VLOC ship methanol fuel tank modification and modification method

Abstract

The present application relates to the technical field of VLOC ship refitting methanol fuel tank, and proposes a VLOC ship refitting methanol fuel tank and a refitting method, which can cooperate with the deck opening sequence and size, adopt a special treatment method for the methanol fuel tank structure with deck pieces, assemble from the methanol fuel tank deck opening sequence, reinforce the deck while assembling, solve the problems of the whole lifting of the deck small opening section and the whole turning of the unmanned section, realize the purpose of not occupying the dry dock for the sectional refitting of the methanol fuel tank of the VLOC ship at the mooring wharf, increase the construction portability, improve the construction environment, and save the refitting cost.

Description

Technical Field

[0001] This invention relates to the field of VLOC (Vehicle-Localized Ocean) vessel methanol fuel tank conversion technology, specifically, to a VLOC vessel methanol fuel tank conversion method. Background Technology

[0002] Very Large Ore Carriers (VLOCs) are large vessels used for transporting ore, often exceeding 200,000 tons in capacity, making them among the largest ore carriers in international trade. Currently, governments worldwide have enacted carbon reduction laws, and the International Maritime Organization (IMO) has set carbon reduction targets. Carbon reduction has become an urgent priority and is now on the international community's agenda. Existing VLOCs use traditional carbon (C)-based fuels, which produce large amounts of carbon dioxide (CO2) upon combustion, failing to meet carbon reduction requirements and thus hindering the achievement of IMO targets. Methanol, a liquid at room temperature and pressure, produces only water (H2O) vapor and carbon dioxide (CO2) upon combustion, offering ample storage and transportation options. However, methanol is a novel carbon-based compound fuel, a low-flash-point flammable and explosive liquid. Traditional ship fuel tanks are unsuitable for storing this fuel, requiring special design and modification. Summary of the Invention

[0003] One of the objectives of this invention is to propose a hybrid heave compensation system that can be adapted to the order and size of deck openings. This system employs a special treatment method with deck panels to assemble the methanol fuel tank structure sequentially from the openings on the top deck of the methanol fuel tank, reinforcing the top deck as it is assembled. This solves the problems of hoisting small-opening sections of the tank as a whole and tilting unmanned sections into their final positions. It enables the modular conversion of VLOC vessels' methanol fuel tanks at mooring docks without occupying dry dock, increasing construction portability, improving the construction environment, and saving conversion costs.

[0004] The technical solution of the present invention is as follows:

[0005] A method for converting VLOC (Vehicle-Localized Ocean Vehicle) vessels to methanol fuel tanks includes the following steps:

[0006] S100: Make a first cut in the top deck of the methanol fuel tank, hoist it into the bottom of the tank along the first cut, and weld it to the surrounding structure;

[0007] S200: After the bottom of the tank is welded and put into place, the central longitudinal bulkhead is hoisted in and welded to the surrounding structure. At the same time, the deck of the central longitudinal bulkhead is also spot welded to the top deck of the methanol fuel tank, and then the top deck of the methanol fuel tank is reinstalled.

[0008] S300: Make a second cut on the top deck of the methanol fuel tank, hoist the front bulkhead of the methanol tank along the second cut, first assemble the left and right front bulkhead sections, then hoist the middle front bulkhead of the adjustment section, after the three sections are positioned, weld them to the surrounding structure, and also spot weld them to the top deck of the methanol fuel tank, and then reassemble the top deck of the methanol fuel tank.

[0009] S400: Make a third cut on the top deck of the methanol fuel tank, hoist the liquid tank into the tank along the third cut and weld it to the surrounding structure, and at the same time spot weld it to the top deck of the methanol fuel tank, and then repair the top deck of the methanol fuel tank.

[0010] S500: A fourth cut is made on the top deck of the methanol fuel tank. The deck is then lowered along the fourth cut and welded to the surrounding structure. The fourth cut is made along the seam between the port and starboard sides of the deck.

[0011] S600: All structures have completed welding and non-destructive testing. The deckhouse has been hoisted to the top of the methanol fuel tank and welding has been completed, thus completing the conversion of the entire methanol fuel tank.

[0012] Furthermore, step S100 includes:

[0013] S110: A longitudinal reinforcing structure and a transverse reinforcing structure are provided around the first cut, and the width B of the first cut is consistent with the deck width on the central longitudinal bulkhead.

[0014] The longitudinal reinforcement structure is installed on the side longitudinal girders on both sides of the first cut, with both ends extending to the front bulkhead of the engine compartment and the rear bulkhead of the connected cargo compartment, respectively. The transverse reinforcement structure is installed between the rear bulkhead of the methanol tank, the rear bulkhead of the connected cargo compartment, and the two sets of longitudinal reinforcement structures, and is connected to each other to form a rectangular reinforcement frame.

[0015] S120: Then cut along the longitudinal girder beside the deck and the aft bulkhead of the methanol tank, and the closure seam of the aft bulkhead of the connected cargo hold.

[0016] Furthermore, in step S300, the width D of the second cut is the same as the deck width of the forward bulkhead of the methanol tank, and it is cut along the closure seam of the forward bulkhead of the methanol tank between the crossbeam and the aft bulkhead of the connected cargo hold.

[0017] Furthermore, in step S400, the width A of the third cut is the same as the width of the deck on the liquid tank, the height C of the third cut is the same as the height of the inner longitudinal wall on the liquid tank, and the third cut is provided with a chamfer R and cut along the closure seam of the left and right liquid tanks.

[0018] Furthermore, step S200 includes the following steps:

[0019] S210: Draw the bottom positioning line at the bow of the methanol fuel tank, make a clear mark with paint at the center line of the positioning line, and spot weld a baffle with a 75° inclination at the edge of the positioning line.

[0020] S220: Make a clear mark in the center of the bilge with flat iron, and weld lifting lugs to the front cross section of the bilge. Use the first crane to hang on the lifting lugs on the front cross section of the bilge to lift the bilge. Align the rear cross section of the bilge with the longitudinal direction of the first cut and lift it into the bilge.

[0021] S230: The hull is turned 90° inside the hull, and the second crane is used to lift it upwards from the lifting lugs on the rear cross section of the hull. After turning it over longitudinally;

[0022] S240: The first and second cranes lower the hull simultaneously, approaching the height of the baffle. After confirming that the flat iron of the hull aligns with the centerline paint markings of the positioning line, continue lowering the hull. Guided by the inclined surfaces of the methanol tank aft bulkhead, the port longitudinal bulkhead, the starboard longitudinal bulkhead, and the baffle, the hull is lowered until it is in place.

[0023] Furthermore, step S500 includes:

[0024] S510: Draw the fourth cut opening line on the top deck layer of the methanol fuel tank;

[0025] S520: The fourth cut is marked on the stern to the joint of the deck panel of the aft bulkhead of the methanol tank, and the bow is marked to the joint of the deck panel of the second cut.

[0026] S530: The fourth cut is made from the midship section to the first cut deck panel joint, from the side to the third cut deck panel joint and to the inner shell deck panel joint, and the fourth cut is made along the marked position;

[0027] S540: First, make the fourth cut on the left chord, then lift the left deck along the fourth cut on the left chord and weld it to the surrounding structure;

[0028] Then, open the fourth incision on the starboard side, hoist the starboard deck along the fourth incision on the starboard chord, and weld it to the surrounding structure to complete the deck replacement.

[0029] Another objective of this embodiment is to provide a methanol fuel tank conversion system for VLOC vessels, comprising a port compartment, a starboard compartment, a bilge, a center longitudinal bulkhead, a methanol tank forward bulkhead, a port liquid tank, a starboard liquid tank, a deck deck, a deckhouse, and empty compartments. The center longitudinal bulkhead is located between the port and starboard compartments. There are two empty compartments, each located on opposite sides of the port and starboard compartments. The bilge connects both empty compartments. The center longitudinal bulkhead divides the methanol fuel tank into two independent liquid tanks, left and right. The deckhouse is an independent compartment used to protect methanol auxiliary and supply equipment. The methanol tank forward bulkhead is divided into three sections: the port forward bulkhead, the starboard forward bulkhead, and the center forward bulkhead. The deck deck is divided into two sections: the port deck and the starboard deck. Manholes are provided on the two opposite inner walls of the port and starboard compartments.

[0030] Furthermore, the bottom of the cabin is provided with an inner bottom plate, and two empty cabins are connected to the two sides of the inner bottom plate respectively. Both the left and right cabins have inner longitudinal walls.

[0031] Furthermore, the deckhouse is divided into several independent compartments by vertical bulkheads;

[0032] The independent compartment includes an auxiliary equipment room, a fuel preparation room, a venting compartment, and a methanol daily use cabinet. The venting compartment is located in the fuel preparation room near the methanol daily use cabinet. The methanol daily use cabinet is protected by an isolation compartment, which is connected to the fuel preparation room through an opening.

[0033] The working principle and beneficial effects of this invention are as follows:

[0034] This paper presents a method for retrofitting existing VLOC vessels with methanol fuel tanks at mooring berths, including the method of hoisting and assembling the tank sections as a whole. By employing a special treatment method with deck panels to coordinate with the sequence and size of deck openings, the methanol fuel tank structure is assembled sequentially from the openings on the top deck of the tank. The top deck is reinforced during assembly, solving the challenges of hoisting and assembling the tank sections with small deck openings and the challenges of tilting and positioning unmanned tank sections as a whole. This method achieves the goal of retrofitting VLOC vessels with methanol fuel tanks at mooring berths without occupying dry dock, increasing construction portability, improving the construction environment, and saving retrofit costs. It provides technical support for retrofitting existing VLOC vessels with methanol fuel tanks. Attached Figure Description

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 Diagram showing the segmentation of the methanol fuel tank;

[0037] Figure 2 This is a cross-sectional view AA;

[0038] Figure 3 A schematic diagram of the front bulkhead of the methanol tank;

[0039] Figure 4 Diagram of deck openings;

[0040] Figure 5 The drawing shows the hull assembly, including the personnel hoisted into the hull.

[0041] Figure 6 The drawing shows the hull assembly, illustrating the hull turning and tipping over.

[0042] Figure 7 The drawing shows the hull assembly, illustrating its placement after it has been flipped over.

[0043] Figure 8 The hull assembly drawing shows the hull placement verification;

[0044] Figure 9 Assembly flowchart;

[0045] Figure 10This is a diagram showing the openings in the bulkheads of connected cargo holds, arranged symmetrically on the port chord and starboard side.

[0046] In the diagram: 11. Deck level; 12. Deckhouse; 13. Reinforced structure; 14. First cut; 15. Second cut; 16. Third cut; 17. Fourth cut; 2. Bottom; 3. Central longitudinal bulkhead; 4. Forward bulkhead of methanol tank; 41. Porto forward bulkhead; 42. Starboard forward bulkhead; 43. Central forward bulkhead; 45. Aft bulkhead of methanol tank; 46. Forward cross section of bottom; 47. Aft cross section of bottom; 48. Forward bulkhead of engine room; 5. Methanol fuel tank; 61. Porto tank; 62. Starboard tank; 63. Horizontal girder; 64. Straight ladder; 65. Outer plating; 66. Port longitudinal bulkhead; 67. Starboard longitudinal bulkhead; 71. Port compartment; 72. Starboard compartment; 73. Port empty compartment; 74. Starboard empty compartment; 75. Inner longitudinal bulkhead; 76. Inner floor plate; 81. Auxiliary equipment room; 82. Fuel preparation room; 83. Vent compartment; 84. Isolation compartment; 85. Methanol day tank; 91. Aft bulkhead of connected cargo hold; 92. First crane; 93. Second crane; 95. Process opening; 96. Baffle; 97. Inclined ladder. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1

[0049] like Figure 1-10 As shown, a method for retrofitting a VLOC vessel with a methanol fuel tank 5 is described. This method, in conjunction with the sequence and size of the deck openings, employs a special method involving deck panels to treat the methanol fuel tank 5 structure. A crane is used to sequentially assemble the methanol fuel tank 5 structure from the deck openings on the top of the tank (which is divided into a left and right methanol tank via the central longitudinal bulkhead 3). This allows existing VLOC vessels to be retrofitted at the mooring dock, achieving the goal of simultaneously assembling and reinforcing the deck openings on the top of the tank. This method is applicable to all platforms, vessels, and marine structures and is completed through the following steps.

[0050] Specifically, it includes the following steps:

[0051] S100: Using the dock crane, the methanol fuel tank 5 structure is assembled sequentially from the top deck opening of the methanol fuel tank 5. The opening line of the first cut 14 is marked on the top deck layer 11 of the methanol fuel tank 5. The first cut 14 is marked from the stern to the joint of the deck plate of the aft bulkhead 45 of the methanol tank, and from the bow to the joint of the deck plate of the adjacent cargo hold bulkhead. The center longitudinal girder of the deck is used as the baseline to mark lines to the port and starboard sides respectively.

[0052] A first cut 14 is made on the top deck layer 11 of the methanol fuel tank 5, and the tank bottom 2 is lowered along the first cut 14 and welded to the surrounding structure.

[0053] Step S100 includes:

[0054] S110: A longitudinal reinforcing structure 13 and a transverse reinforcing structure 13 are provided around the first cut 14. The width B of the first cut 14 is consistent with the deck width on the central longitudinal bulkhead 3. The width B of the first cut 14 is 6100mm, which is consistent with the deck width on the central longitudinal bulkhead 3. The left and right lines are 150mm away from the left and right longitudinal girder of the deck.

[0055] The longitudinal reinforcement structure 13 is installed on the side longitudinal girders on both sides of the first cut 14, and the two ends extend to the front bulkhead 48 of the engine compartment and the rear bulkhead 91 of the connected cargo compartment, respectively. The transverse reinforcement structure 13 is installed between the rear bulkhead 45 of the methanol tank, the rear bulkhead 91 of the connected cargo compartment and the two sets of longitudinal reinforcement structures 13, and they are connected to each other to form a rectangular reinforcement frame.

[0056] The longitudinal reinforcement structure 13 and the transverse reinforcement structure 13 are made of high-strength steel T-shaped profiles of T300x20 / 900x20. The transverse T-shaped profiles are installed between the aft bulkhead 45 of the methanol tank, the aft bulkhead 91 of the connected cargo tank, and the two longitudinal T-shaped profiles, and are connected to each other to form a rectangular reinforcement frame.

[0057] S120: Then make the first cut 14 along the marked position, specifically, along the longitudinal girder of the deck and the aft bulkhead 45 of the methanol tank, and the closing seam of the aft bulkhead 91 of the connected cargo hold.

[0058] S210: Draw the landing line of the bottom 2 of the methanol fuel tank 5 at the bow. Make a clear mark with paint at the center line of the landing line. Spot weld a baffle 96 with a 75° inclination at the edge of the landing line.

[0059] S220: Make a clear mark on the center of the bottom 2 with flat iron, and weld lifting lugs on the front cross section 46 of the bottom 2. Use the first crane 92 to hang on the lifting lugs on the front cross section 46 of the bottom 2 to lift the bottom 2. The rear cross section 47 of the bottom 2 is aligned with the longitudinal direction of the first cut 14 and lifted into the 2nd compartment.

[0060] S230: The bottom 2 is turned 90° inside the hull, and the second crane 93 is used to lift it upwards by hanging it on the lifting lug of the rear cross section 47 of the bottom hull, and then it is turned over longitudinally;

[0061] S240: The first crane 92 and the second crane 93 simultaneously lower the hull to near the height of the baffle 96. After confirming that the flat iron of the hull 2 ​​aligns with the centerline paint markings of the positioning line, continue lowering the hull 2, using the guide surfaces of the methanol tank aft bulkhead 45, the port longitudinal bulkhead 66, the starboard longitudinal bulkhead 67, and the baffle 96, until the hull 2 ​​is in place. Figure 5-8 The assembly drawing of hull 2 ​​is shown.

[0062] S200: The bottom 2 is hoisted into the first cut 14 and welded to the surrounding structure. After the bottom 2 is welded and put back in place, the central longitudinal bulkhead 3 is hoisted into the middle longitudinal bulkhead 3 and welded to the surrounding structure. The deck of the central longitudinal bulkhead 3 is also spot welded to the top deck layer 11 of the methanol fuel tank 5 at the same time. Then the top deck layer 11 of the methanol fuel tank 5 is restored.

[0063] S300: Make a second cut 15 on the top deck layer 11 of the methanol fuel tank 5. Specifically, draw the opening line of the second cut 15 on the top deck layer 11 of the methanol fuel tank 5. The distance between the left and right sides of the second cut 15 and the inner shell deck joint is the distance between the left and right sides of the second cut 15 and the bow line is drawn to the deck joint of the connected cargo hold aft bulkhead 91. The width of the second cut 15, D=2200mm, matches the deck width of the forward bulkhead 4 of the methanol tank. Between the crossbeam and the connected cargo hold aft bulkhead 91, make the second cut 15 along the closing joint of the forward bulkhead 4 of the methanol tank, i.e., at the marked position.

[0064] Then, the methanol tank front bulkhead 4 is hoisted in along the second cut 15. First, the left front bulkhead 41 and the right front bulkhead 42 are assembled. Then, the middle front bulkhead 43 of the adjustment section is hoisted in. After the three sections are positioned, they are welded to the surrounding structure and simultaneously spot-welded to the top deck layer 11 of the methanol fuel tank 5. Then, the top deck layer 11 of the methanol fuel tank 5 is reinstalled.

[0065] S400: Draw the third cut 16 opening line on the top deck layer 11 of the methanol fuel tank 5. The stern line of the third cut 16 is 500mm away from the aft bulkhead of the liquid tank, and the bow line extends to the joint of the deck plate of the adjacent cargo tank bulkhead. The width of the third cut 16, A=5500mm, is consistent with the width of the deck on the liquid tank, and the height, C=13000mm, matches the height of the inner longitudinal wall 75 on the liquid tank. The third cut 16 has a chamfer, and the chamfer R=1000mm.

[0066] Make a third cut 16 along the marked position on the top deck layer 11 of the methanol fuel tank 5, lower the liquid tank into the tank along the third cut 16 and weld it to the surrounding structure, and at the same time spot weld it to the top deck layer 11 of the methanol fuel tank 5, and then repair the top deck layer 11 of the methanol fuel tank 5.

[0067] First, open the third incision 16 on the left chord, and hoist the left liquid tank 61 into the port chord along the third incision 16 and weld it to the surrounding structure; then open the third incision 16 on the starboard side, and hoist the right liquid tank 62 into the starboard side along the third incision 16 and weld it to the surrounding structure, thus completing the liquid tank hoisting.

[0068] In step S400, the width A of the third cut 16 is the same as the width of the deck on the liquid tank, and the height C of the third cut 16 is the same as the height of the inner longitudinal wall 75 on the liquid tank. The third cut 16 is provided with a chamfer R and is cut along the seam of the left liquid tank 61 and the right liquid tank 62, and is symmetrically distributed on the left and right sides.

[0069] S500: A fourth cut 17 is made on the top deck layer 11 of the methanol fuel tank 5. The deck layer 11 is hoisted along the fourth cut 17 and welded to the surrounding structure. The fourth cut 17 is cut along the seam between the port and starboard sides of the deck.

[0070] Step S500 includes:

[0071] S510: Draw the fourth cut 17 opening line on the top deck layer 11 of the methanol fuel tank 5;

[0072] S520: The fourth cut 17 is marked on the stern to the 45 deck panel joint of the aft bulkhead of the methanol tank, and the bow is marked to the second cut 15 deck panel joint.

[0073] S530: Fourth cut 17 from midship to first cut 14 deck panel joint, from side to third cut 16 deck panel joint and to inner shell deck panel joint, the fourth cut 17 is opened along the marked position;

[0074] S540: First, open the fourth cut 17 on the left chord, and then hoist the left deck along the fourth cut 17 on the left chord to weld it to the surrounding structure;

[0075] Open the fourth cut 17 on the starboard side, and hoist the right deck along the fourth cut 17 on the starboard chord to weld it to the surrounding structure, thus completing the replacement of deck layer 11.

[0076] S600: All structures have completed welding and non-destructive testing. The hoisted deckhouse 12 to the top of methanol fuel tank 5 has been welded, completing the entire conversion of methanol fuel tank 5.

[0077] Example 2

[0078] A VLOC ship conversion methanol fuel tank 5 mainly includes a port compartment 71, a starboard compartment 72, a bottom compartment 2, a central longitudinal bulkhead 3, a methanol tank forward bulkhead 4, a port liquid tank 61, a starboard liquid tank 62, a deck layer 11, a deckhouse 12, and an empty compartment.

[0079] The methanol fuel tank 5 is located between the forward bulkhead 48 of the engine room and the aft bulkhead 91 of the connected cargo hold. The forward bulkhead 4 of the methanol tank is close to the aft bulkhead 91 of the connected cargo hold. A temporary staircase is arranged in the connected cargo hold, and two process openings 95 are opened on each of the port and starboard sides of the aft bulkhead 91 of the connected cargo hold. The size of the process opening 95 is bxhxr = 1000mm x 1800mm x 150mm, with its edge 50mm from the bulkhead buttress material and 200mm from the deck. The opening is reinforced with stiffeners of the same size as the bulkhead, 50mm from the upper and lower edges. The process openings 95 communicate with the methanol fuel tank 5, facilitating personnel access during the conversion. Ventilation, lighting, and engineering power and gas supplies are arranged on the side of the methanol tank. Figure 5-8 and Figure 10 The diagram shows the openings in the bulkhead of the connected cargo holds.

[0080] like Figure 1and Figure 2 As shown, the central longitudinal bulkhead 3 is located between the left compartment 71 and the right compartment 72, dividing the methanol fuel tank 5 into two independent liquid tanks, left and right. The central longitudinal bulkhead 3 is a longitudinal structure with a deck width of B=6100mm, which is connected to the aft bulkhead 45 of the methanol tank and to the forward bulkhead 4 of the methanol tank. It is connected to the forward bulkhead 48 of the engine room through the aft bulkhead 45 of the methanol tank and to the aft bulkhead 91 of the connected cargo hold through the forward bulkhead 4 of the methanol tank.

[0081] The empty compartment has two compartments, which are located on opposite sides of the left compartment 71 and the right compartment 72 respectively. The bottom 2 connects the two empty compartments. The central longitudinal bulkhead 3 divides the methanol fuel tank 5 into two independent liquid tanks, left and right. The deckhouse 12 is an independent compartment used to protect the methanol auxiliary equipment and supply equipment. The forward bulkhead 4 of the methanol tank is divided into three sections: the left forward bulkhead 41, the right forward bulkhead 42 and the central forward bulkhead 43. The deck layer 11 is divided into two sections: the left deck and the right deck. Manholes are provided on the two inner walls opposite to each other of the left compartment 71 and the right compartment 72.

[0082] like Figures 1 to 3 As shown, the forward bulkhead 4 of the methanol tank is a transverse structure with a deck width of D=2200mm, connecting to the port longitudinal bulkhead 66 of the methanol fuel tank 5 to the left and to the starboard longitudinal bulkhead 67 of the methanol fuel tank 5 to the right. The forward bulkhead 4 of the methanol tank is divided into three sections: the port forward bulkhead 41, the starboard forward bulkhead 42, and the mid-forward bulkhead 43, with the mid-forward bulkhead 43 being an adjustment section.

[0083] like Figure 1 and Figure 2 As shown, the liquid tank is a structure with a deck width of A=5500mm, a deck chamfer of R=1000mm, and an inner longitudinal wall height of C=13000mm. It is a methanol fuel tank installed in the side compartment and communicates with methanol fuel tank 5. The liquid tank is divided into two sections: the port liquid tank 61 and the starboard liquid tank 62.

[0084] All the parameters mentioned above are actual ship operation data, which are determined according to the deck structure layout, bottom section size and hoisting requirements of different ship types (especially B and D). This embodiment is only for optimization and illustration.

[0085] like Figure 1 As shown in the segmentation diagram of the methanol fuel tank 5, the bottom 2 is installed on the inner bottom plate 76 at the bottom. Two empty compartments are connected to the two sides of the inner bottom plate 76 respectively. Both the left compartment 71 and the right compartment 72 have inner longitudinal walls. Manholes are opened in the empty compartments on the reverse side of the inner longitudinal walls, realizing the surrounding protection of the empty compartments of the methanol fuel tank 5 and facilitating the placement of methanol gas-liquid detectors to detect the leakage of the methanol fuel tank 5.

[0086] Deckroom 12 is divided into several independent compartments by vertical bulkheads;

[0087] The independent compartments include an auxiliary equipment room 81, a fuel preparation room 82, a venting compartment 83, and a methanol daily use cabinet 85 (or methanol daily use compartment). The venting compartment 83 is located on the side of the fuel preparation room 82 close to the methanol daily use cabinet 85. The methanol daily use cabinet 85 is protected by an isolation compartment 84, which is connected to the fuel preparation room 82 through an opening.

[0088] This invention provides a sequence and size for deck openings, employing a method of treating the methanol fuel tank 5 structure with deck panels. The panels are assembled in sections, with openings made and the assembling of each section reinforced as they are joined, before moving on to the next section and repeating this process. This represents a significant improvement over conventional methods, which involve a single opening and overall lifting or multiple panel lifting operations. Specifically, the assembly begins with the openings on the top deck of the methanol fuel tank 5, with reinforcement added as the assembly progresses. This allows for the section-by-section conversion of the methanol fuel tank 5 on VLOC vessels without occupying dry dock space at the mooring pier. Compared to existing technologies that involve directly removing the methanol fuel tank 5 deck in a single dry dock conversion, which occupies a long dry dock period, severely limits the selection of dry dock conditions, and results in high conversion costs, this invention offers a clear advantage.

[0089] Moreover, the original technology involved directly cutting off the methanol fuel tank 5 deck in one go, dividing the bottom 2 of the tank into two parts, and then hoisting and positioning them with the assistance of personnel. This invention also enables the segmented conversion of existing VLOC ship docks into methanol fuel tank 5, solving the problems of hoisting the entire tank section with a small deck opening and tilting and positioning the unmanned tank section as a whole.

[0090] Furthermore, the existing technology directly opens process holes 95 in the methanol fuel tank 5 and overlaps with temporary ladders. After the methanol fuel tank 5 is modified, the temporary ladders are removed and the process holes 95 are sealed, making it impossible to achieve complete coating of the methanol fuel tank 5. The present invention opens process holes 95 in the adjacent cargo hold wall, ensuring personnel safety and the integrity of the coating of the methanol fuel tank 5, and improving the construction environment.

[0091] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for converting a VLOC (Vehicle-Localized Ocean Vehicle) to a methanol fuel tank (5), characterized in that, Includes the following steps: S100: Make a first cut (14) on the top deck layer (11) of the methanol fuel tank (5), lower it into the bottom of the tank (2) along the first cut (14) and weld it to the surrounding structure; S200: After the bottom (2) is welded and put into place, the central longitudinal bulkhead (3) is hoisted in and welded to the surrounding structure. The deck of the central longitudinal bulkhead (3) is also spot welded to the top deck layer (11) of the methanol fuel tank (5). Then the top deck layer (11) of the methanol fuel tank (5) is restored. S300: Make a second cut (15) on the top deck layer (11) of the methanol fuel tank (5), hoist the front bulkhead (4) of the methanol tank along the second cut (15), first assemble the two sections of the left front bulkhead (41) and the right front bulkhead (42), then hoist the front bulkhead (43) of the adjustment section, weld the three sections to the surrounding structure after they are in place, and also spot weld them to the top deck layer (11) of the methanol fuel tank (5), and then reassemble the top deck layer (11) of the methanol fuel tank (5). S400: Make a third cut (16) on the top deck layer (11) of the methanol fuel tank (5), lower the liquid tank into the tank along the third cut (16) and weld it to the surrounding structure, and at the same time spot weld it to the top deck layer (11) of the methanol fuel tank (5), and then repair the top deck layer (11) of the methanol fuel tank (5). S500: Make a fourth cut (17) on the top deck layer (11) of the methanol fuel tank (5), and hoist the deck layer (11) along the fourth cut (17) to weld it to the surrounding structure; S600: All structures are welded and non-destructive testing is completed. The deckhouse (12) is hoisted to the top of the methanol fuel tank (5) and welded, completing the modification of the entire methanol fuel tank (5).

2. The method for converting a VLOC vessel into a methanol fuel tank (5) according to claim 1, characterized in that, Step S100 includes: S110: A longitudinal reinforcing structure (13) and a transverse reinforcing structure (13) are provided around the first cut (14), and the width B of the first cut (14) is consistent with the deck width on the central longitudinal bulkhead (3); The longitudinal reinforcement structure (13) is installed on the side longitudinal girders on both sides of the first cut (14), and the two ends extend to the front bulkhead (48) of the engine room and the rear bulkhead (91) of the connected cargo hold respectively. The transverse reinforcement structure (13) is installed between the rear bulkhead (45) of the methanol tank, the rear bulkhead (91) of the connected cargo hold and the two sets of longitudinal reinforcement structures (13), and they are connected to each other to form a rectangular reinforcement frame. S120: Then cut along the joint of the longitudinal girder beside the deck and the aft bulkhead (45) of the methanol tank and the aft bulkhead (91) of the connected cargo hold.

3. The method for converting a VLOC ship into a methanol fuel tank (5) according to claim 1, characterized in that, Step S200 includes the following steps: S210: Draw the bottom line (2) of the methanol fuel tank (5) at the bow. Make a clear mark with paint at the center of the bottom line. Spot weld a baffle (96) with an angle of α=75° at the edge of the bottom line. S220: Make a clear mark on the center of the bottom (2) with flat iron and weld lifting lugs on the front cross section (46) of the bottom. Use the first crane (92) to hang on the lifting lugs on the front cross section (46) of the bottom to lift the bottom (2). Align the rear cross section (47) of the bottom with the longitudinal direction of the first cut (14) and lift it into the compartment. S230: The bottom (2) is turned 90° inside the cabin, and the second crane (93) is used to lift it up by hanging it on the lifting lug of the rear cross section (47) of the bottom of the cabin, and then it is turned over longitudinally; S240: The first crane (92) and the second crane (93) lowered down simultaneously, approaching the height of the baffle (96). After confirming that the flat iron of the bilge (2) coincides with the center line paint mark of the landing line, the bilge (2) continued to be lowered. With the help of the slope of the methanol tank rear bulkhead (45), the slope of the port longitudinal bulkhead (66), the slope of the starboard longitudinal bulkhead (67), and the baffle (96), the bilge (2) was lowered until it was in place.

4. The method for converting a VLOC ship to a methanol fuel tank (5) according to claim 2, characterized in that, The width D of the second cut (15) in step S300 is the same as the deck width of the methanol tank front bulkhead (4), and it is cut along the closure seam of the methanol tank front bulkhead (4) between the crossbeam and the connected cargo tank rear bulkhead (91).

5. The method for converting a VLOC vessel into a methanol fuel tank (5) according to claim 1, characterized in that, In step S400, the width A of the third cut (16) is the same as the width of the deck on the liquid tank, and the height C of the third cut (16) is the same as the height of the inner longitudinal wall (75) on the liquid tank. The third cut (16) is provided with a chamfer R and is cut along the closing seam of the left liquid tank (61) and the right liquid tank (62).

6. The method for converting a VLOC vessel into a methanol fuel tank (5) according to claim 1, characterized in that, Step S500 includes: S510: Draw the fourth cut (17) opening line on the top deck layer (11) of the methanol fuel tank (5); S520: The fourth cut (17) is marked on the stern to the joint of the deck panel of the methanol tank aft bulkhead (45), and the bow is marked to the joint of the deck panel of the second cut (15); S530: Fourth cut (17) from midship to first cut (14) deck panel joint, from side to third cut (16) deck panel joint and to inner shell deck panel joint, and the fourth cut (17) is made along the marked position. S540: First, open the fourth cut (17) on the left chord, and then hoist the left deck along the fourth cut (17) to weld it to the surrounding structure; Open the fourth cut on the starboard side (17) again, and hoist the right deck along the fourth cut on the starboard chord (17) to weld it to the surrounding structure, thus completing the replacement of the deck layer (11).

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