The leakage test is a central topic in the hydraulics of demolition and cutting technology. It safeguards performance, occupational safety, and environmental protection—especially for hydraulically operated concrete demolition shear, rock and concrete splitters, and the hydraulic power pack systems of Darda GmbH. Detecting leaks early prevents pressure losses, unnecessary downtime, and consequential damage to components that are challenged in demanding applications such as concrete demolition and special demolition, gutting works and cutting, rock excavation and tunnel construction, natural stone extraction, or special operations.
Definition: What is meant by leakage test
A leakage test is the systematic verification of whether a component, an assembly, or an entire hydraulic system exhibits the required tightness. The aim is to determine the leak rate or to ascertain whether, within defined limits, there is no impermissible pressure drop, medium egress, or air ingress. In practice, this includes visual inspections, pressure and functional tests, measurements of pressure drop, and—depending on the task—acoustic, sensory, or fluid-analytical methods. In hydraulic demolition tools, cylinder and valve seals, hose connections, couplings, and housing seals are the focus.
Core aspects of leakage testing in hydraulic demolition systems
The leakage test links technical tightness requirements with real jobsite loads. While concrete demolition shear cycle under load, rock and concrete splitters operate with high peak pressures in the cylinder. Both tool groups place special demands on sealing systems: they must reliably hold pressure, allow movement with low friction, and withstand temperature fluctuations, contamination ingress, and vibration.
Tasks and objectives of the leakage test
A reliable leakage test prevents failures and increases the operational safety of hydraulic tools in the field.
- Safety: Minimizes risks due to sudden pressure drop, medium egress, and resulting malfunctions.
- Performance: Ensures that tools such as concrete demolition shear actually achieve their nominal cutting pressure and that splitters reach their splitting force.
- Cost-effectiveness: Reduces downtime, consequential damage (e.g., to slide bearings, piston rods), and fluid consumption.
- Environmental protection: Prevents hydraulic oil from entering soil and water, supporting clean jobsite processes.
- Quality assurance: Demonstrates functionality after service, assembly, or transport—relevant throughout the entire life cycle.
Seal types and weak points in hydraulics
Hydraulic demolition tools combine static and dynamic sealing points. Understanding different seal types facilitates selection of the test method and interpretation of results.
Typical sealing locations
- Piston and rod seals in the cylinder (e.g., on concrete demolition shear, rock splitter cylinders)
- O-rings and flat gaskets on housings, valve blocks, and fittings
- Quick couplers, hose and pipe connections between the hydraulic power units and the tool
- Shaft seals on pumps and motors in the power pack
Common damage patterns
- Abrasion and scoring on the piston rod due to dirt particles
- Extrusion of sealing lips at pressure spikes or incorrect clearances
- Thermal aging, hardening, or swelling due to unsuitable media
- Assembly errors, misalignment, impermissible surface roughness, and notch effects
Test methods in practice
The choice of test method depends on the component, pressure level, temperature, and the required evidentiary goal (pass/fail or limit value measurement). In the context of demolition tools, the following methods are common:
Visual and functional inspection
- Clean the sealing area; check for dampness, oil film, traces of leakage oil
- Operate the tool over the full stroke; observe response time and return
- Check couplings, hose protection, and chafe points
Pressure hold test (static)
- Build up the target operating pressure via the hydraulic power pack
- Isolate or hold the pressure stage; measure the pressure drop over a defined time
- Evaluate leak rate with respect to volume, time, and temperature
Leakage measurement at the return line (dynamic)
- Measure leakage oil at the return line or at dedicated leakage lines of the cylinder
- Evaluate under real load, e.g., while holding a concrete demolition shear in the closed position
Supporting methods
- Marker or UV leak detection media for hard-to-access areas
- Acoustic/control checks on valve seats and check valves
- Temperature monitoring to correctly assess viscosity-related effects
Test sequence: step by step
- Preparation: secure the tool, depressurize, visual inspection of lines and couplings.
- Cleaning: clean sealing areas to reveal micro-leakage.
- Pressure build-up: slow ramp-up via the hydraulic power pack, avoid pressure surges.
- Stabilization: wait for temperature and viscosity equalization.
- Measurement: record pressure drop, leakage quantity, or flow rate; if necessary at multiple load points.
- Evaluation: compare with permissible limits; plausibility check (temperature, environment).
- Documentation: test report with date, parameters, result, and measures.
Limits and assessment
Permissible leak rates depend on the component, system pressure, and duty profile. As a rule, small function-related leakage quantities in hydraulic systems may be acceptable without impairing safety or function. Decisive are the technical specifications and the recognized rules of technology. Recommendations should always be considered in relation to temperature, oil viscosity, and measurement duration.
Typical application scenarios and their test requirements
- Concrete demolition and special demolition: high dust and impact loads—focus on piston rod and valve seals.
- Gutting works and cutting: alternating load cycles indoors—precise pressure hold tests for accurate work.
- Rock excavation and tunnel construction: long lines, low temperatures—test for cold-start tightness and coupling sealing.
- Natural stone extraction: continuous load and humidity—corrosion protection and sealing face care are crucial.
- Special operations: specifics such as media compatibility, spark environments—strict control for absolutely clean tightness.
Relevance for selected tools and assemblies
Concrete demolition shear
On concrete demolition shear, dynamic rod seals and valve seats are critical. Stable pressure holding with the shear closed indicates sealing quality of cylinder, valve block, and couplings. Leakage measurement at the return line and targeted pressure hold tests are suitable procedures.
Rock and concrete splitters and rock splitting cylinders
Splitter cylinders operate with high pressure spikes. The leakage test focuses on piston/rod seals, port seals, and the transition to high-pressure hoses. A defined static pressure test with temperature equalization is appropriate, supplemented by visual inspection after load changes.
Hydraulic power pack
On the power pack, pump shaft sealing, pressure relief valve, check valves, and connections are the focus. Pressure hold and functional testing with measurement logging ensure the basis for tight tools.
Combination shears, multi cutters, and steel shears
Here, alternating loads and high cutting forces act. Tightness is reflected in reproducible cycle times and stable closing pressure. Tests under load and after temperature changes reveal weak points.
Tank cutters
When working on vessels, clean tightness of hydraulic components is essential to prevent uncontrolled medium egress. The test covers all connections, especially couplings and hose transitions, as well as careful visual inspection before and after use.
Test equipment and auxiliaries
- Precisely calibrated pressure gauges and pressure sensors
- Flow meters and leakage oil measurement devices
- Test blocks, pressure hold valves, measurement adapters
- Cleaning agents, marker or UV media for leak detection
- Personal protective equipment (eye, hand, and skin protection)
Documentation and quality management
Structured logging supports maintenance, verification, and trend analyses. The following should be recorded: test date, ambient temperature, oil type/viscosity, test pressure, measurement duration, measurement results, and measures (e.g., seal replacement, retightening of fittings). Recurring test intervals are based on the duty profile and the technical specifications of Darda GmbH.
Environmental protection and occupational safety
Hydraulic oil must be handled properly. Drips must be eliminated immediately, escaping media absorbed, and disposed of correctly. Tests are performed depressurized, secured, and with appropriate tools. Notes on legal requirements are general in nature and do not replace case-by-case evaluation; the applicable regulations and company instructions remain authoritative.
Common causes of leakage and prevention
- Overpressure events and pressure surges
- Contamination, particles, moisture
- Temperature fluctuations and unsuitable media
- Assembly errors, insufficient tightening torques
- Aging of hoses and sealing materials
- Mechanical damage to lines and sealing faces
Preventive measures
- Ensure cleanliness and filtration of hydraulic oil
- Set pressure limitation correctly; avoid pressure shocks
- Regular inspection and timely seal replacement
- Protective hoses and chafe protection at highly stressed areas
- Run-in and temperature management after service work
Maintenance intervals and condition monitoring
Depending on the load, fixed intervals can be combined with condition-based measures. Trend measurements (pressure drop over time, leakage quantities) and hydraulic oil analysis help detect gradual seal deterioration early. This increases the availability of concrete demolition shear and Splitters in demanding day-to-day operations.
Standards and recognized rules of technology
For planning, operation, and testing of hydraulic systems, the recognized rules of technology are decisive. These include principles of hydraulic safety, requirements for lines, seals, and valves, as well as specifications for documentation. Specific applications should follow the technical documentation of Darda GmbH.
Practical examples
- Gutting works in existing buildings: precise holding of the concrete demolition shear without re-pumping indicates tight valve seats and rod seal.
- Tunnel construction in winter: a cold-start test followed by a pressure hold phase reliably reveals temperature-dependent leakage.
- Natural stone extraction: regular inspection of couplings reduces leak risks on long hose runs between power pack and tool.
Measured variables and influencing factors
Key influencing variables are test pressure, oil viscosity and temperature, measurement duration, the volume of the test environment, and the condition of check valves and pressure relief valves. Proper evaluation always considers the interplay of these factors to avoid misdiagnosis.