A pressure hose is the flexible, high-load connection between the hydraulic power pack and the tool. In Darda GmbH applications—from concrete demolition with concrete demolition shears to hydraulic rock and concrete splitters and on to special demolition and rock excavation—the hose line transmits energy, protects the medium from environmental influences, and ensures safe, low-loss force transmission. Its selection, installation, and maintenance directly influence performance, precision, and occupational safety.
Definition: What is meant by a pressure hose
A pressure hose (also hydraulic hose or hose line) is a flexible line for transmitting pressurized fluids, typically hydraulic oil. It consists of an inner tube that is compatible with the medium, one or more pressure-bearing reinforcements (textile braid, steel wire braid, or wire spiral), and an abrasion- and weather-resistant outer cover. Key parameters include operating pressure, burst pressure, temperature range, bend radius, impulse resistance, and media compatibility. In practice, pressure hoses are crimped with fittings, connected via quick coupling, and routed as paired lines to create supply and return between the power unit and the tool.
Design and functional principle of a hydraulic pressure hose
The design follows a functional layer principle: The inner tube made of oil-resistant elastomer or thermoplastic carries the medium and minimizes internal friction as well as permeation. The reinforcement absorbs the internal pressure—single or double wire braid for medium pressures, multi-layer wire spiral for high flow rates and peak pressures. The cover provides mechanical protection (abrasion, chafing) and resistance against environmental influences (ozone, UV, moisture, chemicals). Depending on the application environment, additional protective layers or textile abrasion guards are used.
Hydraulic pressure causes radial and longitudinal expansion in the hose. This volumetric expansion influences the response of tools such as concrete demolition shears and hydraulic wedge splitters: lower expansion yields a more direct reaction and more precise metering of closing and splitting forces. Impulse resistance is essential, since pressure spikes can occur during start-up, load changes, or when reinforcement tears away. Hose types with verified impulse cycles are selected to match the real load spectra in demolition operations.
Sizing: inner diameter, pressure rating, and routing length
Sizing is based on flow rate, maximum operating pressure, impulse loading, temperature, and the required bend radius along the routing. For mobile use in concrete demolition and tunnel construction the rule is: as short as possible, as large as necessary. Too small an inner diameter raises flow velocity and pressure losses, heats the medium, and impairs the power delivered at the tool. Oversized nominal diameters increase cost, hinder handling, and can make the response feel spongy.
Flow rate and pressure loss
Flow velocity and pressure loss are directly tied to inner diameter and hose length. For compact tools such as concrete demolition shears, a moderately low flow velocity is desirable to limit heat generation and energy losses. Long supply lines between the Darda hydraulic power units and the tool require adapted nominal diameters and high-quality quick couplings with low flow resistance.
Minimum bend radius and freedom of movement
The manufacturer-specified minimum bend radius must not be undershot under pressure. In practical applications—such as guiding a concrete demolition shear in confined demolition areas or positioning hydraulic wedge splitters in boreholes—safety margins should be planned. Anti-kink guards, abrasion protection, and swivel connections increase service life and prevent torsion.
Pressure rating and impulse resistance
The pressure rating (e.g., 250–420 bar in typical mobile high-pressure ranges) must be chosen with an adequate safety margin over system pressure. Especially with hydraulic wedge splitters, which can generate short-term high peak pressures, impulse resistance is crucial. Multi-layer wire-spiral hoses offer advantages here, provided handling weight and flexibility remain practical.
Applications: From concrete demolition to rock
In Darda GmbH application areas—concrete demolition and special demolition, building gutting and cutting, rock excavation and tunnel construction, natural stone extraction as well as special operations—pressure hoses must be robust, flexible, and safe. On construction sites, abrasive concrete dust meets sharp-edged reinforcement; in tunnel construction, moisture, mud, impacts, and tight routing dominate; in natural stone extraction, long line runs, temperature swings, and UV exposure are added factors.
The hose cover should therefore be abrasion-resistant and ozone-resistant. Under thermal stress (cutting operations, sparks), flame-retardant protective sleeves help. In damp environments, thermoplastic hoses can offer benefits, provided the pressure rating and impulse resistance are adequate. In special operations—such as near-underwater work or contaminated areas—media compatibility and safe cleaning are the focus.
Interfaces to concrete demolition shears and hydraulic wedge splitters
Between the pressure hose and the tool, the quality of fittings and couplings determines tightness, flow, and response time. For concrete demolition shears, quick couplings with high flow and drip-free performance are advantageous to enable clean, efficient coupling and decoupling at changing work locations. Anti-twist solutions and swivel fittings prevent torsional damage when aligning the shear.
Hydraulic wedge splitters place high demands on peak-pressure resistance and return-flow capability. A well-matched hose pair—supply with adequate pressure rating, return with sufficient cross-section—supports quick cycle times when setting and releasing the splitting wedge. Protective spirals, textile sleeves, and deflector brackets in contact zones with rock or reinforcement reduce chafing and crushing.
Media and temperature resistance
Mineral oil-based hydraulic oils are standard. Environmentally compatible, rapidly biodegradable pressure fluids are increasingly used. The pressure hose must be compatible with the medium; this concerns swelling, permeation, and temperature stability. At low temperatures the cover needs cold flexibility, at high ambient temperatures heat and ozone resistance. Water-containing media (e.g., water-glycol) place special demands on materials and on corrosion protection for fittings.
Observe thermal limits
The specified temperature range applies to both medium and ambient. Near cutting tools, steel shear, or cutting torch, temporarily elevated temperatures can occur; heat-protection sleeves and sufficient clearance help here. If the hose is overheated regularly, the cover ages prematurely; microcracks and exfiltration may result.
Safety, inspection, and maintenance of hose assemblies
Compliance with recognized technical rules, professional assembly, and regular visual and functional checks are essential. Hose assemblies are wear parts and should be inspected and replaced preventively at sensible intervals—especially under harsh construction-site conditions. Inspection criteria include leaks, blistering, cracks, crushed zones, chafed areas, corrosion on fittings, and damaged coupling profiles.
Installation principles
- Avoid kinks, observe bend radius, prevent torsion.
- Provide sufficient hose slack for lifting and slewing movements.
- Route lines so they are protected from drop edges, hot surfaces, and pinch points.
- Tighten fittings with correct torques; choose the sealing system to suit the medium.
- Ensure cleanliness: keep caps on until installation, flush before commissioning.
Operation and replacement
In operation, pressure spikes, unusual noises, changed response behavior, and elevated oil temperature are warning signs. If age, number of cycles, or damage no longer meet requirements, replacement is indicated. Test and replacement intervals are based on usage intensity and the respective technical specifications; binding intervals are usually defined by the operator.
Accessories: couplings, protective sleeves, and hose management
Components around the pressure hose increase safety, ergonomics, and service life. Quick couplings with high flow minimize pressure losses. Dust caps protect open systems during tool changes. Protective spirals, textile sleeves, and heat shields increase resistance to abrasion, edge contact, and sparks. Color coding and labeling make it easier to distinguish supply and return, especially when changing tools such as multi cutters, combination shears, or concrete demolition shears.
Routing and storage
Hose pairs are routed together wherever possible and secured against twisting. For longer distances between the Darda GmbH hydraulic power pack and the tool, hose reels or take-up systems support neat laying. For storage: cool, dry, dark; no point loads, no sharp bend radii. Before recommissioning, perform a visual check and a brief functional test.
Practical tips for installation and operation
- Select the appropriate nominal size: consider flow rate and maximum line length.
- Dimension the pressure rating with a safety margin over system pressure; consider impulse loading.
- Provide protection at contact points: abrasion guards, edge protection, heat protection.
- Use quick couplings with low pressure loss; keep coupling profiles consistent.
- Prevent torsion: swivel connections, correct hose length, relaxed routing.
- Perform regular visual inspections and preventive replacement of aged lines.
- Ensure cleanliness: caps, clean working environment, flushing before initial operation.
Recognizing and avoiding failure modes
- Kink points: indicate excessive bending or incorrect routing; consequences are weakening up to hose rupture.
- Chafed cover: contact with edges or debris; remedy with protective sleeve, correct routing, deflectors.
- Blistering: inner tube separation due to overheating or media incompatibility; take the hose out of service immediately.
- Cracked cover: aging, ozone exposure, or heat; check storage conditions and temperature.
- Leaks at fittings: faulty crimping, wrong seal, vibration; check installation and re-assemble if necessary.
- Performance drop at the tool: undersized nominal bore, contaminated coupling, high pressure loss; check cross-section and couplings.
Application context: pressure hose in the Darda GmbH system
The pressure hose is part of an overall system of hydraulic power pack, couplings, lines, and tool. With concrete demolition shears it influences closing speed and the consistency of cutting force; with hydraulic wedge splitters it supports short cycle times and controlled pressure build-up and release. In tunnel construction and building gutting, the flexible line makes it possible to position the power unit away from the work area, reduce emissions, and improve operator ergonomics.
System matching
High-performance yet compact hose assemblies with suitable impulse resistance, clean internal finish, and matching couplings contribute to reproducible results and make tool changes between concrete demolition shears, multi cutters, steel shear, or concrete demolition shears in changing demolition sections easier.
Legally compliant practice and responsibilities
For selection, installation, inspection, and operation of hose assemblies, the applicable technical rules, manufacturer’s instructions, and in-house work procedures should be observed. Test cycles, documentation, and the handling of spare parts lie within the operator’s responsibility. Regular instruction of users—especially on safely depressurizing hydraulic systems and recognizing damage patterns—significantly contributes to accident prevention.