i have gone through alll the articles i got here regarding this….
i think, probably i havent got the right or cant fix the answers in my questions……… please explain me in detail… i m a fresh piping engineer… in a EPC.

In every pump suction there is a reducer that i hav seen. if the outlet of the tank nozzle is 50nb and the pump suction nozzle is 40nb, we are using reducer in suction. why cant we use a pump nozzle of 50nb..
plz explain me in detail….