Pumps in Parallel - Flow Rate Added
When two or more pumps are arranged in parallel their resulting performance curve is obtained by adding the pumps flowrates at the same head as indicated in the figure below.

Centrifugal pumps in parallel are used to overcome larger volume flows than one pump can handle alone.

for two identical pumps in parallel and the head kept constant - the flow rate doubles compared to a single pump.

In practice, if one of the pumps in parallel stops, the operation point moves along the system resistance curve to point of intersection with running pump curve - the head and flow rate are decreased.

The key to running dissimilar pumps in parallel is to run the total system flow rate in a range that allows both pumps to run within a reasonable region on their pump curves to avoid issues due to excessive loads on the impeller, bearings, or seals. The pump manufacturer should be consulted to determine if parallel pump operation with dissimilar pumps is advisable for any particular application. When the pump curves are relatively flat, it becomes even more important to avoid excessive resistance. A small change in system resistance can take this pump from operating cleanly and efficiently to not operating at all.

Buy AMJ a coffee to say thanks
*******************************
https://paypal.me/AMJengineering