What is the purpose of a pressure reducing valve?

The function of PRV is to supply gas at set pressure as per the design conditions. Suppose the upstream O2 pressure is 30 Bar and we need constant pressure of 12 Bar down stream. So we need a microprocessor controlled PRV to sense the down stream pressure and always it will close or maintain the system pressure to set value of 12 bar.

It is to be noted that initial pressurization to be done very slowly by operating the PRV manually and when the pressure is equal then put it in Auto.