Regulation 3.2 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR AN INNOVATION PATENT ORIGINAL Name of Applicant: Fabtech SA Pty Ltd Actual Inventors: Mark Bennett Rommell Dumlao Graham Fairhead Alexander D Gersch Address for Service: C/- MADDERNS, GPO Box 2752, Adelaide, South Australia, Australia Invention title: A FLUID STORAGE TANK The following statement is a full description of this invention, including the best method of performing it known to us.
FIELD OF THE INVENTION This invention relates generally to a fluid storage tank for storing large volumes of fluid (particularly liquid) above a ground or floor level. For the purpose of explanation, reference 5 will be made to use of the tank in relation to storing water associated with the exploration for and extraction of natural resources, although the tank according to the present invention is not so limited in its application. The exploration and extraction of natural resources frequently requires the containment of 10 large volumes of water. For example, during the extraction of coal seam gas, some 'produced' water is extracted from the wells with the gas and this is sent via pipes to sealed water storage reservoirs to be stored. Reverse osmosis technology can then be used to treat the water and make it suitable for a variety of uses. 15 Different types of large capacity reservoirs suitable for these purposes include clay lined basins or dams, geomembrane lined basins or dams, and industrial steel and concrete tanks. Clay lined basins or dams and geomembrane lined basins or dams are generally permanent (in as much as they are not temporary) installations, and require extensive earthworks. Clay 20 lined basins or dams are also prone to seepage losses. Industrial steel and concrete tanks are limited in size (by hoop stress), require extensive earthworks and concrete footings, are prone to wind loadings when empty due to their height, are generally permanent (i.e. not temporary) structures, and are expensive to build. 25 When exploration and extraction processes have been completed, it is often a requirement that the land be remediated. In the case of known sealed water storage reservoirs, remediating the land where the reservoir was located, if possible, can be very costly. 30 It is an object of the present invention therefore to provide a fluid storage means that ameliorates one or more of the above stated difficulties, or which at the least provides the public with a useful alternative to known means. Other objects and advantages of the present invention will become apparent from the 35 following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed. 2 SUMMARY OF THE INVENTION In one aspect of this invention there is proposed a fluid storage tank for storing fluid above a 5 ground or floor level, the storage tank comprising a side wall defining shell extending around the perimeter of the storage tank, a fluid holding liner for the shell, and a shell supporting framework extending around the outside of the shell wall. In one form, the tank is circular, and the shell supporting framework encircles the shell wall. 10 In one form, the shell supporting framework comprises a plurality of spaced apart uprights, and at least one structural tie extending between each pair of adjacent uprights. In one form, there are at least three structural ties extending between each pair of adjacent 15 uprights, a first extending between the upper ends of the uprights, a second extending between the lower ends of the uprights, and a third extending between the uprights at a position between the first and second structural ties. In one form, each upright forms part of an A-frame having a concrete footing. 20 In one form, the tank comprises leak indication means comprising a secondary liner around the first, primary liner, the secondary liner having an outlet, and a fluid conduit extending from the outlet to a point outside of the tank, wherein in use, fluid exiting the fluid conduit is an indication of a leak in the primary liner. 25 In one form, the tank has a side wall of a height h above the ground or floor level, a distance d between opposing side wall portions, and a h/d ratio of less than 1/15. In a further aspect, the invention may be said to reside in a fluid storage tank for storing fluid 30 above a ground or floor level, the storage tank comprising a side wall defining shell extending around the perimeter of the storage tank, a fluid holding liner for the shell, a shell supporting framework, a secondary liner extending around the first, primary liner, the secondary liner having an outlet, and a fluid conduit extending from the outlet to a point outside of the tank, wherein in use, fluid exiting the fluid conduit is an indication of a leak in the primary liner. 35 3 In a further aspect, the invention may be said to reside in a fluid storage tank for storing fluid above a ground or floor level, the storage tank comprising a side wall defining shell extending around the perimeter of the storage tank, a fluid holding liner for the shell, and a shell supporting framework, wherein the tank has a side wall of a height h above the ground or 5 floor level, a distance d between opposing side wall portions, and a h/d ratio of less than 1/15. In a further aspect, the invention may be said to reside in a method for constructing the above described tank, the method including the steps of constructing the shell supporting framework, fitting the shell inside of the shell supporting framework, and then fitting the liner 10 inside of the shell. In a further aspect, the invention may be said to reside in a leak detection system for a tank having a primary fluid holding liner, the system comprising a secondary liner around the primary liner, the secondary liner having an outlet, and a fluid conduit extending from the 15 outlet to an inspection point outside of the tank, wherein in use, fluid exiting the fluid conduit is an indication of a leak in the primary liner. BRIEF DESCRIPTION OF THE DRAWINGS 20 For a better understanding of this disclosure it will now be described with respect to an exemplary embodiment which shall be described herein with the assistance of drawings wherein: Figure I is a schematic, cross-sectional view through a fluid storage tank according to the 25 exemplary embodiment; Figure 2 is a perspective, detail view of a portion of the fluid storage tank illustrated in Figure I; 30 Figure 3 is a plan view of the fluid storage tank of Figures 2 and 3 (note any dimensions included in the illustrations or this specification are indicative only, and should not be construed as limiting); and Figure 4 is a detailed side view of a typical A-frame for the shell supporting framework of the 35 tank illustrated in Figures I through 3. 4 In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION OF THE INVENTION 5 Referring now to Figures 1 through 4, where an exemplary embodiment of a fluid storage tank I is illustrated. With reference to Figure 1, it can be seen that the fluid storage tank I comprises a side wall 10 defining shell 2 extending around the perimeter of the storage tank 1, a fluid holding liner 4 for the shell 2, and a shell supporting framework 10 extending around the outside of the shell 2. The tank I may be constructed atop a graded earth floor 20, so the requesite earthworks for 15 tank I are significantly less extensive than those required for clay lined basins or dams and geomembrane lined basins or dams for instance. This further aids remediation of the land on which the tank I sits. In this embodiment, the tank I has a height (h) of 1.4 m and a diameter (d) of 60 m. As a 20 result, a shell supporting framework 10 is required, which, comprises a plurality of spaced apart, structural steel A-frame assemblies arranged into the perimeter shape of the tank I (which is circular in this exemplary embodiment). Each A-frame assembly A is bolted to a reinforced concrete footing 30 and comprises an inwardly positioned steel upright 12 that is as high as the side wall to the tank and which is, in use, braced by the remainder of the A 25 frame assembly. With reference to Figures 2 through 4, it can be seen that three structural steel ties 14 extend between each pair of adjacent uprights 12. A first tie 14a extends between the upper ends of the uprights 12, a second tie 14b extends between the lower ends of the uprights 12, and a 30 third tie 14c extends between the uprights 12 at a position between the first and second structural ties. In the case of the circular tank I illustrated, these structural steel ties 14 are slightly curved so as to form an 'arc' portion of the tank's 1 circumference. The side wall defining shell 2 of corrugated and galvanised (or painted/coated) steel sheeting 35 is fixed to the inside of the shell supporting framework 10 with the corrugations running up 5 and down (see Figure 2). In this way the shell supporting framework 10 encircles, and so fully supports the shell 2 when the primary liner 4 for the tank is filled. A geotextile cushion layer 40 (see Figure 1) of woven or non woven polyolefin or natural 5 filaments, bound, woven or formed together in such a manner as to form a sheet, is laid atop the graded earth floor 20. A primary fluid holding liner 4 of polyolefin film or a sheet, lines the shell 2 and is protected from the ground surface 20 by the geotextile cushion layer 40. The Liner can be made from 10 HDPE, LDPE, LLDPE, VLDPE, PVC, CSPE, polypropylene, nylon and blends or alloys of these materials. With reference to Figure 1, it can be seen that the tank comprises leak indication means 50. These means 50 comprise a secondary liner 52 around the first, primary liner 4 (i.e. between 15 the primary liner 4 and the shell 2 and geotextile cushion layer 40). The second liner 52 has an outlet 54, and a pipe 56 extending from the outlet 54 and beneath the concrete footings 30 to a point outside of the tank 1. This way, in use, fluid exiting the pipe 56 is an indication of a leak in the primary liner 4. The pipe 56 can be closed of, and a repair to liner 4 can be scheduled for a convenient time. 20 Where a plurality of spaced apart leak indication means 50 are employed, these can indicate in what part of liner 4 the leak is located. What is more, the pipe or pipes 56 can be sealed so that the secondary liner 52 retains the fluid until such time as a repair to liner 4 can be effected. 25 Advantages of the fluid storage tank according to the present invention include: " Low wall height of 1.4m so low visual impact and low vulnerability to winds; " No need for working at heights during installation; 30 " Modular design permits construction of tanks of varying diameter & capacity; * Double liner system provides leak detection and leak containment within the tank; 35 0 Minimal earthworks are required; 6 * Relatively short lead times to put a tank into service; * Tanks may be provided as a kit of parts; 5 e Ease of assembly, disassembly means a given tank can be disassembled and moved to a new location, where it is re-assembled and re-used; and * Relatively low environmental impact (so ease of remediation) and minimal permitting requirements. 10 It will be understood that the term "comprise" and any of its derivatives (e.g. comprises, comprising) as used in this specification is to be taken to be inclusive of features to which it refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied. 15 Any and all publications mentioned in this specification are herein incorporated by reference. Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form 20 part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia or elsewhere before the priority date of each claim of this application. Although the disclosure has been herein shown and described in what is conceived to be the 25 most practical and preferred embodiment, it is recognised that departures can be made within the scope of the invention, which is not to be limited to the details described herein but is to be accorded the full scope of the appended claims so as to embrace any and all equivalent devices and apparatus. 7