Patent Publication Number: US-9403639-B2

Title: Modular transportable tank system and method of assembly

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefits under 35 U.S.C 119(e) of U.S. Provisional Application Ser. No. 61/642,780, filed May 4, 2012, which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     Embodiments described herein relate to tanks which are modular and transportable for assembly on-site, such as for temporarily containing large volumes of fluids utilized during oil or gas well servicing operations, and, more particularly, to tank panels, connectors and methods of assembly. 
     BACKGROUND 
     Oil and gas servicing operations require fluid for a variety of reasons, most commonly during drilling and completions operations. The fluid may be used in drilling operations for lubricating the borehole, cleaning away cuttings, and maintaining control of the well by overcoming the reservoir pressure. In completion operations, fluid is generally used for stimulating the formation, such as by acidizing or fracturing, cleaning the well bore, and maintaining well control. In most cases the amount of fluid required is large and the fluid must be prepared and stored onsite during the operation. Onsite tanks may also be used to store fluids such as run-off water, diesel fuel, glycol, oils, waste products and the like. Upon completion of the drilling and completion operations however large volume tanks used to contain such fluids onsite may no longer be required. 
     In completion operations, the fluid used is a fracturing fluid which is typically a mixture of at least water and a proppant, such as sand. Tanks used to store the fracturing fluid, commonly referred to as frac tanks, are fluidly connected to a pump, such as by a hose or pipe, so as flow the fracturing fluid down the wellbore at sufficiently high pressures to fracture the formation. The proppant in the fracturing fluid enters the newly created void space and acts to prop the spaces open, permitting reservoir fluid to flow more freely to the wellbore. 
     One type of conventional frac tank is a rectangular shaped pre-assembled tank unit that is towed behind a truck as a tractor-trailer assembly. This type of conventional tank typically has a capacity of about 500 barrels. Thus, multiple tanks are needed onsite in situations where the fluid volume requirement is greater than 500 barrels, such as in completion operations for stimulating multiple zones in deep horizontal wells. 
     Another type of conventional frac tank consists of an assembly of multiple panels which are transported onsite for assembly of the tank thereat. The panels for the conventional multi-panel tanks are typically made of steel and are very heavy. Due to weight restrictions and the like, several truck-trailer units may be required to deliver the panels to the site. Further, the steel panels require an onerous assembly process as a result of many fasteners required to hold the tank panels together. 
     In the case of the conventional multi-panel tanks, where the surface or ground on which the tank is to be assembled is angled or is uneven and undulating, alignment and assembly of the panels may be problematic. 
     Clearly, there is a need for high volume, transportable fluid storage tanks that are light weight and easy to assemble, such as for temporary use onsite in the oil and gas industry. 
     SUMMARY 
     In embodiments disclosed herein, transportable, arcuate panels having complementary connectors can be assembled in the field without fasteners, such as pins or bolts. A female connector having a shaped groove extends along one end of the panel and a male connector having a shaped tongue extends along the other end of the panel. For assembly with like panels, the tongue on one panel is slid axially into the groove of the adjacent panel. The connectors lock together circumferentially while permitting vertical misalignment between the adjacent panels, such as on sloped or uneven ground. A limited rotation between complementary female and male connectors, allows the panels to engage even when the panels are not perfectly aligned during assembly and further permit embodiments of the tank having multiple radii. 
     In a broad aspect, a transportable tank system comprises: three or more arcuate panels, each panel having first and second opposing and parallel ends and having a bottom edge and a top edge extending therebetween; an elongate female connector having a shaped groove extending along the first end; and an elongate male connector having a shaped tongue formed along the second end. When the three or more arcuate panels are arranged in a perimeter on a surface with the first and second ends oriented substantially vertically therefrom, the shaped tongue of the male connector of each arcuate panels slidably engages within the shaped groove the panels adjacent thereto for circumferential locking therebetween. 
     In another broad aspect, a transportable, arcuate panel for use with like panels for constructing a tank for containing fluid therein, comprises: first and second opposing ends and a bottom edge and a top edge extending therebetween. At least an inner skin extends between the first and second ends. A core is structurally bonded to the inner skin. An elongate female connector having a shaped groove extends along the first end; and an elongate male connector having a shaped tongue extends along the second end. The shaped groove on the female connector and the shaped tongue of the male connector are adapted to engage between adjacent like panels so as to permit circumferential locking and axial engagement and disengagement therebetween. 
     In a broad method aspect, a method for construction of a tank uses three or more arcuate panels having first and second opposing ends and a bottom edge and a top edge extending therebetween. An elongate female connector having a shaped groove extends along the first end; and an elongate male connector having a shaped tongue extends along the second end. A first of the three or more panels is arranged on a surface, the opposing ends being substantially vertical thereto. A second of the three or more panels is lifted above and offset the first panel. A bottom of the shaped groove on the first end of the second panel is aligning above a top of the shaped tongue on the second end of the first panel. The second panel is lowered for axially engaging the shaped tongue within the shaped groove; and the steps are repeated for the remaining panels of the three or more panels for forming the tank perimeter. 
     In embodiments, the panels are FRP panels which are lightweight, strong and durable. In other embodiments, the panels could be made of steel or other suitable materials. The male and female connectors are typically extruded aluminum and are replaceably secured to ends of the panels so that the connectors can be replaced during use if worn or damaged. 
     Where the bottom of the tank perimeter does not engage the ground on which the perimeter is assembled, a liner can be placed within the perimeter and secured to the assembled panels using hook and loop fastener or clamps. The liner can then be replaced with each use or as necessary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a modular tank according to an embodiment described herein; 
         FIG. 2  is a perspective view of a lightweight composite panel used for assembly of the tank according to  FIG. 1 ; 
         FIG. 3  is a perspective view according to  FIG. 1 , a panel being inserted into a space between already-assembled panels for forming a tank perimeter; 
         FIG. 4  is a partial sectional view of a top of the panel of  FIG. 2 ; 
         FIG. 5  is a partial section view of a top of adjacent panels according to  FIG. 2 , assembled using an embodiment of connectors described herein; 
         FIG. 6  is a plan view according to  FIG. 5 ; 
         FIG. 7  is a detailed plan view according to  FIG. 5 ; 
         FIG. 8  is a sectional plan view according to  FIG. 5 ; 
         FIG. 9  is a perspective view of a panel according to  FIG. 2 , supported horizontally on a surface and having ropes installed on shackles for lifting the panel for assembly with like panels; 
         FIG. 10  is a perspective view of a shackle threaded into and used for lifting the panel according to  FIG. 9  and further illustrating threaded connections into reinforcement plates embedded in the panel, as shown in dotted lines; 
         FIG. 11  is a perspective view of ropes engaging between a crane (not shown) and shackles positioned about a center of gravity of the panel in stiffening ribs adjacent a top and bottom edge of the panel for four-point lifting on and off a truck bed or storage surface; 
         FIG. 12  is a perspective view of ropes engaging between a crane (not shown) and shackles positioned about a center of gravity of the panel on a top edge of the panel for two-point lifting for assembly, the panel being suspended substantially vertically therefrom; 
         FIGS. 13A-C  are plan views of a tongue of a male connector engaging a groove of a female connector forming a tongue-and-groove joint and more particularly; 
         FIG. 13A  illustrates the interconnected tongue and groove having a uniform gap therebetween when the connectors are not in tension 
         FIG. 13B  illustrates the interconnected tongue and groove having a non-uniform gap therebetween when the connectors are in tension, the tongue bottoming out in the groove as the connectors are placed in tension such as when the tank is filled with fluid; and 
         FIG. 13C  illustrates limited rotation about an arc radius, such as when the panels are assembled for forming a substantially cylindrical tank; 
         FIG. 14  is a perspective view illustrating a liner engaged within the tank using hook and loop fastener such as when there are gaps between a bottom edge of the tank and the ground surface on uneven ground; 
         FIGS. 15A and 15B  illustrate a stack of like panels according to  FIG. 2 , stacked for transport and storage, more particularly, 
         FIG. 15A  is a side view of the stack of panels showing cribbing positioned beneath the stack for supporting the stack; and 
         FIG. 15B  is a cross-sectional view along lines A-A illustrating neoprene positioned between the panels for protecting the stacked panels; 
         FIG. 16  is a partial perspective view of a first panel having a temporary male guide installed thereon and a second panel aligned for engagement of the groove with the male guide and tongue of the first panel; 
         FIG. 17  is a plan view of the first and second panels according to  FIG. 16  when assembled and prior to removal of the male guide installed thereon’ 
         FIGS. 18 to 26  are perspective views illustrating the method of interconnecting the male connector of one panel with the female connector of an adjacent panel, more particularly, 
         FIG. 18  illustrates aligning the groove of the female connector of a second panel over the temporary male guide and tongue of the first panel; 
         FIG. 19  illustrates the male guide entering the groove of the female connector; 
         FIG. 20  illustrates engagement of the male guide in the groove of the female connector; 
         FIGS. 21 to 26  illustrate axial engagement of the tongue of the male connector in the groove of the female connector as the second panel is lowered and slid downward relative to the first panel; 
         FIG. 27  is a perspective view of a temporary female guide installed on the groove of the female connector of an adjacent already-assembled panel as a last of the panels is aligned for insertion of the tongue of the male connector of the last panel into the temporary female guide and groove of the already-assembled, adjacent panel; 
         FIGS. 28A to 28C  illustrate the temporary female guide of  FIG. 27 , used for installing the last panel for forming the tank perimeter, more particularly, 
         FIG. 28A  is a front view of the female guide; 
         FIG. 28B  is a side view of the female guide; and 
         FIG. 28C  is a plan view of the female guide installed over the groove of a female connector, shown in dotted lines; 
         FIG. 29  is a perspective view of two assembled panels wherein the ground is sloped and there is vertical misalignment between the interconnected male and female connectors of the panels; 
         FIG. 30  is a perspective view of two assembled panels wherein the ground is clopped and there is vertical misalignment between the interconnected male and female connectors of the panels; and 
         FIG. 31  is an inside perspective view of a panel aligned vertically on a ground surface that is uneven, gaps being formed between a bottom edge of the panel and the surface. 
     
    
    
     DESCRIPTION 
     Embodiments of a transportable tank, system and methods of assembly, are disclosed herein. As shown in  FIGS. 1-3 , the transportable tank  10 , often referred to as a sectional knockdown tank, comprises three or more arcuate panels  12  which are interconnected at mating, parallel ends for forming a perimeter  14  of the tank  10  for containment of liquids F therein. The arcuate panels  12  are manufactured as fiber-reinforced plastic or polymer (FRP) panels and are relatively lightweight. When unassembled the panels  12  are compactly stackable on a surface S, such as on a truck bed for transport onsite or on another surface such as the ground for storage. Complementary, mating end connectors  16  are used for connecting the three or more panels  12  together for forming the tank  10 . The connectors  16  act to lock the three or more arcuate panels  12  circumferentially relative to one another, but permit a higher up and down tolerance for assembly relative to one another than in the prior art, such as when assembled on uneven ground. The connectors  16  allow the panels  12  to misalign vertically relative to adjacent panels  12 . 
     Embodiments described herein do not require bolts or pins field for assembly and provide a simplified assembly process when compared to the prior art. Composite FRP panels  12  for forming the tank  10  are lighter than conventional steel tank panels, making the embodiments easier and safer to maneuver and assemble. 
     Transportable Tank System 
     Panels 
     With reference to  FIG. 2 , each panel  12  of the three or more arcuate panels  12  for forming the tank&#39;s perimeter  14  has a first end  18 , a second end  20  and a top edge  22  and a bottom edge  24  extending therebetween. The first end  18  and the second end  20  are parallel to one another. While the particular arrangement of the top and bottom edges  22 , 24  is not critical, each panel  12  is generally rectangular if it could be rolled out flat. 
     In an embodiment, as shown in  FIG. 4 , each panel  12  is a composite FRP panel which comprises a core  26 , such as foam, and at least an inner skin  28  laminated and structurally bonded thereto. Assembled, the panels  12  are expected to support the hydrostatic loading of contained liquids F. Therefore the connectors  16 , at least the inner skin  28  and the core  26  act together to support the hoop stress and other resulting loading. Accordingly the inner skin  28  has suitable tensile strength to take up hoop stress when placed in tension, such as when the assembled tank  10  is filled with liquid F. The inner skin  28  comprises engineered layers of fibers and resins to achieve the required strength. 
     In an embodiment, the inner skin  28  is formed of glass reinforced fiber polymer (GFRP) laminated to the foam core  26 . The foam core  26  may further comprise GFRP shear webs laminated thereto. 
     In an embodiment, the arcuate panel  12  further comprises a protective outer skin  30 , the foam core  26  being sandwiched and structurally bonded between the inner and the outer skin  28 , 30 . The outer skin  30  is also a GFRP skin.  5 . Thus, the core comprises an insulating material. The panel  12 , so constructed, has a design thermal insulation value which negates the need for applying further insulation, such as spray foam, to the tank  10  after it is assembled. Insulation aids in preventing freezing of liquids stored therein. 
     As shown in  FIGS. 2-4 , the panel  12  further comprises an upper stiffening rib  32  formed circumferentially adjacent and below the top edge  22  of the panel  12  and a lower stiffening rib  34  formed circumferentially adjacent and above the bottom edge  24  of the panel  12 . The upper and lower stiffening ribs  32 , 34  add sufficiently to the tensile strength of the panel  12 , without a need for external steel bands such as found in the prior art to maintain structural integrity. 
     The stiffening ribs  32 , 34  aid to prevent buckling of the tank  10  during handling and under windy conditions when assembled and empty. Further, the stiffening ribs  32 , 34  protect the integrity of the panels  12 , such as when the panels  12  are stacked for storage or transport, thus improving the overall safety of the tank  10  and the longevity of each panel  12 , particularly about the bottom edge  24  of the tank  10  where leaking as a result of a loss of integrity is most likely to occur. 
     In embodiments, the upper and lower stiffening ribs  32 , 34  are formed of foam covered by a GFRP skin. 
     Having reference to  FIG. 8 , shaped panel ends  36  are formed at each of the first and second ends  18 , 20 . The panel ends  36  are an extension of the first and second ends  18 , 20  extending circumferentially outwardly in the same plane as the panel  12 . The shaped panel ends  36  form a base to which the connectors  16  are fastened. 
     In an embodiment, the shaped panel ends  36  are formed of a structural member, such as a hollow metal beam  36   b  having a generally rectangular cross-section, each end beam  36   b  having a smaller depth than a depth of the panel  12 . The panel ends  36  extend between the top and bottom edges  22 , 24  and are centered between the inner and outer skins  28 , 30 . 
     Connectors  16  straddle the panel ends  36  and are fastened thereto, such as with nuts and bolts  37 , the fastening being through the end beam  36   b . The inner and outer skins  28 , 30  of the panel  12  extend over the end beams  36   b . When assembled, the connectors  16  are substantially flush with the inner and outer skins  28 , 30 . The connectors  16  can be unfastened from the panel ends  36  and replaced if worn or damaged during use. 
     In an embodiment, shown in  FIGS. 7 and 8 , the end beams  36   b  are elongate, rectangular tubular members  36   b , such as rectangular, extruded aluminum tubulars, which are operatively connected to the foam core  26  along the first and second ends  18 , 20  and which are also covered with the GFRP skin  28 , 30 . The extruded aluminum tubular end beams  36   b  can be removed from between the skins  28 ,  30  and new tubular end beams  36   b  inserted therein for replacement if damaged during use. 
     As shown in  FIGS. 9 and 10 , each of the panels  12  further comprises reinforcements  38 , spaced along the edges  22 , 24  and in the upper and lower stiffening ribs  32 , 34  of each panel  12  and embedded therein as lifting engagement means or connection points to aid in handling of the panel  12 . The reinforcements can be small, stainless steel plates  40  embedded or formed internal to the panels  12 , and which have a fastener provided therein to permit connection of removable eye hooks or shackles  42  used for lifting the panels  12  on and off the truck bed, and for positioning and aligning the panels  12  for connection therebetween during assembly of the tank  10 . 
     In an embodiment, six reinforcement plates  40  are used, two spaced along the top edge  22  of the panel  12  and two in each of the top and bottom stiffening ribs  32 , 34  of the panel  12 . The reinforcement plates are structural and capable of holding greater than 5 times the weight of the panel  12 . 
     In embodiments, as shown in  FIG. 10 , the stainless steel plates  40  are internal to the panel  12  and are threaded to accept threaded shackles  42 . The plates  40  are positioned equidistant either side of the panel&#39;s center of gravity so as to balance the panel  12  when the shackles  42  are engaged and the panel  12  is lifted. 
     As shown in  FIG. 11 , during lifting on and off the truck, shackles  42  are threaded to the reinforcement plates  40  on the top and bottom stiffening ribs  32 , 34  and are engaged to permit a four-point lift, the panel  12  being in a generally horizontal position. As shown in  FIG. 12 , during installation, shackles  42  are threaded into the reinforcement plates  40  on the top edge  22  of the panel  12  and are engaged so that the panel  12  can be suspended substantially vertically, such as from ropes connected to a crane, for alignment with another of the panels  12  during assembly therewith. The panel  12  hangs vertically for parallel alignment of the elongate female connector of one panel with the elongate male connector of an adjacent panel. 
     Advantageously, while being lightweight as a result of the composite structure of the panels  12 , the panels  12  also comprise little if any exposed steel and therefore issues related to corrosion are largely absent. 
     Connectors 
     With reference to  FIGS. 2 and 5-8 , the connectors  16  further comprise an elongate female connector  44  which extends along the first end  18  of the panel  12  and an elongate, male connector  46  which extends along the second end  20  of the panel  12 . The female and male connectors  44 , 46  are complementary to permit interconnection with adjacent, like panels  12  for assembling the tank perimeter  14 . The male and female connectors  44 , 46 , when interconnected, form a dovetail-type or tongue-and-groove type joint  48  which locks circumferentially therebetween, but permits sliding axial engagement and disengagement of the male and female connectors  44 , 46  to allow assembly and further to permit an assembled panel  12  to misalign vertically with respect to adjacent panels  12 . Vertical misalignment permits adjacent panels  12  to remain vertical despite support on an uneven surface S. 
     In an embodiment, the elongate male connector  46  is a generally T-shaped tongue  50  having a neck portion  52  which extends outwardly from the panel end  36  and in the same plane as the panel  12  and a head portion  54  which extends generally perpendicular thereto. As shown in  FIG. 8  and  FIGS. 13A-13C , opposing ends  56  of the head portion  54  are curved inward toward the panel  12  and the panel end  36 . 
     The female connector  44  comprises a channel or groove  58  formed therealong between opposing and parallel fingers  58 F, 58 F. The groove  58  is complementary or corresponds in shape with the generally T-shaped tongue  50  for engagement or coupling therewith. When the tongue  50  is engaged within the groove  58 , the adjacent panels  12 , 12  are locked circumferentially as the curved opposing ends  56  of the head portion  54  cannot be pulled circumferentially out of the groove  58 . 
     As shown in  FIGS. 13A-13C , to prevent forcible removal from one another, and in particular the forcible spreading of the opposing finger  58 F, 58 F under circumferential loading to release of the tongue  50 , the complementary connectors  44 , 46  can have a configuration shaped to encourage a gripping engagement. 
     Each head portion  54  has a mushroom head shape forming angular wing portions  54 W, 54 W that face each other forming an inside dovetail groove and an outside dovetail groove. Opposing ends or wing portions  54 W, 54 W of the head portion  54  are angled inward toward a centerline of the panel  12 . The groove  58  has complementary wing portions  58 W, 58 W forming complementary inside and outside dovetail-shaped portions. When the head wing portions  54 W circumferentially pull on the groove wing portions  58 W, the fingers  58 F are driven inwardly, towards each other gripping the tongue  50  even more strongly. Thus, the curved opposing ends  56  of the head portion  54  cannot be pulled circumferentially out of the groove  58 . 
     Further, as shown in  FIGS. 13A-13C , a gap  60  is formed between the tongue  50  and the groove  58  when interconnected. When the panels  12  are not in tension ( FIG. 13A ), the gap is uniform therebetween, such as about 0.050 inches. When the panels are in tension ( FIG. 13B ), such as when the tank  10  is filled with fluid F, the gap  60  increases, such as to a maximum of about 0.106 inches except where the curved opposing ends  56  bottom out on the groove  58 . As shown in  FIG. 13C , during assembly, when the panels  12  are joined together to form a generally cylindrical containment, the interconnected female and male connectors  44 , 46  and gap  60  therebetween permit a limited rotation of the tongue  50  within the groove  58  allowing adjacent panels  12  to swing laterally within a constrained arc radius relative to one another. 
     The limited rotation between the female and male connectors  44 , 46  allows the panels  12  to engage even when the panels  12  are not perfectly aligned during assembly and further permit embodiments of the tank  10  having multiple radii. For example, fewer panels  12  result in a smaller diameter tank  10  while a larger number of panels  12  result in a larger diameter tank  10 . During assembly, the panels  12  may not be assembled in a perfect circle however when fluid fills the tank, the panels  12  are forced into a substantially perfect circle with the limited rotation at the interconnected female and male connectors  44 , 46 . 
     Best seen in  FIGS. 7 and 13A-13C , each of the female and male connectors  44 , 46  further comprise an elongate rectangular recess  62  extending from a top to a bottom therealong, opposing the tongue  50  or the groove  58 . The recess is bounded by spaced, opposing and parallel flanges  62 F, 62 F. The rectangular panel end  36  fits within the recess  62  between the two flanges  62 F, 62 F and the connectors  16  are fastened transversely therethrough, such as using nuts and bolts  37 , extending through one flange  62 F, through the end beam  36   b  and through the opposing flange  62 F, for secure connection to the panel ends  36 . Thus, the connectors  16  can be easily changed if the connectors  16  are damaged during use. 
     Generally the connectors  16  are extruded or other manufactured elongate shapes of unitary cross-section formed to incorporate the spaced flanges  62 F, 62 F and the respective female and male connector  44 , 46  components. In embodiments, the connectors  16  are made from extruded anodized aluminum which is light weight and will not corrode. 
     As noted above, the flanges  62 F, 62 F of the connectors  16 , when bolted to the panel ends  36 , are substantially flush with the inner and outer skins  28 , 30  of the panel  12 . 
     As one of skill will appreciate, while described herein in the context of use with FRP panels, embodiments of the female and male connectors  44 , 46  are also applicable for use with tanks  10  formed using panels constructed of other materials, such as steel. 
     Liner 
     Once assembled, the tank  10 , engaged with the surface S, typically the ground, about the entirety of the bottom edge  24  of the three or more panels  12  can be used to hold fluid F, the ground S acting as a floor of the tank  10 . 
     Where the panels  12  do not completely seat on the ground S however, a liner  70  can be used within the tank  10 . As with conventional steel tanks where a liner is used, conventional clamps may be used to retain the liner  70  in the tank  10 . While the tank  10  may be reused onsite, typically the liner  70  is replaced with each use. 
     In embodiments disclosed herein, as shown in  FIG. 14 , the liner  70  can be attached using an industrial, flexible, and reusable hook and loop material  72  which can be pre-attached to the tank panels  12  and to the liner  70  to permit safer, less time consuming attachment to the tank  10 . Typically, the liner  70  extends over the top edge of the tank panels  12 , such as about 2 to 3 feet. The hook and loop material  72  is attached to the outer skin  30  of the panel  12  below the top edge  22  of the panel  12  and to the side of the liner  70  adjacent thereto. 
     More robust attachments can include clamps (not shown) that sandwich the liner about the top edge  22  of the panel  12 . 
     Leak Monitoring 
     In embodiments, a leak detection and monitoring system, such as is known in the art, can be installed to monitor the tank integrity. 
     Transport and Assembly 
     Embodiments disclosed herein are assembled in the field, such as at a well site location. As shown in  FIG. 15A and 15B , sufficient arcuate panels  12  to form a tank  10  of the required volume are stacked on a truck bed  80 , such as on a standard 48′ flatbed truck. Due to the stability and lightweight panel design, the stacked panels  12  meet regulations for the maximum dimension and weight limitations for highway transport. 
     Additionally, cribbing  82  may be used between the truck bed  80  and the panels  12  to support the stacked panels  12 . Further, neoprene strips  84  may be positioned between the panels  12 , as the panels  12  are stacked, to avoid damage to the panels  12  during the transport. 
     Once onsite, having reference again to  FIGS. 9 and 12 , guide ropes  86  connected to a crane (not shown) are connected to the shackles  42  on the top edge  22  of each panel  12 . The panels  12  are then lifted by the crane, one at a time, for assembly. A first panel  12   f  is placed with the bottom edge  24  supported on the ground S, the opposing ends  18 , 20  being substantially vertical thereto. 
     As shown in  FIG. 16 , a second panel  12   s  is lifted above and offset the first panel  12   f , a bottom  90  of the shaped groove  58  of the female connector 44  of the second panel  12   s  being aligned with a top  92  of the male connector  46 , particularly the co-operating shaped tongue  50 , of the first panel  12   f . The second panel  12   s  is lowered to axially engage the tongue  50  and groove  58 . 
     In embodiments, as shown in  FIGS. 16-19 , a male guide  100  is temporarily connected to the top  92  of the male connector  46  of the first panel  12   f  for providing tolerance in two directions for alignment of the tongue  50  in the groove  58  of the adjacent second panel  12   s . The male guide  100  is generally a right rectangular, pyramidal-shaped member having an apex  102  directed upwardly from the panel  12  for insertion into the groove  58  of the female connector  44 . The male guide  100  has a flange  104  connected to a base  106  thereof for connection, such as to the neck portion  52  of the tongue  50 . 
     The work crew guides the suspended, bottom end  90  of the shaped groove  58  over the temporary male guide  100  as the second panel  12   s  is lowered thereon. 
     As shown in  FIGS. 20-26 , the second panel  12   s  is lowered until at least a portion of the lower edge  24  of the second panel  12   s  rests on the ground S. The male guide  100  can be removed from the first panel  12   f  when the female and male connectors  44 , 46  are engaged axially therealong. 
     To further aid axial alignment between the female and male connectors  44 , 46  during assembly, graphite spray may be used to lubricate the connectors  16 . 
     The above process is repeated until a last panel  121  of the three or more panels  12  is to be positioned for assembly. Having reference to  FIG. 27 , for assembly of the last panel  121 , a female guide  110  as well as the male guide  100  are used to aid in alignment and connection of the tongue  50  of the male connector  46  of the last panel  121  with the groove  58  of the female connector  44  of the adjacent, already assembled panel  12 . 
     In an embodiment, as shown in  FIGS. 27 and 28A-28C , the female guide  110  is a rectangular, funnel-shaped member  112  having an open side  114  contiguous with an open edge  116  of the shaped groove  58  of the female connector  44  to permit the male connector  46  and panel end  36  of the last panel  121  to slide therethrough as the tongue  50  is axially engaged in the groove  58 . 
     During assembly, the male guide  100  is temporarily attached to the top  92  of the tongue  50  of the already-assembled adjacent panel  12  to which the groove  58  of the female connector  44  of the last panel  121  will be attached. Further, the female guide  110  is temporarily connected to a top  118  of the groove  58  of the already-assembled adjacent panel  12  to which the tongue  50  of the male connector  46  of the last pane 1121  will be attached. An extension  117 , from a bottom  119  of the funnel-shaped member  112 , fits over the top  118  of the groove  58  for temporarily fastening the female guide  110  thereto. 
     As the last panel  121  is lowered into a space  120  ( FIG. 3 ) formed between the adjacent already-assembled panels  12 , the work crew align the groove  58  of the last panel  121  with the male guide  100  and the tongue  50  of the last panel  121  with the female guide  110  and the last panel  121  is lowered therein. Thereafter, both the male and the female guides  100 ,  110  can be removed. 
     Having reference to  FIGS. 29- 31 , once assembled, the panels  12  are axially movable relative to each other at the interconnected female and male connectors  44 , 46  for vertical misalignment therebetween. Slight ground anomalies and localized shifts after installation can raise one or more panels  12  relative to the others and automatically relieve pressure at the connectors  16 . Further, the system has a higher tolerance for assembly on uneven ground S than the prior art.  FIGS. 29 and 30  are illustrative of a worst-case scenario typically not seen in onsite installations, however it is clear that even in such conditions, assembly is possible using the connectors  16  taught herein. In an embodiment, it is recommended that the panels  12  be misaligned vertically up to about twelve inches over the span of a single panel  12 , typically about 37 feet long, while maintaining structural integrity on uneven ground. 
       FIG. 31  illustrates gaps  130  below the bottom edge  24  of the panel when positioned on a uneven or undulating ground surface S. In this case, the liner  70  would be required to maintain the fluid integrity of the tank  10   
     EXAMPLES 
     Table 1 is illustrative of some containment volumes and sizes of tanks assembled using panels according to embodiments disclosed herein, the panels being 10 feet in height and which have the listed length: 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Diameter 
                   
                 Circumference 
                 Number 
                 Panel 
                 Vol. 
                 Vol 
                 Vol 
                 Vol 
                 Wall 
               
               
                 (ft) 
                 π 
                 (ft) 
                 of panels 
                 length (ft) 
                 (ft 3 ) 
                 (m 3 ) 
                 Gal 
                 BBLS 
                 Area 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 173 
                 3.142 
                 543.5 
                 14 
                 38.8 
                 235062 
                 6656 
                 1758384 
                 41686 
                 5435 
               
               
                 120 
                 3.142 
                 377 
                 10 
                 37.7 
                 113097 
                 32.3 
                 846027 
                 20143 
                 3770 
               
               
                 83 
                 3.142 
                 260.8 
                 7 
                 37.25 
                 54106 
                 1532 
                 404742 
                 9637 
                 2608 
               
               
                   
               
            
           
         
       
     
     By way of example, for the 83 foot diameter, 10 foot high tank, having a 9637 barrel capacity (42 US gal/barrel), 7 panels are required for construction of the tank. Each arcuate panel is 10 feet in height and 37.25 feet in length. The composite panels each weight about 2,600 lbs per panel for a total weight of about 18,200 lbs, which is about ½ the weight of a conventional tank. The panels are of high strength and are corrosion and UV resistant. The panels have an E84 Class 1 fire rating. In a test panel, the total thickness of the panel between the stiffening ribs was about 3 inches. 
     High strength ¾″ diameter Grade 8 hex cap screws, washers and nuts were used, such as for attachment of the connectors to the panel ends. During transport, the panels are transportable on a standard 48 foot flatbed truck and would reach the volume limit for transport before the weight limit is exceeded. 
     During assembly, while vertical misalignment acts to accommodate sloping ground and the like, it is not recommended that the ground be sloped more than 12″ over a 37′ span.