A method for LNG ship retrofitting

Abstract

This application relates to the field of liquefied natural gas (LNG) storage and transportation, and more particularly to a method for modifying LNG carriers. The method includes: removing a first cover plate from the cargo hold and removing the spherical cargo tank and supporting components from the cargo hold; modifying the cargo hold walls to obtain the target cargo hold, and installing a second cover plate adapted to the membrane cargo tank on top of the target cargo hold; obtaining the spatial contour of the decahedron space, and laying wedges and adhesive materials on the cargo hold walls according to the spatial contour to form an installation plane for installing a membrane containment system on the cargo hold walls; laying the membrane containment system on the installation plane to obtain a membrane-type cargo tank, thus completing the modification of the LNG carrier's cargo tank. The method provided in this application can reduce the cost of obtaining membrane-type LNG carriers.

Description

Technical Field

[0001] This application relates to the field of liquefied natural gas (LNG) carrier conversion, and in particular to a method for converting LNG carriers. Background Technology

[0002] Membrane-type cargo tanks offer advantages over traditional spherical tanks, including higher capacity utilization and a wider deck view. However, due to their early adoption, spherical cargo tanks are already widely used and form a large fleet in service. Directly phasing out LNG (Liquid Natural Gas) ships using spherical cargo tanks and building new LNG ships with membrane-type cargo tanks would result in a significant waste of hull structure resources and a substantial increase in the economic costs for shipowners.

[0003] Therefore, there is an urgent need for a method to retrofit LNG carriers to achieve a reliable conversion from spherical cargo tanks to membrane cargo tanks, so as to improve operational economics while making full use of existing hull resources. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this application provides a method for modifying the liquid cargo tank of an LNG ship, so as to achieve a safe and efficient conversion of a MOSS-type LNG ship to a membrane-type containment system.

[0005] The present application is described below from multiple aspects, and the embodiments and beneficial effects of these aspects can be referred to each other.

[0006] In a first aspect, this application provides a method for modifying an LNG carrier. A spherical cargo tank is installed in the LNG carrier's hold via supporting components. The method includes: removing a first cover plate from the hold and removing the spherical cargo tank and supporting components from the hold; modifying the hold walls to obtain a target hold, and installing a second cover plate adapted to the membrane cargo tank on the top of the target hold, wherein the target hold and the second cover plate together form a decahedral space accommodating the membrane cargo tank; obtaining the spatial outline of the decahedral space, and laying wedges and adhesive materials on the walls of the target hold according to the spatial outline to form an installation plane for installing a membrane containment system on the walls of the target hold; and laying the membrane containment system on the installation plane to obtain a membrane-type cargo tank, thus completing the modification of the LNG carrier's cargo tank.

[0007] In one implementation of the first aspect, the pipeline connection between the first cover plate and the spherical liquid cargo tank is disconnected, the pipeline including a liquid phase pipeline, a gas phase pipeline or an electrical circuit; the cover plate of the ship's hold is removed, and the support connection between the spherical liquid cargo tank and the support component is disconnected; the spherical liquid cargo tank is removed from the ship's hold by means of a crane, and the support component is removed.

[0008] In one implementation of the first aspect, the bulkhead of the target ship compartment is a planar bulkhead; the bottom of the ship compartment is modified to obtain a bottom bulkhead located at the bottom of the ship compartment; the circumferential part of the ship compartment is modified to obtain four circumferential bulkheads located in the circumferential part of the ship compartment, and four inclined bulkheads located between the circumferential bulkheads and the bottom bulkhead; the bottom bulkhead, the inclined bulkheads and the circumferential bulkheads are connected to obtain the target ship compartment; a second cover plate is installed on the target ship compartment to form a decahedral space together with the bulkheads of the target ship compartment, wherein the decahedral space is used to accommodate a thin-film liquid cargo tank.

[0009] In one implementation of the first aspect, multiple sampling points on the target bulkheads of multiple bulkheads of the target ship compartment are determined, and the spatial coordinates of the sampling points are obtained; based on the spatial coordinates of the sampling points, a first fitting plane corresponding to each target bulkhead is determined; based on the first fitting planes corresponding to multiple target bulkheads, a spatial contour corresponding to the target ship compartment is spliced ​​out; based on the spatial contour corresponding to the target ship compartment, wedges and adhesive materials are laid on the bulkheads of the target ship compartment to form an installation plane on the bulkheads of the target ship compartment that coincides with the spatial contour.

[0010] In one implementation of the first aspect, target spheres are set at the locations of multiple sampling points on the target bulkhead, and the distance between each target sphere and the laser rangefinder is obtained by using a laser rangefinder; a spatial rectangular coordinate system is established with the spatial position of the laser rangefinder as the origin, and the spatial coordinates of each sampling point are determined according to the distance between the target sphere and the laser rangefinder.

[0011] In one implementation of the first aspect, the included angle between each of the relative first fitting planes in the spatial profile is less than 5 degrees.

[0012] In one implementation of the first aspect, the adhesive material is resin putty.

[0013] In one implementation of the first aspect, the thickness of the wedges at each wedge installation position on the bulkhead is determined based on the spatial profile and the distance between the bulkheads; wedges of different thicknesses are laid at each wedge installation position on the bulkheads; resin putty is laid between the wedges to form an installation plane for installing the membrane enclosure system.

[0014] In one implementation of the first aspect, the flatness of the plane formed by multiple wedges is measured; based on the flatness, the thickness of each wedge is adjusted so that the flatness error of the plane formed by the multiple wedges meets the first requirement.

[0015] In one implementation of the first aspect, the first requirement includes: the height difference between the wedges on each bulkhead and the adjacent wedges is less than 1.5 mm.

[0016] In one implementation of the first aspect, a membrane-type enclosure system, consisting of a secondary shielding layer, a primary insulating layer, a primary shielding film, and auxiliary structures, is installed layer by layer on an installation plane to obtain a membrane-type liquid cargo tank. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall process of the LNG ship conversion method provided in the embodiments of this application;

[0018] Figure 2 A side view of a ship's compartment containing a spherical chamber, provided for an embodiment of this application;

[0019] Figure 3 A schematic diagram of a ship's cabin after bulkhead modification, provided as an embodiment of this application;

[0020] Figure 4 This is a side view of the target cabin after the second cover plate has been added, as provided in an embodiment of this application. Detailed Implementation

[0021] The embodiments of this application include, but are not limited to, a method for converting an LNG carrier. The method provided in the embodiments of this application can convert an existing LNG carrier equipped with a spherical cargo tank into an LNG cargo tank equipped with a membrane-type cargo tank.

[0022] The installation method of the liquid cargo tank membrane enclosure system provided in the embodiments of this application will be described below with reference to the accompanying drawings.

[0023] Figure 1 This is an exemplary flowchart of the LNG ship conversion method provided in the embodiments of this application, with reference to... Figure 1 The LNG ship conversion method provided in this application includes:

[0024] S110: Remove the first cover of the hold and remove the spherical cargo tank and supporting components from the hold.

[0025] It is understood that a liquid cargo tank is a container used to transport liquid loads, including liquid hydrogen, liquid ammonia, or liquefied natural gas, etc., which are not limited in this application.

[0026] It is understandable that liquid cargo tanks can be divided into spherical liquid cargo tanks or membrane-type liquid cargo tanks. Among them, spherical liquid cargo tanks can be... Figure 2 To represent. For example... Figure 2 As shown, multiple support members 120 are provided on the semi-circular first bulkhead 110, and the spherical cargo tank 130 is located on... Figure 2 On the multiple support members 120, the first cover plate 140 covers the spherical liquid cargo tank 130.

[0027] The support member 120 may include components such as skirt base and support column, which are not limited in this application.

[0028] It is understandable that the first cover plate 140 can protect the spherical liquid cargo tank 130 to prevent damage to the spherical liquid cargo tank 130.

[0029] Therefore, in order to facilitate the construction work and the removal of the spherical liquid cargo tank 130 or the support component 120, the first cover plate 140 needs to be removed first.

[0030] In some embodiments, since there are complex pipelines arranged under the cover plate, it is necessary to disconnect the pipeline connection between the first cover plate 140 and the spherical cargo tank 130 before removing the first cover plate 140. Figure 2 (Not shown in the drawing). The pipeline may include liquid phase pipeline, gas phase pipeline or circuit, which is not limited in this application.

[0031] It is understandable that after opening the first cover 140, the spherical liquid cargo tank 130 located therein can be taken out.

[0032] In some embodiments, the spherical liquid cargo tank 130 is connected to the support member 120. Therefore, in order to remove the spherical liquid cargo tank 130, it is necessary to disconnect the support connection between the spherical liquid cargo tank 130 and the support member 120.

[0033] It is understandable that since the membrane tank to be installed is constructed by directly attaching it to the bulkhead, the support member 120 does not need to be retained in the ship's hold. When the spherical liquid cargo tank in the ship's hold needs to be removed, the connection between the support member 120 and the first bulkhead 110 is also disconnected, and the support member 120 is also removed when the spherical liquid cargo tank 130 is removed.

[0034] In some embodiments, the removal of the spherical liquid cargo tank 130 may include lifting the spherical liquid cargo tank out of the ship's hold using a crane to remove the spherical liquid cargo tank. The specific removal method will not be described in detail here.

[0035] S120: Modify the bulkhead of the ship's hold to obtain the target ship's hold, and install a second cover plate adapted to the membrane liquid cargo tank on the top of the target ship's hold, wherein the target ship's hold and the second cover plate together form a decahedral space to accommodate the membrane liquid cargo tank.

[0036] It is understandable that since the first bulkhead 110 is a curved bulkhead, it cannot be directly used to lay a membrane-type liquid cargo tank. Therefore, the first bulkhead 110 needs to be modified to transform it into the target bulkhead, which is a flat bulkhead.

[0037] It is understandable that modifications to the ship's bulkheads can be divided into two parts: bottom modifications and circumferential modifications. For example... Figure 3 As shown, Figure 3 This is a schematic diagram of the target bulkhead after modification. Figure 3In the diagram, L represents the length of the ship, V represents the vertical extension from the bottom to the deck, and the bottom bulkhead 210 is obtained by modifying the bottom. The first circumferential bulkhead 220, the second circumferential bulkhead 230, the third circumferential bulkhead 240, and the fourth circumferential bulkhead 250 are modifications made to the circumferential portion of the cabin. The first inclined bulkhead 260, the second inclined bulkhead 270, the third inclined bulkhead 280, and the fourth inclined bulkhead 290 are bulkheads connecting the bottom bulkhead 210 and adjacent inclined bulkheads. By connecting the bottom bulkhead 210, the first circumferential bulkhead 220, the second circumferential bulkhead 230, the third circumferential bulkhead 240, and the fourth circumferential bulkhead 250, as well as the first inclined bulkhead 260, the second inclined bulkhead 270, the third inclined bulkhead 280, and the fourth inclined bulkhead 290, the target cabin 200 can be obtained.

[0038] According to S110, the surface of the liquid cargo tank also needs to be covered. For the cover of the membrane tank, its inner surface and the target ship's tank can together form a decahedral space to accommodate the membrane liquid cargo tank. For example, in Figure 4 In the middle, the inner surface of the second hatch 300 can form a top bulkhead 310 located at the top of the decahedral space, and the top bulkhead 310 can be connected with the circumferential bulkhead to form a sloping bulkhead 320.

[0039] S130: Obtain the spatial contour of the decahedral space, and lay wedges and adhesive materials on the bulkhead of the target cabin according to the spatial contour to form an installation plane on the bulkhead of the target cabin for installing the membrane enclosure system.

[0040] It can be understood that spatial contour is a virtual contour used to represent the contours of the various bulkheads of the target ship's compartments in three-dimensional space.

[0041] For example, S131 to S134 provide a method for calculating a spatial contour, specifically including:

[0042] S131: Determine multiple sampling points on the target bulkheads within multiple bulkheads of the target ship's compartment, and obtain the spatial coordinates of the sampling points.

[0043] It is understandable that, in order to reduce the computational load, the plane corresponding to each bulkhead can be represented by the coordinates of several sampling points on each bulkhead.

[0044] In some embodiments, in order to obtain the spatial coordinates of the sampling points, target spheres can be set at the sampling points in the corner areas of each compartment wall of the liquid cargo tank, and the distance between each target sphere and the laser rangefinder can be obtained according to the laser rangefinder.

[0045] As can be understood, a target ball is a reflectance measurement marker with a standard geometric shape (usually a high-precision sphere) and its surface is coated with a high-reflectivity coating (such as aluminum dioxide, magnesium fluoride, etc.), which can reflect the incident laser back to its original position along the original path.

[0046] As can be understood, a laser rangefinder is an optoelectronic measuring device that uses the principle of laser pulse or phase measurement to measure distance. It can accurately measure the distance between the rangefinder and the object being measured. In the embodiments of this application, the laser rangefinder emits a laser beam and receives the echo signal reflected by the target ball, and obtains the distance between the laser rangefinder and the target ball based on the laser flight time or phase difference.

[0047] It is understandable that after obtaining the distance between the laser rangefinder and the target ball, a spatial rectangular coordinate system can be established with the spatial position of the laser rangefinder as the origin, and the first spatial coordinates of each sampling point can be determined based on the obtained distance between the laser rangefinder and the target ball.

[0048] It is understandable that when measuring the distance between the laser rangefinder and the target ball using a laser rangefinder as described above, the angles between the laser beam and the three coordinate axes in a Cartesian coordinate system can be recorded simultaneously. Thus, the projection of the second distance onto the three coordinate axes, i.e., the spatial coordinates of the sampling point, can be determined using the angles between the laser beam and the three coordinate axes.

[0049] S132: Determine the first fitting plane corresponding to each target bulkhead based on the spatial coordinates of the sampling points.

[0050] It is understandable that due to processing errors, welding deformations, and assembly deviations during the manufacturing and assembly of liquid cargo tanks, the actual constructed bulkheads are not ideal absolute planes. Based on this, a first fitted plane corresponding to each bulkhead can be fitted using the spatial coordinates of the sampling points obtained in S131.

[0051] It is understood that the first fitting plane can be determined in a variety of ways (e.g., principal component analysis), and this application does not limit it here.

[0052] S133: Based on the first fitting planes corresponding to multiple target bulkheads, the spatial contours corresponding to the target hulls are pieced together;

[0053] S134: Based on the spatial contour corresponding to the target cabin, lay wedges and adhesive materials on the bulkhead of the target cabin to form an installation plane on the bulkhead of the target cabin that coincides with the spatial contour.

[0054] It is understood that there is a certain distance between the spatial outline of the target ship's cabin and the bulkhead of the target ship's cabin. Therefore, wedges and putty can be used to form an installation plane on the bulkhead of the target ship's cabin, and make the installation plane coincide with the spatial outline.

[0055] In some embodiments, the adhesive material is resin putty, and the wedge can be a wooden structure made of plywood, which is not limited herein.

[0056] It is understandable that unevenness is unavoidable during the construction of the bulkhead, resulting in varying wedge thicknesses at different installation locations. Therefore, to determine the installation plane, the thickness of the wedges at each installation location on the bulkhead can first be determined based on the spatial outline and the distance between the bulkheads. Then, wedges of different thicknesses are laid at each installation location on the bulkhead.

[0057] It is understandable that due to calculation errors, even if each wedge is laid according to the calculated thickness, the surface formed by the wedges will still be uneven. Therefore, the wedges need to be adjusted again.

[0058] Specifically, the flatness of the plane formed by multiple wedges can be measured first. Then, based on the flatness, the thickness of each wedge is adjusted so that the flatness error of the plane formed by the multiple wedges meets the first requirement.

[0059] The first requirement is flatness. In some embodiments, the flatness requirement is that the height difference between the wedges on each bulkhead and the adjacent wedges is less than 1.5 mm.

[0060] It is understood that the height difference mentioned above can be any decimal greater than 0.5 mm and less than 3 mm, such as 0.5 mm, 1 mm, 1.6 mm or 2 mm, in addition to 1.5 mm. This application does not limit this to any specific value.

[0061] After the wedges are laid, resin putty can be laid between the wedges to form an installation surface for installing the membrane enclosure system.

[0062] S140: Lay a membrane enclosure system on the installation plane to obtain a membrane-type liquid cargo tank, thus completing the modification of the liquid cargo tank of the LNG ship.

[0063] It is understood that after obtaining the mounting plane in S130, the secondary shielding layer, secondary insulation layer, primary insulation layer, primary shielding layer, and auxiliary structures of the membrane-type enclosure system can be installed layer by layer on the mounting plane to obtain a membrane-type liquid cargo tank. The layers can be connected by welding or gluing, which is not limited in this application.

[0064] It should be noted that the terminology used in the embodiment section of this application is only for explaining specific embodiments of this application and is not intended to limit this application. In the description of the embodiments of this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in this document is merely a description of the positional relationship between the sampling point and the fitting plane, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. In addition, in the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, "at least one" or "one or more" means one, two or more.

[0065] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0066] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0067] The above are merely specific embodiments of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the scope of the claims.

Claims

1. A method for converting an LNG carrier, characterized in that, The LNG carrier has a spherical cargo tank installed in its hold via support components, and the method includes: Remove the first cover of the hold, and remove the spherical cargo tank and the supporting components from the hold; The bulkhead of the ship's cabin is modified to obtain the target ship's cabin, and a second cover plate adapted to the thin-film liquid cargo tank is installed on the top of the target ship's cabin, wherein the target ship's cabin and the second cover plate together form a decahedral space to accommodate the thin-film liquid cargo tank; Obtain the spatial contour of the decahedral space, and lay wedges and adhesive materials on the bulkhead of the target cabin according to the spatial contour to form an installation plane for installing the membrane enclosure system on the bulkhead of the target cabin. The membrane enclosure system is laid on the installation plane to obtain a membrane-type liquid cargo tank, thus completing the modification of the liquid cargo tank of the LNG ship.

2. The method according to claim 1, characterized in that, The removal of the first cover plate of the ship's hold and the removal of the spherical cargo tank and the supporting components from the ship's hold include: Disconnect the pipeline connection between the first cover plate and the spherical liquid cargo tank, wherein the pipeline includes a liquid phase pipeline, a gas phase pipeline, or an electrical circuit; Remove the cover plate of the hull and disconnect the support connection between the spherical liquid cargo tank and the support component; The spherical cargo tank is lifted out of the ship's hold using a crane to remove the spherical cargo tank and the supporting components.

3. The method according to claim 1, characterized in that, The target cargo hold has a flat bulkhead; the modification of the bulkhead to obtain the target cargo hold, and the installation of a second cover plate adapted to the membrane cargo tank on the top of the target cargo hold, includes: The bottom of the cabin is modified to obtain a bottom bulkhead located at the bottom of the cabin; The circumferential portion of the cabin is modified to obtain four circumferential bulkheads located in the circumferential portion of the cabin, and four inclined bulkheads located between the circumferential bulkheads and the bottom bulkhead; The bottom bulkhead, the sloping bulkhead, and the circumferential bulkhead are connected to obtain the target ship compartment; A second cover plate is installed on the target ship's compartment to form a decahedral space together with the bulkhead of the target ship's compartment, wherein the decahedral space is used to accommodate the thin-film liquid cargo tank.

4. The method according to claim 1, characterized in that, The process of obtaining the spatial contour of the decahedral space and laying wedges and adhesive material on the bulkhead of the target ship's cabin according to the spatial contour to form an installation plane for installing the membrane enclosure system on the bulkhead of the target ship's cabin includes: Multiple sampling points on the target bulkheads within the target ship's compartment are determined, and the spatial coordinates of the sampling points are obtained. Based on the spatial coordinates of the sampling points, determine the first fitting plane corresponding to each of the target bulkheads; Based on the first fitting planes corresponding to the multiple target bulkheads, the spatial contours corresponding to the target cabins are pieced together. Based on the spatial contour corresponding to the target cabin, wedges and adhesive materials are laid on the cabin wall to form an installation plane on the cabin wall that coincides with the spatial contour.

5. The method according to claim 4, characterized in that, The step of determining multiple sampling points on multiple bulkheads of the target ship compartment and obtaining the spatial coordinates of the sampling points includes: Target spheres are set at the locations of multiple sampling points on the target bulkhead, and the distance between each target sphere and the laser rangefinder is obtained using a laser rangefinder. A spatial rectangular coordinate system is established with the spatial position of the laser rangefinder as the origin, and the spatial coordinates of each sampling point are determined according to the distance between the target ball and the laser rangefinder.

6. The method according to claim 4, characterized in that, The adhesive material is resin putty.

7. The method according to claim 6, characterized in that, The process of obtaining the spatial contour of the decahedral space and laying wedges and adhesive material on the bulkhead of the target ship's cabin according to the spatial contour to form an installation plane for installing the membrane enclosure system on the bulkhead of the target ship's cabin includes: The thickness of the wedge at each wedge installation position of the bulkhead is determined based on the distance between the spatial contour and the bulkhead. Wedges of different thicknesses are laid at the respective wedge installation locations on the bulkhead; The resin putty is laid between each of the wedges to form an installation surface for installing the membrane enclosure system.

8. The method according to claim 7, characterized in that, The method of laying wedges of different thicknesses at the wedge installation positions on the bulkhead includes... Measure the flatness of the plane formed by the multiple wedges; Based on the flatness condition, the thickness of each wedge is adjusted so that the flatness error of the plane formed by the multiple wedges meets the first requirement.

9. The method according to claim 8, characterized in that, The first requirement includes: The height difference between the wedges on each bulkhead and the adjacent wedges is less than 1.5 mm.

10. The method according to claim 1, characterized in that, The process of laying the membrane enclosure system on the installation plane to obtain a membrane-type cargo tank, thereby completing the modification of the LNG carrier's cargo tank, includes: By installing the secondary shielding layer, main insulation layer, main shielding film, and auxiliary structures of the membrane-type enclosure system layer by layer on the mounting plane, a membrane-type liquid cargo tank is obtained.

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