Construction method of MARK III type liquefied natural gas transport ship

Abstract

A construction method of a MARK III type liquefied natural gas transport ship is characterized in that a small dock or an unoccupied area of the dock is utilized, a watertight structural design meeting the structural strength is adopted, and the MARK III type liquefied natural gas transport ship is divided into two sections to be constructed (a bow half section and a stern half section) by taking an isolation void compartment of any cargo compartment as a boundary. After the ballast tank strength test is completed, the whole ship is formed in a floating butt joint mode, and construction of all working procedures of a cargo containment system is carried out after butt joint. After the main ship body is formed and the shaft rudder system is constructed, the whole ship floats out of the dock, construction of the remaining cargo wall system is completed in the dock mooring stage, and the underwater construction period is shortened. According to the method, the liquid cargo natural gas transport ship is built by using the small dock and the free area of the dock, a cargo containment system has construction conditions in advance, the building period of the whole ship is shortened, core resources of ship building are efficiently utilized, the total period of ship building is shortened, and the building cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of MARK Ⅲ type ship design and construction, and particularly relates to a construction method of a MARK Ⅲ type liquefied natural gas transport ship. BACKGROUND

[0002] The construction core of the MARK Ⅲ type liquefied natural gas transport ship lies in the construction of a cargo containment system (hereinafter referred to as a containment system). The construction process of the cargo containment system is complex, difficult and long, usually 8-12 months. The construction period of the cargo containment system accounts for about 1 / 2 of the whole ship construction period, and the underwater period is long, occupying a large amount of wharf resources.

[0003] The conventional construction method of the liquefied natural gas transport ship is to construct the whole ship in the dock, that is, to take the length direction of the ship as the reference section, to longitudinally and transversely close the sections, and finally to form the whole ship. During the whole closing process, the ship cannot be ballasted and moved due to the welding digestion of the closing joint, otherwise there is a risk of damage to the ship structure.

[0004] According to the process flow, before the construction of the containment system, the strength test of the adjacent ballast tank needs to be completed to prevent the deformation of the cargo tank inner shell caused by the change of the ballast state. Due to the limitation of the ground bearing capacity and the limitation of the reaction force on the ship structure, the conventional ballast tank strength test cannot be carried out during the construction stage in the dock, and therefore needs to be carried out in the water, so it needs to be carried out in the wharf. The construction period of the whole ship in the wharf is 12-16 months, and the maintenance cost of equipment and pipeline system is greatly increased compared with the conventional ship construction, which increases the cost of ship construction.

[0005] At the same time, the conventional liquefied natural gas transport ship needs a suitable length and width of the dock to carry out the construction, so when the liquefied natural gas transport ship is constructed, the length of the dock is insufficient, the small dock cannot be constructed, and the large dock is constructed with a waste of space. However, due to the sudden increase in demand and orders for MARK Ⅲ type liquefied natural gas transport ships in recent years, in order to save cost and speed up construction, the present application provides a construction method of MARK Ⅲ type liquefied natural gas transport ship which can reasonably utilize the dock and shorten the construction period. SUMMARY

[0006] To solve the above problems, the present application provides a construction method of MARK Ⅲ type liquefied natural gas transport ship, which aims to reasonably utilize the dock, shorten the construction period and save the cost, and the technical scheme adopted is: A construction method of MARK Ⅲ type liquefied natural gas transport ship, characterized in that the specific operation is as follows: S1: The hull is divided into two halves, namely the bow half and the stern half, by the partitioned empty cabin between the two cargo cabins in the middle of the hull, and on this basis, the bow half and the stern half are further divided into a plurality of bow sub-sections and a plurality of stern sub-sections.

[0007] S2: The bow sub-sections and the stern sub-sections are painted using the empty space in the dock or small dock space, and after painting, the plurality of bow sub-sections are assembled to form the bow section and the plurality of stern sub-sections are assembled to form the stern section in the dock.

[0008] S3: The bow section and the stern section are floated and launched, the floating state of the bow half and the stern half under the condition of water pressure in the ballast tank is calculated, then the diagonal water pressure method is adopted to test the strength of the ballast tank, and the hull structure strength of the bow half and the stern half during the strength test is calculated, if there is a large stress concentration area, the structure of this area is strengthened to ensure that no structural deformation occurs during the strength test.

[0009] S4: After the strength test, the bow half and the stern half are floated into the dock, the bow half and the stern half are leveled and docked to form the whole ship, the stern half is landed first, and the bow half is landed after aligning with the stern half to ensure the hull line type.

[0010] S5: The cargo containment system construction is carried out in the dock, and at the same time, the engine room, bow hull digestion, painting construction, shaft rudder system, deck low temperature pipe system construction are carried out, the flatness is measured with a 3-meter ruler and a 1-meter ruler before the cargo containment system construction, and the gap is required to be less than or equal to 4mm.

[0011] If the construction period is more than 100 days, the cargo containment system in the dock at least completes to the end of the "top bridge plate process", that is, 50% of the work of the cargo containment system is completed, if the construction period is less than 100 days, the cargo containment system in the dock only proceeds to the "insulation board construction" stage, that is, 25% of the work of the cargo containment system is completed.

[0012] S6: The wharf outfitting, the remaining processes of the cargo containment system, the trial voyage and the delivery of the ship are carried out.

[0013] The above-mentioned construction method of the MARK III type liquefied natural gas carrier further has ballast tanks symmetrically arranged on the left and right sides of the hull, and the partitioned empty cabin between the two cargo cabins in the middle of the hull is divided into front and back, and the ballast tanks are also divided into front and back.

[0014] The above-mentioned construction method of the MARK III type liquefied natural gas carrier further has adjacent ballast tanks sharing a bulkhead, and a temporary watertight bulkhead is designed in the ballast tank lacking a bulkhead when the ballast tank strength test is carried out.

[0015] The MARK III type liquefied natural gas transport ship construction method further has the following further improvements: when the difference between the bow draft and the stern draft exceeds 3 meters during the ballast tank strength calculation process, the number of segment assembly can be reduced to reduce the difference between the drafts during the ballast tank strength test.

[0016] The MARK III type liquefied natural gas transport ship construction method further has the following further improvements: the adjacent outfitting parts of the cargo hold inner shell plate need to be installed and the fire operation needs to be completed, and the outfitting parts of the rear wall of the bow half section and the front wall of the stern half section need to be protected and blocked.

[0017] The MARK III type liquefied natural gas transport ship construction method further has the following further improvements: the hull structure strength of the bow half section and the stern half section during the strength test can be analyzed by using the Patran finite element analysis software to analyze the pressure change of the hull structure after the ballast tank is filled with water.

[0018] The MARK III type liquefied natural gas transport ship construction method further has the following further improvements: the MARK III type liquefied natural gas transport ship construction method adopts a watertight structure design meeting the structural strength, and divides the ship into a bow half section and a stern half section for construction, efficiently utilizes the core resources of the shipyard, such as a small dock (the length is not enough to build a whole ship) and a dock idle area (the length or width of the dock is larger than the ship under construction, and the remaining area), and uses the resources for building a liquefied natural gas transport ship, thereby increasing the number of shipbuilding and increasing the shipyard income. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a top view structural schematic diagram of the MARK III type liquefied natural gas transport ship; Figure 2 is a side view structural schematic diagram of the ship body divided into a bow half section and a stern half section; Figure 3 is a construction process schematic diagram of the present application. DETAILED DESCRIPTION

[0020] The present application will be further described in combination with the drawings.

[0021] A MARK III type liquefied natural gas transport ship construction method, a 175,000-ton conventional liquefied natural gas transport ship, such as Figure 1As shown, the MARK III liquefied natural gas transport ship has four cargo holds, and an isolation empty hold is arranged between adjacent cargo holds. From the bow to the stern, the four cargo holds are numbered 1 to 4, and a first isolation empty hold is arranged in front of the first cargo hold. Isolation empty holds are arranged between the cargo holds, and a last isolation empty hold is arranged behind the fourth cargo hold. From the bow to the stern, five isolation empty holds are arranged, numbered 1 to 5. Ballast holds are symmetrically arranged at the left and right sides of the ship, and are numbered 4 pairs from the bow to the stern, numbered 1P, 1S, 2P, 2S, 3P, 3S, 4P, and 4S. The “P” represents the left side, and the “S” represents the right side. Adjacent ballast holds share a bulkhead. For example, the rear bulkhead of the 1P ballast hold is also the front bulkhead of the 2P ballast hold. The adjacent ballast holds of the first cargo hold are the 1P / S ballast holds, the adjacent ballast holds of the second cargo hold are the 2P / S ballast holds, and so on. Figure 3 As shown, the specific construction process is as follows: S1: The ship is divided at the isolation empty hold between the second cargo hold and the third cargo hold in the middle of the ship, to form a bow half and a stern half, as shown in FIG. 1B. Figure 2 As shown, the first cargo hold, the second cargo hold, the first isolation empty hold, the second isolation empty hold, the 1P ballast hold, the 1S ballast hold, the 2P ballast hold, and the 2S ballast hold form the bow half, and the third cargo hold, the fourth cargo hold, the third isolation empty hold, the fourth isolation empty hold, the 3P ballast hold, the 3S ballast hold, the 4P ballast hold, and the 4S ballast hold form the stern half. On this basis, the bow half and the stern half are further divided into a plurality of bow sub-segments and a plurality of stern sub-segments. After the steel plates are cut, the segments are manufactured, to form a plurality of segments suitable for segment yard construction (the size of the segment yard determines the size of the segment design), and to meet the segment transportation requirements (the transportation tool and the transportation channel determine the weight of the single segment and the size of the segment design). For example, the total number of bow sub-segments and stern sub-segments of a 175,000-ton liquefied natural gas transport ship is 350. It should be noted that, in order to ensure that the ship is divided into a bow half and a stern half, the “front” and the “rear” refer to the direction of the bow as the front and the direction of the stern as the rear.

[0022] Because the cargo hold of the liquefied natural gas ship is different from other ships, the construction of the cargo containment system has very high requirements for the cleanliness of the inner wall of the cargo hold, the humidity in the hold, and the special paint for the inner wall of the cargo hold. If the ship is divided at the cargo hold, the cargo hold will be filled with water during the strength test of the ballast hold, and the inner wall of the cargo hold will be difficult to clean and the paint on the inner wall of the cargo hold will be easily damaged after the subsequent construction of the cargo containment system. The dehumidification workload will increase, and the conditions for the construction of the cargo containment system will be difficult to meet. Therefore, the ship is divided at the isolation empty hold between the cargo holds, to ensure the integrity of the structure of the cargo hold.

[0023] S2: Use the empty space of the dock, or the small dock space, to paint the bow sub- segment and the stern sub-segment. After painting, the multiple bow sub-segments are assembled in the dock to form a bow segment, and the multiple stern sub-segments are assembled in the dock to form a stern segment.

[0024] S3: The bow segment and the stern segment are floated and launched. The floating state of the bow half-segment and the stern half-segment under the condition of water pressure in the ballast tank is calculated. Then, the first step 1P ballast tank and the second step 2S ballast tank are used to simultaneously perform the ballast tank strength test. The second step 1S ballast tank and the second step 2P ballast tank are used to simultaneously perform the ballast tank strength test. This diagonal water pressure method reduces the ship deformation stress during the ballast tank strength test. The ship structure strength of the bow half-segment and the stern half-segment during the strength test is calculated. The Patran finite element analysis software can be used for stress analysis to analyze the pressure change of the ship structure after the ballast tank is pressurized. If a large stress concentration area appears, the structure of this area is strengthened to ensure that no structural deformation occurs during the strength test. If the calculation process finds that the bow draft and the stern draft differ greatly (more than 3 meters, since the water pressure is symmetrical on the left and right, the draft difference between the left and right sides is usually less than 1 meter), the number of segment closures can be reduced to reduce the draft difference during the ballast tank strength test. For a 175,000-ton liquefied natural gas carrier, 4 segments (200 tons) of the bow half-segment and 6 segments (300 segments) of the stern half-segment are reduced to close, so that the draft difference during the ballast tank strength test is within 2 meters.

[0025] In order to ensure that the cargo containment system construction can be carried out as soon as possible after the strength test, the adjacent fittings of the cargo hold inner plate need to be installed and the fire operation needs to be completed. The fittings of the bow half-segment rear wall and the stern half-segment front wall, which are originally in the No. 3 isolated empty tank or the bottom pipe tunnel, need to be protected and plugged to prevent corrosion and water from entering the bottom pipe tunnel. During the ballast tank strength test of the 175,000-ton liquefied natural gas carrier, the bow draft and the stern draft are as high as 8 meters. The fittings below 10 meters, pipe tunnels, etc. need to be protected, and 2 meters are reserved to avoid the impact of surges.

[0026] S4: After the strength test, the bow half-segment and the stern half-segment are floated into the dock. The bow half-segment and the stern half-segment are leveled and docked to form a whole ship. During the floating and landing process, the stern half-segment usually lands first because it contains more equipment and has a large draft. The bow half-segment lands later in the process of aligning with the stern half-segment, and the ship line type must be ensured. The advantage of setting the docking interface in the isolated empty tank is that the docking interface welding process will not affect the cargo hold inner wall structure. The cargo hold inner wall flatness requirement of the cargo containment system construction team is extremely high (the cargo hold inner wall of the liquefied natural gas carrier needs to be measured for flatness with a 3-meter ruler and a 1-meter ruler before the cargo containment system construction. The gap is required to be less than or equal to 4 mm. There is no flatness requirement for conventional ships).

[0027] S5: In the dock, the cargo containment system construction is carried out, and the cabin, bow hull digestion, painting construction, shaft rudder system and deck low temperature pipe system construction are carried out. Before the cargo containment system construction, the flatness needs to be measured by using a 3-meter ruler and a 1-meter ruler, and the gap is required to be less than or equal to 4 mm.

[0028] During the "top bridge plate process" of the cargo containment system, the ship is not allowed to be loaded, so if the construction period of the whole ship in the dock cannot complete the "top bridge plate process", it is only carried out to the "insulation plate construction" stage in the dock, that is, 25% of the work of the cargo containment system is completed. If the construction period is sufficient (more than 100 days), at least the "top bridge plate process" is completed in the dock, that is, 50% of the work of the cargo containment system is completed.

[0029] S6: Terminal outfitting, trial voyage and delivery are carried out, and the remaining processes of the cargo containment system construction are carried out. If the "top bridge plate process" of each cabin is completed in the dock stage, the cargo containment construction is completed before launching 50%, and the remaining process construction needs a period of 4 months underwater, which reduces the underwater period by 4 months. If the construction period in the dock stage is shorter, the cargo containment construction is completed before launching 25%, and the remaining process construction needs a period of 6 months underwater, which reduces the underwater period by 2 months.

[0030] The whole ship construction is divided into two directions from the middle to the front and rear, and the "two large sections" (especially "bow half section" and "stern half section") are constructed, that is, four directions are combined, which is an efficient construction mode, and the dock hull combination period is shortened by more than 1 month. The efficiency of the crane is improved, and the construction period is shortened.

[0031] The whole ship construction mode needs to carry out the cargo containment system construction after the completion of the construction in the dock. But the "two large section" construction mode is to float into the dock after completing the strength test of all the ballast tanks of the bow half section and the stern half section, and then the two large sections are docked. After docking, the cargo containment system construction can be carried out, and the cargo containment system construction process is moved to the dock stage, which shortens the underwater period by 2-4 months. The whole ship construction period is effectively shortened.

Claims

1. A method of constructing a MARK III type liquefied natural gas carrier, characterized by, The specific operation is as follows: S1: The hull is divided into two halves, namely the bow half and the stern half, by taking the isolated empty cabin between the two cargo cabins in the middle of the hull as the boundary, and on this basis, the bow half and the stern half are further divided into a plurality of bow sub-segments and a plurality of stern sub-segments; S2: The bow sub-segments and the stern sub-segments are painted using the empty space of the dock or the small dock space, and after painting, the plurality of bow sub-segments are assembled to form a bow segment and the plurality of stern sub-segments are assembled to form a stern segment in the dock; S3: The bow segment and the stern segment are floated and launched, the floating state of the bow half and the stern half under the condition of water pressure in the ballast tank is calculated, then the diagonal water pressure method is adopted to test the strength of the ballast tank, and the hull structure strength of the bow half and the stern half during the strength test is calculated, if there is a large stress concentration area, the structure of the area is strengthened to ensure that the structure will not be deformed during the strength test; S4: After the strength test, the bow half and the stern half are floated into the dock, the bow half and the stern half are leveled and docked to form the whole ship, the stern half is landed on the dock first, and the bow half is landed on the dock after aligning with the stern half to ensure the hull line type; S5: The cargo containment system construction is carried out in the dock, and at the same time, the engine room, the bow hull digestion, the painting construction, the shaft rudder system and the deck low temperature pipe system construction are carried out, the flatness is measured by using 3-meter ruler and 1-meter ruler before the cargo containment system construction, and the gap is required to be less than or equal to 4mm; If the construction period is more than 100 days, the cargo containment system in the dock is completed to the end of the "top bridge plate process", that is, 50% of the work of the cargo containment system is completed, if the construction period is less than 100 days, the cargo containment system in the dock is only completed to the "insulation plate construction" stage, that is, 25% of the work of the cargo containment system is completed; S6: The wharf outfitting, the remaining processes of the cargo containment system, the trial voyage and the delivery of the ship are carried out.

2. A method of constructing a MARK III type LNG carrier according to claim 1, wherein The left and right sides of the hull are symmetrically provided with ballast tanks, and the isolated empty cabin between the two cargo cabins in the middle of the hull is divided into front and back, and the ballast tanks are also divided into front and back.

3. A method of constructing a MARK III type LNG carrier according to claim 1, wherein The adjacent ballast tanks share a bulkhead, and a temporary watertight bulkhead is designed in the ballast tank which lacks a bulkhead during the ballast tank strength test.

4. A method of constructing a MARK III type LNG carrier according to claim 1, wherein If the difference between the bow draft and the stern draft exceeds 3 meters during the ballast tank strength calculation, the number of segment assembly can be reduced to reduce the draft difference during the ballast tank strength test.

5. A method of constructing a MARK III type LNG carrier as claimed in claim 1, wherein, The adjacent outfitting parts of the cargo cabin inner plate need to be installed and the fire operation needs to be completed, and the outfitting parts of the bow half rear wall and the stern half front wall need to be protected and plugged.

6. A method of constructing a MARK III type LNG carrier according to claim 1, wherein The hull structure strength of the bow half and the stern half during the strength test can be analyzed by using Patran finite element analysis software to analyze the pressure change of the hull structure after the ballast tank is pressurized.

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