Construction method for fabrication and installation of outer tank steel dome of large-scale cryogenic storage tank

Abstract

The present invention provides a construction method for the fabrication and installation of the outer tank steel dome of a large-scale cryogenic storage tank, which includes the following steps: prefabrication site layout, prefabrication frame design and fabrication, prefabrication and assembly welding of the steel dome beam and slab, transfer of the dome module, installation of the central and edge supports, installation of the intermediate supports and hoisting and positioning of the dome module, installation of the remaining ring beam skin plates and track beams, installation of the sleeve stud accessories, and removal of the central and intermediate supports. The present invention has developed stress-free pairing of the dome module beams, dome camber maintenance technology, and a cyclic alternate column removal method for avoiding tearing of the welds of the dome steel structure. Through summarization, this construction method has been formed, and remarkable benefits have been achieved in the subsequent construction of multiple large-scale cryogenic storage tanks, and it is worthy of popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of steel domes, and particularly to a construction method for fabricating and installing the external tank steel dome of a large-scale cryogenic storage tank. Background Art

[0002] Currently, all-welded tanks with relatively high safety are usually adopted for large-scale cryogenic storage tanks. The external tank is made of reinforced concrete structure, and the steel internal tank includes components such as a 9Ni cylinder internal tank, a dome (carbon steel dome, aluminum ceiling), a lining plate, embedded parts, and a hot corner protection structure. The dome is fabricated from a steel structure reticulated shell and skin plates, and finally needs to be lifted to the designed elevation to serve as the "formwork bottom" for the casting of the external tank concrete dome. Since its fabrication and installation involve a large amount of prefabrication and welding of radial and circumferential beams and skin plates, high fabrication precision is required and the duration is long. If the beam and plate are assembled inside the tank, there will be a large number of cross operations with the simultaneous casting of the external tank concrete tank wall, seriously interfering with each other. Moreover, local personnel, equipment, and tools are highly concentrated, greatly increasing the safety risk; if prefabrication is carried out outside the tank and installation is carried out inside the tank, the reasonable division of large dome modules, the control of processing precision, and the deformation control during transportation and positioning are of top priority.

[0003] The applicant has constructed two 220,000 m³ LNG cryogenic storage tanks with the largest single capacity in China (a certain storage tank project in Binhai, Jiangsu). The radius of the steel dome reaches 88 m, the span is 87.86 m, the central vertical height is 11.38 m, and the dome reticulated shell is composed of 96 radial beams, 9 circumferential beams, 1 central ring, and 466 skin plates. The super-large dome weighs 829 t. Combining the experience accumulated from the construction of multiple large-scale cryogenic storage tanks in China, the applicant reasonably divides the dome prefabricated modules into two categories of large and small modules, 12 of each, and 1 central ring, and has developed the stress-free assembly of dome module beams, the dome camber maintenance technology, and the cyclic alternate column removal method to avoid the tearing of the steel structure welds of the dome. Through summarization, this construction method is formed, and remarkable benefits have been achieved in the subsequent construction of multiple large-scale cryogenic storage tanks, which is worthy of popularization and application. Summary of the Invention

[0004] To solve the above problems, the present invention discloses a construction method for fabricating and installing the external tank steel dome of a large-scale cryogenic storage tank.

[0005] The specific scheme is as follows:

[0006] A construction method for fabricating and installing the external tank steel dome of a large-scale cryogenic storage tank, characterized by comprising the following steps: prefabrication rack site layout, prefabrication rack design and fabrication, prefabrication and group welding forming of steel dome beam plates, dome module transfer, installation of central and edge supports, installation of intermediate supports and hoisting and positioning of dome modules, installation of remaining ring beams, skin plates and track beams, installation of sleeve studs and accessories, and removal of central and intermediate supports.

[0007] As a further improvement of the present invention, the specific steps of the prefabrication rack site layout are:

[0008] (1) Arrange the prefabrication frame site around the storage tank to reduce the walking distance of the crawler crane, but avoid the rotation radius of the tower crane and the walking route of the crawler crane;

[0009] (2) Determine the size of the prefabrication site according to the on-site conditions and prefabrication requirements. Set it to meet the simultaneous construction of three sets of prefabrication frames. For the prefabrication of the dome module, three sets of prefabrication frames are used for simultaneous construction, which is convenient for the prefabrication work to achieve flow operation according to beam alignment, beam welding, and skin plate welding, and reduce costs;

[0010] (3) The ground of the prefabrication frame site should be flat, solid, and clean, and drainage measures should be taken to prevent site settlement.

[0011] As a further improvement of the present invention, the prefabrication frame is composed of a bottom support, support columns, diagonal supports, and an upper support, and the overall shape is a fan-shaped structure. The specific steps for the design and manufacture of the prefabrication frame are as follows:

[0012] (1) Lofting with Tekla software 3D model; Since the steel dome is a spherical curved shape, it is necessary to loft at a scale of 1:1 through a 3D model to determine the height and spacing of the support columns of the prefabrication frame. The principle of the prefabrication frame is that according to the principle of vertical projection of light, the steel dome structure of the spherical curved surface is projected onto a horizontal plane, and a frame projection is obtained on the horizontal plane. The figure obtained from this projection is the position structure of the prefabrication frame, and appropriate points are selected as the support points of the steel dome. The principle of the support points is to be as close as possible to the intersection of the main beam and the ring beam, but it cannot interfere with the installation and welding operations of the ring beam during construction, nor can it affect the welding of the butt joints of the radial beams and the welding of the aluminum ceiling lifting lugs. And at least two support points are guaranteed for each section of the radial beam. The number of support points of the prefabrication frame depends on the size of the storage tank. After the support points are selected, measure the height from each support point to the ground in the software according to the curved surface height of the steel dome, which is the height of the support column of the prefabrication frame;

[0013] (2) Fabrication and installation of the prefabrication frame; The support columns are vertically arranged, the bottom support is placed at the lower end of the support columns, and the upper ends of adjacent two support columns are connected by the upper support. The diagonal support is used for laying steel gangplanks; The bottom support uses 12*250*250mm steel plates, the support columns use HW150*150*7*9 steel sections, the upper support uses 10# channel steel, and ∠80 angle steel is used as the diagonal support for laying steel gangplanks. The height of the steel gangplank from the end face of the support column is set at a position of 1.2 meters;

[0014] (3) Prefabricated frames are placed. Three sets of prefabricated frames are used for placement. Considering the continuity of construction workers, two large prefabricated frames and one small prefabricated frame are used. The large prefabricated frame is placed close to the tank body to ensure that the crawler hoisting weight can meet the requirements. In order to save the floor space of the prefabricated frames, the three sets of prefabricated frames are arranged with the large and small heads swapped, and the steel springboards of the three sets of prefabricated frames are on the same horizontal plane. When 3D modeling, it is necessary to consider that the columns of the prefabricated frames are on the same axis as much as possible, and the large and small end support columns must be at the same height, so that the steel springboards can be on the same horizontal plane, which is convenient and safe for construction. After the prefabricated frame is installed, use a level to mark the 1m line position on each column, measure the actual height of the column upward from the 1m line, and then adjust the height of the column according to the drawing size. Since the concrete floor may sink, the prefabricated frame should be re-measured regularly to check whether there is any settlement. Only after the re-measurement is qualified can the prefabrication of the next steel dome block be started.

[0015] As a further improvement of the present invention, the specific steps of prefabrication and welding of the steel dome beams and slabs are as follows:

[0016] (1) Prefabrication: The steel dome is composed of H-shaped steel and skin panels. Since the tank dome is a spherical surface and the skin panels shrink in size during welding, the skin panels are rearranged according to the design drawings before cutting. The cutting dimensions of each skin panel are given, and the curvature and dimensions of the steel dome beams are inspected and accepted before cutting and beveling. Then, each steel section is numbered according to the drawings to avoid errors during installation. Among them, when the H-shaped steel is processed into radial beams and circumferential beams according to the radius of the steel dome using the hydraulic top bending process, if there is a deviation in the top bending, it can be checked on the curvature plate to ensure that the arch of the beam meets the requirements of the drawings;

[0017] (2) Assembly welding: First, place the prefabricated radial beams on the prefabricated frame, adjust the size and fix them with a clamp. After the radial beams are welded, install the annular beams. Check the size of the entire steel dome and the gap of the butt joint. Only after they are qualified can the welding work of the annular beams and radial beams be carried out.

[0018] (3) Forming: After the steel dome beams are welded, the skin panels are laid. The skin panels are laid piece by piece and layer by layer from the edge of the dome to the center. Only spot welding can be done during laying. After the entire skin panel is laid, it can be fully welded with the beam. The weld bead should be cleaned before welding the skin panel. The overhead weld between the plate and the beam should be welded first. After the overhead weld is completed, the short welds of the adjacent plates are welded, and finally the long welds are welded. The long welds are welded in sections along the same direction to reduce deformation.

[0019] As a further improvement of the present invention, the dome module transfer is to transfer the formed steel dome to the storage rack around the storage tank, and the specific steps are:

[0020] (1)Select a suitable lifting machine according to the weight and size of the steel dome for the transfer operation of the steel dome module;

[0021] (2)Determine the hoisting point layout with the assistance of Tekla software. During hoisting, two 10t manual chain hoists are used at the large end and small end of the steel dome respectively to adjust the steel dome module to a horizontal state. Three traction ropes need to be set during the displacement of the steel dome module to keep the steel dome block stable during the transfer process.

[0022] As a further improvement of the present invention, the center and edge supports are installed to support the small end and large end of the steel dome module through the center support and edge support respectively, specifically including the center support installation and the edge support installation, wherein,

[0023] I. The specific steps of the center support installation are as follows:

[0024] (1)Calculate the height of the center support according to the bottom elevation of the aluminum ceiling and the spherical radius of the steel dome. The outer diameter formed by the center support columns must match the outer diameter of the center ring, and the installation verticality shall not be greater than 1 / 1000 mm. The center support columns are made of 6 Ø273*10 seamless steel pipes;

[0025] (2)Install the center support platform at the center position of the storage tank. The center support columns are welded to the embedded parts on the bearing platform. To reinforce the center support, ∠75*6 angle steel and [18 channel steel are used to weld the scissors braces for reinforcement. To prevent the center support from tipping over due to uneven loads, each center support column is reinforced with a Ø159*8 steel pipe diagonal brace;

[0026] (3)After the center support platform is installed, weld the guide plate of the center ring on the platform columns, and mark the azimuth angle in advance on the center ring platform. Then use the tower crane to hoist and place the steel dome center ring in place;

[0027] II. The specific steps of the edge support installation are as follows:

[0028] (1)Calculate the height of the edge support according to the bottom elevation of the ceiling and the spherical radius of the steel dome. The edge support is made of Ø219*8 steel pipe. A steel plate with a width 100 mm greater than the diameter of the steel pipe and a length 100 mm longer than the radial beam web is welded on the steel pipe, and a positioning baffle is welded on the steel plate to facilitate the adjustment of the radial beam azimuth;

[0029] (2)When the formwork is lifted to the third layer of the wall, the edge support can be welded and connected with angle steel on the first ring of vertical and circumferential embedded parts on the inner side of the concrete outer tank wall. The position where the vertical embedded part is welded to connect the angle steel is generally at 3 / 4 of the edge support column. Since there are no vertical embedded parts at the large and small door openings, the edge supports at the large and small door openings need to be reinforced with angle steel as diagonal braces on the first ring of circumferential embedded parts.

[0030] As a further improvement of the present invention, the specific steps for installing the intermediate support and hoisting the dome module into place are as follows:

[0031] (1) Since the span of the steel dome module is very large, the camber at the center of gravity will sink after the steel dome is in place. The support at this part needs to be designed as an adjustable-height movable support to adjust the camber of the steel dome to meet the design requirements;

[0032] (2) The intermediate support uses a Ø159*8 steel pipe. Steel plates with a thickness of δ10*200*200 are welded at both ends of the steel pipe. Two lifting lug plates are welded on the upper steel plate, and the distance between the two lifting lug plates is 25 mm (the thickness of the lifting lug plate in the middle of the dome is 20 mm). All intermediate supports need to have the same length (for convenient calculation of the camber). A support is made for each intermediate support. The support is welded by [20 channel steel and steel plates. The height of the support is generally about 500 mm, which is convenient for the operation of the jack. At the same time, the strength of the support needs to be ensured. First, move the steel dome module from the storage rack around the tank to the circumferential road around the storage tank, and temporarily support it with the storage rack. Connect the intermediate support to the lifting lugs pre-welded on the dome module with bolts. At the same time, weld safety protection railings and install life ropes on both sides of the skin plate of the large steel dome module, and then hoist it as a whole.

[0033] (3) After the fourth-layer concrete wall of the outer tank is poured, start hoisting the steel dome;

[0034] a) Since the steel wire ropes used during the installation of the intermediate support are for displacement, the steel wire ropes for hoisting must be replaced when hoisting the dome module into place. Fine-tune the angle of the steel dome module by using the chain hoists set at the large end and the small end of the steel wire rope. After the hoisting angle of the steel dome module is basically consistent with the installation angle, the small end is slightly higher than the theoretical height by about 300 mm;

[0035] b) The crane slowly hoists the hook, and the speed should be 400 mm / min. Observe the settlement of the foundation and the load-bearing condition of the sling. Hoist the test lift to a height of about 300 mm above the ground and stop for 3 minutes. If there is no abnormal situation, continue hoisting. Otherwise, immediately stop the hoisting operation. When hoisting, three traction ropes need to be set on the steel dome module to pull the steel dome module. Lower the hook slowly. First, let the large end be in place on the edge support. Install two limit blocks on the edge support in advance, and then slowly lower the hook to place the small end of the steel dome on the center ring;

[0036] c) After the steel dome is hoisted into place, calculate the theoretical height of the center of gravity position through software, compare it with a level and a reference line, adjust the intermediate support with a 30t jack. After meeting the calculated theoretical support height, weld the stop block to fix it, and then the main crane can be unhooked and disengaged from the lifting lug;

[0037] 4) During the hoisting operation, a commander stands on the formwork platform of the outer concrete tank to mainly observe the distance between the steel dome module and the inner platform of the outer concrete tank formwork. After the steel dome module descends to a certain position, observe the landing situation of the steel dome module and contact the chief hoisting commander with a walkie-talkie. Another observer and communicator is arranged beside the operating room on the crane to ensure that the command information can be transmitted to the crane driver in time in case of any accident with the walkie-talkie.

[0038] As a further improvement of the present invention, the specific steps for installing the remaining ring beam skin plates and track beams are as follows:

[0039] (1) After the hoisting of the steel dome module is completed, first install the circumferential beams at the gap between the large and small modules. First install and weld the first circumferential beam at the large end, then install and weld the first circumferential beam at the small end, and the subsequent beams are assembled and welded in sequence from one side to the other side.

[0040] (2) After the installation and welding of the circumferential beams are completed, the installation of the track beams and skin plates can be carried out. First, weld the welds between the track beams and the track beam stiffeners, then weld the butt welds between the track beams. After the butt welds are welded, the butt joints of the traveling pulleys need to be ground flat. The skin plates are laid in sequence from the periphery to the center of the tank layer by layer, and after laying, they are welded by the method of segmental backward welding.

[0041] As a further improvement of the present invention, the specific steps for installing the stud attachment of the casing are as follows:

[0042] (1) After all the welds of the skin plates are welded, the casing can be installed. Use a total station to position the center point and radius of the casing inside the tank, and use gas cutting to punch holes at the center point of the casing on the back of the skin plate. To ensure the cutting size, install a reinforcement plate according to the center point of the casing, and then cut the skin plate according to the size of the inner hole of the reinforcement plate. After cutting, install the casing. The casing is made of steel plate cut and rolled on site and then welded. Before installation, a 10-mm blind plate needs to be installed on the casing, which needs to be removed after the pressure holding is completed, so a 50-mm allowance needs to be reserved for the casing to ensure that the length of the casing meets the requirements after cutting. For all pipes with flanges, a blind plate needs to be installed before installation to ensure that the casing and pipes do not leak air during the air pressure jacking. When welding the casing, the reinforcement plate needs to be lifted to ensure the welding quality so that the casing can be welded to the skin plate. After the casing is welded to the skin plate, the weld between the reinforcement plate and the casing can be welded. According to the drawing requirements, an airtight test needs to be carried out on the weld of the reinforcement plate, and after passing the inspection, the signal hole is sealed and welded.

[0043] (2) Mark the positions of the studs according to the drawing, and use a stud welder to weld the studs. Pay attention to the welding current and welding time during welding to avoid burning through the skin plate during stud welding. After the stud welding is completed, check the welding quality of each stud one by one, and use manual arc welding for repair welding if necessary.

[0044] As a further improvement of the present invention, the specific steps for removing the central and intermediate supports are as follows:

[0045] (1) After the skin plates and track beams are welded and the entire steel dome forms an integral whole, the central support and intermediate supports can be removed. Before removal, it is necessary to ensure that there is no connection between the edge supports and the radial beams, such as whether the stoppers and temporary welds are disengaged from the radial beams;

[0046] (2) Cut the angle iron connecting the central support and the central ring on the central support platform to disconnect the central support from the central ring; then cut 30 mm on each central support column and observe whether the steel dome descends. If the steel dome descends and the central ring is in contact with the central support column again, continue to cut 30 mm of the central support column until the central ring and the central support column are no longer in contact, and record the descent height of the central ring;

[0047] (3) After the central support is disengaged from the central ring, start removing the intermediate supports. The removal order of the intermediate supports follows the principle of removing every other one. First, remove half of them, then check whether the central ring descends and check whether there is any slippage between the tail ends of the radial beams and the edge supports. If the central ring descends and is already in contact with the central support column, continue to cut 30 mm of the central support column to completely disengage the central ring from the central support column. Finally, remove the remaining intermediate supports. At this time, the intermediate supports are under very large stress and may bend and deform, so safety should be noted. During the removal process, pay attention to observing whether there are any large abnormal noises in the steel dome;

[0048] (4) After the removal of the intermediate supports is completed, check the contact situation between the central support and the central ring again. If there is contact, continue to cut 30 mm of the central support column to completely disengage the central ring from the central support column. Then start removing the central support. First, remove the central support platform, then remove the inclined supports of the central support, and finally remove the central support. After the removal work is completed, the removed parts are centrally transported to a designated location outside the tank.

[0049] The beneficial effects of the present invention are as follows:

[0050] 1. The Tekla software 1:1 model lofting steel dome prefabrication frame is adopted, which can accurately control the camber of the prefabrication frame, avoid the problem of gaps between beams during installation, ensure the stress-free assembly of the beams, and reduce the deformation of the dome;

[0051] 2. The division of the dome module units and the design of the hoisting point positions are reasonable, and the stress is uniform during the later hoisting, which is beneficial to maintaining the camber of the module;

[0052] 3. Modular prefabrication and installation offer significant schedule benefits for large domes with a construction period of at least half a year. At the same time, deep prefabrication can minimize the interference between the two working surfaces of steel dome installation and outer tank wall casting, reducing the high-altitude work of in-tank assembly.

[0053] 4. After the dome module is in place, the camber can be finely adjusted through adjustable intermediate supports at the centroid position, avoiding the reduction of camber caused by the settlement of the centroid part of the dome.

[0054] 5. After the overall welding of the dome is completed, the center support is cut in batches and the intermediate supports are removed in batches, causing the dome to slowly fall back, and the weld stress is slowly released, effectively avoiding tearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flowchart of the present invention.

[0056] Figure 2 This is a steel dome module division diagram of a certain storage tank project in the embodiment of the present invention.

[0057] Figure 3 This is a lofting diagram of the Tekla software 3D model in the embodiment of the present invention.

[0058] Figure 4 This is a plan layout diagram of three sets of steel dome prefabrication frames in the embodiment of the present invention.

[0059] Figure 5 This is a top view of a steel dome prefabrication frame in the embodiment of the present invention.

[0060] Figure 6 This is a front view of a steel dome prefabrication frame in the embodiment of the present invention.

[0061] Figure 7 This is a schematic elevation view of the steel dome prefabrication frame in the embodiment of the present invention.

[0062] Figure 8 This is Figure 7 an enlarged view of A in

[0063] LIST OF REFERENCE NUMERALS:

[0064] 1 - Edge support, 2 - Intermediate support, 3 - Center support platform, 4 - Base, 5 - Jack. DETAILED DESCRIPTION OF THE INVENTION

[0065] The present invention will be further illustrated below in conjunction with the drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0066] In the present invention, by reasonably dividing precast units, according to the distribution of radial and circumferential beams of the steel dome, comprehensively considering the stress of the lifting points and the configuration of on-site lifting machinery, the dome is divided into two types of modules with appropriate sizes. The modules are assembled symmetrically in the radial direction, and a "unit gap" should be reserved between the two types of modules. Later, the large and small modules are connected into a whole. Starting from ensuring and maintaining the camber during the prefabrication and installation process of the dome, a solution is formulated using Tekla software. Since the steel dome is spherical in shape, the height and position of each column are different. In this construction method, 1:1 lofting is carried out on the 3D model of Tekla software, and cutting is performed according to the actual dimensions after lofting to accurately control the camber of the prefabricated arch, thereby ensuring the camber of the prefabricated module. Before the dome is hoisted, Tekla software is used to determine the center of gravity position and weld support lifting lugs. After the dome is hoisted in place, the lifting lugs are connected to the adjustable intermediate supports through bolts, and the support height is adjusted through jacks to control the camber, avoiding the reduction of the camber caused by the sinking of the center of gravity position of the dome. After the steel dome is welded, when the central support and the intermediate supports are removed, the central ring will drop by about 100 mm. To avoid tearing of the steel structure welds of the dome, a demolition process of cutting the central support in stages, removing every other intermediate support, and alternating the two is implemented. That is, first cut the welding point between the central support and the central ring, then cut 30 mm of the central support column. After the central ring and the central support are suspended and have no contact, start removing the intermediate supports, removing every other one. Then, check the descent of the central ring again. If the central ring contacts the central support column, continue to cut 30 mm of the central support column. After the central ring and the central support are suspended and have no contact, continue to remove every other one to remove the remaining intermediate supports. After all the intermediate supports are removed, if the central ring still contacts the central support column, follow the above steps and continue to cut 30 mm until the central ring and the central support column have no contact, and then remove the central support column to end the in-tank assembly of the dome. Embodiment

[0067] As Figure 1 shown, a construction method for the fabrication and installation of the outer tank steel dome of a large cryogenic storage tank includes the following steps: layout of the prefabrication frame site, design and fabrication of the prefabrication frame, prefabrication, welding and forming of the steel dome beam plates, transfer of the dome modules, installation of the central and edge supports, installation of the intermediate supports and hoisting of the dome modules in place, installation of the remaining ring beam skin plates and track beams, installation of the sleeve stud accessories, and removal of the central and intermediate supports. For a 220,000 m³ steel dome of a storage tank project in Binhai, Jiangsu, with a radius of 88 m, the dome is divided into 12 large and small modules each and 1 central ring, as Figure 2 shown.

[0068] In this embodiment, the specific steps for the layout of the prefabrication frame site are as follows:

[0069] (1) Arrange the prefabrication frame site around the storage tank to reduce the walking distance of the crawler crane, but avoid the rotation radius of the tower crane and the walking route of the crawler crane;

[0070] (2) The size of the prefabrication site is determined according to the site conditions and prefabrication requirements, and is set to meet the simultaneous construction of three sets of prefabrication frames. The dome module prefabrication adopts the simultaneous construction of three sets of prefabrication frames, which is convenient for the prefabrication work to achieve assembly line operation according to beam assembly, beam welding, and skin plate welding, reducing costs.

[0071] (3) The ground of the prefabrication frame site should be flat, solid, and clean, and drainage measures should be taken to prevent site settlement. Taking a 220,000 m³ low-temperature storage tank project in Binhai, Jiangsu as an example, after the prefabrication site is leveled and compacted, 50 mm thick gravel is laid, and 100 mm thick plain concrete is poured for leveling.

[0072] In this embodiment, the prefabrication frame is composed of a bottom support, support columns, diagonal supports, and an upper support, and is in a fan-shaped structure as a whole. The specific steps for the design and manufacture of the prefabrication frame are as follows:

[0073] (1) Lofting with a Tekla software 3D model; Since the steel dome is a spherical curved shape, it is necessary to loft at a 1:1 scale with a 3D model to determine the height and spacing of the support columns of the prefabrication frame. The principle of the prefabrication frame is that according to the principle of vertical projection of light, the steel dome structure of the spherical surface is projected onto a horizontal plane, and a frame projection is obtained on the horizontal plane. The figure obtained from this projection is the position structure of the prefabrication frame, and appropriate points are selected as the support points of the steel dome. The principle of the support points is to be as close as possible to the intersection of the main beam and the ring beam, but it cannot interfere with the installation and welding operation of the ring beam during construction, nor can it affect the welding of the butt joint of the radial beam and the welding of the aluminum ceiling lifting lugs, and at least two support points are guaranteed for each section of the radial beam. The number of support points of the prefabrication frame depends on the size of the storage tank. There are 52 large modules for a 220,000 m³ low-temperature storage tank project in Binhai, Jiangsu. After the support points are selected, the height from each support point to the ground is measured in the software according to the curved surface height of the steel dome, which is the height of the support column of the prefabrication frame. As Figure 3 。

[0074] (2) Fabrication and installation of the prefabrication frame; The support columns are set vertically, the bottom support is placed at the lower end of the support columns, and the upper ends of adjacent two support columns are connected by an upper support. The diagonal support is used for laying steel gangplanks; the bottom support adopts a 12*250*250 mm steel plate, the support columns adopt HW150*150*7*9 section steel, the upper support adopts 10# channel steel, and ∠80 angle steel is used as the diagonal support for laying steel gangplanks. The height of the steel gangplank from the end face of the support column is set at a position of 1.2 meters.

[0075] (3) Prefabricated frame placement: Three sets of prefabricated frames are used for placement. Considering the continuity of construction workers, two large prefabricated frames and one small prefabricated frame are used. The large prefabricated frame is placed close to the tank body to ensure that the crawler hoisting weight can meet the requirements. In order to save the floor space of the prefabricated frames, the large and small heads of the three sets of prefabricated frames are arranged in reverse order, such as Figure 4 , and the steel springboards of the three sets of prefabricated frames are on the same horizontal plane. When modeling in 3D, it is necessary to consider that the columns of the prefabricated frames are on the same axis as much as possible, and to ensure that the large and small end support columns are at the same height, such as Figure 5 and 6 , so as to ensure that the steel springboards are on the same horizontal plane, which is convenient and safe for construction. After the prefabricated frame is installed, use a level to mark the 1m line position on each column, measure the actual height of the column upward through the 1m line, and then adjust the height of the column according to the drawing size. Due to the possibility of subsidence of the concrete floor, the prefabricated frame should be re-tested regularly to check whether there is any settlement. Only after the re-test is qualified can the prefabrication of the next steel dome block be started.

[0076] In this embodiment, the specific steps of prefabrication and welding of the steel dome beams and slabs are as follows:

[0077] (1) Prefabrication: The steel dome is composed of H-shaped steel and skin panels. Since the tank dome is a spherical surface and the skin panels shrink in size during welding, the skin panels are rearranged according to the design drawings before cutting. The cutting dimensions of each skin panel are given, and the curvature and dimensions of the steel dome beams are inspected and accepted before cutting and beveling. Then, each steel section is numbered according to the drawings to avoid errors during installation. Among them, when the H-shaped steel is processed into radial beams and circumferential beams according to the radius of the steel dome using the hydraulic top bending process, if there is a deviation in the top bending, it can be checked on the curvature plate to ensure that the arch of the beam meets the requirements of the drawings;

[0078] (2) Assembly welding: First, place the prefabricated radial beams on the prefabricated frame, adjust the size and fix them with a clamp. After the radial beams are welded, install the annular beams. Check the size of the entire steel dome and the gap of the butt joint. Only after they are qualified can the welding work of the annular beams and radial beams be carried out.

[0079] (3) Forming: After the steel dome beams are welded, the skin panels are laid. The skin panels are laid piece by piece and layer by layer from the edge of the dome to the center. Only spot welding can be done during laying. After the entire skin panel is laid, it can be fully welded with the beam. The weld bead should be cleaned before welding the skin panel. The overhead weld between the plate and the beam should be welded first. After the overhead weld is completed, the short welds of the adjacent plates are welded, and finally the long welds are welded. The long welds are welded in sections along the same direction to reduce deformation.

[0080] In this embodiment, the dome module transfer is to transfer the formed steel dome to the storage rack around the storage tank, and the specific steps are as follows:

[0081] (1) Select a suitable lifting machine according to the weight and size of the steel dome for the transfer operation of the steel dome module;

[0082] (2) Determine the hoisting point layout with the assistance of Tekla software. Taking a 220,000 m³ cryogenic storage tank project in Binhai, Jiangsu as an example, the large steel dome module weighs 28.3 tons and 6 hoisting points are set, with the two middle hoisting points set at the center of gravity position. The small steel dome module weighs 14.7 tons and 4 hoisting points are set. During hoisting, two 10t manual chain hoists are used at each of the large end and small end of the steel dome to adjust the steel dome module to keep it in a horizontal state. Three traction ropes need to be set during the displacement of the steel dome module to ensure the stability of the steel dome block during the transfer process.

[0083] In this embodiment, the central and edge supports are installed to support the small end and large end of the steel dome module through the central support and edge support respectively, specifically including the central support installation and the edge support installation. Among them,

[0084] I. The specific steps of the central support installation are as follows:

[0085] (1) Calculate the height of the central support according to the bottom elevation of the aluminum ceiling and the spherical radius of the steel dome. The outer diameter formed by the central support columns must match the outer diameter of the central ring, and the installation verticality shall not be greater than 1 / 1000 mm. The central support columns adopt 6 Ø273*10 seamless steel pipes;

[0086] (2) Install the central support platform at the center position of the storage tank. The central support columns are welded to the embedded parts of the bearing platform. To reinforce the central support, ∠75*6 angle steel and [18 channel steel are used to weld the scissors bracing for reinforcement. To prevent the central support from tipping over due to uneven loads, each central support column is reinforced with Ø159*8 steel pipe diagonal bracing;

[0087] (3) After the central support platform is installed, weld the guiding plates of the central ring on the platform columns, and mark the azimuth angle in advance on the central ring platform. Then use a tower crane to hoist and place the steel dome central ring in place;

[0088] II. The specific steps of the edge support installation are as follows:

[0089] (1) Calculate the height of the edge support according to the bottom elevation of the ceiling and the spherical radius of the steel dome. The edge support adopts Ø219*8 steel pipe, and a steel plate with a width 100 mm greater than the diameter of the steel pipe and a length 100 mm longer than the radial beam web is welded on the steel pipe. Positioning baffles are welded on the steel plate to facilitate the adjustment of the radial beam azimuth;

[0090] (2) After the formwork is lifted to the third - layer wall, the edge supports can be connected and welded with angle steel on the first - circle vertical and circumferential embedded parts on the inner side of the concrete outer tank wall. The position of the vertical embedded part welded to the angle steel is generally at 3 / 4 of the edge - support column. Since there are no vertical embedded parts at the large and small door openings, the edge supports at the large and small door openings need to be reinforced with diagonal braces made of angle steel on the first - circle circumferential embedded parts.

[0091] In this embodiment, the specific steps for installing the intermediate supports and hoisting the dome module into place are as follows:

[0092] (1) Since the span of the steel dome module is very large, after the steel dome is in place, the camber of the center - of - gravity position will sink. The supports at this part need to be designed as adjustable - height movable supports to adjust the camber of the steel dome to meet the design requirements.

[0093] (2) The intermediate supports use Ø159*8 steel pipes. Steel plates with a thickness of δ10*200*200 are welded at both ends of the steel pipes. Two lifting lug plates are welded on the upper steel plate, and the distance between the two lifting lug plates is 25 mm (the thickness of the lifting lug plates in the middle of the dome is 20 mm). The lengths of all intermediate supports need to be kept the same (for convenient calculation of the camber). A support is made for each intermediate support, and the support is welded by [20 channel steel and steel plates. The height of the support is generally about 500 mm, which is convenient for the operation of the jacks. At the same time, the strength of the support must be ensured. First, the steel dome module is shifted from the storage rack around the tank to the circumferential road around the storage tank and temporarily supported by the storage rack. The intermediate supports are connected to the pre - welded lifting lugs on the dome module with bolts. At the same time, safety protection railings are welded on both sides of the skin plate of the large - block steel dome module and life ropes are installed, and then it is hoisted as a whole. In the 220,000 m³ cryogenic storage tank project of Jiangsu Binhai LNG Storage, 3 intermediate supports are installed for the large steel dome module and 2 intermediate supports are installed for the small steel dome module.

[0094] (3) After the concrete wall of the fourth layer of the outer tank is poured, the steel dome is hoisted.

[0095] a) Since the wire ropes used when installing the intermediate supports are the wire ropes for shifting, the wire ropes for hoisting must be replaced when the dome module is hoisted into place. The angle of the steel dome module is finely adjusted by the chain hoists set at the large and small ends of the wire rope. After the hoisting angle of the steel dome module is basically consistent with the installation angle, the small end is slightly higher than the theoretical height by about 300 mm.

[0096] b) Slowly lift the hook of the crane at a speed of about 400 mm / min, and observe the settlement of the foundation and the load-bearing condition of the sling. Try to lift the height to about 300 mm above the ground, and keep it stationary for 3 minutes. If there is no abnormal situation, the hoisting can be continued; otherwise, the hoisting operation should be stopped immediately. When hoisting, three traction ropes need to be set for the steel dome module to tow the steel dome module. Lower the hook slowly. First, let the large end be positioned on the edge support. Install two limit blocks on the edge support in advance, and then slowly lower the hook to position the small end of the steel dome on the central ring.

[0097] c) After the steel dome is hoisted and positioned, calculate the theoretical height of the center of gravity through software, compare it with a level and a reference line, and adjust the intermediate support with a 30t jack. Figure 7 and 8 , after it meets the calculated theoretical support height, weld the stop block to fix it, and then the main crane can be unhooked and detached from the lifting lug.

[0098] 4) During the hoisting operation, a commander stands on the formwork platform of the concrete outer tank to mainly observe the distance between the steel dome module and the inner platform of the concrete outer tank formwork. After the steel dome module descends to a certain position, observe the landing situation of the steel dome module, and communicate with the chief hoisting commander by walkie-talkie. Another observer and communicator is arranged beside the operating room on the crane to prevent accidents of the walkie-talkie and can also timely transmit the command information to the crane driver.

[0099] In this embodiment, the specific steps for installing the remaining ring beam skin plates and track beams are as follows:

[0100] (1) After the hoisting of the steel dome module is completed, first install the circumferential beam at the gap between the large and small modules. First, install and weld the first circumferential beam at the large end, then install and weld the first circumferential beam at the small end, and the subsequent beams are assembled and welded in sequence from one side to the other side.

[0101] (2) After the installation and welding of the circumferential beam are completed, the installation of the track beam and the skin plate can be carried out. First, weld the weld between the track beam and the track beam stiffener plate, then weld the butt weld between the track beams. After the butt weld is welded, the butt joint of the traveling pulley needs to be ground flat. The skin plates are laid in the order from the periphery to the center of the tank layer by layer, and after laying, they are welded by the method of segmental back welding.

[0102] In this embodiment, the specific steps for installing the sleeve stud accessories are as follows:

[0103] (1)After all the welds of the skin plates are completed, the casing can be installed. Use a total station to position the center point and radius of the casing inside the tank. Use gas cutting to punch holes at the center point of the casing on the back of the skin plate. To ensure the cutting size, install a reinforcement plate according to the center point of the casing, and then cut the skin plate according to the size of the inner hole of the reinforcement plate. After cutting, install the casing. The casing is made of steel plate cut and rolled on site and then welded. Before installation, a 10mm blind plate needs to be installed on the casing, which needs to be removed after the pressure holding is completed. Therefore, a 50mm allowance needs to be reserved for the casing so that the length of the casing meets the requirements after cutting. For all pipes with flanges, a blind plate needs to be installed before installation to ensure that there is no air leakage between the casing and the pipe during the air pressure jacking. When welding the casing, to ensure the welding quality, the reinforcement plate needs to be lifted so that the casing can be welded to the skin plate. After the casing is welded to the skin plate, the weld between the reinforcement plate and the casing can be welded. According to the drawing requirements, an airtight test needs to be carried out on the weld of the reinforcement plate, and after passing the inspection, the signal hole is sealed and welded;

[0104] (2)Mark the positions of the stud bolts according to the drawing and use a stud welder for stud welding. Pay attention to the welding current and welding time during welding to avoid burning through the skin plate during stud welding. After stud welding is completed, check the welding quality of each stud one by one. For those that need to be repaired, manual arc welding is used for repair welding.

[0105] In this embodiment, the specific steps for removing the center and intermediate supports are as follows:

[0106] (1)After the skin plate and the track beam are welded and the entire steel dome forms an integral body, the center support and the intermediate support can be removed. Before removal, it is necessary to ensure that there is no connection between the edge support and the radial beam, such as whether the stoppers and temporary welds are separated from the radial beam;

[0107] (2)Cut the angle iron connecting the center support and the center ring on the center support platform to make the center support and the center ring have no connection; then cut 30mm on each center support column and observe whether the steel dome drops. If the steel dome drops and the center ring is in contact with the center support column again, continue to cut 30mm of the center support column until the center ring and the center support column are no longer in contact, and record the drop height of the center ring;

[0108] (3)After the center support is separated from the center ring, start removing the intermediate support. The removal order of the intermediate support follows the principle of removing one every other one. First, remove half of them, and then check whether the center ring drops and whether there is any slip between the tail end of the radial beam and the edge support. If the center ring drops and is in contact with the center support column, continue to cut 30mm of the center support column to completely separate the center ring from the center support column. Finally, remove the remaining intermediate supports. At this time, the intermediate supports are under great stress and may bend and deform, so pay attention to safety. During the removal process, pay attention to observing whether there are any large abnormal noises in the steel dome;

[0109] After the removal of the intermediate support is completed, check the contact between the central support and the central ring again. If there is contact, continue to cut the central support column by 30 mm to completely separate the central ring from the central support column. Then start to remove the central support. First, remove the central support platform, then remove the inclined support of the central support, and finally remove the central support. After the removal work is completed, the removed parts are centrally transported to the designated location outside the tank.

[0110] For the main equipment and materials required by the present invention, see Table 1.

[0111] Table 1 List of Construction Materials and Tools

[0112]

[0113] The quality control based on the present invention is as follows:

[0114] I. Quality Control Basis

[0115] EN14620.2 - 2006 "Vertical Flat - Bottom Cylindrical Tanks under Low - Temperature Working Conditions - Part 2 - Design and Construction Codes for Single - Containment, Double - Containment and Full - Containment Metal Tanks for Liquefied Gases with a Storage Minimum Temperature of - 165 °C; SH / T3561 - 2017 "Technical Specification for Welding of Full - Containment Steel Inner Tanks of Liquefied Natural Gas (LNG) Tanks"; ISO - 5817 - 2014 "Welding - Quality Levels for Imperfections in Fusion Welded Joints of Steels, Nickel, Titanium and Their Alloys"; Design drawings and technical specifications issued by the design unit; Inspection and test plan.

[0116] II. Quality Control for Prefabrication of Dome Modules

[0117] 1. The cutting size of the template must be re - checked to ensure that the template size meets the requirements of the drawings.

[0118] 2. After the prefabrication rack is made, the overall dimensions of the jig should be re - checked by a total station.

[0119] 3. After the dome beam is bent and formed, it should be checked with an arc template not less than 2000 mm, and the gap should not be greater than 2 mm; the deviation of the bending rise should not exceed L / 1000 of the component length and should not be greater than 5 mm; after the splicing of the dome beam extension is completed, the deviation of the bending rise should not exceed L / 1000 and should not be greater than 10 mm.

[0120] 4. When there are no requirements in the design documents, the splicing length of the flange plate of the dome beam shall not be less than 2 times the plate width, the splicing length of the web shall not be less than 600 mm, and the spacing between the splicing welds of the flange plate and the web, and between the flange plates shall not be less than 200 mm. The misalignment of the welded joint in the thickness direction shall not be greater than 1 / 10 of the plate thickness and not greater than 1 mm, and in the width direction, the misalignment of the web shall not be greater than 1 mm, and the misalignment of the flange plate shall not be greater than 2 mm.

[0121] 5. The allowable deviation of the perpendicularity of the H-beam flange to the web is L / 100 (L is the width of the flange), and not greater than 2.0 mm.

[0122] 6. The assembly dimensions of the dome module shall consider the welding shrinkage, and a 20-mm allowance shall be reserved for the radial beam size.

[0123] 7. When the welding groove is processed by flame cutting, the allowable deviation of the flatness of the cutting surface is 0.05t and not greater than 2.0 mm, the groove angle is ±5°, and the root face is ±1 mm.

[0124] 8. After welding, the overall dimensions of the dome module shall be inspected to ensure that the dimensions before installation meet the requirements of the drawings.

[0125] III. Quality Control of the Prefabrication and Installation of the Central Ring

[0126] 1. Before cutting the central ring, the scribing shall be rechecked, and after prefabrication, the relative elevation difference between the inner and outer rings of the central ring shall be rechecked by a total station.

[0127] 2. Before installing the central ring, measure the platform elevation to make the bottom elevation of the central ring consistent with the upper elevation of the platform. Mark the azimuth lines on the platform and the bottom plate of the central ring respectively, and ensure that the two lines can coincide during installation to ensure the accuracy of the installation azimuth of the central ring.

[0128] 3. After assembling the central ring, the radial length deviation shall not exceed 20 mm, and the spacing deviation of the circumferential beams shall not exceed 3 mm.

[0129] 4. The allowable deviation of the installation center point of the central ring is 5 mm, and the allowable deviation of the levelness is 3 mm.

[0130] IV. Quality Control of the Installation of the Dome Module

[0131] 1. The edge supports shall be installed directly below the radial beams, and the elevation deviation of the top surfaces of any two edge supports shall not be greater than 10 mm;

[0132] 2. After installing the large and small modules, measure the actual dimensions of the installation position of the circumferential beam between the large and small modules, and adjust the circumferential beam according to the actual dimensions to ensure the installation accuracy.

[0133] 3. The deflection value after the installation of the dome module shall not exceed the designed deflection value, and its measurement method is to measure symmetrically in 8 directions at the center of the tank top and at 1 / 2 of the tank radius direction.

[0134] 4. Adjust the intermediate support through the jack and use the level to level it, so as to control the sinking of the dome module.

[0135] 5. The allowable deviation of the geometric dimensions of each part of the assembled dome module shall meet the requirements of Table 2.

[0136] Table 2 Allowable Deviation of Dimensions after Assembly of Dome Module

[0137]

[0138] V. Welding Quality Control

[0139] 1. Before welding all welds, it is necessary to grind to a metallic luster.

[0140] 2. After the longitudinal beam is welded, the weld needs to be ground flush with the base metal.

[0141] 3. The welding of the arch roof plate is strictly carried out from the large end to the small end, and during the welding process, it should be welded in sections and layered and channeled.

[0142] 4. During welding, strictly control the welding parameters and strictly implement the requirements of the welding process instruction book for welding.

[0143] The safety measures of the present invention are as follows:

[0144] 1. Before construction, organize all construction personnel to conduct safety technical disclosure and study of safety rules and regulations, carry out pre-shift meetings and hazard prediction activities and make records. Clearly define the working scope and potential safety hazards in cross-operation, and improve the safety awareness and self-protection ability of construction personnel.

[0145] 2. Special equipment such as construction lifting machinery, tower cranes, electric hoists, etc. should be inspected and qualified to ensure good condition.

[0146] 3. For temporary electricity use, set up three-level distribution boxes, implement the safety configuration of one machine, one switch, one leakage protector and one protection, and try to lay the temporary cable along the beams and columns. Adopt sleeve protection measures at key points. At the same time, arrange professional electricians to conduct inspections every day after work to ensure electricity safety and prevent leakage and electric shock accidents.

[0147] 4. The installation process of the dome module is high-altitude operation, and life ropes are separately set up on both sides of the dome module. Before the dome module is hoisted and shifted, it is necessary to check that the rigging and clamps are in good condition, and set up eye-catching warning line signs in the entire operation area. Construction personnel use five-point seat belts, and the hooks are always hung on the life ropes. Set up a special person to command and a special person to monitor, and the signals are clear and accurate to prevent non-construction personnel from straying in.

[0148] 5. On-site construction personnel shall wear work shoes and safety helmets as required. When performing mechanical cutting or welding, they must wear protective face shields.

[0149] 6. For cross-operation, a clear pre-operation briefing shall be conducted in advance. Each worker on the operation floor shall keep his tools properly. The parts and components shall be concentrated in a safe area or stored in wooden boxes for easy access, so as to prevent falling objects from height. After work, construction debris shall be cleared up.

[0150] 7. Dry powder fire extinguishers shall be configured in areas such as the storerooms and material yards at the construction site to take fire prevention measures.

[0151] The environmental protection measures of the present invention are as follows:

[0152] 1. The roads at the construction site shall be hardened and frequently sprinkled on sunny days to prevent dust. For areas where sprinkling is not applicable, enclosing, covering or other measures shall be taken to ensure that dust pollution complies with environmental protection regulations.

[0153] 2. All kinds of materials at the site shall be stored according to specifications, brands, batches and regulatory requirements, and clearly marked in accordance with the material management procedures to make them orderly and clearly visible.

[0154] 3. Construction waste shall not be randomly discarded, but shall be centrally recycled, classified and stacked for unified treatment. Ensure that the site is cleared after work and keep the construction site clean and tidy.

[0155] 4. The remaining paint in the anti-corrosion operation shall be promptly cleaned and stored in the warehouse, and shall not be randomly dumped or discarded.

[0156] 5. Timely conduct daily maintenance of equipment to keep mechanical equipment in good condition and reduce pollution such as oil leakage and noise.

[0157] The benefit analysis of the present invention is as follows:

[0158] 1. Economic benefits

[0159] This construction method adopts modular prefabrication and installation. The prefabrication work adopts flow operation, with concentrated and efficient manpower, and no idling phenomenon will occur, which is conducive to reducing labor costs; deep prefabrication can minimize the mutual interference between the two operation surfaces of the steel dome installation and the outer tank wall pouring, reduce the high-altitude operation in the tank assembly, quickly complete the dome installation and enter the next process; compared with the in-tank assembly method, although the crane cost of this construction method has increased, the overall labor cost has been significantly reduced. Taking the Jiangsu Binhai LNG storage tank project as an example for analysis, as shown in Tables 10-1 and 10-2, the cost difference of the steel dome of a single 220,000 m³ storage tank is 375,100 yuan, and the construction period is relatively saved by 109 days.

[0160] Table 3 Statistical table of the cost of prefabricating the steel dome on the prefabrication jig

[0161]

[0162] Table 4 Statistical Table of Costs for the In - tank Splicing Method of Single - Root Radial Beams

[0163]

[0164] 2. Social Benefits

[0165] In China, the field of cryogenic storage tank design and construction started relatively late compared with foreign countries, and there is still a certain gap from developed countries. There are no relevant specifications for the design and construction of large - scale cryogenic storage tanks in China, and there is no unified standard during construction. This construction method optimizes the conventional manufacturing and installation process of steel domes. Compared with the previous manufacturing and installation processes, both the quality and efficiency have been greatly improved, enhancing the manufacturing and installation level of large - scale steel domes, which is of great significance for improving the safety of large - scale cryogenic storage tanks.

[0166] The application embodiments of the present invention are as follows:

[0167] 1. A liquefied natural gas receiving station project in Binhai, Jiangsu

[0168] The project is currently the cryogenic storage tank with the largest single - unit capacity in China. The overall goal of the project is to strive for the Gold Award of National High - Quality Project, with a contract value of 78.71 million yuan. From March to August 2020, this construction method was applied to complete the manufacturing and installation of the steel domes of two 220,000 m³ tanks, overcoming the adverse factors of tight construction period, high requirements, and frequent extreme weather in the coastal area, and ensuring the subsequent construction nodes to meet the standards.

[0169] 2. The construction and installation project of an ethane cryogenic tank area in Lianyungang (Section B)

[0170] The project contract value is 170 million yuan. This construction method was applied to the 160,000 m³ ethane cryogenic storage tank of this project from November 2018 to April 2019. Due to material supply problems in this project, the dome manufacturing time was 15 days behind schedule. Using this construction method, the lagging progress was made up, providing sufficient time for the subsequent casting and curing of the outer - tank concrete dome.

[0171] 3. The installation construction project of a distribution and transfer station in Nantong Port

[0172] The project contract value is 131 million yuan. This construction method was applied to the dome manufacturing and installation of this project from December 2016 to May 2017. The work efficiency of dome manufacturing and installation has been greatly improved, alleviating the problem of the subsequent construction period being compressed due to the lag of the previous civil engineering. The storage tank has been in use since June 2017 and its overall performance is good.

[0173] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A construction method for the fabrication and installation of the steel dome of the outer tank of a large-scale cryogenic storage tank, characterized in that, it includes the following steps: Prefabrication site layout, prefabrication frame design and fabrication, prefabrication and welding forming of the steel dome beam and slab, dome module transfer, installation of central and edge supports, installation of intermediate supports and hoisting and positioning of the dome module, installation of the remaining ring beam skin plates and track beams, installation of casing stud accessories, removal of central and intermediate supports; The prefabrication frame is composed of bottom supports, support columns, diagonal supports and upper supports, and is in a fan-shaped structure as a whole. The specific steps for the design and fabrication of the prefabrication frame are: (1) Tekla software 3D model lofting; lofting at a 1:1 scale through the 3D model to determine the height and spacing of the support columns of the prefabrication frame, and select appropriate points as the support points of the steel dome. After the support points are selected, measure the height from each support point to the ground in the software according to the curved surface height of the steel dome, which is the height of the support columns of the prefabrication frame; (2) Fabrication and installation of the prefabrication frame; the support columns are arranged vertically, the bottom supports are placed at the lower ends of the support columns, the upper ends of adjacent two support columns are connected by upper supports, and the diagonal supports are used for laying steel gangplanks; (3) Placement of the prefabrication frame; use three sets of prefabrication frames for placement, specifically two large prefabrication frames and one small prefabrication frame. The large prefabrication frames are arranged close to the tank body, the large and small ends of adjacent two prefabrication frames are swapped, and the steel gangplanks of the three sets of prefabrication frames are on the same horizontal plane; The specific steps for the installation of the intermediate supports and hoisting and positioning of the dome module are: (1) Design the support at the center of gravity position of the steel dome module as an adjustable-height movable support to adjust the camber of the steel dome to meet the design requirements; (2) The intermediate supports use steel pipes, with steel plates welded at both ends of the steel pipes, and two lifting lug plates are welded on the upper steel plates. The lengths of all the intermediate supports need to be kept the same, and a support is made for each intermediate support. First, shift the steel dome module from the storage rack around the tank to the circumferential road around the storage tank, temporarily support it with the storage rack, connect the intermediate supports with the lifting lugs pre-welded on the dome module with bolts, and at the same time weld safety protection railings and install life ropes on both sides of the skin plate of the large steel dome module, and then hoist it as a whole; (3) After the concrete wall of the fourth layer of the outer tank is poured, start hoisting the steel dome; The specific steps for the removal of the central and intermediate supports are: (1) After the skin plates and track beams are welded, the entire steel dome forms a whole, and the central support and intermediate supports can be removed; (2) Cut the angle iron connecting the central support and the central ring on the central support platform to make the central support and the central ring have no connection; (3) After the central support is separated from the central ring, start removing the intermediate supports; (4) After the removal of the intermediate supports is completed, check the contact situation between the central support and the central ring again. If there is contact, continue to cut the support columns of the central support until the central ring is completely separated from the support columns of the central support. Then start removing the central support. First, remove the central support platform, then remove the diagonal support of the central support, and finally remove the central support. After the removal work is completed, the removed parts are centrally transported to the designated location outside the tank.

2. A construction method for the fabrication and installation of the steel dome of the outer tank of a large-scale cryogenic storage tank according to claim 1, characterized in that, The specific steps of the prefabricated frame site layout are: (1) Arrange the prefabricated rack site around the storage tank; (2) The size of the prefabrication site is determined according to site conditions and prefabrication requirements, and is set up to accommodate the simultaneous construction of three sets of prefabrication racks; (3) The floor of the prefabricated frame site should be flat, solid and clean, and drainage measures should be taken to prevent site subsidence.

3. According to claim 1, a method for manufacturing and installing a steel dome for an outer tank of a large cryogenic storage tank, It is characterized in that The specific steps of prefabrication and welding of the steel dome beams and slabs are as follows: (1) Prefabrication: The steel dome is composed of H-shaped steel and skin panels. Before cutting the skin panels, they are re-arranged according to the design drawings. The cutting dimensions of each skin panel are given. The curvature and dimensions of the steel dome beams are inspected and accepted before cutting and beveling. (2) Assembly welding: First, place the prefabricated radial beams on the prefabricated frame, adjust the size and fix them with a clamp. After the radial beams are welded, install the annular beams. Check the size of the entire steel dome and the gap of the butt joint. Only after they are qualified can the welding work of the annular beams and radial beams be carried out. (3) Forming: After the steel dome beams are welded, the skin panels are laid. The skin panels are laid piece by piece and layer by layer from the edge of the dome to the center. Only spot welding can be performed during laying. After the entire skin panel is laid, the seam is pressed first, and then the overhead weld between the skin panel and the beam is welded. After the overhead weld is completed, the flat angle seam between the skin panel and the beam can be fully welded.

4. The method for manufacturing and installing the steel dome of the outer tank of a large cryogenic storage tank according to claim 1, It is characterized in that The dome module transfer is to transfer the formed steel dome to the storage rack around the storage tank, and the specific steps are as follows: (1) According to the weight and size of the steel dome, select appropriate lifting machinery to transfer the steel dome modules; (2) Tekla software is used to assist in determining the arrangement of lifting points. During lifting, adjustments are made to keep the steel dome module in a horizontal state and to keep the steel dome block stable during the transfer process.

5. The method for manufacturing and installing the steel dome of the outer tank of a large cryogenic storage tank according to claim 1, It is characterized in that The central and edge support installation is to support the small end and the large end of the steel dome module respectively through the central support and the edge support, which specifically includes the central support installation and the edge support installation, wherein:

1. The specific steps for installing the center support are: (1) Calculate the height of the center support according to the bottom elevation of the aluminum ceiling and the spherical radius of the steel dome. The outer diameter of the center support column must match the outer diameter of the center ring; (2) Install the central support platform at the center of the tank, and weld the central support column to the embedded parts of the base; (3) After the central support platform is installed, weld the guide plate of the central ring on the platform column, mark the azimuth angle on the central ring platform in advance, and then use a tower crane to hoist the steel dome central ring into place; 2. The specific steps for edge support installation are: (1) Calculate the height of the edge support based on the bottom elevation of the suspended ceiling and the spherical radius of the steel dome; (2) When the formwork is lifted to the third layer of the wall, angle steel can be used to connect the welded edge supports on the first circle of vertical and circumferential embedded parts on the inner side of the concrete outer tank wall.

6. A construction method for the fabrication and installation of the outer tank steel dome of a large-scale cryogenic storage tank according to claim 1, characterized in that, the specific steps for the installation of the remaining ring beam skin plates and track beams are as follows: (1) After the hoisting of the steel dome module is completed, first install the circumferential beams at the middle gap between the large and small modules. First, install and weld the first circumferential beam at the large end, then install and weld the first circumferential beam at the small end, and the subsequent beams are assembled and welded in sequence from one side to the other side; (2) After the installation and welding of the circumferential beams are completed, the installation work of the track beams and skin plates can be carried out. First, weld the welds between the track beams and the track beam stiffeners, then weld the butt welds between the track beams. After the butt welds are welded, the butt joints of the traveling pulleys need to be ground flat. The skin plates are laid in sequence from the periphery to the center of the tank layer by layer, and after laying, they are welded by the segmented backstep welding method.

7. A construction method for the fabrication and installation of the outer tank steel dome of a large-scale cryogenic storage tank according to claim 1, characterized in that, the specific steps for the installation of the sleeve stud attachments are as follows: (1) After all the welds of the skin plates are welded, the sleeves can be installed. After the sleeves are welded to the skin plates, the welds between the reinforcement plates and the sleeves can be welded. After inspection and qualification, the signal holes are sealed and welded; (2) Mark the positions of the studs according to the drawings, and use a stud welder to carry out stud welding.

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