Hydraulics

Hydraulics is a drive technology in which pressurised fluids are used to transmit mechanical force and motion. Within Industrial Automation, hydraulics is applied where high forces, accurate positioning or robust linear movement are required. Typical applications include presses, lifting systems, injection moulding machines, locks, mobile equipment, steel processing and heavy process installations.

Hydraulic systems combine mechanics, fluid dynamics, control engineering and industrial control. In modern OT environments, hydraulic installations are often integrated with PLC, SCADA, sensors, actuators and industrial networks for monitoring, control and Predictive Maintenance.

Hydraulics is distinguished from electrical and pneumatic drives by its very high power density. Relatively compact components can deliver substantial forces.

⚙️ How hydraulics works

A hydraulic system operates on the basis of Pascal’s law: pressure exerted on a confined fluid is transmitted uniformly in all directions.

A standard hydraulic system consists of:

• Hydraulic pump
• Reservoir or oil tank
• Pipes and hoses
• Control and directional valves
• Hydraulic cylinders or motors
• Filters
• Pressure relief devices
• Sensors
• Control via PLC or DCS

The pump converts mechanical energy into hydraulic energy by pressurising oil. Via valves, the flow is directed to actuators such as cylinders or hydraulic motors.

Pressure determines the available force:

F = P × A

Where:

• F = force
• P = pressure
• A = piston area

This is why hydraulic systems can deliver very high forces using relatively small cylinders.

🏭 Typical industrial applications

Hydraulics is applied in environments where high loads and robust drive technology are required.

Process industry

• Control valves
• Large shut-off valves
• Safety mechanisms
• Press installations

Production environments

• Injection moulding machines
• Metal presses
• CNC clamping
• Forming machines

Energy and infrastructure

• Lock gates
• Hydropower plants
• Turbine control
• Emergency shut-off valves

Mobile installations

• Excavators
• Aerial work platforms
• Cranes
• Agricultural machinery

Within Industrial Automation, hydraulics is often combined with Motion Control, PID control and SCADA monitoring.

🔩 Key components

Hydraulic pump

The pump generates volumetric flow. Commonly used pump types are:

Variable-displacement pumps can dynamically adjust their output for energy savings.

Hydraulic cylinder

A cylinder converts hydraulic pressure into linear motion.

Types:

• Single-acting
• Double-acting
• Telescopic cylinder
• Differential cylinder

Position feedback is often provided by:

• Encoders
• Linear measurement systems
• Pressure sensors
• Limit switches

Valves

Valves determine direction, pressure and flow.

Key variants:

Servo-hydraulics is used in highly dynamic applications such as test rigs and precision presses.

Hydraulic oil

Hydraulic fluid serves several functions:

• Energy transmission
• Lubrication
• Cooling
• Corrosion protection
• Contaminant removal

Oil contamination is a major cause of failures. Filters, Condition Monitoring and maintenance are therefore critical.

🔄 Closed-loop control

Many modern hydraulic systems operate as closed-loop control systems.

A typical control loop comprises:

1. Sensor measures position or pressure
2. PLC or Motion Controller computes correction
3. Control valve adjusts flow
4. Cylinder moves
5. Feedback is measured again

This forms a Feedback Loop.

Applications:

• Cylinder synchronisation
• Precision positioning
• Pressure control
• Speed control

Advanced systems use:

• PID
• Servo control
• Adaptive control
• Model Predictive Control

🧠 Integration with industrial automation

Hydraulic installations are increasingly integrated into OT networks.

Frequently used integrations:

Real-time data includes, among other things:

• Pressure values
• Oil temperature
• Flow
• Vibration
• Positions
• Energy consumption

This creates opportunities for:

• Predictive Maintenance
• Condition Monitoring
• Alarm detection
• Trend analysis
• Asset optimisation

🌐 Network and OT aspects

Modern hydraulic power units increasingly contain Embedded controllers and network connections.

Frequently used protocols:

• ProfiNET
• Ethernet IP
• CAN
• Modbus TCP
• OPC UA

Hydraulic subsystems often function as distributed IO or intelligent motion nodes within larger OT architectures.

In critical environments such as power plants or water management, failure of hydraulic systems can have a direct operational impact.

For this reason, the following are often applied:

• Redundancy
• Fail-safe design
• Pressure accumulators
• Emergency pumps
• Mechanical bypasses

🔐 Cybersecurity of hydraulic systems

Traditionally, hydraulic systems were largely mechanical, but modern installations increasingly contain digital components.

Risks arise from:

• Remote Access
• Network connections
• Insecure Firmware
• Poorly segmented OT networks
• Insufficient Authentication

Possible attack scenarios:

Mitigating Measures:

• Network Segmentation
• Firewall
• Zero Trust
• IEC 62443
• Hardening
• Monitoring

Within OT environments, cybersecurity must account for the physical consequences of manipulation.

⚠️ Safety and risks

Hydraulics often operates at pressures between 100 and 700 bar. Leaks or defects can therefore cause serious risks.

Key risks:

• Hose burst
• Injection injury
• Overheating
• Fire hazard
• Unintended motion
• Pressure explosions

Safety measures are therefore essential:

• Pressure relief valves
• Mechanical interlocking
• Safety Relay
• Safety PLC
• Pressure monitoring
• Emergency stop circuits

Relevant standards:

⚡ Hydraulics versus Pneumatics and electrical

Hydraulics remains dominant in applications that require extremely high forces.

📈 Monitoring and predictive maintenance

Hydraulic systems generate a great deal of useful operational data.

Key measurements:

• Oil contamination
• Temperature
• Pressure fluctuations
• Vibration
• Pump efficiency
• Leakage flow

Using Industrial AI, Machine Learning and Anomaly Detection, deviations can be detected at an early stage.

Typical predictable defects:

• Pump wear
• Cavitation
• Internal leakage
• Clogged filters
• Defective valves

Integration with CMMS systems enables condition-based maintenance.

🔋 Energy efficiency

Traditional hydraulic systems have relatively high energy losses.

Major sources of loss:

• Heat generation
• Internal leakage
• Continuously running pumps
• Pressure losses

Modern optimisations:

• Variable-frequency-driven pumps
• Variable output
• Servo-hydraulics
• Smart pressure control
• Energy recovery

Particularly in large industrial installations, optimisation can deliver significant energy savings.

🏗️ Hydraulics in IT/OT convergence

Within IT OT Convergence, hydraulics is shifting from purely mechanical technology to data-driven Assets within integrated OT platforms.

This creates new opportunities:

• Remote diagnostics
• Cloud analytics
• Digital twins
• Predictive analytics
• Central Monitoring

But also new challenges:

• Cybersecurity
• Lifecycle Management
• Network load
• Legacy integration
• Vendor lock-in

Hydraulic systems thereby become part of broader Cyber-Physical Systems within modern industrial infrastructures.