Replaceable Tank Lining

Abstract

Replaceable tank (RT) for installing in metallic storage tanks for fluids consists of a tank body and one or more orificial members. The RT conforms with inner walls of the storage tank and is made of flexible materials, such as rubber or PVC that are impermeable to the fluids stored. Orificial members having a tubular neck and conforming with the lumen of the orifices of the storage tank are typically made of the same material as the RT. Magnets, attached to, or embedded in, the walls of the RT are attracted to the walls of the metallic storage tank. A method for manufacturing, packaging and for in situ installing an RT is provided.

Description

FIELD OF THE INVENTION

The present invention relates to storage tanks, and more particularly to a method for prolonging the durability of such tanks.

BACKGROUND OF THE INVENTION

Tanks used for storing petroleum and petrochemicals are normally designed to be leak resistant in order to minimize loss of their contents in or onto the ground, which in excess amounts might contaminate the soil and pollute the surroundings. Many states have enacted laws or regulations to protect the environment by enforcing restrictions on the use of such tanks. Accordingly, operators or owners of tanks storing petroleum, chemicals, or hazardous material, are to provide secondary containment vessels. Secondary vessels such as an exterior shell or leak-proof housing are intended to surround the storage tank and serve as a backup safety vessel to contain any materials which may leak out of the primary tank. In an effort to comply with these secondary containment laws and regulations, operative tanks are typically replaced by double walled tanks. A typical solution often applied with regard to underground storage tanks includes encasing the existing storage tanks (usually steel tanks) in concrete. Another common solution consists of placing an exterior liner or flexible bag around an existing storage tank. Such techniques require excavation of the tank sites, or replacement, or reinstallation of the tanks, along with additional construction.

U.S. Pat. No. 4,763,805 discloses a system which is suitable for installation especially in underground storage tanks. The system has an expandable compartment such as a bladder which is made of a flexible material like rubber that is impermeable to the stored fluids. The expandable compartment serves as a primary container, whereas the operative tank encasing it serves as a secondary tank. However, the walls of the expandable tank are prone to damage due to the dynamically changing volume of the space between the inner tank and the storage tank. Furthermore, installing such a tank is somewhat complex and may require a presence of a worker inside the storage tank.

The present invention facilitates protection of the environment from faulty tanks, and is applicable especially to tanks attractive to magnets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a longitudinal sectional view of a replaceable tank according to the invention;

FIG. 1B is a side view of the replaceable tank of FIG. 1A;

FIG. 1C is an isometric view of an orificial member of a replaceable tank according to a preferred embodiment of the present invention;

FIG. 2A is a frontal view of the replaceable tank of FIG. 1A after a step of flattening;

FIG. 2B is a frontal view of a section of a replaceable tank which is partially folded;

FIG. 2C is a schematic presentation of a replaceable tank after a step of folding;

FIG. 2D is a schematic presentation of a step of packaging a replaceable tank in a hollow cylinder according to a preferred embodiment of the present invention;

FIG. 3 is a schematic presentation of an insertion of a replaceable tank into an operative tank according to a preferred embodiment of the present invention;

FIG. 4 is an isometric view of a jig for drilling an aperture in a replaceable tank of the invention;

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Containers or tanks made of a magnetic metal such as steel are often used for storing fluids considered contaminating and/or hazardous such as fuel, oil, chemicals, pressurized propane or natural gas. These containers must not undergo deterioration that would promote leakage of the contents into the environment. The present invention provides a method and system for applying an internal lining to such containers, with the intention of preventing leakage from the tank. Accordingly, replaceable tanks (RT) conforming to the internal contours of the metal tank of the art are provided. The RTs of the invention in effect provide an internal, replaceable coating to the metal tank. An aged RT is replaceable by a new one so that the external, metal tank is may corrode or undergo other structural deterioration without the risk of environmental damage by spillage of the contents. The RT of the invention is made of flexible materials such as rubber or PVC, impermeable to the relevant fluids.

General Structure of the Replaceable Tank

Reference is first made to FIGS. 1A and 1B in which a longitudinal sectional view and a side view of a RT of the invention are shown respectively. RT 10 has orifices 12 and 13 located at its top side. Magnets 14 are attached to the inner surface of the RT walls. The distances between magnets 14 are determined in respect of the weight of the empty RT and the intensity of the magnetic field which they induce. Side wall 16 is planar or dome shaped conforming to the internal shape of the metal tank. Circumferential flange 17 provides for attaching tubular neck 18 to the rim of the corresponding orifices of the metal tank.

Typically a metal storage tank such as a fuel tank in a refueling service station has at least four orifices for performing the following functions respectively: (i) filling the tank with fuel; (ii) dispensing fuel; (iii) measuring the level of the fuel; and (iv) a vent. The vent is the most narrow orifice of the lot, typically measuring a circumference of 1 inch. The widest orifice of the storage tank is typically used for the insertion of the RT into the tank for providing internal lining.

Construction and Fitting of the RT

The construction of a RT is carried out in two main stages. At stage 1, the tank body and appendages are assembled, and at stage 2 the RT is fitted into the operative tank, typically in situ, and completed. A RT is produced from sheets of impermeable matter, for example rubber or PVC usually approximately 2 mm thick. The sheets are cut into smaller sheets or pieces having a particular shape as required to assemble the RT. Then, the sheets and pieces of building material are joined by soldering or gluing such that the RT formed may fit in with the internal contours of the metal tank. Magnets are attached or embedded in the inner surface of the RT typically prior to its assembly.

Typically a RT is assembled having at least one wide aperture located in correspondence with the exact location of the orifice in the metal tank. A prior knowledge of the exact locations of the other apertures of the metal tank is not necessary for the assembling of a corresponding RT. Such additional apertures are made at the site of application. An orificial member having a neck is inserted in conformity with an aperture, the procedure described with reference to FIG. 1C. Orificial member 20 has a circumferential flange 22 located at one end of hollow tubular neck 24 and an external circumferential ridge 26 located at a second end of the neck. Whether attached to the RT or not, the role of the ring is to prevent falling off or pulling away of the orificial member. The external diameter and the length of the tubular neck fit in the corresponding dimensions of an orifice of the metal tank. Holes 28 provide for securing flange 22 to a rim of the corresponding orificial of the metal tank by means of bolts. A circular aperture matching the external diameter of the tubular neck is provided by punching, drilling, or cutting the corresponding piece of building materials used in the assembly of the RT prior to its assembly. After the assembly is completed the orificial member is inserted into this aperture such that its circumferential ridge is pushed over to the other side of the rim of the aperture. The cylindrical neck is optionally further glued and or soldered to the body of the RT. Other orificial members are produced in advance, corresponding to the additional orifices of the metal tank. Orifices of the storage tank may vary in shapes, and therefore may differ from the cylindrical shape as described hereinabove. The shapes of the orificial members conform to the internal contours of the corresponding orifices of the metal tank according to the present invention. The external ridge can also be segmented and the number of segments and/or the dimensions may vary. Rigid orificial members are partially or completely made of rigid materials such as metals. In general, an orificial member for an orifice of a metal tank has a circumferential flange at one end and an external ridge at its other end of the tubular neck. The hollow tubular neck conforms to the inner dimensions of the metal orifice. For the sake of simplicity, the following description of the invention refers to cases of cylindrical symmetry wherein any one who is knowledgeable with the art is able to adopt the description to other geometrical shapes of orifices of such storage tanks.

Folding Up and Packaging a RT

RTs are packaged according to the invention for shipping to the site of installation. Such packaging provides the background for a convenient installation process and is also convenient with regards to shipping. A process of packaging consists of several steps: Firstly, the RT is flattened forming a planar geometrical body. Then the flattened RT is folded and ropes are tied to its folded orificial members. Then, the folded RT is twisted and packaged for shipping. Reference is now made to FIGS. 2A-2D in which several views of the RT at different stages of a packaging process according to a preferred embodiment of the present invention are correspondingly shown. In FIG. 2A a frontal view of a flattened, pre-folded RT of FIG. 1A is shown. In FIG. 2B a frontal view of a section of the same RT, partially folded, is shown. In FIG. 2C a schematic presentation of same RT, completely folded, is shown. Fully folded RT 36 has orificial members 38 located at its topside folded as well. At this stage a rope, not shown, is tied to each folded orificial member to enable subsequent pulling out of the corresponding orifice of the metal tank as is described infra. Twisting of the folded RT is carried out by rotating the upper and lower ends of RT 36 in opposing directions around axis 42 as is indicated by arrows 42A and 42B correspondingly. In FIG. 2D a packaged, folded and twisted RT is schematically shown. RT 46 is inserted into hollow cylinder 48 such that folded orificial members 50 and ropes 52 tied to them are the last to be inserted. The length of each of ropes 52 is not smaller than the height of hollow cylinder 48. The free ends of these ropes are further secured to the inner wall of the hollow cylinder near its upper end. Lids, not shown, optionally cover the two orifices of hollow cylinder 48 after the folded and twisted RT, folded orificial members 50 and ropes 52 are completely inserted into cylinder 48. The external radius of cylinder 48 is smaller than the inner radius of the corresponding main orifice of the metal tank. The width of the wall of cylinder 48 which is made of standard packaging material such as cardboard or plastic sustains the stresses applied by the twisted RT and protects the RT from being damaged during shipment and/or storage. Optionally the inner surface of hollow cylinder 48 is coated with a lubricant such as a talcum powder which does not harm the RT. Orificial members, intended for other orifices of the metal tank and are made of flexible materials, are similarly packaged in corresponding cylinders.

The shape of the package need not be cylindrical. Any shape that fits in with the shape of the corresponding orifice of the metal tank, such that the packaged RT, or the orificial members, can be inserted into the corresponding orifices, is acceptable. Nevertheless the packaging is constructed such that it is removable from the RT, or the orificial members, after the package is inserted into the interior of the metal tank.

Installing the RT

First the metal tank is emptied, any existing sediments are removed and the inner surface of the tank is rinsed and cleaned. A thorough cleaning such as by chemical solvents, detergents and/or steam, is particularly required in a periphery of any edges or sharp bulges that may damage the RT. Such surfaces optionally require further smoothing. Such smoothing can be carried out by inner surface coating of the metal tank with plaster or sprayed with a foamy plastic resin. The RT can then be inserted into the metal tank through its main orifice.

Reference is now made to FIG. 3 in which a schematic presentation of a RT being inserted into a storage tank is shown. Storage tank 70 has a main orifice 72 through which the packaged RT is inserted. Hollow cylinder 74 in which the RT is packaged is pulled upwards from main orifice 72 while RT 76 is forced downwards. The ropes, not shown, which are tied to the orificial members of the RT are released at this stage from the upper end of the cylinder and are manually held while cylinder 74 is completely removed from the RT. Twisted RT 76 is released and is partially unfolded by the elastic forces applied by its deformed walls and by gravity. The releasing and unfolding are manually assisted by shaking and rotating the ropes.

The process of fitting the orifices of the RT to the corresponding orifices of the metal tank is described in the following. If the RT has more than one orifice, the rope tied to each orificial member other than the orificial member corresponding to the main orifice of the metal tank, is pulled out of its corresponding orifice of the metal tank. Pulling the ropes tied to such different orificial members is effected by means of a catching device. Such a catching device is inserted into the metal tank through the corresponding orifice. Each of the orificial members is untied and unfolded and further pulled upwards through the corresponding orifice of the metal tank. The circumferential flange of an orificial member is rotated around its axis so that the topside wall of the RT is straitened. By means of such rotations the topside of the RT and all its assembled orificial members fit in the corresponding portion of the lumen of the metal tank. The flanges of all orificial members are secured to the rim of their corresponding orifices of the metal tank by bolts. Then, all other orificial members other than the one corresponding to the main orifice are sealed off. The RT is inflated by pressurizing gas such as air through the main orifice. Keeping the RT pressurized for a predetermined time at a predetermined pressure completely untwines and unfolds the RT and further attaches it to the inner walls of the metal tank by means of the magnetic pieces. The RT remains attached to the inner walls of the metal tank conforming to its lumen even after being depressurized.

At this stage, installation of all the orificial members not yet installed is completed. Orifice 84 is an exemplary orifice that corresponds to either a wide orifice in which a corresponding orificial member has not been installed during the stage of assembling a RT, or another orifice such as an orifice for measuring the level of the fluid which is different from a vent. Venting orifices such as orifice 85 typically have pipe 86 extending upwards of which one of its ends is connected to the topside of the metal tank and other end 88 is curved downwards.

An installation process of orificial members is carried out preferably as herein described. First an aperture is made by drilling or punching or cutting the top side wall of the RT which is attached to the inner walls of the metal tank. The cover of the metal orifice is removed prior to that. In a case in which the metal orifice is a vent, a section of the pipe having its curved end is removed prior to cutting. Cutting such as by drilling is effected through the corresponding orifice of the metal tank by employing a corresponding jig. The packaged orificial member is inserted into the aperture drilled in the topside of the RT. Insertion of an orificial member is similarly carried out as the insertion of the RT as described herein above. The cylinder in which the corresponding orificial member is packaged is inserted into the metal orifice so that its open bottom end protrudes into the lumen of the RT. The packaged orificial member is pushed down, and concomitantly the cylinder is pulled up to completely remove it from the corresponding orifice of the metal tank. Then the twist of the orificial member is released further unfolding by elastic forces applied by its deformed walls. In the case of a rigid orificial member, the lower end to be inserted in the metal tank is squeezed, before forcing into the orifice of the metal tank. A slight upward pulling attaches the circumferential ridge of both types of orificial members to the rim of the aperture cut in the topside wall of the RT. Then fitting the orificial member to the metal orifice of the tank is similarly carried out as described hereinabove. After bolting the circumferential flanges of the orificial members to the rim of the metal orifices the covers of corresponding orifices are replaced and or the sections of a pipe having a curved end of a vent are reattached to the rim of the pipes fitted with the corresponding orificial members.

Reference is now made to FIG. 4 in which an isometric view of an exemplary jig according to the invention is shown. Jig 100 has tubular guide 102 having cylindrical lumen and circular aperture 103. The inner diameter of tubular guide 102 is slightly larger than the diameter of the drill to be employed. The diameter of circular flange 104 at the top of tubular guide 102 exceeds the diameter of the metal orifice to which it is to be attached. Neck 106 has a diameter that closely reaches the inner diameter of the metal orifice. The bottom of the wall of tubular guide 108 is beveled so that its external lower diameter slightly exceeds the inner diameter of its lumen. Such a jig is inserted into a metal orifice so that its tipped end is placed on top of the surface of the RT and its neck 106 fits in the rim of the metal orifice of the metal tank. By means of such a jig the aperture formed in the RT by drilling through the jig is aligned with the orifice of the metal tank. Optionally after drilling a first hole in the upper wall of the RT through the lumen of such a jig, the hole is widened by means of additional drilling through this hole employing a drill whose diameter is slightly smaller than the diameter of the metal orifice and is larger than the diameter of the first drill.

An aged RT need not be removed from an operative metal tank prior to replacing. A new RT may be installed in a tank supplemented with a RT of the invention, much in the same way as described above. The metal tank furnished with the additional new RT would thereby be converted to a multi-walled tank by such internal lining with the new RT. Obviously the new RT slightly differs from the old one previously installed.

Claims

1. A replaceable tank (RT) for installing in a metallic storage tank for fluids, comprising:

a tank body made of a flexible material impermeable to said fluids;

at least one orificial member attachable to a hole in said tank body, and

at least one magnet attached to said tank body for attracting to said metallic storage tank.

2. A RT for installing in a storage tank for fluids as in claims 1, wherein one end of a tubular neck of said at least one orificial member has an external ridge.

3. A RT for installing in a metallic storage tank for fluids as in claim 1, wherein said at least one orificial member is attached to said tank body.

4. A RT for installing in a metallic storage tank for fluids as in claim 1, wherein one end of a tubular neck of said at least one orificial member has a flange.

5. A RT for installing in a metallic storage tank for fluids as in claim 1, wherein said at least one orificial member is rigid.

6. A method for preventing leakage from metal storage tanks comprising providing an internal lining to said storage tank by magnetically attaching a replaceable tank (RT) conforming to the internal contours of the metal tank.

7. A method for preventing leakage from metal storage tanks as in claim 6, wherein at least one orificial member is further attached to said RT.

8. A method for preventing leakage from metal storage tanks as in claim 6, further comprising

folding said RT prior to shipping to the place of installation, and

packaging said folded RT in a package insertable into said storage tank through an orifice of said storage tank.

9. A method for preventing leakage from metal storage tanks as in claim 6, wherein gas pressurizing is used for providing said lining,