Steam pressure reducing valves are type of self operated valve that can auto reduce the downstream pressure of steam and self adjust the amount of valve opening to allow the pressure to remain the same even if the flow rate changes by pistons, springs or diaphragms. The pressure reducing valve adopts the opening and closing parts inside the PRV body to adjust the flow of the fluid, reduce the fluid pressure and adjust the opening degree of the opening and closing parts with the help of the pressure behind the valve, then the pressure behind the valve remains in a certain range, in the case of constant changes in the inlet pressure to keep the outlet pressure in the pre set range. To choose the right type of steam pressure reducing valve is very important. This leads to another question why steam needs pressure-reducing?