First, on the pressure vessel
Pressure vessel is the production process, which is used to complete the process of reaction, heat transfer, separation, storage, etc. in the industrial production, and has the special function to bear certain pressure. Pressure vessel manufacturing industry is an important branch of general machinery manufacturing, and it is an important part of equipment manufacturing industry.
The pressure vessel is the basic work in the confined state, and the mediums of high temperature or flammable and explosive, extremely dangerous, so all countries in the world will be mandatory pressure vessel as special equipment management. The type and function of pressure vessels with different applications and change, the design, manufacture and use of the process, involving metallurgical structure design, machining, welding, heat treatment, nondestructive testing technology, automation and other professional categories. Therefore, the technological development of the pressure vessel is based on the comprehensive development of the professional technology.
Two, the development direction of the pressure vessel body
Along with the international economy, the technology trade exchanges gradually strengthens and the pressure vessel design, the manufacture and the use management maturity, the domestic and international pressure vessel development gradually presents the following several directions:
1, universal and standardization
The generalization and standardization of pressure vessels have become an irreversible trend. This is because the general and standardized means that the exchange of the increase, which is not only conducive to the use of pressure vessels to use the unit daily maintenance and logistics, but also to maximize the design and manufacturing costs. At the same time, for export countries like us, standardization also means to get a pass to the international. From the practice of export pressure vessels the world within the scope of the analysis we can see that the international engineering company can drive the pressure vessel industry development and the national standards of the international recognition, thereby gaining greater international voice and huge economic profits.
2, specialization and specialization
Although there are many advantages in general and standardization, but in this type of pressure vessel can only be used in some ordinary occasions, in the work environment with special requirements must be used with special features of the pressure vessel. Such as nuclear reactor vessel, crystal processing container and rocket fuel tank, the pressure vessel must have strong corrosion resistance, high pressure resistance and high temperature resistance. It is these special needs that make pressure vessels develop and progress toward the direction of specialization and specialization.
(1) super high pressure vessel: it refers to the work pressure is greater than or equal to 100MP of the container, this kind of container in the ethylene polymerization, artificial crystal manufacturing and so on has been widely used. But it still has the problem of high cost and safety. Now with the emergence of new materials and metallurgical industry, the development of ultra-high pressure vessel pressure capacity and strength of the limit is also gradually increased, which will promote the further development of ultra high pressure vessels.
(2) high temperature pressure vessel: the so-called high temperature, usually refers to the wall temperature exceeds the container material creep starting temperature (for the general steel is about 350 degrees Celsius). Boiler steam drum and coal conversion reactor of thermal power station, reactor pressure vessel of some reactor type (high temperature gas cooled reactor and breeder reactor) are high temperature pressure vessel. The creep of high temperature pressure vessel will produce the slow change of shape and size. Material in the long-term effect of high temperature, its lasting strength is much lower than the short time tensile strength. Therefore, the main basis for the selection of materials is the high temperature lasting strength and corrosion resistance. The stress analysis of high temperature pressure vessel is more complicated, and the theoretical solution is difficult. Modern practice shows that it is feasible to use the finite element method. If the container is subjected to alternating loads (such as repeated boost and Buck), the interaction between fatigue (see fatigue strength design) and creep should be considered.
(3) strong corrosion resistance of pressure vessel due to pressure vessel with acid, alkali, salt and other corrosive media contact, not only the corrosion caused by material consumption, but also causes damage to the equipment, raw materials and product loss, environmental pollution, and even cause poisoning, fire and explosion accidents. If the transport of sulfuric acid, hydrochloric acid tank, not only to have a strong corrosion resistance, but also the requirements of its security is very strict, this is not a general pressure vessels to meet the.
(4) low temperature pressure vessel: it is mainly used in the preparation of liquid oxygen, liquid nitrogen storage medium, manufacturing process and low temperature superconductors, due to its working temperature is generally -100 degrees Celsius or lower, then the crystal structure of the material will change, causing the material strength and ductility decreased greatly, which brings hidden trouble to the safe operation. This requires that the pressure vessel must be paid attention to in the selection of materials.
(5) in addition, there are large and small containers of such special applications.
Three, pressure vessel professional technology development direction
Pressure vessel is a comprehensive product involving many industries and many disciplines, and its construction technology involves many industries, such as metallurgy, mechanical processing, corrosion and corrosion protection, nondestructive testing, safety protection and so on. Along with the development of metallurgy, mechanical processing, welding and non-destructive detection technology continues to progress, especially the rapid development of computer technology as represented by information technology, led to the development of related industries, based in the world invested a lot of manpower and resources to conduct in-depth research on the technology of pressure vessels has made some progress. In order to produce and use more secure and more economical pressure vessel products, the traditional design, manufacture, welding and inspection methods have been and are being replaced by new technologies and products in different degrees.
1. Technical progress of materials used in pressure vessels
In recent years, pressure vessel with large scale and parameter tendency of hydrogenation reactor, thousands of tons of coal liquefaction reactor, two thousand tons of ten thousand cubic meters of natural gas spherical tank (Japan's largest natural gas spherical tank of thirty thousand cubic meters) has been in China a large number of applications, application of pressure vessel the petroleum chemical industry, nuclear industry, coal chemical industry in the increasingly harsh. Therefore, the research and development of materials for high temperature, high pressure and corrosion resistance of pressure vessels has been a major issue faced by the pressure vessel industry. In this regard, the country has invested a lot of manpower and material resources to engage in related research work. At present, the main research achievements and technical progress of the materials used in the pressure vessel are shown in the following aspects:
(1) high purity materials: metallurgical industry overall level of technology and equipment to improve the level of,Greatly improve the purity of the materials, improve the mechanical properties of the pressure vessel materials, and improve the overall safety of the pressure vessel.
(2) applicability of media materials: for all kinds of corrosive media and operating conditions, has developed the super stainless steel, dual phase steel, special alloy and other metal materials, which is suitable for various application conditions, which gives the designer more choices of space for long period safety production guarantee.
(3) the application of the material boundaries: for high temperature creep, temper embrittlement, low temperature brittle fracture of the research, the application of the material accurately.
(4) a high strength material in large-scale equipment requirements, traditional materials have been unable to solve such as 30 thousand cubic meters of natural gas tanks, steel large spherical tank, 200 thousand cubic meters of crude oil storage tank and material of super high pressure vessel. At present σ b≥ the application of 800MPa high strength material is attracting the attention of domestic researchers.
2, the wide use of computer technology
In the information age today, the application of computer technology has penetrated into every field of pressure vessel industry. Computer software and hardware, each of which has greatly influenced the development of the pressure vessel industry:
(1) design: traditional computer aided design (CAD) has been gradually developed to the direction of Computer Aided Engineering (CAE). With the constant enhancement of the ability of computer and analysis means of increasing diversity, problems in the structure design stage, designers can foresee the residual generated in the welding process such as collision may occur stress, equipment assembly and transport process, and eliminate these problems in the design phase, design and structure optimization design and analysis has been gradually as the designer master.
(2) manufacturing: computer aided manufacturing (CAM) technology is gradually changing the traditional process of pressure vessel manufacturing plant, quality management awareness and production methods have had a profound change. The computer management of pressure vessel makes the whole process of all the control points can be effectively controlled, greatly reduce human error, effectively ensure the stability of the product quality, reduces the production cycle and production cost.
(3): the application of computer controlled welding machine, laser welding machine and profiling of all position automatic welding machine, greatly improve the production efficiency and product quality.
(4) non destructive testing: the application of computer - ray real - time imaging, ultrasonic scan imaging and multi - channel acoustic emission technology, and then with a specially developed expert system, to make the results more accurate and objective. Especially the search technology to simulate the ultrasonic scanning imaging defects (TOFD) has been successfully used for nuclear equipment, heavy vessels for hydrogenation reactor in a thickness greater than 100mm. It plays a positive role in improving the production efficiency and reducing the pollution of the heavy vessels. In the construction of the reactor of coal liquefaction plant, the technology is applied to solve the problem of non destructive testing in the field.
3, structural design
The structure design of pressure vessel is gradually getting rid of the shackles of the traditional concept, and embody the design concept that really satisfies the technological requirements, and the pursuit of effectiveness, safety and economic harmony.
(1) the rationality of structural design: the specific structure of pressure vessel standards are not restricted, so the structure of pressure vessel are less constrained for designers to play a lot of space, help design a more reasonable structure. In addition, the application of the design method and the implementation of the verification test provide the necessary guarantee for the rationality of the structure design. The modular design method for example, it is in accordance with the components of pressure vessel components with different functions will perform the same function as a whole to study, like the safety protection device, tank, it not only makes the pressure vessel maintenance more convenient, but also can shorten the development cycle in the a large extent, accelerate technological upgrading.
(2) the economic design of the structure: the harmony of the safety and economy of the pressure vessel has always been the pursuit of the designers. The use of welded steel pipe and the application of special structure, to a large extent, is to consider the economic structure of the pressure vessel.
(3) reliability design: safety coefficient design method for traditional &ldquo insurance; ” reasons, often safety coefficient is too large, the pressure vessel and the structure and size of the parts design is too large, not only waste materials, but also because of the various parts of the life and strength to guarantee the reasonable matching results the final product caused by 1+1< 2. The treatment will be part of the reliability design parameters as random variables, and carries on the statistics to establish a statistical model, using probability statistics method to scan all the design object, the results accord with the situation of the world.
4, reduce the safety factor
In order to increase the competition of domestic products, reduce the safety factor is a general tendency of Pressure Vessel Standards of the countries and regions of the world at present, our country also put forward specific materials according to the analysis of safety coefficient NB design method is reduced to 2.4 of the proposal. The reduction of safety coefficient related to the pressure vessel standard foundation, a great impact on the economy and safety of pressure vessel industry, must be cautious. The premise of reducing the safety factor is:
(1) the improvement of the level of structural analysis and design.
(2) the accumulation of manufacturing experience and the improvement of manufacturing technology level.
(3) more stringent technical requirements for materials.
(4) more scientific quality assurance system.
Four, pressure vessel industry development trend
The world has entered the era of economic globalization, an inevitable trend of economic globalization is the internationalization of the standard. Europe and the United States and other major economic entities to compete for the right to dominate the market as the main target, put a lot of manpower and material resources, the introduction of a new content in the standard technology.
1, the internationalization of industry standards
International standard is the standard technology content and international standard compatibility, rather than simply copy the contents of all international standards. The international standard should be carried out systematic analysis and study, in line with international standards in the basic requirements, highlight their unique technology and management in the special issue, the final stage of implementation of mutual recognition between the standards.
(1) Convergence: Information TechnologyThe rapid development of the advanced technology in the world within the scope of the rapid popularization, around the technology standard technology development is also inevitable for technical users to accept, so the pressure vessel technology in the world is moving towards a unified direction of development.
(2) compatibility: Although the technical standards of various countries in the world are not exactly the same, but all countries have their own standards and other standards as the goal, in order to achieve the mutual recognition of standards. ASME (Japanese standard) is a research project in 1999, the PED (European standard) to conduct a thorough analysis, and the ESR and VIII-1 PED are a systematic comparison of the design, construction and administrative requirements, that can meet the requirements of PED ASME standard after adding some content.
(3): trade is an important basis for the standard part and Trade Arbitration Rules of international trade, the international standard will be conducive to master the essence to obtain a large market share and the economic benefits of the implementation of international standardization strategy is for control of the international market.
2, technical regulations and technical standards of mutual coordination
The state's technical regulations are mandatory for the state to ensure the safety of pressure vessel products. Any product within its jurisdiction must comply with its safety principles. The technical standard is recommended, regulations to ensure the quality index of the product technology of the corresponding pressure vessel safety, but the technical indicators of the provisions of the standard should be consistent with the principles of safety technical regulations, design, construction, can guide the pressure vessel inspection and acceptance, is a technical assessment of pressure vessel product construction and trade platform. Therefore, technical standards and technical regulations should be overall coordination, but there is a difference in the role and other aspects.
(1) the principle and engineering safety requirements: the basic technical regulations under the jurisdiction of the product standard; in addition to meet these basic requirements, but also meet the basic safety requirements stipulated specific methods and qualified indexes in engineering. The number of technical regulations rarely, but a wide range of jurisdiction; coordinate standard matching involves calculation method, design materials, forming, welding, nondestructive testing, pressure testing and a series of technical standards.
(2) the stability and effectiveness of technical regulations of the state is a part of the national administrative regulations, its content is relatively stable constant safety management of industry standard is favorable, and coordination of technical regulations, product safety and quality to keep pace with the times, always reflect the comprehensive ability of industry development and the corresponding technology.
Therefore, the study of the coordination between technical regulations and technical standards, clear technical regulations and technical standards to define the scope, should give full attention to the relevant state agencies.
3, the industrialization of the market and production specialization
The competition will inevitably lead to the change of production mode, and form the industrial organization structure with the core enterprise as the leading role, the coordinated development of the large and medium-sized enterprises, and the level of competition. Supporting the market and specialized production is the main pattern in pressure vessel industry, but also the development direction; strengthening the standardization work and contribute to the realization of specialization and cooperation, the emphasis on the industrial organization structure supporting the market and specialized production must be highly unified technology for the standardization, is precisely the basis for realization of technology unified therefore, the standard is the bridge and link of professional cooperation.