BACKGROUND OF THE INVENTION 
   Large storage tanks are well known. Warping problems arise when transporting, positioning and welding plates. Building tanks from the ground up requires cranes and high scaffolds for workmen and welders. 
   Needs exist for new methods and apparatus for building large storage tanks. 
   SUMMARY OF THE INVENTION 
   In the workshop plates are produced, with great accuracy, in pieces as big as possible for transportation. 
   Transverse welds are made to elongate floor plates. The floor plates are arranged side by side and the circular peripheries cut, all at the workshop. The tank base is prepared by clearing, excavating and compacting soil. Annular forms are constructed and a reinforced concrete base and radial lifter support pads are poured. The forms are removed and layers of sand and river gravel are compacted within the annular concrete base. 
   On the site the floor plates are assembled and welded along longitudinal side edges as the bottom. The floor is used as a base for welding peripheral templates, on which the shell rings are assembled and welded. Pre-curved plates for forming the top shell ring are placed on the templates and are welded together along vertical seams. 
   The roof is assembled and welded. Details are in co-pending patent application Ser. No. 10/956,351, which is incorporated herein by reference in its entirety. 
   The roof is welded to the upper circular edge of the top shell ring. 
   The whole top ring and roof is lifted with hydraulic jacks on lifting pillars, sufficiently high to install the pre-curved plates for forming the next shell ring on the templates. Vertical seams of the second shell ring are welded. Temporary spacer guides are spot welded inside the second ring. The top shell ring is moved down to fit in the guides and on the spacers attached to the second rings. The upper edge of the second ring is welded to the lower edge of the first ring. The process is then repeated. 
   The last or bottom shell ring is assembled and vertically welded, then is welded to the next above ring. Finally the bottom ring is welded to the floor. 
   A concrete base ring surrounds compacted soil, sand and river gravel layers. A floor is built on top of the concrete ring. 
   Lifting nuts made of weldable steel are welded temporarily to flat floor and roof plates. That makes it possible to lift, move or position the plates whether they are thick, thin or irregular. The plates may be lifted in many points with a yoke and chains connected to bolts in the lifting nuts. 
   An open transport support is constructed as a beam platform. Three double pillars are attached to the beams to vertically hold and transport the pre-curved plates that conform the shell rings. The plates are maintained in a vertical position as they go into the tank from the time that they are rolled. That maintains the accuracy of the curvature, and is safer. 
   A special yoke with a turntable is used to move or position the curved shell plates vertically as they go into the tank. The yoke has a lifting ring in the top center, to be lifted with a crane. In the bottom center of the yoke a turntable has a base to be taken with a forklift. Both ends of the yoke have slots to fit cleats that are temporarily welded to the interior of a curved plate. To be stable and vertical, the center line that connects the two joining points must cross over the vertical center of gravity of the curved plate. 
   To make the tank floor as flat as possible, only longitudinal welding is carried out on site. 
   The bottom of the tank is used as a template by means of a series of special template devices temporarily welded along the perimeter about every twenty inches. 
   To avoid internal tension and deformation, the vertical welding that forms each steel ring must be made when the ring is stationary, independent from the rest of the tank. In that way the reduction of the perimeter produced by the welding will not affect the rest of the shell rings or itself. 
   To assemble one shell ring to another, special alignment and spacer devices are used to obtain perfect assembly between the upper and lower shell rings when they join. When an upper shell ring is lowered, it is centered to the correct alignment with and to the correct gap above the lower ring. 
   The lifting pillars are mechanical jacks driven by hydraulic cylinders. Each structure is formed by two channel beams joined opposite by two plates. In both channel beams, one flange is serrated. 
   In its lower part is has a chair-type base to settle the pillar on the foundation bolts inserted in the pads formed on the concrete base. 
   A sliding device moving in the serrated side lifts the assembled tank rings. The sliding device has an upper part and a lower part, which are joined by a double-action cylinder. Each part has two catches which push toward each other by springs. The catches allow only upward movement. When the partially assembled tank needs to be raised, the hydraulic cylinder pushes it upward, the lower part locks it in place, and the catches prevent the tank from moving downward. The upper part of the tank can then move freely upward. When the hydraulic cylinder is pulled, the upper part of the sliding device cannot descend, and the lower part can move up freely. If the tank needs to be lowered, the hydraulic cylinder must be elongated and the upper catches are opened. When the hydraulic cylinder closes, the tank descends. That is followed sequentially by moving the lower and upper parts downward in repeated steps. 
   Three coordinated independent hydraulic systems drive the lifting pillars. The numbers of pillars must be a multiple of three, operated simultaneously by a common command. The system shares the load between all the lifting pillars and attains a three-point stability of the lifted tank. 
   A storage tank construction starts with providing a prepared base. A tank floor is built on the prepared base. Templates are mounted peripherally around the tank floor. Pre-curved plates are placed on the templates. Welding together vertical longitudinal ends of the plates complete a first cylindrical ring shell. A roof is built and welded atop the first ring. Lifters around the first cylindrical ring shell raise the first cylindrical ring shell and hold the first cylindrical ring shell in an upward position. Placing the next level of pre-curved plates on the templates and vertically welding ends of the pre-curved plates together forms a second cylindrical ring shell spaced beneath the first cylindrical ring shell. Lowering the first cylindrical ring shell near with the second cylindrical ring shell is followed by circumferentially welding lower edges of the first ring shell and upper edges of the second ring shell together. Engaging the second ring shell with the lifters and raising the second ring shell and the first ring shell provides room for constructing a lower ring. Similarly positioning pre-curved plates of sequential ring shells on the templates and welding longitudinal ends of the pre-curved plates together forms sequential ring shells. Lowering above preassembled cylindrical ring shells close to a lower ring shell, welding an upper edge of the lower ring shell circumferentially to a lower edge of the above ring shell, engaging the lower ring shell and raising the lower ring shell and the above ring shells builds the tank. Removing the templates, positioning bottom pre-curved plates in contact with the floor is followed by vertically welding the bottom pre-curved plates end-to-end and forming a bottom cylindrical ring shell. Lowering the above assembled cylindrical ring shells so that a lower edge of the lowermost above ring shell is near an upper edge of the bottom ring shell makes possible the welding the adjacent lower and upper edges circumferentially. Welding a lower edge of the bottom ring shell to the floor completes the storage tank. 
   The floor is built by placing elongated floor plates laterally adjacent each other on the prepared base and welding longitudinal edges of the plates together. 
   The templates are radially oriented plural L-shaped plates welded circumferentially around the floor for supporting the pre-curved plates vertically above the floor. 
   The L-shaped plates have exterior vertical members. The pre-curved plates are placed inside the vertical members. 
   Lower portions of the plates are locked against the vertical members with locking levers hinged on the members. 
   Lifting cleats are temporarily welded to insides of the vertical plates. The cleats have downward openings. Recesses in ends of a lifting yoke beam engage the vertical openings of the cleats. A center of the beam is raised with a lifting device. 
   The lifting device is a crane or preferably a liftable turntable mounted on a forklift. 
   External cleats are welded to the plates in a ring and the lifters engage the external cleats. 
   The number of equally spaced lifters is divisible by three. 
   A roof is supported on and is welded to an upper edge of a first uppermost cylindrical ring shell after the first cylindrical ring shell is completed and before the first cylindrical ring shell is lifted. 
   The roof may be a dome roof. 
   Preferably the roof is a conical roof. 
   To construct the conical roof, support tables are placed inside the first ring. Elongated plates are placed on the support tables and extend over the ring. Welding longitudinal edges of elongated plates leaves an open sector having radial edges in the flat plate. Raising the center of the flat plate closes the sector by abutting the radial edges of the sector. The juxtaposed radial edges are welded together and peripheral parts of the roof are welded to the upper edge of the first ring. 
   Initially spot welding the templates at intervals across the laterally welded elongated plates before lifting the center of the roof and fully welding the radial beams to the cylindrical roof after lifting the center of the roof strengthens the roof. 
   The radial beams terminate at uniform distances spaced from the center of the roof. Welding a compression ring to inner ends of the beams adds strength. Welding a lower surface of the roof to an upper edge of the first cylindrical ring shell completes the roof before the first cylindrical ring shell is lifted. 
   Pre-curved plates of increasing thickness form the sequentially lower cylindrical ring shells. 
   Lateral shims are provided between vertical members of the templates and the pre-curved plates when forming the first cylindrical ring shell. Shims of reduced thickness are provided when forming subsequent cylindrical ring shells with plates of increased thickness. 
   The forklift remains within the tank structure as each cylindrical ring shell is completed and lifted. The forklift exits the structure before pulling a last end of a last pre-curved plate of the bottom cylindrical ring shell into position to complete the bottom ring shell. 
   Pre-curved pre-formed plates are placed on a support between plural pairs of columns. Lifting the loaded support onto a truck trailer, delivering pre-formed plates on the support and truck trailer and off-loading the loaded support at the site preserves and protects the plate curvatures. Loading is in an order reversed from that in which the pre-formed pre-curved plates are to be used in the first and subsequent rings. 
   A reinforced concrete ring base has anchor pads for the lifters. Compacted soil is overlayed by compacted sand and river gravel layers within the concrete ring base. The tank floor elongated plates are placed on the top of the river gravel, sand and compacted soil layers before welding longitudinal edges of the plates, completing the tank floor. 
   The lifters have climbing sliding members with hydraulic rams therebetween. Teeth extend from the members for locking with a stepped beam extending upward within the lifters. 
   Vertically rolled horizontally curved vertical plates are placed in alignment on a support base. Holding the plates on the support base between pairs of columns, clamping tops of the pairs together, and urging the plates from first columns in the pairs toward second columns in the pairs rigidifies the plates and protects their curvature. Lifting the support base onto a truck trailer, transporting the trailer and the support base with the plates to a tank construction site, lifting the support base from the trailer and placing the support base near the tank construction site maintains plate curvatures. The plates are lifted individually from the support base and placed into position above the tank floor. 
   Vertical templates having L-shaped tops with legs extending upward along outer surfaces of the pre-curved plates. Clamps have first ends pivoted on sides of the templates remote from the legs. Sloped second free ends of the clamps are placed against inner surfaces of the pre-curved plates. Wedging the pre-curved plates in place against the legs of the templates occurs by downward blows on the clamps. Welding vertical seams between adjacent ends of the panels forms a ring of panels. After welding tops of the panels to bases of the next above structure, the clamps are released by upward blows on the clamps. 
   Spot welding horizontal bridges over the vertical ends of the panels and welding vertical supports on the bridges and on one of the plates before welding the vertical seams maintains ring size. 
   Laminated guide spacers are spot welded near an edge area of one of the ring of panels, the guide spacers having straight inward vertical edges for spot welding to surfaces of one of the rings and sloping surfaces for guiding the other ring. Spacers extend between the sloping surfaces and the straight edges for spacing the horizontal edges of the adjacent rings of panels during welding of the edges together. 
   The building of the tank floor further includes forming elongated floor panels, laterally, assembling the longitudinal floor panels and forming a circular floor edge on the floor panels, welding lifting nuts to the elongated panels, welding clevises to upper ends of threaded connectors, engaging the lifting nuts with the welded connectors and lifting the clevises on the threaded connectors with chains, a yoke and a crane, placing the elongated panels on the prepared base, welding longitudinal side edges of the elongated plates together, and removing the lifting nuts. 
   Preferred lifters have back-to-back channel beams separated by welded plates. Opposite flanges are shaped with triangular edges with flat upper surfaces. Climber frames have upper and lower gripper members. Each member partially surrounds the opposite shaped flanges. Oppositely inwardly urged detents engage the flat upper surfaces and override the sloped triangular edges. A double-acting cylinder and piston connected between the upper and lower gripper members successively extends and withdraws the piston and thereby sequentially raises the upper and lower gripper members. 
   These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevation of a tank constructed according to the present invention. 
       FIG. 2  is a plan view showing construction of the floor. 
       FIG. 3  shows lifting nuts connected to floor panels. 
       FIG. 4  is a partial cross-section showing guide spacers used in assembly of the curved side panels prior to welding. 
       FIG. 5  shows assembly of an upper thinner curved plate to a lower thicker curved plate using especially configured guide spacers and locators spot welded to the lower plate. 
       FIG. 6  is a plan view detail showing the upper plate partially in cross-section mounted on one guide spacer. 
       FIG. 7  is a side elevational view of curved tank construction plates mounted on a transportable plate support. 
       FIG. 8  is a plan view of the support and curved plates. 
       FIG. 9  is an elevational view of a curved plate supported on a turntable yoke which is raised, moved and lowered by a forklift. 
       FIG. 10  is a plan view of a forklift yoke showing the lifting arms and turntable. 
       FIG. 11  is a detail of an inner lifting cleat being engaged by one end of the forklift yoke lifting arm shown in top view detail. 
       FIG. 12  is a side view detail showing engagement of an interior plate-lifting cleat by an end of the forklift yoke arm. 
       FIG. 13  is a side elevational view of one of many templates which are welded in radial directions near a periphery of the floor, and showing a clamping arm engaging a plate shown in cross-section and urging the plate against an outward stop on the template. 
       FIG. 14  is a plan view of the radial clamp lever hinged with a bolt to the template. 
       FIG. 15  is a front elevational view of a tank assembly lifting jack. 
       FIG. 16  is a top plan view of the lifting jack, showing the back-to-back channel beam or hollow I-beam construction of the vertical member and the spring-loaded detents on the upper climber, which is also shown partially in cross-section. 
       FIG. 17  is a side elevation of an externally mounted cleat on a curved plate of a tank, which is shown in cross-section. A top of a climbing member shown in cross-section engages a bottom of the cleat. 
       FIG. 18  is a side elevation of the lifter showing the hollow I-beam anchored at its base to the annular foundation pad extending from the base of the tank. A hydraulic cylinder alternatively pushes the upper plate upward and pulls the lower plate upward to raise the ring and the partially assembled tank in preparation for inserting additional curved plates to be vertically welded for forming a lower ring. 
       FIG. 19  shows a support and pre-curved plates mounted on a heavy duty truck trailer. 
       FIG. 20  shows templates radially attached to peripheral areas of a floor and a lifter base pad integrally formed with the cement base. 
       FIG. 21  shows a forklift truck with a yoke on a turntable positioning a pre-curved plate on the templates. 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is an elevation of a tank constructed according to the present invention. Tank  1  is built so that all the construction and welding occurs near the ground level  2 . First the upper ring  5  of curved plates is assembled on templates on the base, then the plates are welded vertically  3 . A triangular roof  7  is assembled on and welded to the upper edge  9  of the upper ring  5 . Next, the upper ring  5  is lifted by multiple lifters to provide sufficient clearance to insert curved plates  11 , which form the next lower ring  15  by vertically welding  13  end edges of plates  11 . The upper edge  17  of ring  15  is then welded to the lower edge  19  of ring  5 . External lifters are attached to external cleats on the outer surface of ring  15 . The lifters lift ring  15 , ring  5  and roof  7  to make room for placing plates  21  beneath ring  15 . When the plates  21  are in place and clamped against the templates, vertical seams  23  between the plates are welded, and ring  25  is formed. The upper edge  27  of ring  25  is then welded to the lower edge  29  of ring  15 . External cleats are welded to outer surfaces of ring  25  at spaced locations, and lifters engage the cleats to lift ring  25 , ring  15 , ring  5  and roof  7  sufficiently high to allow installation of plates  31 . Plates  31  are placed in position on templates or on the floor against external guides. When all of the plates  31  are assembled, vertical seams  33  are welded, forming the bottom ring  35 . Then the above rings  25 ,  15 ,  5  and roof  9  are lowered until the lower edge  39  of ring  25  is positioned just above the upper edge  37  of ring  35 . Then the edges  37  and  39  are welded, followed by welding lower edge  38  of ring  35  to floor  2 , completing the overall construction of the tank body. 
     FIG. 2  is a plan view showing construction of the floor. As shown in  FIG. 2 , a base  60  is made up of multiple elongated plates  61 . Some of the plates have transverse seams  63  welded between sections  64  and  65  prior to placement on the base. 
   Elongated panels  61  are welded transversely  63  off site and are assembled, held together and peripherally cut  67  off site. The panels  61  are then transported to the site and moved to the prepared base, where they are reassembled and welded along longitudinal seams  69 . The welding along longitudinal seams  69  is the only welding that takes place in the floor on the site. That prevents wrinkling and grooving of the welded plates at intersections of the welds  63  and  69 , which would occur if all of the welds were performed on site. 
     FIG. 3  shows lifting nuts connected to floor panels. 
   Because the plates  61  are thin and flexible, they are lifted and positioned in place with lifting nuts  71 , which are spot welded  73  to the tops  72  of the plates  61 . Threaded connectors  75 , in this case all threads, are welded  76  to loops or bails  77 , which are attached to chains  79 . The all threads or bolts  75  are engaged with the lifting nuts  71  and lifted with chain  79  uniformly across the plates  61  to prevent bending or warping of the plates while lifting the plates into position for assembly as the floor  60  on site on the prepared base. After the longitudinal welds  69  are completed, the spot welds  73  are ground off and the lifting nuts  71  are removed from the upper surfaces  72  of plates  61 . 
     FIG. 4  is a partial cross-section showing assembly of the curved side panels prior to welding. 
   As shown in  FIG. 4 , spacer and guides  41  are spot welded  43  at numerous positions along the internal wall  22  of ring  25 . The spacers have projections  45  which fit between edges  27  and  29  of rings  25  and  15 , and have sloped guiding surfaces  47  which guide the upper rings as they are lowered. Internal wall  49  of the guide and spacer  41  correctly position the internal wall  12  of the ring  15  to properly align ring  15  with ring  25 . 
   The proper spacing between edges  27  and  29  is maintained by the projections  45  from the guides and positioners  41 . External welds are applied between the spaced edges  27  and  29 , and projections  45  are consumed in the welding. Then the guides  41  are knocked off with hammer blows and any debris between the edges  27  and  29  is ground away, and the internal welds between the edges  27  and  29  are made. 
     FIG. 5  shows assembly of an upper thinner curved plate to a lower thicker curved plate using especially configured guide spacers spot welded to the lower ring. As shown in  FIG. 5 , guide spacer  51  is spot welded  53  to the interior  32  of bottom ring  35 . Spacers  55  extend between the lower edge  39  of upper plate  25  and the upper edge  37  of the bottom plate  35 . Because the bottom plate  35  is thicker than the upper plate  25 , interior surface  59  of the guide is spaced outward from the interior surface  58  of the guide  51 , which lies along the interior surface  32  of ring  35 . The outward positioning of guide surface  59  ensures that the outer surfaces  24  and  34  of rings  25  and  35  are maintained in a straight line. The upper sloping surface  57  assures the proper centering of the upward assembly as it is lowered into position adjacent the bottom ring. 
     FIG. 6  is a plan view showing the upper ring partially in cross-section mounted on one guide spacer.  FIG. 6  shows a top view of the structure shown in  FIG. 4 , with the upper ring  15  shown in cross-section. The guide spacers  41  may be made of thin laminated sheets. 
     FIG. 7  is a side elevational view of curved tank construction plates mounted on a transportable plate support.  FIG. 8  is a plan view of the support and curved plates.  FIGS. 7 and 8  show supports  80  for transporting the tank-building curved plates  11 ,  21 ,  31  from off site vertical rolling equipment to the tank-erecting site. Support  80  has a base  81  made of welded side and end channel beams  82 ,  84  and cross members  83 . Lifting tubes  85  are welded between side beams  82 . Double columns  87  extend upward from the base for holding the pre-curved plates  11 ,  21 ,  31  rigidly in a vertical position while transporting the plates from the off site rolling machinery to the erection site. The double columns have outer members  91  and inner members  93 , and the pre-curved plates are held between the outer and inner members. Caps  95  hold upper ends of the columns  91  and  93  together. Lower ends of the columns are welded to the side beams  82 . Bolts  97  with flat ends  96  are tightened to secure the plates in place. Collars  101  are connected to cross tubes  85 , and lifting cables  103  have lower ends looped around the cross tubes  85  outside of the collars. Upper ends of cables  103  are connected to holes  104  at ends of yoke  105 . The center of the yoke has a lifting opening  107  reinforced with gussets  109 . In use, the support  80  is placed near the vertical rolling machinery. Plates are transferred directly from the vertical rolling machinery to the support and are placed between the columns  91  and  93 . When the support is filled to capacity with the plates, caps  95  are positioned over upper ends of the supports, and bolts  97  are turned inward to hold the plates in fixed position. Cables  103  are then connected to the lifting tubes  85  outside of the collars  101 , and the support  80  is raised by a crane and placed on a flat bed trailer. The trailer is hauled to the site, the lifting yoke  105  and cables  103  are again attached to the lifting tubes  85  outside of the collars  101 , and a crane lifts and deposits the support  80  close to the prepared tank building site. The cables  103  and yoke  105  are removed. Caps  95  are removed and bolts  97  are loosened. 
     FIG. 9  is an elevational view of a curved plate supported on a yoke which is raised, moved and lowered by a forklift.  FIG. 10  is a plan view of a forklift yoke showing the lifting arms and turntable.  FIG. 11  is a detail of an inner lifting cleat being engaged by one end of the forklift yoke lifting arm shown in top view detail.  FIG. 12  is a side view detail showing engagement of an interior plate-lifting cleat by an end of the forklift yoke arm. 
   As shown in  FIGS. 9-12 , interior plate-lifting cleats  111  are spot welded  113  to interior surfaces  112  of the innermost pre-curved plate  110  of the nested pre-curved plates on the support. Yoke  115  on a forklift has end depressions  116 , which engage the interior lifting cleats  111 . Forks of a forklift are placed through openings in base  117  of turntable  119  at the center of the yoke  115 . The forklift lifts the innermost plate clear of the inner vertical columns  93  and carries the innermost plate to an appropriate position on templates assembled around the peripheral area of the floor. The forklift lowers the plate into a predetermined position on the templates, and clamps on the templates are raised to clamp the pre-curved plate  110  into position on the templates. Lowering the forklift releases the depressions  116  in ends of the yoke from the interior lifting cleats  111 , and the forklift returns to the support  80  for lifting the next innermost shell  110 , to which interior lifting cleats  111  have been welded. The forklift completes the carrying of a number of pre-curved plates  110  into place on the templates until the ring is complete. Welding vertical edges  3  of the plates completes one of the rings. 
   In all but the final bottom ring, the forklift remains within the ring until the ring and above rings and roof are lifted by the lifters. The bottom ring is assembled just as the other rings are assembled, with the exception that the final plate of the bottom ring is carried into position by the forklift driving within the structure. One vertical edge of the final plate is aligned with the next adjacent vertical edge of a plate which is already in position, and the forklift continues to move the pre-curved plate outward until a gap is left between the other end of the final pre-curved plate and the end of the plate adjacent the other end. The forklift then lowers the plate onto the templates and exits from the floor of the tank through the gap. Pulling outward on the end of the last plate from outside the tank places the last plate into the last ring. The turntable under the lifting yoke enables the disengaged yoke to be aligned with the forklift as it drives outward through the gap. 
   Before placing the plates in position for forming the bottom ring, the templates may be removed and replaced with alignment blocks. The bottom plates may be placed directly on the floor. 
     FIG. 13  is a side elevational view of one of many templates which are welded in radial directions near a periphery of the floor. A clamping arm engages a plate shown in cross-section and urges the plate against an outward stop on the template.  FIG. 14  is a plan view of the radial clamp lever hinged with a bolt to the template. 
     FIGS. 13 and 14  show one of the many templates and clamps which are aligned radially. The templates  121  are thin vertical plates. Each has a horizontal surface  123  which supports the plates, and an outward stop  125  which prevents excessive outward movement of the plate. The stop  125  is a grooved shim in a preferred embodiment. A clamp  127  is an arm which is pivoted by a bolt  129  at one end. The arm has a sloped outer surface  128  which bears against the inner surface  112  of the plate. A blow on the top  126  of the clamp secures the plate in position. When it is time to release the clamp, a blow on the under surface  124  of the arm releases the clamp, which is rotated counterclockwise, as shown in  FIG. 13 , to release the completed ring for raising. 
     FIG. 15  is a front elevational view of a tank assembly lifting jack. 
     FIG. 16  is an elevational view of the lifting jack showing the back-to-back channel iron or hollow I-beam construction of the vertical member and the spring-loaded detents on the upper climber, which is also shown partially in cross-section. 
   Lifter  130  has a column or pillar  139  with a base plate  132  which is connected to an annular concrete base  135 . Bolts  133  secured in the cement base  135  are engaged by nuts  137  to hold the pillar firmly in place. 
   As shown in  FIGS. 15 and 16 , the column  139  is formed of first and second back-to-back channel beams  141  and  143  having opposite flanges  145  and  146  at one end, and opposite flanges  147  and  149  at the opposite end. Flanges  147  and  149  have serrated edges  150  with upward and outward sloping triangular surfaces  151 , and flat horizontal surfaces  153 . Cross members  155  and  157  are welded between the opposite channel beams  141  and  143 . 
   A climber frame  160  has upper and lower members  161  and  163 . Each of the climber members has detents  165  urged inward by springs  167  to grip the flat surfaces  153  of the serrated flanges  150 . A double-acting hydraulic actuator ram  170  is connected between the upper and lower climber members  161  and  163 . As the double-acting hydraulic cylinder is extended, the upper member  161  is pushed upward, compressing springs by moving the grippers  165  outward until the next horizontal surface  153  is reached, whereupon the grippers are moved inward by springs  167  to engage the flat surfaces  153 . The next operation of the ram is a pulling operation, which draws the lower climber member  163  upward in a similar operation of the gripper members  165  on the lower climbing member  163 . 
   Lifters  139  are always arranged in three so that there are three, six, nine, twelve . . . twenty-one or more lifting pillar positioned on pads around the tank base. 
     FIG. 17  is a side elevation of an externally mounted cleat on a curved plate of a tank, which is shown in cross-section. A relatively thick climbing member which engages a bottom cleat is also shown in cross-section.  FIG. 17  shows an external surface cleat  180  having a base edge  181  welded  183  to an outer surface  184  of a tank construction ring  186 . 
     FIG. 18  is a side elevation of the lifter showing the hollow I-beam anchored at its base to the annular foundation pad of the tank, and showing a hydraulic cylinder for alternatively pushing the upper plate upward and pulling the lower plate upward to raise the next-above ring and the tank in preparation for inserting additional curved plates to be welded under the above welded ring. 
   As shown in  FIG. 18 , ring  186  has been partially lifted by the lifters  160 . External lifting cleat  180  is engaged by the upper lifter  161 , which is positioned near the tank ring  186 . 
     FIG. 19  shows a support and pre-curved plates mounted on a heavy duty truck trailer. 
     FIG. 19  shows a truck trailer  180  on which support  80  is mounted for holding the pre-curved tank plates  11 ,  21 ,  31  between the vertical columns  87 . The outer columns  91  and the inner columns  93 , which are connected to the support  80 , are also shown in  FIG. 19 . 
     FIG. 20  shows templates radially attached to peripheral areas of a floor and a lifter base pad integrally formed with the cement base. 
     FIG. 20  shows an annular concrete base  190  which has been prepared with integrally extended lifter pads  191  at several places around the periphery of the annular concrete base  190 . The lifter pads  191  occur in at least three places or in multiples of three places around the concrete base. A base plate  132  is attached to each pad, and bolts  133  are embedded in each pad. Floor  60  is constructed by assembling pre-cut elongated plates  61  on the annular base and pre-compacted soil and compacted sand and river stone or asphalt layers within the base, and laterally welding  69  the plates  61 . Templates  121  are welded to a peripheral area of the floor  60  at intervals of about 20 inches. A gap  195  between adjacent templates is left so that a forklift truck, which carries the pre-curved plates into the structure for forming the rings, can drive into and out of the structure. 
     FIG. 21  shows a forklift truck with a yoke on a turntable positioning a pre-curved plate on the templates. 
     FIG. 21  shows a forklift truck  197  within the structure on floor  60  positioning a plate  199  on the templates  121  with the help of a worker. Forks of the forklift engage the base  117  of the turntable for raising and lowering yoke  115 , which has recesses in its end for engaging interior cleats  111  welded to interior surfaces of plate  199 . When all of the plates necessary for constructing one ring are positioned, the forklift truck  197  remains within the structure while vertical welds along vertical edges of the plates in that ring are welded to form the ring. After the lifters raise the ring in the above structure, the forklift drives off the floor  60  to return with pre-curved plates for the next ring. In the final positioning of the final plate in the bottom ring, one vertical edge of the plate is positioned near the vertical edge of the adjacent plate. A gap is left between the opposite vertical edge of the plate and the next adjacent plate so that the forklift  197  may exit the structure before pulling the final plate into position. 
   While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention, which is defined in the following claims.
Large tanks are built by welding pre-formed plates in operations near the ground. An annular concrete base with extended lifter pads is poured. Floor plates are lifted using lifting nuts, are placed on compacted sand and river gravel and are welded laterally. Peripheral templates are welded to the floor. Nested pre-curved plates are transported vertically. Forklifts move the plates using cleats, yokes and turntables. Pre-curved plates are welded vertically, forming a first ring. A roof is built on and welded to the first ring. The first ring and roof are lifted with self-climbing hydraulic lifters on lifting pillars. Additional rings are assembled in sequences of plate positioning, vertical welding, lowering the above structure using guides and spacers, horizontal welding, lifting, repeating the steps, and finally welding the bottom ring to the floor.