The oil pipeline is the central connecting element in the hydraulic system and ensures that pressure energy is reliably transmitted from the Darda hydraulic power units to tools and cylinders. In the context of Darda GmbH, it plays a key role, for example in operating concrete demolition shears or stone and concrete splitters in applications such as concrete demolition, strip-out, rock breakout, tunnel construction, and natural stone extraction. A properly designed and routed oil pipeline increases performance, improves controllability, and reduces downtime in demanding operations.
Definition: What is meant by oil pipeline
An oil pipeline is a hydraulic line that transports hydraulic oil between pump, valves, actuators, and tools. It can be implemented as a flexible hose line or as a rigid pipe run and includes the associated fittings, threaded connections, and couplings. Depending on the task, a distinction is made between pressure lines, return lines, suction lines, and leak-oil lines. Essential properties of an oil pipeline include pressure resistance, flow capacity, resistance to media and temperatures, and a safe, leak-tight connection technology.
Structure and components of an oil pipeline
An oil pipeline essentially consists of the line body (hydraulic hose or pipe), the end fittings (e.g., cutting-ring or O-ring fittings), suitable couplings for the tool-side connection, and, where applicable, protective components such as abrasion protection, burst protection, or thermal protection. Flexible hose lines use multilayer fabric or steel wire braid to absorb pressure; pipework often consists of precision-drawn steel tubes. Sealing typically takes place via conical sealing faces, O-rings, or flange systems. A professional combination of these components is crucial so that tools such as concrete demolition shears and stone and concrete splitters can operate in the high-pressure range in a controlled and safe manner.
Functions in the system: From the pump to the tool
In Darda GmbH hydraulic systems, oil pipelines connect the hydraulic power pack with the tools and return points. They perform different functions:
- Pressure line: transports energy to the tool, e.g., to cylinders of a concrete demolition shear or to stone-splitting cylinders.
- Return line: routes the oil back at low pressure, minimizes pressure losses, and causes less heating.
- Suction line: supplies the pump with oil; low flow velocity is important to avoid cavitation.
- Leak-oil line: discharges clearance flows from motors/control units in a controlled manner and relieves seals.
Hose line or pipe run: selection according to operating conditions
In concrete demolition, rock breakout, and tunnel construction, flexible hose lines dominate due to mobility, vibration decoupling, and rapid installation. Pipe runs are advantageous when high stability, low expansion, and good heat dissipation are required, for example between the power pack and the machine frame. Both principles are often combined: pipe runs for fixed routing, hose lines for movable transitions to tools such as concrete demolition shears, multi cutters, or steel shears.
Sizing: pressure, flow rate, diameter
The sizing of the oil pipeline is determined by system pressure, flow rate, and permissible flow velocity. For good controllability and low heating, flow velocity in pressure lines should remain moderate, return lines should be sized somewhat larger, and suction lines particularly generously. In practice, low velocities are recommended in suction lines (to avoid cavitation) and limited velocities in the pressure and return branches (to reduce pressure loss and noise). The internal diameter should be selected so that pressure spikes are damped and energy losses minimized. In applications with impulsive loading, such as closing concrete demolition shears or during the splitting stroke of a stone and concrete splitter, the expansion behavior of the line (volumetric compliance) is also relevant for response behavior.
Influence of length, bend radii, and couplings
Long routing paths, tight bend radii, and many couplings increase pressure loss. A streamlined routing with the minimum bend radius according to the manufacturer’s specifications protects the hose from internal damage and extends service life. Quick couplings should be chosen so that they transmit the flow without noticeable throttling.
Media compatibility, temperature, and sealing materials
Oil pipelines must match the hydraulic oil used, such as mineral-oil-based fluids or biobased, rapidly biodegradable oils (e.g., HEES). Sealing materials such as NBR, HNBR, or FKM are selected according to temperature window and media compatibility. In cold environments (tunnels, high altitudes, winter operations), the cold bendability of the hose is crucial to ensure lines remain elastic and tight at low temperatures. At high continuous and peak temperatures, improved thermal resistance helps protect the line.
Cleanliness, filtration, and commissioning
Particle contamination is a main cause of premature wear of valves and seals. Oil pipelines should be kept clean before installation, flushed if necessary, and then correctly vented. An appropriate filtration rating in the system supports the target cleanliness. During tool changes (e.g., concrete demolition shear to steel shear), clean coupling faces are essential to avoid dirt ingress. A systematic approach to commissioning, including a leak test and visual inspection, reduces start-up problems and minimizes the risk of failures.
Typical measures to ensure cleanliness
- Use protective plugs and caps during transport and before installation.
- Flush new lines and fill in a controlled manner with filtered oil.
- Carefully vent after installation or tool change.
Routing and fastening: practice in demolition and tunnel construction
In harsh operations, vibration, abrasion, impacts, and weather act on oil pipelines. Professional routing avoids chafing points, torsion, and pressure spikes. Lines must be routed so that tool movements (e.g., large opening paths of a concrete demolition shear) are accommodated without kinking. Clamps and protective sleeves prevent point loads at edges. In tunnel construction and special operations with tight radii or sharp rock edges, additional abrasion protection has proven effective.
Torsion-free installation
Hose lines must not be installed twisted. Markings along the hose length help detect twisting. A slight inherent rotation of the tool when gripping or splitting must not force the line into torsion; for this, appropriate length reserves and coupling positions must be provided.
Fittings, threaded connections, and couplings
End fittings connect the line securely to valves, power packs, and tools. Sealing systems with O-ring or metallic sealing edge must match the pressure level and the medium. Quick couplings facilitate tool changes between concrete demolition shear, combination shear, or multi cutter. Attention must be paid to low pressure losses, secure locking, and mix-up protection of the connections. Regular visual inspection of the sealing faces increases operational safety.
Inspection, maintenance, and replacement
Oil pipelines are wear parts. Visible cracks, blistering, oil leakage at crimp ferrules, damaged outer covers, or deformed fittings are warning signs. Scheduled inspection at fixed intervals as well as documentation of service time facilitates preventive maintenance. After exceptional events (mechanical impact, strong overstretching), an unscheduled inspection should be performed. When replacing, observe compatible line types, correct lengths, and the ratings for pressure and temperature.
Typical failure patterns and causes
- Abrasion on outer covers due to rubbing on edges or concrete.
- Kink points due to undershooting the minimum bend radius.
- “Sweating” at crimp ferrules as an indication of seal wear.
- Couplings loosening due to insufficient locking under vibration.
- Excessive heating due to too small a nominal size or constrictions.
Safety: minimizing risks
Hydraulic oil under high pressure can be dangerous. Injection injuries caused by leak jets must be avoided; leaks must never be searched for by hand. Establish zero-pressure conditions before working on the oil pipeline, wear suitable protective equipment, and do not route lines near hot surfaces or sharp-edged components. Test and maintenance work is carried out under clean conditions; spilled oil must be collected and disposed of in an environmentally sound manner.
Normative guidance and marking
Hydraulic lines and hoses are usually designed according to recognized rules of technology and are marked with information on nominal size, pressure rating, manufacturer code, and production date. For safe application, conformity with the system requirements is decisive: permissible operating pressure, temperature range, media compatibility, and bend radii. Clear marking facilitates assignment in the field and supports preventive maintenance.
Selection criteria for oil pipelines in products from Darda GmbH
For tools such as concrete demolition shears or stone and concrete splitters, robust high-pressure lines with suitable nominal size and a resistant outer cover should be selected. Decisive criteria are pressure range, flow rate, movement profile of the line, environmental conditions (dust, moisture, temperature), coupling system, and protection needs (abrasion or burst protection). A well-matched interplay with the hydraulic power pack from Darda GmbH and the valves used ensures precise response and high repeatability.
Practical tips for selection
- For impulsive load changes, choose a line with good fatigue behavior.
- Couplings with a high flow cross-section avoid unnecessary throttling.
- With frequent tool changes, pay attention to dirt-tolerant coupling geometries and protective caps.
- Provide additional protective jackets in dirty environments.
Areas of application and special requirements
In the application areas of Darda GmbH, the requirements for oil pipelines vary:
- Concrete demolition and special deconstruction: high impact loads and abrasion, therefore reinforced outer covers and secure fastening.
- Strip-out and cutting: flexible line bundles for tight spaces, low leakage, and clean couplings.
- Rock breakout and tunnel construction: increased requirements for cold-bend behavior, abrasion and cut protection; reliable function in dust and moisture.
- Natural stone extraction: long routing distances between power pack and tool, therefore optimized nominal sizes against pressure loss.
- Special operations: depending on boundary conditions, special media (e.g., rapidly biodegradable oils), additional protection systems, and redundant fastening.
Hydraulic fine-tuning for concrete demolition shears
The precise opening and closing of concrete demolition shears strongly depends on the oil pipeline design. Too small a nominal size slows the tool and generates heat; too large a nominal size can make the response feel spongy. A suitable combination of line length, coupling cross-section, and damping behavior enables controlled, sensitive work when gripping, cracking, and separating concrete components.
Oil pipelines on stone and concrete splitters
Peak loads are transmitted during the splitting process. Lines with an appropriate pressure rating and good fatigue strength are important to safely transmit force to the splitting cylinder. Tidy, torsion-free routing helps to handle repeated splitting cycles without premature material fatigue. The return should be sufficiently sized so that the cylinder depressurizes quickly and is ready for the next cycle.
Documentation and traceability
Simple but consistent documentation with installation date, line type, pressure rating, length, and place of use simplifies later assessments. Markings on the lines, labels on couplings, and an individual line concept for tool sets (e.g., for concrete demolition shears, combination shears, tank cutters) create clarity and prevent mix-ups.
Environmental and sustainability aspects
Tight systems and intact oil pipelines protect the environment and the workplace. Containment trays, absorbent mats, and proper disposal of oil-containing operating supplies are part of responsible handling. The use of suitable media can meet additional environmental requirements depending on the place of use.
Interaction with hydraulic power packs from Darda GmbH
Oil pipelines form the interface between hydraulic power pack and tool. A needs-based design of the line with respect to the delivery volume and pressure behavior of the power pack supports performance in the field. Coordinated couplings and clear assignment of supply and return keep operation simple and prevent misconnections.