Application of Pressure Vessels

Petroleum, chemical, pharmaceutical and other products are produced according to certain technological processes and under certain conditions using matching machinery and equipment. With the advancement of science and technology and the development of industrial production, especially the continuous and stable pressure vessels in the national economic field have been used in petroleum, chemical, light industry, medicine, environmental protection, metallurgy, food, bioengineering and national defense and other industrial fields as well as people's daily life. It has been widely used, and the number is increasing day by day, and there are more and more large-volume equipment. For example, the production of urea requires pressure vessels such as synthesis towers, heat exchangers, separators, reactors, and storage tanks; processing crude oil requires rectification towers, heat exchangers, heating furnaces, etc. Pressure vessels; in addition, various tower equipment used for refining, analysis, absorption, extraction and other processes are also pressure vessels; various heat exchangers used for fluid heating, cooling, liquid vaporization, steam condensation and waste heat recovery are still It is a pressure vessel; the reaction equipment used in the polymerization, hydrogenation, cracking and other processes in the production of the three major synthetic materials in the petrochemical industry, and various equipment used for the storage, transportation and measurement of raw materials, finished products and semi-finished products are pressure vessels. According to statistics, about 80% of the equipment in chemical plants belong to the category of pressure vessels.

There are many types of pressure vessels and complex operating conditions, including vacuum vessels, high-pressure and ultra-high pressure equipment and nuclear energy vessels; the temperature also has a wide range from low temperature to high temperature, and most of the treated media are corrosive, or flammable, explosive, and toxic. , even highly toxic. This variety of operating characteristics has brought complexity to the pressure vessel in terms of material selection, manufacture, inspection, use, maintenance and management. high demands.

Pressure vessels involve multiple disciplines and are highly comprehensive. From the determination of parameters to the normal use of a pressure vessel, it can only be realized through the joint efforts of various engineering and technical personnel in many links and related departments.

Development of Pressure Vessel Manufacturing Technology

With the development of science and technology, the level of pressure vessel manufacturing technology is getting higher and higher, and its manufacturing progress is mainly manifested in four aspects.

1. The development of pressure vessels to large-scale

Large-scale pressure vessels can save materials, reduce investment, save energy, improve production efficiency, and reduce production costs. At present, the thickness of the coal gasification tower in the form of plate welding structure is 200mm, its inner diameter is 9100mm, and the quality of a single unit has reached 2500t; now the four key equipments of the annual output of 300,000 tons of synthetic ammonia and 520,000 tons of urea have been localized. The oil refining processing unit has also increased the processing capacity of crude oil from 250 X 104 t/a to 1000 X 104 t/a crude oil. In the storage and transportation of liquefied petroleum gas and chemical raw material gas, the horizontal storage tank has been able to produce φ7400mmX 38mmX 7400mm, and a single equipment can reach 600t. In the production of nuclear power equipment, 350MV nuclear reactor pressure vessels with a total weight of 380t and 1000MV nuclear power steam generators with a total weight of 345t have been produced.

In order to adapt to the manufacture of large containers, its manufacturing equipment has also been developed rapidly. At present, the lifting quality of a single crane has reached 1200t, the hydraulic press is more than 6000t, the plate rolling machine is more than 4000t, the thickness of cold bending is 380mm, the width is 6m, the diameter of the hot stamping head is 4.5m, and the thickness is 300mm. The heavy-duty spinning machine can process oval heads with a diameter of 7m and a thickness of 165mm.

2. Development of steel for pressure vessels

Due to the large-scale pressure vessels and the increasingly harsh process conditions in the production process, the requirements for the steel used for pressure vessels are becoming more and more stringent, thus promoting the continuous development of material technology. Crack resistance and toughness index of steel. Strength is guaranteed by reducing carbon content and increasing trace alloying elements, while crack resistance and toughness are guaranteed by improving smelting technology to reduce impurities. At present, the smelting technology in Japan can reduce the phosphorus content to below 0.01% and the sulfur content to below 0.002%. With the continuous development of smelting technology, steel plates with good weldability under large line energy have appeared, and the use of clad steel plates has become more and more common. With the development of hydrogenation process technology, especially coal hydrogenation and liquefaction process, the anti-oxidation ability, creep resistance, high service temperature limit and tensile strength of steel can no longer meet the requirements. Cr-Mo-V hydrogen resistant steel. In order to ensure the safe use of pressure vessels in some corrosive environments, there are more and more applications of duplex stainless steel, Ni-based stainless steel, Hastelloy and other materials.

3. Development of pressure vessel manufacturing methods

The traditional manufacturing methods of pressure vessels mainly include forging, coil welding, wrapping, and heat sleeve. In 1981, Germany introduced a new method of welding forming technology for the first time, using multi-wire submerged arc welding to manufacture pressure vessels. The emergence of this new technology adds a fourth manufacturing method-welding manufacturing to the three traditional manufacturing methods of original casting, forging and rolling.

4. Generation and application of new welding materials and new technologies

In order to improve the fracture toughness of high-strength steel, the hydrogen content in the weld must be reduced, so the development and use of ultra-low hydrogen materials have attracted the attention of container manufacturers. The UL series ultra-low hydrogen electrode developed by Kobelco Corporation can reduce the crack arrest temperature by 25-50 during use. C, at the same time, its hygroscopicity is very small, and the management is also very simple. The steel used for pressure vessels in my country has transitioned from simple carbon steel to ordinary low-alloy steel, and then developed to low-temperature steel, high-strength steel and special steel. At present, Cr-Mo-V hydrogen-resistant steel can be used to manufacture hydrogenation reactors.

In addition, automatic welding technology and welding robots automate the welding of large containers, improve welding quality and efficiency, and reduce the labor intensity of workers. In terms of automatic welding equipment, automatic welding machines with tracking weld systems have appeared. And can use numerical control technology to control welding parameters, use industrial TV to monitor the welding process and so on. Light heating furnaces also appeared in heat treatment methods, spray and immersion methods also appeared in quenching process, and internal combustion and local heating annealing appeared in annealing. Local heating methods such as power frequency electric heating, resistance heating and infrared heating are also widely used.