GB2453119A

GB2453119A - Pre-fabricated hollow base for domestic gas tank

Info

Publication number: GB2453119A
Application number: GB0718701A
Authority: GB
Inventors: Robert Michael Cox
Original assignee: Calor Gas Ltd
Current assignee: Calor Gas Ltd
Priority date: 2007-09-25
Filing date: 2007-09-25
Publication date: 2009-04-01
Also published as: GB0718701D0

Abstract

The hollow pre-formed base 2 may be moulded from a medium density polyethylene. It may have a reinforcing framework of hollow steel section. The upper surface of the base is preferably connected to its underside at a plurality of positions. A cover 38, 50 may be provided which is preferably a vacuum formed polythene polystyrene mix or polypropylene and may be slidable telescopically relative to the base. The base may have a load-bearing central spine. It may have means for securing a leg of a tank thereto, preferably a pair of lugs on the upper surface. Locating means, such as a tab and recess may be formed on a side of the base. A raised edge comprising drainage channels may be provided around the perimeter of the base. In use top soil 64, 66 is removed and underlying soil 68 compacted prior to locating the base on a layer of compacted aggregate 70. The base is then preferably filled with non-combustible ballast such as sand or water.

Description

-I-

A TANK BASE

The invention relates to a base for a storage tank. More specifically, but not exclusively, the invention relates to a base for a bulk gas storage tank for domestic applications.

In domestic heating and cooking applications, many people favour gas over electricity.

Many properties are connected to a mains gas supply, but for others, often those in more remote areas, it is necessary to have a bulk storage tank to contain the fuel.

Domestic bulk storage tanks rest on bases, which are commonly prepared from concrete. The bases may either be cast in situ, or be constructed from one or more pre-cast base pieces.

In order to cast a base in situ, the ground first has to be prepared. The area for tank location is identified, topsoil is removed, weed stop material is laid to prevent growth through the concrete, and 6" (150mm) of hardcore is laid and compacted. Once the ground has been prepared, 6" of concrete is poured into shuttering to form a concrete base on top of the compacted hardcore. The concrete must be allowed to cure fully, which can take up to 7 days, before the tank can be delivered and craned into position on the base. The process of casting the base on site allows absolute freedom in the size of base to be prepared, but gives rise to a significant delay in the installation process while the concrete is allowed to cure.

Using pre-cast bases, typically concrete pads approximately Im x 0.8m, eliminates the delay associated with letting the concrete base cure on site. The ground is prepared as described above, and then pre-cast bases are delivered to the site for positioning on the prepared area. This method, however, limits the possible size of the finished base to multiples of the dimensions of a few standard pre-cast pads. Furthermore, the weight of each pre-cast pad (approximately 250kg), makes it necessary to use a crane to lift the pads into position.

It would be beneficial if there was a way of forming a tank base, which did not cause long delays in the installation process, while also allowing maximum flexibility and ease of installation.

According to the present invention there is provided a base for a storage tank, the base comprising a pre-formed hollow base unit positionable between a storage tank and an area of ground on which the storage tank is to be located. The hollow nature of the base unit allows weight to be minimised, simplifying the installation process.

The pre-formed base unit is preferably formed of a plastics material such as Medium Density Polyethylene (MDPE) or similar, which may be moulded to shape. Preferably a reinforcing framework, for example of hollow steel section, is provided within the hollow base unit. To provide extra strength and rigidity to the base unit, the upper and lower surfaces of the hollow structure may be joined together at a number of points.

The base may further comprise a cover part, to cover at least part of the pre-formed base unit. The cover part is preferably a vacuum formed part of a plastics material, such as a Polyethylene Polystyrene mix, a Polypropylene, a Polyethylene or similar.

The cover part should be slidable telescopically relative to the pre-forrned base unit, to allow a number of base sizes to be provided.

The pre-formed base unit may beneficially comprise a load bearing central spine, to support the weight of a storage tank. Means are preferably provided on the pre-formed base unit for securing a leg of a storage tank to the unit. The securing means should preferably be on the load bearing central spine, and may comprise a pair of lugs extending from an upper surface of the pre-formed base unit. To aid stacking of a number of base units, the opposite, underside, of the pre-formed base unit may comprise means for receiving the lugs provided on the upper surface.

More than one base unit may be needed to form a suitable tank base. In this respect, it is beneficial if a side of the base unit is provided with locating means, perhaps in the form of a tab and a recess, to align with similar locating means provided on a second base unit.

The base formed may comprise a raised edge around its perimeter, formed by raised sections of the base unit(s) alone, or in combination with raised edge sections of the cover part(s). Channels may be provided in the raised edge section for drainage purposes.

The base may be installed by preparing an area of ground by removing a layer of topsoil, compacting the remaining soil, and laying and compacting a layer of aggregate.

A base as described above may then be simply positioned on top of the aggregate layer. Where the base comprises a raised edge around its perimeter; gravel, granite, shingle, slate, marble chips, cobbles or similar non-combustible and preferably decorative material may be poured into the base to provide an aesthetically pleasing finish. A storage tank may be secured to the base either before or after the base is positioned on top of the aggregate.

The invention will be better understood with reference to the following detailed description of a preferred embodiment. Throughout the following description reference is made to a number of accompanying drawings, in which: Figure 1 is a perspective view of the top of a base unit for a tank base according to the present invention; Figure 2 is a perspective view of the bottom of a base unit for a tank base according to the present invention; Figure 3 is a perspective view of steel framework from a base unit for a tank base according to the present invention; Figure 4 is a cut away perspective view of a base unit, showing the framework of Figure 3; Figure 5 is a perspective view a stack of base units for tank bases according to the present invention; Figure 6 is an end view of the stack of base units in Figure 5, taken in the direction of arrow A; Figure 7 is a perspective view of an end cover for a tank base according to the present invention; Figure 7a is a plan view of the end cover of Figure 7; Figures 7b and 7c are end views of the end cover of Figure 7, taken in the direction of arrows B and C respectively; Figure 8 is a perspective view of a middle cover for a tank base according to the present invention; Figure 8a is a plan view of the middle cover of Figure 8; Figures Bb is an end view of the middle cover of Figure 8, taken in the direction of arrow B; Figure 9 is a perspective view of the assembly of a tank base according to the present invention; Figure 9a is a detailed view showing the interaction of a base unit and a middle cover; Figures lOa to lOd are perspective views showing the connection of the leg of a storage tank to a base unit; Figure 11 is a perspective view of a storage tank on a tank base according to the present invention with a cut away section showing the ground beneath the tank base; and Figure 12 is a perspective view of a storage tank on a finished tank base according to the present invention.

The view of Figure 1 shows the upper surface of a base unit 2 for a tank base. The base unit 2 is a thin, hollow, plate like rectangular part, rotationally moulded from Medium Density Polyethylene (MDPE). Along the middle of the base unit 2, parallel to its longest side, is a raised central support spine 4. A raised edge portion 6 is also provided along each of the shorter sides of the base unit 2. The central support spine 4 and the edge portions 6 are raised to substantially the same height relative to upper surface of the majority of the base unit 2. Two further raised ribs 8 are provided on each side of the central support spine 4, equally spaced between and parallel to the raised edge portions 6. The ribs 8 are not raised to the same extent as the edge portions 6 and spine 4. The spine 4, edge portions 6, and ribs 8 define six discrete lower areas 10 on the upper surface of the base unit 2. Each lower area 10 is moulded with a multi-axial strengthening pattern 12, which in the embodiment shown takes the form of an eight pointed star depressed relative to the upper surface of the base unit 2.

A strengthening rib 13, in the form of an elongate depression, is also provided along the edge of each lower area 10 adjacent the edge of the base unit 2. Two pairs of foot securing lugs 14 are provided on the central spine 4. Each foot securing lug 14 takes the form of an elongate raised section running parallel with the central spine. The pairs are arranged such that one foot securing lug 14 is positioned either side of a marking 16 indicating the location where, in use, the foot of a tank should be positioned on the spine 4 of the base unit 2. The central support spine 4 also includes the product name and logo, and may further have markings indicating the unit's weight, material of manufacture, and recycling information. Warnings such as Read instructions before attempting assembly may also be moulded into, or otherwise displayed on, the central spine 4.' On each longer side of the base unit 2, locating means 18 are provided to allow two base units 2 to be located next to one another. Each locating means 18 comprises a substantially square tab 20 extending laterally from the side of the base unit 2, and a recess 22, sized to accept a tab 20 of a corresponding locating means 18, and provided in the underside of the edge of the base unit 2. Two sets of locating means 18 are provided on each long side of the base unit 2.

Figure 2 shows the underside of the base unit 2 of Figure 1. The underside of the base unit 2 is generally flatter than the upper surface shown in Figure 1, but a strengthening pattern of ribs 24 is provided. The pattern of ribs 24 takes the shape of a six pointed star, similar to the eight pointed pattern of the multi axial strengthening pattern 12 of each lower area 10 of the upper surface, but is larger, covering substantially the entire underside of the base unit 2. In the space where the seventh and eighth points of the star would be, two pairs of stacking lug locators 26 are provided. The stacking lug locator 26 comprises an elongate channel, with a raised lip surrounding it. Each stacking lug locator 26 is sized to receive a foot securing lug 14, and is located on the underside of the base unit 2 directly below a foot securing lug 14 on the top of the base unit 2. Strengthening ribs 23 at the edges of the base unit 2 correspond with the strengthening ribs 13 provided on the upper surface. Figure 2 also clearly shows the recesses 22 of the location means 18 adjacent the tabs 20.

Each base unit 2 has an internal steel framework 3 to provide strength. The framework 3 is shown in Figure 3. The framework 3 comprises a central spine 28, of 100mm x 50mm steel box section, to support the weight of a tank, and outrigger load spreaders 30,31, of 25mm x 25mm steel box section, welded to the spine 28 to distribute the weight evenly through the structure. The outriggers 30,31 are welded at right angles to the spine 28. A longer outrigger 30 is welded at each end of the spine 28 such that the spine 28 is positioned centrally to each long outrigger 30. Two shorter outriggers 31 are welded to each side of the spine 28 and are evenly spaced between and parallel to the longer outriggers 30. Once the framework 3 has been welded it is coated with a corrosion protection such as FP Tri-Cat/CED 1000 PIus, to adhere to BS EN 12476-FeIZnPh/r13/T1.

Figure 4 shows the framework 3 inside a hollow base unit 2. The central spine 28 of the framework 3 lies inside the central spine 4 of the base unit 2, and the outriggers 30,31 lie inside the raised edge portions 6 and raised ribs 8 respectively. The framework 3 is completely enclosed by the hollow moulded plastic of the base unit 2 and is prevented from movement by raised areas (not shown) provided throughout the moulding. The interaction of the ribs 13,23, provided in the upper and lower surfaces of the moulding, also helps to provide strength and prevent flex in the structure. This is further helped by the provision of kiss points' 32 where the upper surface is connected through the hollow interior of the base unit 2 to the lower surface. The kiss points 32 are created by providing deep indentations 34 in the upper surface of the moulding.

These indentations 34 are provided both within and outside of the multi axial strengthening pattern 12 provided in the upper surface of the base unit 2. In total, ninety kiss points 32 are provided. Through the use of a hollow plastics moulding, and hollow section steel reinforcement, the weight of each base unit can be limited to around 25kg.

Figures 5 and 6 show the stacking of three base units 2. The base units 2 can be stacked for ease of storage, and can be transported, for example by a forklift truck, without fear of sliding, due to the interaction of the foot securing lugs 14 provided on the upper surface of each unit, with the stacking lug locators 26 provided on the underside. The interaction can be seen most clearly in the end view of Figure 6. With each foot securing lug 14 located in a stacking lug locator 26, the base units 2 can be stacked securely and prevented from sliding relative to one another. This obviates the need for further securing means, or wrapping of the units to prevent relative movement, and allows larger stacks to be formed more safely. The interaction of the foot securing lugs 14 and stacking lug locators 26 also means that a clearance 36 is created between adjacent top and bottom surfaces of the stacked base units 2 for a majority of their area.

Figure 7 shows a perspective view of an end cover 38, to cover one end of a base unit 2. Alternate views of the end cover 38 are shown in Figures 7a, 7b and 7c. The end cover 38 is vacuum formed from a Polyethylene Polystyrene mix, and takes the form of a thin shell which is substantially rectangular in plan. The longer side of the end cover 38 is substantially equal in length to the longer side of the base unit 2, and the shorter side of the end cover 38 is slightly longer than the part of the base unit 2 to either side of the central spine 4. Accordingly, the end cover 38 is capable of completely covering the part of the base unit 2 lying to one side of the central spine 4, including the extra length created by the tabs 20 of the locating means 18. The end cover 38 is provided with a multi-axial strengthening pattern 40, which is essentially a reverse of the multi-axial strengthening pattern provided on the lower areas 10 of the upper surface of the base unit 2. The pattern 40 is provided in three discrete areas, divided by two raised ribs 42, which correspond to the raised ribs 8 of the base unit 8. Each area also features an elongate strengthening rib 44, similar to the elongate strengthening rib 13 of the base unit. The features are more clearly shown in the plan view of Figure 7a. A raised lip 46 is provided along the two shorter sides, and one of the longer sides of the end cover 38. The longer side of this raised lip 46 is provided with three channels 48, best shown in the end view of Figure 7c, for reasons which will be explained later. The end view of Figure 7b shows the thin cross-section of the end cover 38, and shows the shape of the lip 46 on the two short sides. The cross-section allows the end cover 38 to slide over the base unit 2, and to be movable with a telescoping action.

Figures 8, 8a and 8b show various view of a middle cover 50, to slide over one or more base units 2. The middle cover 50 is most easily described with reference to the end cover 38 of Figure 7. The middle cover 50 is similar to the end cover 38 in terms of construction and overall shape. The cover is rectangular in plan and is provided with a strengthening pattern 40 and ribs 42 exactly as seen in the end cover 38. However, the middle cover 50 has a short side shorter than the part of the base unit to either side of the central spine 4, and does not include the strengthening ribs 44 at the edge of each of three discrete areas. The difference in size, and missing features can be easily seen by comparing the plan view of the end cover 38 (Figure 7a) with that of the middle cover 50 (Figure 8a). The raised lip 52 is only provided along the two shorter edges of the middle cover 50; both longer edges of the middle cover 50 are open allowing either end of the middle cover 50 to slide onto a base unit 2 in the same way as the end cover 38. The end view of Figure 8b shows that the cross-section of the middle cover 50 is similar to that of the end cover 38.

The product name and logo, weight, material of manufacture, and recycling information may also be displayed on each middle cover 50 and end cover 38. It is also worth noting that, due to the clearance 36 provided when stacking base units (see Figure 6), it is possible to assemble middle covers 50 or end covers 38 onto the base units 2 before stacking, without affecting the integrity of the stack.

The perspective view of Figure 9 shows the assembly of a tank base according to the present invention from two base units 2, two end covers 38 and a middle cover 50. The tank base being formed is suitable for a 12001 gas storage tank. The various parts are assembled as indicated, with the two base portions 2 abutting one another such that the tabs 20 of the locating means 18 of a fist base unit 2 engage with the recesses 22 of the locating means 18 of the second base unit 2 and vice versa. The middle cover is slid over one side of one of the two base units 2 prior to the abutment, and is then slid back to cover the join between the two base units 2. Figure 9a shows a cross-section of the middle cover 50 in position on a base unit 2. The cross sectional shape of the middle cover 50 surrounds the raised edge portions 6 of the base unit 2, retaining the middle cover 50 in place, but allowing it to slide freely relative to the base unit 2. A portion of the internal steel framework 3 is also shown. The end covers 38 engage with the base units in exactly the same way as shown in Figure 9a. When the tank base is fully assembled, the base units 2, middle cover 50 and end covers 38 form a tray like structure for positioning below a gas tank. The channels 48 provided in the end of the end covers 38 allow any water collected in the tray during use to escape.

Figures lOa to lOd show the process of securing the leg 54 of a typical gas tank 56 to a base unit 2. The process can take place once the tank base has been completed and installed in a desired location. Alternatively, the tank base can be formed and secured to a gas tank 56 prior to lifting into position as a single unit. The leg 54 of the gas tank 56 has a closed loop shape, with two substantially vertical parts connected to the tank 56 and a substantiallyhorizontal foot portion 55. Firstly, as shown in Figure lOa, a gas tank 56 is lowered into position such that a foot 55 of the tank 56 is located on a marking 16 provided on the central spine 4 of the base unit 2, between two foot securing lugs 14. Each foot securing lug 14 has a curved surface at its top edge to aid in guiding the foot 55 of the tank 56 into the appropriate position. Once ihe foot 55 of the tank 56 is in position between the foot securing lugs 14 (as shown in Figure lOb) the weight of the tank is supported by the central spine 4 of the base unit 2, and the steel framework (not shown) takes the load and distributes it evenly throughout the base unit 2. A slide lock 58 (a pressed 2mm PP shape) is then slid through a slot 60 provided in the first foot securing lug 14, and above the foot portion 55 of the leg 54 of the tank 56, between the substantially vertical portions. The slide lock 58 is provided with a pair of prongs 62 which are configured to flex as the slide lock 58 moves through the slot 60 provided in each foot supporting lug 14 in a first direction (as indicated by arrow A), but to prevent withdrawal of the slide lock 58 in the opposite direction. The slide lock 58 is shown during insertion in Figure lOc, passing through a slot 60 in one of the foot supporting lugs 14, and between the substantially vertical portions of the leg 54 of the tank 56. The slide lock 58 is shown fully inserted through slots 60 in both foot securing lugs 14 in Figure lOd. Once the slide lock 58 is fully inserted and locked in place, the foot 55 of the gas tank 56 is retained in position on the central spine 4 of the base unit 2 by the foot securing lugs 14 and the slide lock 58.

Figure 11 shows a gas storage tank 56 in place on a tank base constructed according to the present invention. The tank 56 is a 12001 gas storage tank, and the base is constructed as shown in Figure 9. The tank and base are secured together as shown in Figures lOa to lOd. Figure 11 shows the tray like configuration of the finished base, with the middle cover 50 covering the join between the two base units 2 and an end cover 38 covering the ends of each base unit 2. Cut-aways of the ground beneath the tank base show how the ground is prepared prior to installation. The grass 64 and a thin layer of topsoil 66 are removed from the area under the base. The remaining topsoil 68 is compacted with a whacker plate to provide a stable foundation, and a thin layer (approximately 100mm) of gravel and/or hardcore 70 is laid and compacted to provide a level surface for the tank base. The tank base can then be positioned onto this surface ready to receive a storage tank 56. Alternatively, the base and tank 56 can be assembled as previously described and craned into position as a single unit. The tank base forms a complete barrier to weed growth underneath the tank 56.

Figure 12 shows the tank 56 and base in a finished state. The raised lips 46,52 of the end and middle covers 38,50, together with the raised edge portion 6 of the base units 2 form a lip to a tray, which can be filled with decorative gravel, or similar, to provide a more aesthetically pleasing base which can blend in to the tank surroundings. The channels 48 provided in the end covers 38 are also clearly shown.

The base described does not cause any undue delay during installation, because there is no need to let large amounts of concrete dry. The individual components are lightweight and easily handled, and the telescopic nature of the cover parts allows great flexibility in the size of base that can be prepared. The solid base provides a barrier to weed growth, obviating the need for any separate weed stop material or treatment.

The forgoing description relates only to one preferred embodiment of the present invention, and is not intended to limit the protection sought. Numerous modifications to the system shown are possible. For example, the base formed is suitable for a 12001 tank but the telescoping nature of the cover parts means that numerous alternative base sizes are possible. Where a larger base, for example for a 20001 tank, is required, additional base units 2 may be employed or, alternatively, two base units 2 could each be provided with a pair of end covers 38. The gap that would otherwise exist between the base units 2 could be covered by extending the end covers 38 towards each other.

The components described could be assembled in several combinations to provide bases ranging from im x 2m, to im x 3m, and possibly beyond.

The materials specified in the detailed description, and those mentioned elsewhere in the document, should be seen only as examples of a far greater number of possible -11 -materials which could be used in the device. Any material having the necessary characteristics in terms of formability, strength etc. could be substituted without departing from the inventive concept.

Claims

CLAIMS: 1. A base for a storage tank, the base comprising a pre-formed hollow base unit positionable between a storage tank and an area of ground on which the storage tank is to be located.
2. A base according to claim 1, wherein the pre-formed base unit is formed of a plastics material.
3. A base according to claim 2, wherein the plastics material is Medium Density Polyethylene.
4. A base according to claim 2 or 3, wherein the pre-formed base unit is moulded.
5. A base according to any of the preceding claims, wherein the pre-formed base unit is provided with a reinforcing framework.
6. A base according to claim 5, wherein the framework is of hollow steel section.
7. A base according to any of the preceding claims, wherein an upper surface of the hollow base unit is connected to an underside of the hollow base unit at a plurality of positions across the width of the unit.
8. A base according to any of the preceding claims, wherein a cover part is provided to cover at least part of the pre-formed base unit.
9. A base according to claim 8, wherein the cover part is a vacuum formed plastics part.
1O.A base according to claim 9, wherein the cover part is formed from a Polyethylene Polystyrene mix.
11.A base according to claim 9, wherein the cover part is formed from a Polypropylene.
12.A base according to any of claims 8 to 11, wherein the cover part is slidable telescopically relative to the pre-formed base unit.
13.A base according to any of the preceding claims, wherein the pre-formed base unit comprises a load bearing central spine.
14.A base according to any of the preceding claims, wherein the pre-formed base unit comprises means for securing a leg of a storage tank to the pre-formed base unit. -13-
15.A base according to claim 14, wherein the means for securing the tank leg comprises a pair of lugs extending from an upper surface of the pre-formed base unit.
16. A base according to claim 15, wherein an underside of the pre-formed base unit comprises means for receiving the lugs provided on the upper surface.
17.A base according to any of the preceding claims, wherein a side of the base unit is provided with locating means.
18.A base according to claim 17, wherein the locating means comprise a tab and a recess.
19.A base according to any of the preceding claims, wherein a raised edge is provided around the perimeter of the base.
20.A base according to claim 19, wherein drainage channels are provided in the raised edge section.
21.A method of forming a tank base, comprising the steps of removing a layer of topsoil from an area of ground, compacting the remaining soil, laying and compacting a layer of aggregate, and positioning a base according to any of the preceding claims on top of the aggregate.
22.A method of forming a tank base, comprising the steps of removing a layer of topsoil from an area of ground, compacting the remaining soil, laying and compacting a layer of aggregate, and positioning a base according to claim 19 or on top of the aggregate and filling the base with a non-combustible material.
23.A method according to claim 21 or 22, wherein a tank is secured to the base before the base is positioned on top of the aggregate.
24.A method according to claim 21 or 22, wherein a tank is secured to the base after the base is positioned on top of the aggregate.
25. Apparatus comprising a base and a storage tank, wherein the base is as claimed in any of claims I to 20.
26. Apparatus according to claim 25, wherein the storage tank is a gas tank.
27.A base substantially as herein described with reference to the accompanying drawings.
28.A method of forming a tank base substantially as herein described, with reference to Figures 11 and 12 of the accompanying drawings.