Control cabinet

A control cabinet is the functional hub for power distribution, control, monitoring, and safety of machines and tools on the construction site and in deconstruction. In applications with hydraulic tools from Darda GmbH – such as concrete demolition shears, rock and concrete splitters, combination shears, multi cutters, steel shears, or tank cutters – the control cabinet coordinates the interaction of the hydraulic power unit, valve technology, sensors, and operation. It ensures that commands like Start, Open/Close, Split, or Relieve Pressure are executed reliably, reproducibly, and safely – even under demanding conditions in concrete demolition, strip-out, rock excavation, tunnel construction, natural stone extraction, or special operations. The result is consistent process control, high availability, and a robust operating concept tailored to harsh environments.

Definition: What is meant by a control cabinet?

A control cabinet is an enclosure that brings together electrical and electronic components for controlling and safeguarding technical processes. It houses switching devices (e.g., contactors, relays), protective and monitoring equipment (circuit protection, motor protection, residual-current protection), controllers (e.g., PLC), indication and operating elements (pushbuttons, indicator lights, emergency stop), as well as interfaces (connectors, terminals, radio and cable interfaces). In contrast to a large-format switchgear cabinet, the control cabinet is often more compact, mobile, or mounted close to the machine and tailored to a specific function – such as the safe operation of a concrete demolition shear or a rock and concrete splitter. The goal is the safe, standards-compliant and robust implementation of switching and control tasks in harsh environments with clear separation of control and power circuits, well-structured cable routing, and adequate thermal management.

Design and components of a control cabinet

The design is determined by the task (power distribution, control, safety) and the operating environment. In applications with hydraulic power packs and hydraulic tools from Darda GmbH, typical functional groups are combined to control and safeguard movements (open/close, forward/back), forces, and pressures in a targeted way. A logical layout with segregated voltage levels and safety circuits supports maintainability and fault finding.

Enclosure and degrees of protection

The enclosure protects the internals against dust, moisture, impacts, and vibration. Common IP degrees of protection (e.g., IP65/IP66) ensure operation with splashing water, drilling slurry, and dust. Mechanical impact resistance (e.g., IK ratings) and corrosion-resistant materials are important on construction sites and in tunnel construction. A well-sealed cover, cable glands, and proper drainage help prevent condensation.

• Optional pressure equalization elements reduce condensation through breathing without water ingress.
• Appropriate cable glands with strain relief and sealing inserts maintain the IP rating under movement.
• Surface treatments and stainless components improve longevity in aggressive atmospheres.

Power distribution and protection

Within the control cabinet, supplies are distributed, feeders are protected, and drives are safeguarded. Typical components include:

• Main switch and interlocks
• Circuit breakers, motor protection switches, thermal and electronic overload relays
• Residual-current protection (depending on use), surge protection, line filtering (EMC)
• Power supplies (e.g., 24 V DC for sensors/control)
• Verified short-circuit rating and selective coordination for clear fault isolation
• Provisions for lockout-tagout and safe energy dissipation

Control technology

Depending on complexity, relay logic or PLC-based controls are used. Solenoid valves on the hydraulic power pack are actuated; pressure sensors and limit switches provide status feedback. In applications with concrete demolition shears, interlocks are common to prevent inadmissible motion sequences, while with rock and concrete splitters the focus is on a safe pressure build-up and relief sequence. Deterministic cycle times and debounced signal processing ensure reproducible motion profiles.

Operating elements and indication

• Emergency stop as a mushroom pushbutton, wired for functional safety
• Command pushbuttons (Start, Stop, Open/Close, Split, Relieve Pressure)
• Selector switch (operating modes: manual/automatic/service)
• Indicator lights/displays for readiness, fault, pressure reached
• Optionally illuminated, color-coded pushbuttons for intuitive state feedback

Interfaces and communication

Wired hand-held controls, connectors for valve manifolds, potential-free contacts for enables, and optionally radio control with safety-related signal transmission. In larger systems, fieldbuses or serial interfaces are possible – with vibration-resistant connectors and strain reliefs in dust- and shock-exposed environments. Consistent shielding, equipotential bonding, and EMC-compliant cable separation maintain signal integrity.

Function in concrete demolition, special deconstruction, and rock excavation

In deconstruction and natural stone extraction, the control cabinet coordinates the interaction of hydraulic power, tool motion, and safety functions. Targeted enables, pressure limits, and defined sequences ensure that movements remain controlled even under fluctuating loads.

• Concrete demolition shears: Control of opening/closing, holding functions, pressure monitoring, interlock to prevent unintentional closing when a guard position is open.
• Rock and concrete splitters: Sequence control for pressure build-up, splitting impulse, and pressure relief; feedback when splitting pressure is reached; monitoring of temperature and duty cycle at the power pack.
• Combination shears, multi cutters, steel shears: Soft start, end-position logic, load monitoring to avoid overload.
• Tank cutters: Special consideration of spark avoidance through appropriate switching device selection and EMC measures; clear separation of control and power circuits.
• Power management: Automatic stand-by and ramped restarts reduce idling losses and mechanical stress.

Actuating hydraulic power packs

Start/Stop of the power pack, pump selection, switching between pressure/flow rate, valve enables, and pressure limiting are logically linked in the control cabinet. This allows movements to be executed in a targeted and reproducible manner. Soft-start strategies and ramp functions help minimize pressure shocks and extend component life.

Pressure and force control

Setpoints and limits are monitored via pressure switches, sensors, or analog signals. This is essential for splitting operations and for cutting with high force. Depending on the application, open-loop limiting is supplemented by closed-loop control to stabilize force under varying material resistance.

Interlocks during tool change

The control cabinet can issue enables only after pressure relief and tool acknowledgment. This prevents unintended start-up of hydraulic components. Additional plausibility checks (e.g., valve neutral position confirmed) further reduce residual risk.

Selection criteria for control cabinets in harsh environments

Selection depends on location, tool, power demand, and safety requirements:

• Degree of protection and robustness: IP protection, shock and vibration resistance, UV resistance, corrosion protection.
• Temperature range: Starting capability in cold conditions, heat dissipation under continuous load; condensation management.
• EMC and power quality: Mitigation measures with frequency converters, long cables, and generator operation.
• Safety functions: Emergency stop, safe enables, interlocks; design based on risk assessment.
• Service access: Clearly wired terminals, clear labeling, sufficient space reserves.
• Cable management: Strain reliefs, kink-free routing, abrasion-resistant jacket materials.
• Modularity: Expandability for additional sensors or further valve sections.
• Documentation: Circuit diagrams, terminal plans, bills of materials, test records, unambiguous designations.
• Weight and handling: Portable design with protected grips and lifting points where mobile use is required.
• Lifecycle considerations: Availability of spare parts, standardized components, and versioned software.

Installation and commissioning

Proper installation is a prerequisite for safe operation, especially in mobile applications in deconstruction or tunnel construction.

Mounting location and fastening

The control cabinet is mounted for accessibility, protected from splashing water, and with minimal vibration. Heat ingress from sun exposure or the power pack’s exhaust is avoided. For mobile use, shock-absorbing mounts are advisable.

• Observe minimum clearance for ventilation and service access.
• Verify fastening torque and use locking elements against loosening under vibration.
• Route cables with compliant bending radii and adequate chafe protection.

Wiring and labeling

Conductor cross-sections, ferrules, color-compliant core identification, and clear terminal markings simplify maintenance and troubleshooting. For hand-held controls and sensor circuits, tread-resistant connectors are important. Consistent wire numbering, durable labels, and QR-linked documentation support fast diagnostics.

Testing and functional acceptance

Before operation, insulation resistance, protective conductor continuity, phase sequence (for three-phase consumers), emergency stop function, interlocks, and all operating modes are tested. The machine leaves the assembly area only after documented acceptance. Depending on the design, direction of rotation, voltage drop under load, and validation of safety functions are also recorded.

Safety-related functions

Safety functions are defined according to the risk assessment. Typical measures include dual-channel emergency stop circuits, safe enables, monitored valve return, and defined stop categories. In applications with concrete demolition shears and splitters, uncontrolled motions and pressure spikes must be avoided. Performance and safety levels are determined by applicable standards; a project-specific evaluation is essential. Common frameworks include principles from ISO 13849 and IEC 62061 for determining required performance levels.

• Emergency stop: Redundant design, force-guided contacts, clear labeling.
• Enable chains: Mode selector switch, door/lid monitoring (if present), pressure relief as a start condition.
• Diagnostics: Fault messages with clear assignment (e.g., Valve A stuck, pressure switch B not reached).
• Reset logic: Manual reset with restart interlock prevents unexpected motion after faults or power loss.

Maintenance, inspection, and troubleshooting

Regular visual and functional checks increase availability and safety. Maintenance intervals depend on usage intensity and environmental conditions.

1. Open the enclosure; visual inspection for moisture, dust, loose parts.
2. Tighten terminals, check connectors, inspect seals.
3. Functional test: emergency stop, operating modes, end positions, pressure switches.
4. Thermography or temperature measurement under load during continuous operation.
5. Update documentation: changes, spare part replacements, test results.
6. Clean vents and filters, check pressure equalization elements, and remove deposits from cable entries.

Typical faults and remedies

• Loose terminal/connector: leads to sporadic failures – tighten terminals, check strain reliefs.
• Condensation/corrosion: dry, replace seals, use dehumidifier if necessary.
• Thermal trip: check load profiles, improve ventilation, correctly size protective devices.
• Defective operating elements: replace pushbuttons/switches with mechanical wear in good time.
• EMC interference: separate power and signal wiring, ensure shielding continuity, add filters if required.

Environmental conditions, degrees of protection, and materials

Concrete dust, moisture, salt exposure (e.g., in tunnel construction), temperature fluctuations, and vibration require robust enclosures, high-quality seals, and vibration-proof mounting. Materials such as powder-coated metal or high-grade plastics are selected based on weight targets, corrosion risk, and impact loading. Pressure-compensation devices, hydrophobic membranes, and UV-stable gaskets further increase durability in outdoor and semi-outdoor use.

Documentation, labeling, and retrofits

Complete documentation with circuit and terminal diagrams, cable lists, operating manual, and spare parts list facilitates operation and service. Retrofits – such as additional pressure sensors, further valve sections for combination shears, or extended operating logic for rock and concrete splitters – are cleanly documented, labeled, and tested. Change indices and digital access to current documents support configuration control over the entire lifecycle.

Practical examples from application areas

During strip-out, the control cabinet controls compact hydraulic power packs for concrete demolition shears directly inside the building; a wired hand-held control enables finely metered movements with minimal spark and dust risk. In tunnel construction, particularly high requirements for IP protection, EMC, and vibration resistance must be met. In natural stone extraction, the control cabinet prioritizes a process-secure pressure sequence for splitters to achieve clean fractures. In special operations – such as with limited power supply – a robustly designed power path with monitoring ensures reliable operation even under fluctuating generator conditions.

Future topics: condition monitoring and digital signals

Sensors for temperature, humidity, and switching cycles enable predictive maintenance. Event logs and clearly structured diagnostic signals reduce downtimes. Even in harsh environments, this improves availability and process quality – without compromising simple, robust operability. Edge-capable data acquisition, standardized diagnostic codes, and secure remote updates prepare the control cabinet for data-supported service concepts.

Demarcation and classification

The term control cabinet is used in practice for compact, machine-proximate units. Larger, stationary installations with extensive power distribution are often referred to as switchgear cabinets, while portable operator boxes appear as hand-held control units or control panels. For hydraulic applications with tools from Darda GmbH, a clear division of tasks has proven effective: the control cabinet consolidates operation, protection, and control logic; the hydraulic power pack delivers the power; the tool-side mechanics (e.g., concrete demolition shear, rock and concrete splitter) safely convert the commands into force.