译文：
1．分类 　　目前大量生产的安全阀有弹簧式和杆式两大类。另外还有冲量式安全阀、先导式安全阀、安全切换阀、安全解压阀、静重式安全阀等。弹簧式安全阀主要依靠弹簧的作用力而工作，弹簧式安全阀中又有封闭和不封闭的，一般易燃、易爆或有毒的介质应选用封闭式，蒸汽或惰性气体等可以选用不封闭式，在弹簧式安全阀中还有带扳手和不带扳手的。扳手的作用主要是检查阀瓣的灵活程度，有时也可以用作手动紧急泄压用，如图3。杠杆式安全阀主要依靠杠杆重锤的作用力而工作，但由于杠杆式安全阀体积庞大往往限制了选用范围。温度较高时选用带散热器的安全阀。 　　安全阀的主要参数是排量，这个排量决定于阀座的口径和阀瓣的开启高度，由开启高度不同，又分为微启式和全启式两种。微启式是指阀瓣的开启高度为阀座喉径的1／40～l／20。全启式是指阀瓣的开启高度为阀座喉径的1／4。 2．安全阀的选用 　　由操作压力决定安全阀的公称压力，由操作温度决定安全阀的使用温度范围，由计算出的安全阀的定压值决定弹簧或杠杆的定压范围，再根据使用介质决定安全阀的材质和结构型式，再根据安全阀泄放量计算出安全阀的喉径。以下为安全阀选用的一般规则。 （l）热水锅炉一般用不封闭带扳手微启式安全阀。 （2）蒸汽锅炉或蒸汽管道一般用不封闭带扳手全启式安全阀。 （3）水等液体不可压缩介质一般用封闭微启式安全阀，或用安全泄放阀。 （4）高压给水一般用封闭全启式安全阀，如高压给水加热器、换热器等。 （5）气体等可压缩性介质一般用封闭全启式安全阀，如储气罐、气体管道等。 （6）E级蒸汽锅炉一般用静重式安全阀。 （7）大口径，大排量及高压系统一般用脉冲式安全阀，如减温减压装置、电站锅炉等，如图8所示。 （8）运送液化气的火车槽车、汽车槽车、贮罐等一般用内装式安全阀，如图4所示。 （9）油罐顶部一般用液压安全阀，需与呼吸阀配合使用。 （10）井下排水或天然气管道一般用先导式安全阀，如图6所示。（11）液化石油气站罐泵出口的液相回流管道上一般用安全回流阀。（12）负压或操作过程中可能会产生负压的系统一般用真空负压安全阀。（13）背压波动较大和有毒易燃的容器或管路系统一般用波纹管安全阀。（14）介质凝固点较低的系统一般选用保温夹套式安全阀。

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原文：
1. Classification Current mass production of spring-loaded safety valve and the rod are two major categories. There are also impulse-type safety valve, pilot safety valve, safety valve switch, safety release valve, safety valve and other static weight. Spring safety valve spring force and rely mainly on the work of another spring-loaded safety valve in the closed and not closed, generally flammable, explosive or toxic media should use closed, steam or inert gas used is not closed type, in the spring-loaded safety valve in there with a wrench and without wrenches. Wrench key is to examine the role of the flexibility of the valve flap, and sometimes can also be used manually with emergency relief, in Figure 3. Lever-type safety valve lever hammer mainly depend on the force and work, but because of the huge volume of leveraged safety valve is often limited range of choice. Use at high temperature safety valve with radiator. The main parameter is the safety valve displacement, the displacement depends on the caliber of the valve seat and valve valve opening height, different from the opening height, then divided into Weiqi the entire Kai two. Weiqi is the valve opening height for the seat valve throat diameter of 1 / 40 ~ l/20. The entire Kai is the valve opening height for the seat valve throat diameter of 1 / 4. 2. Selection of safety valve Decided by the operating pressure safety valve nominal pressure, the decision by the operating temperature range of temperature safety valve from the computed value of the decision constant pressure safety valve spring or a lever set pressure range, then the safety valve according to the decision to use media materials and structure type, and then calculated according to the safety valve Discharge valve throat diameter. The following general rules for the safety valve of choice. (L) hot water boilers generally is not closed with a safety valve with a wrench Weiqi. (2) steam boiler or steam pipe wrench for general use is not closed with a safety valve. (3), water and other liquids with a closed incompressible medium Weiqi general safety valve, or safety relief valve. (4) the general use of closed high-pressure water safety valve, such as the high pressure feed water heater, heat exchanger. (5) gas and other compressible medium for general use closed safety valve, such as the gas tank, gas pipelines. (6) E-class steam boiler safety valve for general use of static weight. (7) large diameter, large displacement and high pressure systems typically use pulse valve, such as temperature and pressure reduction equipment, boiler, etc., shown in Figure 8. (8) transportation of liquefied gas tanker train car tanker, tanks and other general use built-in safety valve, shown in Figure 4. (9) hydraulic valve tank top general, be used in conjunction with the breathing valve. (10) underground water or gas pipelines generally use pilot operated relief valve, shown in Figure 6. (11) Liquefied petroleum gas station can pump liquid return pipe back to normal with the safety valve. (12) or negative pressure during operation may have negative pressure systems generally use vacuum relief valve. (13) back pressure and toxic volatile flammable container or piping systems are generally used bellows safety valve. (14) medium low freezing point of the system is generally used in thermal insulation jacket safety valve.