The difference between safety valve and pressure relief valve

[1] Simply put, the pressure relief valve to prevent the system exceeds a certain value, is mainly used to protect the system, the valve is to reduce the system pressure from a high pressure to the appropriate value required for its export pressure a range, as long as this range can be.
[2] Safety valve: valve is opening and closing pieces by the external force is normally closed state, when the device or media pressure inside the pipe rises above a predetermined value, by medium pressure pipeline or equipment to the outside of the system to prevent the emission medium special valve exceeds a predetermined value. Safety valves are automatic valves, mainly used in boilers, pressure vessels and piping, control pressure does not exceed a predetermined value, for personal safety and equipment operation plays an important protective role. Note the safety valve must be pressure tested before use.
[3] valve: valve by regulating the inlet pressure is reduced to the outlet pressure of a need, and rely on the energy of the medium itself, so that automatically maintain a stable outlet pressure valve. From the point of view of fluid mechanics, pressure reducing valve is a local resistance to change spending components, that is, by changing the throttle area, so that the kinetic energy of change velocity and the fluid, resulting in different pressure loss, so as to achieve the purpose of decompression. And then rely on regulation and control and regulation systems, so that the valve pressure fluctuations and the spring force balanced, so that the pressure after the valve