Machine tool equipment reliability is the key to nuclear power processing equipment

The nuclear island portion is mainly composed of a reactor core, a steam generator, a voltage regulator and a main pump, wherein the reactor core includes a pressure vessel, a nuclear fuel bundle, a driving mechanism and the like. The conventional island is composed of a water pump, a steam separator, a steam turbine, a generator, a steam condenser, and the like. In addition, there are auxiliary equipment that support the normal operation of the system and ensure the safety of the reactor. These are the main components of nuclear power plant equipment.

The manufacture of the main components of these equipment can be divided into the following types, which require different machine tools for processing.

Large drum-type components such as a pressure vessel casing, a steam generator casing, and a pressure regulator casing basically belong to a drum-shaped member having a head at both ends, but the diameter and height are different. The diameter of the pressure vessel and steam generator depends on the size of the nuclear power plant generator set.

At present, it mainly produces millions of kilowatt-class nuclear power equipment. The pressure vessel has a diameter of 5 to 8 m or more and a length of about 20 m. It is divided into 4 to 5 sections and welded. The material is special steel. The blank is a cylindrical forging that requires 10,000 tons of press forging. Subsequent cutting operations require ultra-heavy-duty CNC vertical lathes, super-heavy-duty CNC horizontal lathes, large mast multi-axis linkage CNC boring and milling machines, CNC gantry boring and milling machines, and five-axis linkage turning and milling centers. These devices are large in size and have no special requirements for machining accuracy, spindle speed and rapid movement. However, due to the high cost of these workpieces and the absence of spare parts, the required yield must be 100%, so the reliability and stability of the machine tool are Very high demand.

A nuclear power plant requires more than 200 different types of pumps of various types, all of which are centrifugal pumps. The main pump (Class 1 pump) is a key component located in the heart of the nuclear island. It is the key to the nuclear power operation to control the water cycle. It belongs to the primary equipment of the nuclear power plant, and each steam generator has a main pump.

The structure of the main pump in the nuclear island is not more complicated than other pumps, but it is extremely demanding and requires absolute reliability. It is the only equipment in the nuclear reactor that cannot be done at present. It is completely dependent on imports, mainly because the main pump requires continuous operation of at least 30. No problems are allowed in the year. The main pump has a diameter of about 2m and a height of 5 to 6m. Its main components are divided into two categories: pressure-bearing components (including pump body, pump cover, main bolt, main nut, etc.) and functional components (including impellers, leaf shafts, seals, etc.). ). At present, Shengu is co-developing with Westinghouse, and the overall new design has not yet been completed. In addition to the first-stage main pump, there are a variety of 2-stage and 3-stage pumps. The names and functions of the various pumps are different, but the principle is basically the same. Such as the safety shell spray pump, the pump is not used normally, only in the event of a fault, it is required to start within 6 seconds to cool down. The processing of these pumps basically includes the processes of turning, milling, boring, drilling, tapping and the like.

The pump body and pump cover processing equipment for pressure-bearing parts mainly include large-scale CNC vertical lathes, CNC floor-type milling and boring machines, and gantry machining centers. Machining of main bolts and main nuts is more demanding than general bolts and nuts, but it is mainly due to material and tool selection problems.

The equipment required for the impeller and impeller shaft machining in the functional components mainly includes a five-axis linkage machining center, a CNC lathe, and a large-scale CNC horizontal lathe.

The conventional island part is mainly composed of a steam turbine unit, a generator set, a water pump, a steam separator and the like. The principle and structure of nuclear power steam turbines are the same as those of thermal power (burning coal) steam turbines. The difference lies in the steam turbines with the same generating capacity. The diameter of nuclear steam turbines is larger than that of thermal power steam turbines, and the materials used are also partially different. Manufacturing requirements are higher. The main processing parts are blades, stators, rotors, etc. The main processing machine has different models for processing blades (maximum blade length over 1600mm) 4~5 axis linkage machining center, CNC heavy duty horizontal lathe for machining rotor, CNC root groove milling machine, CNC large-scale landing for machining stator Milling and boring machines, CNC gantry boring and milling machines, large stator special machine tools.

For example, a 600,000-kilowatt steam turbine rotor weighing more than 200 tons requires a heavy-duty truck with a diameter of 3.5 to 5.0 m and a length of 15 to 20 m. The machining of turbine blades requires a five-axis linkage machining center, and the processing of medium-pressure cylinders and high-pressure cylinders is required to be wide. CNC gantry boring and milling machine with 7.5~8m and length of 22m and heavy-duty CNC vertical lathe and CNC floor-standing milling and boring machine with diameter of 200~260mm. Under normal circumstances, the machine tools that can meet the needs of thermal power steam turbine processing can basically meet the requirements of nuclear power steam turbine processing. Among these machine tools, most of the small and medium-sized blade machining 4 to 5 axis machining center and rotor spindle machining CNC horizontal lathe, etc., can basically meet the requirements in China. However, CNC machine tools such as machining centers for large-scale blade machining and CNC root-groove milling machines rely mainly on imports.

In addition, the nuclear power generator is basically the same as the thermal power generator, and the processing equipment of the two is no different. Under normal circumstances, machine tools that can meet the needs of thermal power generator processing can basically meet the requirements of nuclear power generator processing. The main processing machines include CNC heavy-duty horizontal lathes for machining rotors, CNC rotor slot milling machines, CNC large-scale floor milling and boring machines for machining stators, and large-scale stator-specific machine tools. At present, in these high-end CNC machine tools, some machine tools can meet the needs in China, but some machine tools such as CNC rotor slot milling machines still rely on imports.

Machine tool accuracy restricts the development of wind power equipment

Wind power plant equipment mainly includes the following parts: gearbox (lifting box), generator set, blades, tower base and substation. At present, wind power generation is gradually developing to high-power units, requiring high reliability and long life cycle, so the accuracy and functional requirements of components are high.

With the development of wind power generation technology, the principle and structure of wind turbines are also changing. The future wind turbines are developing in the direction of simplification of structure and volume reduction. At present, China is developing gearless box wind turbines. For example, the Power Generation Equipment Engineering Research Center of Harbin Power Generation Equipment Group has developed gearless box variable pitch permanent magnet wind turbines, and is developing "variable frequency constant frequency wind turbines" and "direct drive variable speed wind turbines", etc. The asynchronous generator set driven by the gearbox has the advantages of low manufacturing cost, reliable operation and easy maintenance, and has independent intellectual property rights.

At present, the most production is gearbox wind turbines. Due to the complicated structure, the manufacture of various components requires different machine tools for processing.

The gearbox of the fan is mainly composed of a box, a planetary gear train and a shifting mechanism. The fan gearbox body is a large-sized box, and the diameter is about 2 to 3 m depending on the amount of power generation, and most of them are separated structures. The machining requires a CNC floor-type milling and boring machine with a diameter of about 160-250mm, a large horizontal machining center, and a gantry machining center. The machining accuracy is high. At present, the imported equipment is mainly used.

The gears in the gearbox are processed in large quantities and require large-scale production of large internal ring gears, cylindrical spur gears and helical gears. The main processing equipment is large-scale CNC vertical gear hobbing machine, CNC gear shaping machine, CNC gear grinding machine and so on. Among these gear processing machines, large-size CNC gear machine tools generally require high-efficiency, heavy-duty, heavy-cut, and rigid features, mainly relying on imports, and small and medium-sized domestically produced equipment. Among them, large-size, large-modulus gears and ring gears adopt CNC forming gear milling machine and CNC forming gear grinding machine. CNC forming gear milling machine requires large depth of cut, large feed and high rolling speed. CNC forming gear grinding machine requires precision of more than 5 grades, high degree of automation, automatic centering, automatic measurement, automatic shape modification and high stability. At present, the company that manufactures gearboxes for wind power in China mainly has Nanjing Gaojing Gear Co., Ltd. The production task of the plant is very busy. It can't fully meet the market demand after three shifts in the long run. Therefore, the processing equipment is required to be stable and reliable. At present, the gear processing machine used by the factory is basically imported equipment.

The principle and structure of the generator for wind power are basically the same as those of other generators such as thermal power. Most wind power generators use kilowatt-class generators, and the 10,000-kilowatt-class generators used in thermal power are classified into different levels. From the manufacturing point of view, there is not much difficulty. Enterprises that can manufacture thermal power generator sets can generally meet the requirements for manufacturing wind power generator sets. However, wind turbine generators require a service life of more than 20 years, which requires higher stability and reliability.

The blades of the fan are mostly made of composite materials such as epoxy glass fiber or carbon fiber. The blade design mainly uses full three-dimensional aerodynamic simulation and structural finite element simulation, and the vacuum infusion process is used for blade production. There is less machining and some parts need to be die cut.

The pitching mechanism of the blade mainly includes a pitch motor, a speed reducer and a pitch controller. There are no special requirements for manufacturing equipment, and domestic machine tools can meet the demand.

The main components of the yaw mechanism are large bearings with internal and external teeth, four small gears and shifting devices. This kind of large-sized bearing is currently not manufactured in China, mainly relying on imports. Domestic Tianma shares will develop and manufacture large bearings for yaw mechanisms. Its processing equipment is mainly some special machine tools and equipment with high requirements. For example, at CCMT2008, three large-scale CNC special-purpose machine tools exhibited by Qizhong CNC Equipment Co., Ltd. are equipment for processing large-scale gears for wind power.