The safety distance is a central principle in demolition, deconstruction, rock cutting/processing and cutting technology. It defines the protected area around the machine, material and personnel so that crushing, cutting and fragment hazards as well as uncontrolled movements of components remain under control. Especially when working with concrete demolition shears, rock and concrete splitters or stone splitting cylinders, but also with combination shears, multi cutters, steel shears and tank cutters, a correctly dimensioned safety distance determines whether execution remains calm and predictable – in concrete demolition and special deconstruction, during strip-out and cutting, in rock excavation and tunnel construction, in natural stone extraction and during special operations.
Definition: What is meant by safety distance
Safety distance is the spatial separation zone between the hazard source and people or property, dimensioned so that foreseeable movements, energy inputs and spalling during normal operation and deviations (e.g., component misalignment, material fracture, pressure relief) cause no harm. It includes the tool’s work zone, the movement envelopes of the carrier, the potential hazard cone for fragment ejection, and buffer zones for unplanned events. Safety distance is therefore not a fixed value but a dynamic protection zone derived from the hazard analysis and continuously monitored and adjusted during the work.
Significance in demolition and rock operations: objectives, risks and interactions
In practice, the safety distance serves to decouple the effects from force, pressure, tension and vibration. Cutting, splitting and crushing generate energy redirections that can lead to component rotation, uncontrolled cracking, spalling or hose movements. Tools such as concrete demolition shears generate shear and crushing zones; stone and concrete splitting devices as well as stone splitting cylinders create controlled crack formation in concrete and rock; combination shears, multi cutters and steel shears cut metallic reinforcement and sections; tank cutters separate vessel walls. In all cases, an appropriate safety distance protects people, infrastructure and the carrier, reduces downtime due to incidents and increases process quality.
Safety distance with concrete demolition shears
Concrete demolition shears apply high shear and compressive forces to components. Typical risks are pinch points, snap-back due to stress-free release of reinforcement, and fragment ejection.
Hazard zones and buffer areas
- Tool proximity: The immediate shear area including the closing path is off-limits. Approach only when fully stopped and depressurized.
- Component movement: Upon separation, the component can tip, rotate or fall. The safety distance includes the potential rotation radius plus a buffer.
- Fragment cone: Concrete spalls often follow a fan-shaped pattern. Lateral clearance and protection mats or shields reduce the risk.
Practical guidance
- Shore components or cut in sections to avoid uncontrolled movements.
- Expose reinforcement and cut it selectively before separating load-bearing areas.
- Ensure signals and line-of-sight between operator and spotter; strictly cordon off access to the demolition zone.
Safety distance with stone and concrete splitting devices and stone splitting cylinders
In hydraulic splitting, pressure is introduced via wedges or cylinders into a borehole, causing cracks to propagate along preferred planes. Stresses shift within the material, and non-explosive rock removal effects can occur – controlled, but with possible stone ejection or component distortion.
Key aspects
- Crack progression: Cracks follow material disposition, reinforcement, joints and discontinuities. Safety distance covers the expected crack path and a lateral buffer.
- Energy relief: Sudden crack run-throughs can displace components. Personnel protection is provided from a laterally offset position and never in line with the split joint.
- Wedges and cylinders: Approach only in a depressurized state. Engaging, setting and releasing are performed in a controlled manner; hose routing is kept free from tension and abrasion.
Rock excavation and natural stone extraction
- Analyze existing joint systems; plan crack propagation along discontinuities.
- Use coverings or nets when stone ejection is possible.
- On slopes, keep the runout zone clear; personnel stand above and laterally to the joint.
Hydraulic power packs and high-pressure lines: sensibly dimensioning clearances
Hydraulic power packs (power units) feed the tools and generate pressure, heat and noise emissions. Safety distances account for radiated heat, exhaust routing, refilling areas and hose routing up to the tool.
- Hoses: Avoid mechanical damage; route without kinks or abrasion. Do not remain within the direct jet zone of potential leaks.
- Power packs: Keep a work corridor clear around the service area; do not block air inlets and outlets.
- Pressure relief: Before coupling, retooling or maintenance, depressurize the system and secure against re-energizing.
Cutting technology: combination shears, multi cutters, steel shears, tank cutters
Cutting tools create separation cuts in which energy is locally released. Metallic components can snap, rotate or be under pre-stress.
- Combination shears / steel shears: Plan cut lines, create controlled holding tabs, secure components. No personnel within the swing range.
- Multi cutters: Note spark projection and chip ejection transverse to the cut line; store combustible materials outside the ejection zone.
- Tank cutters: Cutting in the vessel environment only with approved procedures. Align safety distances to possible gases, vapors and convection; plan ignition source control and continuous monitoring.
Safety distance across application areas
Concrete demolition and special deconstruction
- Identify load paths, secure load paths, cordon off drop zones.
- Use concrete demolition shears to separate components in controlled sequences; the safety distance accounts for tipping angle and drop corridor.
Strip-out and cutting
- Tight layouts require time-based separation: only one trade in the hazard area at a time.
- Increase downrange clearance on the spark side during cutting; shield sensitive lines.
Rock excavation and tunnel construction
- In tunnels, add time spacing due to limited visibility and ventilation.
- With stone and concrete splitting devices, read crack guidance, barricade the breakout zone, secure the rear area.
Natural stone extraction
- Keep an eye on the working bench and slope: keep the downhill runout zone clear.
- Define nets, mats and spotters; separate access and haul routes.
Special operations
- Unknown material states require conservative distances and stepwise approach.
- Use monitoring (measuring wedges, crack markers, cameras) to shrink the zone once behavior is verified.
Procedure for determining the safety distance
- Develop a hazard profile: Material, component geometry, reinforcement, stresses, surroundings.
- Record tool and carrier data: Reach, pressing or splitting force, cutting speed, swing ranges.
- Define zones: Core work area (machine only), hazard area (authorized personnel only), observation area (spotter, line-of-sight).
- Set buffers: Allowances for fragment ejection, component movement, hose swing and visibility/communication limits.
- Secure and mark: Barriers, signage, spotters, radios.
- Monitor and adjust: Dynamically correct the safety distance when the component’s behavior changes.
Practical reference values and calculation approaches
Concrete values depend strongly on equipment, material and environment. In practice, reference models have proven useful and are then verified for the project:
- Machine envelope: Maximum swing or working radius of the carrier plus a circumferential allowance as buffer.
- Component movement: Possible tipping path of the released component; set distance so the entire drop and rotation zone remains clear.
- Fragment cone: Lateral allowance depending on material and processing method; shielding allows reduction.
- Hose and line path: Additional clearance in front of and lateral to the line to cover pendulum and pressure surge movements.
Example idea (non-binding): For concrete demolition shears with reach R plus expected component rotation and lateral fragment cone, plan the safety distance as the sum of R, a rotation buffer and a lateral allowance, then verify and adjust on site.
Organizational measures for compliance
- Access control: Clear roles, markings and barricades; only authorized personnel in the hazard area.
- Communication: Unified hand signals, radio discipline, fixed rally points.
- Lines of sight: No work without direct sight between operator and spotter; define alternative camera perspectives.
- Sequencing: Spatial and temporal separation of trades at interfaces.
Technical measures to reduce the safety distance
- Protection mats and nets: Fragment capture reduces lateral allowances.
- Shoring and catch scaffolds: Limit component movements during cutting or splitting.
- Water mist: Binds dust and dampens light fragments.
- Tool selection: Properly sized concrete demolition shears or stone and concrete splitting devices reduce uncontrolled energy inputs.
Additional aspects: environment and weather
- Ground and slope: Slip and tipping risks influence the buffer.
- Wind and visibility: Consider spark travel, dust plumes and communication quality.
- Noise: Ensure adequate intelligibility; increase observation distance if needed.
Personal protective equipment
- Eye and face protection against flying fragments.
- Helmet and hand protection near pinch points.
- Hearing protection near power packs and cutting technology.
- Match cut resistance and sure-footedness of clothing to the task.
Common mistakes and how to avoid them
- Static distances: Do not treat safety distances as a fixed value; update them dynamically.
- Underestimated residual stresses: Plan conservatively, especially with prestressed concrete and jointed rock.
- Unclear responsibilities: Clearly designate spotter, operator and supervisor.
- Uncontrolled hoses: Secure lines against whipping and kinking.
Documentation and evidence
- Hazard analysis with zone plan, communication routes and barricades.
- Photo documentation of barriers and adjustments during execution.
- Task- and area-specific briefings for all participants.
Legal and insurance classification
The safety distance follows recognized engineering practice and is derived from the specific hazard analysis. Requirements may vary by country, contract and site. The information in this text is general in nature and does not replace binding project specifications or regulatory requirements. The governing basis is always the project-specific instructions, approvals and documentation.