A construction method of an LNG ship with a MARK III fuel tank

Abstract

A construction method for an LNG ship with a MARK III fuel tank divides the LNG ship into a bow section, a midship section, and a stern section. The MARK III fuel tank is located within the midship section. Based on the integrity of the MARK III fuel tank, the midship section is first divided, and then, with the integrity of the engine room as the criterion, the bow section and the stern section are divided. The bow section, midship section, and stern section are respectively constructed in one or more small shipyards. The midship section is constructed first. After the bow section and the stern section are completed, they are joined together by welding in a large shipyard to form a complete hull. In the present invention, the insulation layer construction work of the MARK III membrane tank is completed during the sub-assembly construction stage. After the bow section, midship section, and stern section are joined together, other construction work such as the stainless steel welding of the MARK III membrane tank is continued. By advancing the construction of the MARK III membrane tank, the occupation of production resources of the large shipyard and the mooring dock is reduced, the production efficiency is improved, the shipyard output is increased, and the single-ship construction cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of offshore LNG design, construction and transportation, and particularly relates to a construction method of an LNG ship with a MARK III type fuel tank. Background Art

[0002] For ultra-large ships such as ultra-large oil tankers and ultra-large container ships over 250 meters, currently mainly two large-section general assembly construction is adopted, that is, the ship is divided into a bow section and a stern section, which are respectively constructed at different locations, and finally the bow and stern sections are joined together in a large shipyard. Due to the scale limitation of ultra-large ships, they can only be constructed in a large shipyard. LNG fuel, as an energy-saving and environment-friendly energy source, can reduce the carbon emissions, sulfur emissions and nitrogen emissions of ships, and can meet the requirements of various international specifications. LNG-powered ships are occupying an increasing market share. Large ships have high energy consumption and need to be equipped with LNG fuel tanks with large tank volumes. Usually, MARK III type thin film tanks are used as fuel tanks.

[0003] For LNG-powered ships using MARK III type thin film tanks as fuel tanks, since the thin film tanks must rely on the hull structure to paste the insulation layer and weld, construction needs to be carried out after the hull structure supporting the LNG fuel tank is completed, and the construction period of the thin film tank enclosure system is relatively long. Adopting the current two-large-section general assembly construction plan, the thin film tank needs to start construction after the whole ship is joined together and needs to start from the time when the ship is joined together until the mooring stage. The increased construction period needs to occupy the large shipyard or the mooring wharf.

[0004] The production resources of the large shipyard or mooring wharf of the shipyard are limited. Occupying the large shipyard or mooring wharf for a long time will lead to a reduction in the utilization rate of production resources, resulting in a reduction in the output of the shipyard and an increase in the construction cost. Summary of the Invention

[0005] To solve the above problems, the present invention provides a construction method of an LNG ship with a MARK III type fuel tank, and the technical solution adopted is as follows:

[0006] A construction method of an LNG ship with a MARK III type fuel tank divides the LNG ship into a bow section, a midship section and a stern section. The MARK III type fuel tank is located in the midship section. Taking the integrity of the MARK III type fuel tank as the standard, the midship section is divided first, and then taking the integrity of the engine room as the standard, the bow section and the stern section are divided. The bow section, the midship section and the stern section are respectively constructed in one or more small shipyards, and the midship section is constructed first.

[0007] After the midship section is completed, it leaves the small dry dock by floating and is towed into the large dry dock by a tugboat. After the bow section and the stern section are completed, they leave the small dry dock or the shipbuilding berth by floating or launching and are towed into the large dry dock by a tugboat. In the large dry dock, they are stably placed on the dock blocks in the order of the bow section, the midship section, and the stern section, and the seawater in the large dry dock is drained. The bow section, the midship section, and the stern section are joined together by welding to form a complete hull.

[0008] For the above-mentioned construction method of an LNG ship with a MARKIII fuel tank, further, in the small dry dock, the MARKIII fuel tank is fixed in the completed midship section, and the steps are as follows:

[0009] S1: Use a high-precision laser line marker to measure each surface of the MARKIII fuel tank, calculate the deviation values of the center lines of each surface, and fit the best reference loop line. S2: The MARKIII fuel tank is equipped with a base, and the positions of the bases are the intersection points of each grid line. Determine the positions for installing studs according to the intersection points.

[0010] S3: Place the MARKIII thin-film fuel tank in the midship section according to the reference loop line. Apply epoxy resin on the hull structure adjacent to the MARKIII thin-film fuel tank in the midship section, and insulation modules are fixedly installed on the epoxy resin.

[0011] S4: The MARKIII thin-film tank consists of a stainless-steel film, a main screen wall, and a secondary screen wall from the inside out. The secondary screen is composed of two layers of fiberglass cloth and one layer of aluminum foil, and the secondary screen wall is bonded to the insulation module with glue.

[0012] For the above-mentioned construction method of an LNG ship with a MARKIII fuel tank, further, after the joining is completed, conduct a tightness test on the main screen wall of the MARKIII fuel tank. After the test is qualified, hoist the pump tower to the MARKIII fuel tank for installation.

[0013] For the above-mentioned construction method of an LNG ship with a MARKIII fuel tank, further, the coating gap of the epoxy resin in step S2 should meet the technical requirements of the manufacturer.

[0014] For the above-mentioned construction method of an LNG ship with a MARKIII fuel tank, further, the insulation model in step S3 is fixed to the hull structure by bolts.

[0015] For the above-mentioned construction method of an LNG ship with a MARKIII fuel tank, further, in step S4, it is necessary to control the temperature in the tank between 20 and 30 degrees Celsius, the humidity within 70%, and the tank should be kept dust-free.

[0016] For the above - mentioned method for building an LNG ship with a MARKIII - type fuel tank, further, when the bow section, mid - ship section, and stern section are floating, it is necessary to ensure that the mid - ship section is in a level - floating state.

[0017] For the above - mentioned method for building an LNG ship with a MARKIII - type fuel tank, further, after the overall ship is assembled, check whether the MARKIII - type secondary shield that has been constructed is complete. If there is any damage, it should be repaired or corrected.

[0018] For the above - mentioned method for building an LNG ship with a MARKIII - type fuel tank, further, draw grid lines on the outer surface of the stainless - steel film, and the grid lines correspond one - by - one to the corrugations of the stainless - steel film.

[0019] For the above - mentioned method for building an LNG ship with a MARKIII - type fuel tank, further, when scribing the dihedral angle of the grid lines, the axis error is not more than ±2 mm, and when scribing on a plane, the axis error is not more than ±1 mm.

[0020] The present invention will adopt a general assembly construction method in three major sections to build a large LNG - powered ship, that is, divide the LNG - powered ship into three general sections: bow, mid - ship, and stern. The MARKIII - type thin - film fuel tank section should be included in the mid - ship general section. Since the construction time of the MARKIII thin - film tank is relatively long, the mid - ship general section containing the MARKIII thin - film tank starts construction first, and the bow and stern general sections start construction subsequently. After the mid - ship general section completes the overall erection, the construction work of laying the insulation layer of the MARKIII - type thin - film tank starts. The entire insulation layer laying construction work should be completed during the construction process of the mid - ship general section. When the construction of the bow, mid - ship, and stern general sections is all completed, they are assembled in a large shipyard and the construction continues. After completing the construction work in the shipyard, the mooring - stage construction continues until the ship is completed.

[0021] In shipyards, there are many construction sites such as small shipyards and shipbuilding berths that can build large general sections of large ships, while the production resources of large shipyards and mooring docks that can build ultra - large ships are relatively limited. Aiming at the problem that the long construction period of the MARKIII - type thin - film fuel tank leads to the occupation of large shipyards and mooring docks, the present invention separately divides the part containing the MARKIII - type thin - film fuel tank into a mid - ship general section, advances the construction process of the MARKIII - type thin - film tank, reduces the occupation of production resources of large shipyards and mooring docks, improves production efficiency, and saves costs.

[0022] The MARK III thin-film tank needs to be built relying on the hull structure and has a long construction period. In the present invention, the MARK III thin-film tank part is separately divided into a total section, and construction is preferentially started and completed for erection, creating the construction conditions for the MARK III thin-film tank. During the total section construction stage, the insulation layer construction work of the MARK III thin-film tank is completed; then, after the bow section, midship section, and stern section are joined together, other construction work such as stainless steel welding of the MARK III thin-film tank is continued. The construction of the MARK III thin-film tank is advanced, reducing the occupation of production resources of large shipyards and mooring docks, improving production efficiency, increasing the output of the shipyard, and reducing the construction cost per ship. Specific Embodiments

[0023] The hull is divided into sections according to the location of the fuel tank of the ultra-large LNG-powered ship. When dividing the sections, priority is given to considering the integrity of the MARK III fuel tank, and secondly, the integrity of the engine room. The ultra-large LNG-powered ship is divided into a bow section, a midship section, and a stern section.

[0024] The large midship section should contain the LNG fuel tank and construction should be preferentially started. The bow and stern total sections start construction slightly later.

[0025] The bow section, midship section, and stern section are further subdivided and divided into several sections according to the hull structure. To make full use of the section assembly line resources, the sections are preferably made into sections about 20 meters long.

[0026] According to the design drawings, in the order of the large midship section first and then the bow section and stern section, the construction of all sections is completed in the section workshop.

[0027] To make full use of the crane in the small shipyard, the completed sections are assembled into a total section not greater than 90% of the rated load of the crane.

[0028] Select the bottom total section of the midship total section as the foundation, join together the various total sections of the large midship section in the small shipyard, build the hull structure of the large midship section, and after completion, inspect the surface flatness of the adjacent hull structure of the MARK III fuel tank and correct the flatness of the parts that do not meet the manufacturer's construction standards.

[0029] Using a high-precision laser line marker, measure each surface of the MARK III fuel tank, calculate the deviation values of the center lines of each surface, and fit the best reference loop line, laying a good foundation for the high-precision installation of the fuel tank.

[0030] The base position of the MARK III fuel tank is the intersection point of each grid line, and the positions for installing studs are demarcated according to the intersection points.

[0031] Build an installation platform and scaffolding according to the internal shape of the MARK III fuel tank to prepare for the next construction step.

[0032] Using the installation platform and scaffolding, first apply epoxy resin on the adjacent hull structure of the MARK III membrane fuel tank. The coating gap of the epoxy resin should meet the manufacturer's technical requirements.

[0033] Then, install the insulation module on the epoxy resin, install it to the hull structure by bolts, and keep the structure stable.

[0034] The secondary shield of the MARKIII membrane cabin is a composite material consisting of 2 layers of glass cloth and 1 layer of metal aluminum foil, which is bonded to the insulation module with glue. To improve the bonding effect, the temperature in the cabin needs to be controlled between 20 and 30 degrees Celsius, the humidity within 70%, and the cabin should be kept dust-free.

[0035] The completion of the secondary shielding construction means the completion of the construction of the large section of the midship in the small dock.

[0036] The bow section and the stern section were assembled and constructed in other small docks or slipways. Since the construction of the bow section and the stern section started later, their assembly completion time was equivalent to the construction time of completing the secondary shielding of the midship section.

[0037] After the bow section, midship section and stern section are completed, the midship section will leave the small dock by floating and be towed to the large dock by a tugboat. When the midship section floats, it is necessary to strictly control the floating state of the midship section to ensure that it is in a flat floating state to avoid hull deformation affecting the construction accuracy of the MARK III fuel tank secondary shielding.

[0038] After the large bow section and the large stern section are built in a small dock or slipway, they are transferred from the production site to the sea by floating or launching, adjusted to a horizontal floating state, and towed to a large dock by a tugboat.

[0039] During the construction of the bow section, midship section and stern section, the accuracy and margin are strictly controlled. The three sections are arranged in the order of bow, midship and stern in the same large dock, and the sea water in the large dock is drained so that the ship can sit stably on the piers of the large dock. The three sections are welded together to form a complete hull.

[0040] After the whole ship is assembled, check whether the construction integrity of the completed MARK III secondary shielding is damaged. If damaged, it should be repaired or corrected.

[0041] Conduct the secondary shielding layer tightness test, including vacuum box test, sound test and secondary layer tightness test. The vacuum box test is used to check the adhesion effect. The sound test and secondary layer tightness test are used to check whether there are leaks in the fuel tank.

[0042] Before the formal installation of the main film wall, it is necessary to scribe the stainless-steel film. The purpose is to ensure that the corrugations of the film on each surface can correspond one by one. The scribing accuracy requirement is high. When scribing the dihedral angle, the axis error ≤ ±2 mm, and when scribing the plane, the axis error ≤ ±1 mm.

[0043] The welding process of the main wall should strictly control the accuracy to ensure that the stainless-steel corrugations correspond one by one. After all the welds are completed, they should be polished to remove harmful residues.

[0044] Conduct the tightness test of the main shielding layer, including the ammonia test and the main layer pressure test, to check whether there are leakage points in the main wall.

[0045] Lift and install the pump tower of the MARKIII film cabin. After the installation of the pump tower is completed, remove the scaffolding, clean the fuel tank and complete the sealing of the cabin. The construction of the MARKIII fuel tank is completed.

[0046] Put seawater into the large shipyard and pump in ballast water as needed to make the ship float in a level state, and then move it to the dock by tugs for mooring construction.

[0047] Continue the construction in the moored state, complete the processes such as LNG fuel filling, equipment commissioning, sea trials, etc., and complete the construction of the large LNG-powered ship.

[0048] If the MARKIII fuel tank is small enough, the area of the midship section can be reduced as much as possible. Based on this super-large section, the fore half section or the aft half section can be built using the traditional method of assembling two large sections. This plan requires that the super-large section of the fuel tank be small enough to be within the working range of the gantry crane, and the design of this super-large section should be completed as early as possible.

Claims

1. A construction method for an LNG ship with a MARK III fuel tank, characterized in that: The LNG carrier is divided into the bow section, the midship section and the stern section. The MARK III type fuel tank is located within the midship section. Taking the integrity of the MARK III type fuel tank as the standard, the midship section is first divided, and then, taking the integrity of the engine room as the criterion, the bow section and the stern section are divided. The bow section, the midship section and the stern section are respectively constructed in one or more small shipyards, and the midship section is constructed first; After the construction of the midship section is completed, it leaves the small shipyard by floating and is towed into the large shipyard by a tugboat. After the construction of the bow section and the stern section is completed, they leave the small shipyard by floating or launching and are towed into the large shipyard by a tugboat. In the large shipyard, they are stably seated on the dock piers in the order of the bow section, the midship section and the stern section, and the seawater in the large shipyard is drained. The bow section, the midship section and the stern section are joined together by welding to form a complete hull; In the small shipyard, the MARK III type fuel tank is fixed within the constructed midship section. The steps are as follows: S1: Using a high-precision laser alignment instrument, measure each surface of the MARK III type fuel tank, calculate the deviation values of the center lines of each surface, and fit the best reference circular line; S2: The MARK III type fuel tank is equipped with a base, and the positions of the bases are the intersection points of each grid line. Determine the positions for installing studs according to the intersection points; S3: According to the reference circular line, place the MARK III type fuel tank within the midship section. Apply epoxy resin on the hull structure adjacent to the MARK III type fuel tank in the midship section, and insulating modules are installed and fixed on the epoxy resin; S4: The MARK III type fuel tank consists of a stainless steel film, a main screen wall and a secondary screen wall from the inside out. The secondary screen is composed of two layers of fiberglass cloth and one layer of aluminum foil, and the secondary screen wall is bonded to the insulating module by glue.

2. The construction method of an LNG ship with a MARK III fuel tank according to claim 1, characterized in that: After the joining is completed, conduct a tightness test on the main screen wall of the MARK III type fuel tank. After the test is qualified, hoist the pump tower to the MARK III type fuel tank for installation.

3. A method for constructing an LNG ship with a MARK III fuel tank according to claim 1, characterized in that: In step S2, the coating gap of the epoxy resin should meet the technical requirements of the manufacturer.

4. A method for constructing an LNG ship with a MARK III fuel tank according to claim 1, characterized in that: In step S3, the insulating model is fixed to the hull structure by bolts.

5. A method for constructing an LNG ship with a MARK III fuel tank according to claim 1, characterized in that: In step S4, it is necessary to control the temperature inside the tank between 20 and 30 degrees Celsius, the humidity within 70%, and the inside of the tank should be kept dust-free.

6. A method for constructing an LNG ship with a MARK III fuel tank according to claim 1, characterized in that: When the bow section, the midship section and the stern section are floating, it is necessary to ensure that the midship section is in a level floating state.

7. A method for constructing an LNG ship with a MARK III type fuel tank according to claim 1, characterized in that: After the entire ship is joined together, check whether the MARK III type secondary screen that has been constructed is complete. If there are damages, repairs or corrections should be carried out.

8. A method for constructing an LNG ship with a MARK III fuel tank according to claim 1, characterized in that: Draw grid lines on the outer surface of the stainless steel film, and the grid lines correspond one by one to the corrugations of the stainless steel film.

9. A method for constructing an LNG ship with a MARK III fuel tank according to claim 8, characterized in that: When scribing the dihedral angle of the grid lines, the axis error is not more than ±2 mm, and when scribing on a plane, the axis error is not more than ±1 mm.