《外文翻译--气压系统及各种阀门的基本介绍》由会员分享，可在线阅读，更多相关《外文翻译--气压系统及各种阀门的基本介绍（6页珍藏版）》请在金锄头文库上搜索。
1、Pneumatic system and various valve basic introductionPneumatic systems use pressurized gases to transmit and control power. As the name implies, pneumatic system typically use air (rather than some other gas) as the fluid medium because air is a safe ,low-cost ,and readily available fluid. It is par
2、ticularly safe in environments where an electrical spark could ignite leaks from system components.In pneumatic systems, compressors are used to compress and supply the necessary quantities of air. Compressors are typically of the piston, vane or screw type. Basically a compressor increases the pres
3、sure of a gas by reducing its volume as described by the perfect gas laws. Pneumatic systems normally use a large centralized air compressor which is considered to be an infinite air source similar to an electrical system where you merely plug into an electrical outlet for electricity. In this way,
4、pressurized air can be piped from one source to various locations throughout an entire industrial plant. The compressed air is piped to each circuit through an air filter to remove contaminants which might harm the closely fitting parts of pneumatic component such as valves and cylinders. The air th
5、en flows through a pressure regulator which reduces the pressure to the desired level for the particular circuit application. Because air is not a good lubricant (contains about 20% oxygen ), pneumatics systems required a lubricator to inject a very fine mist of oil the air discharging from the pres
6、sure regulator. This prevents wear of the closely fitting moving parts of pneumatic components.Free air from the atmosphere contains varying amounts of moisture. This moisture can be harmful in than it can wash away lubricants and thus cause excessive wear and corrosion. Hence, in come applications,
7、 air driers are needed to remove this undesirable moisture. Since pneumatic systems exhaust directly into the atmosphere, they are capable of generating excessive noise. Therefore, mufflers are mounted on exhaust ports of air valves and actuators to reduce noise and prevent operating personnel from
8、possible injury resulting not only from exposure to noise but also from high-speed airborne particles.There are several reasons for considering the use of pneumatic systems instead of hydraulic systems. Liquids exhibit greater inertia than do gases. Therefore, in hydraulic systems the weight of oil
9、is a potential problem when accelerating and decelerating and decelerating actuators and when suddenly opening and closing valves. Due to Newtons law of motion (force equals mass multiplied by acceleration),the force required to accelerate oil is many times greater than that required to accelerate a
10、n equal volume of air. Liquids also exhibit greater viscosity than do gases. This results in larger frictional pressure and power losses. Also, since hydraulic systems use a fluid foreign to the atmosphere, they require special reservoirs and no-leak systems use air which is exhausted directly back
11、into the surrounding environment. Generally speaking, pneumatic systems are less expensive than less expensive than hydraulic systems.However, because of the compressibility of air, it is impossible to obtain precise controlled actuator velocities with pneumatic systems. Also, precise positioning co
12、ntrol is not obtainable. While pneumatic pressures are quite low due to pressures can be as high as 10,000 psi. Thus, hydraulics can be high-power systems, whereas pneumatics are confined to low-power applications. Industrial applications of pneumatic systems are growing at a rapid pace.Underneath i
13、ntroduction is widely used in all kinds of pneumatic system valve.Valve is a widely used mechanical product in each countrys economy. You can find valves commonly used in the following fields like oil, nature gas, coal, metallurgy, mining, refinery, pipe transportation, petrochemical, chemical, phar
14、macy, food production, power plant, water supply / drainage, heat supply, air supply, marine, vehicle, airplane, spacecraft, military, new tech, irrigation and many other flowing systems.There are self-driven valves and operated valves. Self-driven valves( like safety valve, relief valve, steam trap
15、, check valve ) are functioning by utilizing its mechanical design or the pressure, direction of its flow medium .Operated valves( like gate valve, globe valve, ball valve, butterfly valve ) are functioning by actuator( manual, electric, hydraulic, pneumatic etc. ) or the pressure , flow direction o
16、f its medium. Due to the differences of pressure, temperature, flow, and physical-chemical character of its medium ,there are different requirements in designing and applying the pipeline system .Therefore there are numerous types of valve. GAS VALVEFrom the air valve operating principles of view, air valve performance will directly affect the work of compressor tanks, air valve for the following requirements: resistance losses small. Air valve size and airflo
