Hydraulic Power Unit | HPU Design, Manufacturing & Commissioning
Hydraulic Power Unit | HPU Design, Manufacturing & Commissioning
Hydraulic Power Unit: Design, Components, Manufacturing and Commissioning Guide
A Hydraulic Power Unit (HPU) is the central power source of many industrial hydraulic systems. It generates, controls and supplies hydraulic energy required to operate hydraulic cylinders, hydraulic motors and other hydraulic actuators.
Hydraulic power units are widely used across Europe in industrial machinery, manufacturing plants, steel and metal processing, mining equipment, construction machinery, energy systems, presses, injection moulding machines and customised automation applications.
A professionally engineered hydraulic power unit is much more than a hydraulic pump and electric motor mounted on a tank. The complete system must be designed according to operating pressure, flow rate, duty cycle, oil temperature, filtration requirements, control philosophy and the specific requirements of the machine.
As an experienced hydraulic power unit manufacturer, Hidroman designs and manufactures customised hydraulic power units and hydraulic subassemblies for demanding industrial applications.
What Is a Hydraulic Power Unit?
A Hydraulic Power Unit (HPU) is a hydraulic drive system used to generate and supply hydraulic power to a machine or hydraulic circuit.
The main purpose of an HPU is to convert mechanical energy supplied by an electric motor into hydraulic energy and provide the required pressure and flow to the hydraulic system.
Depending on the application, a hydraulic power unit can include:
- Electric motor
- Hydraulic pump
- Hydraulic oil tank
- Pressure relief and control valves
- Hydraulic manifold
- Suction and return line filtration
- Hydraulic oil cooler
- Pressure and temperature sensors
- Level monitoring
- Accumulator system
- Hydraulic hoses and pipework
- Electrical control cabinet
- PLC and monitoring system
The exact configuration depends on the machine requirements and operating conditions.
Hydraulic power units and hydraulic subassemblies are generally designed as customer-specific systems rather than simple standard products. The technical documentation may include hydraulic schematics, technical specifications, component lists and assembly drawings.
Hydraulic Power Unit Design
The performance and reliability of a hydraulic system depend heavily on the correct design of the hydraulic power unit.
A professional HPU design should consider the complete hydraulic circuit rather than individual components.
Key design parameters include:
- Required operating pressure
- Maximum system pressure
- Required flow rate
- Electric motor power
- Pump displacement
- Hydraulic oil type and viscosity
- Oil tank capacity
- Filtration level
- Oil cooling requirements
- Accumulator requirements
- Duty cycle
- Ambient temperature
- Hydraulic actuator requirements
- Control and automation requirements
- Maintenance accessibility
The hydraulic power unit should be designed according to the actual working conditions of the machine. Pressure, temperature, environmental conditions, operating time and cycle frequency should all be considered when defining the service and maintenance requirements.
Main Components of a Hydraulic Power Unit
- Electric Motor
The electric motor provides the mechanical power required to drive the hydraulic pump.
Motor selection should be based on the required hydraulic power, operating pressure, flow rate, pump efficiency and duty cycle.
An incorrectly sized electric motor can result in:
- Excessive energy consumption
- Overheating
- Insufficient hydraulic flow
- Poor system performance
- Reduced pump efficiency
For this reason, the electric motor and hydraulic pump should always be selected as part of the overall hydraulic power unit design.
- Hydraulic Pump
The hydraulic pump converts mechanical energy from the electric motor into hydraulic energy.
Depending on the application, different pump technologies may be used. Pump selection should consider:
- Required flow rate
- Continuous operating pressure
- Maximum pressure
- Oil viscosity
- Operating temperature
- Duty cycle
- Fixed or variable flow requirements
Correct pump installation and commissioning are also essential. Unusual pump noise may indicate conditions such as cavitation, air entering through the suction line or excessive air in the hydraulic oil.
- Hydraulic Oil Tank
The hydraulic reservoir stores the hydraulic fluid and contributes to thermal management and air separation within the system.
A properly designed hydraulic tank should consider:
- Oil volume
- Working temperature
- Air breather
- Suction connections
- Return connections
- Drainage
- Filtration
- Oil level monitoring
- Maintenance access
Minimum and maximum oil levels should be monitored during operation. After transportation or long-term storage, the tank should also be checked for water contamination.
Hydraulic Filtration and Oil Cleanliness
Hydraulic oil cleanliness is one of the most important factors affecting the reliability and service life of hydraulic components.
Contaminated hydraulic oil can cause:
- Pump wear
- Valve malfunction
- Servo valve problems
- Proportional valve performance issues
- Seal damage
- Increased component wear
- Unexpected hydraulic system failures
Hydraulic contamination can be introduced during manufacturing, assembly, pipe installation, commissioning, maintenance or oil filling.
Importantly, new hydraulic oil is not necessarily clean enough for every hydraulic application. The technical documentation recommends filling the hydraulic system through a dedicated filtration unit or fine filtration station when the required cleanliness level needs to be ensured.
For high-performance hydraulic systems, hydraulic oil filtration should therefore be considered an integral part of the system design.
Hydraulic Flushing and System Cleanliness
Hydraulic flushing is a critical commissioning process for newly installed or modified hydraulic systems.
During manufacturing and installation, hydraulic pipes and components can contain contaminants such as:
- Welding residues
- Metal particles
- Dust
- Manufacturing debris
- Assembly contamination
- Foreign particles
If these contaminants enter sensitive hydraulic components, they can cause premature failure.
Hydraulic system flushing is performed to achieve the required fluid cleanliness level and reduce contamination-related failures.
The technical documentation specifies ISO 4406 cleanliness class 20/18/15 as an example for general industrial hydraulic systems. Systems containing servo valves or high-precision control valves may require higher cleanliness levels, such as ISO 4406 19/16/13. The actual target cleanliness level must be determined according to the requirements of the installed components.
How Is Hydraulic Flushing Performed?
Hydraulic flushing should be planned according to the hydraulic circuit and the cleanliness target.
Depending on the application, preparation may include:
- Replacement or flushing filter elements
- Temporary flushing hoses
- Additional pipework
- Flushing plates
- Bypass connections
- Alternative directional valves
- Suitable flushing fluid
Complex hydraulic systems require detailed flushing planning and controlled implementation.
During flushing, the hydraulic power unit should preferably be brought to its operating temperature and operated at low pressure. Oil samples should be taken periodically and analysed to verify the cleanliness level.
This approach makes hydraulic flushing based on oil analysis, rather than simply relying on flushing time.
Hydraulic Subassemblies
In addition to complete hydraulic power units, specialised hydraulic subassemblies can be designed and manufactured for integration into industrial machinery.
Examples include:
- Valve manifolds
- Valve stations
- Hydraulic accumulator stations
- Motor-pump units
- Filtration stations
- Cooling stations
- Filtration and cooling circulation units
These hydraulic subassemblies can be integrated into larger hydraulic systems according to the machine's functional requirements.
A modular approach can simplify hydraulic system installation, maintenance and servicing.
Hydraulic Power Unit Installation
Correct installation is essential for reliable HPU operation.
Hydraulic pipework and hoses must be installed without unnecessary mechanical stress. Incorrectly installed hydraulic lines can transfer additional forces and vibration to hydraulic components.
Particular attention should be paid to:
- Hose bending radius
- Hose twisting
- Mechanical tension
- Abrasion
- Vibration
- Pipe support
- Connection alignment
- Accessibility for maintenance
Hydraulic hoses should not be installed under excessive tension or torsion. Proper routing and support are essential for long-term hose reliability.
Electrical installation must also comply with the applicable electrical engineering requirements. Hydraulic power units must be properly grounded and potential equalisation must be implemented where required.
Hydraulic Power Unit Commissioning
Hydraulic power unit commissioning is one of the most critical stages of a hydraulic system project.
Before commissioning, the following checks should be completed:
- Check hydraulic connections.
- Check the hydraulic oil level.
- Verify suction and return connections.
- Check valves and pressure settings.
- Verify the electrical connections.
- Check the electric motor rotation direction.
- Ensure the hydraulic pump is correctly filled where required.
- Remove air from the hydraulic system.
- Perform hydraulic flushing where required.
- Start the system at low pressure.
- Check for abnormal noise and leakage.
- Increase operating pressure gradually.
- Monitor oil temperature and system performance.
After long-term storage, additional checks should include oil level, accumulator pre-charge pressure and leakage from hydraulic components and pipework. The hydraulic system should also be carefully vented before normal operation.
The hydraulic power unit should not be operated as an independent machine if it is designed to be integrated into another machine. The complete machine and its associated safety requirements must also be considered during commissioning.
Hydraulic Power Unit Maintenance
A professional maintenance programme helps maintain hydraulic system performance and extend component service life.
The maintenance interval should be determined according to:
- Operating pressure
- Oil temperature
- Working environment
- Operating hours
- Duty cycle
- Number of shifts
- Component requirements
Important inspection points include:
- Hydraulic oil level
- Hydraulic oil cleanliness
- Filter condition
- Oil temperature
- Hydraulic leaks
- Hose condition
- Pipe connections
- Pressure gauges
- Pressure valves
- Electrical connections
- Accumulator pre-charge
- Cooling system
Regular hydraulic oil analysis can also provide valuable information about contamination and system condition.
Hydraulic System Safety
Hydraulic systems can operate at extremely high pressures. Improper intervention can result in serious injury or equipment damage.
A high-pressure hydraulic oil leak must never be checked with hands or exposed body parts. High-pressure fluid injection injuries can occur even when the leak appears small.
Installation, commissioning, maintenance and dismantling should be carried out by personnel with appropriate mechanical, electrical and hydraulic knowledge.
Safety procedures should always be based on the actual machine design, applicable regulations and the manufacturer's technical documentation.
Hydraulic Power Unit Manufacturer for Industrial Applications
Choosing the right hydraulic power unit manufacturer is an important decision for industrial machinery manufacturers and system integrators.
A reliable HPU supplier should be able to support the complete engineering process, including:
- Hydraulic circuit design
- Pump selection
- Electric motor selection
- Hydraulic manifold design
- Reservoir design
- Filtration
- Oil cooling
- Accumulator systems
- Hydraulic pipework
- Hose assemblies
- Electrical control
- PLC integration
- Commissioning
- Hydraulic flushing
- Oil cleanliness management
- Maintenance and service
Hidroman develops custom hydraulic power units and hydraulic subassemblies according to specific machine and application requirements.
The engineering process can include hydraulic circuit diagrams, technical specifications, component lists and assembly drawings to support installation, commissioning and future maintenance.
Why Hydraulic Power Unit Design Matters
A properly engineered HPU provides more than hydraulic pressure and flow.
Correct hydraulic power unit design can contribute to:
- Reliable machine operation
- Longer component service life
- Improved hydraulic efficiency
- Better temperature control
- Improved oil cleanliness
- Easier maintenance
- Reduced unplanned downtime
- Safer system operation
- More predictable machine performance
For this reason, hydraulic power units should be engineered according to the complete machine requirements rather than selected solely according to pump capacity or motor power.
Conclusion
A Hydraulic Power Unit (HPU) is one of the most important components of an industrial hydraulic system. Its performance directly affects the reliability, efficiency and service life of the machine.
A successful HPU project requires much more than selecting a pump and electric motor. Hydraulic power unit design, filtration, oil cleanliness, hydraulic flushing, cooling, accumulator systems, pipework, hose assemblies, electrical control and commissioning must be considered as one integrated system.
For demanding industrial applications, customised engineering provides the flexibility required to meet specific pressure, flow, temperature, cleanliness and control requirements.
Hidroman designs and manufactures customised hydraulic power units and hydraulic subassemblies for industrial applications, supporting customers from hydraulic engineering and component selection through manufacturing, installation, flushing, commissioning and service.
Frequently Asked Questions
What is a Hydraulic Power Unit?
A Hydraulic Power Unit (HPU) is a system that generates and supplies hydraulic pressure and flow to operate hydraulic machinery and actuators.
What are the main components of an HPU?
The main components generally include an electric motor, hydraulic pump, oil reservoir, valves, filtration system, pipework and control equipment. Additional components such as coolers, accumulators and sensors can be incorporated according to the application.
Why is hydraulic oil cleanliness important?
Contaminated hydraulic oil can cause premature wear, valve malfunction, pump damage and unexpected system failures. Maintaining the correct ISO 4406 cleanliness level is particularly important for sensitive hydraulic components.
What is hydraulic flushing?
Hydraulic flushing is a controlled cleaning process used to remove contamination from hydraulic pipework and systems before or during commissioning. The process should continue until the required fluid cleanliness level is achieved.
What ISO 4406 cleanliness level is required for a hydraulic system?
The required cleanliness level depends on the hydraulic components used in the system. ISO 4406 20/18/15 is given as an example for general industrial hydraulic systems, while more sensitive systems may require levels such as 19/16/13.
Can a hydraulic power unit be customised?
Yes. Hydraulic power units can be engineered according to the required pressure, flow, motor power, oil capacity, filtration, cooling, control and machine integration requirements.
Why should I choose a specialised hydraulic power unit manufacturer?
A specialised HPU manufacturer can evaluate the complete hydraulic circuit and optimise the interaction between the pump, motor, valves, filtration, cooling, controls and actuators rather than treating each component separately.