CORE PRINCIPLES
What to establish first
- Hydraulic power rises with flow and head.
- Input power is higher than hydraulic power because efficiency is below 100%.
- Operating point is set by the intersection of pump and system curves.
Pumps
Pump power, system curves, operating points and pump selection.
MODULE OVERVIEW
Pumps in practical engineering work.
A pump adds energy to a fluid. Selection requires matching the pump curve to the system curve while checking efficiency, cavitation margin, liquid properties, controls and motor duty.
DESIGN CONCEPTS
Terms worth checking
- Total dynamic head
- Efficiency
- NPSH
Common applications: Water transfer · Cooling water · Process circulation
KEY RELATIONSHIP
Hydraulic pump power
Pinput = ρgQH/η
- ρ — density, kg/m³
- Q — flow, m³/s
- H — total head, m
- η — pump efficiency
This is a power estimate; it does not locate a safe operating point on a pump curve.
WORKED EXAMPLE
Known values → substitution → interpretation
- Known values
- Water; Q = 15 L/s; H = 30 m; η = 70%
- Method
- Convert Q to 0.015 m³/s and divide hydraulic power by 0.70
- Interpretation
- The input-power estimate is about 6.31 kW before motor and service factors.
KEY DESIGN CHECKS
Confirm the conditions behind the number
- Define the governing load case, duty cycle and required design life before using a simplified relation.
- Use compatible units and material data for the actual condition, temperature and manufacturing state.
- Compare the result with strength, stiffness, fatigue, safety, serviceability and applicable-code requirements.
COMMON ENGINEERING MISTAKES
Keep the model within its scope
- Applying hydraulic pump power outside the assumptions shown on this page.
- Using a nominal condition while a peak, alternating, transient or environmental case governs the design.
- Treating a calculated value as a final component selection without checking interfaces, tolerances and the current governing standard.
AVAILABLE CALCULATORS
Select a calculator
RELATED RESOURCE
Open Pump Power Calculator
Estimate hydraulic and input power with stated water-density assumptions.
Open related resource →REFERENCES & LIMITATIONS
Use this content as a transparent starting point
ReferenceHydraulic Institute Standards and manufacturer pump curves; use the current manufacturer data for selection.ScopeRelationships are presented for the assumptions stated on this page and linked tool.Design reviewCheck material condition, loads, environment and the applicable current code.SafetyResults are educational/preliminary and do not certify safety or compliance.
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