Construction method for LNG ship No.4 cargo hold cargo containment

Abstract

A construction method for the cargo cofferdam of LNG carrier No. 4 cargo hold involves modifying the sectional division diagram, re-dividing the 901C main assembly section and the No. 5 isolation compartment. The aft wall of the No. 5 isolation compartment extends rearward into the 901C main assembly section, forming a stern-protruding stern compartment that connects to the No. 5 isolation compartment. This improves the structural strength of the No. 5 isolation compartment, reduces the impact of 901C closure on the deformation of the No. 4 cargo hold's inner hull plates, and eliminates the need for secondary marking after closure welding. Construction begins on the bow 40 meters, installing insulating plates from the bow corners towards the stern. 24 hours after the 901C closure welding, insulation plate installation begins on the stern 10 meters, advancing the plates from the two stern corners towards the center of the cargo hold. This invention strengthens the hull structure, reduces inner hull plate deformation, and minimizes the workload of secondary marking after the 901C closure welding and subsequent re-measurement of the cargo hold's inner hull plates. To avoid the complete halt in the production of the No.4 cargo hold enclosure due to the delay after the 901C closure welding, ensure the continuity of cargo enclosure production, and shorten the cargo enclosure construction cycle.

Description

Technical Field

[0001] This invention belongs to the field of marine ship construction and design, and specifically relates to a construction method for the cargo hold cofferdam of LNG ship No. 4. Background Technology

[0002] In the LNG carrier construction field, the cargo containment system is a special construction area, and its construction progress is a key factor affecting the overall ship production milestones. The construction of the ship's conventional areas also impacts cargo containment production. Taking a 175,000 cubic meter MARK III type LNG carrier as an example, it is divided into 4 cargo holds and 5 isolation compartments from bow to stern. Isolation compartments separate cargo holds from each other; Isolation compartment No. 1 separates cargo hold No. 1 from the bow; Isolation compartment No. 5 separates cargo hold No. 4 from the engine room, and so on. Figure 1 As shown. Each cargo hold forward bulkhead is equipped with one isolation compartment. Cargo hold No. 5 is located at the stern of cargo hold No. 4. Due to the impact of the welding of the 901C main assembly section after the closure, the closure stress and welding deformation have a significant impact on the deformation of the inner shell plate of cargo hold No. 4. It is necessary to wait 24 hours after the 901C closure welding to ensure the flatness and deformation of the inner shell plate are stable, and then re-measure the flatness of the inner shell plate and the cargo enclosure markings of cargo hold No. 4. The markings include baseline lines and grid lines. Only after the flatness of the inner shell plate and the markings are repaired and qualified can the subsequent cargo enclosure procedures be carried out in sequence, including stud driving, shim leveling, final cleaning of the compartment, insulation plate installation and integrity, manual / automatic bonding, installation of top bridge plate TBP and corner connecting beam EOB, corrugated plate assembly and welding, etc. At present, the insulation plate installation method of cargo hold No. 4 is to start from the entire compartment, advancing from the corner area to the center of the compartment, and advancing downwards on each side from the 8th floor to the 0th floor in terms of height. Insulation panels can only be installed after all previous processes have passed inspection and are free of any outstanding issues. The welded joint of the 901C assembly line affected the flatness of the inner shell of cargo hold No. 4, impacting the marking corrections and thus delaying the start of the insulation panel installation for the entire hold, causing a complete halt to subsequent processes in the cargo enclosure.

[0003] The current construction method for a certain LNG carrier is as follows: Sectional assembly is performed. The cargo hold sections are joined together in the dry dock to form a parallel hull consisting of four connected cargo holds, excluding the bow, engine room, and forecastle / sterncastle. The parallel hull is then undocking and moored at the pier for ballast tank strength tests. Cargo cofferdam construction is then carried out according to the working conditions, following the sequence of 3 holds – 2 holds – 4 holds – 1 hold. The parallel hull returns to the dry dock, where the bow, engine room, forecastle, and sterncastle are joined until the entire ship is formed. Cargo cofferdam construction continues simultaneously upon returning to the dry dock. System acceptance, sea trials, and final finishing touches are then performed before delivery. After the final assembly department delivers the cargo holds, the flatness of the inner shell plates is checked, cargo hold lines are marked, studs are installed, reference shims are leveled, and insulating plates are installed simultaneously from the four corners of the cargo hold towards the center. The construction method for the No. 4 cargo hold is significantly affected by the 901C assembly. The accuracy of marking and leveling needs to be adjusted and corrected at any time according to the deformation of the inner shell plates. The start-up time for the insulation boards of the No. 4 cargo hold is long. In particular, the start-up of the 8th layer of insulation boards affected the installation of the subsequent 7-0 layers of insulation boards, and even the subsequent series-connected cargo enclosure works and inspection, thus affecting the overall cargo enclosure production schedule. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a construction method for the cargo cofferdam of LNG carrier No. 4 cargo hold, the technical solution of which is as follows: A construction method for the cargo cofferdam of LNG carrier No. 4 cargo hold, the specific operation is as follows: S1: The design of the segmented partitioning diagram was modified, and the 901C main assembly section and the No.5 isolation compartment were re-divided. The rear wall of the top of the No.5 isolation compartment was extended rearward into the 901C main assembly section, forming a hollow compartment protruding towards the stern. This hollow compartment was connected to the No.5 isolation compartment. The hollow compartment can improve the strength of the No.5 isolation compartment and reduce the impact of the 901C closure welding on the inner shell plate deformation of the No.4 cargo hold. This eliminates the need for secondary marking after the closure welding. The deviation values ​​before and after the improvement were recorded and the data were compared to determine the boundary line position of the zoning construction method.

[0005] S2: Confirm the location of the boundary line of cargo hold area No.4. Draw a circular boundary line on cargo hold No.4, which is 50 meters long in the bow direction, at a distance of 40 meters from the bow, dividing cargo hold No.4 into two areas: a 40-meter bow area and a 10-meter stern area.

[0006] The 40-meter bow area and the 10-meter stern area were to be constructed, inspected, and reported separately, with each area reported from the 8th floor downwards.

[0007] S3: The original method was to measure the flatness of the inner shell plate 24 hours after the 901C was welded together, and only after it was repaired and qualified could the entire cargo hold be enclosed. The new method is to first install the insulation plates in the bow 40-meter area. There is no need to wait for the 901C main assembly section to be welded together. After the flatness of the inner shell plate in the 40-meter area of ​​the bow is inspected and repaired and passes the inspection, the marking, stud welding, reference pad leveling, cleaning, and insulation plate installation are carried out. The insulation plates in the 40-meter area of ​​the bow are installed from the two corner areas towards the stern.

[0008] S4: After the insulation board in the 40-meter area at the bow is installed, the 901C main assembly section is welded together. 24 hours after welding, the flatness of the inner shell plates on each side of the four compartments in the 10-meter area at the stern is re-measured. After the flatness of the inner shell plates in the 10-meter area at the stern is repaired and qualified, the following steps are carried out in sequence: marking and re-measurement and correction, stud welding, leveling of reference pads, cleaning, and installation of insulation boards. The insulation boards in the 10-meter area at the stern are installed from the stern towards the two corner areas and then towards the bow.

[0009] S5: After the insulation boards in the 40-meter bow area and the 10-meter stern area are installed, install the top bridge plate.

[0010] Before the corrugated sheet is installed, the main process of the cargo enclosure system is: marking - studs - reference pads - insulation board installation - insulation board integrity - bonding - TBP / EOB installation. Before starting the next process, the previous process is required to have completed 6-8 layers of inspection. For example, if the integrity inspection of 6-8 layers (including liquid dome) of the insulation board is completed and any remaining issues are resolved, the bonding of 8 layers can begin. Subsequent construction requires that after each layer of the previous process is inspected, the next process can be carried out on the previous layer.

[0011] Furthermore, in the above-mentioned construction method for the No. 4 cargo hold of an LNG ship, the installation sequence for the bow 40-meter area and the stern 10-meter area is as follows: construction begins from the 8th floor downwards.

[0012] Furthermore, the aforementioned construction method for the No. 4 cargo hold of an LNG carrier is further elaborated in that the 901C general assembly consists of the first and second floors of the living quarters on the main deck.

[0013] Furthermore, in the above-mentioned construction method for the No. 4 cargo hold of an LNG ship, after the final assembly department delivers the cargo hold, it is forbidden to use open flames on the inner wall of the cargo hold to avoid burning the paint on the inner wall of the cargo hold, increasing the need for grinding, oiling and cleaning, and damaging the leveling reference blocks and insulation plates.

[0014] The above-mentioned method for constructing the No. 4 cargo hold enclosure of an LNG carrier is further elaborated so that, from bow to stern, the compartments are arranged in the following order: No. 1 isolation compartment, No. 1 cargo hold, No. 2 isolation compartment, No. 2 cargo hold, No. 3 isolation compartment, No. 3 cargo hold, No. 4 isolation compartment, No. 4 cargo hold, and No. 5 isolation compartment.

[0015] The lower part of the NO.5 isolation compartment is adjacent to the engine room, and the upper part is adjacent to the 901C main assembly section.

[0016] Furthermore, in the aforementioned construction method for the No. 4 cargo hold of an LNG ship, the third floor and above of the living quarters are located above the 901C main assembly section and the empty cargo hold.

[0017] Furthermore, the above-mentioned construction method for the No. 4 cargo hold of an LNG ship requires an ambient temperature of 15-35 degrees Celsius for the installation of insulation boards and an ambient temperature of 20-30 degrees Celsius for the installation of bonding and top bridge plates, and air conditioning and heating machines are used to ensure the temperature inside the hold.

[0018] The beneficial effects of this invention are: 1. Modify the segment division. Strengthen the hull structure, reduce the deformation of the inner hull plates, and reduce the workload of secondary marking after the re-measurement of the marking inside the compartments following the 901C assembly welding.

[0019] 2. Strictly implement the 1040 construction method plan and production schedule to avoid stagnation in the enclosure construction after the welding is completed, and ensure continuous production.

[0020] 3. Optimize the board loading sequence to improve board loading efficiency.

[0021] 4. Strengthen production control of hot work operations to avoid the paint on the inner shell of the cargo hold being burned due to hot work in the isolation compartment, which would increase the need for grinding, oiling and cleaning, and damage the reference pads or even the insulation boards.

[0022] 5. Ensure the early commencement and continuous operation of insulation board installation, bonding, and top bridge plate installation, shortening the cycle of each process. Insulation board installation will start 14 days earlier; the cycle for insulation board installation and integrity inspection will be shortened by 14 days; bonding will start 2 days earlier, shortening the cycle by 17 days; and top bridge plate installation will start 17 days earlier, shortening the cycle by 12 days.

[0023] 6. Improved board assembly efficiency; the interval between the integrity inspection of two adjacent insulation boards is shortened to 3 days.

[0024] 7. No.4 The automatic bonding of the 8-4 layers at the bow 40 meters is not affected by the loading of the stern 10 meters. The automatic bonding of the 8-4 layers and the bonding of the A side started 2 days ahead of schedule.

[0025] 8. Solidify the management documents for the 1040 construction method, and develop shorter timelines for subsequent ships that conform to the construction model, continuously optimize construction methods, and accelerate production. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of an existing ship structure; Figure 2 This is a schematic diagram of the ship structure of the present invention; Among them, 1-901C main assembly section, 2-No.4 cargo hold, 3-empty hold, 4-engine hold, 5-living quarters, and 6-No.5 isolation compartment. Detailed Implementation

[0027] The invention will be further described with reference to the accompanying drawings.

[0028] A construction method for the No. 4 cargo hold of an LNG carrier, wherein the compartments arranged from bow to stern are, in sequence, No. 1 isolation compartment, No. 1 cargo hold, No. 2 isolation compartment, No. 2 cargo hold, No. 3 isolation compartment, No. 3 cargo hold, No. 4 isolation compartment, No. 4 cargo hold, and No. 5 isolation compartment. The lower aft wall of the No. 5 isolation compartment is adjacent to the engine room, and the upper aft wall is adjacent to the 901C main assembly section. Figure 2 As shown, the 901C main assembly section is located on the lowest floor of the dormitory building, and the 901C main assembly section consists of the first and second floors of the dormitory building.

[0029] The specific steps are as follows: S1: Modify the segmentation diagram. Re-divide the 901C main assembly section and the corresponding sections of the No.5 isolation compartment. Add a box structure to the upper opening of the rear wall of the No.5 isolation compartment, protruding towards the stern, while the front opening of the 901C main assembly section is correspondingly offset towards the stern. This improves the structural strength of the No.5 isolation compartment, reduces the impact of the 901C main assembly section closure on the deformation of the No.4 cargo hold inner shell plate, and reduces the workload of re-measurement and correction of the markings after closure welding. Record the deviation values ​​before and after the improvement and compare the data.

[0030] S2: Determine the boundary line location for the zoned construction method. Avoid installing insulation boards across zones, and mitigate the impact of the 901C assembly section welding on the plate installation and bonding processes in the bow 40-meter area. Based on the 50-meter length of the No.4 cargo hold in the bow-stern direction, the arrangement of insulation boards shown in the "No.4 Hold Reference Pad Position Installation Diagram" and "No.4 Hold Insulation Board Installation Diagram," combined with the stress analysis of the area affected by hull deformation, the 50-meter-long No.4 cargo hold in the bow-stern direction is divided into two zones: a 40-meter bow zone and a 10-meter stern zone.

[0031] S3: First install the insulation board in the 40-meter bow area, then install the insulation board in the 10-meter stern area. The 40-meter bow area installation will proceed after the 901C main assembly is completed and the marking, studs, leveling, and final cleaning of the 8 layers in the 40-meter bow area have passed inspection. 24 hours after the 4 901C main assembly is welded together, re-inspect the flatness of the shell plates in the 10-meter stern area and repair any issues. Re-inspect the markings and correct any errors. After the studs, leveling, final cleaning of the 8 layers, and any remaining issues have been resolved, the installation of the insulation board in the 10-meter stern area can begin.

[0032] S4: Optimization of Marking Method. No. 4 Cargo hold marking is carried out after handover, consistent with the original method. The bow 40 meters does not require re-marking after the 901C main assembly section is welded. However, for the stern 10 meters, marking is re-marked and corrected 24 hours after the 901C main assembly section is welded, once the inner shell plate deformation has stabilized. Then, studs are installed, leveling is performed, and the installation of insulation panels in the stern 10-meter area begins. Insulation panels are installed from the two stern corners towards the bow.

[0033] The insulation panels for the 40-meter bow area are installed from the bow towards the two corner areas and then towards the stern. When conditions permit for construction in the 10-meter stern area, the panels on side A are installed from the stern towards the corner areas and then towards the bow. The insulation panels for the 40-meter bow area are installed first, followed by the insulation panels for the 10-meter stern area. In the vertical direction, both areas are constructed from the 8th floor down to the 0th floor, and the construction sequence remains unchanged.

[0034] Conditions for starting the installation of the insulation board on side A in the 40-meter section at the bow: The installation can begin once the flatness, cleanliness, marking, studs, and leveling of the inner shell plate have passed inspection and all remaining issues have been resolved.

[0035] Conditions for starting the installation of the insulation board on side A in the 10-meter stern area: 24 hours after the 901C main assembly section is welded together, check and correct the flatness of the inner shell plate, re-measure and correct the marking, install studs, level, clean and inspect for compliance, and handle any remaining issues before installing the board.

[0036] S5: Zonal inspection, with the bow 40m and stern 10m sections divided into tiered inspection zones, remaining unchanged from the 8th layer down to the 0th layer. This reduces the amount of insulation board installation material needed for the 8th layer and the 10m stern section, thus accelerating the installation and inspection progress of the bow 40m insulation board.

[0037] S6: Optimization of Adhesion Method. Conditions for starting manual adhesion: 8-6 layers of insulation board installation and integrity inspection passed, remaining issues resolved. Conditions for starting automatic adhesion (8-4 layers): 3 layers of insulation board integrity inspection passed, remaining issues resolved.

[0038] Conditions for starting A-side bonding: The integrity of the 8-6 layer insulation board has been inspected and approved, and any remaining issues have been resolved.

[0039] The automatic bonding construction of layers 4-8 in the 40-meter bow area is not affected by the panel installation in the 10-meter stern area, and the bonding of side A can start ahead of schedule.

[0040] S7: Hot Work Control. Hot work operations will be moved forward by the final assembly department. After cargo hold handover, avoid hot work on the underside of the cargo hold inner hull plating to prevent the paint on the inner hull plating from burning, increasing the need for sanding, oiling, and cleaning, and potentially damaging the reference pads or even the installed insulation panels.

[0041] S8: Shorten the production cycle of cargo hold enclosure No.4. The new construction method allows the installation and integrity of insulation boards, bonding, and top bridge plate to start earlier, be completed earlier, and be inspected earlier. In particular, the automatic bonding of layers 8-4 and bonding of surface A can start 2 days earlier. The original installation and integrity of insulation boards, bonding, and top bridge plate installation took 93 days, which was shortened to 75 days.

[0042] Project Name Actual construction period (days) of the original method Actual construction period (days) for the new method Saved days Improvement rate Start work ahead of schedule (days) Insulation board installation and integrity 61 42 19 31% 14 Adhesion 50 28 22 44% 2 TBP Installation 33 29 4 12% 17 total 93 75 18 19% 33

[0043] This invention improves the efficiency of insulation board installation and shortens the insulation board integrity inspection cycle. The interval between the integrity inspections of adjacent upper and lower insulation board layers is reduced from 3.7 days to 3 days, improving the tightness of the inspection process. Each area is inspected separately for its entire layer. The integrity inspection interval for each layer of insulation boards in compartment N0.4 is shortened by 0.7 days, resulting in a total cycle saving of 7 days.

[0044] The construction period is reduced by 18 days, and the inspection period is reduced by 7 days.

[0045] .

[0046] This invention solves the following problems: 1. Strengthen the hull structure, reduce the deformation of the inner hull plates, and reduce the workload of marking correction after marking re-measurement.

[0047] 2. Optimize construction methods to avoid the impact of waiting for the 901C main assembly section to be welded on the start point of insulation board installation.

[0048] 3. The start dates for each process, including insulation board installation, bonding, and top bridge plate installation, are brought forward, effectively compressing the cycle time of each process and thus shortening the overall cycle time.

[0049] 4. The interval for reporting the integrity of insulation board installation has been shortened from the original 1-8 days, with an average of 3.7 days, to 1-6 days, with an average of 3 days, thereby improving the efficiency of insulation board installation and shortening the time interval between reporting of adjacent layers.

[0050] 5. Strengthen the management and control of hot work operations to prevent the final assembly department from using hot work on the back of the cargo hold inner shell after the cargo hold is handed over, which could cause the paint on the inner shell to burn, requiring grinding, oiling and cleaning work, damaging the reference pads and even the insulation boards, and reducing the amount of ineffective work caused by poor hot work control.

[0051] 6. Optimize the bonding process and production plan, accelerate the bonding start-up time, and shorten the bonding cycle.

Claims

1. A construction method for the cargo cofferdam of cargo hold No. 4 of an LNG carrier, characterized in that, The specific steps are as follows: S1: The design of the segment division diagram is modified to re-divide the 901C main assembly section and the No.5 isolation compartment. The aft wall of the No.5 isolation compartment on the main deck extends towards the stern into the 901C main assembly section, forming an empty compartment that protrudes towards the stern. The empty compartment is connected to the No.5 isolation compartment below it. S2: Confirm the location of the boundary line of cargo hold area No.

4. Draw a circular boundary line on cargo hold No.4, which is 50 meters long in the bow direction, at a position 40 meters away from the bow wall. The boundary line divides cargo hold No.4 into two areas: a 40-meter bow area and a 10-meter stern area. The 40-meter bow area and the 10-meter stern area were to be constructed, inspected, and reported separately, with construction and reporting carried out layer by layer from the 8th floor downwards; S3: Without waiting for the 901C general assembly progress, following the conventional cargo enclosure production process, the general assembly department delivers the cargo hold - inner shell plate flatness - marking - stud welding - wedge leveling - final cleaning of the 8th floor of the compartment and the liquid dome area. After the previous process is inspected and approved without any remaining issues, the insulation plates in the 40-meter area at the bow are installed. The installation sequence of the insulation plates in the 40-meter area at the bow is from the bow to the two corner areas and then to the stern. S4: The General Assembly Department will assemble the 901C general assembly section according to the production plan. 24 hours after the assembly welding, the flatness of the inner shell plates of each of the four compartments in the stern 10-meter area will be re-measured. After the flatness of the inner shell plates is repaired and qualified, the following steps will be carried out in sequence: line marking re-measurement and correction, stud welding, reference pad leveling, and final cleaning of the liquid dome area of ​​the eight compartments. After the above procedures are inspected and qualified and the remaining issues are resolved, the installation of the insulation plate in the stern 10-meter area can begin. The insulation plate in the stern 10-meter area will be installed from the stern to the two corner areas and then to the bow. S5: The main construction and inspection sequence of the main processes, including the installation of insulation boards in the 40-meter bow area and the 10-meter stern area, the integrity of the insulation boards, manual / automatic bonding, and the installation of TBP / EOB, is the same as the original construction method of the cargo enclosure. The difference is that the No.4 cargo warehouse implements separate construction and inspection for the 40-meter bow area and the 10-meter stern area.

2. The construction method for the cargo cofferdam of LNG carrier No. 4 cargo hold according to claim 1, characterized in that, The installation sequence in the height direction of the 40-meter bow area and the 10-meter stern area is as follows: construction starts from the 8th floor and proceeds downwards.

3. The construction method for the cargo cofferdam of LNG carrier No. 4 cargo hold according to claim 1, characterized in that, The 901C main assembly section consists of the forecastle on the main deck, which comprises the first and second floors of the living quarters.

4. The construction method for the cargo cofferdam of LNG carrier No. 4 cargo hold according to claim 1, characterized in that, After the final assembly department delivers the cargo hold, it is forbidden to use open flames on the hull structure on the reverse side of the cargo hold inner shell plating, so as to avoid burning the paint on the inner shell plating, increasing the need for grinding, oiling and cleaning, and damaging the leveling reference pads and the installed insulation plates.

5. The construction method for the cargo cofferdam of LNG carrier No. 4 cargo hold according to claim 1, characterized in that, From bow to stern, the compartments are arranged as follows: No. 1 isolation compartment, No. 1 cargo hold, No. 2 isolation compartment, No. 2 cargo hold, No. 3 isolation compartment, No. 3 cargo hold, No. 4 isolation compartment, No. 4 cargo hold, and No. 5 isolation compartment. The rear wall of the NO.5 isolation compartment is adjacent to the engine room below the main deck and to the 901C main assembly section above the main deck.

6. The construction method for the cargo cofferdam of LNG carrier No. 4 cargo hold according to claim 3, characterized in that, The third floor and above of the living quarters building are located above the 901C main assembly section and the stern bulge.

7. The construction method for the cargo cofferdam of LNG carrier No. 4 cargo hold according to claim 1, characterized in that, The installation of insulation boards requires an ambient temperature of 15-35 degrees Celsius inside the cabin. Manual / automatic bonding and TBP / EOB installation require an ambient temperature of 20-30 degrees Celsius inside the cabin. The cabin temperature is maintained by using cabin air conditioning, temporary heating machines, cotton curtains at the side openings, and liquid dome doors that are normally closed.

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