Classification of shipbuilding

The division of the workshop is often different according to the production scale, nature and habits of the shipyard.

In the past, in addition to steel processing, hull assembly, welding and equipment system installation, many shipyards also had a certain capacity of casting, forging and machining. In addition to hull manufacturing, they also manufactured main engines, auxiliary engines, boilers and other equipment. Since the 1950s, with the development of shipbuilding and its supporting industries, shipyards have developed towards the direction of final assembly, that is, hull construction is the main, a large number of mechanical and electrical equipment and outfitting parts are provided by professional or non-professional cooperative plants, shipyards only installation, in order to improve the quality and efficiency of shipbuilding.

The main process of shipbuilding can be represented by the block diagram below.

Steel pretreatment The rectification, derusting, and priming of steel prior to marking. Marine steel often has various deformation due to uneven rolling, uneven cooling shrinkage after rolling or other factors in the process of transportation and storage. For this reason, after the plate and profile are taken out from the steel yard, they are first corrected by the multi-roll steel plate leveler and the section steel straightener to ensure the normal process of marking material, edge and forming. The corrected steel is usually polished first, then primed and dried. The finished steel in this way can be sent to the marking material. These processes are often composed of automatic preprocessing lines, which connect the conveyor raceway with the transportation lines of steel material lifting, marking material, edge processing and other subsequent processes of the steel material storage yard, so as to realize the comprehensive mechanization and automation of the material preparation and processing of hull parts.

Lofting and marking hull shapes are usually smooth spatial surfaces. The hull outline drawing provided by the design department with three projection lines, called the line chart, is usually drawn at a scale of 1:50 or 1:100. Due to the large scale ratio, there is some error in the three-way smoothness of the profile line, so the hull construction cannot be carried out directly according to the profile diagram. Instead, 1:1 full scale lofting or 1:5, 1:10 proportional lofting should be carried out in the shipyard lofting table to smooth the profile and obtain the correct profile value and the actual shape size and position of each part required in the construction. Provide necessary construction information for subsequent process. Hull lofting is the basic procedure of hull construction.

Marking material refers to marking the actual shape and size of the hull parts obtained after lofting on the plate or profile using the template, sample material or sketch, and marking for processing and assembly. The earliest method of lofting and marking material is full scale lofting and manual marking material. In the early 1940s, proportional lofting and projection marking appeared, that is, lofting at the ratio of 1:5 or 1:10 to make projection base map, which was enlarged to actual size with the corresponding low-power projection device; Or reduce the projection base map to 1/5~1/10 to make a projection negative, and then use a high-power projection device to enlarge 50~100 times to form parts, and then line on the steel. Proportional lofting can also provide a copy diagram for the photoelectric tracking cutter to directly cut the steel plate, thus eliminating the ellipsis process. Although the projection marking material has been greatly improved on the basis of the manual marking material, it still cannot get rid of manual operation. In the early 1960s, electroprinting materials began to be applied, that is, the principle of electrostatic photography was used to spray photosensitive conductive powder on the surface of the steel plate first, and positive projection exposure was carried out. After developing and fixing, parts graphics were shown on the steel plate. The large electric printing material device suitable for large size steel plate adopts synchronous continuous exposure projection mode, that is, the bottom picture and the steel plate move synchronously, and the continuous projection exposure is made in the process of motion. It is suitable for the small electric marking device of small size steel plate, and all the graphics are projected on the steel plate at one time. This marking method has been widely used. With the application of electronic computer in shipbuilding, mathematical lofting method appears. The ship shape line or hull surface is represented by mathematical equation, the design type value table and the required boundary condition value are used as the original data, and the computer is used to carry out repeated check and calculation to achieve the modification of the shape line and smooth, so as to obtain the exact smooth and the corresponding projection point of the ship shape line. Each contour line of the hull is represented by a characteristic mathematical spline curve equation and can be graphed using a CNC plotter (see Drawing Tool). Mathematical lofting can cancel the traditional full-length lofting work and provide control information for the following processes such as cutting and forming. It plays a key role in the automation of hull construction process and is an important development of shipbuilding technology.

Hull parts machining includes edge machining and forming machining. Edge processing is in accordance with the actual shape of the hull parts drawn on the steel after the material, the use of scissors or oxyacetylene gas cutting, plasma cutting cutting. The edge of some parts also needs to be processed by gas cutting machine or edge planer for weld groove. The photoelectric tracking gas cutting function in the gas cutting equipment automatically tracks the lines on the scale drawing, and cuts on the steel plate through the synchronous servo system. It can be used in combination with manual marking material and projection marking material. The CNC gas cutting machine not only has high cutting precision, but also can cut directly according to the mathematical lofting data, which can simplify the material process and realize the lofting and cutting process automation.

For the hull plate with curvature, folding Angle or folding and other space shape, in the steel plate cutting also need to form processing, mainly the application of roller bending machine and rolling machine for cold bending; Or the processing method of water and fire forming, that is, on the plate according to the predetermined heating line with oxygen - acetylene drying torch for local heating, and water tracking cooling, so that the plate produces local deformation, bending into the required curved surface shape. For the profile used for ribs, the application of cold frame bending machine shape. With the development of digital control technology, the digital control frame cold bending machine has been used and then developed. Hull parts processing has progressed from mechanization to automation.

Hull assembly and welding The process of assembling the parts of a ship's structure into an entire hull. Segmental construction is generally adopted, which is divided into three stages: component assembly welding, segmental assembly welding and berth assembly welding.

① Component assembly welding: also known as small closing. The process of assembling the finished steel plate or section into plate row, T section, frame frame or ship head and stern column and other components is carried out on the welding platform in the workshop.

② points (total) section assembly welding: also known as in the close. Combine parts into plane segments, curved segments or three-dimensional segments, such as bulkhead, bottom, side and superstructure segments; Or combined into the captain in the direction of the main hull of the cross-sectional ring three-dimensional segment, known as the total section, such as the total bow section, total stern section, etc. Sectional assembly and welding are carried out on the welding platform or tire frame. The division of the section mainly depends on the characteristics of the hull structure and the lifting conditions of the shipyard. With the upsizing of ships and the increase of crane capacity, sections and total sections are also increasing, and their weight can reach more than 800 tons.

(3) Berth (dock) assembly welding: that is, hull assembly, also known as big close. The parts, sections and total sections of the hull are finally assembled and welded on the berth (or dock) to form the hull. Large ships with a displacement of more than 100,000 tons are usually assembled in shipyards to ensure launching safety. The commonly used assembly methods are as follows: the total section construction method, which takes the total section as the assembly unit and lifts from the middle of the ship to the bow and stern, is generally applicable to the construction of small and medium-sized ships; First lifting a bottom section at the partial stern of the ship, as the construction basis to the bow, stern and upper lift adjacent sections, the range of lifting is called tower construction method; There are two or three construction bases, respectively built in the tower construction method, and finally connected into the hull called island construction method; When the first ship is built at the end of the slipway (or dock), the tail of the second ship is built at the front end of the slipway at the same time. After the first ship is launched, the tail of the second ship is moved to the end of the slipway to continue hoisting other sections until the whole hull is assembled. At the same time, the tail of the third ship is built at the front end of the slipway, and so on. A two-stage construction method in which a ship's hull is divided into two sections, the first and the last, which are launched on the slipway and then closed on the water. The selection of various assembly methods depends on the characteristics of the hull structure and the specific conditions of the shipyard.

The workload of hull assembly and welding accounts for more than 75% of the total workload of hull construction, of which welding accounts for more than half. Therefore, welding is the key work in shipbuilding, which is not only directly related to the construction quality of the ship, but also related to the shipbuilding efficiency. Since the 1950s, the welding methods have developed from manual welding to submerged arc automatic welding (see submerged arc welding), semi-automatic welding, electroslag welding, gas shielded arc welding. Since the mid-1960s, there have been new technologies such as single-side welding double-sided forming, gravity welding, automatic fillet welding, and automatic vertical and transverse welding. Welding equipment and welding materials also have corresponding development. Because of the complex structure of the hull, manual welding is still needed in the position where it is difficult to implement automatic welding and semi-automatic welding.

Combined with the development of welding technology, T profile assembly line and plane sectional assembly line have been adopted respectively in hull parts and sectional assembly since 1960s. T section is the basic component of plane segment skeleton. Plane sections take a significant proportion in the hull structure. For example, on large bulk carriers and oil carriers, plane sections can account for more than 50% of the total weight of the hull. Plane segmental assembly line includes a variety of special assembly and welding equipment, it uses the conveyor device to continuously feed, plate welding and frame welding operations, can significantly improve the degree of mechanization of segmental assembly, has become one of the main contents of modern shipyard technological transformation. Some shipyards in the world also adopt the assembly line production method for assembly welding and dock assembly of the three-dimensional segment of large oil tanker in mass production.

After the final assembly of the hull, the airtight test must be carried out on the hull, and then the shafting and rudder system must be matched in the tail, and the shafting, propeller and rudder must be installed. Prepare for launching after completing various underwater works.

The process of moving a ship from land to water after it has been assembled on a berth (dock). When a ship is launched, its direction of shift is either parallel to or perpendicular to the captain, which are called longitudinal launching and transverse launching respectively. The launching slipway is mainly wooden beam slipway and mechanized slipway. The former is widely used for sliding into the water depending on the ship's own weight. The latter uses the trolley to carry the hull on the track to pull the launch, which is often used in the small and medium-sized shipyard of inland river.

Before longitudinal launching, the hull resting on the pier is transferred to the slide board and the slipway, which inclines to the direction of the ship entering the water. When the brake device arranged between the slide board and the slide way is released, the ship slides into the water together with the slide board and support due to its own weight, and then floats on the surface of the water by its own buoyancy. In order to reduce the friction resistance during sliding, a certain thickness of grease is often applied between the slide and the slide; Steel balls can also be used to replace grease in the water, to change sliding friction to rolling friction, further reducing friction. When the ship is assembled in the dock, it can float as long as the water is poured into the dock, and its launching operation is much simpler and safer than launching under the slipway.

Launching means that the construction of the ship has completed the key and main work. According to the traditional custom, the launch of large ships often held a grand celebration ceremony.

Quay installation (installation of equipment and systems) After launching a ship is usually docked at the outfitting quay in the plant for the installation of hull equipment, mechanical and electrical equipment, pipes and cables, as well as the woodwork, insulation and painting of cabins. Dock installation involves many kinds of work, and the mutual influence is great. With the increasing complexity of ship equipment and system, the requirements of installation quality are also increasing. Therefore, the installation work is directly related to whether the ship can be quickly tested and delivered after launching. In order to shorten the installation period after launching, the above installation work should be carried out as far as possible in advance to the stage of sectional assembly and hull assembly, known as pre-outfitting. The installation cycle can also be greatly shortened by changing the traditional single-piece installation to unit assembly, which determines the degree of composition of the installation unit according to the layout and composition characteristics of the machinery room and other cabin equipment. For example, the main engine cooling unit may include heat exchangers, pumps, temperature regulators, related pipes with accessories and the electrical equipment necessary for the unit. The installation unit is formed in the workshop, and then hoisted to the section, the whole section or the ship for installation. In this way, 18~25% of the installation work can be carried out from the ship to the infield in advance, and the installation cycle on the ship can be shortened by 15~20%.

After the completion of the construction and installation of the hull, in order to ensure the completeness of the construction and the reliability of various equipment, a comprehensive and strict test must be carried out, which is usually divided into two stages, namely, the mooring test and the sailing test.

Mooring test, commonly known as dock trial, is a series of practical tests carried out on the main engine, auxiliary engine and other mechanical and electrical equipment of the ship in the mooring state to test the installation quality and operation condition. Mooring test takes main engine test as the core to check the working condition of generator set and distribution equipment, so as to create conditions for the test of main engine and other equipment. Reliability and safety tests are also required for coordination, emergency response, telemetry and automatic control of all relevant systems. During the mooring test, the ship is basically in a static state, and the main engine, shafting and related equipment system cannot show the performance of full load operation, so the voyage test is still needed.

The voyage test is a comprehensive examination of the performance of the main engine, auxiliary engines and various mechanical and electrical equipment and systems under the voyage condition. There are usually light load trials and heavy load trials. The ship's speed, power of the main engine, maneuverability, rotation, course stability, inertia and seaworthiness of the designated navigation area are measured during the voyage test. Test results After the ship organization and the user pass the acceptance, the shipyard will formally deliver the goods to the orderer for use.

The development of modern shipbuilding technology is a process from manual operation to mechanization and automation. Since the 1950s, welding has replaced riveting in hull construction, which has improved hull construction from piecewise bulk in the past to piecewise assembly, greatly improving shipbuilding efficiency. Due to the complex structure and shape of hull, manual operation has been a large proportion in hull construction. The application of electronic computers and numerical control technology is further changing the face of shipbuilding. Electronic computers are first applied to mathematical lofting, and then appear digital input and graphic output of CNC plotter, CNC cutting machine, CNC frame cold bending machine, CNC propeller machining machine and pipe machining machine. At the same time, electronic computing technology has been gradually applied in production management, planning, material and equipment supply and cost accounting in shipyards. In order to reduce the information preparation and eliminate the disconnection between design and production, a large shipbuilding integrated numerical control system has been developed, which includes the general information of ship design, production and management, and can coordinate the whole working process from design to production. Therefore, expanding the application of computer in shipbuilding is the main direction of developing shipbuilding technology and improving the degree of shipbuilding automation.