This is Ahmed from Alexandria, Egypt. I am studying at faculty of engineering, Alexandria university, Egypt . Actually ,This is my last year and i am working for my graduation project . In my graduation project i met a difficult situation for me . i have a system consist of 4 different tanks and every tank is connected with a pump . The 4 pumps are supposed to deliver flowrate to delivery tank throw a header . it's supposed to get flowrates from lines by ratio as i can get a final product consists of ratio of different mixed oils . My problem is how to draw the pump curve in parallel for this combined system as there are 4 pumps (2cenrtifugal pumps & 2 positive displacement pumps ) .