Valve housings are central components in fluid power systems. They guide and protect the spool or valve body, direct flows, and safeguard the pressure balance. In demolition and splitting technology as used by Darda GmbH, valve housings connect hydraulic power packs with tools such as concrete demolition shears or rock and concrete splitters. They help ensure that forces are precisely metered, movements safely controlled, and media losses minimized—even under harsh environmental conditions on construction sites, in tunnels, or in natural stone extraction.
Definition: What is meant by valve housing
A valve housing is the housing of a slide or spool valve (directional or flow control valve). It forms the pressure-bearing structure, contains the control bores and channels, accommodates seals, and ensures the precise guidance of the spool (spool, slider body). In hydraulic applications, the valve housing controls the flow of pressurized fluid between pump, working cylinders, and tank. In practice, the term is also used for the housings of gate valves in pipelines; in mobile hydraulics—such as with concrete demolition shears, rock splitters, or combi shears—the focus is usually the housing of a directional control valve or a valve manifold.
Design and operating principle
The valve housing contains precisely machined bores and channels. The spool moves axially within them. Depending on its position, the spool geometry connects or isolates individual ports (P, T, A, B). In this way, the direction of motion, speed, and holding function of hydraulic cylinders are defined.
Key components
- Housing body with pressure channels, connection threads, or flange faces
- Spool with control edges for switching
- Sealing elements (O-rings, backup rings, wipers) to minimize leakage
- Actuation (manual, hydraulic, electric) for spool adjustment
- Return elements (springs), optional for a center position
Flow and sealing concept
Flow occurs across control edges with defined overlap. Surface quality and geometric accuracy in the housing determine leakage and friction behavior. A suitable sealing concept reduces internal leakage and protects against external emissions without impairing the spool’s ease of movement.
Valve housings in demolition and splitting technology
Hydraulic tools from Darda GmbH operate with high pressures and varying loads. Valve housings in the valves of the tools or the hydraulic power packs must therefore be robust, precise, and service-friendly.
Concrete demolition shears
In concrete demolition shears, valve housings control the pressurization and relief of the hydraulic fluid for opening and closing the jaws. The housings must withstand pressure spikes from cutting reinforcement, impact loads when biting in, and ingress of debris. Low internal leakage helps keep hold functions stable, for example when securing a concrete element.
Rock and concrete splitters
In splitting, reproducible pressure profiles are crucial. The valve housing of a directional or pressure control valve supports precisely metered pressurization of the splitting cylinders. Sensitive switching behavior promotes controlled crack growth in the rock and reduces undesirable impact effects.
Combi shears, multi cutters, steel shears, and tank cutters
These tools require reliable switching under load, often in alternating operation. Valve housings with optimized flow cross-sections limit pressure losses and heating. In tank-cutting applications, the media compatibility of the housing material and the seals can play a particular role.
Design features and materials
Valve housings are pressure-bearing and functionally precise. The choice of material and machining is based on pressure level, flow rate, and environment.
- Materials: Quenched and tempered steel (e.g., 42CrMo4) for high strength; spheroidal cast-iron housings for damping; aluminum for low weight (at moderate pressures); stainless steel for media or corrosion resistance.
- Wall thicknesses and ribs: to absorb internal pressure and bending loads from hose forces.
- Surfaces: finely ground guides for the spool; suitable coatings for corrosion protection and wear reduction.
- Seal grooves: sized according to manufacturer specifications, with backup rings for extrusion resistance at high pressure.
- Connections: threads, screw-in cartridges (cartridge), or flanges per common interfaces, matched to the hydraulic power packs and tools of Darda GmbH.
Selection criteria and design
The correct design of a valve housing supports efficiency, service life, and safety.
- Rated pressure and load spectra: take into account static and dynamic pressure spikes; plan safety margins.
- Flow rate and pressure loss: size flow channels to avoid heating and cavitation.
- Control characteristics: overlap of control edges (under-, equal-, or over-lapped) appropriate to the desired sensitivity, e.g., when positioning a concrete demolition shear.
- Media compatibility: mineral oils or rapidly biodegradable hydraulic fluids; check seal compatibility.
- Temperature range: consider viscosity effects and thermal expansion.
- Actuation: manual (lever), hydraulic, pneumatic, or electric (solenoid valve) depending on the application environment.
- Contamination tolerance: robust clearances and good filtration; important in concrete demolition and natural stone extraction.
Manufacturing, machining, and testing
The functional quality of a valve housing depends on machining accuracy.
- Machining: drilling, reaming, honing for guides and control bores; coaxiality and straightness are critical.
- Cleaning: low-particle assembly through thorough deburring and flushing of channels.
- Pressure and leak testing: verification of strength and leakage limits; if necessary, functional testing of switching positions.
- Documentation: traceability of material, batches, and test parameters supports maintenance of Darda GmbH’s tools.
Installation in hydraulic power packs and tools
The installation location influences function and maintainability. In hydraulic power units, valve housings are often integrated as a valve manifold; in tools they are located close to the actuator for short line runs and fast response.
Assembly notes
- Clean sealing faces, correct tightening torque, suitable bolt quality.
- Observe installation orientation to avoid air pockets and facilitate venting.
- Vibration protection and mechanical decoupling against impact loads in concrete demolition.
- Filtration: fine filters in pressure and return lines, wipers in exposed locations.
Maintenance, cleaning, and servicing
Regular care preserves switching precision and extends service life in demanding applications such as rock demolition and tunnel construction or strip-out.
- Inspection: visual check for leakage, corrosion, cracks; functional test of switching positions.
- Oil quality: monitor particle count and water content; replace oil and filters at set intervals.
- Cleaning: gentle external cleaning; no aggressive chemicals that could attack seals.
- Seal service: replace O-rings and backup rings when pressure-holding capability declines.
- Documentation: record service loads and operating hours to plan maintenance.
Typical failure patterns and causes
- Sluggish or stiff switching: contamination, burr formation, incorrect viscosity, or worn guides.
- Internal leakage: worn spool edges/guides, unsuitable seals, thermal distortion.
- External leakage: pinched O-rings, insufficient tightening torque, damaged sealing faces.
- Cavitation/noise: excessive flow velocities, unfavorable cross-sections, air in the system.
- Corrosion: insufficient protection in wet and dusty environments, incompatible media.
Safety aspects
Valve housings are safety-relevant because malfunctions can affect tool movements. In general: observe the manufacturer’s specifications, allow installation only by trained personnel, and avoid changes to control systems. Depressurize and secure against restart before working on the system. Document tests after maintenance.
Environmental and sustainability aspects
A tight, precisely manufactured valve housing reduces oil losses and thus environmental impacts on construction sites. Media-compatible seals support the use of rapidly biodegradable hydraulic fluids. Durable materials, replaceable sealing elements, and repair-friendly designs improve the carbon footprint over the life cycle.
Trends and further developments
Modern valve housings increasingly integrate sensors for condition monitoring (e.g., position, temperature, pressure). Improved surfaces and coatings reduce friction and wear. Flow-optimized geometries lower pressure losses, which in Darda GmbH’s mobile hydraulic systems supports energy efficiency and keeps oil temperature within the permissible range—important for continuous operations in natural stone extraction or in specialized deconstruction.