Hydraulic Pumps: Types, Efficiency Calculations, Cavitation & Energy Saving Systems
Hydraulic Pumps: Types, Efficiency Calculations, Cavitation & Energy Saving Systems
Hydraulic Pumps: Types, Efficiency Calculations, Cavitation and Energy-Efficient Control Systems
Hydraulic pumps are the core of every industrial hydraulic system. They convert mechanical energy into hydraulic energy by moving fluid and creating flow, while system pressure is generated by the load. Selecting the correct pump type and control method directly affects energy consumption, system efficiency, operating cost and component lifetime.
This guide explains hydraulic pump types, efficiency formulas, cavitation risks and modern energy-saving pump control technologies used in European industry.
What Is a Hydraulic Pump?
A hydraulic pump produces flow by displacing fluid from the inlet (suction) side to the outlet (pressure) side. The volume of fluid delivered per revolution is called the geometric displacement.
Theoretical flow:
Qₜ = Vg × n
Where:
Qₜ → theoretical flow (l/min)
Vg → displacement (cm³/rev)
n → rotational speed (rpm)
Because of internal leakage, the actual flow is always lower than the theoretical value.
Hydraulic Pump Efficiency
Volumetric Efficiency
Volumetric efficiency represents internal leakage losses.
ηv = Qactual / Qtheoretical
As system pressure increases, internal leakage increases and volumetric efficiency decreases.
Overall Efficiency
Overall efficiency includes both volumetric and mechanical losses:
ηo = ηv × ηm
Mechanical efficiency represents friction losses in bearings, gears and pistons.
Hydraulic Pump Power Calculation
P (kW) = (p × Q) / (600 × ηo)
Example:
150 bar × 26.7 l/min with 85% efficiency → 7.85 kW required motor power
Accurate power calculation is essential for correct motor sizing and energy optimisation.
Types of Hydraulic Pumps Used in Industry
External Gear Pumps
Fixed displacement
Simple and cost-effective
Medium pressure capability
Relatively higher noise level
Typical applications: mobile hydraulics, lubrication systems, auxiliary circuits.
Internal Gear Pumps
Internal gear pumps provide:
Very low noise levels
High volumetric efficiency
High contamination tolerance
Stable performance at low speeds
Modern four-quadrant pump-motor units can operate as both pump and motor, enabling energy recovery during load lowering.
Applications: industrial power units, presses, elevators, energy-efficient systems.
Vane Pumps
Low noise
Smooth flow
Available in fixed and variable displacement
Easy maintenance
Applications: machine tools, plastic injection machines, medium-pressure industrial systems.
Screw Pumps
Very low pulsation
Quiet operation
High flow at low pressure
Applications: cooling circuits, filtration loops, oil transfer systems.
Piston Pumps (Axial and Radial)
High pressure capability (>350 bar)
Variable displacement options
High power density
Precise control
Applications: steel mills, heavy presses, mining equipment, offshore and wind energy systems.
Gear vs Vane vs Piston Pumps: Key Selection Criteria
When selecting a hydraulic pump, engineers must evaluate:
Maximum operating pressure
Required flow rate
Duty cycle (continuous, intermittent, peak)
Fluid viscosity
Noise limits
Energy efficiency targets
Total cost of ownership
High pressure and precise control → Piston pump
Low noise and high efficiency → Internal gear pump
Economical solution → External gear pump
Cavitation in Hydraulic Pumps
Cavitation is one of the most common causes of premature pump failure.
It occurs when dissolved air in the oil vaporises under vacuum conditions at the suction side and collapses under pressure.
Main Causes
Clogged suction filter
Long or undersized suction line
Cold oil with high viscosity
Blocked tank breather
Excessive suction resistance
Consequences
Metal surface erosion
Increased noise and vibration
Reduced efficiency
Severe pump damage
Proper suction line design and correct oil viscosity are critical for cavitation prevention.
Energy-Efficient Hydraulic Pump Control Systems
Traditional valve-controlled systems waste energy through throttling losses and heat generation.
Modern pump-controlled systems significantly improve efficiency.
Key Advantages
✔ Up to 60–70% energy savings
✔ Up to 90% reduction in oil volume
✔ Smaller tank and cooling requirements
✔ Lower noise levels
✔ Compact system design
These systems are widely used in:
Scissor lifts
Hydraulic elevators
Wind turbine pitch control
Plastic injection machines
Flight simulators
Servo press systems
Variable Speed Drives and Servo Hydraulic Pumps
In variable speed pump drives:
Flow is controlled by motor speed
Pressure is controlled by motor torque
Using feedback from:
Pressure sensors
Position transducers
Temperature sensors
the system achieves high dynamic response within milliseconds.
This technology delivers:
Significant energy savings
High positioning accuracy
Reduced heat generation
Lower lifecycle cost
Low-Noise and High-Efficiency Solutions for EU Industry
European manufacturers increasingly demand:
Energy-efficient hydraulic systems
Low noise emission
Compact power units
CE and ISO compliant designs
Internal gear pumps and servo-driven piston pumps are becoming the preferred solutions for modern industrial applications.
Conclusion
Hydraulic pump selection is not only a technical decision but also an energy and cost optimisation strategy.
Understanding pump types, efficiency calculations, cavitation risks and modern control technologies enables engineers to:
Reduce power consumption
Extend system lifetime
Improve machine performance
Lower maintenance costs
Energy-efficient pump-controlled systems represent the future of industrial hydraulics in Europe.