Test Bench

A hydraulic test bench is a specialized testing facility that tests, measures, and documents hydraulic components and complete hydraulic circuits under defined, reproducible operating conditions. It evaluates the function, performance, efficiency, tightness, and safety of the components and is primarily used in the B2B environment for quality assurance, development, repair, and acceptance of hydraulic systems.

What is a hydraulic test bench?

A hydraulic test bench replicates one or more hydraulic circuits and subjects the test object to controlled pressure, volume flow, speed, temperature, and defined load profiles. It combines:

• Drive unit (electric motor or combustion engine)
• Hydraulic unit with variable pressure and volume flow stages
• Open, closed, or combined test circuits
• Measurement and control technology for recording all relevant variables
• Safety and protection systems
• Data acquisition and documentation

In industrial environments, test benches are primarily used to check whether a hydraulic component or unit is operating in accordance with specifications, whether repairs have been carried out properly, and whether a system can be safely put into operation.

Areas of application for test benches in hydraulics

A modern hydraulic test bench is aimed at manufacturers, operators, and service providers of machines and systems in the B2B sector:

Development and testing:

• Validation of new pumps, motors, valves, cylinders
• Determination of characteristic curves, efficiency levels, and temperature behavior
• Design of systems for mobile hydraulics, hydraulic presses, machine tools, steelworks, plastics machines

Quality assurance in series production:

• 100% testing of safety-related components
• Spot checks according to factory standards and customer requirements
• End-of-line test benches with automated test cycles

Repair and service:

• Functional verification after repair
• Comparison of actual values with manufacturer specifications
• Documented approval for operators and purchasers

Acceptance and system tests:

• Testing of complete units and control blocks prior to installation in the system
• Testing of open, closed, and hybrid drive concepts

HK Hydraulik uses highly flexible test benches that cover a wide range of components and meet test requirements from various industries.

Standards, guidelines, and legal requirements

In Europe, a hydraulic test bench is considered a machine in terms of product safety law. Manufacturers, operators, and integrators must comply with the following regulations:

• Machinery Directive 2006/42/EC and successor Machinery Regulation (EU) 2023/1230:
• Safety of control systems
• Emergency stop devices
• Separating protective devices (protective covers, enclosures)
• Safe operation during automatic cycles

Pressure Equipment Directive 2014/68/EU:

• Design and marking of pressure-bearing components
• Materials, testing, conformity assessment
• Low Voltage and EMC Directives:
• Electrical equipment, control cabinet construction, interference emissions

Functional safety:

• Design of safety functions according to EN ISO 13849 or IEC 62061
• Assessment of performance level/SIL for critical functions such as pressure limitation, speed limitation, interlocks
• BetrSichV, occupational safety and environmental protection:
• Safe operating stations
• Handling of hydraulic fluids, leak detection
• Noise protection, hot surfaces

A professionally designed test bench consistently incorporates these requirements so that operators can argue their case clearly in the event of an audit (e. g. , automotive, rail, aviation).

Design and operating principle of a hydraulic test bench

A professional hydraulic test bench for hydraulic components consists of clearly structured functional groups.

Hydraulic power supply

• Drive: Electric motor with frequency converter or mechanically coupled drive
• Test unit: Constant or variable displacement pump, often axial piston
• Pressure ranges: classic industry: up to approx. 350 bar; high-pressure applications: up to 420 or 500 bar
• Volume flow ranges: from a few l/min for proportional valves to several hundred l/min for large pumps or mobile hydraulic components
• Temperature control: cooling and preheating of the fluid for testing at defined temperatures

Test circuits: open, closed, combined

A flexible test bench replicates different hydraulic circuits:

Open circuits:

• Testing of constant and variable displacement pumps
• Load via throttle or load valves
• Determination of delivery volume, pressure build-up, efficiency

Closed circuits:

• • Testing of hydrostatics, travel drives, slewing drives
  • Combination of pump and motor in circulation
  • Measurement of torque, slip, volume losses

• Semi-closed/combined circuits:
• Integration of flushing and auxiliary circuits
• Testing of complex control blocks or system solutions

A PLC or industrial PC control system defines test sequences, runs ramps, cycles, and load changes, and logs all measured values.

Typical design parameters of a hydraulic test bench

When designing a test bench for hydraulics in a B2B environment, engineering is guided by the target components.

Typical parameters:

Maximum pressure_pmax:

• 250 to 420 bar for standard industrial hydraulics
• Up to 500 bar for high-pressure applications

Volume flow_Qmax:

• 50 to 150 l/min for medium-sized components
• 300 to 1, 000 l/min and more for large pumps and motors

Drive power P:

• From 30 kW in training or laboratory operation
• To well over 250 kW in service and OEM test benches

Fluid management:

• Fine filtration according to manufacturer specifications
• Online monitoring of temperature, viscosity, contamination

Exemplary relationships, greatly simplified:

Phyd = (p × Q) / 600
ηges =Phyd / Pantrieb
M = (Phyd × 9550) / n

A well-planned system uses these variables to plan for reserves, ensure thermal stability, and realistically map different load cases.

Test procedures for hydraulic components

A hydraulic test bench supports specific test procedures for each component group. Decision-makers in design, service, and purchasing need clear, reproducible criteria.

1. Test bench for hydraulic pumps

Characteristic curve recording:

• Volume flow over pressure at constant speed
• Determination of internal leakage

Efficiency analysis:

• Comparison of mechanical, volumetric, and overall efficiency with reference values

Noise and vibration behavior:

• Evaluation for noise- or vibration-sensitive applications

Endurance or burn-in tests:

• Verification of stability under real load conditions

2. Test bench for hydraulic motors

• Measurement of torque and speed
• Efficiency over load and speed
• Behavior during direction of rotation change
• Starting torque and starting behavior at different pressures

3. Test bench for hydraulic cylinders

• Leak test: Rod side and piston side at different pressure levels
• Positioning accuracy: For cylinders with position measuring system
• Frictional forces: Detection of seal or guide damage
• End position damping: Evaluation of braking distance and pressure peaks

4. Test bench for hydraulic valves and control blocks

• Switching function: Switching times, hysteresis, reproducibility
• Flow characteristics: Pressure loss and volume flow at defined positions
• Leakage: Internal leakage on seat and slide valves
• Proportional and servo valves: Control via electronics, map testing, linearity

Measurement and data technology in the hydraulic test bench

A modern test bench for hydraulics not only provides a “pass” result, but also reliable data.

Important measured variables:

• Pressure: at inlets and outlets, in control lines
• Volume flow: via measuring turbines or flow meters
• Speed and torque: at pump and motor shafts
• Temperature: of fluid, housings, return flow
• Travel/positions: on cylinders and actuators
• Electrical signals: on valves with integrated electronics

Requirements for measurement technology:

• Sufficient accuracy (often ≤ 0. 5% of the measuring range, better for reference positions)
• Dynamic recording for load changes and pulsations
• Synchronization of all channels
• Tamper-proof storage and test reports (for OEM, rail, aviation, automotive)

Safety concept and operator requirements

A hydraulic test bench operates with high energies. Operators in service, production, and laboratories pay attention to a robust safety design.

Key elements:

• Enclosures and protective covers: Protection against bursting pipes, burst tests, flying parts
• Pressure limitation: Mechanical and control-related limitation
• Interlocks: Opening the protective enclosure stops the test sequence and relieves the system
• Emergency stop: At all relevant operating stations
• Leakage management: Collection trays, sensors, clean fluid handling
• Clearly defined operating modes: Setup, manual test, automatic run with different release conditions

HK Hydraulik and other specialists design test benches so that service personnel can quickly change over, but all relevant protective functions remain active.

The specific design depends on the target components and industry requirements.

Current market requirements in B2B mechanical engineering

Companies that develop, maintain, or use hydraulic components expect the following from a test bench:

• High flexibility: Quick adaptation to different pumps, motors, cylinders, and valves
• Realistic load profiles: Load collectives from mobile hydraulics, press operation, cycle machines
• Digital integration: Connection to ERP, QA systems, remote access, test reports as PDF/data records
• Energy efficiency: Feedback of test power into the grid, variable speed drives
• Transparent test reports: For acceptance, complaint management, and documentation requirements

A professionally designed hydraulic test bench thus directly strengthens the technical decision-making confidence of:

• Design engineers who want to know the limits
• Service technicians who want to verify repair quality
• Purchasers who want to verify performance data
• Plant operators who want to ensure availability and safety

This means that the test bench is not just a “nice to have” in the hydraulic environment, but rather the central tool for reliable, traceable hydraulic performance.