Patent Publication Number: US-2011067761-A1

Title: Storage Tank Containment Apparatus

Description:
FIELD OF THE INVENTION 
     This invention is in the field of liquid storage equipment and in particular a containment apparatus for containing liquid that might leak from liquid storage tanks. 
     BACKGROUND 
     Large liquid storage tanks are used in a variety of industries. For example in the petroleum industry, oil is pumped from underground reservoirs to the surface at oil well sites. The oil coming from the well site is commonly connected to a pipeline system and conveyed to a central storage location through the pipeline system. Where such a pipeline system is not available however, one or more large storage tanks are placed on the well site, and the oil is pumped into the tanks. Periodically a transport will remove oil from the tanks and haul it away. 
     Where the stored liquid, such as oil, poses an environmental hazard, the storage tanks must be located inside a containment structure that is configured to contain any liquid that might be spilled from the tank. Such containment structures typically include walls supported upright on the ground and extending around the tank, and an impervious liner made from plastic or the like that covers the ground and extends generally to the top of the inside surface of the walls, thereby forming a container. The area enclosed by the walls and the height of the walls are configured to provide sufficient volume to contain the required amount of liquid, which is usually regulated in the jurisdiction where it will be used, based on the number and capacity of the tanks being contained. 
     A typical containment structure is disclosed for example in Canadian Patent Number 2,362,105 to Mackie. A plurality of wall panels are connected end-to-end with corners as required to form an enclosure and the liner is laid on the ground and up over the top of the wall panels. Braces extend from the ground to the top of the wall outside the wall. The storage tanks are placed on the liner inside the enclosure. 
     In a typical oil well site then, a conduit extends along the ground from the oil well output to the wall, then up over the wall and down along the inside of the wall to the ground, and then along the ground to the tank where it is connected to a port in the wall of the tank, such that oil can flow from the well output into the tank. Valves are also provided to allow for connection of conduits to remove oil from the tanks. 
     Thus the typical containment structure is quite time consuming to erect. As well, the conduit needs to have a number of elbows to go up and over the wall, which increases the risk of leaks, and also increases the cost and the time to connect the oil well to the tank, and restricts flow to the tank, increasing the pressure required to push the oil to the tank. Going up and over the wall can also provide a liquid trap where liquid gathers in the conduit when idle, and which can be subject to freezing and disruption of flow to the tank. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a containment apparatus for storage tanks that overcomes problems in the prior art. 
     The present invention provides, in a first embodiment, a secondary containment apparatus for storage tanks. The apparatus comprises a floor, and side walls extending upward from a perimeter of the floor, wherein the side walls are sealed to the floor to form a containment structure. The floor and the side walls are configured such that the side walls are supported in an upright orientation, and a plurality of lifting lugs are configured for connection to a crane for lifting the apparatus. The containment structure is configured to be placed on a transport vehicle for transport along a public road. 
     The present invention provides, in a second embodiment, a storage tank apparatus comprising a containment structure configured to be placed on a transport vehicle for transport along a public road. The containment structure comprises a rectangular floor and four side walls extending upward from a perimeter of the floor, wherein the side walls are welded to the floor and to adjacent sidewalls, and the floor and the side walls are configured such that the side walls are supported in an upright orientation. A plurality of lifting lugs are configured for connection to a crane for lifting the apparatus. First and second storage tanks are supported on the floor inside the containment structure, and each storage tank is connected by a conduit to an oil well production output. 
     The present invention provides, in a third embodiment, a method of providing secondary containment for at least one storage tank at a work site. The method comprises assembling a containment structure with a floor and side walls extending upward from a perimeter of the floor, sealing the side walls to the floor; supporting the side walls in an upright orientation; and attaching a plurality of lifting lugs to the containment structure. When the containment structure is assembled connecting an assembly site crane to the lifting lugs and lifting the containment structure on to a transport vehicle, disconnecting the assembly site crane, and transporting the containment structure along a public road to the work site; preparing a pad with a substantially level top surface in a desired location at the work site; connecting a work site crane to the lifting lugs and lifting the containment structure off the vehicle and placing the containment structure on the top surface of the pad; connecting the work site crane to the at least one storage tank and lifting the at least one storage tank over a top edge of the side walls of the containment structure and placing the at least one storage tank on the floor of the containment structure. 
     Thus the invention provides a one piece containment apparatus that can be transported as single unit to a work location and placed on the ground without further construction. Conveniently the apparatus is made from welded steel and the inside is coated with epoxy or the like to protect the steel. The apparatus includes required bracing and support for transport. Braces are located inside the containment structure such that the braces do not extend outside the walls so that the transport width can be kept to a minimum. 
     To facilitate connection to a supply conduit, such as the output from an oil well, threaded or flanged ports can be provided through lower portions of the walls so that the outer supply conduit from the well output can run along the ground and be sealed to the outside of the port. Then the inner supply conduit from the tank can be sealed to the inside of the port, such that the supply conduit extends through the wall instead of over the wall, making a simpler connection, with reduced pressure loss and reduced risk that liquid will be trapped in the supply conduit. A plurality of ports can be provided to accommodate more than one tank, or to provide increased options for connecting to the supply conduit. 
     The one-piece construction of the present invention reduces the time and labor required to set up the containment apparatus in the desired working location. The port through the wall allows for convenient connection of a conduit to the tank inside the containment apparatus. The present invention can be used wherever contained storage of materials other work sites such as oil wells, mines, and like industries. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where: 
         FIG. 1  is a schematic perspective view of an embodiment of a containment apparatus of the present invention; 
         FIG. 2  is schematic sectional view along lines  2 - 2  in  FIG. 1 ; 
         FIG. 3  is a schematic top view of the embodiment of  FIG. 1 , with tanks installed inside the containment apparatus; 
         FIG. 4  is a schematic sectional view of a wall port of the embodiment of  FIG. 1  connected to outer and inner supply conduits; 
         FIG. 5  is a schematic sectional view of an alternate wall port connected to outer and inner supply conduits; 
         FIGS. 6-8  schematically illustrate a method of the invention for providing secondary containment for storage tanks at a work site. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
       FIG. 1  schematically illustrates an embodiment of a one piece secondary containment apparatus  1  of the present invention. The apparatus  1  can be conveniently formed, for example, with a floor  3  and side walls  5  of steel, with the side walls  5  sealed to the floor  3  by welding to form a containment structure  10 , and supported in an upright orientation. The floor  3  and side walls  5  can be constructed of sufficiently strong material to support the walls  5 , or braces  7  can be provided. Inner surfaces  9  of the steel floor  3  and side walls  5  are coated with an epoxy or like protective material to seal and protect the steel material. 
     The braces  7  are attached inside the containment structure  10  to the floor  3  and side walls  5  as required to provide sufficient rigidity to the apparatus  1  to allow same to be loaded on a transport vehicle and transported on a on a public road, and to be substantially free standing at the working location. Locating the braces  7  inside the containment structure  10  allows the transport width to be about the same as the width of the containment structure  10 . The top of the wall  5  can be formed as illustrated in  FIG. 2  to provide increased strength and rigidity. A plurality of lifting lugs  11  are configured for connection to a crane for lifting the apparatus  1  onto and off of a vehicle. 
     The area enclosed by the walls  5  and the height of the walls  5  are calculated so that the apparatus  1  can contain all the liquid that is stored in the tanks that will be located in the apparatus  1 . As an example and as schematically illustrated in  FIG. 3 , the floor  3  is rectangular with four side walls  5  with each side wall sealed to adjacent side walls  5  at each end thereof, as well as to the floor  3 . Other shapes could be used as well that are suited to a particular application, for example circular, oval, square, or whatever is suitable in a given application. 
     In order to contain two common 400 barrel tanks, each about 12 feet in diameter, the containment structure  10  of the apparatus  1  could be about 20 feet wide, 40 feet long and have walls  5  that are about 3.5 feet high to satisfy capacity requirements in a particular jurisdiction. The weight is about 11,000 pounds which is readily carried by a truck or trailer. 
     The one piece apparatus  1  at about 20 feet wide can be transported in one piece on a trailer or the like along a public road in many jurisdictions, using pilot vehicles and warning lights as needed. 
     Once at the work site, such as an oil well site as schematically illustrated in  FIG. 3 , the apparatus can be placed on a pad, typically of compacted sand, crusher dust, or the like, with a substantially level top surface in a desired location at the work site. The bottom of the containment structure  10  is typically flat and supported on the surface of the pad, but it is contemplated that in some circumstances it will be desirable to provide skids or the like under the floor of the containment structure  10 . Further construction is not required, and so work site set up time is minimal, 
     Some tanks come with a base  12  onto which the tank  13  is mounted but many tanks do not include such a base and the tank  13  is simply placed on the floor  3  of the containment structure  10  of the apparatus  1 . Once the apparatus  1  is in place at the site, the tanks  13  are raised over the wall  5  of the apparatus  1  by a crane, and placed in the desired location on the floor  3  of the apparatus  1 , or on the base provided. This crane can be used to both place the apparatus  1  on the ground, and then place the tanks  13  inside the apparatus  1 .  FIG. 3  shows one tank  13 A located on a base, and the other tank  13 B resting on the floor  3 . Typically bridge planks will be laid on the floor  3  to protect the floor, and the tanks  13  will be placed on top of the bridge planks. 
     At the oil well site in  FIG. 3 , as an example of an industry where the invention can be used, there are shown two separate oil wells  17 , each with an output  19 . To facilitate connection of supply conduits  21  from the outputs  19  to the tanks  13 , wall ports  23  are provided through lower portions of the walls  5  adapted at outer and inner sides  23 A,  23 B thereof for connection to a conduit. Each outer supply conduit  21 A, which lies outside the containment structure  10  of the apparatus  1 , is connected at one end to the well output  19  and runs along the ground or supported somewhat above the ground to the opposite end which is connected and sealed to the outer side  23 A of the wall port  23 . 
     The inner supply conduit  21 B, which lies inside the apparatus  1 , is connected at one end to a tank port  25  of the tank  19  and runs along the ground or supported somewhat above the ground to the opposite end which is connected and sealed to the inner side  23 B of the port  23 . Thus the resulting complete supply conduit  21  comprises outer and inner supply conduits  21 A,  21 B passing through the wall  5  just above the ground, with the resulting reduced complexity of piping. It is also contemplated that in some situations it may also be desired to provide wall ports  23  in higher portions of the wall  5 . 
     A number of wall ports  23  can be provided at various locations along the side walls  5  to provide increased options and allow for other connections to the tanks through the wall, or for greater versatility in placing the tanks  13  by providing optional routes for the supply conduit  21 . These additional wall ports  23  can be sealed off with a cap  24  or the like when not in use to seal the wall  5 . 
     The wall port  23  can be flanged as schematically illustrated in  FIG. 4  where the outer and inner conduits  21 A,  21 B are attached to the corresponding outer and inner sides  23 A,  23 B of the wall port  23 , by connecting bolts  27  through holes in the flanges  29  as is known in the art. The resulting complete supply conduit  21  passes through the wall  5  just above the floor  3 . 
       FIG. 5  schematically illustrates a threaded wall port  123  where threaded outer and inner conduits  121 A,  121 B are connected to threaded outer and inner sides  123 A,  123 B of the wall port  123  by a threaded coupler  131 . It is contemplated that other connection means known in the art could also be used to connect the supply conduits to the wall port. 
     There may also be only a single oil well producing at a work site, in which case it may be desirable to connect the single production output  19  to both storage tanks  13 . As schematically illustrated in  FIG. 3 , inner conduit  21 X from a tank port  25  on tank  13 A can be connected in a T-junction with the inner conduit  21 B from tank  13 B such that both tanks  13 A,  13 B are connected to the inner side of the same wall port  23 , and thus to a single oil well production output such that the output fluid will be stored in both tanks  13 . 
     The present invention thus provides a method of providing secondary containment for storage tanks  13  at a work site. The method comprises assembling a containment structure  10  with a floor  3  and side walls  5  extending upward from a perimeter of the floor  3 , and sealing the side walls  5  to the floor  5 . A plurality of braces  7  are attached to the floor  3  and the side walls  5  inside the containment structure  10  and are configured to support the side walls  5  in an upright orientation. 
     A plurality of lifting lugs  11  are attached to the containment structure  10 , and an assembly site crane  31  is connected to the lifting lugs  11  by cables  33  and the crane  31  lifts the containment structure  10  off the ground and onto a transport trailer  35 , as schematically illustrated in  FIG. 6 . The assembly site crane  31  is disconnected, and the containment structure  10  is transported along public roads to the work site where a pad  37  with a substantially level top surface has been prepared in a desired location at the work site as schematically illustrated in  FIG. 7 . 
     At the work site, a work site crane  39  is connected to the lifting lugs  11  and lifts the containment structure  10  off the trailer  35  and places the containment structure  10  on the top surface of the pad  37  such that the containment structure  10  rests on the top surface of the pad  37 . Once the containment structure  10  is in place, the work site crane is connected to a storage tank  13  and lifts the storage tank  13  over a top edge of the side walls  5  of the containment structure  10  and places the storage tank  13  on the floor of the containment structure  10  as schematically illustrated in  FIG. 8 . 
     As described above, outer conduit  21 A is connected to a tank port  25  on the storage tank by providing a wall port  23  extending through a lower portion of a side wall  5  and connecting the outer conduit  21 A to an outer side of the wall port  23 , and connecting an inner conduit  21 B from an inner side of the wall port  23  to the tank port  25 . 
     The present invention provides a significant time and labor advantage over prior art storage tank containment systems where containment walls must be erected at the work site and braced in an upright orientation and then a liner placed over the ground and up the walls. The present one piece containment structure can be loaded on a trailer or truck and hauled to a prepared pad and simply lifted off the trailer onto the pad. Generally a crane will be used to move the storage tanks and so will be available to place the containment structure. Plumbing the storage tanks to an external supply is facilitated by providing a wall port through a lower portion of the wall so the conduits do not have to bend up and over the wall as in the prior art. 
     The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.