Pumps in Parallel or Series
Two identical pumps added in parallel double flow at fixed head; added in series double head at fixed flow (against a flat enough system curve).
Parallel flow (at same head)
1,000.0m³/h
Series head (at same flow)
100.00m
Formula, assumptions, and limits
$$Q_\text{parallel} = n \cdot Q_1, \quad H_\text{series} = n \cdot H_1$$
Works only on a flat system curve; real systems absorb most of the gain as increased flow × increased friction loss. Parallel for high-flow low-head duty (ballast, fire); series rarely used at sea - multistage pumps cover that need.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $Q_1,\ H_1$ | Single-pump duty-point values | m³/h, m | pump curve |
| $n$ | Number of pumps | - | plant design |
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