What is the reason behind most positive displacement pumps have expanding cavity on the suction side and a decreasing cavity on the discharge side..? pl help clear my doubt :confused2:
Welcome! I don't know squat about pumps but in googling your question I found this:
These pumps provide a constant flow of fluid at a given pump speed, regardless of the discharge pressure required. A pressure relief needs to be used with these pumps to protect both the pump and the process in which it is installed.
In a well designed system, all types of pumps will have a larger suction pipe and smaller discharge pipe. The large suction pipe reduces the velocity and pressure (head) loss. Low pressure on the suction side will lead to cavitation (localized flashing of liquid to gas, i.e. water to steam) which will cause flow instability and potential erosion of pump internal parts. At the high pressure discharge, pressure drops are not so critical.