GB2456041A

GB2456041A - Modular bund with tiled floor

Info

Publication number: GB2456041A
Application number: GB0823216A
Authority: GB
Inventors: Ian A M Pogson
Original assignee: ANDEL Ltd
Current assignee: ANDEL Ltd
Priority date: 2007-12-24
Filing date: 2008-12-19
Publication date: 2009-07-01
Anticipated expiration: 2028-12-19
Also published as: GB0823216D0; GB0725135D0; GB2456041B

Abstract

A modular bund 1 includes a floor 2 and a retaining wall 3. The floor comprises a plurality of inter-engaging, non-porous tiles 6 and the retaining wall comprises a plurality of non-porous panels 19 supported by brackets 20 or posts 21. Advantageously, the tiles comprise rectangular tiles which are provided along two adjacent edges with an overlap 8 and along the other two adjacent edges with an underlap 9. Joints between the tiles, the panels and the panels and the floor are sealed with a non-porous sealant. The whole of the floor and the retaining wall within the bund may be coated with a non-porous sealant such as an elastomeric polyurethane coating. Self-tapping fasteners may be used to secure the tiles and the tiles laid on a foundation of concrete beams and slabs. A pump and sump may be provided for draining the bund, the pump being able to determine the detect rainwater and drain the bund automatically accordingly.

Description

-1-2456041

A MODULAR BUND ARRANGEMENT

The present invention relates to a modular bund arrangement.

It is now a legal requirement to provide a secondary containment for storage tanks and the like which hold environmentally unfriendly liquids such as oil. This is to prevent environmental damage should the tank develop a leak or if spillage occurs in other ways, for example during tank filling or evacuation.

The object of the present invention is to provide a modular bund arrangement, which can be either retro-fitted around an existing storage facility or which can be provided as part of the installation of a new storage facility. :1.5

According to the present invention there is provided a modular bund arrangement including a floor comprising a plurality of inter-engaging, non-porous tiles; a retaining wall comprising a plurality of non-porous panels supported by brackets or posts; and wherein joints between the tiles, the panels and the panels and the floor are sealed by a non-porous sealant.

Preferably, the floor and inner surfaces of the retaining wall within the bund arrangement are coated with a non-porous sealant arrangement.

Preferably also, the sealant arrangement comprises a mat that is laid over the floor and the inner surfaces of the retaining wall and over which is spread one or more coats of a non-porous sealant.

Preferably also, the retaining wall and tiles are laid over a base structure comprising a grid of slabs and/or beams that is filled with concrete to form a level surface.

Preferably also, a plurality of the tiles comprise rectangular tiles which are provided along two adjacent edges with an overlap and along the other two adjacent edges with an underlap in order that these tiles lap together when forming the floor.

Preferably also, fasteners are used to securing lapping portions of the tiles.

Preferably also, the retaining wall comprises a plurality of substantially rectangular panels that inter-engage along their length.

Other preferred but non-essential features of the various aspects of the present invention are described in the dependent claims appended hereto.

The present invention will now be described by way of example with reference to the accompanying drawings, in which:-Fig. 1 is a perspective, schematic view of a modular bund arrangement according to the present invention when in use around an electricity transformer and prior to the application of a sealant arrangement over a tile floor and other surfaces of the bund arrangement, part of the tile floor being broken away to reveal a base structure; Fig. 2 is a schematic vertical cross-section through part of a bund arrangement showing the way the arrangement is retro-fitted around an existing apparatus such as the electricity transformer shown in Fig. 1; Fig. 3 is a plan view of a tile forming part of a floor of the bund arrangement shown in Fig. 1 but to an enlarged scale; Fig. 4 is a transverse cross-section along the line IV-W in Fig. 3; Fig. 5 is a part-vertical cross-section, to an enlarged scale, of a joint between two tiles as shown in Figs. 3 and 4 when connected together in the floor; Figs. 6a and 6b are perspective and plan views respectively of a support post for a retaining wall of the bund arrangement as shown in Fig. 1; Fig. 7 is a perspective view of part of the retaining wall supported by a bracket as an alternative to the support post shown in Figs. 6a and 6b; Fig. 8 is a view of part of Fig. 2 but to an enlarged scale and showing the retaining wall supported by a post as shown in Figs. 6a and 6b; Fig. 9 is perspective view showing two corner panels in the retaining wall during the latter's construction; Fig. 10 is a cross-sectional view of a gasket for use in the construction of the retaining wall; Fig. 11 is a perspective view of a chimney for enclosing features of apparatus to be bunded; Fig. 12 is a transverse cross-section through the chimney along the line XII-XII in Fig.ii; and Fig. 13 is schematic perspective view of a sealant arrangement for use in the sealing of the surfaces of the bund arrangement.

As shown in Fig. 1, an embodiment of a modular bund arrangement 1 according to the invention comprises a floor 2 and retaining wall 3. The arrangement 1 shown in Fig. 1 of this example is being used to contain an electricity transformer 4, which includes an oil reservoir 5. The height of the wall 3 has therefore been calculated relative to the floor area of the arrangement 1 so that if the reservoir 5 leaks, all of the oil will be contained within the bund. In practice, the capacity of the bund should meet legal requirements, which means that its capacity must be at least 110% of the capacity of the reservoir. The arrangement 1 is modular so that its shape and configuration can be adapted to suit any particular facility which it is desired to bund. The particular arrangement can then be retrofitted to an existing facility or installed at the same time as the facility is itself installed. Various parts and components of the bund arrangement iwill now be described.

As shown in Fig. 2, the floor 2 comprises a plurality of inter-engaging, non-porous tiles 6 which are laid over a base structure formed by a grid of slabs 7 and beams 8 that is filled with concrete 9 to form a level surface over which the tiles 6 can be laid. The slabs 7 are preferably arranged in a ring around the periphery of the bund 1 and over which the retaining wall 2 is laid. The beams 8 are set into the earth 10 and laid as cross-members at locations which will coincide with the joints between tiles 6, as shown in Figs. 1 and 2. This is to ensure that the tiles 6 remain level with one another.

The tiles 6, slabs 7 and beams 8 are all moulded from thermoplastic materials. In particular, they can be made from recycled plastics material and be comprised of a mixture of low density polyethylene and any of high density polyethylene, polypropylene, acrylonitrite butadiene styrene co-polymers, high impact polystyrene and other thermoplastic materials. These materials are ground, mixed and fused at high temperatures and pressures and then pressed into moulds. The resulting tiles 6, slabs 7 and beams 8 are durable, splinter-free, flexible, shock-proof and do not leach toxic substances. They can also be worked in the same way as wood so that they can be sawn into shape, in particular around the periphery of the floor 2 of an installation.

The tiles 6 can be provided in a range of shapes and sizes but for most installations, tiles 6 which are of the order of 8oo mm square will be used.

Each tile is 50 mm thick but may be recessed underneath, as at ii, to save unnecessary weight and use of materials. The tiles 6 can be interconnected because each is provided along two adjacent edges with an overlap 12 and along the other two adjacent edges with an underlap 13. Two tiles 6 can therefore be lapped together when forming the floor 2, as shown in Fig. 5, to form a solid water-tight structure. In particular, when the tiles 6 are lapped together fasteners 14 are used to secure the lapping portions 12, 13 of the tiles 6. The fasteners 14 preferably comprise self-tapping bolts, for example such as those currently used for roofing with an incorporated washer 15.

Tiles 6 are adapted to accommodate these bolts 14 by providing countersinking 16 for the heads of the bolts 14 at regular intervals along the length of the overlap 12 and pilot holes (not shown) in both the bottom of the countersinking 16 and the underlap 13.

When two tiles 6 are lapped, a sealing membrane 17 is located between the substantially horizontal lapping portion 12, 13 of the tiles 6 through which the fastener passes. In addition, a non-porous sealant 18 is applied to the substantially vertical portions of the lap joint. This sealant i8 can be applied localiy to the lap joints but more preferably the whole surface of the floor, the joint with the retaining wall 3 and the inner surface of the wall 3 are coated with a non-porous sealant arrangement, as is described below with particular reference to Figs. 2 and ii. Such a sealant arrangement provides a better seal than one applied between the joints in the tiles 6 and between the tiles 6 and the retaining wall 6 and can accommodate thermal expansion of the components of the bund arrangement 1 and small structural movements.

The retaining wall 3 is fitted to the floor 2 either by locating it on top of the floor 2, as shown in Fig. 1, once the floor 2 has been laid, or by butting it to the edge of the floor 2, as shown in Fig. 2. In the latter case the retaining wall 3 is erected after the base structure of slabs 7, beams 8 and concrete 9 has been laid but before the tiles 6 are laid. The tiles 6 are then be fitted to the wall 3 rather than the wall 3 being secured through the tile 6.

In both cases the retaining wall 3 comprises a plurality of non-porous, substantially rectangular panels 19 which in one embodiment are supported by support brackets 20, as shown in Fig. 7 and in another embodiment are supported by support posts 21 as shown in Figs. 1, 2 and 6. The panels 19 are laid with their longitudinal axes horizontal one on top of the other to a suitable height and are inter-engaged along their length via tongue and groove arrangements. To this end, each panel 19 comprises a longitudinal groove 22 along its longitudinal edges into which is fitted a tongue 23 that has been manufactured separately from the panel 19. Preferably, the panels 19 are moulded from the same material as the tiles 6, slabs 7 and beams 8, as described above. However, the tongues 22 are preferably comprised of a high density polyethylene and are of the order of ii mm in width, of which 6 mm is inserted into the groove in each panel 19 to form a projecting tongue of 5 mm. Hence, the wall 3 is made up of a plurality of panels 19 which are inter-engaged via the tongues 22. Preferably the upper edge 24 of the uppennost panels 19 in the retaining wall 3 are cut off at an angle to deter persons from standing on them, which may exert forces that could jeopardize the integrity of the bund arrangement 1.

As shown in Fig. 9, adjacent panels 19 along the length of the wall 3 and at the corners of the wall 2 are butted together and a gasket 25 is located in the joint. The gasket 25, which is shown in Fig. 10, comprises an elastomeric gasket that has a double P' cross-sectional shape with two sections 26 of increased thickness. This shape provides a seal against liquids escaping out of the bund arrangement 1 via the retaining wall 3 and against liquid seeping into the bund arrangement 1 through the joint.

As indicated above, the height of the panels 19 required for any particular bund arrangement 1 depends on the capacity of bund required and on its surface area. A typical wall 3 may be four panels 19 high and these can be supported either by the brackets 20 or the posts 21. The brackets 20 are manufactured from 6 mm thick, hot-dip galvanized steel and are triangular, their height being made commensurate with the height of the wall 3 to which they are to be attached so that all of the panels 19 making up the height of the wall 3 are supported. In contrast, the posts 20 are moulded from the same material as the tiles 6, slabs 7, beams 8 and panels 19, as described above. They are of square cross-section with a projecting foot 27 that is adapted to be bolted as at 28 to the slabs 7 laid around the periphery of the bund arrangement. They are also arranged to support all the panels 19 in the height of the wall 3 and also have a sloping upper surface to deter persons from standing on them.

It will be appreciated that as the bund arrangement 1 of the invention is intended to retain liquids within the retaining wall 3, it will also retain rainwater. This must be removed. Preferably, therefore, at least one of the tiles 6 of the floor 2 is adapted to accommodate a prefabricated sump 29 (Fig. 1) for use in liquid removal from the bund arrangement 1. The floor 2 is preferably laid so that liquids drain towards the sump 29, which may be covered by a grating (not shown) and in which is located a pump (not shown) that is connected to the exterior of the bund by a conduit (not shown). Means can also be provided for detecting whether liquid within the suinp comprises oil or water and, in the case of the latter, for operating the pump to evacuate the water to the surrounding area. However, when oil or oily water is detected, then the pump can be prevented from operating and, instead an alarm can be initiated. In this way, the bund arrangement 1 can be kept free of rain water so that in the event of a leakage from the apparatus it protects, the bund is not breached by an excess of liquid.

When installing or retro-fitting a bund arrangement 1 according to the invention, pipework, cables and the like often project from the surface of the area to be covered by the bund arrangement 1. These must be isolated from the bund area and in order to cope with them, the bund arrangement 1 preferably comprises one or more chimneys 30, as shown in Figs. ii and 12, that can enclose them. Each chimney 30 comprises a plastics tube that is fabricated around the existing feature and projects upwards to a height at least commensurate with the height of the retaining wall 3. The walls of the chimney 30, which is preferably rectangular in cross-section, are formed in a similar way to the boards 19 and are connected by similar tongue and groove arrangements 31. The chimney 30 is also adapted to inter-engage with the floor 2 via a tongue and groove arrangement 32, a groove being cut in the appropriate tiles 6 of the floor to accommodate the tongue. In addition, the chimney 30 may be supported by one or more brackets 33, which are each connected to its exterior and to the floor 2.

Once the floor 2, walls 3, sump 29 and chimneys 30 have been built, the interior surface of the bund arrangement is preferably sealed using a non-porous sealant. In particular, the joints between the tiles, the panels 19, and the panels 19 and the floor 2 must be sealed. Any suitable outdoor plastics sealant that is appropriately resistant to water and the type of liquid that the bund is designed to retain can be used for this purpose. Preferably, however, the sealant comprises an elastomeric polyurethane coating that is cold-applied and incorporates a moisture-triggered curing system. Such a sealant forms a seamless, durable, waterproof barrier that is resistant to rainfall and ponded water. Preferably, the whole surface of the floor 2 and the inner surfaces of the retaining wall within the bund arrangement 1 are sealed. One preferred form of sealant arrangement is as shown in Fig. 13 and comprises a felt mat 34, which is laid over the floor 2, the inner surfaces of the retaining walls 3 and the outer surfaces of any chimneys 30, and over which is spread base and top coats, 35 and 36 respectively, of an elastomeric polyurethane coating such as is sold under the registered trade mark DECOTHANE by Liquid Plastics Limited. A scrim tape 37 may be applied between the base and top coats 35 and 36 to provide local reinforcement of the coating over joints and to bridge any gaps. Preferably this tape is a woven reinforced nylon tape that is capable of stretching with the sealant to accommodate thermal and structural movements in the bund arrangement 1.

A termination strip may also be used at the top edges of the sealant arrangement near the top of the retaining wall 2.

When a bund arrangement i according to the invention is to be installed, for example around an existing piece of apparatus such as the electricity transformer 4 and oil reservoir 5, the ground around the apparatus is leveled over the area where the floor 2 is to be laid. The apparatus 4, 5 is often seated on a concrete plinth 38, as shown in Fig. 2. In these circumstances, the ground io around the plinth should be excavated to a level such that the surface of the base structure of the floor 2 that comprises the grid of slabs 7 and beams 8 and that is filled with concrete 9 is level with the top surface of the plinth 38. This base structure is then laid, making appropriate arrangements for an outlet for the sump 29. Then either the wall 3 is built and the tiles 6 are laid and fitted to it or the tiles 6 are laid and the wall 3 is built over tiled floor 2. In either case the tiles 6 are laid around the apparatus 4, 5 and stop short of covering the plinth 38. The tiles 6 are laid as described above and chimneys 30 are also built where appropriate. The sump 29 can then be fitted and connected to the exterior of the bund area. The area above the plinth 38, which has a lower level than the upper surface of the tiles 6 can then be filled in with a self-levelling polymer screed 39 up to the top surface of the tiles 6. This screed will cure and set to form a seal with the floor 2 and at the same time isolate and seal the plinth 38. Thereafter, the interior of the bund 1 can be sealed, preferably using a sealant arrangement 40 as described above. The bund arrangement i is then secure and can retain liquids within it.

It will be appreciated that the modular bund arrangement of the present invention has several advantages. First, it can be manufactured almost exclusively from recycled materials, making it environmentally friendly and economical to manufacture. It is readily installed, either as a retro-fit around an existing facility or when a new facility is being installed.

Also, although primarily designed as a bund to retain liquids that leak or spill from the facility itself, it will provide a defensive wall to keep floodwater away from any facility around which it is fitted. This can be advantageous for electricity transformers, pumping installations and the like that are located in areas liable to flooding. The bund arrangement can be fitted without any -10 -specialized plant or tools being required and with minimal ground penetration. This keeps the cost of site preparation low. It can also be installed by workmen with traditional paving skills so that specialist workmen are not required. This also keeps labour costs to a minimum. Once fitted, the bund arrangement is hard-wearing and has a low on-going maintenance cost.

Claims

-11 - CLAIMS

1. A modular bund arrangement induding a floor comprising a plurality of inter-engaging, non-porous tiles; a retaining wall comprising a plurality of non-porous panels supported by brackets or posts; and wherein joints between the tiles, the panels and the panels and the floor are sealed by a non-porous sealant.

2. An arrangement as claimed in Claim i, wherein the floor and inner surfaces of the retaining wall within the bund arrangement are coated with a non-porous sealant arrangement

3. An arrangement as claimed in Claim 2, wherein sealant arrangement comprises a mat that is laid over the floor and the inner surfaces of the retaining wall and over which is spread one or more coats of a non-porous sealant.

4. An arrangement as claimed in any of Claims 1 to 3, wherein the non-porous sealant comprises an elastomeric polyurethane coating.

5. An arrangement as claimed in any of Claims 1 to 4, wherein a plurality of the tiles comprise rectangular tiles which are provided along two adjacent edges with an overlap and along the other two adjacent edges with an underlap in order that these tiles lap together when forming the floor.

6. An arrangement as claimed in Claim 5, wherein fasteners are used to securing lapping portions of the tiles.

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7. An arrangement as claimed in Claim 6, wherein the head of each fastener is countersunk into the overlap of the lapping portions of the tiles.

8. An arrangement as claimed in Claim 6 or Claim 7, wherein a sealing membrane is located between the substantially horizontal lapping portions of the tiles through which the fastener passes.

9. An arrangement as claimed in any of Claims 5 to 8, wherein a non-porous sealant is located in substantially vertical portions of the lap joint between two lapping tiles.

10. An arrangement as claimed in any of Claims 1 to 9, wherein the retaining wall and tiles are laid over a base structure comprising a grid of slabs and/or beams that is filled with concrete to form a level surface.

ii. An arrangement as claimed in Claim io, wherein the base comprises a ring of slabs arranged in a ring around the periphery of the arrangement and over which the retaining wall is located.

12. An arrangement as claimed in Claim 10 or Claim ii, wherein the beams are set into the earth 10 and laid at locations which coincide with joints between tiles.

13. An arrangement as claimed in any of Claims i to 12, wherein the tiles and/or the panels are comprised of a mixture of low density polyethylene and any of high density polyethylene, polypropylene, acrylonitrite butadiene styrene co-polymers, high impact polystyrene and other thermoplastic materials.

-13 -

14. An arrangement as claimed in any of Claims i to 13, wherein the retaining wall comprises a plurality of substantially rectangular panels that inter-engage along their length.

15. An arrangement as claimed in Claim 14, wherein the panels are inter-engaged by a tongue and groove arrangement.

16. An arrangement as claimed in Claim 15, wherein the tongues of the tongue and groove arrangement are manufactured separately from the panels and are located in grooves define in the longitudinal edges of the panels.

17. An arrangement as claimed in Claim 15 or Claim 16, wherein the tongues are substantially comprised of high-density polyethylene.

18. An arrangement as claimed in any of Claims 1 to 17, wherein adjoining panels along the length or at corners of the wall are butted to one another, a gasket being located in the joint between the panels.

19. An arrangement as claimed in Claim 18, wherein the gasket is an elastomeric gasket that has a double P' cross-sectional shape

20. An arrangement as claimed in any of Claims 1 to 19, wherein at least one of the tiles of the floor is adapted to accommodate a sump for use in liquid removal from the bund arrangement.

21. An arrangement as claimed in Claim 20, wherein a pump is located in the sump and is connected to the exterior of the bund by a conduit.

22. An arrangement as claimed in Claim 21, wherein means are provided for detecting whether liquid within the sump comprises oil or water and for operating the pump when only water is detected within the sump.

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23. An arrangement as claimed in any of Claims 1 to 22, wherein one or more chimneys are provided enclosing features of the apparatus, the chimneys inter-engaging with the floor and projecting upwards to a height at least commensurate with the height of the retaining wall.

24. An arrangement as claimed in Claim 23, wherein the or each chimney inter-engages with at least one tile of the floor via a tongue and groove arrangement and is sealed thereto by a non-porous sealant.

25. An arrangement as claimed in Claim 23 or Claim 24, wherein the or each chimney is supported by at least one bracket which is connected to its exterior and to the floor.

26. An arrangement as claimed in any of Claims 23 to 25, wherein walls of the chimney comprise a plurality of panels which are interconnected via a tongue and groove arrangement and sealed by a non-porous sealant.

27. A modular bund arrangement substantially as described herein with reference to the accompanying drawings.