Tank For Fuel Oil Or Other Liquids

Abstract

A double-walled tank is provided for the storage of fuel oil and other liquids and comprises a spaced inner and outer tank in accordance with known concepts. In the present disclosure the outer tank is made of asbestos-cement, preferably with continuously wound asbestos fibers.

Description

It is known to construct tanks for fuel storage and the like which are to be buried in the ground of doublewalled construction, or stated otherwise, of spaced inner and outer tanks. Sensing means is provided between the tanks operable, for example, according to pressure changes between the tanks to detect leakage of liquid into this space.

Liquid may leak from the internal tank due to the corrosion or other reasons, while ground water or other liquids in the ground may seep through the outer tank in the event of any corrosion or damage thereto. In accordance with some prior art uses both the inner and the outer tank are made of steel, and the susceptibility to corrosion is obvious. Other constructions are known in which the outer tank is made of steel for physical strength and protection, while the inner tank is made from plastic materials reinforced with glass fibers. It is also known to substitute an outer concrete tank for the steel tank mentioned above. It is common practice to provide a negative pressure between the two tanks which is measured continuously by a suitable sensing device. Any increase in pressure in the space between the two tanks will cause the sensing device to actuate a warning signal. Alternatively, sensing devices may be placed between the tanks at the bottom thereof to react to the presence of moisture at this location.

Double-walled tanks by their very nature are more expensive than simple, single-walled tanks. Not only are subterranean tanks subject to corrosion, but they are also subject to physical damage during transportation from the factory to the construction site. Furthermore, they often must withstand a substantial external pressure when buried in the ground, and under some circumstances the water table in the ground may cause the tanks to float if they are only partially filled.

When a plastic material is used as the construction material for the inner tank, and if correctly selected and used, internal corrosion is no longer a great problem. However, problems arising in connection with the outer tank have heretofore not been solved.

Steel is often used for the outer tank as it is easy to fabricate and is low in price. However, corrosion problems are substantially insurmountable. The application of protected coats of paint, asphaltic materials, etc. do not entirely solve the problem since such coats are easily damaged. The use of plastics for the outer tank has not heretofore proved fully satisfactory. Unless glass fiber reinforcement is used throughout, the plastic material is not strong enough, and the use of glass fiber raises the manufacturing cost, often to a prohibitive level. In any event, the use of plastic for the outer tank results in a sufficiently light weight tank that special anchors must be used to preclude the tank from heaving or floating on the ground water. Rendering the anchorings resistant against corrosion also significantly raises costs.

The use of concrete for construction of the outer tank overcomes the problem of corrosion, and also overcomes the problem of floating on ground water. On the other hand, concrete tanks are easily damaged by physical shock, and are so heavy as to increase installation costs to a great degree. Due to the risk of physical damage, concrete tanks must be installed slowly and with a great deal of labor, thus raising the cost of installation significantly. Concrete tanks are so heavy that they can be installed only with the use of special cranes which are costly and which are available only in certain cities. The use of such cranes elsewhere requires expensive transportation to a job site. Furthermore, the great weight of concrete tanks renders shipping thereof from the factory to the job site expensive.

In accordance with the present invention, the problem of constructing a tank for underground storage of fuel oil and the like which is resistant to corrosion and which is reasonably inexpensive to fabricate and install has been solved.

In accordance with the present invention, the outer tank is made of asbestos-cement, preferably with the asbestos fibers continuously wound. The outer tank is formed as a more or less cylindrical tube having end covers joined thereto in physically strong and leak-proof manner. The inner tank may be of any known construction, preferably of plastic material, while a warning device is provided between the tanks to actuate an alarm when any liquid enters the space between the tanks.

An outer tank of asbestos-cement can be placed directly in the ground without danger of corrosion. Due to the strength of the outer tank it weighs much less than a concrete tank, most particularly because the thickness need not be nearly so great. Nevertheless, the tank is sufficiently heavy that it will not float in the subterranean ground water, even when the tank is empty. Hence, no additional anchoring is required. The weight strikes on an ideal compromise between the too lightweight of plastic tanks and the too heavyweight of conventional concrete tanks, whereby transportation and installation difficulties do not arise, nor do problems of floating of the installed tanks.

In the preferred embodiment of the invention the tank end pieces or lids are formed of at least two asbestos-cement plates each, joined at their confronting faces, preferably by a suitable adhesive. The resulting structure is an asbestos-cement plate having portions of respectively larger and smaller diameter with the smaller diameter portion fitting within the wall of the outer tank, and the portion of the larger diameter butting against the end of the outer tank wall. Preferably the asbestos fibers of the two plates forming a lid are radially arranged with the fibers of the adhesively joined plates being offset from one another arcuately by about ninety degrees. The lids are secured to the end of the outer tank by means of screws extending axially through the lids and into dowels or other screw receiving means installed in the outer tank wall. In addition, there are preferably radially directed screws passing through the outer tank wall and threaded into dowels or the like in the lids.

In addition, a sealing material is used between the lids and the outer tank walls, and this preferably is an adhesive material coating all of the contacting surfaces between each lid and the respective outer tank wall. In addition, a sealing tape preferably is disposed over the slit between the lid and the outer tank wall on the outside thereof. Such tape preferably is made of a corrosion resistant material and is provided with an adhesive, such as of the pressure sensitive type.

Further advantages and structural details of the present invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a longitudinal sectional view through a double-walled tank constructed in accordance with the principles of the present invention;

FIG. 2 is a partial cross section through the tank as taken substantially along the line II--II in FIG. 1;

FIG. 3 is a view on a greatly enlarged section showing a preferred embodiment of the connection between a lid and the outer tank;

FIG. 4 is a view similar to FIG. 3 showing another embodiment of the connection between the lid and outer tank;

FIG. 5 is an enlarged longitudinal sectional view of a modification of the invention wherein the inner tank comprises a plastic film, the view being taken in the vicinity of the tank inlet and;

FIG. 6 is a modified form of this invention showing the tank with one end wall thereof formed as an integral part.

A double-walled tank or container 1 comprises an outer tank 2 and an inner tank 3. The inner tank 3 preferably consists of a synthetic plastic which is reinforced with glass fibers. The inner tank is provided with feet 4 or other spacers for maintaining a suitable space between the outer surface of the inner tank 3 and the inner surface of the outer tank 2. The inner tank 3 is provided at the top thereof, and conveniently adjacent the center a protuberance through which a filling tube 6 and a control tube 7 lead to the inside of the inner tank 3. The maximum diameter of the inner tank 3 measured across the feet 4 and the protrusion 5 is somewhat smaller than the inside diameter of the outer tank 2.

The outer tank 2, in accordance with the present invention, is formed essentially as a cylindrical tube comprising asbestos-cement. It has a length which is equal to or somewhat greater than the maximum length of the inner tank 3. At either end the outer tank 2 is closed by lids 8, 8', likewise made of asbestos-cement. The lids may be constructed as flat plates (viz, lid 8) or, in a preferred form, as shell-like or concave-convex sections (viz, lid 8'). The lids are secured to the tube or sidewall of the outer tank 2 in a leak proof manner, preferably by the use of an adhesive. As an alternative, one of the lids 8,8' may be manufactured integral with the tube or sidewalls of the outer tank so that it is thereafter necessary to install only one lid following installation of the inner tank 3.

The outer tank is provided with a protuberance 9 substantially co-axial with the protuberance 5 of the inner tank. The protuberance 9 preferably consists of a tube and is provided at its outer or free end with a flange which forms a sealing and attachment face for a cover plate 10 which, upon removal, provides access to the interior of the outer tank 2, and vents to the inner tank 3. The tube forming the protuberance 9 preferably is adhesively secured to the sidewall of the outer tank 2.

Means is provided for ascertaining when any liquid enters the space between the inner and outer tanks. In the present disclosure a pump 11 is connected through a conduit 12 with the inner space between the two tanks. The pump removes a certain amount of air from this space, thereby maintaining it under negative pressure. Another tube or conduit 13 passes through the plate 10 (as do the tubes or pipes 6,7, and 12) and has connected a gauge or indicator 14 which indicates the pressure existing in the space between the two tanks. In addition, or alternatively, the tube 13 may be connected to an alarm actuator for operating a visual or audible alarm in the event that pressure rises within the space between the tanks. As will be understood, the tubes 6,7, 12 and 13 pass tightly through openings in the cover plate 10 so as to preclude leakage of air through the cover plate. In the event of any failure in the cover plate 10 or of failure to seal with the tubes passing therethrough, then there will be an indication of rising pressure in the space between the two tanks, and inspection will reveal the flaw where upon the plate can easily be replaced without any significant expense.

With tanks having a capacity between roughly 500 and 2,000 gallons, it has been found advantageous if the wall thickness of the outer tank 2 is about an inch and a half, the wall thickness of the inner tank 3 is slightly less than 1/10 inch, and the spacing between the tank walls is about 1/8 inch.

It is particularly advantageous if the flat lids 8 of the outer tank are composed of several flat plates secured together by a suitable adhesive. Once such embodiment of a lid 8 is shown in FIG. 3, the lid comprising two plates 20 and 21. The innermost plate 20 in this embodiment has an outer diameter just slightly smaller than the inner diameter of the outer tank 2, while the outer plate 21 has an external diameter which is substantially the same as the external diameter of the outer tank 2. Accordingly, a rather large sealing face is created between the asbestos-cement tube and the asbestos-cement lids.

The two plates 20 and 21 have their asbestos fibers oriented in one direction for each plate, and the plates are oriented relative to each other so that the fibers in one plate are substantially perpendicular to the fibers in the other plate. The plates are cemented or adhesively secured to one another in such relative position whereby the space 30 between them is filled with the adhesive. In order to connect the asbestos-cement tube comprising the sidewall of the tank 2 to the lid, a sealing mass is provided therebetween, and such sealing mass preferably comprises an adhesive. In addition to this, the parts are secured together by screws including axially directed screws 25 passing through the outer plate 21 into the sidewall of the tank 2. There are also radially oriented screws 26 passing through the sidewall of the tank 2 and into the inner plate 20.

Each of the screws 25 and 26 preferably engages in a dowel received in the corresponding sidewall or plate. Finally, a leak proof joint is further insured by the provision of sealing tape 31 which is passed around the slit between the tube and the plate 21. This sealing tape 31 resists corrosion and preferably is self adhering. It must also resist being desolved by or otherwise attacked by the liquid stored in the tank.

In a further embodiment of the invention as shown in FIG. 4, there are three asbestos-cement plates 20, 21, and 22 of common outside diameter joined to one another as by a suitable adhesive. All of the plates 20, 21, and 22 are of a common outside diameter, and are secured to the sidewalls of the outer tank 2 by means such as screws 3, and preferably also sealing tape 31 wrapped around the outside of the slit between the sidewall and the inner plate 20.

In accordance with a further embodiment of the invention, the inner tank 3 is formed as a plastic film which is connected to the outer tank 2 in the manner shown in FIG. 5. The inner tank 3 has a lateral extension or protrusion 35 corresponding to the protrusion 9 of the outer tank and goes upwardly, extending first in a radial direction, and then around the rounded upper end of the protrusion 9, and finally in an axial direction. At the upper limit of the protrusion 9 there is attached a rim 36 which in cross section is L-shaped secured by means such as screws 37 to the vertical protuberance. The film of the protrusion 35 is introduced into the slit between the rim 36 and the plate 10. Two annular gaskets or washer like seals 40 and 41 grip the protuberance against the upper flange of the rim 36.

A clamping ring 32 is provided to retain the film extrusion or protuberance 35 against the protuberance 9 and comprises a clamping ring 32 made either of synthetic material or a metal which is coated with a synthetic, and which presses the protuberance 35 resiliently against the protuberance 9 of the outer tank 2.

As an alternative, it is possible that the leakage warning device may consist of metal anodes or similar parts arranged in the intermediate space between the outer and the inner tank at the bottom thereof to indicate moisture arriving at that location. In order to insure that any such liquid will arrive in the region of such metal anodes, and also so as to facilitate cleaning of the inner tank, the inner tank and outer tank are both inclined at a small angle from the horizontal. In the space between the tanks at the bottom thereof there preferably is provided a plastic grating (not shown) which allows a free flowing of any liquid in the space until it reaches the deepest region of the tank.

In order to facilitate transportation of the tank and installation thereof, transportation belts (not shown) may be provided having eyelets therein for receipt of hooks and the like for lifting of the tank. Such transportation belts and eyes need not be removed, but may be left attached to the tank after its installation. FIG. 6 shows a modified form of this invention wherein the end wall 8" is formed as an integral unit of the outer shell 2.

The specific examples of the invention herein shown and described are for illustrative purposes only. Various changes in structure will no doubt occur to those skilled in the art, and will be understood as forming a part of the present invention insofar as they fall within the spirit and scope of the appended claims.

Claims

The invention is claimed as follows:

1. A container assembly comprising an inner and an outer tank adapted for under ground large capacity storage of fuel oil and other liquids, said outer tank being formed as a cylindrical tube made substantially entirely of asbestos-cement of a thickness to be self supporting of its own weight and the weight of the inner tank, said tube including ends, at least one end being closed and sealed by a lid, said lid including two plates of asbestos-cement secured together in face to face relation and having asbestos fibers in each plate oriented at substantially ninety degrees relative to the fibers of the other plate.

2. A container as set forth in claim 1 wherein the asbestos-cement of said tube comprises continuously wound asbestos fibers.

3. A container as set forth in claim 1 wherein one of the lids is integral with said tube.

4. A container as set forth in claim 1 wherein at least one of the lids is adhesively secured to the cylindrical tube.

5. A container as set forth in claim 1 wherein said lids form vertical end walls for said outer tank and at least one of said vertical end walls is substantially flat.

6. A container as set forth in claim 1 wherein said lids form vertical end walls for said outer tank and at least one of said vertical end walls is concave-convex configuration.

7. A container as set forth in claim 1 wherein the inner tank comprises a plastic film.

8. A container as set forth in claim 1 and further including sensing means disposed between said tanks to sense the entry of liquid into the space between said two tanks.