Tank having upper and lower collars connected by overlapping edges

FIELD OF THE INVENTION

5 This invention concerns storage tanks inter alia for liquids and methods for their construction.

BACKGROUND OF THE INVENTION

Q Farming generates large tonnages of cereals and nuts which require dry storage. Silos are

commonly the building of choice.

Factories, food processing plants, plating works, mines and other production plants commonly have an onsite water tank standing on a concrete base. The capacity of such tanks varies from about 40O ₅ OOO-IO ⁶ litres. The tanks may have a flexible liner but usually not. They are made of galvanised sheet steel 1.5 -3mm in thickness depending on the height of the tank. In a known method of construction, the tanks are fabricated from panels 2400 x 1200mm. The borders are perforated and the panels are overlapped and secured by nuts and bolts.

Tanks may contain thousands of nut and bolt fasteners. Accordingly the greatest cost component is the labour required for the repetitive connections.

SUMMARY OF THE INVENTION

The apparatus aspect of the invention provides a storage tank inter alia for liquids comprising an upper collar closed by a cover and a lower collar which is connected to the upper collar by their mutually overlapping circumferential edges.

There may be more than two collars arranged each higher than the one below in order to reach the required height. The collars may be made from one long strip of sheet metal. Alternatively and less desirably the collars may be made of two strips of metal joined end to end. The tank made of one piece collars afford the greatest labour savings. Savings arise because even though the same number of horizontally disposed fasteners are required, a smaller number of vertically disposed fasteners suffice. Making the tank from collars rather than multiple panels has constructional benefits also.

The method aspect of this invention provides a method of fabricating a liquid storage water tank comprising making a first collar by joining the ends of a strip covering the first collar, elevating the first collar and optionally a cover, forming a second collar beneath the first collar by joining the edges of a strip, overlapping the circumferential edges of the first and second collars connecting the mutually overlapping edges of the first and second collars and optionally elevating the first and second collars in order to add a further

collar.

Elevation may be achieved by inserting rams around the periphery of the collar. The rams may react against the cover. The rams may be single lift or telescopic.

The second collar may be formed by feeding the leading end of the strip through a ring of guide assemblies fixed to the ground in the shape of the tank perimeter.

The guide assemblies may each have a pair of upright guides through which the strip passes and a roller which supports the strip edge clear of the ground.

Elevation may be achieved by engaging the perimeter of one of the collars and extending the rams.

A strip of gasket material may be interposed between the rows of bolt holes. Preferably this is a resilient polyurethane foam band with a face made adhesive with a coating of contact adhesive. This is laid flush with the edge of the strip covering the bolt holes. Provision of a gasket is not essential. When the tank is to store water, a waterproof liner is commonly installed.

Although sheet steel in coil form is obtainable in many different widths, we prefer 1200- 1800mm. Larger widths increases handling difficulties.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is now described with reference to the accompanying drawings, in which:

Figure 1 is a plan of a strip for forming a collar.

Figure 2 is a plan of the strip of Figure 1 following perforation in the factory.

Figure 3 is a side view of a ground roller and guide for the strip.

Figure 4 is a plan of six ground rollers arranged in a circle to form a strip into a collar.

Figure 5 is a perspective of a strip joined end to end standing on the ground rollers.

Figure 6 is a perspective of the collar of Figure 5 with a cover support applied thereto.

Figure 7 is a perspective of the collar with a cover in position.

Figure 8 is a side view of a ram and hanger.

Figure 9 is a perspective of the collar and cover of Figure 7 with a trio of rams assembled to permit elevation.

Figure 10 is a perspective of the elevation of the first collar and the formation of the second collar beneath the first collar.

Figure 11 is a part sectional view of the top, middle and bottom collars and the nut and bolt fasteners.

Figure 12 is a perspective of the part formed tank ready to receive the bottom collar.

Figure 13 is a perspective of a fragment of the tank receiving the split ring for base attachment.

DETAILED DESCRIPTION WITH RESPECT TO THE DRAWINGS

Referring now to the drawings, Figure 1 shows a 2mm strip 2 of galvanised steel 1200 x 30m docked from a coil. The strip is fed through a flat bed laser cutter which is CNC programmed to cut a double row of bolt holes 4 at both ends and a single row along each longer edge.

hi Figure 2 each bolt hole is a slot 6, 12mm deep with arcuate ends 8 and is 15mm long. The bolt holes are separated by 115mm. If the tank is to be three collars high (see Figure

11), two collars 10, 12 are perforated at this spacing and the third middle collar 14 at slightly larger spacing because it occupies a central position overlapping the upper and lower collars and is therefore of slightly larger diameter. The perforator is programmed to cut two straight rows of bolt holes exactly 1120mm apart so that if the edge of the strip is not quite straight, the wavy edge extending over 20-50 metres will not spoil the mutual registration of the two rows of bolt holes.

The strips are preferably prepared in a machine shop off site and freighted to the site together with a lower ring 16 and an upper ring 18 (see Figure 6) made of angle section. One is for connection to the concrete base 20 in the standing position of the tank, while the other is intended for connection to the topmost collar 10 in order to assist in roof support.

Referring to Figures 3, 4 and 5, at the site the lower ring 16 is used to mark the circumference of the tank and six wheel assemblies 22 are bolted to the concrete base in a circumferential path. The assemblies each comprise a metal base 24 made of lengths of square steel tubes to which mounting brackets 26 are welded. The brackets support a shaft 28 and a nylon roller 30 with the cross section of a bobbin. A pair of tubular guides 32 about 600mm high extend from the base about 150mm apart. The operators flex the strip 2 into a curve by following the circumference and overlap the two ends to form a collar 10. A strip of gasket foam 36 (see Figure 11) is placed between the overlapping ends. The gasket foam is adhesive on one face. A bolt 38 is forced through each pair of mutually registering bolt holes and the intervening gasket and a nut 40 is applied. The gasket punctures easily and seals the hole.

Referring now to Figures 6 and 7, the roof assembly comprises a central diametric beam 42 with C-section purlins 44 spanning the semicircular space between the beam and the L-section ring. In Figure 7, a dome or conical lid 46 is attached to the purlins to prevent access to the tank interior. The collar rests on the wheel assemblies. The upper ring 18 projects from the collars as shown in Figure 6.

Referring now to Figures 8 and 9, a trio of rams 48 are arranged around the perimeter of the collar 10 at an inclination of about 80°. Each ram has a baseplate 50 which is bolted

to the base 20 outside the circle indicated by the wheel assemblies. Each ram 48 has a sliding hanger 52 which extends between head 54 and sleeve 56. When the ram is retracted, the head engages the upper ring 18 and is able to lift the collar and cover to the position shown in Figure 10. The hanger has a pair of inwardly projecting pins 58 for engaging the second and subsequent collars. In a variant, the hanger has a pair of bores through which bolts protrude.

The middle strip 14 is stood upright by the operators and the leading end is lifted onto the wheel of the first assembly 22 and threaded between the pair of guides 32.

The second strip is joined end to end to form the middle collar 14 lying directly beneath the first collar. The jacks lower the first collar to register with the middle collar. The circumferential edge of collar 10 fits inside the edge of the middle collar so that the bolt holes register. The collars are bolted together and the jacks raise both collars in preparation to receive the third strip to form the third collar as shown in Figure 12.

The 10mm bolts and nuts are shown in Figure 11. Each bolt 38 has an integral washer 60. Each nut 40 also has an integral washer 62. The operator punctures the gasket with the bolt. The punctured gasket grips the bolt and allows the operator to apply the nut without assistance from a partner. This allows a two man team to progress rapidly around the collar. When the nut is finger tight, the nut is tightened from one side only. The friction of the contacting surfaces and the resilience of the gasket is sufficient to permit a tightening tool to tighten the nut from one side using a portable drill type spanner.

In Figure 13, the tank stands on the lowermost collar on the concrete base 20 or on a raised steel platform a few centimetres deep. The lower ring 16 is offered up in two or more parts. The ring parts have bolt holes in the upright flange and the horizontal flange. The upright flange is bolted to the collar. The horizontal flange is bolted to the concrete or the platform.

The tank is then finished in known manner and the lowermost collar is bored to receive the bolts of an outlet fitting through which liquid is removed. A liner is installed and the

outlet is sealed to the outlet fitting in known manner. If the tank is to function as a silo, a powered auger is installed in known manner. It is convenient to install the cover support and the cover when the first collar is formed because the structure is close to the ground. The cover can be added at any later stage.

At the site the cast concrete base 20 is capable of taking the weight of water or cereal to be stored in the tank. Cereals have an average density of 1.4. The tank itself may only add a further 1-2.5 tonnes. For multi-collar constructions, telescopic rams are used.

We have found the advantages of the above embodiment to be:

1. The tank is economical to build in terms of components.

2. Construction time is shorter than the tanks built from plates.