Cover for storage tanks

Abstract

A system for providing a flexible cover in a storage tank is provided that reduces the amount of vapors released from a hydrocarbon liquid and other liquids and reduces the amount of product (liquid) lost to the atmosphere. The flexible cover is, in some embodiments, comprised of one or more membranes joined together along their respect perimeter edges. The membranes are made from a material or materials that allow the cover to roll up, or otherwise reduce the cross sectional diameter or area of the cover, to allow the membrane to pass through a port in a storage tank. Once inside the storage tank, the cover may return to its normal and/or predetermined dimensions to cover the upper surface of the hydrocarbon or other liquid, which reduces the release of vapors from the hydrocarbon liquid and other liquids.

Claims

1. A system for covering a liquid in a storage tank and depositing said liquid in said storage tank, comprising: said storage tank having a bottom, an outer wall, and a roof that form an enclosed volume, said storage tank having an access port with a cross sectional area; said liquid at least partially filling said enclosed volume of said storage tank, said liquid having an upper surface; a flexible cover having at least one membrane, said flexible cover having an uncompressed cross sectional area larger than said cross sectional area of said access port and a compressed cross sectional area smaller than said cross sectional area of said access port to allow said flexible cover to pass through said access port; an inset of said flexible cover that defines a space between said flexible cover and said storage tank; and a conduit having an open upper end and an open lower end, wherein said conduit extends through said storage tank and said space defined by said inset of said flexible cover such that said lower end of said conduit is positioned below said upper surface of said liquid, wherein said lower end of said conduit is offset from said bottom of said storage tank by a predetermined distance, wherein said conduit is configured to deposit liquid from outside said storage tank to below said upper surface of said liquid.

2. The system of claim 1, further comprising a tether extending from said flexible cover to an inner surface of said storage tank to maintain a relative orientation between said flexible cover and said storage tank, and a weight interconnected to an end of said tether to keep said tether taut between said flexible cover and said inner surface of said storage tank.

3. The system of claim 1, wherein said flexible cover comprises a first membrane having a valve, said first membrane interconnected to a second membrane to define a cavity between said membranes, wherein said valve is configured to allow the introduction of a gas or liquid into said cavity to inflate said flexible cover.

4. The system of claim 1, further comprising: an inflatable tube positioned on said at least one membrane of said flexible cover, wherein said at least one membrane is a single membrane, and wherein a valve is operatively interconnected to said inflatable tube such that said valve allows the introduction of a gas or liquid into said inflatable tube to reduce the bulk density of the flexible cover.

5. The system of claim 1, wherein said flexible cover comprises a single membrane having a bulk density that is less than a bulk density of said liquid.

6. The system of claim 5, wherein said single membrane comprises a plurality of air pockets.

7. The system of claim 5, wherein said single membrane comprises at least one of Nitrile, Nylon, Polypropylene, Ryton (polyphenylene sulfide), PVC, Viton (synthetic rubber and fluoropolymer elastomer), Tygon (flexible polymer), Nitrile Butadiene, Nitrile Butadiene with a copolymer of acrylonitrile, and any other material that is chemically inert with respect to said liquid.

8. The system of claim 1, wherein the at least one membrane is a continuous first membrane and a continuous second membrane joined to each other about a perimeter edge to define a cavity.

9. The system of claim 8, wherein said cavity is inflatable from a first volume to a larger second volume.

10. The system of claim 1, wherein said access port is a thief hatch.

11. A method of placing and orienting a flexible cover over a hydrocarbon or other liquid in a storage tank, comprising: providing said storage tank having a bottom wall, an outer wall, and a roof that form an enclosed volume, said storage tank having an access port with a cross sectional area, said storage tank having said hydrocarbon or other liquid at least partially filling said enclosed volume, said hydrocarbon or other liquid having an upper surface; providing the flexible cover having at least one membrane, said flexible cover having an uncompressed cross sectional area larger than said cross sectional area of said access port and a compressed cross sectional area smaller than said cross sectional area of said access port; compressing said flexible cover to said compressed cross sectional area and passing said flexible cover through said access port into said enclosed volume of said storage tank; unfurling said flexible cover from said compressed cross sectional area to said uncompressed cross sectional area so that said flexible cover covers said upper surface of said hydrocarbon or other liquid; extending a conduit through said storage tank into said enclosed volume, through a space defined by an inset in said flexible cover, and below said upper surface of said hydrocarbon or other liquid, wherein said conduit has an open upper end and an open lower end; and depositing a hydrocarbon or other liquid through said conduit to said open lower end at a location below said upper surface of said hydrocarbon or other liquid, wherein said open lower end of said conduit is offset from said bottom of said storage tank by a predetermined distance.

12. The method of claim 11, further comprising: providing said flexible cover with a first membrane having a valve, said first membrane interconnected to a second membrane to define a cavity; and operating said valve when said flexible cover is in said enclosed volume of said storage tank to inflate said cavity with air to reduce a bulk density of said flexible cover.

13. The method of claim 12, further comprising providing an inflatable tube in said cavity, wherein said valve is operatively interconnected to said inflatable tube such that said valve allows air into said inflatable tube to inflate said cavity.

14. The method of claim 11, further comprising extending a tether from said flexible cover to an inner surface of said storage tank to maintain a relative orientation between said flexible cover and said storage tank, and providing a weight on an end of said tether to keep said tether taut between said inner surface of said storage tank and said flexible cover.

15. The method of claim 11, further comprising: providing a flexible flap around a perimeter edge of said flexible cover, said flexible flap is configured to form a seal with an inner surface of said outer wall of said storage tank.

16. The method of claim 11, wherein the at least one membrane is a continuous first membrane and a continuous second membrane joined to each other about a perimeter edge to define a cavity.

17. The method of claim 16, further comprising: inflating said cavity from a first volume to a larger second volume.

18. The method of claim 11, wherein the access port is a thief hatch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the disclosure and together with the general description of the disclosure given above and the detailed description of the drawings given below, serve to explain the principles of the disclosures.

(2) FIG. 1 is a diagram of a typical oil production tank battery in accordance with an embodiment of the present invention;

(3) FIG. 2 is a cross sectional front elevation view of a cover in a storage tank in accordance with an embodiment of the present invention;

(4) FIG. 3A is a perspective view of a cover in accordance with an embodiment of the present invention;

(5) FIG. 3B is a cross sectional view of a cover taken along line 3B-3B in FIG. 3A in accordance with an embodiment of the present invention;

(6) FIG. 4A is a perspective view of another cover in accordance with an embodiment of the present invention;

(7) FIG. 4B is a cross sectional view of a cover taken along line 4B-4B in FIG. 4A in accordance with an embodiment of the present invention;

(8) FIG. 5 is a cross sectional view of another embodiment of a cover;

(9) FIG. 6A is a perspective view of a cover in accordance with an embodiment of the present invention; and

(10) FIG. 6B is a partial cross sectional view of a cover taken along line 6B-6B in FIG. 6A in accordance with an embodiment of the present invention.

(11) To assist in the understanding of the embodiments of the invention the following list of components and associated numbering found in the drawings is provided herein:

(12) TABLE-US-00001 Component No. Component 10 Flexible Cover 14 Storage Tank 16 Access Port 18 Inlet Fitting 22 Conduit 26 First Inset 30 Grommet 34 Tether 38 Weight 42a, 42b Membranes 46 First Flap 50 Second Inset 54 First Valve 58 Inflatable Cavity 62 Inflatable Tube 66 Second Valve 70 Second Flap 74 Flap Angle

(13) It should be understood that the drawings are not necessarily to scale, and various dimensions may be altered. In certain instances, details that are not necessary for an understanding of the invention or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein.

DETAILED DESCRIPTION

(14) The invention has significant benefits across a broad spectrum of endeavors. It is the Applicant's intent that this specification and the claims appended hereto be accorded a breadth in keeping with the scope and spirit of the invention being disclosed despite what might appear to be limiting language imposed by the requirements of referring to the specific examples disclosed. To acquaint persons skilled in the pertinent arts most closely related to the invention, a preferred embodiment that illustrates the best mode now contemplated for putting the invention into practice is described herein by, and with reference to, the annexed drawings that form a part of the specification. The exemplary embodiment is described in detail without attempting to describe all of the various forms and modifications in which the invention might be embodied. As such, the embodiments described herein are illustrative, and as will become apparent to those skilled in the arts, and may be modified in numerous ways within the scope and spirit of the invention.

(15) Although the following text sets forth a detailed description of numerous different embodiments, it should be understood that the detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims. To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term by limited, by implication or otherwise, to that single meaning.

(16) Various embodiments of the invention are described herein and as depicted in the drawings. It is expressly understood that although the figures illustrate covers, floating covers, flaps, etc., the invention is not limited to these embodiments.

(17) Now referring to FIG. 1, a typical oil production tank battery is provided. Oil, gas, and water flow from the well to a separator where the oil, gas, and water are separated from each other. Then, the water flows to a water storage tank, the gas flows to a pipeline or to a flare, and the oil flows to a storage tank generally operated at an ambient pressure. In the storage tank, residual gas in the oil and oil vapors are emitted through the tank vent. The oil gathers in the storage tank until there is enough oil to fill a transport truck.

(18) Now referring to FIG. 2, a system having a flexible cover 10 positioned over a hydrocarbon or other liquid in a storage tank 14 is provided. As shown, the flexible cover 10 substantially covers an upper surface of the hydrocarbon or other liquid and, in some embodiments, a perimeter edge of the flexible cover 10 contacts an inner surface of the storage tank 14 to form a seal. In this position, the flexible cover reduces the amount of vapor released by the hydrocarbon or other liquid.

(19) It will be appreciated that in some embodiments, the flexible cover 10 has only a single layer or membrane. The single membrane can include a plurality of air pockets to reduce the bulk density of the membrane and the flexible cover 10 relative to the bulk density of the liquid in the storage tank 14. It will be further appreciated that in some embodiments, the flexible cover 10 has a bulk density that is less than the bulk density of the liquid in the storage tank 14. In some embodiments, the flexible cover 10 has a bulk density that is 80% or less than the bulk density of the liquid in the storage tank 14. In yet further embodiments, the flexible cover 10 has a bulk density that is 60% or less than the bulk density of the liquid in the storage tank 14. Further embodiments of the flexible cover 10 are depicted in FIGS. 3A-6B.

(20) In the depicted embodiment, a conduit 22 extends from an inlet fitting 18 of the storage tank 14, through a first inset 26 of the cover 10, and into the liquid below an upper surface of the liquid. With this conduit 22 additional liquid can be added to the storage tank 14 without splashing liquid on the top of the flexible cover 10.

(21) Also shown in FIG. 2 is a grommet 30 on the flexible cover 10 that allows an operator to retrieve the flexible cover 10 or to orient the flexible cover 10 relative to the storage tank 14 by the use of a line or tether 34 or a removable pole of any sort. The tether 34 extends from the flexible cover 10 to an inner surface of the storage tank 14. In some embodiments, the tether 34 extends through an eyelet or similar structure of the storage tank 14. This configuration allows a weight 38 to be attached to an end of the tether 34, which allows the tether 34 to remain taught. As a result, the tether 34 maintains the relative orientation of the flexible cover 10 and the storage tank 14 and so that an access port 16 can remain over a particular portion of the cover 10.

(22) Now referring to FIGS. 3A and 3B, one embodiment of a flexible cover 10 is provided. FIG. 3A is a perspective view of the flexible cover 10 that shows a first, or top, membrane 42a that has a circular shape. The first membrane 42a can combine with a second membrane 42b to form the flexible cover 10 as shown in FIG. 3B. Once installed in the enclosed volume of a storage tank, the perimeter edge of the membranes 42a, 42b extend to the inner surface of an outer wall of the storage tank 14. In some embodiments, an optional flexible flap 46 extends from the membranes 42a, 42b to the inner surface of the outer wall of the storage tank 14, and forms a seal with the inner surface to more effectively prevent flashing of the hydrocarbon liquid or evaporation of the stored liquid.

(23) The membranes 42a, 42b may be made from chemically inert material so as not to interact with hydrocarbons or other liquid, air, the material of the storage tank, or any other materials in the system. Examples of possible materials include polymers such as nylon and polyethylene, or other materials which are substantially impermeable to hydrocarbon vapors or gases. Such materials may be coated with other treatments to further impede the flashing of vapors and protect the material. In addition, the membranes material may be flexible to allow the cover to roll, or otherwise change shape, to a reduced cross sectional diameter or area to fit through the maximum diameter or cross sectional area of an access port or inlet fitting in the storage tank.

(24) As shown in FIG. 3A, one or more insets 26, 50 may be positioned on the perimeter edge of the first membrane 42a and the cover 10. A first inset 26 provides access from the access port of the storage tank to the upper surface of the hydrocarbons or other liquid in the storage tank 14, and the first inset 26 further provides access to the bottom of the storage tank 14 through the hydrocarbons or other liquids such that any pipe or conduit that can run from the top of the storage tank 14 into the liquid. The second inset 50 can provide, for instance, access to the grommet 30 or other feature for maintaining the orientation and position of the flexible cover 10 relative to the storage tank.

(25) FIG. 3B shows a cross sectional view of the flexible cover 10 taken along line 3B-3B of FIG. 3A. First and second membranes 42a, 42b are shown. The first and second membranes 42a, 42b may be mechanically joined together along perimeter edges of the first and second membranes 42a, 42b. It will be appreciated that the perimeter edges of the first and second membranes 42a, 42b may be joined by non-mechanical means, for example, an adhesive or sealant. Further, the flexible flap 46 may be used to join the first and second membranes 42a, 42b.

(26) A cavity 58 is formed between the first and second membranes 42a, 42b, and an air/liquid valve 54 on one of the membranes 42a, 42b provides access to the cavity 58. Therefore, once the flexible cover 10 is placed in the enclosed volume of the storage tank, the air/liquid valve 54 may be operated to allow air or other gases or liquids into the cavity 58, which inflates the flexible cover 10 to its original shape or to a shape that covers the most surface area of a liquid in the storage tank. In some embodiments, the pressure within the cavity 58 can range between approximately 0 and 15 psig. It will be appreciated that there are many ways to inflate the cavity 58 including allowing ambient air into a cavity 58 that has open-cell foam where the cells expand from a compressed state to an uncompressed state and draw in air, a user blowing into the cavity 58, a pump, a propellant such as nitroguanidine, phase-stabilized ammonium nitrate (NH4NO3) or other nonmetallic oxidizer, and a nitrogen-rich fuel different from azide (e.g. tetrazoles, triazoles, and their salts).

(27) Now referring to FIGS. 4A and 4B, a second embodiment of the flexible cover 10 is provided. FIG. 4A is a perspective view of the flexible cover 10, and FIG. 4B is a cross sectional view of the flexible cover 10 taken along line 4B-4B in FIG. 4A. This flexible cover 10 has many features similar to those of the flexible cover 10 in FIGS. 3A and 3B. For instance, the flexible cover 10 in FIGS. 4A and 4B has membranes 42a, 42b, a flap 46, insets 26, 50, and a valve 66.

(28) However, the valve 66 in the flexible cover 10 in FIGS. 4A and 4B is operatively interconnected to an inflatable tube 62. After the flexible cover 10 is installed in the enclosed volume of the storage tank, the valve 66 may be actuated to allow air into the inflatable tube 62, which causes the flexible cover 10 to return to its original shape, or otherwise extends the flexible cover's optional flap to cover the most surface area of a liquid in the storage tank. The inflatable tube 62 in FIGS. 4A and 4B is a ring, but it will be appreciated that the inflatable tube 62 may have a variety of shapes and configurations, including multiple interconnected chambers, electronic control systems, etc.

(29) It will be further appreciated that the cavity in which the inflatable tube 62 is positioned may also be inflatable or collapsed in some embodiments. In the collapsed embodiments, the cross sectional profile of the flexible cover 10 would generally be flat with the exception of the location of the inflatable tube 62. Further still, in some embodiments, a single membrane has the inflatable tube 62 embedded within the membrane, and the single membrane has a generally constant cross sectional profile with the exception of the location of the inflatable tube 62. As shown in FIG. 5, the flexible cover 10 may have a single membrane with an inflatable tube 62 positioned on the membrane. In addition, the flexible cover 10 in FIG. 5 has a valve 66 operably interconnected to the inflatable tube 62 and flaps 46 extending to an inner surface of a storage tank.

(30) Now referring to FIGS. 6A and 6B, a perspective view of a flexible cover 10 and a cross sectional view of the flexible cover 10 taken along line 6B-6B of FIG. 6A are provided, respectively. These figures show the optional flap 70 where the flap 70 floats towards an upper surface of a liquid at a flap angle 74 during normal operation in a storage tank, which seals off the liquid from the vapor space of the storage tank. When access to the tank bottom is needed, the flap 70 can be pushed downward into the liquid.

(31) In further embodiments, a device such as a spray gun may be used to introduce a film or layer on the upper surface of the hydrocarbons or other liquid to prevent flash of vapors. The film may be similar in consistently to paraffin wax where the spray gun can heat and deliver the wax to the upper surface of the hydrocarbons or other liquid. Then, clusters of wax may combine into a film that covers the upper surface of the hydrocarbons or other liquid.

(32) While embodiments of the present invention are described with respect to oil storage tanks and hydrocarbon or other liquids, it will be appreciated that the present invention may be applied to a wider range of containers and contents of containers.

(33) The invention has significant benefits across a broad spectrum of endeavors. It is the Applicant's intent that this specification and the claims appended hereto be accorded a breadth in keeping with the scope and spirit of the invention being disclosed despite what might appear to be limiting language imposed by the requirements of referring to the specific examples disclosed.

(34) The phrases at least one, one or more, and and/or, as used herein, are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions at least one of A, B, and C, at least one of A, B, or C, one or more of A, B, and C, one or more of A, B, or C, and A, B, and/or C means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together.

(35) Unless otherwise indicated, all numbers expressing quantities, dimensions, conditions, and so forth used in the specification, drawings, and claims are to be understood as being modified in all instances by the term about.

(36) The term a or an entity, as used herein, refers to one or more of that entity. As such, the terms a (or an), one or more and at least one can be used interchangeably herein.

(37) The use of including, comprising, or having, and variations thereof, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Accordingly, the terms including, comprising, or having and variations thereof can be used interchangeably herein.

(38) It shall be understood that the term means as used herein shall be given its broadest possible interpretation in accordance with 35 U.S.C., Section 112(f). Accordingly, a claim incorporating the term means shall cover all structures, materials, or acts set forth herein, and all of the equivalents thereof. Further, the structures, materials, or acts, and the equivalents thereof, shall include all those described in the summary of the invention, brief description of the drawings, detailed description, abstract, and claims themselves.

(39) The foregoing description of the invention has been presented for illustration and description purposes. However, the description is not intended to limit the invention to only the forms disclosed herein. In the foregoing Detailed Description for example, various features of the invention are grouped together in one or more embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate preferred embodiment of the invention.

(40) Consequently, variations and modifications commensurate with the above teachings and skill and knowledge of the relevant art are within the scope of the invention. The embodiments described herein above are further intended to explain best modes of practicing the invention and to enable others skilled in the art to utilize the invention in such a manner, or include other embodiments with various modifications as required by the particular application(s) or use(s) of the invention. Thus, it is intended that the claims be construed to include alternative embodiments to the extent permitted by the prior art.