AU2003231622B2 - A Water Tank Having a Mesh Sidewall - Google Patents

Description

A WATER TANK HAVING A MESH SIDEWALL FIELD OF THE INVENTION This invention is directed to a water tank and is particularly directed to a large aboveground water tank which is used on farms, properties and in general industry.

BACKGROUND ART Aboveground water tanks are well-known and are typically formed of concrete, steel or plastic. Concrete water tanks are well-known in the marketplace. These tanks suffer from a disadvantage when large aboveground water tanks are required. These large tanks can have a diameter of over 5 m and a height of over 2 m and can hold between 10,000- 450,000 I. It is difficult and expensive to assemble a large concrete water tank from preformed concrete shell portions or from pouring concrete in situ on-site. Moreover, once the concrete water tank has been assembled or poured, it is difficult if not impossible to disassemble the water tank for transportation to a different site. Concrete tanks suffer from corrosion especially if the tank is filled with bore water. Bore water can be extremely heavy with minerals and this can result in corrosion of the concrete wall. For instance, if the concrete contains a relatively high level of iron, rust can develop inside the concrete tank. For this reason, it is sometimes known to line the inside wall of a concrete tank with a thin flexible plastic liner. Another disadvantage with concrete tanks is that the tanks are extremely rigid and are therefore prone to cracking and leaking with ground movement. That is, the tanks cannot compensate for any ground movement which can occur as the water content in the ground varies.

Plastic water tanks are known. These tanks are suitable for smaller volumes but are not particularly suitable for larger tanks due to the enormous loads placed on the plastic wall by the weight of the water. Water tanks made entirely of plastic are also more susceptible to damage. For instance, plastic moulded water tanks are prone to cracking and leaking and have been known to crack during transport to location.

Metal water tanks are known and extremely common. The water tank is typically made of metal sheets which are attached together to form a cylindrical tank. These tanks can be made quite large. The metal sheets are typically corrugated or otherwise profiled to provide strength. The metal sheets of the older style tanks are typically galvanised to provide corrosion resistance. More recent metal water tanks have metal sheets which have been painted or otherwise treated to provide corrosion resistance. In practice, and especially with bore water, it is common to line the metal water tank with a flexible plastic sheet in order to prevent corrosion of the inside wall of the metal tank and to prevent tainting of water in the tank. It is found that painting and galvanising are not sufficient to prevent corrosion. One advantage of a metal water tank made of metal sheets is that relatively large tanks can be made on-site with reduced transportation cost as the metal sheets are much easier to transport and handle then preformed concrete shells. Moreover, it is possible to disassemble such a water tank for relocation.

In summary therefore the most versatile manner to form a large aboveground water tanks is a combination of metal sheets and a thin flexible metal liner to protect the inside of the tank, and to prevent the water from becoming tainted.

One major disadvantage with lined metal water tanks is that corrosion occurs between the metal wall and the plastic liner. This corrosion is not visible to the naked eye and can result in substantial corrosion and weakening of the tank over time. Another disadvantage is the cost in manufacturing a large aboveground metal tank from continuous metal sheets.

A known aboveground water tank comprises an outer wall which comprises vertical posts and a wire mesh sidewall. A collapsible flexible plastic bag is positioned within the outer wall. The flexible bag contains semi rigid ribs fixed to the sidewall of the flexible bag such that the bag can collapse inwardly. The ribs prevent the bag from crumpling and prevent folds of material being trapped when the bag is refilled. The collapsible bag is not attached to the top of the outer wall as it needs to collapse.

Smaller plastic/metal roof tanks are known which contain a relatively rigid inner plastic wall or liner. The wall or liner is substantially self supporting because the tanks are not particularly large. As a precaution, it is known to provide a surrounding protective cage, and this cage can be made of metal panels, metal mesh, or the surrounding protective cage can be made of horizontal metal bands.

It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

OBJECT OF THE INVENTION The present invention is directed to an aboveground water tank which may at least partially overcome some of the above-mentioned disadvantages and/or provide the public with a useful or commercial choice.

In one form, the invention resides in a water tank, the water tank comprising a sidewall and an internal liner, the sidewall comprising a plurality of panels which are attached together to form the sidewall, at least one panel having a mesh portion, the internal liner being attached to an upper part of the sidewall.

The water tank is particularly suited for outdoor use and to hold between 80,000-200,000 I of water although smaller and larger tanks can also be fabricated.

The sidewall is made of a plurality of panels which are attached together. Each panel may have the same size as each other panel although it is also envisaged that some side panels may be larger and other side panels may be smaller. It is envisaged that a typical side panel will have a length of between 1-4 m and a height of between 1-4 m.

The number of side panels can vary to suit the size of the formed water tank. Typically, between 3-8 side panels are attached together to form a cylindrical water tank. In a preferred embodiment, the water tank can be formed of 4 side panels attached together.

It is envisaged that each side panel or at least some of side panels will be curved. For longer side panels, the panels may be formed flat and bent into a curved shape when the tank is being assembled.

The side panels may be substantially rectangular and may comprise a surround frame comprising a pair of vertical frame members and an upper and lower horizontal frame member. These frame members may be attached to each other to form a peripheral frame. Typically, the vertical frame member comprises a post which has a first face and a second face which are angled relative to each other and which are preferably at right angles relative to each other. Thus, it is preferred that the vertical frame member is L-shaped. The vertical frame member may have a length of between 1.5-4 m and in an embodiment has a length of 2.5 m. For longer frame members, the frame member may be formed from shorter frame members which are attached together (for instance by welding or bolting) to form the longer frame member. Intermediate strut members may be provided to provide additional strength to the side panel.

The upper horizontal frame member and the lower horizontal frame member may comprise metal plates. These metal plates may have a length of between 1.5-6 m, a width of between 20-200 mm and a thickness of between 2-5 mm.

A mesh is typically attached to the surround frame. The mesh may comprise a metal mesh and typically comprises a metal mesh formed of a first series of metal rods extending in a horizontal direction and a second series of metal rods extending in a vertical direction, the rods being welded together to form the metal mesh. This type of mesh is well-known. The thickness of the mesh rods may vary depending on the size of the tank. The rods are typically cylindrical and may have a diameter of between 5-20 mm although this can vary to suit. Although the rods are typically cylindrical, the rods may also have a rectangular cross-section, an oval cross-section and the like. The rods are typically solid metal rods but may comprise strong metal tubes. The mesh may also comprise a woven mesh providing that such the mesh provides the required strength to the panel.

The mesh size (the spacing between the rods) can vary depending on the size of the tank. A typical mesh size will have a spacing of between 50-200 mm between adjacent rods. The mesh shape typically defines rectangular openings although the mesh may be formed to define openings of different shapes.

It is envisaged that the water tank may comprise panels formed of different types of mesh. For instance, one panel may comprise a "stronger mesh". Alternatively, a side panel may comprise two different types of mesh in the same panel. For instance, a side panel my comprise an upper area having a mesh of larger opening size and a lower area having a mesh of smaller opening size. Alternatively, a side panel may comprise a lower area having a mesh formed of thicker rods and an upper area having a mesh formed of thinner rods. In yet further alternative, a side panel may comprise a second layer of mesh extending over the first layer of mesh. The second layer of mesh may extend about a lower part of the sidewall or about any other part of the sidewall. Multiple layers of mesh are also envisaged.

The mesh is typically fastened to the vertical members and as the mesh is typically a metal mesh, it is preferred that the mesh is welded to the vertical members. It is also preferred that the mesh is welded to the upper horizontal member and to the lower horizontal member to provide a good strong rigid side panel.

Adjacent side panels are preferably attached using separate fasteners to allow the panels to be decoupled if required. Thus, each vertical member may be formed with an array of spaced apart openings to accept a plurality of fasteners thereby allowing adjacent vertical members to be bolted together at a plurality of positions to provide a good strong connection.

The liner is typically formed of a plastic material which is thicker and stronger than the thin flexible plastic liners found in concrete water tanks and in metal water tanks. Suitably, the liner has a thickness of 1 mm and preferably has a thickness of between 1.5-5 mm and most preferably has a thickness of about 2 mm. It is preferred that the liner is made of a polyethylene material and a particularly preferred polyethylene material is high density polyethylene (HDPE). The liner typically comprises sheet material which is cut to shape. The liner typically comprises rectangular sheets and the sheets are typically cut to form the sidewall and the bottom wall. The sheets are attached together in a waterproof manner. In one form, this can be achieved by plastic welding the sheets together although other attachment means are envisaged including the use of adhesive, fasteners, intermediate layers, and the like.

To manufacture a water tank according to the present invention, a flat base is initially prepared on the ground surface and it is typical to provide a layer of sand or other suitable material on which the tank will sit.

The side panels are then attached together to form the outer wall of the tank.

The liner can then be placed inside the tank and welded to form a waterproof liner and the liner can be attached to the top horizontal frame member. If required, one or more pipes or other types of inlets/outlets can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will be described with reference to the following drawings in which: Figure 1. Illustrates a water tank according to an embodiment of the invention.

Figure 2. Illustrates an exploded view of the water tank according to Figure 1.

Figure 3. Illustrates a vertical side member of a side panel.

Figure 4. Illustrates in greater detail the top portion of the vertical side member of Figure 3.

Figure 5. Illustrates in greater detail the bottom portion of the vertical side member of Figure 3.

Figure 6. Illustrates in plan view attachment of 2 side panels to each other.

BEST MODE Referring to the figures and initially to figure 1 and figure 2 there is illustrated an above ground water tank 12. In the particular embodiment, the water tank is cylindrical having a diameter of approximately 7.6 m and therefore having a circumference of approximately 25 m. The water tank is made from 4 side panels 13-16. Each side panel has a length of about 6 m and a height of about 2.5 m. Each side panel is made predominantly of steel mesh and has a peripheral metal frame to which the mesh is welded.

Specifically, each side panel has two vertical frame posts 3 each post being made of steel which is galvanised and being L-shaped in configuration. Each side panel has an upper horizontal member 2 and a lower horizontal member 2, each member is identical and formed of steel plate having a width of 100 mm and a thickness of 6 mm. The members are also galvanised.

The metal mesh is formed of steel bars which are welded together at right angles to form the metal mesh. In the particular embodiment, the mesh is a SL62 mesh. The peripheral edge of the mesh is welded to each vertical post and to the upper and lower horizontal members.

The welding is such that the top edge of the upper member does not contain mesh the reason for which will be described in greater detail below. In the particular embodiment each mesh panel is formed from 2 mesh sheets being an upper sheet having a larger opening and a lower sheet having a smaller opening. This provides additional reinforcement to the lower part of the water tank. However, this particular arrangement is according to an embodiment only and is not meant to be limiting to the invention. For instance, a water tank can be made having a single mesh sheet of a single opening size.

In the particular embodiment, each side panel is pre curved to approximate the shape of the formed water tank. However, this may not be necessary for larger water tanks and for larger water tanks, relatively flat panels could be bent to shape on site.

Figure 3 illustrates a particular vertical frame post. The frame post 3 is L-shaped and is formed from galvanised steel. The frame post in the embodiment is a 65L65 X 6 X 2500 frame post. The frame post is provided with a number of spaced apart openings to allow adjacent frame posts to be bolted together.

Figure 4 shows greater detail of the upper part of frame post 3.

In particular, there is illustrated attachment of the mesh 5 against one side face of the frame post 3. The top horizontal end plate 2 is welded to the upper part of frame post 3 in such manner that the upper edge of the top

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horizontal end plate 2 projects above the uppermost part of frame post 3.

This allows a protective plastic tube 1 to be fitted over the upper edge of the top horizontal end plate 2. The plastic tube 1 is a 75 mm PVC tube which has been slit to allow it to be pressed fitted over the free edge of end plate 2.

Figure 5 shows greater detail of the lower part of frame post 3.

Again, the lower horizontal end plate 2 has been welded to frame post 3 to provide a strong surround frame and to confine the bedding sand to within the tank walls. The steel mesh 5 has been welded to this horizontal end plate 2 as well and is to the frame post 3.

Referring to figure 6, there is illustrated a plan view showing two frame posts 3 bolted together via an array of bolts 4.

Inside the water tank is a plastic liner 8. In the particular embodiment, the plastic liner is relatively thick compared to plastic liner is fitted into concrete tanks or steel tanks. The plastic liner is a 2 mm thick high density polyethylene liner which is somewhat bendable but is much less flexible than the thin liners formed in concrete tanks or steel tanks. The polyethylene liner needs to be cut and fitted to form a waterproof liner. In the embodiment, the liner is cut to shape and the shapes are overlapped at their edges and plastic welded to form a waterproof liner. For instance, the side wall of the liner is cut such that the upper edge is adjacent the top of frame post 3 but the lower edge extends beyond the bottom of frame post 3 and therefore is bent into a substantially horizontal position to form part of the bottom wall of the liner. The main body of the bottom wall is formed separately and is overlapped against the substantially horizontal portion and these portions are welded to form a waterproof liner.

Referring to figure 4, the plastic liner 8 is attached to an upper part of frame post 3 via a liner clamping plate 6. Plate 6 is bolted to frame post 3 and liner 8 is sandwiched between plate 6 and frame post 3. A bolt 7 fastens plate 6 to frame post 3.

To assemble the water tank, the panels are transported to site and are assembled by bolting each panel to an adjoining panel through holes in the frame posts 3. All metals including bolts nuts and washers are galvanised Approximately 50-100 mm of sand or other suitable material is placed on the floor inside the tanks to cushion and to protect the liner. The liner is placed and welded inside the tank wall and is attached to the strip of flat bar 6 on the top inside face of the tank using galvanised self tapping roofing screws and washers. Pieces of poly pipe are passed through the liner at specific locations and are welded to the liner to form watertight outlets/inlets and/or overflow pipes. A small length of galvanised steel pipe is welded to a galvanised piece of plate which is then attached to the mesh on the outside of the tank. The poly pipe is passed through the galvanised pipe to prevent accidental bumping of the poly pipe causing damage to the watertight weld.

It is found that the water tank according to the invention is more cost-effective then steel panel tanks and plastic tanks. There is less chance of corrosion of steel parts as moisture is not trapped between steel panels and the liner. The mesh allows any moisture to drain or evaporate. The water tank does not crack or split should some ground movement further.

The water tank is predicted to have a longer life and steel tanks or plastic moulded tanks. The water tank can be easily transported and erected in remote locations. The high density polyethylene liner can tolerate bore water containing aggressive minerals which in the past have corroded concrete tanks and steel tanks. By having the liner relatively thick, the liner can tolerate bore water reaching temperatures of up to 80 degrees centigrade which is not possible with the lined concrete tanks and lined steel tanks. By having the liner manufactured from high density polyethylene, the liner is made from the same material as popular plastic pipe and therefore the plastic pipe can be welded directly to the liner to form a waterproof seal around outlets, inlets and overflow pipes.

It should be appreciated that various other changes and modifications can be made to any embodiment described without departing from the spirit and scope of the invention.

Claims (5)

1. A water tank comprising a sidewall and an internal liner, the sidewall comprising a plurality of panels which are attached together to form the sidewall, at least one panel having a mesh portion, the internal liner being attached to an upper part of the sidewall.

2. The tank as claimed in claim 1, wherein each panel is substantially rectangular and comprises a surround frame.

3. The tank as claimed in claim 2, wherein the surround frame comprises a pair of vertical frame members, an upper horizontal frame member and a lower horizontal frame member.

4. The tank as claimed in claim 3, wherein each vertical frame member is substantially L-shaped and has a length of between 1.5-4 metres. The tank as claimed in claim 3 or claim 4, wherein the upper horizontal frame member and the lower horizontal frame member comprise metal plates having a length of between 1.5-6 metres, and a width of between

20-200 millimetres. 6. The tank as claimed in any one of the preceding claims wherein the mesh comprises a metal mesh. 7. The tank as claimed in claim 6, wherein the metal mesh comprises welded rods. 8. The tank as claimed in any one of claims 3-7, wherein the mesh is attached to each vertical frame member. 9. The tank as claimed in any one of claims 3-8, wherein the mesh is attached to the upper horizontal frame member and the lower horizontal frame member. The tank as claimed in any one of the preceding claims wherein the panels are attached to each other. 11. The tank as claimed in claim 10, wherein each vertical frame member is formed with an array of spaced apart openings to accept a plurality of fasteners thereby allowing adjacent vertical members to be bolted together at a plurality of positions. 12. The tank as claimed in any one of the preceding claims, wherein the liner comprises a plastic liner. 13. The tank as claimed in claim 12, wherein the liner comprises polyethylene having a thickness of between 1-5 millimetres. 14. The tank as claimed in claim 13, wherein the liner is made of high density polyethylene. The tank as claimed in any one of the preceding claims wherein the liner comprises a plurality of sheets which are joined together. 16. The tank as claimed in claim 15, wherein the sheets are formed of plastic and are joined together by plastic welding. 17. The tank as claimed in any one of claims 3-16, wherein the liner is attached to the upper horizontal frame member. 18. The tank as claimed in any one of the preceding claims, wherein each panel member has a length of between 1-4 metres and a height of between 1-4 metres. 19. The tank as claimed in any one of the preceding claims comprising between 3-8 panel members A tank substantially as hereinbefore described with reference to the accompanying drawings. Dated this 6 th day of August 2003 Australian Lining Company Pty Ltd By their Patent Attorneys CULLEN CO.