Safety maintenance process for large ethylene tank at low temperature

Abstract

The application discloses a low-temperature ethylene large-scale storage tank safety maintenance process, wherein X-shaped supporting pieces are used to fix the inner tank and the outer tank together, synchronous movement of the inner tank and the outer tank is ensured, then a rising ring, a support and a stand are additionally arranged on the outer tank, a plurality of jacks are used to lift the support, the inner tank and the outer tank are synchronously lifted, after the inner tank and the outer tank are lifted to a certain height, a cushion block is additionally arranged and fixed on the stand, the stability and safety of the storage tank after being suspended are ensured, the structure is simple, the construction method is scientific and novel, the operation is convenient, the deformation amount is small, large lifting machines or electric hoists on racks are not needed in the whole process, the construction cost is low, and the stability and safety are high.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of storage tank maintenance, in particular to a low-temperature ethylene large-scale storage tank safety maintenance process. BACKGROUND

[0002] With the improvement of industry and economy, the demand for ethylene in light industry, textile, mechanical and electronic, automobile manufacturing and modern agriculture industries shows a trend of substantial growth, so the ethylene industry has developed rapidly. At present, the storage of ethylene adopts the advanced low-temperature storage tank process in the world, which has the advantages of large single tank storage capacity (normal storage capacity ≥20000m 3 ), safe operation. These storage tanks adopt double-layer structure, the outer tank is made of carbon steel material, the inner tank is made of stainless steel material, the inner tank bottom is paved with foam glass bricks, and the inner tank and the outer tank are filled with heat insulation and cold preservation materials. Because the storage tank is too heavy, the steel material under the outer tank will deform or crack due to insufficient strength after a long time, so the first section wall plate and the bottom plate under the outer tank need to be replaced. When replacing, the tank body and the tank bottom need to be cut and separated first, then the tank body is hoisted, the bottom plate is pulled out and replaced with a new one, and the first section wall plate under the outer tank is cut off and replaced with a new steel plate. However, there are several difficulties in the construction process:

[0003] 1. The tank bottom plate replacement and the first section wall plate replacement under the outer tank need to lift the entire inner and outer tank to a certain height. Because the storage tank is too large, it is too costly to call a crane of several hundred tons, and it takes too long to consider. If a lifting sling is used, a support rack needs to be built around the storage tank first, which is large in engineering quantity and high in cost.

[0004] 2. It is difficult to pull out, put in, weld and detect the welding quality of the edge plate of the inner and outer tank bottom plate.

[0005] 3. After the first section wall plate under the outer tank is removed, the ring weld joint between the second section wall plate and the first section wall plate is assembled. Due to the deviation of the wall plate cylinder ellipticity and the influence of internal stress, when the ring joint is assembled, the ring joint part will cause the angle to be too large, and the size deviation will be out of standard.

[0006] 4. Many chemical plants are generally built on the sea coast. After the storage tank is lifted, it is difficult to ensure that the tens of meters high storage tank will not sway after being lifted. There is a serious safety hazard. SUMMARY

[0007] To solve the above problems, the present application discloses a low-temperature ethylene large-scale storage tank safety maintenance process, which is scientific, novel, convenient, low in cost, small in deformation, short in construction time, good in stability and high in safety when the storage tank is suspended.

[0008] To achieve the above purpose, the technical scheme of the present application is as follows:

[0009] The low-temperature ethylene large-scale storage tank safety maintenance process comprises the following steps:

[0010] (1) remove the electrical, instrument, pipeline connected with the storage tank, remove the suspended ceiling and the cold insulation material in the annular space between the inner tank and the outer tank;

[0011] (2) open all the holes of the storage tank, and detect the combustible gas content in the confined space;

[0012] (3) add a ring of expansion ring on the outer side of the lower second section wall plate of the outer tank, and the installation position of the expansion ring is above the welding seam between the first section wall plate and the second section wall plate,

[0013] (4) install an operation platform on the outer side of the outer tank, and open a temporary construction door hole corresponding to the operation platform;

[0014] (5) install explosion-proof lighting in the inner tank, cut the welding seam between the edge plate and the middle plate of the inner tank with a grinder, and remove the cold insulation material at the bottom of the tank;

[0015] (6) connect the annular space between the inner tank and the outer tank into a whole by adding support members;

[0016] (7) evenly fix ≥20 supports on the expansion ring; a jack column and a cushion column are arranged below each support;

[0017] (8) install a hydraulic jack on each jack column, and the jack supports the support without moving, removes the anchoring belt of the outer tank, and cuts the wall plate of the outer tank bottom plate upward by 50mm;

[0018] (9) simultaneously press all the jacks upward by hand, drive the storage tank upward by the support, pause for 30 times for height statistics, and check whether the mechanical and the inner and outer tanks are abnormal, continue to lift after confirming that the lifting height is synchronized and there is no abnormality, when the stroke of the jack reaches 150mm, place 135mm cushion blocks at the cushion column and install bolts to connect the column and the cushion block into a whole, then lower the jack to make the cushion block bear the force, remove the jack, install a 135mm bracket below the jack, and rise by 135mm according to the above method, and the cycle is repeated, when the lifting height of the storage tank reaches 405mm, ensure that each cushion column supports the storage tank, and meanwhile, four supports are placed below the inner tank wall plate;

[0019] (10) after the storage tank is stable, reinforce it, remove the ring beam, cut the outer tank bottom plate, clean the foundation, and lay a line to prepare to install the outer tank bottom plate, in order to reduce the period of lifting the storage tank, concentrate on installing the edge plate, after the edge plate RT and PT detection are free of defects and the vacuum box test is qualified, first carry out the tank bottom concrete leveling layer and cold insulation work at the ring beam, and then install the ring beam, so as to make the storage tank in place as soon as possible; when the cold insulation work and the ring beam installation work are carried out at the edge plate,

[0020] (11) After the cold insulation work at the ring beam and the installation of the ring beam and the installation of the outer tank wall plate are completed, the bottom plate edge plate installation and welding at the inner tank construction door hole are carried out, and 100% RT and PT detection are carried out and qualified;

[0021] (12) The storage tank is reset, and the process of resetting is the reverse operation of the lifting method described in step (9). When the first section of the wall plate and the second section of the wall plate are aligned, stop lowering, then weld the ring seam of the wall plate, adjust the perpendicularity of the wall plate, the wall plate geometry detection is qualified, and the wall plate longitudinal ring seam nondestructive testing is qualified, then weld the anchor belt, after welding is completed, remove all columns and supports;

[0022] (13) After the storage tank is in place, the middle plate installation of the outer tank is carried out, after the penetration detection and vacuum box test of the bottom plate weld are qualified, the remaining center area cold insulation work is carried out, and the middle plate installation of the inner tank bottom plate is carried out after the cold insulation work is completed. Control the deformation of the bottom plate when welding the middle plate, and carry out penetration detection and vacuum test of the bottom plate;

[0023] (14) Ceiling edge cover plate modification construction, installation of all accessories and supporting brackets of the inner tank and the outer tank; after the completion of all work of the inner tank, the inner tank door is sealed, and the static grounding is installed; after the completion of all work of the inner tank, the water pressure test is carried out, and after the completion of all work of the outer tank, the outer tank door is sealed for air tightness test;

[0024] (15) After the test is completed, the inner tank is cleaned, and after the remaining cold insulation work and the outer tank painting are completed, the tank is sealed, the storage tank drying and nitrogen replacement work are carried out, and the pre-cooling start-up guidance work of the storage tank is carried out. The entire overhaul work is completed.

[0025] As a supplement of the present application, the door hole size in step (4) is 4715mm*2825mm.

[0026] As a supplement of the present application, the support in step (6) has 4-8 groups, each group of support is fixed between the inner tank and the outer tank in X shape, and the support point is at the same position as the outer side of the expansion ring.

[0027] As a supplement of the present application, the support in step (7) includes a rib plate and a stress plate, the expansion ring is fixed horizontally around the outer tank, the rib plate is fixed vertically outside the expansion ring, and the stress plate is fixed horizontally between the expansion ring and the lower plane of the rib plate.

[0028] As a supplement of the present application, the number of rib plates is two, respectively corresponding to the axis of the jack column and the cushion block column.

[0029] As a supplement of the present application, the cushion block in step (9) is a square frame structure; the cushion block and the cushion block column are connected through bolts.

[0030] As a supplement of the present application, the bracket in step (9) is the same as the cushion block.

[0031] As a supplement of the present application, the reinforcement after the stabilization of the storage tank in step (10) is provided with a diagonal brace outside the jack column and the cushion block column, and the connection between the diagonal brace and the ground is provided with an expansion bolt and a pre-buried plate.

[0032] As a supplement of the present application, the jack column and the cushion block column are made of H-shaped steel.

[0033] As a supplement of the present application, the number of the anchoring belts in step (12) is greater than or equal to 70, and the anchoring belts are fixedly connected with the pile cap below the tank body.

[0034] The present application has the following beneficial effects:

[0035] (1) The X-shaped supporting member is used to fix the inner tank and the outer tank together, so that the inner tank and the outer tank will not be displaced and the synchronous movement of the inner tank and the outer tank is ensured.

[0036] (2) The outer tank is provided with a rising ring and a support, a plurality of jacks are used to lift the support, the inner tank and the outer tank are lifted synchronously, the cushion block is installed and fixed on the column after the lifting to a certain height, and the stability and safety of the storage tank after being suspended are ensured.

[0037] (3) The large lifting machine or the electric hoist with a rack is not needed, the structure is simple, and the construction cost is low. DETAILED DESCRIPTION

[0038] Figure 1 The figure is a schematic diagram of the installation of the rising ring.

[0039] Figure 2 The figure is a schematic diagram of the installation of the support.

[0040] Figure 3 The figure is a schematic diagram of the cushion block.

[0041] Figure 4 The figure is a schematic diagram of the connection of the inner tank wall plate and the outer tank wall plate.

[0042] Figure 5 The figure is a schematic diagram of the temporary operation platform.

[0043] Figure 6 The figure is a schematic diagram of the diagonal brace.

[0044] Figure 7 The figure is a schematic diagram of the installation of the first section wall plate below the outer tank. EMBODIMENT

[0045] The present application will be further clarified by the following description and examples with reference to the accompanying drawings and specific embodiments, which should be understood to be only illustrative of the present application and not limiting the scope of the present application.

[0046] Take the VCM TK-601 ethylene tank maintenance of XX Chemical Plant as an example, the maintenance content includes: ethylene tank bottom cold insulation material removal, inner and outer tank bottom plate and the first circle wall plate replacement, tank pipe and other accessories modification, hydraulic test, air tightness test and other maintenance work.

[0047] The storage tank to be maintained is a double-layer metal 20000m³ low-temperature ethylene tank, the outer tank has a diameter of 30 meters, the inner tank has a diameter of 28 meters, and the total height of the tank is 37.589 meters. The original outer tank bottom plate edge plate is Q345R steel plate with a thickness of 12mm, the middle plate is Q345R steel plate with a thickness of 6mm, and now it is replaced by 304 stainless steel plate with the same thickness; the original outer tank last section wall plate is Q345R steel plate with a thickness of 14mm and a height of 2970mm, and now it is replaced by 304 stainless steel plate with a thickness of 18mm and a height of 2825mm (30mm above the original weld is cut off the weld heat affected zone when cutting the wall plate); the inner tank middle plate material is unchanged, with A553 Type1 material and a thickness of 6mm.

[0048] The specific removal and recovery process is as follows:

[0049] Construction preparation → circle expansion, support, bracket and column installation → inner and outer tank door opening reinforcement → opening of inner and outer tank construction door → tank accessory removal → tank external accessory removal → inner tank bottom plate middle plate removal → tank bottom center area glass brick removal → inner and outer tank connecting rod device installation → outer tank wall and bottom plate fillet weld cutting → jack in place lifting of storage tank → tank bottom edge area ring beam and cold insulation removal → outer tank edge plate replacement → tank wall cutting → tank wall hoisting → wall plate assembly, welding → tank bottom edge area ring beam and cold insulation installation → inner tank bottom edge plate installation → tank overall lowering → wall plate non-destructive testing → outer tank bottom plate middle plate replacement → inner tank cold insulation brick laying → inner tank bottom plate installation → tank inner and outer accessory recovery → ceiling edge cover plate modification → inspection and acceptance → water pressure and air tightness test → tank wall and ceiling cold insulation material installation → nitrogen replacement → pre-cooling → overall acceptance.

[0050] Specifically, the following steps are included:

[0051] 1. Remove the electrical, instrument, pipeline connected to the storage tank, remove the ceiling insulation material and the perlite and elastic felt insulation material in the annular space;

[0052] 2. After the removal work is completed, all the holes that can be opened of the storage tank are opened, and the limited space is detected for combustible gas;

[0053] 3. Add a circle of [25a circle expansion (the circle expansion installation position is 400mm above the first weld)] to the outside of the second section of the outer tank wall plate, as shown inFigure 1 As shown, prevent the wall deformation when replacing the wall. The ring weld support position full welding, weld leg height is not less than 7mm; the rest of the interval welding, welding 100mm interval 200mm weld leg height is not less than 7mm.

[0054] 4、[25a ring reinforcement, installation of temporary construction door hole operation platform (operation platform using HN300*150 H-shaped steel production, platform plate for 8mm thick steel plate production, column using seamless steel pipe Φ273*6), such as Figure 5 As shown, the inner and outer tank door hole using profile reinforcement, inner and outer tank wall plate for opening temporary construction door hole; the size of the outer tank construction door is 4715mm*2825mm, before opening the door hole using channel steel [25a reinforcement, Hw200*200*8*12 column support, the inner tank construction door hole and the outer tank construction door hole position (angle) is the same, the size of the door hole is 4399mm*3070mm, before opening the door hole using channel steel [25a reinforcement, column using I-beam 25 support, the door hole height is 3070mm, to ensure that the forklift in and out of the transport plate without problem.

[0055] 5、inner tank installation anti-explosion lighting, the inner tank edge plate and the middle plate of ethylene low temperature tank are cut by grinding machine, the excess height of the welding position is polished to be flush with the base material, the heat affected zone of the original welding position is considered, the size of the middle plate is enlarged when installing the middle plate to cover the original weld; the middle plate is cut using plasma cutting (according to the design size, the original middle plate is cut down), and the outer tank bottom cold preservation material (sand, glass brick, ring beam) is removed.

[0056] 6、inner and outer tank ring space is connected into a whole by support, as shown in the figure Figure 4 The support has 4-8 groups, each group of support is fixed between the inner and outer tank in X shape, and the support point is at the same position as the outer ring. The total weight of the inner and outer tank is about 650T, and the weight of the inner tank is about 168T. The support is fixed at 20 positions of the inner and outer tank, the support point is at the same position as the tank lifting support, and the installation height is between 3.2-6.2 meters. The weld leg height is the thinnest plate thickness, the weld leg height of the connection point between the support and the outer tank is 14mm, and the weld leg height of the connection point between the support and the inner tank is 8mm. After welding, the weld of the stress point is detected by PT to ensure that the welding is problem-free.

[0057] 7、evenly fixed ≥20 places of support on the ring; each support is provided with a jack column and a cushion column below, as shown in the figure Figure 2 The support includes a rib plate and a stress plate, the ring is fixed horizontally around the outer tank, the rib plate is fixed vertically outside the ring, and the stress plate is fixed horizontally below the rib plate and the ring. The number of rib plates is two, corresponding to the axis of the jack column and the cushion column respectively.

[0058] 8, to do the preparation work: tank before all the participants to the tank technical briefing and safety briefing, to confirm that all the tank with the annex has been removed (ethylene export pump combined tube material A553M TP1 part has been removed, radar level, servo level meter with the tank connected bracket all removed, the tank temperature gauge removed, the tank and the tank static grounding removed, the tank anchor band removed, etc.), in 20 column support point installation 20 hydraulic jacks (stroke 150 mm), so that 20 jacks have a point of force on the pedestal (that is, all jacks stay on the force plate of the pedestal, while measuring the height of the 20 jacks has been lifted, to provide parameters for the synchronization of the later lifting), and the jack, jack column, the force point of the pedestal must be on the same axis (force point to ensure that all components bear the maximum point on the force). Remove the tank anchor band (according to the anchor band to remove the butt joint), then evenly distributed cutting tank bottom plate up 50 mm wall, after a wall cutting is completed, ready to lift the tank.

[0059] 9, to lift the tank (the weight of the tank is about 650T, select 11 100T hydraulic jacks, 9 50T hydraulic jacks, meet the requirements of lifting the tank), 20 people at the support point at the same time operating hydraulic jacks to lift the tank (lifting point set operation platform), for synchronous lifting, requires 20 people to press 30 times within a minute, on-site arrangements for a full-time order officer to command, every five minutes to stop once to lift the height statistics, and check the mechanical, tank and tank whether there is an abnormal, to confirm the lifting height synchronization and no abnormalities can continue to lift, when the jack stroke reaches 150 mm, in the pad column pad 135 mm pad and install the bolt to make the column and pad connection, pad like Figure 3As shown, the cushion and the cushion column are connected by bolts, then the jack is lowered, so that the cushion pushes against the stressed plate, the jack is removed, a 135mm bracket (the bracket is the same as the cushion) is installed below the jack, and the above method is used to rise again by 135mm. According to the above operation three times, when the storage tank rises by 405mm, it is ensured that each cushion column supports the storage tank, and the four supports under the inner tank wall plate are installed (the supports are installed in the symmetric direction, and the inner side of the beam edge plate is directly cantilevered to the outer tank wall), the stress must be directly below the wall plate, (stainless steel plate is used to isolate the contact with the 9Ni plate). The temporary support of the outer tank lifting wall plate maintains 8 support points, controls the balance of the tank lifting process, and is removed when the bottom plate is replaced. People need to patrol the outer tank at all times during the jacking process, and data is recorded every 5 minutes; During the jacking process, two people check whether there are any connecting parts between the inner and outer tanks, whether the connecting bracket between the inner and outer tanks is abnormal, and stop jacking immediately if any abnormalities are found. After jacking is completed, check whether there are any abnormalities in the weld of the workpiece, and perform PT inspection on the weld of the connecting bracket between the inner and outer tanks to ensure the stability of the inner and outer tanks. During the jacking process, the inner and outer tanks are selected as 8 points for support (the 8 points must be symmetrically and uniformly distributed), and the cushion steel plate is installed after each rise until the end of the tank jacking, using H200*200 H-shaped steel and Φ273*6 seamless steel pipe as the inclined support under the inner and outer tank wall plates (replace the steel plate), the inclined support is connected with the ground by expansion bolts and embedded plates to ensure the balance after the tank is raised, such as Figure 6 As shown.

[0060] 10. After the stability of the inner and outer tanks is reinforced, the ring beam is removed, the remaining cold insulation material is removed, the outer tank bottom plate is cut, the outer tank bottom plate is removed, the foundation is cleaned, and the outer tank bottom plate is installed. In order to reduce the period of lifting the storage tank, the edge plate is installed, the edge plate RT and PT are detected without defects, and the vacuum box test is qualified, then the tank bottom concrete leveling layer and the cold insulation work at the ring beam are performed, and then the ring beam is installed, so as to make the storage tank in place as soon as possible. During the cold insulation work at the edge plate and the installation of the ring beam, the first section of the wall plate of the outer tank is replaced, and the specific method is shown in Figure 7 During the replacement of the wall plate, the original wall plate is removed, the wall plate is divided into several parts, and the wall plate is symmetrically removed during the removal to ensure the balance of the storage tank. During the removal and installation of the wall plate, the column is protected to prevent collision and imbalance of the balance of the tank body.

[0061] 11. After the cold insulation work at the ring beam and the installation of the ring beam are completed, the installation of the outer tank wall plate is completed, the bottom plate edge plate at the door opening of the inner tank is installed and welded, and 100% RT and PT detection are performed and qualified.

[0062] 12, prepare to reset the work of the storage tank, the process and steps (9) of the lifting method are opposite operations. When the first section of the wall plate and the second section of the wall plate are reduced to the position of the joint, stop reducing, then assemble the wall plate ring joint, adjust the perpendicularity of the wall plate, the wall plate geometry detection is qualified, and the wall plate longitudinal ring joint is qualified, then weld the big foot weld, after welding, remove all the columns and supports.

[0063] 13, after the completion of the storage tank in place, the middle plate of the outer tank is installed, the bottom plate weld must be at least 2 welds, the bottom plate deformation needs to be controlled during the welding process, and the bottom plate weld is welded according to the welding sequence, and the bottom plate weld is penetrated and tested and qualified, then the remaining center area is cooled, the middle plate of the inner tank bottom plate is installed after the cooling work is completed, the bottom plate deformation is controlled during the welding of the middle plate, and the bottom plate is penetrated and tested and vacuum tested.

[0064] 14, the construction of the ceiling edge cover plate is carried out, all accessories and supporting brackets of the inner tank and the outer tank are installed. After the completion of all work of the inner tank, the inner tank door hole is sealed, and the static grounding is installed. After the completion of all work of the inner tank, the water pressure test is carried out, and after the completion of all work of the outer tank, the outer tank door hole is sealed and the air tightness test is carried out.

[0065] 15, the water discharge of the water pressure test, the inner tank is cleaned, and after the completion of the remaining cooling work and the outer tank painting, the tank is sealed, the tank drying and nitrogen replacement work are carried out, the tank pre-cooling operation guidance work is carried out, and the whole maintenance work is completed.

[0066] The low-temperature ethylene large storage tank safety maintenance process fixes the inner tank and the outer tank together by using the X-shaped supporting piece, ensures the synchronous movement of the inner tank and the outer tank, installs the expansion ring and the support on the outer tank, uses a plurality of jacks to lift the support, lifts the inner tank and the outer tank to a certain height, installs the cushion block and fixes it on the column, and ensures the stability and safety of the suspended storage tank. The structure is simple, the construction method is scientific and novel, the operation is convenient, the deformation is small, the whole process does not need a large lifting machine or an electric hoist on the rack, the construction cost is low, and the stability and safety are high.

[0067] It should be noted that the above content only illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. For ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements fall within the protection scope of the claims of the present application.

Claims

1. A safe maintenance process for cryogenic ethylene large-scale storage tanks, characterized in that: The method comprises the following steps: (1) remove the electrical, instrumentation, pipelines connected to the tank, remove the ceiling and the inner and outer tank annular space between the cold material; (2) the tank hole is opened, the limited space is detected for flammable gas content; (3) a circle of the ring is added on the outside of the lower part of the second section of the outer tank wall plate, the installation position of the ring is above the welding seam between the first section of the wall plate and the second section of the wall plate, (4) an operating platform is installed on the outside of the outer tank, and a temporary construction door hole is opened on the inner and outer tank wall plate corresponding to the operating platform; (5) the inner tank is installed with explosion-proof lighting, the welding seam between the edge plate of the inner tank and the middle plate is cut by a grinding machine, and the cold insulation material of the tank bottom is removed; (6) the inner and outer tank annular space is connected into a whole by adding support members; the support members have 4-8 groups, each group of support members is fixed between the inner and outer tanks in an X shape, and the support points are at the same position as the rings on the outside; (7) ≥20 supports are uniformly fixed on the rings; a jack column and a cushion column are arranged below each support; (8) a hydraulic jack is installed on each jack column, the jack supports the support without moving, the anchoring belt of the outer tank is removed, and the outer tank bottom plate is cut by 50 mm upwards; (9) all jacks are simultaneously pressed upwards by hand, the support drives the tank to be lifted, the pressing is stopped for 30 times, the lifting height is counted, and it is checked whether the mechanical equipment, the inner and outer tanks are abnormal, the lifting height is confirmed to be synchronous and no abnormality, then the lifting is continued, when the stroke of the jack reaches 150 mm, 135 mm cushion blocks are placed at the cushion column and connected with the column by bolts to make the column and the cushion block integrated, then the jack is lowered to make the cushion block bear the force, the jack is removed, a 135 mm bracket is installed below the jack, the tank is lifted by 135 mm according to the above method, and the cycle is repeated, when the lifting height of the tank reaches 405 mm, it is ensured that each cushion column supports the tank, and meanwhile, 4 supports are placed below the inner tank wall plate; (10) after the tank is stabilized, the ring beam is removed, the outer tank bottom plate is cut, the foundation is cleaned, and the outer tank bottom plate is installed after line laying, in order to reduce the period of lifting the tank, the edge plates are concentratedly installed, the edge plate RT and PT are detected to be free of defects, and the vacuum box test is qualified, then the tank bottom concrete leveling layer and the cold insulation work at the ring beam are performed, and then the ring beam is installed, so that the tank is positioned as soon as possible; when the cold insulation work and the ring beam installation at the edge plate are performed, the first section of the outer tank wall plate is replaced, (11) after the cold insulation work at the ring beam and the installation of the ring beam are completed, the installation of the outer tank wall plate is completed, the bottom edge plate at the construction door hole of the inner tank is installed and welded, and 100% RT and PT detection are performed and qualified; (12) the tank is reset, and the resetting process is the reverse operation of the lifting method in step (9), when the first section of the wall plate and the second section of the wall plate are aligned, the lowering is stopped, then the ring seam of the wall plate is welded, the perpendicularity of the wall plate is adjusted, the wall plate geometric dimension detection is qualified, the wall plate longitudinal ring seam is qualified in nondestructive testing, the anchoring belt is welded, after the welding is completed, all the columns and supports are removed; (13) After the tank is in place, the outer tank is installed, and the remaining center area is cooled after the bottom plate weld is penetrated and the vacuum box test is passed. After the cooling work is completed, the inner tank bottom plate is installed, and the bottom plate is deformed during welding. The bottom plate is penetrated and vacuum tested; (14) The ceiling edge cover plate is modified and constructed, and all accessories and supporting brackets of the inner tank and outer tank are installed; After the inner tank is completed, the inner tank door is sealed, and the static grounding is installed. After the inner tank is completed, the water test is performed, and after the outer tank is completed, the outer tank door is sealed for air tightness test; (15) After the test is completed, the inner tank is cleaned, and after the remaining cooling work and outer tank painting are completed, the tank is sealed, the tank is dried and nitrogen is replaced, the tank is pre-cooled and the operation is guided. The entire maintenance work is completed.

2. The cryogenic ethylene full-scale storage tank safety maintenance process according to claim 1, characterized in that: The door hole size of step (4) is 4715mm*2825mm.

3. The cryogenic ethylene full-scale storage tank safety maintenance process according to claim 1, characterized in that: The support of step (7) includes a rib plate and a stress plate, and the expansion ring is fixed horizontally around the outer tank. The rib plate is vertically fixed outside the expansion ring, and the stress plate is horizontally fixed below the expansion ring and the rib plate.

4. The cryogenic ethylene full-scale storage tank safety maintenance process according to claim 3, characterized in that: The number of rib plates is two, corresponding to the axis of the jack column and the cushion column.

5. The cryogenic ethylene full-scale storage tank safety repair process of claim 1, wherein: The cushion of step (9) is a square frame structure; the cushion and the cushion column are connected by bolts.

6. The cryogenic ethylene full-scale storage tank safety repair process of claim 5, wherein: The bracket of step (9) is the same as the cushion.

7. The cryogenic ethylene full-scale storage tank safety maintenance process of claim 1, wherein: Step (10) said after the tank is stable, it is reinforced, a inclined brace is arranged outside the jack column and the cushion column, the inclined brace is connected with the ground through expansion bolts and embedded plates.

8. The cryogenic ethylene full-scale storage tank safety maintenance process of claim 1, wherein: The jack column and the cushion column are made of H-shaped steel.

9. The cryogenic ethylene full-scale storage tank safety maintenance process of claim 1, wherein: The number of anchor belts in step (12) is greater than or equal to 70, and the anchor belts are fixedly connected with the pile cap below the tank body.

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