Wall panel installation method for large LNG storage tanks

Abstract

The application discloses a wall plate mounting method for a large LNG storage tank, which comprises the following steps: 1, welding the bottom plate of the LNG storage tank; 2, transporting the components for erecting a floating bridge to the central position of the bottom plate; 3, arranging the wall plates of the lowermost circle of the LNG storage tank on the bottom plate; 4, arranging a floating bridge in the form of a ring close to the inner wall of the wall plates of the lowermost circle of the LNG storage tank; 5, hoisting the wall plates of the next circle to be welded and arranging corresponding expansion rings to realize fixation, and meanwhile, water is injected into the space surrounded by all the wall plates and the bottom plate which have been welded, so that the floating bridge is floated to a height satisfying the welding personnel on the floating bridge to perform welding work; 6, welding the wall plates of the next circle to be welded, and removing the corresponding expansion rings after nondestructive testing is qualified; and 7, repeating steps 5 and 6 until the wall plates of the uppermost circle of the LNG storage tank. The application shortens the construction period and avoids damage of the wall plates of the LNG storage tank during construction.

Description

Technical Field

[0001] The present invention relates to the technical field of LNG storage tank construction, and in particular to a wall panel installation method for a large LNG storage tank. Background Art

[0002] At present, large-scale LNG cryogenic storage tanks, i.e. LNG cryogenic storage tanks with a capacity of 50,000 cubic meters or above, are mainly divided into three types: single-containment tanks, double-containment tanks, and full-containment tanks. Full-containment tanks consist of an inner tank and an outer tank, which together constitute a complete storage tank. The inner tank is a self-supporting steel tank for storing liquid products, while the outer tank is a self-supporting steel or concrete tank with a dome. Since the LNG storage temperature is -163°C, perlite particles need to be filled in the annular space between the outer tank and the inner tank to keep the LNG in the inner tank cold.

[0003] The low-temperature steel inner tank, low-temperature steel outer tank and normal-temperature steel outer tank are designed using the allowable stress method, and the materials of the low-temperature steel inner tank and low-temperature steel outer tank are austenitic stainless steel or 9% Ni steel.

[0004] Single containment tanks currently mainly consist of a low-temperature steel inner tank, a tank bottom insulation layer, a foundation, a foundation heating system, a flexible insulation seal, a suspended ceiling, a normal-temperature steel tank roof, loose insulation fillers, a normal-temperature steel outer tank (not capable of containing liquefied natural gas), and a containment dike.

[0005] The double containment tank consists of a low-temperature steel inner tank, a low-temperature steel outer tank, prestressed concrete, a tank bottom insulation layer, a foundation, a foundation heating system, a flexible insulation seal, a suspended ceiling (insulation layer), a normal-temperature steel tank top, loose insulation fillers, a normal-temperature steel outer tank (not capable of containing liquefied natural gas), and a top cover (rain shield);

[0006] The full-containment tank consists of a low-temperature steel inner tank, a low-temperature steel outer tank, a tank bottom insulation layer, a foundation, a foundation heating system, a flexible cold insulation seal, a suspended ceiling (cold insulation layer), a normal temperature steel roof, loose cold insulation filler, a concrete roof, and a prestressed concrete outer tank; the membrane tank consists of a low-temperature steel inner tank, a prestressed concrete outer tank, a tank bottom insulation layer, a foundation, a foundation heating system, a flexible cold insulation seal, a suspended ceiling (cold insulation layer), and a cold insulation layer inside the concrete outer tank.

[0007] In the prior art, the installation methods of LNG storage tank wall panels mainly include upright installation and inverted installation.

[0008] Among them, the formal method mainly includes internal scaffolding and external full-automatic welding method, as well as external scaffolding and internal full-automatic welding method.

[0009] Not only is it expensive to build scaffolding, but it also needs to be welded to the LNG tank wall panels. When dismantling the scaffolding, the root position of the weld between the cut scaffolding and the tank wall panels needs to be polished.

[0010] Therefore, how to simplify the installation process of LNG tank wall panels, reduce construction costs, and eliminate the damage caused by the need to grind the root position of the welding between the scaffolding and the tank wall panels has become a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0011] In view of the above-mentioned defects of the prior art, the present invention provides a method for installing wall panels of large LNG storage tanks, the purpose of which is to simplify the process of installing LNG storage tank wall panels, reduce construction costs, and eliminate damage caused by the need to grind the root position of the welding between the scaffolding and the tank wall panels.

[0012] To achieve the above object, the present invention discloses a method for installing a wall panel of a large LNG storage tank, comprising the following steps:

[0013] Step 1: Weld the bottom plate of the LNG storage tank and perform a vacuum tightness test on the bottom plate;

[0014] Step 2: transporting the components for building the floating bridge to the center of the base plate;

[0015] Step 3: Arrange the wall panels of the bottom circle of the LNG storage tank on the bottom plate;

[0016] Step 4: disposing a ring-shaped floating bridge in the wall panel of the bottom circle of the LNG storage tank, close to the inner wall of the wall panel;

[0017] Step 5: hoist the next circle of wall panels to be welded and set corresponding expansion rings to fix them. At the same time, water is poured into the space enclosed by all the wall panels and the bottom plate that have been welded, so that the floating bridge is floated to a height that allows the welders on the floating bridge to perform welding work.

[0018] Step 6: Weld the next circle of the wall panel to be welded, and remove the corresponding expansion ring after passing the non-destructive test;

[0019] Step 7: Repeat steps 5 and 6 until the top wall panel of the LNG storage tank is reached;

[0020] Step 8: dismantling the floating bridge;

[0021] Step 9: Weld the top plate of the LNG storage tank. The top plate is prefabricated and installed on the ground and then hoisted as a whole.

[0022] Step 10: The top plate is put into place and welded, and the weld is subjected to non-destructive testing after completion;

[0023] Step 11: inject water from the water injection hole close to the bottom plate and perform strength and sealing tests on the welded LNG storage tank;

[0024] Step 12, after meeting the strength and tightness requirements of the experiment, the clean internal water is drained, and then water is injected and flushed through the manhole position on the top of the tank, and then dried after flushing.

[0025] Preferably, the bottom plate is a tortoise type plate, which is welded by 4 groups of welding personnel in a symmetrical form.

[0026] Preferably, the components used to erect the floating bridge include a plurality of floating barrels, safety nets, a plurality of railings, and patterned steel plates.

[0027] More preferably, the floating barrels are plastic barrels made of polyvinyl chloride material.

[0028] More preferably, the floating bridge includes a plurality of floating barrels arranged close to the wall plates of the lowermost circle of the LNG storage tank, and the patterned steel plates laid on all the floating barrels.

[0029] The railings are arranged as safety guardrails on one side of each two floating barrels close to the center position of the LNG storage tank.

[0030] Moreover, the safety ropes are connected between every two safety guardrails, and the safety nets are used to cover them.

[0031] Preferably, the method for arranging the lowermost circle of wall plates on the bottom plate is as follows:

[0032] Step 3.1, hoist the lowermost circle or the uppermost first circle of wall plates of the LNG storage tank into position;

[0033] Step 3.2, install the corresponding expansion ring on the wall plates that have been hoisted to achieve fixation with the bottom plate or the top plate;

[0034] Step 3.3, weld the inner side and the outer side of the wall plates respectively;

[0035] Step 3.4, perform non-destructive testing on the completed welds, and remove the expansion ring after the testing is qualified.

[0036] Preferably, in step 3.4, the non-destructive testing is performed on the fillet weld between the wall plates and the bottom plate, as well as the vertical weld and the horizontal weld of the lowermost circle of wall plates of the LNG storage tank.

[0037] Preferably, each wall plate is hoisted into position in a symmetrical form by two mobile cranes.

[0038] Preferably, each of the wall panels is welded symmetrically by four groups of welders at positions corresponding to the interior of the LNG storage tank, and then welded by a fully automatic welding carriage at positions corresponding to the exterior of the LNG storage tank.

[0039] Preferably, the wall panels of the bottom circle of the LNG storage tank are opened with holes and welded with a short steel pipe with a water injection valve and a size of DN80, and water is injected into the space enclosed by all the wall panels and the bottom plate that have been welded through the short steel pipe; the water is clean water or fresh water.

[0040] Preferably, before executing step 8, all the wall panels and the bottom panels that have been welded are placed in water and allowed to stand for 48 hours to perform a strength pressure test.

[0041] Preferably, in step 8, the floating bridge is dismantled by a high-altitude hanging basket, and the components used to erect the floating bridge are transported out.

[0042] Preferably, in step 11, after draining water from the water injection hole near the bottom plate, a negative pressure is formed in the LNG storage tank, and real-time detection is carried out to strictly guard against deformation of any of the wall panels.

[0043] Preferably, each of the wall panels is subjected to anti-corrosion coating in a prefabrication yard before welding, and the spray rust removal level is Sa2.5 anti-corrosion coating.

[0044] Preferably, after completing all steps, each weld is derusted using ST3 grade manual power and repainted.

[0045] Preferably, after completing all steps, the internal garbage of the LNG storage tank is transported out through the manhole on the tank top for processing.

[0046] Preferably, when cleaning the interior of the LNG storage tank, after the staff enters the LNG storage tank, a forced mechanical blower is installed in the manhole on the tank top for ventilation; the staff carries lighting fixtures with a safety voltage of less than 36V.

[0047] Preferably, in step 11, the manhole is closed when the negative pressure test and the sealing test are performed on the LNG storage tank, and the manhole is opened immediately after the test is completed.

[0048] Beneficial effects of the present invention:

[0049] The application of the present invention shortens the construction period, reduces labor costs and material costs, turns waste float barrels / plastic barrels into treasure, enables resources to be recycled, and avoids damage to the LNG storage tank wall during construction.

[0050] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram illustrating a state in which the welding of the wall panels of the bottom circle of the LNG storage tank is completed and the floating bridge is set up is shown in one embodiment of the present invention.

[0052] Figure 2 A partially enlarged schematic diagram of a bottom plate provided with a floating bridge in one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0053] Example

[0054] like Figure 1 and Figure 2 As shown, the wall panel installation method of a large LNG storage tank includes the following steps:

[0055] Step 1: Weld the bottom plate 6 of the LNG storage tank and perform a vacuum tightness test on the bottom plate 6;

[0056] Among them, 2. Perform a vacuum box tightness test on the bottom plate 6. It is necessary to apply soapy water to the weld of the bottom plate 6 and evacuate the weld. If bubbles are generated, it means that there are pores at the weld position and rework is required.

[0057] Step 2: transport the components for building the floating bridge to the center of the bottom plate 6;

[0058] Step 3: Install the wall panels of the bottom circle of the LNG storage tank on the bottom plate 6;

[0059] Step 4: Arrange an annular floating bridge in the wall panel of the bottom circle of the LNG storage tank, close to the inner wall of the wall panel;

[0060] Step 5: hoist the next circle of wall panels to be welded and set the corresponding expansion ring 8 to fix them. At the same time, water is poured into the space enclosed by all the wall panels and the bottom plate 6 that have been welded, so that the pontoon is floated to a height that allows the welders on the pontoon to perform welding work.

[0061] The specification of the expansion ring 8 is [20 channel steel, material is Q235B;

[0062] The distance between the floating bridge and the weld seam to be welded is 600mm, which is convenient for welding. The amount of water injected is determined according to the height of the weld seam. The height can be suitable for welding.

[0063] Step 6: Weld the next circle of wall panels to be welded, and remove the corresponding expansion ring 8 after passing the non-destructive test;

[0064] Up to the top wall of the LNG tank;

[0065] Step 8: Dismantle the floating bridge;

[0066] Step 9: Weld the top plate of the LNG storage tank. The top plate is prefabricated and installed on the ground and then hoisted as a whole.

[0067] Step 10: Place the top plate in place and weld it. After completion, perform non-destructive testing on the welds.

[0068] Step 11: inject water from the water injection hole near the bottom plate 6 and perform strength and sealing tests on the welded LNG storage tank;

[0069] Step 12: After meeting the strength and tightness requirements of the experiment, drain the water inside, then flush with water through the manhole on the top of the tank, and dry it after flushing.

[0070] The present invention avoids the need to set up scaffolding during the installation and welding process of the LNG storage tank wall plate, eliminates the need to weld the scaffolding to the LNG storage tank wall plate, and eliminates the risk of damage to the tank wall plate due to welding;

[0071] There is no need to dismantle the scaffolding, which eliminates the need to cut the scaffolding first and then grind the root position of the weld between the cut scaffolding and the tank wall panel during the dismantling process, and will not cause damage to the wall panel.

[0072] It also accelerated the construction progress, changed the process flow, and brought forward the strength pressure test and tightness test of the storage tank, so that welding, non-destructive testing, and strength testing can be carried out in parallel, shortening the project construction period.

[0073] In some embodiments, the bottom plate 6 is a tortoise-shaped plate and is welded symmetrically by four groups of welders.

[0074] In some embodiments, the components used to build the floating bridge include a plurality of buoys 11 , a safety net 10 , a plurality of railings 9 and a patterned steel plate 14 .

[0075] In some embodiments, the float barrel 11 is a plastic barrel made of polyvinyl chloride material.

[0076] In some embodiments, the floating bridge includes a plurality of floating barrels 11 disposed close to the wall panels of the lowest circle of the LNG storage tank, and a patterned steel plate 14 laid on all the floating barrels 11;

[0077] A railing 9 is provided between each two floating barrels 11 on one side close to the center of the LNG storage tank as a safety guardrail;

[0078] Moreover, every two safety guardrails are connected by a safety rope and are covered with a safety net 10.

[0079] In actual application, the safety guardrail formed by the multiple railings 9, as well as the provision of the safety rope and the safety net 10 can prevent welders from accidentally falling into the water during work.

[0080] The floating barrel 11 can be used to recycle discarded plastic barrels and garbage from petrochemical plants and turn waste into treasure.

[0081] The specification of the floating barrel 11 is 600*600*800mm. If the plastic barrel discarded by the petrochemical plant is small, two layers of floating barrels 11 can also be fixed.

[0082] The patterned steel plate 14 is 0.2 mm thick in order to prevent welding sparks from falling and burning the float 11 and to protect it.

[0083] In some embodiments, the method for setting the bottom circle of wall panels on the bottom plate 6 is as follows:

[0084] Step 3.1: Hoist the bottom or top wall panels of the LNG storage tank into place;

[0085] Step 3.2: Install the corresponding expansion ring 8 on the hoisted wall panel to secure it to the bottom plate 6 or the top plate;

[0086] Step 3.3: Weld the inner and outer sides of the wall panels respectively;

[0087] Step 3.4: Perform nondestructive testing on the completed weld and remove the expansion ring 8 after the test is qualified.

[0088] Non-destructive testing usually uses radiography, ultrasound or penetration testing and is performed at night when there is no construction work.

[0089] In some embodiments, in step 3.4, non-destructive testing is performed on the fillet welds 15 between the wall panels and the bottom panel 6, as well as the vertical welds 5 and the transverse welds 7 of the wall panels of the bottom circle of the LNG storage tank.

[0090] In some embodiments, each wall panel is lifted into place using two mobile cranes 3 in a symmetrical manner.

[0091] In some embodiments, each wall panel is symmetrically welded by four groups of welders at positions corresponding to the interior of the LNG storage tank, and then welded by a fully automatic welding carriage at positions corresponding to the exterior of the LNG storage tank.

[0092] In some embodiments, a hole is opened in the wall panel of the bottom circle of the LNG storage tank and a short steel pipe with a DN80 size and a water injection valve 12 is welded, and water is injected into the space enclosed by all the welded wall panels and the bottom plate 6 through the short steel pipe; the water is clean water or fresh water.

[0093] In actual application, you can use municipal water or tap water nearby, or dig a well after obtaining approval from local government departments, and set a layer of filter at the water inlet and injection holes to prevent debris from entering the storage tank.

[0094] In some embodiments, before executing step 8, all the wall panels and bottom panels 6 that have been welded are placed in water and allowed to stand for 48 hours to perform a strength pressure test.

[0095] In some embodiments, in step 8, the floating bridge is dismantled by a high-altitude hanging basket, and the components used to build the floating bridge are transported out.

[0096] In some embodiments, in step 11, after draining water from the water injection hole near the bottom plate 6, a negative pressure is formed in the LNG storage tank, and real-time detection is carried out to strictly guard against deformation of any wall panel.

[0097] In some embodiments, each wall panel is subjected to anti-corrosion coating at a prefabrication site before welding, and the spray rust removal level is Sa2.5 anti-corrosion coating.

[0098] In certain embodiments, after all steps are completed, each weld is manually powered with ST3 grade rust removal and touch-up paint is applied.

[0099] In certain embodiments, after all steps are completed, the waste inside the LNG storage tank is transported out through the manhole on the tank top for disposal.

[0100] In certain embodiments, when cleaning the interior of an LNG storage tank, after workers enter the LNG storage tank, a forced mechanical blower is installed in the manhole on the tank top for ventilation; the workers carry lighting fixtures with a safety voltage of less than 36V.

[0101] In certain embodiments, in step 11, the manhole is closed when the LNG storage tank undergoes the negative pressure test and the sealing test, and the manhole is opened immediately after the test is completed.

[0102] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. The wall panel installation method of a large LNG storage tank includes the following steps: Step 1: Welding the bottom plate (6) of the LNG storage tank and performing a vacuum tightness test on the bottom plate (6); Step 2: transporting the components for building the floating bridge to the central position of the bottom plate (6); The components used to build the floating bridge include a plurality of floating barrels (11), a safety net (10), a plurality of railings (9) and a patterned steel plate (14); the floating bridge includes a plurality of floating barrels (11) arranged close to the wall plate of the bottom circle of the LNG storage tank, and the patterned steel plate (14) laid on all the floating barrels (11); The floating barrel (11) is a plastic barrel made of polyvinyl chloride material; The railing (9) is provided on one side between each two of the floating barrels (11) and close to the center of the LNG storage tank as a safety guardrail; Furthermore, each two of the safety guardrails are connected by a safety rope and are covered with the safety net (10); Step 3, arranging the wall panels of the bottom circle of the LNG storage tank on the bottom plate (6); Step 4: disposing a ring-shaped floating bridge in the wall panel of the bottom circle of the LNG storage tank, close to the inner wall of the wall panel; Step 5: hoist the next circle of the wall panels to be welded and set the corresponding expansion ring (8) to fix them, and at the same time, inject water into the space enclosed by all the wall panels and the bottom plate (6) that have been welded, so that the floating bridge floats to a height that satisfies the welding work of the welding personnel on the floating bridge; Step 6, welding the next circle of the wall panel to be welded, and removing the corresponding expansion ring (8) after passing the non-destructive test; Step 7: Repeat steps 5 and 6 until the welding of the top wall panel of the LNG storage tank is completed; Step 8: dismantling the floating bridge; Step 9: Weld the top plate of the LNG storage tank. The top plate is prefabricated and installed on the ground and then hoisted as a whole. Step 10: The top plate is put into place and welded, and the weld is subjected to non-destructive testing after completion; Step 11, injecting water from the water injection hole close to the bottom plate (6), and performing a strength test and a sealing test on the welded LNG storage tank; Step 12: After meeting the strength and tightness requirements of the test, drain the water inside, then flush with water through the manhole on the top of the tank, and dry it after flushing.

2. The wall panel installation method according to claim 1, characterized in that: The bottom plate (6) is a tortoise-shaped plate and is welded in a symmetrical manner by four groups of welders.

3. The wall panel installation method according to claim 1, characterized in that: The method for arranging the bottommost circle of the wall panels on the bottom plate (6), or arranging the topmost circle of the wall panels on the top plate is as follows: Step 3.1, hoisting the wall panels of the bottom circle or the top circle of the LNG storage tank into place; each wall panel is hoisted into place in a symmetrical manner using two mobile cranes (3); Step 3.2, installing corresponding expansion rings (8) on the hoisted wall panels to secure them to the bottom plate (6) or the top plate; Step 3.3, welding is performed on the inner side and the outer side of the wall panel respectively; Step 3.4: Perform nondestructive testing on the completed welds, and remove the expansion ring (8) after passing the test; perform the nondestructive testing on the fillet welds (15) between the wall panel and the bottom plate (6), as well as the vertical welds (5) and the horizontal welds (7) of the wall panel at the bottom of the LNG storage tank.

4. The wall panel installation method according to claim 1, characterized in that: Each of the wall panels is welded by four groups of welders who symmetrically weld the vertical welds (5) of the wall panels at positions corresponding to the interior of the LNG storage tank, and then weld the wall panels at positions corresponding to the exterior of the LNG storage tank using a fully automatic welding trolley; each of the wall panels is subjected to anti-corrosion coating in the prefabrication yard before welding, and a Sa2.5 grade rust removal layer is sprayed.

5. The wall panel installation method according to claim 1, characterized in that: The wall panels of the bottom circle of the LNG storage tank are opened and welded with a short steel pipe with a water injection valve (12) and a size of DN80, and water is injected into the space surrounded by all the wall panels and the bottom plate (6) that have been welded through the short steel pipe; the water is clean water or fresh water.

6. The wall panel installation method according to claim 1, characterized in that: Before executing step 8, all the wall panels and the bottom plate (6) that have been welded are placed in water and allowed to stand for 48 hours to perform a strength pressure test.

7. The wall panel installation method according to claim 1, characterized in that: In step 8, the floating bridge is dismantled by means of a high-altitude hanging basket, and the components used to erect the floating bridge are transported out.

8. The wall panel installation method according to claim 1, characterized in that: In step 11, after water is released from the water injection hole near the bottom plate (6), negative pressure is formed in the LNG storage tank, and real-time detection is performed to prevent any of the wall panels from being deformed; The manhole is closed when the negative pressure test and the sealing test of the LNG storage tank are carried out, and the manhole is opened immediately after the test is completed.

9. The wall panel installation method according to claim 1, characterized in that: After completing all the steps, each weld is derusted with ST3 grade manual power and repainted; The internal garbage of the LNG storage tank is transported out through the manhole on the tank top; When cleaning the interior of the LNG storage tank, after the workers enter the LNG storage tank, a forced mechanical blower is installed in the manhole on the tank top for ventilation; the workers carry lighting fixtures with a safety voltage of less than 36V.

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