GB2352761A

GB2352761A - A multi-chamber tank and method of producing same

Info

Publication number: GB2352761A
Application number: GB0012462A
Authority: GB
Inventors: William Kiely
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-05-24
Filing date: 2000-05-24
Publication date: 2001-02-07
Anticipated expiration: 2020-05-24
Also published as: IE20000394A1; GB0012462D0; IES20000395A2; GB2352761B

Abstract

A tank body 1 has a base (fig 2 and 3), a cylindrical external wall 2, and internal walls 4, 5 and 6 defining chambers 15, 16,17 and 18. The tank body 1 is produced with integral moulding of all parts. A mould (fig 4) is gradually filled with a concrete mix having a water: cement ratio of 0.18 to 0.25 by weight. The mould may be removed afterwards.

Description

2352761 "A multi-chamber tank and method of moducing same" The invention

relates to multi-chamber tanks for underground use such as tanks for waste water treatment systems.

At present, such tanks are available in a variety of different types and there are mag different associated production methods. One type of tank is producedin situ using blockwork and/or concrete formers. However, this approach is quite timeconsuming and it is difficult to guarantee integrity of joints.

It is also known to pre-cast components of a tank such as described in United States Patent Specification No. US5544460 (Fife). Post-tension cables are routed through chase ways and are tightened to compress the compartments together so that they act as one integral unit. It appears that this tank is relatively complex and difficult to 15 install.

In another development, a sealed component has been developed for use in walls of poured concrete tanks, as described in United States Patent Specification No. US5711536 (Tuf-Tite). Again, it appears that this arrangement leads to additional 20 complexity and expense.

Another type of multi-chamber tank is of moulded plastics construction. Such tanks do to a large extent overcome the problems of sealing joints of the tank. However, they do not provide as much ground pressure strength as concrete. Also, such tanks 25 are prone to degradation over prolonged periods of time.

It is therefore an object of the invention to provide a tank and method bf producing same to overcome these problems.

According to the invention, there is provided a multi-chamber tank body of concrete material having an upright curved external wall, a planar base, and internal upright walls defining chambers.

The curved shape of the external wall may be oval or substantially circular in plan.

In one embodiment, the internal walls are planar.

In another embodiment, the tank body is of integral pre-cast concrete construction.

In one embodiment, the internal walls comprise a primary internal wall extending substantially diametrically and a secondary wall connecting the primary internal wall to the external wall.

In another embodiment, there is a secondary internal wall on each opposed side of the primary internal wall.

In one embodiment, the tank body is opentopped and comprises a rim for receiving a cover or a riser.

The invention also provides a tank body comprising a tank as defined above and a cover.

According to another aspect, the invention provides a method of producing a tank body comprising the steps of.- providing a mould shaped with interconnected cavities defining a base, an upstanding wall, and internal walls; mounting the mould on a vibratory table, vibrating the mould and filling it with a concrete mix during vibration in a gradual manner to fill all cavities, and removing the mould to provide an integral pre-cast tank body having a base, an external wall, and internal walls defining chambers.

In one embodiment, the cavities are filled by a dispenser moving in a horizontal plane to dispense a layer having a depth of less than 75 mm at a time.

In one embodiment, the layer has a depth of less than 50 mm.

In one embodiment, the mix has a water to cement ratio in the range of 0. 18 to 0.25 by weight.

In another embodiment, the mix has a ratio of approximately aggregates 21. 0 cement 4.7: water 1.0 by weight.

In a further embodiment, the tank body is cast upsidedown with the base being formed last, and the mould is removed after turning over.

In one embodiment, the method comprises the further step of forming apertures for liquid flow in the internal walls and the external wall by withdrawing uncured concrete with an actuator.

In another embodiment, the mould is of fabricated steel construction.

In one embodiment, the internal walls comprise a primary internal wall extending diametrically and a secondary internal wall linking the primary internal wall to the external wall.

The invention will be more clearly understood from the following description of some embodiments thereof given by way of example only with reference to the accompanying drawings in which:-

Fig. 1 is a plan view of a tank body of the invention; Fig. 2 is a cross-sectional view in the direction of the arrows II- II in Fig. I of the tank body; Fig. 3 is a cross-sectional view of a riser and a cover for the tank body; and Fig. 4 is a diagrammatic cross-sectional front view of a tank production plant.

Referring to Figs. 1 to 3 a tank body I is of upstanding cylindrical shape having an external carved wall 2 of 75 mm thickness. The external wall 2 has a circular rim 3 providing a seat for a riser such as a riser 30 shown in Fig. 3 or a cover 40, also shown in Fig. 3.

The tank body I is of fully integral pre-cast concrete construction. An integral planar 50 mm primary internal wall 4 extends internally across the diameter of the tank body 1. There are also secondary 50 mm integral planar walls 5 and 6 extending at right angles to the primary internal wall 4 on opposite sides of it. These walls link the primary internal wall 4 to the external wall 2 and so support it to provide excellent strength. An inlet pipe 7 extends through the external wall 2 for inlet flow of sewage, and there is a succession of holes 8, 9, and 10 in the internal walls 5, 4, and 6 respectively for flow of gradually more purified sewage between chambers to an outlet duct I I in the external wall 2. The internal walls and these holes define a primary chamber 15, an anoxic chamber 16, an aerobic chamber 17, and a final clarification chamber 18 withinthe tank body 1. The flow from the inlet to the outlet indicated by the letters A to E inclusive. The body I also comprises an integral concrete base 20 having a thickness of 100 mm. The height of the tank body I is 1.65m.

Because of the overall cylindrical shape and the integral pre-cast construction there is excellent compressive strength. Also, there is no need forin situ work for tasks such as aligning and grouting internal walls. There is also a perfect and robust seal between the different chambers. The arrangement of the internal walls 4, 5, and 6 provides excellent support because the external wall 2 is linked in both directions to 10 the primary internal wall 4. Referring to Fig. 3 the method of production of the tank body I by a productim plant 50 is described. A mould 51 is of fabricated mild steel construction having a plate thickness of 10 mm. 15 The mould 51 is orientated for production of the tank body I upside-down, and is placed on a high-strength vibrating table 52. A primary hopper 55 dispenses a semidry concrete mix onto a primary conveyor 56. The conveyor 56 in turn dispenses the mix into a secondary hopper 57, which in turn dispenses onto a secondary conveyor 20 58. The secondary conveyor 58 is driven to rotate about an axis59 of the mould 51 as indicated by the arrow P so that it gradually dispenses the mix into the mould 51 to initially cast the external wall 2, as illustrated. All the walls are cast by gradually dispensing the mix to form a layer having a depth of less t1an 75 mm and preferably less than 50 mm at any one time until the full height is reached. 25 When the external wall 2 has been formed, the full conveyor/hopper assembly is moved translationally as indicated by the arrow Q to fill the internar walls at the same dispensing rate. The base 20 (uppermost in the mould 5 1) is the last part of the body I to be formed. While the dispensing is taking place the table 52 vibrates the mould 51, and thereby the dispensed mix, to ensure a complete fill without air pockets.

Immediately when the dispensing is complete a ring former is pressed onto the top of the external wall 2 to form the rim 3. A steel pallet is then clamped to the top of mould 51. The whole assembly comprising the mould 51, the filled mix 60, and the pallet is conveyed by an overhead mechanical handling system to a curing location. The handling system up-turns the assembly so that it rests upright with the pallet on the ground. Hydraulically-driven actuators (not shown) mounted on the mould 51 then withdraw the form of the apertures for the inlet 7 and the outlet I I and also the internal apertures 8, 9, and 10.

The mould 51 is then lifted out to reveal the dispensed mix in the shape of the tank body 1. The mix has sufficient strength to retainits shape and it then cures under ambient conditions over a period of 24 hours. It may then be shipped.

The semi-dry concrete mix I has the following composition in a batch of Im' (weight 2400 kg).

Component Weight (kg) 10-12 mm chippings 920 0-5 mm grit 250 plastering sand 720 cement 420 water 90 In this embodiment, the total weight of the tank body 1 is 5.5 tonnes. Ih general, the water content should be in the range of 18% to 25% by weight of the cement content in order to achieve the strength required and to achieve immediate separation of the mould for short cycle times.

It will be appreciated that the method of production provides a very short cycle time as the tank body may be transported immediately to its despatch location and no further handling or production control is required. Also, the method provides a tank body of very high strength and seal integrity, and which requires very little labour for installation. Ail that is required is that the tank body I be transported to thesite and lowered into position. A cover such as the cover 40 is then dropped into position so that it engages the rim 3. A riser such as the riser 30 may be used to bring the top of the full tank to ground level. The required waste water pipe connection are then made, and parts of the inlet pipe 7 and an outlet pipe I I are shown. These may be of conventional PVC material.

The invention is not limited to the embodiments described. For example the process may be used for production of tank bodies other that the tank body 1, such as one having a rectangular shape in plan. The advantages arising from the integral cast construction of the tank body and production efficiency are still achieved.

The invention is not limited to the embodiments described but may be varied in construction and detail within the scope of the claims.

Claims

1. A multi-chamber tank body (1) of concrete material having an upright curved external wall (2), a planar base (20), and internal upright walls (4, 5, 6) defining chambers (15, 16, 17, 18).

2. A multi-chamber tank body as claimed in claim 1, wherein the external wall 2 is substantially circular in plan.

3. A multi-chamber tank body as claimed in claims I or 2, wherein the internal walls are planar.

4. A multi-chamber tank body as claimed in any preceding claim, wherein the tank body (1) is of integral precast concrete construction.

5. A multi-chamber tank body as claimed in any preceding claim, wherein the internal walls comprise a primary internal wall (4) extending substantially diametrically and a secondary wall (5, 6) connecting the primary internal wall (4) to the external wall (2).

6. A multi-chamber tank body as claimed in claim 5, wherein there is a secondary internal wall (5, 6) on each opposed side of the primary internal wall (4).

7. A multi-chamber tank body as claimed in any preceding claim, wherein the tank body is open-topped and comprises a rim (3) for receiving a cover (40) or a riser (30).

8. A tank body substantially as described with reference to the drawings.

9. A tank comprising a tank body (1) as claimed in any preceding claim and a cover (40).

10. A method of producing a tank body comprising the steps of.

providing a mould (51) shaped with interconnected cavities defining a base, an upstanding wall, and internal walls; mounting the mould on a vibratory table (52), vibrating the mould and filling it with a concrete mix during vibration in a gradual manner to fill all cavities, and removing the mould to provide an integral precast tank body having a base, an external wall, and internal walls defining chambers.

11. A method as claimed in claim 10, wherein the cavities are filled by a dispenser moving in a horizontal plane to dispense a layer having a depth of less than 75 mm at a time. 20

12. A method as claimed in claim 11, wherein the layer has a depth of less than 50 mm.

13. A method as claimed in any of claims 10 to 12, wherein the concrete mix has 25 a water to cement ratio in the range of 0. 18 to 0.25 by weight.

14. A method as claimed in claim 13, wherein the mix has- a ratio of approximately aggregates 2 1. 0: cement 4.7: water 1. 0 by weight.

15. A method as claimed in any of claims 10 to 14, wherein the tank body is cast upside-down with the base being formed last, and the mould is removed after turning over.

16.A multi-chamber tank body as claimed in any of claims 10 to 15, wherein the method comprises the further step of forming apertures for liquid flow in the internal walls and the extemal wall by withdrawing uncured concrete with an actuator.

17. A method as claimed in any of claims 10 to 16, wherein the mould is of fabricated steel construction.

18. A method as claimed in any of claims 10 to 16, wherein the internal walls comprise a primary internal wall (4) extending diametrically and a secondary internal wall (5, 6) linking the primary internal wall to the external wall.

19. A method substantially as described with reference to Fig. 4.