CN113895588B

CN113895588B - Ship lengthening reconstruction method

Info

Publication number: CN113895588B
Application number: CN202111366453.2A
Authority: CN
Inventors: 张春; 曹晔; 王友亮; 孙晓锋; 赵伟; 范军; 袁晨晨; 王之飞; 严波; 任海涛; 谷新华; 林怡; 沈伟; 桑桥; 王坤; 柏甲鹏; 吴健; 陈文华; 孟闯; 陆峻飞
Original assignee: Nanjing Changjiang Waterway Engineering Bureau
Current assignee: Nanjing Changjiang Waterway Engineering Bureau
Priority date: 2021-11-18
Filing date: 2021-11-18
Publication date: 2023-06-30
Anticipated expiration: 2041-11-18
Also published as: CN113895588A

Abstract

The invention discloses a ship lengthening and rebuilding method, which belongs to the technical field of ship lengthening and rebuilding, and comprises the following steps: and (3) carrying out survey marking, cutting, pulling and moving the bow section, carrying out sectional mounting, folding the bow section and refitting matched equipment on the ship. The invention utilizes the method of matching the air bag and the traction device to realize the displacement of the bow section, overcomes the difficulty of insufficient infrastructure of a shipyard, simultaneously greatly reduces the cost, has low foundation requirements on the shipyard, is applicable to both a dock and a slipway, and has wide applicability, low cost and controllable period; the five-section line inspection method is used for measuring and recording deflection values of ship positions through the cooperation of five line sections and lasers, and the small section carrying method is adopted for carrying and folding sections in a sectional manner, so that fine adjustment can be carried out on the carried and folded sections in time, and the lengthening reconstruction precision is improved; and after the segmentation scribing, supporting and reinforcing the large opening part and the weak part of the structural strength of the bow segment, wherein the cut plane is perpendicular to the center line of the ship, so that the controllable precision of the ship is further ensured.

Description

Ship lengthening reconstruction method

Technical Field

The invention belongs to the technical field of ship lengthening reconstruction, and particularly relates to a ship lengthening reconstruction method.

Background

As is well known, the world trade has the largest shipping and transportation ratio, however, the newly manufactured ship has high cost, long period and high investment, and the lengthening and reconstruction of the ship can meet the requirements of increasing the transportation capacity and improving the utilization rate of the ship in a short time. However, although the advantages of the lengthening and reconstruction of the ship are obvious, the technical difficulty is high, and the transformation and upgrading of the technology are imperative.

At present, a lengthening and reconstruction process is commonly used as a floating and sinking method and a track pulling and moving method, and the floating and sinking method is only suitable for a floating dock which is limited by a shipyard infrastructure, the fixing and reinforcement needed to be carried out are more, and the cut stem and stern sections also need to be correspondingly protected in order to avoid soaking in water; the track pulling and moving method needs special tracks or flat cars, has higher foundation requirements on shipyards, relatively high input cost and is not suitable for shipyards with smaller scale due to the fact that the two methods are high in use cost and need to be rebuilt on shipyards and shipways comprehensively.

Disclosure of Invention

Technical problems: the invention aims at solving the problems in the prior art, and aims to provide a ship lengthening reconstruction method, which reduces the structural change of a dock or a slipway and reduces the ship reconstruction cost.

The technical scheme is as follows: in order to solve the technical problems, the invention adopts the following technical scheme:

a ship lengthening reconstruction method comprises the following steps:

s1, ship survey marking: five section lines are drawn after the ship is docked or the slipway falls, including drawing two first straight lines parallel to the longitudinal direction of the ship on a main deck, drawing a second straight line parallel to the longitudinal direction of the ship on the left and right straight bottoms, drawing a ocean punching point, projecting the center line of the ship to the ground, and drawing a center marking line of the ship on the ground; setting a permanent support on the five section lines, setting a laser on the support, and measuring and recording deflection values of the ship positions corresponding to the five section lines, namely the two first straight lines, the two second straight lines and the ship center marking line, by using the laser; drawing a cutting loop line of a ship cross section on the outer surface of the ship, wherein the cutting loop line is perpendicular to the longitudinal direction of the ship and divides the ship into a bow section and a stern section;

s2, cutting: cutting the cutting loop line to divide the bow section and the stern section.

S3, pulling and moving the bow segment: arranging a plurality of air bags at the bottom of the bow section, inflating and lifting the bow section by utilizing the air bags, arranging a traction device in the direction of the bow, and dragging the bow section to a specified position by utilizing the traction device to match with the air bags in the direction of the bow;

s4, carrying in sections: taking a stern section as a reference section, hoisting and segmenting, and installing a temporary positioning code plate at a strong structure position after preliminary positioning is finished according to the five line sections, the recorded deflection value and the position of the preliminary positioning segmentation of the laser, detecting the precision before welding, and welding after detection;

s5, closing the bow section: the method comprises the steps of moving a bow section towards a stern by utilizing a traction device in combination with an air bag, arranging a second lifting hammer corresponding to a ship center marking line in front of and behind the center line of the bow section, wherein the second lifting hammer is used for detecting the leaning deviation degree of the bow section, controlling the folding precision of the bow section by utilizing a first straight line, a second straight line and the ship center marking line in combination with a laser and deflection values recorded in the earlier stage, adjusting the front-back height of the bow section by utilizing the pressure of inflation of the air bag to enable the bow section to reach a preset position and the height, keeping the air bag in an inflated state at the moment, arranging a dock pier with adjustable height at the bottom of the bow section, detecting the positioning precision of the bow section by utilizing five sections of lines in combination with the laser again after the dock pier is arranged, installing a positioning code plate on a ship, checking that the air bags are all stressed one by one, and withdrawing the air bag from each other, and welding a closing port;

s6, refitting matched equipment: and the ship piping and the cable are correspondingly prolonged, and the equipment is installed.

Preferably, in the step S1, the left and right side top strakes at the cross section of the ship respectively take two ocean punching points, the left and right flat bottom installation bilge keels at the cross section of the ship take two ocean punching points, the elastic wire is pulled, the position of the cutting loop is preliminarily determined, and then the position of the cutting loop is corrected again according to whether the cutting loop is perpendicular to the five sections of wires.

Preferably, in the step S1, the laser measures and records a plurality of deflection values in the vertical direction of each rib position of each first linear ship position, takes an average value of the plurality of deflection values as a first deflection line, measures and records a plurality of deflection values in the horizontal direction of each rib position of each second linear ship position, takes an average value of the plurality of deflection values as a second deflection line, measures and records a plurality of deflection values in the vertical direction of the ship bottom position corresponding to the ship center mark line, and takes an average value of the plurality of deflection values as a third deflection line.

Preferably, in step S2, a plurality of first support rods are disposed in the corresponding cabin at the cutting loop, to fix the ship hatch to prevent the hatch from deforming, and a second support rod is disposed at the cutting loop of the bow section to prevent the bow section from deforming at the cutting position, and the stern section is provided with a positioning bracket for fixing the stern section.

Preferably, in the step S3, the pulling device includes a pulley block and a winch connected with the pulley block through a wire rope, a first pulling lug is welded on the bow section, and the winch is connected with the first pulling lug through the pulley block and pulls the bow section to move towards the bow through the first pulling lug.

Preferably, the step S4 specifically includes the following steps:

s4.1, dividing the segment into three small segments, wherein the small segments comprise a first side segment, a bottom segment and a second side segment;

s4.2, taking the stern section as a reference section, hoisting the bottom section, hanging first hanging hammers in front and back of the bottom section, and matching the position of the bottom section with a laser according to the ship center marking line and the recorded deflection value

S4.3, hoisting the first side section, and positioning the first side section by matching with a laser according to the first straight line, the second straight line and the recorded deflection value;

s4.4, hoisting the second side section, and positioning the second side section by matching with the laser according to the first straight line, the second straight line and the recorded deflection value;

s4.5, after the initial positioning of the three small segment positions is finished, installing a temporary positioning code plate at the main position, detecting the precision before welding, and welding after detection.

Preferably, the step S5 further includes arranging a plurality of calabash groups between the segments and the bow segment, where the calabash groups are used to adjust the left and right positions of the bow segment in cooperation with the pulling device.

Preferably, in the step S5, when there is no gradient at the bottom of the dock or the slipway, a plurality of second pull lugs connected with the pulley block are disposed on the stern section, a plurality of third pull lugs connected with the pulley block through a wire rope are disposed on the bow section, and the winch pulls the bow section to the stern direction through the pulley block.

The beneficial effects are that: compared with the prior art, the invention has the following advantages: 1. the displacement of the bow section is realized by utilizing a method of matching the air bag and the traction device, excessive investment of professional equipment is not needed, the difficulty of insufficient infrastructure of a shipyard is overcome, the cost is greatly reduced, the air bag and the winch used by the invention can be realized in a leasing mode, the additional investment is low, the foundation requirement on the shipyard is low, and the invention has wide applicability, low cost and controllable period and is applicable to shipyards and shipyards;

2. the ship has certain deformation due to long-time use, the five-section line inspection method is used for measuring and recording deflection values of the ship position through the cooperation of five line sections and lasers, and the small section carrying method is adopted for carrying and folding sections in a sectional manner, so that fine adjustment can be carried out in time, and the lengthening reconstruction precision is improved;

3. and after the segmentation scribing, supporting and reinforcing the large opening part and the weak part of the structural strength of the bow segment, wherein the cut plane is perpendicular to the center line of the ship, so that the controllable precision of the ship is further ensured.

Drawings

FIG. 1 is a schematic drawing of the pulling method of the present invention;

FIG. 2 is a schematic diagram of the wire positions and cutting loop wire positions of the "five-segment wire inspection method" of the present invention;

FIG. 3 is a schematic illustration of the segmented construction of the present invention;

FIG. 4 is a side view of a cut bow section;

FIG. 5 is a schematic diagram of auxiliary adjustment of the hoist when the bow sections are closed;

FIG. 6 is a schematic diagram of retrofitting of a suction hopper dredger kit according to an embodiment.

Detailed Description

The invention will be further illustrated with reference to specific examples, which are carried out on the basis of the technical solutions of the invention, it being understood that these examples are only intended to illustrate the invention and are not intended to limit the scope thereof.

The invention is illustrated by the reconstruction project that the actual mud cabin of a 500-square trailing suction hopper dredger is lengthened by 6 meters, and the basic parameters of the ship are as follows:

'navigation dredging 22' of trailing suction hopper dredger "	Before reconstruction	After reconstruction
			Total length of	72.8m	80.3 m
Wide width of	14.0m	14.0 m
			Depth of shape	5.2m	5.2 m
Structural draft	4.0m	4.0m
			Maximum bilge	900m ³	1258m ³
Maximum depth of digging	13.5m	18.0 m

When the "aviation dredging 22" is lengthened and rebuilt, the "aviation dredging 22" original ship has three mud doors according to the overall arrangement condition of the mud tanks, namely the mud tanks can be divided into three standard sections. According to the use requirement and the actual ship condition, a scheme of adding a 6-meter long mud cabin standard section and a new set of mud door system meets the expected requirement, so that the docking with the front-rear structure can be facilitated, and the expected effect of lengthening and reconstruction can be met. Other ships are lengthened and rebuilt, the straightening section is preferentially considered, and the rebuilding difficulty can be greatly reduced no matter the ship is built in sections or is carried and positioned.

The whole process mainly comprises the steps of ship survey marking, sectional cutting, stem section pulling and moving, sectional carrying, stem section folding and matched equipment refitting. The survey and scribing of the ship mainly comprises the steps of rechecking the existing size of the ship in the earlier stage, and scribing cutting lines and detection lines at the designated positions; the sectional cutting mainly comprises the steps of locally reinforcing the vicinity of a cutting circumferential seam to prevent the ship from deforming; the stem section pulling and moving comprises positioning and fixing a stern section, cutting the stem section and pulling and moving; the segment carrying mainly comprises carrying positioning work of a new segment; the bow segment folding mainly comprises relevant works such as folding, positioning and the like; the refitting of the matched equipment mainly comprises the matched refitting work of equipment such as newly-added mud door system installation, mud pipes, cables, winches and the like. FIG. 1 is an overall schematic of the "balloon-pull method".

The main steps of the invention are specifically described as follows:

step one, scribing a ship survey using a five-segment line inspection method "

After the ship is docked or the berth falls, 4 straight lines parallel to the longitudinal direction of the ship are drawn on the left and right main decks and the left and right straight bottoms of the ship to be about 12 meters long (which can be adjusted according to actual needs and depends on the length of the newly added section), namely, two first straight lines 10 and two first straight lines 10 in fig. 2 are respectively marked with a plurality of ocean impact points on the 4 straight lines to make permanent marks, the center line of the ship is projected to the ground and is prolonged by 30 meters (which can be adjusted according to actual needs and depends on the length of the newly added section and the distance of the displacement of the bow section), and a ship center mark line 12 is drawn on the ground. The method comprises the steps of respectively making a permanent support at the positions of the five line segments (two first straight lines 10, two first straight lines 10 and a ship center marking line 12) close to a stern section 7, erecting a laser 13, measuring first deflection lines 14 (taking the average value of n deflection values from a theoretical horizontal plane in the upper and lower directions at a distance of 600 mm) of each rib position (rib distance of 600 mm) of the ship position of the first straight lines 10, continuously measuring and recording a plurality of deflection values in the horizontal direction of the ship position of the first straight lines 11 according to the method, making a record, taking the average value as a corresponding second deflection line, continuously measuring and recording n deflection values in the upper and lower directions of the ship bottom position corresponding to the ship center marking line 12 (taking a theoretical horizontal plane to find n values from the ship bottom), taking the average value as a corresponding third deflection line (taking the deflection line can reflect the deformation condition of the ship bottom center, and taking the difference value of the theoretical horizontal plane to be referred to by the ship bottom center back of a subsequent new subsection and the bow section), and controlling the mapping and closure accuracy of the five sections to control the map-mounted deflection lines 8. Cutting loop 16 is cut at FR67+200mm (FR 67 is a strong frame of the mud cabin section of the ship), two-point ocean punching points are respectively taken by the FR67+200mm left and right side roof plates, two-point ocean punching points are taken by the left and right flat bottom mounting bilge keels, the positions of the cutting loop 16 are preliminarily determined by pulling the elastic lines, the cutting loop 16 is vertical to the longitudinal direction of the ship, and then the adjustment quantity is reserved for the subsequent new section according to whether the cutting loop 16 is vertical to the five sections (normally, the cutting loop is vertical, the slight deviation has little influence), of course, the adjustment quantity can be also reserved through the comparison of the hanging vertical line, the hanging vertical line is absolutely vertical to the ground, the five sections of lines are basically vertical to the vertical line, the cut line is parallel to the vertical line, and the data are confirmed to be submitted to QC, ship inspection and east inspection.

Step two, sectioning and cutting

As shown in fig. 4, 4 first support rods 22 are erected in the mud cabin near the cutting loop line 16, round steel is adopted for the first support rods 22, a large opening of the mud cabin is fixed to prevent deformation, second support rods 21 are erected near the cutting loop line 16 of the bow section 9, the second support rods 21 are arranged vertically up and down by adopting angle steel, deformation of the cutting position of the bow section 9 is prevented, no angle steel is needed for a strong frame at the FR67 position of the stern section 7, and two sets of rigid positioning supports 6 are erected at the stern as shown in fig. 1 and used for fixing the position of the stern section 7 to enable the stern section 7 to be positioned on the rear dock pier 5.

The cutting requirement is that before cutting, the front cable and the rear cable are removed or cut off, the related pipelines are removed or cut off, and related personnel can execute cutting after confirming that the cutting loop line 16 is marked without errors. It should be noted that the main deck, hatch coaming, straight bottom, flat bottom and other intermediate decks should be cut by a semi-automatic cutting machine, and other related sections, structures and pipelines can be cut manually, so that the cut is as smooth as possible.

After the cutting, the steel wire is pulled for inspection, so that all the components are ensured to be cut.

Step three, pulling and moving the bow segment

A plurality of air bags 1 are arranged at the bottom of a bow section 9, the bow section 9 is inflated and lifted by the air bags 1, a pulling device is arranged in the direction of the bow, and the pulling device is matched with the air bags 1 to pull the bow section 9 to a specified position in the direction of the bow; the traction device comprises a pulley block 2 and a winch 3 connected with the pulley block 2 through a steel wire rope, and a bow section 9 which needs to be pulled and moved is usually heavier, so that the pulling force of the winch 3 and the bearable pressure of a single air bag 1 are required to be calculated, the positions of the air bags 1 are reasonably arranged and the number of the air bags 1 is increased according to the requirement, the number of the winches 3 or a certain number of movable pulley blocks 2 is increased, and the steel wire rope with a proper size is selected to meet the use requirement of traction. The selection of the air bag 1 can refer to the relevant requirements of CB/T3795-1996 (air bags for ship upper drainage and lower water), and the selection of the traction device can be adapted according to the weight of the bow section of the ship.

As shown in fig. 1, a pulling lug 4 is welded at the bow of a ship, a winch 3 is arranged and fixed, a pulley block 2, the winch 3 and the bow pulling lug 4 are connected by using a steel wire rope, and the pulling steel wire is tightened to be hard by using the winch 3, so that the relative position of a bow section 9 is ensured. The garbage on the ground is cleaned, and the air bag 1 is prevented from being punctured. Before the dock blocks below the bow section 9 are not evacuated, a sufficient number of air bags 1 are prepared, are alternately arranged below the bow section 9, then the air bags 1 are inflated step by step, the inflation pressure of each air bag is slowly and synchronously increased until the bow section 9 is stably lifted, after waiting for 5 minutes, the air bags 1 are confirmed to be airtight and have no abnormality, and the dock blocks below the bow section 9 can be evacuated in batches. At the same time, the uninflated air bags 1 are required to be continuously arranged in front of the bow section 9, the air bags 1 are arranged in front of the bow section 9 to be inflated along with the pulling and moving of the bow section 9 by a pulling device, and when the air bags 1 at the bottom of the ship behind the bow section 9 roll off, the air bags are deflated and moved to the bow part, and the cycle is performed until the bow section 9 reaches a specified position. After the bow section 9 reaches the designated position, the fact that the air bags 1 are not abnormal is confirmed again, dock blocks can be arranged between gaps of the air bags 1 in batches, and after the dock blocks are arranged, the air bags 1 can be deflated and removed.

Step four, carrying in sections

Since the age of the ship "navigation dredging 22" has been 15 years, the ship is considered to have a certain deformation, and the small-section embedding method is adopted for carrying, so that the section 8 can be prefabricated in advance, and the deviation can be adjusted in time. As shown in fig. 3, taking the main body portion 20 of the segment 8 with the addition of "dredging 22" as an example, the main body portion 20 is divided into 3 small segments, a first side segment 17, a bottom segment 18, a second side segment 19, respectively. It should be noted that 10mm is reserved at the two ends of the stem and stern as the subsequent chamfering and the chamfering and adjustment of the end faces of the cutting circular seam when the segment 8 is prefabricated (because the cutting generally adopts high-temperature flame to manually cut the hull, errors can be generated), after the cut end faces are processed to be flat, dock blocks are arranged, the stern segment 7 is taken as a reference positioning segment, the bottom segment 18 is firstly carried (i.e. hoisted) by hoisting, and then the first side segment 17 and the second side segment 19 are carried in sequence. The laser 13 is used on a permanent laser bracket at the end part of the five lines of the stern section 7, the first hanging weights 15 are respectively hung on the bow and the stern of the bottom section 18, the left and right positions of the bottom section 18 are controlled by the first hanging weights 15 corresponding to the ship center marking line 12, the bottom section 18 is placed on a arranged dock block, the crane can slightly move the bottom section 18, the positions of the bottom section 18 are matched with the laser 13 according to the ship center marking line 12 and the recorded deflection value on the ground, and the positions of the first side section 17 and the second side section 19 are matched with the laser 13 by using the two first straight lines 10, the two second straight lines 12 and the original recorded deflection value. After all small segment positions are initially positioned, a temporary positioning code plate is installed at a strong structure position, the detection precision before welding is detected corresponding to the related detection requirement of China shipbuilding quality standard 2016, and after the detection precision meets the related specification and requirement, QC, ship detection and signature confirmation are contacted. And finishing the welding task according to the standard requirement, and performing a test after welding.

Step five, closing the bow segment

The lengthening reconstruction of the 'navigation dredging 22' is carried out on a slipway with a slope ratio of 1:50, when a bow section is required to be folded, the bow section 9 is moved towards the stern by utilizing a slow loosening traction device matched with an air bag 1 under the driving of dead weight sliding of the bow section 9, a ship center mark line 12 of a second lifting hammer corresponding to the ground is arranged in front of and behind the center line of the bow section 9, and when the bow section 9 is leaned back, the second lifting hammer can detect the leaning deviation degree of the bow section 9 so as to adjust in time, and the folding precision of the bow section 9 is controlled by utilizing a first straight line 10, a second straight line 11, the ship center mark line 12 matched with a laser 13 and deflection values recorded in the earlier stage. According to FIG. 5, two groups of calabash groups 23 are arranged on a section 8 and a bow section 9, the left and right positions of the bow section 9 can be adjusted by using the calabash groups 23 in combination with a traction device, the front and rear heights of the bow section 9 are adjusted by using the inflation pressure of the air bag 1 until the positions of the bow section 9 meet the related standard requirements, the air bag 1 is kept inflated at the moment, docking blocks with adjustable heights are arranged at the bottom of the bow section 9, after the docking blocks are arranged, the positioning precision of the bow section 9 is checked again by using a five-section line inspection method, after the fact that the docking blocks meet the related inspection standard and standard is confirmed, a positioning code plate is installed at a stronger position of a ship structure in time, the docking blocks are checked again to be stressed, and the air bag 1 is evacuated one by one.

The welding quality of the closure opening is an important flow of precision control, the precision before and after welding needs to be controlled, the distance between grooves needs to be focused when the grooves are cut before welding, the working such as cleaning and polishing near the grooves is performed, and the position of the closure opening is deformed locally or cannot be adjusted and adjusted before welding. After conventional defects such as surface weld flash, slag inclusion and air holes are treated after welding, the proportion of ultrasonic flaw detection is properly increased, and 100% vacuumizing tightness test is performed to ensure the welding quality of the folding port.

Step six, refitting matched equipment

For the 'navigation dredging 22' ship pipe system and the cable to be correspondingly prolonged, the corresponding dredging pipe system and the hydraulic pipe system should be prolonged along with the corresponding dredging pipe system, and the cable penetrating from the head to the tail should be increased in the length of the cable prolonged by the junction box. As shown in fig. 6, after the rake 27 is lengthened, the strength of the hanger 28, the thickness of the wire rope, whether the tension of the winch 24 is satisfied, and the loading mud pipe 25 is correspondingly lengthened. The control logic of the dredging control system after adding a set of mud gate system 26 is matched and modified, and in addition, whether the performance of the mud pump meets the deep-digging requirement after the rake pipe is lengthened is considered. And calculating according to the corresponding design company to ensure that related equipment meets the requirements and ensure the ship construction safety and dredging performance.

Example 2

In the fifth step of folding, when there is no gradient at the position where the ship falls, a second pull lug is welded on each side edge of the stern section 7, each second pull lug is connected with one pulley block 2, two third pull lugs corresponding to the second pull lugs are welded on the bow section 9, a steel wire rope of the winch 3 is connected with the two third pull lugs through the pulley block 2, so that the direction of the force is changed through the second pull lugs and the pulley block 2, and when the winch 3 works, the pulling force acts on the third pull lugs through the steel wire rope to pull the bow section 9 towards the stern, so that the winch 3 moves towards the stern in cooperation with the air bag 1.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims

1. The ship lengthening reconstruction method is characterized by comprising the following steps of:

s1, ship survey marking: five sections of lines are drawn after the ship enters the dock or the slipway falls on the pier, including drawing two first straight lines (10) parallel to the longitudinal direction of the ship on a main deck, drawing a second straight line (11) parallel to the longitudinal direction of the ship on the left and right straight bottoms, drawing the ocean punching point, projecting the center line of the ship to the ground, and drawing a center marking line (12) of the ship on the ground; setting a permanent support on five section lines, setting a laser (13) on the support, and measuring and recording deflection values of the five section lines corresponding to the ship positions by using the laser (13), wherein the deflection values are the first straight lines (10), the second straight lines (11) and the ship center mark line (12); drawing a cutting loop line (16) of a ship cross section on the outer surface of the ship, wherein the cutting loop line (16) is perpendicular to the longitudinal direction of the ship and divides the ship into a bow section (9) and a stern section (7);

s2, cutting: cutting the cutting loop line (16) to divide the bow section (9) and the stern section (7);

s3, pulling and moving the bow segment: a plurality of air bags (1) are arranged at the bottom of a bow section (9), the bow section (9) is inflated and lifted by utilizing the air bags (1), a pulling device is arranged in the direction of the bow, and the bow section (9) is pulled to a specified position in the direction of the bow by utilizing the pulling device in combination with the air bags (1);

s4, carrying in sections: taking a stern section (7) as a reference section, hoisting a subsection (8), and installing a temporary positioning code plate at a strong structure position after preliminary positioning is finished according to the five section lines, the recorded deflection value and the position of the preliminary positioning subsection (8) of a laser (13), detecting the precision before welding, and welding after detection;

s5, closing the bow section: the method comprises the steps of moving a bow section (9) towards a stern by utilizing a traction device in cooperation with an air bag (1), arranging a second lifting hammer corresponding to a ship center marking line (12) in front of and behind the center line of the bow section (9), detecting the leaning deviation degree of the bow section (9), utilizing a first straight line (10), a second straight line (11) and the ship center marking line (12) in cooperation with a laser (13) and a deflection value recorded in the front to control the folding precision of the bow section (9), adjusting the front and rear height of the bow section (9) by utilizing the inflation pressure of the air bag (1) to enable the bow section (9) to reach a preset position and height, keeping the air bag (1) in an inflated state at the moment, arranging docking piers with adjustable heights at the bottom of the bow section (9), detecting the positioning precision of the bow section (9) by utilizing five sections of lines in cooperation with a laser (13) again after the docking piers are arranged, installing positioning code plates on a ship, checking that the docking piers are stressed one by one, deflating the air bag (1) and withdrawing an air bag from a welding joint;

2. The method for lengthening and rebuilding a ship according to claim 1, wherein in the step S1, two points are respectively provided on the left and right side top plates at the cross section of the ship, two points are provided on the left and right bottom mounting bilge keels at the cross section of the ship, the elastic wire is pulled, the position of the cutting ring wire (16) is primarily determined, and the position of the cutting ring wire (16) is again corrected according to whether the cutting ring wire is perpendicular to the five sections of wires.

3. The method for lengthening and rebuilding the ship according to claim 1, wherein in the step S1, a laser (13) measures and records a plurality of deflection values in the up-down direction of each rib position of the ship position of each first straight line (10), takes an average value of the plurality of deflection values as a first deflection line (14), measures and records a plurality of deflection values in the horizontal direction of each rib position of the ship position of each second straight line (11), takes an average value of the plurality of deflection values as a second deflection line, measures and records a plurality of deflection values in the up-down direction of the corresponding ship bottom position of a ship center marking line (12), and takes an average value of the plurality of deflection values as a third deflection line.

4. The method for lengthening and rebuilding a ship according to claim 1, wherein in the step S2, a plurality of first support rods (22) are arranged in the corresponding cabin at the cutting loop (16), the hatch of the ship is fixed to prevent the deformation of the hatch, a second support rod (21) is arranged at the cutting loop (16) of the bow section to prevent the deformation of the cutting position of the bow section, and the stern section is provided with a positioning bracket (6) for fixing the position of the stern section.

5. The ship lengthening and rebuilding method according to claim 1, wherein in the step S3, the pulling device comprises a pulley block (2) and a winch (3) connected with the pulley block (2) through a steel wire rope, a first pulling lug (4) is welded on the bow section, and the winch (3) is connected with the first pulling lug (4) through the pulley block (2) and pulls the bow section (9) to move towards the bow through the first pulling lug (4).

6. The ship lengthening reconstruction method according to claim 1, wherein the step S4 specifically includes the steps of:

s4.1, dividing the section (8) into three small sections, wherein the small sections comprise a first side section (17), a bottom section (18) and a second side section (19);

s4.2, taking the stern section (7) as a reference section, hoisting a bottom section (18), hanging a first lifting hammer (15) in front and behind the bottom section (18), and positioning the position of the bottom section (18) according to the ship center marking line (12) and the recorded deflection value and matching with a laser (13)

S4.3, hoisting the first side section (17) and positioning the first side section (17) according to the first straight line (10), the second straight line (11) and the recorded deflection value in cooperation with the laser (13);

s4.4, hoisting the second side section (19) and positioning the second side section (19) according to the first straight line (10), the second straight line (11) and the recorded deflection value matched with the laser (13);

7. The ship lengthening and rebuilding method according to claim 1, wherein the step S5 further comprises arranging a plurality of hoist groups (23) on the segments (8) and the bow segments (9), wherein the hoist groups (23) are used for adjusting the left and right positions of the bow segments (9) in cooperation with a pulling device.

8. The method for lengthening and rebuilding a ship according to claim 5, wherein in the step S5, when the bottom of the dock or the slipway has no gradient, a plurality of second pull lugs connected with the pulley block (2) are arranged on the stern section (7), a plurality of third pull lugs connected with the pulley block (2) through a steel wire rope are arranged on the bow section (9), and the winch (3) pulls the bow section (9) towards the stern through the pulley block (2).