Abstract:
There is provided an assembly for hoisting and transporting objects having support receptacles affixed to its outer surface and for moving the objects into a desired close alignment in a predetermined location. The assembly includes a mounting bracket configured to mechanically engage with a lifting end of a crane and at least a pair of lifting plates pivotally coupled to the mounting bracket. The lifting plates have opposed non-parallel sides that are angled to engage the support receptacles during lifting of the object and during transportation of the object. When the crane moves the object to its desired location, the crane operator may pivot the assembly to facilitate aligning the object. Upon completion of alignment, the object is put down, and the lifting plates disengage from the support receptacles by sliding out of the slots of the support receptacles.

Description:
BACKGROUND OF INVENTION 
     1. Technical Field 
     The technology relates to the field of fluid storage tanks, and more particularly to the fabrication of large above-ground liquid storage tanks that can be used to contain brine, for example, in connection with oil and gas production. 
     2. Description of the Related Art 
     There has been an increasing demand for energy world-wide. As a result, many different technologies are being used to meet this demand, and many are under development. Current technologies include, for example, traditional oil and gas production, secondary and enhanced oil and gas recovery techniques, coal production, use of solar panels and wind turbines to generate electricity, production of bio-fuels, use of ocean waves to generate electricity, and the use of nuclear reactors to generate electricity. It is known that in several parts of the world there are large subterranean reservoirs of natural gas, a desirable clean burning fuel, held in relatively impermeable geological formations. The relative impermeability of these formations presents a challenge to the production of these gas reserves because the gas is “tightly held” within the formations and cannot readily flow to a production well. 
     The technique of hydraulic fracturing of impermeable subterranean formations is being used to produce gas from relatively impermeable formations. Hydraulic fracturing, also known as “fracking” or “hydro-fracking,” is a technology that fractures underground formations creating flow pathways for release of the trapped natural gas and production of that gas for commercial purposes. 
     During gas production, “brine” containing injected chemicals is produced. This brine must be disposed of in an environmentally acceptable manner. In addition, the fracking operation typically consumes large amounts of water for hydraulic fracturing of the formations. So, before fracking there is a need for short term storage of the hydro-fracking fluid, and after fracking there is a need to store the brine produced. 
     Brine may be stored above ground in storage tanks for a period of time. There are several different tank designs. However, they should preferably meet criteria of durability and resistance to leaks under the conditions of use, and should be relatively easy and inexpensive to transport and construct. In the case of some tank designs, for example circular tanks, that are made up of a series of interlocked curved wall sections, there are significant challenges on site in handling the heavy metal sections. Each wall section is hoisted by a crane and guided into place next to other already installed wall sections. In order to get a closer alignment between the wall sections to facilitate joining wall sections together, workers must manipulate the wall section into position. The use of manpower in proximity to heavy wall sections, and man-handling the wall sections, poses an issue of potential risk to the worker. In addition, the use of additional manpower to guide the wall sections into position of closer alignment incurs labor costs. 
     SUMMARY OF PREFERRED EMBODIMENT 
     The following is a summary of some aspects and exemplary embodiments of the present technology, of which a more detailed explanation is provided under the Detailed Description section, here below. 
     An exemplary embodiment provides an assembly for hoisting sections of a tank wall into position during above ground tank construction. The tank wall sections are equipped with support receptacles that may be affixed temporarily or permanently to the curved outer surface of the tank wall section. The exemplary embodiment provides an assembly that includes a mounting bracket configured to mechanically engage with a lifting end of a crane. It also has lifting plates pivotally coupled to the mounting bracket. The lifting plates have opposed non-parallel sides that are configured to engage the support receptacles to thereby lift the tank wall section to which they are attached. The lifted tank wall section is transported for installation into the tank wall being constructed or repaired. To align the tank wall section more precisely and appropriately with an already-installed tank section to which it will be coupled, the assembly controllably pivots the lifting plates, about a pivot point, relative to the mounting bracket. This pivots the tank wall section into the desired position. Upon completion, the lifting plates disengage from the support receptacles by sliding away from the support receptacles, leaving the tank wall section in place. 
     Another exemplary embodiment provides a method of using an assembly for installing a tank wall section into a tank wall. The tank wall section has support receptacles attached to its outer surface. The pivoting assembly is attached to a lifting end of a crane. The exemplary method includes the steps of engaging a support receptacle with each of the lifting plates of the assembly, and lifting the tank wall section with the crane; moving the wall section to the desired location; and aligning the tank wall section by controllably pivoting the assembly by pivoting the lifting plates. Once the alignment is achieved, the lifting plates are disengaged from the support receptacles by sliding the lifting plates away from the support receptacles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments will be described in conjunction with the following drawings which are schematic, not to scale, and wherein like numerals denote like elements, and: 
         FIG. 1  is a schematic diagram showing a top view of a curved wall section of a storage tank under construction and indicating the alignment of the wall section relative to the installed wall section; 
         FIG. 2  is a schematic illustration of a side view portion of a wall of a storage tank showing the support receptacles used to the lift tank wall section into position; 
         FIG. 3  is a perspective view of an exemplary embodiment of a support receptacle to be lifted and placed in position by a pivoting assembly for hoisting objects to be lifted via attached support receptacles; 
         FIGS. 4A ,  4 B and  4 C are top views of an exemplary embodiment of the lifting assembly for hoisting support receptacles showing neutral and pivot positions; 
         FIGS. 5A ,  5 B and  5 C are perspective views of an exemplary embodiment of the lifting assembly for hoisting support receptacles of  FIGS. 4  A, B and C; and 
         FIG. 6  is a rear view of the exemplary embodiment of the pivoting assembly for hoisting support receptacles of  FIGS. 5A ,  5 B and  5 C. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is exemplary in nature facilitating an understanding of the inventions embodied in the appended patent claims. This detailed description is not intended to, and does not, limit the inventions to the described exemplary embodiments, or the application and uses of the exemplary embodiments. Furthermore, there is no intention to be bound by any express or implied theory presented in the preceding background, summary or the following detailed description. 
     Above ground tanks may contain thousands of gallons of liquid, such as fracking fluids and brine. These tanks generally have a metal circular outer wall with an inner liner enclosing the volume of liquid. The tank walls are subjected to radially outward directed forces from the pressure of the mass of liquid, which varies based on the height of liquid within the tank and the liquid&#39;s density. These walls are therefore strong and heavy and pose challenges when lifted into place at the tank site. Generally, the wall sections are fabricated off site and lifted by a hoist or crane onto a truck bed and transported to the tank site. At the site, they are individually lifted by a hoist or crane and guided into place with assistance of manual labor. Mechanization and automation of this process at the tank site would reduce the labor required and potentially improve safety. 
     Referring to the exemplary embodiments illustrated at  FIGS. 1  (a partial top view) and  2  (a partial side view), the tank wall  200  is constructed of a series of curved sections  202  that are joined together, end to end. As seen in  FIG. 2 , each curved section  202  of the tank wall  200 , in this example, has a structure that includes a curved (circular in this exemplary case for a round tank) top beam  206  and likewise curved bottom beam  204 , with vertical supports  208  at spaced intervals between the top and bottom beams. Spaces  210  between the supports  208  are metal plate, covered with thick plastic sheeting on the other side, for example, to contain the liquid inside the tank. 
     As seen in  FIG. 2 , according to an exemplary embodiment, trapezoidal support receptacles  102  are affixed on the outer surface of the tank wall section  202 . These support receptacles  102  are used to lift the tank wall section for transport at the site and for placing the tank wall section in position for constructing (or repairing) the tank wall. However, while these support receptacles facilitate lifting of the tank wall sections, close alignment of the heavy tank wall section to facilitate mechanical coupling to the end of the wall section to which it much be attached, still poses challenges, and requires manual labor. 
     The alignment issue is illustrated in  FIG. 1 , where it is desired to align a new tank wall section  202 ″ closely with end tank wall section  202 ″. To achieve this closeness and alignment, the gap  10  between the tank section ends has to be closed, and in addition, the tank section ends adjacent to each other should lie on common tangent line  12  to the tank wall surface at the point of connection of sections  202 ′ and  202 ″. 
     Exemplary embodiments, therefore, also provide a pivot capability: the assembly is able to pivot and the crane operator is thereby able to visually align the tank wall section on the assembly before setting it down in close alignment with the tank wall end to which it is intended to be attached. Without thus pivoting capability, the hoist carrying the tank wall section would have to be repositioned, perhaps several times, before the tank wall section is aligned with the adjacent section for attachement. 
     Exemplary embodiments provide a lifting assembly that has a fixed relation to the crane to which it is attached, but that can swivel under operator control to more precisely align the tank wall section with the adjacent already-installed the wall section, for ease of construction. This reduces or eliminates the need for manual labor manipulation of heavy tank wall sections, with all potential attendant risks, to facilitate installation. 
     An exemplary embodiment of a support receptacle is illustrated in  FIG. 3 . In this example, the support receptacle  102  is trapezoidal, having parallel upper and lower sides  106  and non-parallel or converging sides  104 . The ends of non-parallel sides  104  are folded to provide slots  108  that are sized to engage lifting plates of an assembly  100  for hoisting the support receptacles and any object to which they are attached, as explained in more detail below. Of course, support receptacles are not limited to trapezoidal shapes, but can include triangular shapes, and indeed, any shape that will allow the lifting plate of the assembly (1) to slidingly and securely engage slots of the support receptacle and prevent the support receptacle from falling off under gravity, and (2) to disengage by sliding out of the slots, when the tank wall section is set down in place aligned with the adjacent installed section of the tank wall. 
     Referring to  FIGS. 4-6 , an exemplary embodiment of an assembly for hoisting support receptacles is illustrated in top, perspective and rear perspective views, and in three different pivot positions: neutral, pivoting to the left and pivoting to the right. 
     The exemplary assembly  100  shown has a pair of lifting plates  120  that are each shaped to receive a support receptacle  102 . In this instance, the lifting plates  120  are trapezoidal, but may be any shape that has non-parallel converging sides that will engage the slots  108  of the support receptacles and thereby allow lifting of the support receptacles  102 . In the case of the non-limiting trapezoidal example illustrated, the angle β between the lower of the two parallel sides and the non-parallel side may be less than 90° or in the range from about 60° to about 85°. Since the lifting plates and the support plates in this exemplary embodiment have matched geometry, the angle β, is best seen in  FIG. 3 . 
     The assembly  100  has a mounting bracket structure  130  for engaging a hoist to lift the support receptacles. As seen in  FIG. 6 , the illustrated example of a mounting bracket structure  130  has a substantially rectangular shaped upper frame  140 . Upper frame  140  includes a surrounding frame  142  and an array of vertical supports  144 , and is supported on lower frame structure  150 . A pair of hooks  152 , configured to engage with structure on the crane (not shown), extends rearward (i.e. away from the lifting plates  120 ) from the lower frame structure. Of course, structure, other than hooks  152  may be used, depending upon the hoist structure that must be engaged for lifting the assembly  100 . The illustrated hooks  152  readily engage a coupling beam at the end of a Skycrane-type of quick connect that has a horizontal bar that fits within the hooks, and may then be secured to the hooks  152 . The hydraulic controls of the crane can be used to raise, tilt and lower the assembly. Of course, other kinds of crane-coupling attachments may also be used, and the pivoting assembly is not limited to the exemplary hooks illustrated as crane-coupling devices. 
     Referring to the examples of  FIGS. 4 and 5 , lifting plates  120  are each mounted to a plate support structure  160  that has a rectangular frame  162 , shown in this example as fabricated of tubular metal. The frame  162  has a pair of horizontally extending support beams  164 , joined by a pair of vertically extending support beams  166 . The lifting plates  120  are supported forward of the frame  162  and are attached to the frame  162  by couplers  168 . Each of the couplers  168  may be welded to the frame  162  at one end and to the rear of its respective lifting plate  120  at the other end. Of course, support structure other than a rectangular frame may be used as well. 
     The lifting plate support structure  160  and the mounting bracket structure  130  are mechanically coupled together to pivot with respect to each other. In the example illustrated, a first bracket  170  extends rearward from the upper frame horizontal support beam  164 , and a second bracket  170  (not shown in the views) extends rearward from the lower horizontal support beam. The brackets  170  have through holes that register, and that are sized and shaped to receive a pivot pin  176 . Third bracket  174  and fourth bracket (not visible in views), similar to the first and second brackets  170 , extend forward from the mounting bracket structure  130  to align with the first and second brackets such that through holes in the third bracket  174  and fourth brackets align with those of the first and second brackets  170 . Thus, a pivot pin may extend through all four holes since these register with each other. The lifting plate support structure  160  can therefore pivot relative to the mounting bracket structure  130  about the pivot pin  176 , which is the pivot point. 
     To facilitate the controlled pivoting of the lifting plate support structure  160  relative to the mounting bracket structure  130 , a control device (not shown) may be used to control an extendable and retractable pivot arm, such as for example, a hydraulic or pneumatic cylinder or a servomechanism  180  that can extend and retract, thereby pivoting the lifting plate support structure  160  relative to the mounting bracket structure  130  at the pivot point, where the pivot pin is located. As shown in  FIGS. 4B and 4C , the angular range of pivoting is through an angle α. The angle α is not critical, but in an exemplary embodiment is sufficiently large to facilitate placement of the tank wall section on the assembly in close alignment with an adjacent tank wall section. 
     A pair of lifting lugs  190  shown in  FIGS. 5A-C  may be used to hoist the assembly  100  for transportation, or handling, or to couple it to the cooperating mechanical structure of a crane or hoist for use in lifting support receptacles. 
     In general, the wall sections are fabricated off-site in a machine-shop environment, and are very heavy. They are hoisted with cranes and stacked onto vehicles, like flat bed trucks, to be hauled to the site where the tank is to be constructed. On site the tank sections are readily lifted from the flat bed by using the tank wall section hoisting assembly, of which embodiments are described above. The assembly is attached to the end of a crane and may be tilted such that the plates are in an orientation suitable to slide into the support receptacles of the tank wall section. Typically, the plates would lie flat on the flat bed, so the plates would be tilted to a substantially horizontal orientation. Once the lifting plates are in the support plate slots, the assembly is raised and the plates are tilted to substantially vertical orientation, thereby lifting and tilting the tank wall section to the vertical. The tank wall section is then safely transported to any desired location, such as to on-site storage or to be added to the tank wall under construction. 
     At the tank wall construction site, each wall section is hoisted by a crane and guided into place next to other already installed wall sections. In order to join wall sections together it is necessary to get alignment between the wall sections and overlap of the wall edges. The tank wall section is manipulated at the end of a crane, for example, a Skycrane, so that when the tank wall section is in position, the operator pivots the assembly to bring the tank wall section into closer alignment with the end of the tank wall to which it should be coupled. Once satisfied that the tank wall section is sufficiently closely aligned for ready coupling to the tank wall, the operator sets the tank wall section down, and uses the crane end to move the assembly downward, thereby sliding the lifting plates out of the slots of the support receptacles. The operator can then repeat the process for the next tank wall section to be moved and aligned. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description section, it should be appreciated that many variations exist. It should also be appreciated that the exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the claimed inventions in any way. Rather, the foregoing detailed description provides a convenient road map for those of ordinary skill in the art to implement exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements described herein without departing from the scope of the patent claims listed below, including the legal equivalents of these patent claims.