The pressure regulator is a generally open valve and is installed at the starting point of a system or before pressure sensitive equipment to regulate or reduce undesirable higher upstream pressure.
The backpressure regulator is a generally closed valve installed at the end point of the piping system to provide an obstacle to flow so that it regulate upstream (back) pressure. The backpressure regulator is used to provide pressure in order to draw fluid off the system. When fluid pressure exceeds the set point, the valve opens more to relieve the excess pressure.
Use of Backpressure Regulator:
Where a barrier benefits each and everything before to the valve, at the end point of the return line and before to the tank, a backpressure regulator must be used to give obstacle so that the equipment prior will have adequate pressure. When pressure is very high, the backpressure regulator opens and dumps into the cistern.
Use of Pressure Regulator:
Where a barrier will benefit everything after the valve, a pressure regulator must be used so that all the equipment after regulator will not have extreme pressure. Pressure regulator will use at the starting point of a process because pressure regulator will secure safe downstream pressure for the whole system.