The pressure reducing valve is a valve that reduces the inlet pressure to a certain required outlet pressure through adjustment, and relies on the energy of the medium itself to automatically maintain a stable outlet pressure. From the perspective of fluid mechanics, the pressure reducing valve is a throttling element whose local resistance can be changed. That is, by changing the throttling area, the flow velocity and the kinetic energy of the fluid are changed, resulting in different pressure losses, so as to achieve the purpose of decompression. Then rely on the adjustment of the control and regulation system to balance the fluctuation of the pressure behind the valve with the spring force, so that the pressure behind the valve remains constant within a certain error range.

Although the water flow through the pressure reducing valve has a large head loss, it is still energy-saving in general because it reduces water waste, makes the system flow distribution reasonable, and improves the system layout and working conditions. When the medium is steam, a pilot piston type pressure reducing valve or a pilot bellows type pressure reducing valve should be selected. For the convenience of operation, adjustment and maintenance, the pressure reducing valve should generally be installed on a horizontal pipeline.