压力容器的设计与实践(Pressure Vessels Design and Practice).pdf
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1、chapter one Overview of pressure vessels Contents 1.1Introduction. 1.2Development of pressure vessel construction codes. References . 1.1Introduction Vessels, tanks, and pipelines that carry, store, or receive fl uids are called pressure vessels. A pressure vessel is defi ned as a container with a p
2、ressure differential between inside and outside. The inside pressure is usually higher than the outside, except for some isolated situations. The fl uid inside the vessel may undergo a change in state as in the case of steam boilers, or may combine with other reagents as in the case of a chemical re
3、actor. Pressure vessels often have a combination of high pressures together with high temperatures, and in some cases fl ammable fl uids or highly radio- active materials. Because of such hazards it is imperative that the design be such that no leakage can occur. In addition these vessels have to be
4、 designed carefully to cope with the operating temperature and pressure. It should be borne in mind that the rupture of a pressure vessel has a potential to cause extensive physical injury and property damage. Plant safety and integrity are of fundamental concern in pressure vessel design and these
5、of course depend on the adequacy of design codes. When discussing pressure vessels we must also consider tanks. Pressure vessels and tanks are signifi cantly different in both design and construction: tanks, unlike pressure vessels, are limited to atmospheric pressure; and pressure vessels often hav
6、e internals while most tanks do not (and those that do are limited to heating coils or mixers). Copyright 2005 by CRC Press, Inc. All Rights Reserved. Pressure vessels are used in a number of industries; for example, the power generation industry for fossil and nuclear power, the petrochemical indus
7、try for storing and processing crude petroleum oil in tank farms as well as storing gasoline in service stations, and the chemical industry (in chemical reactors) to name but a few. Their use has expanded throughout the world. Pressure vessels and tanks are, in fact, essential to the chemical, petro
8、leum, petrochemical and nuclear industries. It is in this class of equipment that the reactions, separations, and storage of raw materials occur. Generally speaking, pressurized equipment is required for a wide range of industrial plant for storage and manufacturing purposes. The size and geometric
9、form of pressure vessels vary greatly from the large cylindrical vessels used for high-pressure gas storage to the small size used as hydraulic units for aircraft. Some are buried in the ground or deep in the ocean, but most are positioned on ground or supported in platforms. Pressure vessels are us
10、ually spherical or cylindrical, with domed ends. The cylindrical vessels are generally preferred, since they present simpler manufacturing problems and make better use of the available space. Boiler drums, heat exchangers, chemical reactors, and so on, are generally cylindrical. Spherical vessels ha
11、ve the advantage of requiring thinner walls for a given pressure and diameter than the equivalent cylinder. Therefore they are used for large gas or liquid containers, gas-cooled nuclear reactors, containment buildings for nuclear plant, and so on. Containment vessels for liquids at very low pressur
12、es are sometimes in the form of lobed spheroids or in the shape of a drop. This has the advantage of providing the best possible stress distribution when the tank is full. The construction of a typical pressure vessel is shown in Figure 1.1. A spherical pressure vessel is shown in Figure 1.2. This i
13、s a special pressure Figure 1.1 Typical pressure vessel. Copyright 2005 by CRC Press, Inc. All Rights Reserved. ? vessel and is really a storage sphere. Functionally it acts as a tank because its purpose is to store a fl uid. However since it does so at pressures above atmospheric, it can be classif
14、i ed as a pressure vessel. This however does not have internals and operates at atmospheric temperatures. A horizontally supported cylindrical pressure vessel with a hemispherical head and conical transition is shown in Figure 1.3. This consists of a cylindrical main shell, with hemispherical header
15、s and several nozzle connections. The vessel geometries can be broadly divided into plate- and shell-type confi gurations. The plate-type construction used in fl at covers (closures for pressure vessels and heat exchangers) resists pressure in bending, while the shell-types membrane action operates
16、in a fashion analogous to what happens in balloons under pressure. Generally speaking the shell-type construction is the preferred form because it requires less thickness (as can be demonstrated analytically) and therefore less material is required for its manufacture. Shell-type pressure components
17、 such as pressure vessel and Figure 1.2 Spherical pressure vessel. Figure 1.3 Horizontally supported pressure vessel. Copyright 2005 by CRC Press, Inc. All Rights Reserved. ? heat exchanger shells, heads of different geometric confi gurations, and nozzles resist pressure primarily by membrane action
18、. Pressure vessels are made in all shapes and sizes, from a few centimeters (cm) in diameter to 50 meters (m) or more in diameter. The pressure may be as low as 0.25 kilopascals (kPa) to as high as 2000 megapascals (MPa). The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel
19、 Code, Section VIII, Division 1,1 specifi es a range of internal pressures from 0.1 MPa to 30 MPa. Pressure equipment, such as the American Petroleum Institute (API) storage tanks are designed to restrict internal pressure to no more than that generated by the static head of the fl uid contained in
20、the tank. A few more examples are provided in this chapter. In the area of nuclear power generation a number of coolant systems are used. The two plant cycles most often found in nuclear power plants are the pressurized water reactor and the boiling water reactor. The pressurized water reactor insid
21、e the reactor pressure vessel is subjected to a high coolant water pressure. The pressurized water is heated and the pump circulates the water through a heat exchanger (steam generator) where the steam for the turbine is generated. The part of the nuclear power plant containing the reactor coolant i
22、s called the primary circuit. Included in the primary circuit is an important vessel called the pressurizer. The coolant volume varies when the load changes require reactor coolant temperature changes, and when this occurs, the pressurizer serves as the expansion tank in the primary system, which al
23、lows the water to undergo thermal expansion and contraction keeping the primary circuit pressure nearly constant. If the pressures are allowed to fl uctuate too far, steam bubbles might form at the reactor heating surfaces; these bubbles or voids if formed inside the reactor core greatly alter react
24、or power output. The pressurizer has electric heating elements located low inside to provide the vapor needed to cushion the fl owing liquid coolant. All of these items are included in the primary circuit. Figure 1.4 shows a pressurized water reactor (PWR) vessel. A PWR steam generator and a PWR pre
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