"PROCESS AND SYSTEM FOR REPLACING THE FIXED ROOF OF A STORAGE TANK"

Abstract

"METHOD AND SYSTEM FOR REPLACING THE FIXED ROOF OF A STORAGE TANK" The present invention discloses a method for replacing the fixed roof of a storage tank, comprising the steps of pre-assembling a roof on a floor of a tank basin in the form of modules and assembling the modules on a top of the tank. Furthermore, the present invention discloses a system for replacing the fixed roof of a storage tank, characterized in that it comprises: a jig, a coil support, at least one roof module, a plurality of eyelets, a step beam and a hoisting means.

Description

Title of the invention: “METHOD AND SYSTEM FOR REPLACING THE FIXED ROOF OF A STORAGE TANK” Field of invention

[0001] The present invention relates to the technical fields of maintenance and supply installations. More specifically, the present invention relates to a method and system for replacing the fixed roof of storage tanks. Background to the invention

[0002] Storage tanks are a fundamental piece of equipment in oil refineries and logistics terminals. Despite its relatively simple design, compared to other equipment in the oil and gas industry, the costs associated with its maintenance are often high, especially in older facilities.

[0003] Building or replacing the roof of a storage tank is a maintenance activity that, admittedly, requires a lot of man-hours, machinery and material resources. In recent years, efforts have been made not only to maintain extensive storage facilities, but also to carry out maintenance activities in a productive, efficient and safe manner.

[0004] There are different types of storage tank roofs, generally fixed roofs, external floating roofs, internal floating roofs, external vaulted floating roofs, horizontal roofs, pressure roofs and variable vapor space roofs.

[0005] To date, it is known that the replacement of fixed roofs can normally be carried out using two techniques known in the industry: "sheet to sheet" hoisting or ramping. In "sheet to sheet" hoisting, one sheet is raised at a time, and on the ramp, a scaffolding ramp is mounted to access the roof, where the roll of the sheet is unrolled to a length equivalent to the diameter of the tank; the cut sheet is positioned in the center of the roof, and it is distributed from the center of the roof to the ends.

[0006] In the context of refineries, factors that can create difficulties in tank maintenance activities must also be considered. For example, the use of routine contracts for roof replacement. Since the importance of the tank is perceived as less than that of other processing units, each time a processing unit needs to be maintained, the personnel initially engaged for tank maintenance are transferred to the maintenance of another processing unit.

[0007] Another factor may be the lack of flexibility of the tank park which, combined with market demands, leads to restrictions on the release of tanks for maintenance.

[0008] It is therefore necessary to improve roof replacement techniques to meet the requirements of productivity, technical-economic efficiency and safety, which can be applied to any refinery or processing plant that has a storage area, such as refineries, terminals and petrochemical plants. State of the art

[0009] In the current state of the art, there are documents which contain teachings on roof replacement techniques.

[0010] The said technique is a page on the Gairns Santos Engineering company website, available at: https: / / www.gsei.ca / projects / high-density-tank-newstainless-steel-roof. This page presents a company project entitled “New High Density Tank Stainless Steel Roof”, which involves a 11.7 m diameter stainless steel storage roof. The roof is pre-assembled in two panels, each corresponding to one half of the roof. The halves consist of pre-fabricated plates, a tension ring at the edges and stiffening by beams. The roof lifting points are welded to each panel to allow lifting via a lifting frame between the panel and the crane.

[0011] The said technique is a page on the Gairns Santos Engineering company website, available at: https: / / www.gsei.ca / projects / storage-tank-roofreplacement. This page presents a company project entitled “Storage Tank Roof Replacement”, which involves a 9.8 m diameter stainless steel storage roof. The roof is pre-assembled into panels, each of which contains part of an edge tension ring, a center tension ring and roof sheet stiffening beams. Each panel is directly hoisted onto the tank roof using a crane and cables.

[0012] However, the above-mentioned techniques stiffen the roof with beams. These beams remain welded to the roof after assembly. This increases replacement costs, in addition to increasing the overall mass of the roof, especially when hoisting large diameter tanks, which is not addressed by the above-mentioned techniques.

[0013] Another technique is described in JPS 59224777, which presents a technique for assembling a spherical roof for a large storage tank. In this document, it is proposed to weld a roof sheet and an annular material to the roof sheet on the ground (in a factory or on site) to form a unit, and then fix the unit between the roof sheets on a pedestal / support. The beam material and the ring material are welded to the roof sheet on the ground to form a unit. Adjacent units are welded to each other and the rings are joined to form a spherical roof. Work inside the roof after the units are installed is limited to joining the ring material and the beam material at the radial joint between the units.

[0014] However, as described in this document, spherical roofs are conventionally mounted with the support of a scaffolding structure on top of the tank. Furthermore, this document teaches that the circumferential beams are welded with the roof sheets in order to clearly stiffen the roof.

[0015] Therefore, the state of the art still has obvious shortcomings. The features and advantages of the present invention will therefore become clear from the detailed description below and with reference to the attached drawings, which are provided only as preferred and non-limiting embodiments. Brief description of the invention

[0016] The present invention discloses a method for replacing the fixed roof of a storage tank, comprising the steps of pre-assembling a roof on a floor of a tank basin in the form of modules and assembling the modules on a top of the tank. Furthermore, the present invention discloses a system for replacing the fixed roof of a storage tank, characterized in that it comprises: a jig, a coil support, at least one roof module, a plurality of eyelets, a step beam and a hoisting means. Brief description of the figures

[0017] In order to complete the present description and to obtain a better understanding of the characteristics of the present invention, figures are indicated in which are represented, by way of example and in a non-limiting manner, its preferred embodiments.

[0018] [Fig.l] illustrates an exemplary embodiment of the present invention.

[0019] [Fig.2] illustrates a preferred embodiment of a walking beam (2).

[0020] [Fig.3] illustrates an exemplary embodiment of a sample (7).

[0021] [Fig.4] illustrates an exemplary embodiment of a coil holder (8) comprising a coil (9).

[0022] [Fig.5] illustrates a preferred embodiment of mooring eyes.

[0023] [Fig.6] illustrates an exemplary embodiment of a set of mooring eyes and a tirfor (13).

[0024] [Fig.7] illustrates a graph of a physical progress curve for performing a fixed roof replacement service, using the present invention compared to a state-of-the-art technique.

[0025] [Fig.8] illustrates a bar graph relating to the reduction in the cost of replacing a fixed roof, using the present invention compared to a state-of-the-art technique.

[0026] [Fig.9] illustrates a bar graph relating to the reduction in time of exposure to risk in working hours, using the present invention compared to a state-of-the-art technique.

[0027] [Fig. 10] shows the result of an operation to replace a real fixed roof using the method of the present invention.

[0028] [Fig. 11] illustrates a hoisting step of an operation to replace a real fixed roof using the method of the present invention.

[0029] [Fig. 12] shows the result of the finishing and remaining material of an actual fixed roof replacement operation using the method of the present invention. Detailed description of the invention

[0030] The present invention relates to a method and system for replacing the fixed roof of a storage tank. The invention is mainly aimed at replacing the roof of APL650 tanks, used in processing, refining and petrochemical installations.

[0031] It will be appreciated that the present invention provides a significant cost reduction, since the equipment downtime is reduced, in conjunction with the great increase in productivity in welding and roof assembly. In addition, tank downtime is reduced compared to the use of the prior art.

[0032] Furthermore, it should be noted that the present invention allows parallelism in the execution of the steps and promotes flexibility in the use of labor. Furthermore, it is important to emphasize that the present invention reduces the exposure of employees to work at height, which significantly increases the safety level of the activity, given that most of the execution time of the roof replacement is at ground level.

[0033] The method of this invention applied to the replacement of the fixed roof of storage tanks essentially consists of pre-assembly and assembly steps. A preparation step may optionally be carried out in parallel with the pre-assembly step, or between the pre-assembly step and the assembly step.

[0034] Although the steps of the present invention are generally sequenced, a person skilled in the art will appreciate that the nature of these steps allows other equipment maintenance activities to be performed in parallel, thereby generating a reduction in the final delivery time, as well as a reduction in the final cost of maintenance, and mainly, a reduction in working hours exposed to the risk of working at height.

[0035] In a non-exhaustive manner, the following advantages are expected from the implementation of the present invention compared to the state of the art:

[0036] Reduction in the number of working hours exposed to risk and increase in the availability of equipment undergoing maintenance;

[0037] Reduction of the specific cost expected for the maintenance of equipment and increase in productivity thanks to the reduction of risks inherent in the activity linked to working at height;

[0038] Protection and preservation of the health and integrity of the performing employee;

[0039] Better quality of welding service, because the welder is not suspended in a risky situation, but on the ground. This allows for improved working conditions and the use of more productive and better quality welding techniques;

[0040] Use of roofing materials with low corrosion rates, which reduces the risk of roof perforation. A leaky roof allows rainwater to enter the tank, which must then be drained and treated before being released into the environment. In addition, the presence of water inside the tank can cause corrosion of the bottom of the tank, which will lead to hydrocarbon contamination of the soil;

[0041] Reduction of occupational risks and stress inherent in the activity of maintaining storage tanks, most of the operations being carried out at ground level;

[0042] Increase in the range of automated welding processes and, consequently, significant improvement in the productivity of the roof replacement activity.

[0043] The present invention makes it possible to prefabricate large modules of the fixed roof of a storage tank on the ground, to prepare them and to assemble / transport them to the top of said tank in a safe and efficient manner. The invention comprises at least the following elements: a jig, a coil support, at least one roof module, several mooring eyes, a step beam and a hoisting means.

[0044] As shown in [Fig.l], an exemplary embodiment of the present invention illustrates a carrier cable (1) of a jig hoisting crane ([Fig.3]), which comprises carrier cables (3) connected to a roof module (4).

[0045] As shown in [Fig.3], the template (7) is a support structure constructed from structural profiles (e.g., scaffolding tubes) that include a layout corresponding to a section of a circumferential area of ​​the roof. This template serves as a support for welding the roof modules, avoiding any contact between the areas to be welded and the ground. In addition, the template reproduces the layout of the sheets on the roof of the tank in accordance with the design of the equipment.

[0046] 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 support coil support (8) is preferably placed close to the template ([Fig.3]), preferably on one side thereof, in order to allow the sheets to be unwound onto the template (7). It will also be appreciated that the coil support (8) can be moved relative to the template (7), in order to facilitate the lateral arrangement of the sheets.

[0047] Therefore, when the sheets are arranged on the template (7), overlap welding is carried out to start the formation of a roof module (4). This arrangement allows the use of semi-automatic welding techniques (the most commonly used semi-automatic welding processes are GMAW -MIG / MAG and FCAW - Tubular Wire), which generates excellent technical and economic results for the entire process, such as the reduction of the roof manufacturing time and the quality of the weld bead.

[0048] The sheets preferably have a thickness of at least 4 mm, due to the safety conditions required to withstand atmospheric electric discharges.

[0049] Furthermore, the choice of using 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 assembly step.

[0050] The mooring eyes are then welded. These are preferably made of stainless steel and distributed in pre-defined positions on the roof module.

[0051] As illustrated in [Fig.5], the eyelets are preferably composed of two sheets (11, 12) and a tie (10). One sheet is square (12) and the other rectangular (11). The square sheet (12) has a through hole for attaching the tie (10) and is welded perpendicular to the rectangular sheet (11). The rectangular sheet (11) is welded, in parallel, in its respective predefined position on the roof module (4). Once the hoisting and assembly of the roof modules (4) is completed, 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.

[0052] The step beam (2) is designed to allow the fabricated roof module (4) to be hoisted onto the jig (7) to maintain the stability and integrity of the sheet metal. Furthermore, it will be appreciated that the step beam (2) is sized to work with both quarter-form and half-form modules.

[0053] As illustrated in [Fig.2], the step beam (2) has a generally square shape and comprises mooring means (5, 6) responsible for connecting a roof module (4) manufactured on the template ([Fig.3]). This connection is made by means of the mooring eyes which are installed in the module manufactured on the template ([Fig.3]). The connection between the mooring means of the step beam (2) and the mooring eyes mounted on the module is made using support cables (3). Said support cables (3) are preferably steel cables.

[0054] As illustrated in [Fig.6], the mooring means also comprise respective tirfors (13). The tirfor (13) allows the length (tension) of the carrier cable to be adjusted in order to keep it taut.

[0055] Therefore, when the support cable assemblies (3) and tirfor (13) of the walking beam (2) are connected to the eyelets of the module (4) to be towed, the support cables (3) are correctly tensioned to apply an equally distributed support tension on the module (4), so that it is aligned.

[0056] Once tensioning is complete, the module (4) can be hoisted to the top of the tank roof. For safety reasons, hoisting may involve hoisting the module (4) a certain distance above the jig (7) (e.g., a few centimeters) and waiting for a predetermined time (approximately 10 minutes), in order to allow verification that all loads are correctly balanced and that all cables are correctly tensioned. This check can be carried out visually by an operator.

[0057] Then, the procedure of hoisting the module (4) to the top of the tank continues. After the assembly of a first module (4), the assembly steps of the remaining number of modules (4) are repeated, on the same template (7), for all the transport steps described above.

[0058] After assembling and hoisting the necessary modules (4) onto the top of the tank, the adjustment, alignment and cutting of the sheet metal flashings begins. The modules (4) are then welded together to form the roof itself. Results of the invention

[0059] As illustrated by the graphs of Figures 7, 8 and 9, the present invention provides substantial advances over the state-of-the-art methods currently implemented in fixed roof replacement operations.

[0060] As illustrated by the graph in [Fig.7], a gain of approximately two months was observed with the implementation of the present invention, compared to the prior art (sheet to sheet and ramp); that is, with completion in approximately 80% of the total time required by the prior art.

[0061] Furthermore, as illustrated by the graphs of Figures 8 and 9, the present invention has enabled, respectively, a significant reduction in costs of about 28% and labor hours of about 58% compared to the prior art.

[0062] Finally, as illustrated in Figures 10, 11 and 12, the present invention has already made it possible to pre-assemble, transport and safely assemble roofs for tanks with a diameter of up to 45 m, the only remaining material being the support sheets of the mooring eyes. The present invention therefore appears to be much more efficient in terms of cost and weight.

[0063] Those skilled in the art will appreciate the knowledge presented herein and will be able to reproduce the invention in the indicated embodiments and in other variations, covered by the scope of the accompanying characteristics. Favorite Achievements

[0064] In a preferred embodiment, the present invention comprises a method of replacing the fixed roof of a storage tank, which comprises the following steps:

[0065] pre-assembling a roof on a floor of a tank basin in the form of modules, comprising the following steps:

[0066] constructing a template (7), made from welded structural profiles, which reproduces the arrangement of the sheets on the roof of the tank and whose shape corresponds to a section of a circumferential area of ​​the roof;

[0067] positioning a coil holder (8) comprising a coil (9) of metallic material on one side of the constructed jig;

[0068] unwinding the metal material from the coil holder (8) onto the template (7) constructed to form sheets;

[0069] welding the sheets so that they overlap when the sheets are arranged on the template to form respective modules (4); and

[0070] weld the mooring eyelets to the formed modules (4);

[0071] assembling the modules (4) on top of the tank, which comprises the following steps:

[0072] connecting a walking beam (2) to the respective mooring eyes by means of a plurality of support cables (3);

[0073] adjusting the tension of the respective cables of the plurality of support cables connected to the walking beam, in order to ensure the alignment of the formed module (4);

[0074] hoist the formed module (4) to the top of the tank;

[0075] repeating steps (b) to (e) of the pre-assembly step for a new module;

[0076] weld the modules (4) together to form the roof of the tank.

[0077] Wherein the method may also comprise a preparation step, to be carried out in parallel with the pre-assembly step, or between the pre-assembly step and the assembly step, wherein the preparation step comprises the following steps:

[0078] f) emptying, isolating and cleaning the tank;

[0079] g) assembling the drum barges and scaffolding, followed by closing and filling the tank with water; and

[0080] h) inspection and maintenance of the roof beams of the tanks using barges.

[0081] Wherein in the pre-assembly step, step (a) may comprise manufacturing a template (7) with a section of circumferential area of ​​between at least one quarter and one half of the total circumferential area of ​​the roof.

[0082] Wherein in the pre-assembly step, step (c) may comprise moving the spool holder (8) along the side of the constructed jig (7).

[0083] Wherein the assembly step may further comprise, between steps (j) and (k), a step consisting of: jl) transporting the formed module (4) to a certain distance from the template (7) and waiting for a predetermined time.

[0084] In another preferred embodiment, the present invention comprises a system for replacing the fixed roof of a storage tank, which comprises, at least:

[0085] a template, constructed from structural profiles, the layout of which corresponds to a section of a circumferential area of ​​the roof;

[0086] a coil holder comprising a coil of metallic material, from which the sheets are unwound onto the jig;

[0087] at least one roof module, formed from sheets unrolled 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;

[0088] a plurality of mooring eyelets respectively welded to at least one roof module;

[0089] a walking beam comprising a plurality of suspension cables connected to respective ones of the plurality of mooring eyes of the roof module; and

[0090] a hoisting means for hoisting the respective roof modules to the top of the tank using the step beam.

[0091] In which the template (7) may correspond to a section of a circumferential surface comprised between at least a quarter and half of the total circumferential surface of the roof.

[0092] Wherein the spool holder (8) can be moved along one side of the jig (7).

Claims

Claims

1. A METHOD FOR REPLACING THE FIXED ROOF OF A STORAGE TANK, characterized by the steps of: pre-assembling a roof on a floor of a tank basin in the form of modules, comprising the following steps: a) constructing a template (7), made from welded structural profiles, which reproduces the arrangement of the sheets on the roof of the tank and whose shape corresponds to a section of a circumferential area of the roof; b) positioning a coil holder (8) comprising a coil (9) of metallic material on one side of the constructed template; c) unwinding the metallic material from the coil holder (8) onto the constructed template (7) to form sheets; d) welding the sheets so that they overlap when the sheets are arranged on the template to form respective modules (4); and e) welding mooring eyes to the formed modules (4);assembling the modules (4) on top of the tank, which comprises the following steps: i) connecting a step beam (2) to the respective mooring eyes by means of a plurality of support cables (3); j) adjusting the tension of the respective ones of the plurality of support cables connected to the step beam, in order to ensure the alignment of the formed module (4); k) hoisting the formed module (4) to the top of the tank; 1) repeating steps (b) to (e) of the pre-assembly step for a new module; m) welding the modules (4) together to form the roof of the tank.;

2. A method according to claim 1, characterized in that it further comprises the following steps: preparation, to be carried out in parallel with the pre-assembly step, or between the pre-assembly step and the assembly step, wherein the preparation step comprises the following steps: f) emptying, isolating and cleaning the tank; g) assembling the drum barges and scaffolding, followed by closing and filling the tank with water; and

3.

4.

5.

6.

7.

8.

9. (h) inspection and maintenance of tank roof beams using barges. METHOD, according to claim 1, characterized in that in the pre-assembly step, step (a) comprises the manufacture of a template (7) with a section of a circumferential area of between at least a quarter and half of the total circumferential area of the roof. METHOD, according to claim 1, characterized in that in the pre-assembly step, step (c) comprises moving the coil holder (8) along the side of the constructed jig (7). METHOD, according to claim 1, characterized in that in the pre-assembly step, step (d) is carried out by semi-automatic welding processes. METHOD, according to claim 1, characterized in that in the assembling step, step (j) further comprises using a tirfor (13) to adjust the tension of the respective cables of the plurality of support cables (3). METHOD according to claim 1, characterized in that the assembly step further comprises, between steps (j) and (k), a step consisting of: jl) transporting the formed module (4) to a certain distance from the template (7) and waiting for a predetermined time. METHOD, according to claim 1, characterized in that the assembly step further comprises, before step (m), a step consisting of: ml) mount and adjust the modules (4) on top of the tank, including alignment and cutting of the sheet burrs. SYSTEM FOR REPLACEMENT OF THE FIXED ROOF OF A STORAGE TANK, characterized in that it comprises: a template (7), constructed from structural profiles, the layout of which corresponds to a section of a circumferential area of the roof; a coil holder (8) comprising a coil (9) of metallic material, from which the sheets are unwound onto the template (7); at least one roof module (4), formed from sheets unrolled from the coil (9), which are positioned on said template (7) and welded together

10.

11.

12.

13.

14. to form a part of the roof corresponding to the shape of the template (7); a plurality of mooring eyes respectively welded to at least one roof module (4); a walking beam (2), comprising a plurality of support cables (3) connected to respective ones of the plurality of mooring eyes of the roof module (4); and a hoisting means for hoisting the respective modules from the roof to the top of the tank using the walking beam (2). SYSTEM, according to claim 9, characterized in that the template (7) corresponds to a section of a circumferential surface comprised between at least a quarter and half of the total circumferential surface of the roof. SYSTEM according to claim 9, characterized in that the coil holder (8) can be moved along one side of the template (7). SYSTEM, according to claim 9, characterized in that the welding of the sheets together is carried out by a semi-automatic welding process. SYSTEM according to claim 9, characterized in that each eyelet is composed of a pair of welded sheets (11, 12) and a link (10). SYSTEM, according to claim 9, characterized in that it further comprises a plurality of tirfors (13) for forming traction and tension assemblies with the respective cables of the plurality of carrier cables (3) and eyelets.

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