EP2409936B1

EP2409936B1 - Water tank, method for constructing such a tank and its use

Info

Publication number: EP2409936B1
Application number: EP10170135.7A
Authority: EP
Inventors: Gerrit J. Kruithof
Original assignee: AVASCO IND; Avasco Industries
Current assignee: AVASCO INDUSTRIES
Priority date: 2010-07-20
Filing date: 2010-07-20
Publication date: 2013-10-09
Anticipated expiration: 2030-07-20
Also published as: PL2409936T3; BE1018789A3; EP2409936A1

Description

Field of the invention

The invention relates to a watertight bottom of a steel water tank suitable for storage of sprinkler water for fire prevention. The invention also relates to a method for installing said bottom in a steel water tank.

Background of the invention

Traditionally a steel water tank is installed with a watertight bottom by providing a concrete filling of about 20 cm thick at the bottom inside the tank. A problem arises however when water tanks need to be installed in isolated regions where supply of concrete is a problem. Another problem may be the quality and reliability of the concrete mixture that must resist cracks and be waterproof. In other words, the process of making and the availability of concrete as such can not be controlled fully by the installer. Moreover concrete makes this a costly installation.
Another way of installing a watertight steel water tank is by providing an inner liner, e.g. in rubber. The inner liner covers the entire tank wall of the water tank and reaches up to the top, to above the water level. Such tanks are e.g. described in CH 484 798 A or US 2004/0217118 A1 This solves the problems just mentioned, however there are some major drawbacks. A problem with this type of design is that the water tank starts leaking and becomes useless whenever the liner gets teared or damaged. Another problem is serious corrosion of the tank wall due to condensation between the liner and said wall and due to water vapor permeability.
Corrosion resistance can be enhanced by applying the liner to a lower part of the sidewalls as e.g. described in US 3,545,640 A , DE 298 07 285 U1 , DE 2 202 096 A1 and DE 201 04 828 U1 . A problem with such tanks is however that when leakage occurs, the tank necessarily has to be emptied before the leak can be sealed. Best water resistance can be assured with a water tank as described in DE 298 07 285 U1 , but by welding of bolts to the sidewalls, corrosion resistance again diminishes.
It is therefor an object of the present invention to provide at the same time a cheap and reliable solution for the above mentioned problems, as a solution whereby the installation can be done fully autonomously by the installer, without being dependent on (the quality of) third parties. It is another object of the invention to provide a water tank that is perfectly watertight during the required life span, wherein corrosion resistance is improved and wherein, when leakage occurs the tank not necessarily has to be emptied in order to stop the leak.

Summary of the invention

For this purpose the invention provides a water tank for water storage, comprising sidewalls (1) mounted on a foundation (2) and a membrane (4) covering the foundation and extending upwards onto the inner sidewalls, wherein the membrane only extends up to a lower part of the sidewalls, such that when the water tank is filled with water, the membrane (4) edge ends under the water level, wherein the membrane is applied to the sidewalls by means of a peripheral band of clamping plate, sealing bands being provided between the membrane and the sidewalls and between the membrane and the clamping plate, wherein the clamping plate comprises at least two rows of prepunched holes, extending parallel to the surface of the foundation, wherein the sidewalls comprise corresponding prepunched holes, wherein the sealing bands are made of mastic and are applied at the level of the rows of holes and wherein the membrane is watertightly applied between said inner sidewalls and the clamping plate by means of bolts through the holes and the mastic. The membrane only extends up to a part of the sidewalls, being the part of space necessary for fixing the membrane to the lower part of the inner sidewalls.
The membrane only extends onto a lower part of the sidewalls and does not reach up to the top level of the tank. Because the membrane edge lies under the water level, there is a need for a watertight sealing of the membrane to the tank wall. This watertight sealing is provided by the embodiments of the present invention.
Said two or more rows (I, II) are horizontal, i.e. parallel to the surface of the foundation.
The advantage of the water tank of the invention is that it is cheap, simple, easy, reliable and fast to install. Furthermore the water tank is perfectly watertight. A mimum amount of membrane material is used. Due to the small thickness of the membrane in comparison with a tank bottom filled with concrete, the height of the tank may decrease for the same capacity (volume) thereby creating a reasonable cost saving. The process of installation solely relies on one installer from start to end.
Thanks to the bolts being applied through prepunched holes in the sidewalls of the tank, the bolts no longer have to be welded to the sidewalls. By welding the bolts to the sidewalls the corrosion resistance of the sidewalls and the bolts deteriorates. When leakage occurs, the tank does not necessarily have to be emptied in order to stop the leak. As the bolts are applied through the sidewalls of the tank and the clamping plate, they can be reached in order to (re)tighten them or to seal the leak otherwise through the holes in the sidewalls.
In order to be able to make the tank watertight with holes through the sidewalls, the membrane and the clamping plate, a double row of bolts is provided and mastic is used as sealing bands.
In a preferred embodiment said membrane (4) extends 10 to 50 cm up onto the sidewalls (1), preferably 10 to 30 cm, or any suitable distance for fixing the membrane to the sidewalls with a fixation means hereby cost-effectively applying only a minimum amount of membrane needed.
In a specific embodiment at least one row of swell seal mastic (7) is provided in an uninterrupted watertight manner between the sidewalls (1) and the membrane (4).
In a specific embodiment a mastic (6) is provided in each hole (5a, 5b) in an uninterrupted watertight manner. A mastic (10) is provided in an uninterrupted watertight manner, between the lower end of the fixation means (8) and the membrane (4), between the upper edge of the fixation means (8) and the membrane (4), and between the membrane upper edge and the sidewalls.
Said clamping plate (8) comprises one or more reinforcing ribs (11) extending out of its surface. In a specific embodiment said reinforcing rib (11) is a bent edge or a seal edge.
In a preferred embodiment said fixation means (8) comprises one or more additional peripheral bands (8) of clamping plates, each band comprising two or more horizontal rows (I, II) of prepunched holes (5b) corresponding to prepunched holes (5a) in the sidewalls.
The membrane (4) is preferably made of EPDM. A protective layer (3) is applied on the bottom between the foundation (2) and the membrane (4) and this protective layer preferably partly extends up to the sidewalls of the tank.
In a specific embodiment a casing (12) holding gravel (13) is provided around the outside bottom of the tank for hiding a bolted (16) L-profile (14) by which the tank is mounted to the foundation (2).
The invention also provides a method for constructing a water tank as described above, said method comprising the steps of: a) mounting the sidewalls (1) of a water tank onto a foundation (2); b) spreading a membrane (4) onto the foundation (2) and extending said membrane up to a lower part of the sidewalls such that when the water tank is filled with water, the membrane extends onto the inner sidewalls to a level under the water level; c) applying an uninterrupted swell seal mastic (7) between the membrane (4) and the sidewalls (1); d) applying an uninterrupted mastic (6) between the membrane (4) and the sidewall (1) at the level of the rows (I, II) of holes (5a); e) applying an uninterrupted mastic (6) between the membrane (4) and a clamping plate (8) at the level of the rows (I, II) of holes (5b); f) fixing the clamping plate (8) to the sidewalls (1) by means of bolts (9) through the holes (5a, 5b) and the mastic (6); g) applying mastic (10) to the edges of the clamping plate (8) and the membrane (4), sealing off any space between the edge of the membrane (4) and the sidewalls (1) and any space between the clamping plate (8) and the membrane (4); and h) optionally providing an outer casing around the bottom of the watertank.
The invention also provides for the use of a sprinkler water tank as described above for watertight storage.
The water tank may be installed on any horizontal surface that is strong and stable enough to support the weight of the tank and the water in it. As such, the water tank may be installed (on a concrete slab) on the ground, but may also be installed on a tower, a roof top or any other supporting means.

Brief description of drawings

Figure 1 shows a sectional view of a cylindrical water tank according to the invention.
Figure 2 shows a photo detail of a water tank construction according to the invention.

Detailed description of preferred embodiments

Figure 1 shows a sectional view of a cylindrical water tank (1) placed on a concrete foundation (2). The tank is mounted level (tolerance of about 10 mm) and secured with anchor bolts into the concrete slab. The water tank is made of galvanized modular steel sheets, assembled with silo bolts and sealed with mastic.
The top surface of the concrete is broomed clean and made free of any parts that could damage the membrane. A protective layer (3) is placed on top of the concrete surface and partly extends up onto the sides of the tank. Examples of protective layers are geotextiles (300 gr/m²) or equivalents.
The membrane (4) is first positioned on top of the protective layer, in the center of the tank, in a specially packed embodiment. It is then opened to cover the bottom of the tank hereby partly extending up onto the sides of the tank, preferably 20 to 30 cm. As such the membrane (4) does not reach above the water level, but ends under the water level, inside the tank. The membrane is preferably made of EPDM (1.2 mm thickness) or equivalents.
The tank wall is provided with prepunched holes (5a) in two horizontal rows (I, II) parallel to the bottom of the tank. A mastic (6) is provided on the inside of the tank in an uninterrupted manner along each of the two horizontal rows (I, II) of prepunched holes. Also in a horizontal row, in between the two horizontal rows of punched holes, a swelling joint with swell seal mastic (7) is applied, also preferably in an uninterrupted manner. The swelling joint may be the same material as the mastic.
The membrane (4) is pressed tightly onto the two rows (I, II) of mastic (6) and the swell seal mastic (7), hereby preventing any leaks of water.
A clamping plate (8) provided with two horizontal rows (I, II) of prepunched holes (5b) is applied on top of the membrane and fixed to the corresponding rows of prepunched holes (5a) in the tank wall. Both rows of holes of the clamping plate (8) are also provided with mastic (6) in uninterrupted horizontal rows.
The clamping plate (8) is fixed onto the tank wall (1) segment by segment by means of silo bolts (9) that fit into the holes (5a, 5b), hereby forming an uninterrupted peripheral clamping band (8).
The upper and lower side of the clamping plate (8) is provided with an uninterrupted row of mastic (10), so as to firmly seal the clamping plate preventing any leakage of water from the tank.
In this embodiment, the clamping plate (8) has an upper edge (11) that is slightly folded open towards the center of the tank. A feature like this, extending out of the plane of the plate, prevents the plate from curving when the bolts are tightened by enhancing the firmness of the plate. Other embodiments of such a feature are possible. This embodiment here also eases the application of the mastic (10) into the space of the folded upper edge (11).
Around the outside of the tank, at the level of the concrete floor bottom, an upstanding casing (12) is applied holding gravel (13) between the casing and the tank. An L-profile (14) is applied on to the tank wall and leveled with shims (15) and fixed by means of silo bolts (16) to tank wall (1) and with anchor bolts (16) to the concrete floor (2) to prevent gravel (13) from piercing through the bottom of the protective liner (3) and the membrane (4). The upstanding casing (12) is preferably about 15 cm high. The filled casing provides an esthetical look of the tank and protects any dirt or other material from entering under the side of the tank.
The mastic (6, 7, 10) used for sealing is specially made for good adherence to both the galvanized steel tank and the (EPDM) membrane. Examples of mastics suitable for this purpose are AvascoFlex and AvascoRub or equivalents.
The inside of the tank (1) may be protected against corrosion and fouling. The water inside the tank may also be treated against fouling. The tank is preferably grounded.
Figure 2 shows a detailed view of the tank bottom, showing the sidewalls (1) and the membrane (4) on the bottom. The clamping plate (8) is mounted close to the bottom of the tank, but could also be mounted at any higher level. Figure 2 shows the empty watertight water tank which is ready for receiving water. As can be seen, the clamping plate is mounted at the lower bottom of the tank.

Claims

A water tank for water storage, comprising sidewalls (1) mounted on a foundation (2) and a membrane (4) covering the foundation and extending upwards onto the inner sidewalls (1), wherein the membrane (4) only extends up to a lower part of the sidewalls (1), such that when the water tank is filled with water, the membrane (4) edge ends under the water level and wherein the membrane (4) is applied to the sidewalls (1) by means of a peripheral band (8) of clamping plate, sealing bands (6) being provided between the membrane (4) and the sidewalls (1) and between the membrane (4) and the clamping plate (8) characterized in that the clamping plate (8) comprises at least two rows (I, II) of prepunched holes (5b), extending parallel to the surface of the foundation (2), that the sidewalls (1) comprise corresponding prepunched holes (5a), that the sealing bands (6) are made of mastic (6) and are applied at the level of the rows (I, II) of holes (5b) and that the membrane (4) is watertightly applied between said inner sidewalls (1) and the clamping plate (8) by means of bolts (9) through the holes (5a, 5b) and the mastic (6, 7).
Water tank according to claim 1, characterized in that said membrane (4) extends 10 to 50 cm up onto the sidewalls (1), preferably 10 to 30 cm.
Water tank according to any of the preceding claims, characterized in that at least one row of swell seal mastic (7) is provided in an uninterrupted watertight manner between the sidewalls (1) and the membrane (4).
Water tank according to any of the preceding claims, characterized in that a mastic (6) is provided in each hole (5a, 5b) in an uninterrupted watertight manner.
Water tank according to any of the preceding claims, characterized in that a mastic (10) is provided in an uninterrupted watertight manner, between the lower end of the clamping plate (8) and the membrane (4), between the upper edge of the clamping plate (8) and the membrane (4), and between the membrane upper edge and the sidewalls.
Water tank according to any of the preceding claims, characterized in that said clamping plate (8) comprises one or more reinforcing ribs (11) extending out of its surface.
Water tank according to claim 6, characterized in that said reinforcing rib (11) is a bent edge or a seal edge.
Water tank according to any of the preceding claims, characterized in that it comprises one or more additional peripheral bands (8) of clamping plates each band comprising two or more horizontal rows (I, II) of prepunched holes (5b) corresponding to prepunched holes (5a) in the sidewalls.
Water tank according to any of the preceding claims, characterized in that the membrane (4) is made of EPDM.
Water tank according to any of the preceding claims, characterized in that a protective layer (3) is applied on the bottom between the foundation (2) and the membrane (4).
Water tank according to claim 10, characterized in that the protective layer (3) partly extends up onto the sidewalls (1) of the tank.
A method for constructing a water tank of claims 1 to 11, said method comprising the steps of:
a. Mounting the sidewalls (1) of a water tank onto a foundation (2);

b. Spreading a membrane (4) onto the foundation (2) and extending said membrane onto the inner sidewalls (1) up to a lower part of the sidewalls (1) such that when the water tank is filled with water, the membrane extends to a level under the water level;

c. Applying an uninterrupted swell seal mastic (7) between the membrane (4) and the sidewalls (1);

d. Applying an uninterrupted mastic (6) between the membrane (4) and the sidewall (1) at the level of the rows (I, II) of holes (5a);

e. Applying an uninterrupted mastic (6) between the membrane (4) and a clamping plate (8) at the level of the rows (I, II) of holes (5b);

f. Fixing the clamping plate (8) to the sidewalls (1) by means of bolts (9) through the holes (5a, 5b) and the mastic (6);

g. Applying mastic (10) to the edges of the clamping plate (8) and the membrane (4), sealing off any space between the edge of the membrane (4) and the sidewalls (1) and any space between the clamping plate (8) and the membrane (4);
Method according to claim 12, characterized in that it comprises the additional step of providing an outer casing around the bottom of the watertank.
Use of a water tank according to any of claims 1 to 11 for watertight storage.