AU2016201702A1 - Transportable liquid storage tank - Google Patents

Abstract

Some embodiments relate to a transportable liquid storage tank, comprising a unitary plastic body having a bottom wall, a convex front wall, an opposite convex back wall, opposed side walls joined to the front and back walls by rounded corners, and a top wall; wherein the body is sized and configured so that two of the tanks can fit end to end in a standard 6 metre length shipping container while taking up almost all of a useable shipping space within the container.

Description

2016201702 17 Mar 2016 1 "Transportable liquid storage tank"

Technical Field [0001] Described embodiments generally relate to transportable liquid storage tanks. Background [0002] There are various way liquids can be transported. Some liquids require particular care when being transported, in order to avoid spillage or unsafe conditions.

[0003] Large metal tankers can be used for storage and transport of some liquids, where such tankers are integrated with a transport means, such as a truck chassis or a ship. However, such tankers are relatively expensive to make and operate.

[0004] It is desired to provide an improved liquid storage tank that can be efficiently transported when empty or when full, or to at least provide a useful alternative to prior liquid storage and/or transport techniques.

[0005] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

[0006] Throughout this specification the word "comprise", or variations 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.

Summary [0007] Some embodiments relate to a transportable liquid storage tank, comprising: 2016201702 17 Mar 2016 2 a unitary plastic body having a bottom wall, a convex front wall, an opposite convex back wall, opposed side walls joined to the front and back walls by rounded corners, and a top wall; wherein the body is sized and configured so that two of the tanks can fit end to end in a standard 6 metre length shipping container while taking up almost all of a useable shipping space within the container.

[0008] The top wall may define surface variations that provide increased load-bearing capacity when compared to a flat wall. The surface variations may comprise a crossshape, for example. The surface variations may define raised comer portions and recessed portions between the comer portions, for example. The surface variations may comprise raised ribs.

[0009] The body may define an outlet valve aperture in one of the front wall and the back wall. The tank may further comprise a hand-actuable outlet valve seated in and occluding the outlet valve aperture.

[0010] The body may defines an access aperture in the top wall. The tank may further comprise an access hatch occluding the access aperture, the access hatch being openable to allow access to an interior of the tank via the access aperture, the access hatch comprising a hand-actuable valve to allow or block fluid communication through a vent aperture.

[0011] The tank body may be rotationally moulded. The tank body may be formed of polyethylene, for example, such as linear low density polyethylene (LLDPE).

[0012] A curvature of the convex front wall may be substantially the same as a curvature of the convex back wall. The side walls may have a substantially same convex curvature as each other. A radius of curvature of the side walls may be different from, optionally larger than, a radius of curvature of the front and back walls. 2016201702 17 Mar 2016 3 [0013] The body may have a generally rounded cuboid or rectanguloid shape with bulged sides.

[0014] The tank may further comprise a plurality of coupling lugs projecting from the front wall and the back wall. The plurality of coupling lugs may comprise four lugs projecting from the front wall and four lugs projecting from the back wall, each coupling lug being disposed near a comer of the front wall or the back wall. The coupling lugs may be integrally formed with the body. Each lug may define a coupling aperture.

[0015] The tank may further comprise a plurality of ribs projecting from the front wall. The plurality of ribs may be laterally spaced across a middle part of the front wall. The plurality of ribs may comprise a first plurality of ribs on one lateral side of the front wall and a second plurality of ribs on an opposite lateral side of the front wall. The first and second plurality of ribs may be configured to avoid projecting further forward than an outermost part of the convex front wall.

[0016] The tank may further comprise a plurality of ribs projecting from the back wall. The plurality of ribs may be laterally spread across a middle part of the back wall and are configured to avoid projecting further backward than an outermost part of the convex back wall.

[0017] The front wall may form a portion of a first spherical surface and the back wall may form a portion of a second spherical surface. A centre of the first spherical surface may be spaced from a centre of the second spherical surface. The radius of curvature of the first and second spherical surfaces may be between about 3.0m and about 3.5m, for example. A radius of curvature of the side walls may be between about 5.0m and about 6.0m.

[0018] A wall thickness of the body may be nominally 20 mm and may have some areas of lesser thickness across large wall areas and some areas of greater thickness at comers and other areas requiring structural strength. 2016201702 17 Mar 2016 4 [0019] A storage capacity of the tank may be greater than 10,000 litres, and may be greater than 11,000 litres.

[0020] Some embodiments relate to a rotationally moulded transportable liquid storage tank, comprising a unitary plastic body resembling a cube with bulged side walls and a closed top, the body being sized so that two of the tanks can fit end to end in a standard 6 metre length shipping container while taking up almost all of a useable shipping space within the container.

[0021] Some embodiments relate to a rotationally moulded transportable liquid storage tank, comprising: a closed unitary plastic body having a bottom wall, opposed convex front and back walls, opposed convex side walls and a top wall; wherein a hand-actuable outlet valve is disposed in a lower part of the front wall and a vent aperture is disposed in or toward the top wall; and wherein a storage capacity of the tank is greater than 10,000 litres.

[0022] Some embodiments relate to a method of transporting liquid, comprising filling first and second storage tanks according to any of the embodiments described herein with liquid to be transported, loading the first tank into a shipping container and loading the second storage tank into the shipping container so that the first and second storage tanks are positioned end-to-end within the shipping container; and transporting the shipping container. The method may include anchoring the storage tanks to the shipping container.

[0023] Where the shipping container is long enough to accommodate more than two storage tanks, the method may comprise filling third and fourth storage tanks with the liquid to be transported and loading the third and fourth storage tanks into the shipping container prior to the transporting. 2016201702 17 Mar 2016 5 [0024] Some embodiments relate to a method of transporting liquid storage containers, comprising loading first and second empty storage tanks according to any of the embodiments described herein into a shipping container so that the first and second storage tanks are positioned end-to-end within the shipping container; and transporting the shipping container. The method may include anchoring the storage tanks to the shipping container. Where the shipping container has an open top, the method may comprise stacking two further empty storage tanks according to any of the embodiments described herein on top of the first and second empty storage tanks and anchoring the two further storage tanks to the shipping container and/or the first and second storage tanks.

[0025] Some embodiments relate to a method of manufacturing a transportable liquid storage tank, comprising: rotationally moulding a unitary closed plastic body having a storage capacity of at least 10,000 litres, the body having a bottom wall, a convex front wall, an opposite convex back wall, opposed side walls joined to the front and back walls by rounded comers, and a top wall; fitting an outlet valve to control fluid flow through an aperture in a lower part of the front wall; and fitting a vent valve to control venting through an aperture in or near the top wall; wherein the body is sized and configured so that two of the tanks can fit end to end in a standard 6 metre length shipping container while taking up almost all of a useable shipping space within the container.

Brief Description of Drawings [0026] Embodiments are described in further detail below, with reference to the accompanying drawings, in which: 2016201702 17 Mar 2016 6 [0027] Figure 1A is a top perspective view of a storage tanker according to some embodiments; [0028] Figure IB is a bottom perspective rear view of the storage tanker of Figure 1A; [0029] Figures 2A, 2B, 2C, 2D and 2E are plan, side, front, back and bottom views, respectively, of the storage tank of Figure 1 A; [0030] Figure 3 is an elevation view illustrating a possible horizontal and vertical stacking arrangement using multiple storage tanks as shown in Figure 1A; [0031] Figure 4A is a plan view illustrating how two storage tanks according to described embodiments can fit end-to-end within a standard shipping container; [0032] Figure 4B is an end view corresponding to Figure 4A, showing storage tanks within a shipping container, as seen from one end of the container; [0033] Figure 4C is a perspective view illustrating how two of the storage tanks can fit within a standard shipping container, where the shipping container is shown in partial cutaway and without its top roof panel; [0034] Figures 5A, 5B and 5C illustrate an outlet valve mechanism positioned towards a bottom of the storage tank according to some embodiments; [0035] Figure 6 is a perspective view of a fluid outlet and control valve that is fitted to the storage tank as shown in Figures 5A to 5C; [0036] Figures 7A and 7B are bottom and top perspective views of a top lid closure of the storage tank according to some embodiments; [0037] Figure 8 is an exploded perspective view of the top lid closure shown in Figures 7A and 7B. 2016201702 17 Mar 2016 7

Description of Embodiments [0038] Described embodiments generally relate to transportable liquid storage tanks.

[0039] Embodiments generally relate to transportable liquid storage tanks that can be formed in a moulding process, such as by rotational moulding, for example. Described tanks are intended to provide a relatively large (at least for transportable plastic tanks) liquid storage capacity, such as greater than 10,000 litres. In some embodiments, the actual capacity may be greater than 11,000 litres, such as an actual capacity of 11,300 litres and a useable capacity of around 11,000 litres.

[0040] The described liquid storage tank embodiments are designed to be able to fit two tanks to a single standard (general purpose intermodal) shipping container of 6 metre length and 2.6 metre height while using almost all of the useable space within the shipping container. For example, the two tanks may be sized to take up 85%-90% or more of the available storage space within such a shipping container. This allows liquid to be effectively transported within shipping containers, which has advantages for efficient use of containers and shipping logistics. Figures 4A to 4C illustrate how two tanks according to described embodiments can fit snugly end to end within one shipping container. In some embodiments, where the shipping container is of 12 metre length, four of the described tanks can be positioned end-to-end while taking up almost all of the useable space in the container. While described storage tanks are sized and configured to be able to easily and optimally fit multiple such tanks within standard 6 and 12 metre intermodal shipping containers, they may also be used to transport liquids in other scenarios and in other container sizes or configurations that can accommodate the tank’ dimensions.

[0041] Figures 1A, IB, 2A, 2B, 2C, 2D and 2E show various views of a storage tank 100 according to some embodiments. The tank 100 has a unitary body 101 that has a bottom wall 102, a front wall 103, a back wall 104, opposite side walls 105, 106 and a top wall 107, all of which are adjoined along slightly rounded (or “radiused”) corner portions. For example, bottom wall 102 is joined to the front wall 103, back wall 104 2016201702 17 Mar 2016 8 and side walls 105, 106 via corner portions 113 that are somewhat rounded. Further, the front wall 103 is joined to the side walls 105, 106 by rounded comer portions 112 and to the top wall 107 via rounded corner portion 114. Similarly, back wall 104 is joined to side walls 105, 106 by rounded comer portions 112 and to top wall 107 by rounded comer portion 114.

[0042] Storage tank 100 is formed by rotational moulding according to some embodiments. According to such embodiments, all of the tank walls are integrally formed with the corner portions 112, 113 and 114 that connect them to each other. Once the unitary body 101 is formed by rotational moulding, an outlet 115 is fixed in place in a lower portion of the front wall 103 (or optionally the back wall 104) in order to allow the liquid contents of the tank to be dispensed through a valve and conduit (described in further detail in relation to Figures 5A to 5C and 6) and to allow liquid to be pumped into the tank. Further, an access hatch 120 is fixed in position in a part of the upper wall 107 towards the front wall 103. In alternative embodiments, the access hatch 120 may be located in an upper part of one of the front, back or side walls. The access hatch 120 is shown and described in further detail below, with reference to Figure 7A, 7B and 8.

[0043] The storage tank 100 has a shape that resembles a generally cuboid or possibly rectanguloid shape with bulged sides. In particular, the front wall 103 and the back wall 104 bulge outwardly to a greater degree than the side walls 105, 106. In some embodiments, the front wall 103 and back wall 104 have a substantially same convex curvature (in opposite directions). The front wall 103 and back wall 104 may be curved to emulate a part-spherical surface with a radius of curvature in the order of about 3 to 3.5 metres, preferably about 3.2 metres. For the front wall 103, the centre (ie origin) of the part-spherical surface lies outside of the tank body 101, past the back wall 104. Similarly, the curvature of the part-spherical surface of the back wall 104 has its centre outside of the tank body 101, past the front wall 103.

[0044] Side walls 105 and 106 are each convexly curved with a different radius of curvature to the front and back walls 103, 104. The side walls 105, 106 follow a part- 2016201702 17 Mar 2016 9 cylindrical contour, defining oppositely directed convex surfaces. The convex end and side wall surfaces may alternatively be described as dished or domed end and side wall surfaces. The radius of curvature of the side walls 105, 106 is the same for each of those walls. For example, the radius of curvature of the side walls 105, 106 may be between about 5 metres and about 6 metres, for example around 5.5 metres.

[0045] The top wall 107 is formed to be partially flat and have some areas of surface variation. Top wall 107 is generally parallel to the bottom wall 102, which may also be generally flat or have some surface variation. The top wall 107 does have surface variations to assist in providing greater load bearing capacity by strengthening the top wall 107. Such surface variations can include, for example, a series of ribs 108 projecting vertically upward from the rest of the upper surface of the top wall 107, as well as raised or projecting comer portions 110. The ribs 108 may be formed to have a generally cross-shaped configuration as shown in the drawings, with the ribs intersecting at a centre region or portion 109. Instead of a cross-shape of the ribs 108, they may be formed to have additional or other shapes or patterns that still provide a strengthening function to increase the ability of the top wall 107 to distribute vertical load. For example, the cross-shaped ribs 108 may be supplemented by a circular shape that is concentric with the central portion 109 but crosses each of the linear ribs 108 at a point inside the comer portions 110. The ribs 108 and comer portions 110 also serve to keep separation between the access hatch 120 and an object (such as another storage tank 100) that is resting on the ribs 108 and/or comer portions 110.

[0046] In some embodiments, the central portion 109 may house a further vent valve 199 to act as a one-way breather valve, allowing pressure equalisation between the inside and outside of the tank 100. The vent valve 199 defines a passage (not shown) between the internal volume of the tank 100 and the external environment. The vent valve 199 has a closure (not shown) disposed in or near a lower end of the passage, inside the tank 100. The closure can move between a normally non-activated state or position, in which the closure does not fully block or occlude the passage, and an activated state or position, in which it is configured to substantially close off the passage to liquid flow to the external environment. The closure moves to the activated 2016201702 17 Mar 2016 10 state in response to an increase in liquid level, for example due to sloshing of liquid within the tank 100, to stop liquid from flowing out of the tank 100. For example, the closure may include a floating ball held captive at or near the lower end of the passage but movable upward to block the passage when liquid in the tank (temporarily) reaches the level of the bottom of the passage. The tank 100 may therefore have three valves, two of which are hand-actuable and one of which is automatic, for example. The valve 199 may be fitted to the tank 100 after the rotational moulding process has been completed, for example by cutting a small cylindrical passage (sized to snugly receive the valve 199) downwardly through the middle of central portion 109 and then fitting the valve 199 sealingly in place in the cylindrical passage.

[0047] The outer dimensions of the tank 100 in the front-to-back (longitudinal) direction may be around 2850 mm, in the side-to-side (lateral) direction may be around 2270 mm and in the top-to-bottom (vertical) direction may be around 2200 mm, for example. Some variation of these dimensions can occur without departing from the spirit and scope of the present disclosure.

[0048] As shown in Figure 3, a stacked arrangement 300 of storage tanks 100 can be made in order to efficiently transport the storage tanks 100, when empty, full or partially full, for example. In the arrangement 300 shown in Figure 3, storage tanks 100 can be vertically stacked, with the bottom wall 102 of an upper tank 100 resting on the top wall 107 (and the comer portions 110 and ribs 108 in particular) of the lower tank 100. Additionally, the storage tanks 100 can be positioned adjacent one another in a horizontal manner, with the front wall 103 of one tank 100 contacting or being directly adjacent to the back wall 104 of the next tank 100. In the horizontally adjacent end to end position shown in Figure 3, the longitudinal and lateral alignment of the two adjacent tanks 100 is aided by the presence of multiple projecting ribs 140 disposed on each lateral side of each tank 100 on the front and back walls 103, 104, respectively. These projecting ribs 140 may be generally T-shaped and are positioned and configured to extend only out to the outermost level of the bulged convex front or back wall and not much further. In some embodiments, the projecting ribs 140 may be sized to extend slightly longitudinally (e.g. 1 to 5 cm) beyond the outer extent of the front and back 2016201702 17 Mar 2016 11 walls 103, 104 in the empty state, so that if the front and back walls 103, 104 bulge further outwardly when full of liquid, the projecting ribs 140 are relatively more aligned with the outer extent of the bulged front and back walls 103, 104. In this way, the front and back walls 103, 104 of adjacent tanks 100 can contact each other while the projecting ribs 140 of the adjacent tanks 100 contact each other in a way that can resist relative rotational displacement of the tanks 100 (that might otherwise occur more readily without the projecting ribs 140 being present).

[0049] In addition to the projecting ribs 140, which can also serve to space the front and back walls 103, 104 of the tank 100 from the front and back walls of a container 400 (see for example Figure 4A), a series of coupling lugs 130 are formed on the front and back walls 103, 104. The front wall 103 has four coupling lugs 130, each positioned toward a corner (ie top left, top right, bottom right, bottom left) of the front wall 103. These coupling lugs 130 each define a small circular aperture 131 towards one end thereof in order to allow a cable or connector to be passed through it to couple to the lug 130 for pulling, anchoring or otherwise positioning the tank 100.

[0050] The coupling lugs 130 are integrally moulded as part of the front wall 103 (and also the back wall 104) with an elongate shape that narrows and gets further away from the wall surface in a direction from the middle of the tank toward the top or bottom. Other than the presence of the apertures 131 in the lugs 130, they are formed of solid plastic material. Similarly, projecting ribs 140 are solid plastic and integrally formed with the front and back walls 103, 104. As with the front wall 103, the back wall 104 also has four coupling lugs 130 projecting from the wall surface at the four comers of the back wall 104, as seen best in Figure IB. In alternative embodiments, the coupling lugs 130 may be non-integrally formed with the front and back walls 103, 104, instead being connected thereto post-moulding.

[0051] Other than the coupling lugs 130 and projecting ribs 140, the body 101 of the tank 100 is generally hollow. Although the wall thickness of the body 101 may have a nominal thickness, such as around 20mm (or possibly other nominal thicknesses in the range of 15mm to 25mm), the actual thickness of the rotationally moulded plastic walls 2016201702 17 Mar 2016 12 of the body 101 varies across different parts of the body 101. For example, the thickness across large areas, such as the bottom wall 102, side walls 105, 106 and front and back walls 103, 104, may have areas that are a little less than the nominal thickness, for example in the order of 5, 10, 15 or 20%, while other areas that require greater structural strength and/or rigidity, such as the ribs 108 and comer portions 110, may have a thickness greater than the nominal thickness by 5, 10, 15 or 20%, for example.

[0052] Polyethylene (in a granulated/powder form) is used to form the body 101 of the tank 100 in the rotational moulding process. Although in some instances high density polyethylene may be used, low density polyethylene is preferred for some embodiments. In particular, linear low density polyethylene (LLDPE) is preferred for some embodiments. Various classes of granulated polyethylene powders can be used to form the body 101, such as those marketed as “Microlene” resin powders supplied by Martogg Group of Companies. Where the tank 100 is intended to transport certain chemicals, such as aggressive or toxic chemicals or hydrocarbons, an appropriate grade of polyethylene is preferred. For example, where the liquid to be transported in the tank 100 is diesel fuel, a particular grade of polyethylene is preferred that has a more dense molecular structure to avoid the diesel penetrating the tank wall. The polyethylene powder that may be used to form the body 101 in this example (to transport Diesel) may be Microlene D6300 UV R02 GY1997, for example.

[0053] Figures 4A, 4B and 4C illustrate how two tanks 100 can fit within a normal sized (6 metre length) standard intermodal shipping container 400 that has side walls 405, a floor 406, a roof 408, an end wall 407 and a front door (or set of doors) 410. Figures 4A and 4C show how two tanks 100 can fit within the container 400 so that the back wall 104 of one container is directly adjacent the front wall 103 of another tank 100.

[0054] In some embodiments, the tanks 100 may be oriented with their back walls 104 adjacent each other, so that the liquid contents of the tanks 100 can potentially be accessed and dispensed through openings or missing sections of end wall 407 and front 2016201702 17 Mar 2016 13 door 410. Such embodiments allow the liquid tanks 100 to be transported to a particular site for dispensing of their contents without the need to remove them from the container 400. Once the contents of the tanks 100 are suitably dispensed or emptied, then the container 400 and tanks 100 can be readily transported again as a unit without the need to put the tanks 100 back into the container 400.

[0055] Relatively little clearance is allowed along the sides of the tanks 100 adjacent container walls 405. Thus, if the side walls 105, 106 of one of the tanks 100 tend to bulge further outwardly due to liquid pressure from inside, the side walls 405 of the container 400 can assist to limit the amount of bulging that can occur and thereby provide reinforcement to the side walls 105, 106. Similar considerations apply where the shipping container is 12 metres in length, in which case four tanks 100 can be positioned end-to-end along the length of the container while using almost all of the useable shipping space in the container. In some situations, a “flat-rack” shipping container frame (without side walls or a roof) may be used to transport empty ones of the tank 100. Such a container frame would allow two or four tanks 100 (depending on whether the container is 6 or 12 metres in length) to be positioned inside the frame and also allow two or four empty tanks 100 to be positioned on top of the two or four that are in the container frame (as it does not have a roof), in a manner similar to that shown in Figure 3. The lugs 130 can be used to secure the four or eight empty tanks 100 into position in relation to the container frame.

[0056] Referring further to Figures 5A, 5B, 5C and Figure 6, an example fluid outlet 115 is shown and described in further detail. The positioning of the fluid outlet 115 shown in the drawings of tank 100 is somewhat different from the position of the outlet 115 shown in relation to tank 100’ in Figures 5A, 5B and 5C (but tank 100’ is otherwise the same as tank 100). For example, Figure 2C shows the fluid outlet 115 towards the bottom right comer of the front wall 103, while Figure 5C shows the outlet 115 positioned within a recessed area 119 that is more centrally positioned along the bottom part of the front wall 103. The exact positioning of the outlet 115 along the lower part of the front wall 103 is not critical, but it is desirable for it to be positioned 2016201702 17 Mar 2016 14 in a location where no part of it projects laterally beyond the outermost part of the front wall 103 or the projecting ribs 140.

[0057] As shown in Figure 6, the outlet 115 comprises a conduit structure to define a fluid path from an inside aperture 118 through a wall portion 103a of the front wall 103, and through a hand actuable valve 116 (such as a butterfly valve) and out through an external aperture that is normally covered by a cap 117. The valve 116 has a handle 116a coupled thereto that can be operated in order to open and close the valve 116. Outlet 115 may also serve as a fluid inlet, whereby the contents of the tank 110 can be pumped into the tank 100 via the fluid path defined by the outlet 115.

[0058] Referring now to Figures 7A, 7B and 8, access hatch 120 is described in further detail. Access hatch 120 has an annular mould-in ring 710 that acts as an anchor for the other parts of the access hatch 120. The mould-in ring 710 is positioned relative to the mould at the beginning of the moulding process so that during the moulding, the plastic of body 101 forms around an annular base part of the ring 710 and through apertures 714, which serve to anchor the mould-in ring 710 in place. The mould-in ring 710 has an upper annular ring defining a series of threaded apertures to receive fasteners 723 to secure a circular sealing plate 720 thereto. The circular plate 720 acts to seal an aperture in the body 101 disposed within the ring 710. This aperture is sized to allow human access into the inner volume of the tank 100, if necessary. The aperture covered by the access hatch 120 is formed by cutting the material of the tank body 101 that is within the area of the mould-in ring 710 after the body 101 has been formed and cooled.

[0059] The circular plate 720 is fastened to the mould-in ring 710 by a series of bolts 723 that thread into the apertures 715 in the upper and lower ring of the moulding ring 710. These bolts 723 may project part-way into the spaces or recesses 714 in the lower annular base section of the mould-in ring 710.

[0060] The circular plate 720 has grab rails 725 that extend from opposite lateral sides to allow the plate 720 to be manually lifted and placed and/or removed if necessary. 2016201702 17 Mar 2016 15

The circular plate 720 also has raised female threaded portions 727 to receive bolts 743 extending through a flange 740 that secures a hand-operable valve 730 in place on the circular plate 720. The valve 730 may be a butter fly valve, for example, having a handle 732 that can be manually manipulated in order to open or close the valve 730. The circular plate 720 has an aperture 726 formed therein to allow passage of fluid, such as gas or air, out of the access hatch 120 when the valve 730 is in an open position. A filter, for example in the form of a perforated cover 750, may be secured over the top of the valve 730 in order to avoid ingress of particulate into the valve 730.

[0061] The perforated cover 750 may be fastened to the circular plate 720 through apertures 752 in outwardly flared wing sections 751 of the cover 750, for example.

[0062] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (39)

1. CLAIMS:

   1. A transportable liquid storage tank, comprising: a unitary plastic body having a bottom wall, a convex front wall, an opposite convex back wall, opposed side walls joined to the front and back walls by rounded comers, and a top wall; wherein the body is sized and configured so that two of the tanks can fit end to end in a standard 6 metre length shipping container while taking up almost all of a useable shipping space within the container.
2. 2. The tank of claim 1, wherein the top wall defines surface variations that provide increased load-bearing capacity when compared to a flat wall.
3. 3. The tank of claim 2, wherein the surface variations comprise a cross-shape.
4. 4. The tank of claim 2 or claim 3, wherein the surface variations define raised comer portions and recessed portions between the corner portions.
5. 5. The tank of any one of claims 2 to 4, wherein the surface variations comprise raised ribs.
6. 6. The tank of any one of claims 1 to 5, wherein the body defines an outlet valve aperture in one of the front wall and the back wall.
7. 7. The tank of claim 6, further comprising a hand-actuable outlet valve seated in and occluding the outlet valve aperture.
8. 8. The tank of any one of claims 1 to 7, wherein the body defines an access aperture in the top wall.
9. 9. The tank of claim 8, further comprising an access hatch occluding the access aperture, the access hatch being openable to allow access to an interior of the tank via the access aperture, the access hatch comprising a hand-actuable valve to allow or block fluid communication through a vent aperture.
10. 10. The tank of any one of claims 1 to 9, wherein the body is rotationally moulded.
11. 11. The tank of any one of claims 1 to 10, wherein the body is formed of polyethylene.
12. 12. The tank of claim 11, wherein the polyethylene is linear low density polyethylene.
13. 13. The tank of any one of claims 1 to 12, wherein a curvature of the convex front wall is substantially the same as a curvature of the convex back wall.
14. 14. The tank of any one of claims 1 to 13, wherein the side walls have a substantially same convex curvature.
15. 15. The tank of any one of claims 1 to 14, wherein a radius of curvature of the side walls is different from, optionally larger than, a radius of curvature of the front and back walls.
16. 16. The tank of any one of claims 1 to 15, wherein the body has a generally rounded cuboid or rectanguloid shape with bulged sides.
17. 17. The tank of any one of claims 1 to 16, further comprising a plurality of coupling lugs projecting from the front wall and the back wall.
18. 18. The tank of claim 17, wherein the plurality of coupling lugs comprises four lugs projecting from the front wall and four lugs projecting from the back wall, each coupling lug being disposed near a comer of the front wall or the back wall.
19. 19. The tank of claim 17 or claim 18, wherein the coupling lugs are integrally formed with the body, each lug optionally defining a coupling aperture.
20. 20. The tank of any one of claims 1 to 19, further comprising a plurality of ribs projecting from the front wall.
21. 21. The tank of claim 20, wherein the plurality of ribs are laterally spaced across a middle part of the front wall.
22. 22. The tank of claim 21, wherein the plurality of ribs comprises a first plurality of ribs on one lateral side of the front wall and a second plurality of ribs on an opposite lateral side of the front wall.
23. 23. The tank of claim 22, wherein the first and second plurality of ribs are configured to avoid projecting further forward than an outermost part of the convex front wall.
24. 24. The tank of any one of claims 1 to 23, further comprising a plurality of ribs projecting from the back wall.
25. 25. The tank of claim 24, wherein the plurality of ribs are laterally spread across a middle part of the back wall and are configured to avoid projecting further backward than an outermost part of the convex back wall.
26. 26. The tank of any one of claims 1 to 25, wherein the front wall forms a portion of a first spherical surface and the back wall forms a portion of a second spherical surface.
27. 27. The tank of claim 26, wherein a centre of the first spherical surface is spaced from a centre of the second spherical surface.
28. 28. The tank of claim 26 or claim 27, wherein the radius of curvature of the first and second spherical surfaces is between about 3.0m and about 3.5m.
29. 29. The tank of any one of claims 1 to 28, wherein a radius of curvature of the side walls is between about 5.0m and about 6.0m.
30. 30. The tank of any one of claims 1 to 29, wherein a wall thickness of the body is nominally 20 mm and has some areas of lesser thickness across large wall areas and some areas of greater thickness at comers and other areas requiring structural strength.
31. 31. The tank of any one of claims 1 to 30, wherein a storage capacity of the tank is greater than 10,000 litres, optionally greater than 11,000 litres.
32. 32. A rotationally moulded transportable liquid storage tank, comprising a unitary plastic body resembling a cube with bulged side walls and a closed top, the body being sized so that two of the tanks can fit end to end in a standard 6 metre length shipping container while taking up almost all of a useable shipping space within the container.
33. 33. A rotationally moulded transportable liquid storage tank, comprising a closed unitary plastic body having a bottom wall, opposed convex front and back walls, opposed convex side walls and a top wall; wherein a hand-actuable outlet valve is disposed in a lower part of the front wall and a vent aperture is disposed in or toward the top wall; and wherein a storage capacity of the tank is greater than 10,000 litres.
34. 34. A method of manufacturing a transportable liquid storage tank, comprising: rotationally moulding a unitary closed plastic body having a storage capacity of at least 10,000 litres, the body having a bottom wall, a convex front wall, an opposite convex back wall, opposed side walls joined to the front and back walls by rounded comers, and a top wall; fitting an outlet valve to control fluid flow through an aperture in a lower part of the front wall; and fitting a vent valve to control venting through an aperture in or near the top wall; wherein the body is sized and configured so that two of the tanks can fit end to end in a standard 6 metre length shipping container while taking up almost all of a useable shipping space within the container.
35. 35. A method of transporting liquid, comprising: filling first and second storage tanks according to any one of claims 1 to 33 with liquid to be transported; loading the first tank into a shipping container; loading the second storage tank into the shipping container so that the first and second storage tanks are positioned end-to-end within the shipping container; and transporting the shipping container.
36. 36. The method of claim 35, further comprising: where the shipping container is long enough to accommodate more than two storage tanks, filling third and fourth storage tanks with the liquid to be transported and loading the third and fourth storage tanks into the shipping container prior to the transporting.
37. 37. A method of transporting liquid storage containers, comprising: loading first and second empty storage tanks according to any one of claims 1 to 33 into a shipping container so that the first and second storage tanks are positioned end-to-end within the shipping container; and transporting the shipping container.
38. 38. The method of any one of claims 35 to 37, further comprising anchoring the storage tanks to the shipping container.
39. 39. The method of claim 37, wherein, where the shipping container has an open top, the method comprises stacking two further empty storage tanks according to any one of claims 1 to 33 on top of the first and second empty storage tanks and anchoring the two further storage tanks to the shipping container and/or the first and second storage tanks.