US20070056975A1

US20070056975A1 - Double walled tank

Info

Publication number: US20070056975A1
Application number: US11/224,748
Authority: US
Inventors: Dwayne Long; Scott Higgins; John Redmond; Dwayne Holden; Robert Letterman
Original assignee: Custom Metalcraft Inc
Current assignee: Custom Metalcraft Inc
Priority date: 2005-09-12
Filing date: 2005-09-12
Publication date: 2007-03-15

Abstract

A double walled tank (12) is provided which includes an outer shell (14), a telescopically interfitted inner shell (16), and a cover (18) secured to outer shell (14). The tank (12) includes at least one spacer (48) located between the inner and outer shells (16, 14), as well as resilient seals (38, 72) serving to maintain an appropriate and safe spacing gap between the shells (14, 16). The inner shell (16) includes a top wall (38) equipped with a fill opening (52) defined by an upstanding central flange (50, 50 a) surmounted by a detachably secured cover (54, 54 a).

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention is broadly concerned with an improved double walled tank assembly having telescopically interfitted inner and outer shells sized and configured in cube-efficient dimensions. More particularly, the invention is concerned with such double walled tank assemblies having the inner and outer shells maintained in a stable, spaced-apart relationship by means of spacers disposed within the gap between the shells. A detachable cover is secured to the outer shell and allows access to the inner shell top wall having a fill opening.
2. Description of the Prior Art
Portable tanks are used extensively for the storage and transport of hazardous materials. To be most efficient, such portable tanks must be of a size and configuration that lend themselves to transport in standard over-the-road vehicles and containers. Single walled tanks are commonly constructed with these size considerations in mind. However, single walled tanks do not provide the same measure of protection against spillage as do double walled tanks.
Double walled tanks have been proposed in the past, see e.g., U.S. Pat. Nos. 4,782,973, 6,484,899, 6,272,021, 5,687,757, 5,373,961, 4,930,661, 2,706,575, 2,495,798, 2,640,355, 1,657,283, and GB 894,173. Generally, prior double walled tanks have been constructed by first fabricating a more or less conventional single walled tank, and then creating an outer shell by piecewise welding or other attachment of shell components to the existing tank. This is a relatively expensive technique, and moreover inevitably results in welded connections between the inner tank and the outer cladding, thus making it impossible to replace the inner tank.
The assignee of the present invention previously sold a double walled tank that employed an inner and outer shell. The outer shell was not created by piece-wise welding of components to the existing inner tank. Rather the outer shell was created with spacers provided to maintain separation between the inner shell and outer shell once the inner shell was placed within the outer shell. However, this prior double wall tank suffered from the same drawbacks discussed above in that the inner shell was welded to the outer shell at least at the top and drainage ports. The welding prevented removal of the inner shell from the assembly. Additionally, the spacers spanned the sides of the inner shell creating compartments that prevented the free flow of liquid between the inner and outer shells.
There is accordingly a need in the art for improved double walled tanks which can be fabricated in a modular fashion without welded connections between the inner tank and outer components, which allow for liquid flow in the space between the inner and outer shells, and which are sized in a cube-efficient manner allowing the tanks to be stored and shipped in conventional storage and transport equipment.

SUMMARY OF THE INVENTION

The present invention overcomes the problems outlined above and provides a double walled tank assembly comprising an outer shell including an outer shell bottom wall and upright outer shell sidewall structure secured to and extending upwardly from the outer shell bottom wall and defining an upper open end. The overall assembly also has an an inner shell disposed within said outer shell and comprising an inner shell bottom wall, upright inner shell sidewall structure secured to and extending upwardly from the inner shell bottom wall, and an inner shell top wall secured to the inner shell sidewall structure adjacent the upper end thereof. In order to maintain a proper spacing or gap between the outer and inner shells, a plurality of spacers are located between the shells. The tank assembly is surmounted by a cover operably secured to the outer shell adjacent the upper end thereof and is disposed at least partially over the upper open end of the outer shell.
In preferred forms, the spacers are located between adjacent side walls and bottom walls of the inner and outer shells, and are affixed to the outer surface of the inner shell, thereby facilitating telescopic interfitting of the shells during constructions. Also, resilient seal structure is provided adjacent the top and bottom of the tank assembly for resiliently maintaining the shells in a desired spaced apart relationship. The spacers are designed to allow the flow of liquid in the outer shell to facilitate drainage of the outer shell or the provision of insulative or barrier materials between the shells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a double walled tank in accordance with the invention, illustrating the drain valve assembly at the lower end of the tank;
FIG. 2 is an elevational view similar to that shown in FIG. 1, but viewing the tank from the end thereof;
FIG. 3 is a plan view of the tank depicted in FIGS. 1 and 2;
FIG. 4 is a bottom view of the tank depicted in FIGS. 1 and 2;
FIG. 5 is a vertical sectional view taken along line 5-5 of FIG. 1 and illustrating the preferred placement of spacers between the inner and outer shells of the tank;
FIG. 6 is an exploded view of a preferred double walled tank of the invention, illustrating the inner and outer shells in a separated condition, and the top cover disposed above the shells;
FIG. 7 is an enlarged, fragmentary view in vertical section depicting one form of connection of the openable fill cover of the tank;
FIG. 8 is a fragmentary view in partial vertical section illustrating the inner shell drain pipe and associated drain valve assembly;
FIG.9 is an enlarged, fragmentary view in vertical section depicting another form of connection of the openable fill cover of the tank;
FIG. 10 is an enlarged, fragmentary view in vertical section depicting another form of connection of the openable fill cover of the tank;
FIG. 11 is an enlarged, fragmentary view in vertical section depicting still another form of connection of the openable fill cover of the tank;
FIG. 12 is an enlarged, fragmentary view in partial vertical section illustrating the outer shell and a form of connection of the outer shell top with the main body;
FIG. 13 is an enlarged, fragmentary view in vertical section depicting another form of connection of the removable cover of the outer shell with the body of the outer shell of the tank; and
FIG. 14 is an enlarged, fragmentary view in vertical section depicting one form of spacer between the inner and outer shells of the tank.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, a double wall tank 12 is in the form of an upright, liquid-holding tank which is generally quadrate (e.g., rectangular) in cross-section and includes telescopically interfitted outer and inner shells 14 and 16, respectively, and cover 18 operably secured to outer shell 14. The tank 12 is designed for the secure storage and transit of materials including, e.g., dangerous liquids, and is of a size and configuration for transportation enclosed transport vehicles such as conventional trucks, trailers and sea vans.
In more detail, the outer shell 14 includes a bottom wall 20 as well as upstanding, interconnected sidewall structure 22 secured to and extending upwardly from bottom wall 20 and defining an upper open end 24. Four corner-mounted legs 26 are secured to the shell 14 adjacent the bottom wall 20 thereof in order to elevate the tank above a supporting surface. The bottom wall 20 has an opening 28 formed therein (see FIG. 8) with an annular resilient seal 30 located around the opening 28 as shown. Bottom wall 20 also has a drain plug 27, that preferably includes a lead or polymer core forming a fuse venting device that blows when temperatures and pressures reach a predetermined level. In preferred embodiments the plug is made from a threaded outer steel ring with a ½ inch diameter center fuse material. The plug allows for drainage of the outer shell 14 separately from inner shell 16, discussed below. Finally, as best seen in FIGS. 4 and 8, a depending guard wall 32 is secured to and extends between an adjacent pair of legs 26, which is important for purposes to be made clear.
Inner shell 16 comprises a bottom wall 34, upstanding sidewall structure 36 connected to and extending upwardly from bottom wall 34, and a top wall 38 secured to sidewall structure 36 at the upper end thereof. The bottom wall 34 is equipped with a downwardly extending, threaded drain pipe 40 permitting draining of shell 16. Again referring to FIG. 8, it will be seen that the seal 30 engages the outer surface of drain pipe 40 to maintain a liquid-tight seal. The lower end of pipe 40 has an elbow 42, which in turn is connected to and supports a conventional gate-type drain valve 44, which is operable by manipulation of handle 46. The inner shell bottom wall 34 may be tapered to allow for maximum fluid drainage. The inner shell may optionally be provided with one or more drain plugs similar to plug 27 described above with respect to the outer shell. Guard wall 32 protects the drain pipe 40, elbow 42, drain valve 44, and handle 46 such that the tank, when standing upright on its legs, may be approached by a forklift on three sides. The lift can insert its forks between the bottom wall 20 and the surface the tank is standing on without damaging the drain assembly because of the presence of wall 32. The drain assembly may additionally be protected by an optional security door 33 (FIGS. 15, 16). The door is preferably connected by hinges to the outer shell and may be secured in place by a latch or lock to prevent tampering with the valve assembly and reduce the likelihood of an inadvertent or even intentional discharge of materials from within the inner shell. The door may extend partway or all the way across the tank side with the valve assembly as desired.
A plurality of spacers 48 are welded or otherwise affixed to the outer surface of inner shell bottom wall 34 and sidewall structure 36, in order to maintain the spacing between the inner and outer shells without welds therebetween. In a preferred embodiment the spacers 48 are tubular with a square cross section allowing for the free flow of liquid in the gap created by the spacers. The spacers, however, may have any desired shape and cross section suitable to maintain the gap. In another embodiment spacer 48 a has a “Z” shaped cross section and acts as a spring (see FIG. 14) or shock absorber. The spacers may be made of any material suitable to performing the function including for example, metal or plastic. The combination of flexible seals described herein and the spacers 48 allows the inner shell to “float” within the outer shell. Moreover, the combination of flexible seals and spacers allows the inner shell to be placed within the outer shell without the need for welding connections between the two shells. This allows for replacement or cleaning of the inner shell.
In another embodiment, spacers 48 b may be made from a webbing, or preformed panel, made from any suitable material but preferably from a plastic or polymeric material and most preferably from a polymer that is more fully described in U.S. Pat. No. 6,805,815, which is incorporated herein by reference in its entirety. The spacers 48 b in a panel format may be formed of a pattern similar to the shape of the interior of an egg carton, to allow for the free flow of liquid between the inner and outer shell in the space created by the web (FIG. 17). One side of spacer 48 b is flat and the other has the familiar egg carton shape. When using such polymer based spacers, the panels could be used without attaching them to either shell. A base panel can be inserted into the outer shell followed by the inner shell and then side wall spacers (FIG. 16). When such preformed panels or webbing are used as the spacer material, and are formed of a non-metal such as the polymer referenced above, metal-to-metal contact between the inner and outer shells is prevented over substantially all of the surface area of the tank. This arrangement advantageously prevents the conduction of heat from the inner to outer shell or vice versa.
Top wall 38 of inner shell 16 includes an upstanding, generally central, circular in cross-section, integral flange wall 50, which defines a fill opening 52 for the tank 12. An openable cover 54 is positioned atop flange wall 50 and permits access to inner shell 16 for fill or emptying purposes. The flange wall 50 has an uppermost, circumferentially extending, metallic bead 56 welded to the upper margin thereof, which facilitates attachment of cover 54. Referring specifically to FIGS. 3 and 7, it will be noted that the cover 54 has a central, fusable, pressure relief cap 58, as well as a secondary gasketed plug 60. The outer peripheral margin of cover 54 has an arcuate lip 62 which conforms with bead 56. In order to create a releasable connection of cover 54 to flange wall 50, a circumferential, resilient seal 64 is located about bead 56 and lip 62 is then placed over the seal 64. The connection is completed by means of a clamp ring 66 which can be tightened via screw 68.
Cover 18 is designed for connection to the open upper end 24 of outer shell sidewall structure 22 by means of welding or, if desired, a conventional threaded coupling arrangement. The cover 18 has four corner-mounted lifting lugs 69, a central opening 70 which accommodates upstanding flange wall 50 of inner shell top wall 38, and a secondary drain plug 71. Preferably, the inner margin of cover 18 defining opening 70 engages a peripheral 0-ring seal 72 located adjacent the outer surface of flange wall 50 and below the cover 18.
FIGS. 12 and 13 show an alternative outer shell top 18 a. Top 18 a differs from top 18 in that it may be fastened onto outer shell 14 using fasteners 90. In this embodiment, outer shell 14 has a peripheral rim 92, having openings 94 to allow passage of the fasteners 90 (in this case bolts). Top 18 a has a matching rim 96 with openings 98 for fasteners 90. Use of the fasteners facilitates removal of top 18 a to allow cleaning of outer shell 14 and inspection, repair, replacement, or cleaning of inner shell 16.
Referring next to FIG. 9, an alternative flange wall and cover arrangement, also known as a universal manway, is illustrated. In this case, an upstanding flange wall 50 a is welded to inner shell top wall 38. A circular, laterally extending apertured flange 74 is welded to the upper end of wall 50 a, and has a short upstanding wall 75 surmounted by a circumferential bead 76 adjacent the outboard edge thereof. In this case, the universal manway cover 54 a has a substantially flat, apertured outer margin and is secured to flange 74 by a series of bolt-and-nut connectors 78 placed through openings 81 and an intermediate resilient seal 80.
FIG. 10 illustrates another cover attachment arrangement for the universal manway described in FIG. 9, including the basic structure of FIG. 9, namely flange wall 50 a, flange 74, wall 75, and bead 76. In this case, however, the cover 54 is configured in the manner of FIG. 7, with an arcuate lip 62 a designed to mate with bead 76. In this instance, a circumferential seal 64 a is provided about bead 76, with lip 62 a engaging seal 64 a. An imperforate resilient seal 80 a is located atop flange 74, and is engaged by a flat segment 82 of cover 54. As can be seen, the lid seals the bolt hole openings 81 when bolts are not in use. A clamp ring 66 is then employed to complete the releasable connection of the cover 54. The Universal manway of FIGS. 9-10 is unique in that it provides the user with the choice of using either bolts to secure the cover or a quick change clamp ring. While a bolted manway provides a greater degree of protection from leakage, it can be cumbersome to use. Depending on the circumstances, the user can employ an industry standard quick change clamp ring system without changing the manway.
FIG. 11 depicts a similar connection arrangement having a wall 50 a with an upper apertured flange 74. A circular, apertured seal 80 overlies flange 74, and the cover in turn is positioned atop seal 80 as shown. A plurality of connectors 78 are used to releasably secure the cover in place.
In fabrication procedures, outer shell 14 is manufactured of metal, preferably in the size and shape widely accepted for shipment and storage of hazardous materials. The inner shell 16 is separately manufactured to the same proximate shape and dimensions as the outer shell 14, less allowance for the spacers 48 although different material thicknesses may be employed for the inner and outer shell as desired. The inner and outer shells may be manufactured of different materials depending on cost considerations and the desired end use. For example, the inner shell may be manufactured from 316L grade steel or alloy 22. The outer shell may be manufactured from less expensive material or, depending on the application, more expensive material such as a strong barrier material. For example, one suitable material comprises long molecular chains produced from poly-paraphenylene terephthalamide that are highly oriented with strong interchain bonding, also known commercially as Kevlar®. As previously described, the inner shell also has a depending drain pipe 40 designed to extend through and be engaged by seal 30. The inner shell 16 is telescoped within shell 14 with pipe 40 engaged by the seal 30. At this point the cover 18 is affixed to outer shell sidewall structure 22, preferably with the provision of O-ring 72. In this fashion, the inner shell 16 is resiliently maintained in position at top and bottom between the seals 70 and 30; at the same time, the spacers 48 assure a positive and generally uniform separation between the inner and outer shells 16 and 14.
In the use of tank 12, the cover 54 may be opened, allowing the inner shell 16 to be filled with material. The cover 54 is then reattached and the tank 12 can be used for storage and/or transport of the material. In the event that inner shell 16 needs to be drained, such can be accomplished by opening cover 54; any residual material may be drained by opening gate valve 44 via handle 46. The gap between the inner and outer shells created by spacers 48 may be filled with a liquid used for temperature regulation of the material stored within inner shell 16. Such liquid can be circulated in the gap and used, e.g., for cooling. Likewise, the gap between the shells may be filled by insulating materials used to regulate inner shell temperatures or to protect the environment from hazardous radio-active material that may be stored in the inner shell for transport.
In one embodiment the gap between the shells may be filled by the polymer described in U.S. Pat. No. 6,805,815, which, after set up and hardening, acts as a barrier preventing radiation from radio active materials stored within the inner shell escaping through the barrier and the outer shell and into the environment. In this embodiment, special provision must be made to allow for the polymer barrier to entirely surround the inner shell including above fill opening 52 to ensure that the radio active materials contained within the inner shell are entirely encapsulated by the polymeric barrier. In one embodiment, there is no change to the structure depicted, for instance, at the top of FIG. 6. In this embodiment, the neck region above opening 52 in the area of flange 50 is filled with the polymeric barrier. This encloses the materials beneath opening 52. In another embodiment, the integral flange wall 50 and openable cover 54 of inner shell 16 are recessed below top cover 18 such that the polymeric barrier can entirely cover those features of the inner shell thereby encapsulating the radio active material below the fill opening 52. In this embodiment, the drain plugs 27 and 71 of outer shell 14 may advantageously be used to provide access for electronic sensors such as heat or gas sensors that can be used to monitor conditions of the assembly. Such electronic monitoring would be useful for more than the enclosure of radio active materials, but for other applications as well. This configuration is highly advantageous for the transport and storage of radio active materials.
In another embodiment the gap between the inner and outer shell may be filled with bullet deflecting or impact resistant materials such as Kevlar® as well as others known to those skilled in the art. In these embodiments highly dangerous materials may be transported or stored outside while reducing the threat of explosion or venting of hazardous material from within that may be caused by vandals or terrorists attempting to puncture the tank. In another embodiment a combination of filler materials having different characteristics may be used to fill the gap between the inner and outer shell thereby providing multiple benefits to the arrangement. For example, the bottom gap between the inner and outer shells can be filled with vibration damping material such as a foaming agent comprising polystyrene, while the side gaps are filled with a barrier agent such as Kevlar®. This combination would provide vibration damping during transport, while at the same time providing added protection against puncture of the inner shell to the most vulnerable portions of the tank assembly. Other permutations and combinations will be apparent to those of ordinary skill in the art.
In another embodiment, the gap between the inner and outer shell may be filled with liquid to facilitate maintaining the contents of the inner shell at a desired temperature. For example, if dairy products were being transported, it would be desirable to maintain the dairy product at an industry standard transport temperature of 40° F. Alternatively, wine makers often desire to closely regulate the temperature of wine during the wine making process and will desire to maintain the inner shell at certain predetermined temperatures during different phases of the process. To accomplish these goals, water or some other temperature regulating liquid could be circulated in the gap between the inner and outer shells. The liquid could be maintained externally at a known temperature and then circulated through the tank assembly. In this embodiment, the drain plugs 27 and 71 may alternatively be used as ports for the circulation of the temperature regulating liquid by a pumping system (not shown).
In another embodiment, the gap between the inner and outer shells may be filled by an insulating material. This material will facilitate maintaining the contents of the inner shell at within a desired temperature range. Suitable materials include but are not limited to rock wall, fiberglass, and other insulating materials known to those skilled in the art.
The preferred tank design affords a number of advantages not heretofore available in the art. For example, the tank may be accessed via forklift on three sides and can be lifted and moved using cables or slings by virtue of the lugs 69. The outer and inner shells can be drained separately and the outer vessel gives improved fire and explosion protection owing to the presence of venting device(s). Safety is enhanced using the tank of the invention, inasmuch as the gap between the inner and outer shells provides a high degree of puncture protection for the inner shell. The inner shell may also be removed and replace as necessary by detachment of top cover 18, thereby permitting cost-efficient tank repair.

Claims

1. A double walled tank assembly comprising:

an outer shell including an outer shell bottom wall and upright outer shell sidewall structure secured to and extending upwardly from said outer shell bottom wall and defining an upper open end;

an inner shell disposed within said outer shell without welding the inner and outer shell to each other and comprising an inner shell bottom wall, upright inner shell sidewall structure secured to and extending upwardly from said inner shell bottom wall, and an inner shell top wall secured to said inner shell sidewall structure adjacent the upper end thereof;

at least one spacer located between said inner shell and outer shell in order to maintain the inner shell in spaced relationship to said outer shell and configured to allow substantially free liquid flow between said inner and outer shell; and

a cover operably secured to said outer shell adjacent the upper end thereof and disposed at least partially over said upper open end.

2. The tank assembly of claim 1, said at least one spacer being tubular.

3. The tank assembly of claim 1, said at least one spacer having a “z” shaped cross section.

4. The tank assembly of claim 1, said at least one spacer formed from a polymeric material.

5. The tank assembly of claim 4, said at least one spacer being formed into a panel having a substantially smooth side and a patterned side.

6. The tank assembly of claim 1, including resilient seal structure adjacent the top and bottom of said tank assembly for resiliently maintaining said inner shell within said outer shell.

7. The tank assembly of claim 6, said inner shell having a drain pipe secured to said inner shell bottom wall, said outer shell bottom wall having an opening for passage of said drain pipe therethrough, there being a resilient seal adjacent said opening and engaging said drain pipe.

8. The tank assembly of claim 6, said inner shell top wall including an upstanding, continuous flange wall at the central region of the inner shell top wall, said cover having a cover opening therein and disposed about said flange wall, there being a resilient seal located between said cover and a portion of said inner shell top wall outboard of said flange wall.

9. The tank assembly of claim 7, said outer shall having a security door attached thereto for protecting said drain pipe.

10. The tank assembly of claim 1, said inner and outer shells being generally quadrate in plan configuration.

11. The tank assembly of claim 1, said outer shell having a plurality of depending legs extending below said outer shell bottom wall.

12. The tank assembly of claim 1, including a drain aperture formed in said outer shell bottom wall, there being a replaceable seal located within said drain aperture.

13. The tank assembly of claim 1, said inner shell top wall having a relief aperture formed therein, there being frangible seal disposed within said relief aperture in order to vent said inner shell in the event of an overpressure condition therein.

14. The tank assembly of claim 1, said cover being welded to said outer shell sidewall structure adjacent the upper end thereof.

15. The tank assembly of claim 1, said inner shell top wall having a fill opening provided therethrough, with an openable cover disposed across said fill opening.

16. The tank assembly of claim 1, further comprising an insulating material disposed between said inner and outer shells.

17. The tank assembly of claim 1, further comprising a barrier material disposed between said inner and outer shells.

18. The tank assembly of claim 1, further comprising a vibration absorbing material disposed between said inner and outer shells.

19. The tank assembly of claim 1, further comprising a temperature regulating liquid disposed between said inner and outer shells.

20. The tank assembly of claim 1, further comprising at least two different materials disposed between said inner and outer shells selected from the group comprising an insulating material, a barrier material, a vibration absorbing material, and a temperature regulating liquid.

21. A material container assembly comprising:

a bottom wall;

upright sidewall structure secured to and extending upwardly from said bottom wall and forming an interior space with said bottom wall for storing material;

a top wall secured to said sidewall structure having an opening therein for accessing the interior space of said material container assembly; and

a universal manway cover assembly having a flange with at least one aperture for a fastener and a circumferential bead for use with a clamp ring, said cover assembly including a cover releaseably secured over said opening.

22. The container assembly of claim 21, said universal manway cover assembly sealing said at least one aperture when said cover is clamped to said assembly.

23. The container assembly of claim 21, said universal manway cover assembly dimensioned to use an industry standard size cover and an industry standard size clamp ring.

24. The container assembly of claim 21, said universal manway cover assembly sealing said at least one aperture when said cover is fastened to said assembly.