“safety valve”和“relief valve”都可以称为安全阀，二者没有本质区别；不同之处在于relief valve【泄压阀】只是safety valve【安全阀】的一种类型而已。
1、safety valve：安全阀
A safety valve is a valve that acts as a fail-safe in a thermalhydraulics plant. An example of safety valve is a pressure relief valve (PRV), which automatically releases a substance from a boiler, pressure vessel, or other system, when the pressure or temperature exceeds preset limits. Pilotoperated relief valves are a specialized type of pressure safety valve.
安全阀是启闭件受外力作用下处于常闭状态，当设备或管道内的介质压力升高超过规定值时，通过向系统外排放介质来防止管道或设备内介质压力超过规定数值的特殊阀门。
2、relief valve：泄压阀
A relief valve is a pressure relief valve characterized by rapidopening or pop action, or by opening in proportion to theincrease in pressure over the opening pressure, depending on the application and may be used either for liquid or compressible fluid.
泄压阀是一种减压阀迅速开启或流行的动作，或在增加压力超过开启压力比例开放，根据不同的应用，可用于液体或可压缩流体。
3、区别：relief valve【泄压阀】是安全阀的一种，一般用于液体或可压缩流体；而safety valve【安全阀】则指控制设备或管道内的任何介质，包括液体或可压缩流体。
所以，“safety valve”和“relief valve”区别在于范围不同。
参考文献：维基百科
https://en.wikipedia.org/wiki/Safety_valve
