METHOD AND SYSTEM FOR REPLACING THE FIXED ROOF OF A STORAGE TANK

Abstract

Embodiments of methods and systems for replacing a fixed roof of a storage tank. An embodiment of a method includes pre-assembling a roof on a floor of a tank basin in the form of modules, assembling the modules on a top of the tank, and welding the modules together to form the roof of the tank. An embodiment of a system for replacing the fixed roof of a storage tank includes a template, a coil support, a plurality of roof modules, a plurality of eyelets, a walking beam, and a hauler.

Claims

1. A system for replacing a fixed roof of a storage tank, the system comprising: a template, constructed from structural profiles, with an arrangement corresponding to a section of a circumferential area of the roof; a coil support comprising a coil of metallic material, from which sheets are uncoiled onto the template during installation; at least one roof module, formed from sheets uncoiled from the coil, positioned on the template and welded together so as to define a part of the roof corresponding to the shape of the template; a plurality of mooring eyelets respectively welded to the at least one roof module; a walking beam having a plurality of support cables connected to one or more respective mooring eyelets of the plurality of mooring eyelets of the roof module; and hauling means for hauling respective modules from the roof to a top of the tank using the walking beam.

2. The system according to claim 1, wherein the template corresponds to a section of a circumferential area of between at least a quarter and half of total circumferential area of the roof.

3. The system according to claim 1, wherein the coil support is configured to be moved along a side portion of the template.

4. The system according to claim 1, wherein when the welding of the sheets together, a semi-automated welder carries out the welding by semi-automated welding.

5. The system according to claim 1, wherein each of the plurality of mooring eyelets comprises a pair of welded sheets and a link.

6. The system according to claim 1, further comprising a plurality of tirfores, thereby to define hauling and tensioning assemblies with respective cables of the plurality of support cables and eyelets.

7. A system to replace a fixed roof of a storage tank, the system comprising: a template including a plurality of structural profiles having an arrangement corresponding to a section of a selected circumferential area of the fixed roof; a coil support including a coil of metallic material, the coil of metallic material configured so that sheets of metallic material are uncoiled therefrom onto the template for installation; one or more roof modules defined by the sheets when uncoiled from the coil and positioned on the template when welded together, thereby to form a part of the roof corresponding to a shape of the template; a plurality of mooring eyelets respectively connected to the one or more roof modules; a walking beam having a plurality of support cables connected to one or more respective eyelets of the plurality of mooring eyelets of the roof module; and a hauling assembly to haul respective modules from the roof to a top of the tank by use of the walking beam.

8. The system according to claim 7, wherein the template corresponds to a section of a circumferential area of between at least a quarter and half of a total circumferential area of the roof.

9. The system according to claim 7, wherein the coil support is configured to move along a side portion of the template.

10. The system according to claim 7, further comprising an automatic welder configured to weld the sheets together by semi-automated welding.

11. The system according to claim 7, wherein each of the plurality of mooring eyelets comprises a link connected to a pair of welded sheets.

12. The system according to claim 7, further comprising a plurality of tirfores, thereby to define one or more hauling assembly and one or more tensioning assemblies with respective cables of the plurality of support cables and the plurality of mooring eyelets.

13. A system to replace a fixed roof of a storage tank, the system comprising: a template including a plurality of structural profiles having an arrangement corresponding to a section of a selected circumferential area of the fixed roof; a coil support including a coil of metallic material, the coil of metallic material configured so that sheets of metallic material are uncoiled therefrom onto the template for installation; one or more roof modules defined by the sheets when uncoiled from the coil and positioned on the template when welded together, thereby to form a part of the roof corresponding to a shape of the template; a plurality of mooring eyelets respectively connected to the one or more roof modules; a walking beam having a plurality of support cables connected to one or more respective eyelets of the plurality of mooring eyelets of the roof module; and a plurality of tirfores to define one or more hauling assembly and one or more tensioning assemblies with respective cables of the plurality of support cables and the plurality of mooring eyelets, the one or more hauling assemblies configured to haul respective modules from the roof to a top of the tank by use of the walking beam.

14. The system according to claim 13, wherein the template corresponds to a section of a circumferential area of between at least a quarter and half of a total circumferential area of the roof.

15. The system according to claim 14, wherein the coil support is configured to move along a side portion of the template.

16. The system according to claim 15, further comprising an automatic welder configured to weld the sheets together by semi-automated welding.

17. The system according to claim 14, wherein each of the plurality of mooring eyelets comprises a link connected to a pair of welded sheets.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0018] In order to complement the present description and obtain a better understanding of the features of the present disclosure, figures are indicated in which, in an exemplified and non-limiting manner, its preferred embodiments are represented.

[0019] FIG. 1 illustrates an exemplary embodiment of the present disclosure.

[0020] FIG. 2 illustrates a preferred embodiment of a walking beam (2) according to the present disclosure.

[0021] FIG. 3 illustrates an exemplary embodiment of a template (7) according to the present disclosure.

[0022] FIG. 4 illustrates an exemplary embodiment of a coil support (8) comprising a coil (9) according to the present disclosure.

[0023] FIG. 5 illustrates the preferred embodiment of mooring eyelets according to the present disclosure.

[0024] FIG. 6 illustrates an exemplary embodiment of a set of mooring eyelets and tirfor (13) according to the present disclosure.

[0025] FIG. 7 illustrates a graph of a physical progress curve for executing a fixed roof replacement service, using the present disclosure in comparison with a technique from the state of the art.

[0026] FIG. 8 illustrates a bar graph relating to the reduction in the cost of replacing a fixed roof, using the present disclosure in comparison with a technique from the state of the art.

[0027] FIG. 9 illustrates a bar graph relating to the reduction in man-hour exposure time to risk, using the present disclosure in comparison with a technique from the state of the art.

[0028] FIG. 10 discloses a result of a true fixed roof replacement operation using the method of the present disclosure.

[0029] FIG. 11 discloses a hauling step of a true fixed roof replacement operation using the method of the present disclosure.

[0030] FIG. 12 discloses a result of the finish and remaining material of a true fixed roof replacement operation using the method of the present disclosure.

[0031] FIG. 13 is a flow chart of steps for replacing a fixed roof on a storage tank according to an embodiment of the disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0032] The present disclosure relates to a method and system for replacing the fixed roof of a storage tank. The disclosure is primarily aimed at replacing the roof of API-650 tanks, used in processing, refining and petrochemical facilities.

[0033] It will be appreciated that the present disclosure allows a significant reduction in costs, as the loss of profit from the equipment is reduced, in conjunction with the great increase in productivity in welding and roof assembly. Furthermore, there is a reduction in tank downtime compared to the use of prior art.

[0034] Furthermore, it should be noted that the present disclosure allows parallelism in the execution of steps and favors flexibility in the use of labor. Furthermore, it is important to highlight that the present disclosure reduces the exposure of employees to working at height, considerably increasing the level of safety of the activity, due to the fact that most of the execution time for replacing the roof is at floor level.

[0035] The method of this disclosure applied to replacing the fixed roof of storage tanks essentially consists of steps of pre-assembling and assembling. Optionally, a preparation step can be carried out in parallel with the step of pre-assembling, or between the step of pre-assembling and assembling.

[0036] Although the steps of the present disclosure are generally sequenced, it will be appreciated by a person skilled in the art that the nature of these steps allows other equipment maintenance activities to be carried out in parallel, thus, generating a reduction in the final delivery time, as well as a reduction in the final cost of maintenance, and mainly, reduction of man hours exposed to the risk of working at height.

[0037] Non-exhaustively, the following advantages are expected from the implementation of the present disclosure in relation to the state of the art: [0038] Reduction of man hour exposed to risk and increased availability of equipment undergoing maintenance; [0039] Reduction in the specific cost foreseen for equipment maintenance and increased productivity due to the reduction of risks inherent in the activity related to working at heights; [0040] Protection and preservation of the health and integrity of the performing employee; [0041] Better quality of the welding service, as the welder is not suspended in a risky condition, but on the ground. This leads to better working conditions, in addition to allowing the use of welding techniques with greater productivity and quality; [0042] Use of materials in the roof with low corrosion rates and, therefore, reducing the likelihood of the roof puncturing. A punctured roof allows rainwater to enter the tank, which then needs to be drained and treated before being discharged into the environment. Furthermore, the presence of water inside the tank can cause the bottom of the tank to corrode, which will lead to soil contamination with hydrocarbons; [0043] Reduction of occupational risk and labor stress inherent to the maintenance activity of storage tanks, as most of it is carried out at floor level; [0044] Increase in the range of automated welding process alternatives, and as a consequence, significant improvement in the productivity of the roof replacement activity.

[0045] The present disclosure allows large modules of a fixed roof of a storage tank to be prefabricated on the ground, prepared and assembled/hauled to the top of said tank safely and efficiently. The disclosure comprises at least the following elements: a template, a coil support, at least one roof module, a plurality of mooring eyelets, a walking beam, and a hauling means.

[0046] As can be seen in FIG. 1, an exemplary embodiment of the present disclosure illustrates a hauling cable (1) of a crane hauling a template (FIG. 3), which comprises support cables (3) connected to a roof module (4).

[0047] As can be seen in FIG. 3, the template (7) is a support structure constructed from structural profiles (for example, scaffold tubes) that comprise an arrangement corresponding to a section of a circumferential area of the roof. This template serves as a support for welding roof modules, avoiding contact between the areas to be welded and the floor. Furthermore, the template reproduces the arrangement of the sheets on the tank roof according to the equipment design.

[0048] As illustrated in FIG. 4, the coil support (8) consists of a structure and a coil (9) made of metallic material, preferably stainless steel. The coil support (8) is preferably positioned close to the template (FIG. 3), preferably on one side of it, in order to allow the sheets to be uncoiled onto the template (7). It will also be appreciated that the coil support (8) can be moved in relation to the template (7), to facilitate the arrangement of the sheets laterally.

[0049] Therefore, as the sheets are arranged on the template (7), overlapping welding is carried out to begin the formation of a roof module (4). This arrangement allows the use of semi-automated welding process techniques (the most commonly used semi-automatic welding processes are GMAW-MIG/MAG and FCAW-Tubular Wire), generating excellent technical and economic results for the process as a whole, such as reduction in roof manufacturing time and quality of the weld bead.

[0050] The sheets preferably have a thickness of at least 4 mm, due to the safety condition for withstanding atmospheric electrical discharges.

[0051] Furthermore, the selection for the use of modules (4) in the form of quarters or halves is conditioned by the total weight of the module and the availability of the crane to be provided for the step of assembling.

[0052] Mooring eyelets are then welded. These are preferably manufactured in stainless steel and distributed in previously defined positions on the roof module.

[0053] As illustrated in FIG. 5, the eyelets are preferably composed of two sheets (11, 12) and a link (10). One sheet is square (12) and the other rectangular (11). The square sheet (12) comprises a through hole for fixing the link (10) and is welded, perpendicularly, to the rectangular sheet (11). The rectangular sheet (11) is welded, in parallel, in its respective pre-defined position on the roof module (4). After finishing the hauling and assembly of the roof modules (4), it will be appreciated that the square sheets (12) can be removed/separated from the rectangular sheets (11), so that only the rectangular sheets (11) remain on the roof.

[0054] The walking beam (2) is designed to allow the hauling of the manufactured roof module (4) onto the template (7), in order to maintain the stability and integrity of the sheet. Furthermore, it will be appreciated that the walking beam (2) is dimensioned to work with both quarter-shaped modules and half-shaped modules.

[0055] As illustrated in FIG. 2, the walking beam (2) comprises a generally square shape and incorporates mooring means (5, 6) responsible for connecting a roof module (4) manufactured on the template (FIG. 3). This connection is made through the mooring eyelets that are installed in the module manufactured on the template (FIG. 3). The connection between the walking beam mooring means (2) and the mooring eyelets mounted on the module are carried out using support cables (3). Said support cables (3) are preferably steel cables.

[0056] As illustrated in FIG. 6, the mooring means also comprise respective tifores (13). The tirfor (13) allows the length (tensioning) of the support cable to be adjusted in order to keep it taut.

[0057] Therefore, when the sets of support cables (3) and tirfor (13) of the walking beam (2) are connected to the eyelets of the module (4) to be hauled, the support cables (3) are properly tensioned (taut) to apply an equally distributed support voltage across the module (4), so that it is aligned.

[0058] Once tensioning is complete, hauling the module (4) to the top of the tank roof can be started. For safety reasons, hauling may involve hauling the module (4) at a distance above the template (7) (for example, a few centimeters) and waiting a predetermined time (around 10 minutes), in order to allow verification that all cargo is properly balanced that all cables are correctly tensioned. Said check can be carried out visually by an operator.

[0059] Then, the procedure for hauling the module (4) to the top of the tank continues. After assembling a first module (4), the steps for assembling the remaining number of modules (4) are repeated, on the same template (7), for any and respective steps of hauling as described above.

[0060] After assembling and hauling the necessary modules (4) onto the top of the tank, the adjustment, alignment and cutting of sheet metal burrs begins. Then, the modules (4) are welded together, forming the roof itself.

RESULTS OF THE DISCLOSURE

[0061] As illustrated in the graphs in FIGS. 7, 8 and 9, the present disclosure brings substantial advances compared to the methods from the state of the art currently being implemented in operations for replacing a fixed roof.

[0062] As illustrated in the graph in FIG. 7, a gain of around two months was observed with the implementation of the present disclosure, compared to prior art (sheet-to-sheet and ramp); that is, with completion in approximately 80% of the total time required by the prior art.

[0063] Furthermore, as illustrated in the graphs in FIGS. 8 and 9, the present disclosure enabled, respectively, a significant cost reduction of around 28%, and man-hours of around 58%, compared to prior art used.

[0064] Finally, as further illustrated in FIGS. 10, 11 and 12, the present disclosure has already made it possible to safely pre-assemble, haul and assemble roofs for tanks up to 45 m in diameter, wherein the only remaining material is supporting sheets of the mooring eyelets. Therefore, the present disclosure appears to be much more efficient in terms of cost and weight.

[0065] Those skilled in the art will value the knowledge shown here and will be able to reproduce the disclosure in the indicated embodiments and in other variants, covered within the scope of the attached claims.

PREFERRED EMBODIMENTS

[0066] In a preferred embodiment, the present disclosure comprises a method for replacing the fixed roof of a storage tank, which comprises the steps of:

pre-assembling a roof on a floor of a tank basin in the form of modules, comprising the steps of: [0067] a) constructing a template (7), manufactured from welded structure profiles, which reproduces the arrangement of sheets on the tank roof and with a shape corresponding to a section of a circumferential area of the roof; [0068] b) positioning a coil support (8) comprising a coil (9) of metallic material on one side of the constructed template; [0069] c) uncoiling the metallic material from the coil support (8) onto the template (7) built to form sheets; [0070] d) welding the sheets in an overlapping manner as the sheets are arranged on the template to form respective modules (4); and [0071] e) welding mooring eyelets to the modules (4) formed;
assembling the modules (4) on a top of the tank, which comprises the steps of: [0072] i) connecting a walking beam (2) to respective mooring eyelets by means of a plurality of support cables (3); [0073] j) adjusting the tension of the respective cables of the plurality of support cables connected to the walking beam, to guarantee the alignment of the module (4) formed; [0074] k) hauling the formed module (4) to the top of the tank; [0075] l) repeating steps (b) to (e) of the step of pre-assembling for a new module; [0076] m) welding the modules (4) together to form the roof of the tank.

[0077] Wherein the method may further include a preparation step, to be carried out in parallel with the step of pre-assembling, or between the step of pre-assembling and assembling (see FIG. 13), wherein the preparation step includes the steps of: [0078] f) emptying, isolating and cleaning the tank; [0079] g) assembling drum barges and scaffolds, with subsequent closing and filling of the tank with water; and [0080] h) inspecting and maintaining tank roof beams using barges.

[0081] In another preferred embodiment, the present disclosure comprises a system for replacing the fixed roof of a storage tank, which comprises, at least: [0082] a template, constructed from structural profiles, with an arrangement corresponding to a section of a circumferential area of the roof; [0083] a coil support comprising a coil of metallic material, from which sheets are uncoiled onto the template; [0084] at least one roof module, formed from sheets uncoiled from the coil, which are positioned on said template and welded together to form a part of the roof corresponding to the shape of the template; [0085] a plurality of mooring eyelets respectively welded to the at least one roof module; [0086] a walking beam comprising a plurality of suspension cables connected to respective eyelets of the plurality of mooring eyelets of the roof module; and [0087] a hauling means for hauling respective roof modules to a top of the tank using the walking beam.