KEVOS® MAKEOS · Hydraulics
Two-Pump Arrangement Check (Parallel or Series Operating Point, Flow Gain, Each Pump’s Duty)
If I run two identical pumps in parallel or in series on this system, what flow and head do I get compared with one pump, and where does each pump run on its curve?
Operating point of two identical centrifugal pumps in parallel (heads equal, flows add) or in series (flows equal, heads add) on a system curve: the single-pump operating point (as the pump operating point tool), the combined pump curve and its intersection with the system curve, the flow gain over one pump, the flow, head, share of best-efficiency flow and efficiency of each pump, and the total power, against the flow needed.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Arrangement | choice | Parallel pumps share the flow at the same head; series pumps pass the same flow and add their heads. |
| Each pump at rated speed | ||
| Shut-off head | m | Head of each pump at zero flow. |
| Best-efficiency flow | L/min | Flow of each pump at its best efficiency. |
| Head at best efficiency | m | Head of each pump at best efficiency. |
| Best efficiency | % | Best efficiency of each pump. |
| System | ||
| Static head | m | Static head of the system. |
| Known system flow | L/min | A known flow on the system curve. |
| System head at that flow | m | System head at that flow. |
| Liquid density | kg/m³ | Liquid density. |
| Flow needed | L/min | Flow the duty needs. |
Method and formulas
- Pump curve H = H₀ − a Q² through the best-efficiency point; system curve H = H_s + k Q² (as the pump operating point tool).
- Parallel: H₀ − a (Q ÷ 2)² = H_s + k Q². Series: 2 (H₀ − a Q²) = H_s + k Q².
- Each pump’s efficiency from the parabola through its best-efficiency point; power = ρ g Q H ÷ η per pump.
- Example: one pump gives 390.8 L/min; two give 438.18 L/min (12.122% more).
Limitations
- Identical pumps with simple parabolic curves; real curves and unequal pumps need the makers’ data.
- Parallel pumps need check valves; series pumps need the second casing rated for the higher pressure.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- See how much a second pump really adds
- Choose parallel or series for a duty
- Check each pump stays near its best efficiency
Who it is for
- Process engineers
- Building services engineers
- Maintenance engineers
What you get
- One pump alone
- Both pumps together and the gain
- Each pump’s flow, head and efficiency
Interpreting the result
- On a steep (friction-dominated) system a second pump in parallel adds little flow; series suits high static head.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3021–3026. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
