Solid roller failed again

[madmaxx]

I wish I could stick a picture in here. Take a pump feeding a one inch diameter line and off that line is four quarter inch diameter lines, spaced two inches apart.

At the end of each of the four quarter inch lines is a cover which does not allow the total volume of oil to pass, which the pump is capable of moving.

With a positive displacement pump the pump moves its entire capacity (volume) with every rotation, it does not have the ability to slip (cavitation) like a centrifugal pump. The clearances in a PDP are exponentially tighter than a centrifulgal. So if you block to much flow either your pump relief pops, your oil pump body cracks, or you dont have enough power to turn the pump.

Look at a garden hose dumping into a bucket driven by a centrifugal pump. You open the nozzle flow increases because you are reducing resistance in the circuit and the pump impeller does not recirculating as much since you get to it highest efficiency point.

You now use a positive displacement pump on your garden hose with the hose in a bucket, you open your nozzle and flowrate does not increase, you reduced pressure in the system but your flowrate stayed the same because the gears in the gear pump cannot pump anymore.