and oval tanks provide substantial advantages over rectangular tanks in terms of structural integrity and also in the ability to naturally shed any water or debris from the tank. However these advantages come at the expense of capacity. Per unit volume a round tank is poor value when compared to rectangular tanks with respect to the same containerised volumetric area. All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country. 2 Throughout this specification, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. DISCLOSURE OF THE INVENTION According to one aspect of the present invention there is provided a bunded tank which includes inner and outer walls ("the walls"), wherein the inner and outer walls, when the tank is viewed in transverse cross-section, define a substantially rectangular shape (SRS) wherein each inner or outer wall has an at least partially convex profile, wherein adjacent sides of the inner and/or outer walls are connected by rounded corners, and wherein the inner and outer walls are arranged with respect to one another to create an inner tank and an outer tank. As used herein the term 'wall' refers to a material layer or surface which forms a barrier. A wall may be configured as a continuous surface which may enclose a space. Preferably the inner and outer walls of the bunded tank may each respectively have a cross sectional profile which includes two lines of symmetry. In especially preferred embodiments the two lines of symmetry are a vertical line of symmetry and a horizontal line of symmetry. It will be appreciated that the outer tank shares at least one wall with the inner tank, therefore the respective symmetry of the inner and outer tank should be understood to each include the shared inner/outer wall. Collectively the inner and outer wall share a single line of symmetry which, in preferred embodiments, is a vertical line. Bunded tanks are known in the art of hazardous liquid storage as being any tank having a inner and an outer wall. The inner wall defines the area of the tank that contains the stored liquid. The outer wall provides redundancy in the event that the inner wall becomes damaged or otherwise fails to contain the liquid therein. In the present invention the inner and outer walls are adjacent each other and may be in direct contact, or separated by a gap, or separated by 3 insulation, between the inner and outer walls. In preferred embodiments the inner wall is formed from steel. However the inner wall may be any suitably corrosion resistant material. In some embodiments the inner wall may be impervious to the fluid contained therein, but may provide no structural support, for example a bladder. In some embodiments the inner wall may be a coating on the inside of the outer wall. In some preferred embodiments the inner wall is of a seamless construction. In other preferred embodiments the inner wall may be identical in structure to the outer wall. In preferred embodiments the outer wall is formed from steel. In other embodiments the outer wall may be a composite material In preferred embodiments the outer wall is made by way of one or more sections, such as: * at least one centre section; and * at least two end cap sections. It will be appreciated that the SRS of the outer wall forming the bunded tank provides a single integrated structure capable of substantially maintaining its shape during transportation and storage of fluid therein. In preferred embodiments the SRS outer wall is substantially monocoque. In some preferred embodiments the tank may include one or more plug welds or other joins between the inner and outer walls at one or more locations along the length of the tank. This is particularly advantageous for embodiments which are 12.2m or greater in length. The plug welds prevent the inner walls from bulging under pressure and making contact with the outer walls. In preferred embodiments the end caps of the tank include a partial outwardly convex curved profile. In preferred embodiments the tank includes isoblock connectors or the like on the lower side of the tank. In preferred embodiments the isoblock connectors or the like are located symmetrically on the bottom of the tank. In some preferred embodiments isoblock connectors or the like are located on the upper side of the tank. 4 In preferred embodiments the isoblock connectors are located on the outer comers of the tank. It will be appreciated that the isoblock connectors provide a connection point to which lifting chains or strops can be attached. A person skilled in the art would understand that the isoblock connection points will be positioned evenly about the centre of gravity of the tank; such that the tank is evenly supported when being lifted at the isoblock connection points. In preferred embodiments the isoblock connectors are located at the ends of the tank. However it will be apparent to a person skilled in the art that the isoblock connectors could be located at any position on the tank that allows balanced lifting of the tank. In some preferred embodiments the tank includes one or more lower support members. In one preferred embodiment lower support members are in the form of two parallel supports substantially running the length of the tank. In some preferred embodiments the lower support members comprise a plurality of supports running in either a longitudinal direction, a transverse direction or a combination of longitudinal and transverse directions. The configuration of the lower support members should therefore not be seen as being limiting. The purpose of the lower support members is to distribute the weight of the tank and the tanks contents into a support platform such as the ground or a concrete slab. It will be apparent to a person skilled in the art that: " the number of supports; " the spacing of the supports; and " the shape or configuration of the supports, will be defined by: * the resiliency of the tank structure; and * the resiliency of the support platform. In preferred embodiments the isoblock connectors may be integral with the lower support members.. In other embodiments the isoblock connectors may be attached to the tank by way of support struts or the like. According to another aspect of the present invention there is provided a method of constructing a bunded fuel tank having inner and outer walls, wherein each inner or outer wall has an at least partially convex profile; and wherein adjacent sides of the inner and/or outer walls are connected by rounded comers, and 5 wherein the inner and outer walls are arranged with respect to one another to create an inner tank and an outer tank, the method including the steps of: a) pre-forming one or more standard sheets of material into one or more SRS sections for the inner walls; b) forming one or more standard sheets of material into end caps for the inner wall; c) pre-forming one or more standard sheets of material into one or more SRS sections for the outer wall; d) forming one or more standard sheets of material into end caps for the outer wall; e) joining the one or more SRS sections forming the inner wall together to form a single inner SRS tube; f) joining the one or more SRS sections forming the outer wall together to form a single outer SRS tube forming an enclosure about at least a section of the inner SRS tube; g) joining the end caps for the inner wall to the inner SRS tube; h) joining the end caps for the outer wall to the outer SRS tube; and i) joining the one or more lower support members and integrated isoblock connectors to the lower surface of the SRS tank. In preferred embodiments the section of the inner tank that is enclosed by the outer SRS tube in method step f) comprises substantially three sides and both ends of the inner SRS tube. In preferred embodiments the method of constructing a fuel tank includes the further step j) wherein one or more apertures are cut through the section of the inner SRS tube that is not enclosed by the outer SRS tube. It is preferred not to cut through both the outer and inner SRS layers as this would result in introduction of a weakness in the bund. Therefore access to the tank contents is typically configured through access ports cut in the upper surface of the tank. In preferred embodiments the side of the inner SRS layer that is not enclosed by the outer SRS tube is the upper surface of the tank. In preferred embodiments the sheet material is steel. In preferred embodiments the sheets of steel are joined by welding. According to another aspect of the present invention there is provided a bunded tank substantially as described above wherein the tank includes at least two longitudinally extending support structures on the underside of the floor region. 6 Preferred embodiments of the bunded tank substantially as described above may have one or more of the following advantages: * the tank is self supporting whether it is filled, or not filled, with liquid; " the tank is capable of having isoblock connection points attached to the top of the tank and upon the support structures which may allow the tanks to be more easily handled for shipping and transportation purposes; * the dimensions and SRS of the tank provides comparable volumetric capacity to a standard shipping container; " the configuration of the tank provides a high volume, aesthetic relocatable, fuel tank; and * the tank may be permanently sited as the convex sides and top do not allow water and debris to collect on the tank. BRIEF DESCRIPTION OF DRAWINGS Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which: Figure Ia an isometric drawing showing a bunded tank according to one preferred embodiment of the present invention; Figure 1b shows a transverse cross section of the bunded tank of Figure 1a; Figure 2a an isometric drawing showing the inner wall middle section of the bunded tank shown in Figure 1 a; Figure 2b an isometric drawing showing the inner wall end section of the bunded tank shown in Figure ia; Figure 2c an isometric drawing showing the inner wall end cap of the bunded tank shown in Figure 1a; Figure 3a an isometric drawing showing the outer wall middle section of the bunded tank shown in Figure 1a; Figure 3b an isometric drawing showing the outer wall end section of the bunded tank shown in Figure 1a; 7 Figure 3c an isometric drawing showing the outer wall end cap of the bunded tank shown in Figure 1a; Figure 4 an isometric view of an inner tank of the bunded tank shown in Figure 1a; Figure 5 an isometric view of an outer tank of the bunded tank of Figure 1a; and Figure 6 shows a further embodiment of a bunded tank. BEST MODES FOR CARRYING OUT THE INVENTION With respect to Figures la, lb and 6 there is shown a bunded tank, as generally indicated by arrow 1. The bunded tank 1 has an inner steel sheet wall 2 (of which only the top is visible) and an outer steel sheet wall 3. The relationship of the inner wall 2 and the outer wall 3 are illustrated in the transverse cross-sectional profile of Figure 1 b, wherein the inner wall 2 is enclosed by the outer wall 3 on substantially three sides. The uppermost surface 202 of the inner wall 2 forms both an inner wall 2 and at least a portion of an outer wall 3 of the tank. With respect to Figures 2a - 2c the various components which make up the inner wall 2 are shown. The inner wall 2 of the tank 1 has 3 SRS sections in the form of strakes, shown in Figures 2a - 2c which include: * an inner wall middle section 2a; and " a first and second inner wall end sections 2b. The inner wall 2 also includes two end caps 2c. The orientation in which inner wall 2, sections 2a, 2b and 2c are connected together is shown in Figure 4. It will be appreciated that the inner wall 2 sections could be attached to one another in a number of ways without departing from the scope of the invention. However, in the embodiment shown the sections are welded together. The inner wall 2 of Figure 4 also includes an access port in the top surface thereof over which is bolted a hatch plate 100. Also visible shown in Figure 4 are overhanging lips 101 found in inner wall end sections 2b. With respect to Figures 3a - 3c the various components which make up one portion of the outer wall 3 are shown. It will be appreciated that the uppermost surface 202 of the inner wall 2 also forms part of the outer wall. However, for the purposes of clarity the outer wall is described only in terms of the components that only comprise outer walls. The outer wall 3 of the tank includes 3 SRS sections in the form of strakes, shown in Figures 3a - 3c which comprise: * an outer wall middle section 3a; and 8 * a first and second outer wall end sections 3b. The outer wall 3 also includes two end caps 3c. The manner in which outer wall 3, sections 3a and 3b are connected together is shown in Figure 5. It will be apparent to a person skilled in the art that the open tub shape excluding the inner tank 2 as depicted in Figure 5 would never exist in reality as the inner tank would always be located inside the outer tank 3 prior to completion of welding. It will be appreciated that the outer wall sections could be attached to one another in a number of ways without departing from the scope of the invention. However in the embodiment shown the sections are welded together. Further to the welding of the individual sections of the inner 2 and outer 3 walls of the tank 1, the upper most surface 202 of the inner wall 2 is welded to the outer wall 3 along the edges 201 of the open top of the tub shape shown in Figure 5. It will be appreciated that the inner tank 2 shown in Figure 4 fits entirely within the outer open topped tank of Figure 5 and welding in this manner effectively suspends the inner tank 2 within the outer tank 3. This is illustrated in the transverse cross section of Figure 1b where a gap 200 can be seen between substantially 3 sides of the inner 2 and outer 3 walls of the tank 1. Whilst not shown in the drawings, it will be appreciated that a similar gap will exist between the inner end wall 2c and outer end wall 3c of the tank. Because the inner end walls 2c are spaced apart from the outer end walls 3c, if an overhanging lip 101, or the like, is not included a gap will be left at the top of the tank between the inner 2c and outer 3c end walls. Thus the lips 101 both cover the gap that would otherwise be left and also provide a greater weld area by which to attach the inner 2c and outer 3c tanks. As most clearly shown in the transverse cross section of Figure 1 b, the body of the tank 1 is substantially rectangular in form, bounded by four distinct sides 4, each opposed side 4 of the inner 2 and outer 3 walls is further defined by a partial convex curved profile 4a. Adjacent sides 4 of the inner 2 and outer 3 walls are connected by rounded comers 4b along adjacent edges 4c of the partial convex curved profile 4a. The tank 1 is constructed in a number of SRS tube sections. For the purposes of clarity, the tank 1 has been described in terms of one preferred length only, comprising 3 SRS tube sections. It will be apparent to a person skilled in the art that the length of the tank 1 can be altered by using more or less of the SRS tube sections. As shown in Figures 1 and 6, the tank 1 also includes longitudinally extending support structures 7 welded to the bottom of the tank 1. The longitudinally extending support structures 7 include integrated isoblock connection points 8, of which only 3 are visible. Figure Ia shows an embodiment in which welded to the upper surface of the tank 1 are support struts 10, into which upper isoblock connectors 9, are integrated. 9 Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims. 10

Claims

1. A bunded tank including inner and outer walls which are at least partially convex in profile and when viewed in transverse cross-section, define a substantially rectangular shape.

2. The bunded tank of claim 1 wherein adjacent sides of the inner and/or the outer walls are connected by rounded corners

3. The bunded tank of any one of the preceding claims wherein the outer wall is substantially monocoque.

4. The bunded tank of any one of the preceding claims including end caps having an at least partially convex profile.

5. The bunded tank of any one of the preceding claims including lower support members in the form of two parallel supports running substantially the length of the tank. 11