Switch hydraulics describes the entirety of hydraulic control and switching functions used to deliberately initiate, regulate, and safely terminate movements, forces, and sequences in tool operations. In practice, this concerns the precise actuation of concrete demolition shears, rock and concrete splitters, steel shears, tank cutters, combination shears, multi cutters, and stone splitting cylinders that are powered by a hydraulic power pack. Especially in concrete demolition, special demolition, building gutting, rock breakout, tunnel construction, natural stone extraction, and special operations, a robust and intelligently designed switch hydraulics determines speed, control, efficiency, and safety.
Definition: What is meant by switch hydraulics
Switch hydraulics refers to the functional structure of valves, control blocks, lines, couplings, and sensors that direct the oil flow in a hydraulic system so that actuators (usually cylinders or motors) perform defined movements. It includes the switching of flow paths, the limiting of pressure, the throttling of flow, the holding of loads, and the sequencing of work steps. In connection with hydraulic power packs from Darda GmbH, switch hydraulics feeds the connected tools and coordinates their work strokes—from closing a concrete demolition shear to spreading with a stone and concrete splitter.
Operating principle and key components of switch hydraulics
Switch hydraulics connects energy source, control, and consumers into a logically operating unit. Core components are:
- Directional control valves (e.g., 3/2-, 4/3-, or seat valves) for diverting oil flow for extend and retract strokes or opening and closing.
- Pressure valves (safety and relief valves) to protect against overload and to limit cutting or splitting force.
- Flow control and throttle valves for speed control, for example to ensure uniform closing of concrete demolition shears.
- Check and load-holding valves for safe positioning and to prevent uncontrolled movements.
- Sequence or priority valves for defined processes, for example clamping before cutting.
- Control blocks as compact units in which valves are functionally combined.
- Quick couplers and hose lines for modular connection between hydraulic power pack and tool.
- Sensors (pressure gauge, temperature, and, if applicable, switching position) for monitoring and diagnostics.
Switch hydraulics in interaction with concrete demolition shears and stone and concrete splitting devices
The requirements differ depending on the tool. Two typical examples:
Concrete demolition shears: controlled opening and closing
Concrete demolition shears operate with double-acting cylinders and require a directional valve with two active switching positions plus a pressure-neutral center position (depending on the system). Sensitive flow throttling is important so the arms close uniformly. Load-holding or check valves prevent yielding under load. A cross-over relief valve can protect the structure against pressure spikes that occur when notching reinforcing steel.
- Open: The directional valve switches to retract; oil flow is controlled out of the cylinder.
- Position: The center position allows holding without creeping (given the appropriate valve characteristic).
- Close/Cut: The directional valve switches to extend; pressure is limited via the safety valve.
Stone and concrete splitting devices: safe force peaks during the stroke
Splitting devices often generate characteristic pressure peaks during wedging. Switch hydraulics must reliably control pressure build-up and relief. A sequence control can separate wedge advance (positioning) from the actual spreading stroke (splitting). Overpressure protection and anti-cavitation safeguards secure the return stroke. The hydraulic power pack from Darda GmbH provides the required flow rate and pressure; the valve logic in the tool or on the control block executes the work cycle.
Circuit types and architectures
The choice of circuit type influences usability, efficiency, and tool compatibility.
- Open center: Oil circulates at low pressure in neutral; good for simple, mobile power packs and one tool at a time.
- Closed center: Neutral position blocks consumer ports; suitable for parallel consumer control.
- Single-acting: Extend hydraulically, return by spring/weight—typical for certain spreading or wedge functions.
- Double-acting: Extend and retract hydraulically—standard for concrete demolition shears and steel shears.
- Series circuit: Functions switch one after the other, controlled by sequence valves.
- Parallel circuit: Simultaneous supply of multiple functions, requiring careful flow division.
Pressure, flow, and control: sizing for force and speed
Switch hydraulics converts the performance data of the hydraulic power pack into tool motion. Key aspects are:
- Pressure determines the maximum possible force at the tool.
- Flow sets the speed; excessive flow rates make fine control more difficult.
- Valve characteristics (proportionality, hysteresis) affect metering when positioning.
- Thermal effects and viscosity: Oil temperature changes control behavior; stable conditions improve repeatability.
Quick couplers, residual pressure, and safe switching operations
Quick couplers enable rapid tool changes. Reliable switching requires proper management of residual pressure. Relief valves, pressureless returns, and clearly defined neutral positions prevent shocks in the system and make coupling easier. Load-holding valves and check valves secure the position of a concrete demolition shear even if pressure drops.
Hydraulic power packs as the energy source of switch hydraulics
Hydraulic power units from Darda provide the required pressure and flow rate. In switch hydraulics, the power pack is controlled via start/stop and, if applicable, speed, while the valves on the control block handle fine distribution. For mobile deployments (building gutting, tunnel construction, special demolition), a compact, robust design with good heat dissipation and appropriate filtration is essential.
Commissioning, adjustment, and maintenance
A structured approach increases reliability and service life:
- Preparation: Visual inspection of hoses, sealing faces, couplings; check oil level and viscosity.
- Bleeding: Cycle consumers at low load until bubble-free operation is achieved.
- Adjustment: Set pressure at the safety valves to match the tool; throttle flow for uniform speed.
- Functional test: Open/close or spread under test load; evaluate temperature and noise.
- Maintenance: Replace filters per interval, clean couplings, fix leaks immediately.
Troubleshooting: typical symptoms and causes
- Slow stroke: Clogged filter, flow too low, throttle closed too far.
- Creeping in neutral: Leaks, contaminated valve seat, incorrect center position.
- Pressure spikes/shocks: Missing pressure relief, switching too abruptly, no anti-cavitation safeguard.
- Uneven opening of the concrete demolition shear: Asymmetric throttling, air in the system, defective load-holding valves.
- Difficult coupling: Residual pressure in lines, contaminated couplings, missing pressureless return.
Application areas and typical switching logics
Concrete demolition and special demolition
Sequence: position, clamp, cut/crush, relieve. A clear order prevents material jamming and reduces load spikes in the existing structure.
Building gutting and cutting
Sensitive control with moderate flow to work close to load-bearing structures. Pressure limiting protects against unintended force transmission.
Rock breakout and tunnel construction
With splitting devices, robust overpressure and load-holding functions are important. Temperature and contamination management ensure consistent performance in dusty environments.
Natural stone extraction
Repeatable splitting cycles with reproducible pressure levels. Simple, intuitive valve operation accelerates the takt.
Special operations
Flexible control blocks with switchable scenarios (e.g., soft start or fast cycle) increase adaptability to changing tasks.
Selection criteria for valves and control blocks
- Compatibility with tools such as concrete demolition shears, steel shears, or stone splitting cylinders (single-/double-acting, required switching positions).
- Performance data: maximum pressure, flow rate, switching capacity.
- Operating concept: hand-, foot-, or electrohydraulic actuation, ergonomic layout.
- Serviceability: accessibility of filters, gauges, and test ports.
- Robustness against dirt, moisture, and vibration in construction site use.
Oil quality, filtration, and temperature management
Clean hydraulic fluid with suitable viscosity is a basic prerequisite for precise switching. Staged filtration (suction and return filters) and temperature control keep valve clearances freely moving and minimize wear. In cold conditions, short warm-up cycles with reduced flow help; in heat, consistent pressureless circulation in neutral prevents unnecessary heating.
Control strategies: manual, electrohydraulic, proportional
Depending on the application range, manual lever valves, foot-actuated directional valves, or electrohydraulically actuated valves are used. Proportional valves enable sensitive speed control—helpful for millimeter-precise placement of a concrete demolition shear or controlled widening during the splitting process. Clear labeling and tactilely distinct controls increase process safety.
Integration in mobile and stationary applications
In mobile scenarios (e.g., building gutting), compact, contamination-resistant valve technology with well-protected couplings is advantageous. Stationary applications (e.g., natural stone extraction with recurring splitting operations) benefit from hard-piped control blocks with reproducible settings. In both cases, test ports simplify diagnostics during operation.
Best practices for clear switching sequences
- Define a clear neutral position to prevent unintended movements.
- Use sequence logic for critical operations (clamp before cutting/splitting).
- Place pressure limitation close to the consumer to minimize line effects.
- Symmetric throttling for uniform jaw movement of shears.
- Perform regular functional tests under realistic loads.