Method for installing sewage discharge pipeline of secondary insulating layer of LNG (Liquefied Natural Gas) ship

Abstract

According to the LNG ship secondary insulation layer sewage discharge pipeline installation method, an embedded butt welding mode of an ultralow-temperature discharge pipeline is adopted at a cabin penetration piece, single-face welding operation is only carried out on the outer side of a sewage well, full penetration welding and double-face forming are carried out, and workers do not need to enter the sewage well to carry out welding operation. And in addition, the butt welding compound plate and the protection pipe are subjected to nail welding in the pipe prefabricating stage, adjustment of accumulated errors caused by manufacturing, construction and the like in the later period is facilitated, and the problem that the installation precision is not high is solved. The ultralow-temperature discharge pipeline is connected with the cabin penetration compound plate and the butt welding elbows in a welded mode, leakage of liquid or boil-off gas of the liquid cargo tank is effectively avoided, danger is avoided, the 1.5-time-length butt welding elbows are more beneficial to smooth discharge of ultralow-temperature discharge objects, the problem that maintenance is inconvenient is effectively solved, and the service life of the ultralow-temperature discharge pipeline is prolonged. Meanwhile, the installation of the tightness test device at the end part is more convenient. And the problem of liquid accumulation in the pipeline is solved, later maintenance is facilitated, and the design quality is improved.

Description

Technical Field

[0001] The invention belongs to the field of marine ship design and construction, and in particular relates to a method for installing an insulating layer sewage discharge pipeline of an LNG ship. Background Art

[0002] LNG carriers are ships that are specially used to transport liquefied natural gas. They are "super-refrigerated trucks at sea" that carry LNG at minus 163 degrees Celsius and are known as the "crown jewel" of the shipbuilding industry. Due to the particularity of LNG carriers, they have extremely high requirements for safety and sealing, so they have high requirements for the design and construction of pipeline systems and equipment. The isolation tank is a compartment that separates the front and rear tanks of LNG ships. Its main functions are fire prevention, explosion prevention, and leakage prevention. The secondary insulation layer sewage well of the LNG ship is set in the isolation tank. A discharge pipeline needs to be set to achieve the connection between the secondary insulation layer discharge and the secondary insulation layer. The design requirements of this pipeline are higher than those of conventional ships, and the tightness and durability of the pipeline need to be considered, which increases the difficulty of design and construction technology. Since the secondary insulation layer sewage well is a square box with a length (1360mm) x width (860 mm) x height (560 mm), the internal space is extremely small. The conventionally designed LNG secondary insulation layer sewage well discharge pipeline adopts the secondary insulation layer ultra-low temperature pipeline. The sewage well through-tank composite plate is lap-welded with the sewage well bulkhead. The lap-welding type of the composite plate and the structural plate requires welding on both sides, but it is impossible for personnel to enter the sewage well for welding. If extended welding tools are used to weld inside the sewage well, the space is limited, heat sources are generated during welding, and air cannot circulate effectively, and the welding quality cannot be guaranteed. There are even certain safety risks in welding in a small space. In addition, the low-temperature discharge pipeline welded in this case will be prone to rapid corrosion in the later operation after a long time, and the tightness and strength will be weakened. In this case, the pipeline is prone to corrosion, causing leakage, and there are major safety hazards. Once it occurs, it is easy to cause safety accidents.

[0003] In order to effectively solve the problems of double-sided welding of through-chamber parts cannot be achieved due to the small space of the sewage well, and the pipeline is prone to corrosion and leakage after a long time, as well as to improve the welding quality, improve the installation accuracy of low-temperature pipelines, reduce corrosion and avoid leakage, multiple schemes and multiple angles have been improved to achieve safe and effective discharge of the medium from the secondary insulation layer sewage well and the isolated empty cabin sewage well. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for installing an insulating layer sewage discharge pipeline of an LNG ship, and the technical solution adopted is: A method for installing a secondary insulating layer sewage discharge pipeline for an LNG ship, wherein a secondary insulating layer sewage well is arranged below an isolation void compartment, one end of a secondary insulating layer discharge pipe is connected to the secondary insulating layer, and the other end passes through a side wall of the secondary insulating layer sewage well and enters the secondary insulating layer sewage well.

[0005] An opening with a diameter of 820mm is opened on the side wall of the secondary insulation layer sewage well. A 35° groove is set at the opening, and the groove angle is outward. The through-tank casing is welded at the groove. The through-tank casing has a protective tube located in the center and a double plate outside the protective tube. A 35° groove is set at the connection between the double plate and the protective tube, and the groove angle is outward.

[0006] During installation, the protective tube and the ultra-low temperature tube are welded together in the prefabrication stage, and the composite plate and the protective tube are nailed and welded in the prefabrication stage. First, adjust the composite plate and the secondary insulation layer sewage well side wall to be accurately aligned. After positioning, first weld the composite plate and the secondary insulation layer sewage well side wall, and then weld the composite plate and the protective tube. These two welds are welded by the single-sided welding and double-sided forming method.

[0007] An upper suction discharge pipe is adopted, and the end of the discharge pipe penetrates the top plate of the secondary insulation layer sewage well downward and extends into the secondary insulation layer sewage well. A right-angle check valve is arranged at the corner of the discharge pipe, and the check valve is connected to the pneumatic diaphragm pump unit via a straight-through stop valve.

[0008] The above-mentioned method for installing the sewage discharge pipeline of the insulating layer of the LNG ship further adopts a current of 120A for welding when the protection pipe is welded to the composite plate and when the web is welded to the side wall of the sewage well.

[0009] In the above-mentioned method for installing the sewage discharge pipeline of the insulating layer of an LNG ship, further, the opening diameter of the composite plate is 3 mm larger than the diameter of the protective pipe.

[0010] The above-mentioned method for installing the secondary insulation layer sewage discharge pipeline of an LNG ship further comprises: a filter screen is provided at the end of the secondary insulation layer discharge pipe located inside the sewage well, and the end is 400 mm away from the side wall of the sewage well.

[0011] In the above-mentioned method for installing the sewage discharge pipeline of the insulating layer of an LNG ship, the filter screen is further fixed by a flange clamping form.

[0012] The above-mentioned method for installing the secondary insulation layer sewage discharge pipeline of an LNG ship further has the end of the discharge pipe being 30±5mm away from the inner bottom of the secondary insulation layer sewage well.

[0013] The above-mentioned method for installing a sewage discharge pipeline of a secondary insulation layer of an LNG ship further comprises a through-tank composite plate being arranged at the connection between the secondary insulation layer discharge pipe and the secondary insulation layer.

[0014] The above-mentioned method for installing the sewage discharge pipeline of the insulating layer of an LNG ship further comprises the step of: the other end of the pneumatic diaphragm pump unit is connected to the hose through a pipeline and a hose connector valve.

[0015] The present invention adopts an embedded butt welding type of ultra-low temperature discharge pipe at the through-tank part, and only performs single-sided welding outside the sewage well, performs full penetration, and double-sided forming, without the need for personnel to enter the sewage well for welding. In addition, the butt-welded composite plate is nailed and welded with the protective pipe in the prefabricated pipe stage, which is conducive to the adjustment of the accumulated errors due to production and construction in the later stage, and solves the problem of low installation accuracy. The ultra-low temperature discharge pipe is connected by welding through-tank composite plates and butt-welded elbows, which effectively avoids the leakage of liquid or evaporative gas in the liquid cargo tank and avoids danger. The 1.5-times long butt-welded elbow is more conducive to the smooth discharge of ultra-low temperature discharge objects. The end of the ultra-low temperature discharge pipe is set to 400mm long from the sewage well bulkhead, which effectively solves the problem of inconvenient maintenance and maintenance. At the same time, it is more convenient to install a tightness test device at the end. This invention also solves the problem of liquid accumulation in the pipeline, is more conducive to later maintenance and maintenance, improves the design quality, ensures the purpose of no need for open fire maintenance during the entire life cycle of the pipeline system, is safer, and improves the operating value of the ship. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the secondary insulation layer, the isolation air chamber, and the sewage well of the secondary insulation layer; Figure 2 It is a schematic diagram of the structure of the present invention; Figure 3 yes Figure 2 A schematic diagram of the enlarged structure of the middle circle I; Figure 4 It is a schematic diagram of the through-tank casing structure; Among them, 1-secondary insulation layer discharge pipe, 1.1-through cabin double plate, 1.4-double plate, 1.5-sewage well side wall, 1.6-protection pipe, 1.8-flange, 2.1-discharge pipe, 2.2-right angle check valve, 2.3-straight stop valve, 2.4-pneumatic diaphragm pump unit, 2.5-hose connector valve, 2.6-hose, F-isolation empty cabin, G-ultra-low temperature liquid tank, H-secondary insulation layer sewage well. DETAILED DESCRIPTION

[0017] The present invention will be further described in conjunction with the accompanying drawings.

[0018] A method for installing an insulating layer sewage discharge pipeline on an LNG ship, such as Figure 1 As shown, the secondary insulating layer sewage well is arranged below the isolation empty cabin, one end of the secondary insulating layer discharge pipe is connected with the secondary insulating layer, a through-cabin composite plate is arranged at the connection between the secondary insulating layer discharge pipe and the secondary insulating layer, and the other end passes through the side wall of the secondary insulating layer sewage well and enters the secondary insulating layer sewage well.

[0019] like Figure 2 , 3As shown in Figure 4, an opening with a diameter of 820 mm is opened on the side wall of the sewage well of the secondary insulation layer. A 35° groove is set at the opening, and the groove angle is outward. The through-tank casing is welded at the groove. The through-tank casing consists of a protective tube located in the center and a double plate outside the protective tube. A 35° groove is set at the connection between the double plate and the protective tube, and the groove angle is outward. The opening diameter of the double plate is 3 mm larger than the outer diameter of the protective tube, and the opening of the side wall of the sewage well of the secondary insulation layer is 2 mm larger than the outer diameter of the double plate.

[0020] During installation, the protective tube and the ultra-low temperature tube are welded together in the prefabrication stage, and the composite plate and the protective tube are nailed and welded in the prefabrication stage. First, adjust the composite plate and the secondary insulation layer sewage well side wall to be accurately aligned. After positioning, first weld the composite plate and the secondary insulation layer sewage well side wall, and then weld the composite plate and the protective tube. These two welds are welded by the single-sided welding and double-sided forming method.

[0021] An upper suction discharge pipe is adopted, and the end of the discharge pipe penetrates the top plate of the secondary insulation layer sewage well downward and extends into the secondary insulation layer sewage well. A right-angle check valve is arranged at the corner of the discharge pipe, and the check valve is connected to the pneumatic diaphragm pump unit.

[0022] A filter screen is provided at the end of the secondary insulation layer discharge pipe located inside the sewage well, and the end is 400 mm away from the side wall of the sewage well.

[0023] Since the sewage well has a small space and cannot meet the welding conditions and requirements, this invention solves this problem.

[0024] The present invention discharges to the secondary insulating layer sewage well through the secondary insulating layer discharge pipe, and a right-angle check valve and a straight-through valve are arranged on the discharge pipe to form a double-valve isolation. The double valve is opened to act through the pneumatic diaphragm pump unit to suck the medium into the pipeline and discharge it to the collection device. After the medium of the secondary insulating layer sewage well is discharged, the blow-off valve arranged in front of the diaphragm pump outlet is connected to compressed air for blowing to remove the accumulated liquid in the pipeline. When the present invention is used, the secondary insulating layer sewage well discharge pipeline of the entire isolation cabin will not retain the medium.

Claims

1. A method for installing an insulating layer sewage discharge pipeline for an LNG ship, characterized in that: The secondary insulation layer sewage well is arranged below the isolation void compartment, one end of the secondary insulation layer discharge pipe is connected to the secondary insulation layer, and the other end passes through the side wall of the secondary insulation layer sewage well and enters the secondary insulation layer sewage well; An opening with a diameter of 820 mm is opened on the side wall of the sewage well of the secondary insulation layer. A 35° groove is set at the opening, and the groove angle is outward. The through-tank casing is welded at the groove. The through-tank casing has a protective pipe located in the center and a double plate outside the protective pipe. A 35° groove is set at the connection between the double plate and the protective pipe, and the groove angle is outward. During installation, the protection tube and the ultra-low temperature tube are welded together in the prefabrication stage, and the composite plate and the protection tube are nailed and welded in the prefabrication stage. First, adjust the composite plate and the side wall of the secondary insulation layer sewage well to be accurately aligned. After positioning, first weld the composite plate and the side wall of the secondary insulation layer sewage well, and then weld the composite plate and the protection tube. These two welds are welded by single-sided welding and double-sided forming method; An upper suction discharge pipe is adopted, and the end of the discharge pipe penetrates the top plate of the secondary insulation layer sewage well downward and extends into the secondary insulation layer sewage well. A right-angle check valve is arranged at the corner of the discharge pipe, and the check valve is connected to the pneumatic diaphragm pump unit.

2. The method for installing an insulating layer sewage discharge pipeline of an LNG ship according to claim 1 is characterized in that: When welding the protective pipe to the composite plate and the web to the side wall of the sewage well, a current of 120A is used for welding.

3. The method for installing an insulating layer sewage discharge pipeline of an LNG ship according to claim 1 is characterized in that: The opening diameter of the double plate is 3 mm larger than the diameter of the protection tube.

4. The method for installing an insulating layer sewage discharge pipeline of an LNG ship according to claim 1 is characterized in that: A filter screen is provided at the end of the secondary insulation layer discharge pipe located inside the sewage well, and the end is 400 mm away from the side wall of the sewage well.

5. The method for installing an insulating layer sewage discharge pipeline of an LNG ship according to claim 4 is characterized in that: The filter screen is fixed by means of flange clamping.

6. The method for installing an insulating layer sewage discharge pipeline of an LNG ship according to claim 1, characterized in that: The end of the discharge pipe is 30±5mm away from the bottom of the sewage well in the secondary insulation layer.

7. The method for installing an insulating layer sewage discharge pipeline for an LNG ship according to claim 1, characterized in that: A through-cabin composite plate is arranged at the connection between the secondary insulation layer discharge pipe and the secondary insulation layer.

8. The method for installing an insulating layer sewage discharge pipeline of an LNG ship according to claim 1, characterized in that: The other end of the pneumatic diaphragm pump unit is connected to the hose through a pipeline and a hose connector valve.

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