Theory bites are a collection of basic hydraulic theory and will touch upon pump design and other areas of pump industry knowledge.

Pumps can be arranged and connected in series or parallel to provide additional head or flow rate capacity.

When two (or more) pumps are arranged in series they are resulting pump performance curve is obtained by adding their heads at the same flow rate as indicated in the figure below.

Centrifugal pumps in series are used to overcome larger system head loss than one pump can handle alone:

• For two (2) identical pumps in series the head will be twice the head of a single #pump at the same flow rate – as indicated with point 2.

With a constant flow rate, the combined head moves from 1 to 2 – BUT in practice, the combined head and flow rate moves along the system curve to point 3.

• Point 3 is where the system operates with both pumps running
• Point 1 is where the system operates with one pump running

Note that for two pumps with equal performance curves running in series:

• The head for each pump equals half the head at point 3
• The flow for each pump equals the flow at point 3

Source: Engineering ToolBox

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