Patent Application
20150136799
The present application relates generally to storage tanks for storing liquids and granular solids (dry bulk commodities), and more particularly to storage tanks constructed of curved steel panels.
Large cylindrical storage tanks for liquids and granular solids may be constructed from a plurality of panels that are curved in the form of an arc and are fastened together. For example, a tank may have six panels connected end-to-end, each covering a sixty-degree arc, to form the circumference of the tank. The panels may be stacked vertically to provide a desired tank height. By way of further example, a storage tank may be four panels high, with each level having six circumferential panels, such that twenty-four panels are required in total to construct the tank. The arc angle and number of panels needed to form the circumference are adjustable depending on the tank design. Similarly, the number of height levels is subject to design choice.
Each tank panel is provided with a pair of parallel flanges, one along each longitudinal edge of the panel. A plurality of bolt holes are provided through each flange for attachment of the panel to adjacent panels above and below, to a supporting base structure below, and/or to a roof structure above. Further groups of bolt holes are provided at each opposite end of the panel across the width of the panel for attachment of the panel end-to-end with adjacent panels in the same height level of the tank structure. Each flange is provided with “chime region” offset toward the longitudinal centerline of the panel at one end of the panel to accommodate slight overlap of an adjacent panel for bolted connection of the panels.
Each panel may be formed from an elongated rectangular piece of steel plate on the order of forty feet long by ten feet wide. Plate thickness may vary depending on the tank requirements, and it is known to use ¼ inch, 5/16 inch, and ⅜ inch steel plate among other possible thicknesses. A piece of steel plate that is 40 ft×10 ft×3/8 in weighs approximately 6,126 pounds.
It is known to form flanges in a metal plate using a press brake. With a plate approaching forty feet in length, it is challenging and time consuming to form two parallel flanges along opposite longitudinal edges using a press brake. A first flange must be formed, and then the plate must be removed from the press brake and rotated 180 degrees to engage the opposite edge in the press brake to form the second flange. Sequential formation of flanges in this manner introduces quality control problems wherein the flanges are not parallel with one another to a suitable tolerance. Moreover, handling of the large plate to switchover from one edge to the other involves time, material handling equipment, and significant operator skill. Use of a press brake to form the flanges is not ideal from either a quality standpoint or an efficiency standpoint. Use of a press brake to form the flanges also imposes a length limitation on the panel.
Making the chime region of each flange may involve further operations. For example, a notch may be cut in the plate at the corresponding corner, and a separately fabricated chime piece may be welded to the corner portion of the plate to provide the chime region. Of course, this must be repeated at the opposite corner.
As may be appreciated, poor quality and lack of consistency in the formed panels will cause delays during tank construction and possibly result in tank leakage. What is needed is a more efficient and economical process of making flanged curved panels for a cylindrical storage tank, wherein the resulting panels are of consistently high quality.
The present invention provides a process for manufacturing flanged curved panels that overcomes the problems mentioned above while reducing the cost and time invested in making the panels relative to prior methods.
In an embodiment of the present invention, a flat plate is automatically conveyed into a CNC cutting station, which may include a high definition plasma cutter or laser cutter, to form all bolt holes and cut-out features (i.e. doors, inlet and outlet pipe holes), and to trim the plate to a defined outer dimension. After the cutting station, the plate is automatically conveyed into a roll-forming line configured to progressively bend both longitudinal edges of the plate to form parallel longitudinal flanges. When the leading end of the plate exits out of the roll-forming line, respective leading end regions of the two flanges may undergo a swaging operation by a pair of opposing hydraulically-powered swage dies each acting in a direction lateral to the flow direction of the plate through the roll-forming line. The swaging operation forms an integral chime region of each flange. After the swaging operation, the plate is automatically conveyed into a roll bending unit configured to curve the flanged plate into an arc to form a finished panel. A movable cradle shaped to support the curved panel may be actuated to receive and support the panel, and to move the panel to a position wherein the panel may be transferred to a shipping crate specially designed to securely hold a plurality of nested panels.
As may be appreciated, the process of the present invention avoids the use of a press brake and provides repeatable formation of highly parallel flanges. The process may also avoid a welding operation associated with forming the chime regions. Operator skill is largely removed from the process, resulting in greater uniformity in the manufactured panels.
Features and advantages of embodiments of the present disclosure will become apparent by reference to the following detailed description and drawings, in which:
The present invention provides a process for manufacturing curved panels for use in constructing large cylindrical storage tanks for storing contents such as liquids and dry bulk commodities in granular form. As one non-limiting example, the panels made by the disclosed process may be used to construct water storage tanks.
Each panel is formed from a large plate of steel P. The dimensions of plate P will depend on the overall dimensions of the tank to be constructed. For purposes of indicating an order of magnitude, it is understood that plates P may be on the order of forty feet long by ten feet wide by ⅜ inches thick. These dimensions are subject to variation depending on the tank design.
Initially, a flat plate P received from a steel mill is loaded onto an automated in-feed conveyor 12 of equipment layout 10. The loading may be carried out using a plate-lifting hoist supported by an overhead traveling gantry. The loading step is designated as step 100 in
In-feed conveyor 12 feeds the flat plate P forward (to the right in
Once all holes and cut-out features have been formed and the plate trimmed by cutting station 14 in accordance with step 104, plate P is conveyed out of cutting station 14 by an automated conveyor 16, which in turn conveys the plate into a roll-forming line 18. The conveyance of plate P from cutting station 14 to roll-forming line 18 is labeled step 106 in
Roll-forming line 18 comprises a plurality of roll-forming stations configured to progressively bend the longitudinal edges of plate P to form a pair of parallel flanges F extending the length of plate P (a leading end portion of one flange F is visible in
Equipment layout 10 may comprise a pair of swaging stations 20A, 20B located on opposite sides of the flow path. Swaging stations 20A, 20B may be configured and tooled with corresponding swage dies 22A, 22B and corresponding swage blocks (not shown) to perform a swaging operation upon a leading end region of each flange F on opposite sides of plate P.
With respect to steps 108 and 110, it is highly desirable that all tank panels, and thus plates P, have a standard width because this will avoid set-up time needed to reconfigure roll-forming line 18 and swaging stations 20A, 20B to accommodate a different plate width. Moreover, it is desirable to choose a plate width that is a standard mill size, e.g. 120 inches, to avoid cost and delay associated with procuring custom plate sizes.
From swaging stations 20A, 20B, the flanged plate P is conveyed by an automated conveyor 24 into a roll bending unit pursuant to step 112 in
Roll bending unit 26 includes a configuration of parallel pinch rollers for curving flanged plate P into an arc. For example, plate P may be curved to form a sixty-degree arc to define a portion of a tank circumference. This step is designated by reference numeral 114 in
As the curved and flanged plate P emerges from bending unit 26, it may be supported by a vertically and horizontally movable cradle 28 positionable at an exit end of bending unit 26. Cradle 28 may be shaped to receive and support the curved and flanged plate P so as prevent damage to the plate and deviation of the formed curvature. In the present embodiment, cradle 28 is initially actuated to a receiving position near bending unit 26. Once the curved and flanged plate P is received by cradle 28, the cradle is actuated to retract the cradle from bending unit 26 and lower the cradle to the ground. The cradling operation is designated by step 116 in
Finally, the plate (now referred to as a formed panel FP), is safely transferred to a shipping crate 30 for transport to a site where blasting and coating may be performed in accordance with step 118 in
While the invention has been described in connection with exemplary embodiments, the detailed description is not intended to limit the scope of the invention to the particular forms set forth. The invention is intended to cover such alternatives, modifications and equivalents of the described embodiment as may be included within the spirit and scope of the invention.
| Number | Date | Country | |
|---|---|---|---|
| 61904554 | Nov 2013 | US |
