Hydraulic shears are central tools in professional demolition, in strip-out, and for precise cutting of construction materials and metals. They operate with hydraulic pressure, converting it into high pressing or cutting forces to enable safe, controlled separating, crushing, or pulverizing. In the Darda GmbH environment, the spectrum ranges from concrete demolition shears for reinforced concrete to combination shears and Multi Cutters, as well as specialized steel shears and tank cutters. In addition, hydraulic rock and concrete splitters and rock splitting cylinders are used when material is not cut but split with minimal residual stress. This combination allows quiet, low-vibration, and predictable workflows in many applications.
Definition: What is meant by hydraulic shear
A hydraulic shear is a hydraulically actuated tool with two or more jaws that separates materials by cutting, crushing, pressing, or breaking. Energy is supplied by a hydraulic power pack via hoses; cylinders in the shear convert oil pressure into mechanical force at the jaws. Depending on the configuration, the hydraulic shear serves as a concrete demolition shear (breaking and downsizing concrete, exposing reinforcement), as a steel shear (severing sections, pipes, rebar), as a combination shear or Multi Cutter (interchangeable sets for concrete and steel), or as a tank cutter (cold cutting of thin to medium-thickness sheet and tank walls). In demolition and specialized deconstruction, the term is often used as an umbrella term for hydraulic demolition shears on excavators.
Function and design
Hydraulic shears typically consist of a base body, one or more hydraulic cylinders, a pivoted jaw mechanism with joints and pins, and interchangeable blades, teeth, or crushing inlays. Via hydraulic hoses, oil flows from the power pack into the cylinder that closes the jaws; in double-acting systems, opening is also hydraulically assisted.
Force transmission
Crucial is the linkage between cylinder and jaws: depending on geometry, the force at the jaw tips is multiplied many times over. This enables high cutting forces for rebar and sections or large pressing forces for fracturing concrete.
Hydraulic power packs
Energy supply is provided by hydraulic power units with defined pressure and flow rate. Proper sizing is essential for cycle times and consistent performance. In practice, compact, electrically or gasoline-driven power packs are used for handheld shears, while attachment shears on carrier machines are fed by the excavator hydraulic system.
Tool sets and inserts
Many hydraulic shears, especially combination shears and Multi Cutters, allow changing jaws or cutting sets. This lets users switch between concrete-crushing jaws and steel-cutting sets without changing the base tool. Concrete demolition shears often feature replaceable tooth segments; steel shears commonly have adjustable blades.
Types and differentiation
Hydraulic shears can be distinguished by task, size, and drive type. The following classification is common in practice:
- Concrete demolition shears: For breaking concrete and exposing and separating reinforcement. Teeth break the concrete; integrated cutting edges sever rebar.
- Combination shears: Interchangeable or combined jaws for concrete and steel; suitable for heterogeneous structures.
- Multi Cutters: Universal cutting tools for pipes, sections, and sheet in strip-out and deconstruction.
- Steel shears: Optimized for high cutting forces and edge stability when cutting steel beams, rebar bundles, or scrap.
- Tank cutters: For cold cutting of tanks and vessels when spark generation should be reduced.
Distinct from these are rock and concrete splitters and rock splitting cylinders. They do not cut but generate controlled tensile splitting stress in the material via hydraulically driven wedges. This is particularly suitable in rock excavation and tunnel construction and for natural stone extraction when vibration, noise, or sparks must be avoided. In many projects, concrete demolition shears and rock and concrete splitters complement each other.
Fields of application and typical uses
Hydraulic shears combine precision with high force. In combination with Darda GmbH products, the following areas enable efficient workflows:
Concrete demolition and specialized deconstruction
Concrete demolition shears separate slabs, walls, and beams in a controlled manner. By breaking sequentially from the edge to the center, load paths can be managed. Where massive components are present, pre-splitting with rock and concrete splitters can initiate cracking and significantly ease the shears’ work.
Strip-out and cutting
In interior demolition, Multi Cutters and combination shears are used to cut lines, cable trays, sections, rebar bundles, or façade substructures. Specialized steel shears speed up bundle cutting. For space-constrained tasks, handheld shears combined with compact hydraulic power packs are practical.
Rock excavation and tunnel construction
In heading and support work, cutting with a hydraulic shear is often secondary; rock splitting cylinders and rock and concrete splitters dominate here. Nevertheless, hydraulic shears are used to remove overbreak, cut anchors, meshes, and support elements, and for removing temporary concrete placements.
Natural stone extraction
In quarries, rock splitting cylinders create targeted split joints, while hydraulic shears handle auxiliary tasks such as cutting tensioning cables, clamps, and steel supports. For the step “from block to transport size,” combining splitting with secondary downsizing using shears is often advantageous.
Special applications
For work on tanks, in sensitive facilities, or areas with potential ignition risk, cold cutting with tank cutters and suitable steel shears can offer advantages. This presupposes a careful hazard analysis, appropriate procedures, and matched hydraulic power packs.
Selection criteria and sizing
The appropriate hydraulic shear depends on material, component geometry, accessibility, and available hydraulic power. The following criteria are relevant in practice:
- Jaw opening and geometry: Must suit material thickness and component shape; in concrete shears, tooth and nose geometry influences fracture behavior.
- Cutting or pressing force: Determined by system pressure and cylinder area as well as lever linkage. High cutting forces are required for reinforcement and sections; for concrete, the resulting pressing force at the teeth is key.
- Weight and handling: For handheld tools, weight and balance affect fatigue; for attachments, the carrier’s capacity is decisive.
- Hydraulic parameters: Required pressure and flow must match the hydraulic power pack. Cycle times (open/close) are critical to productivity.
- Blade/tooth material: Wear resistance, adjustability, and refurbishment options influence operating costs.
- Compatibility: Hose connections, couplings, control logic, and possible rotators (on attachments) must be matched to the system.
Hydraulic power packs: energy supply and integration
Hydraulic power packs provide pressure and flow for hydraulic shears. Clean matching increases performance and service life.
Performance data
Key factors are operating pressure, flow rate, tank volume, and cooling. Adequate cooling stabilizes oil temperature under continuous load; filtration protects cylinders and valves.
Control and connection
For handheld systems, robust control valves, smooth couplings, and kink-resistant hoses are key. For attachments, proportional controls and rotators affect positioning accuracy.
Power source
Depending on the environment, electrically driven, acoustically unobtrusive power packs or mobile combustion-engine units are suitable. In emission-sensitive areas, appropriate measures and coordination with site management are required.
Safety and occupational health
Working with hydraulic shears requires forward planning. The following notes are general in nature and do not replace a project-specific risk assessment:
- Hazard zone: Secure pinch and shear points; maintain adequate distances and line of sight.
- Component stability: Assess load paths before cutting; avoid uncontrolled collapse; shore or rig as needed.
- Hydraulic pressure systems: Protect hoses, secure couplings, and relieve pressure before disconnecting components.
- Dust and noise: Provide dust suppression (e.g., water mist); consider noise control and hearing protection.
- Hot/cold cutting methods: Where sparks must be avoided, include cold cutting with suitable shears in the selection; observe clearance measurements and permits.
- Personal protective equipment: Use helmet, eye protection, hand protection, safety footwear, and additional PPE as required by the task.
Work methodology in deconstruction
Thought-out sequences increase efficiency and safety in concrete demolition and specialized deconstruction as well as in strip-out:
- Prepare: Disconnect services, check rebar drawings, secure the work area, position hydraulic power packs.
- Pre-tension/pre-splitting: On massive components, initiate cracks with rock and concrete splitters to let shear forces act optimally.
- Downsize: Work from the edge with concrete demolition shears, selectively expose reinforcement, and cut it with cutting inserts.
- Source separation: Separate steel to simplify transport and recycling.
- Finishing: Dress edges, remove embedded parts, and cut remaining pieces with Multi Cutters or steel shears.
Maintenance, wear, and service life
Regular care increases availability and reduces costs:
- Blades and teeth: Check for wear, adjust or replace; address damaged edges early.
- Joints and pins: Ensure lubrication; check bearing play.
- Hydraulics: Inspect seals and hoses, observe filter intervals, monitor oil quality.
- Bolted joints: Check torques as specified, especially after changing tool sets.
- Storage: Clean, preserve, and store tools in a protected manner.
Performance in sensitive environments
Compared to percussive methods, hydraulic shears work with low vibration. This favors use near existing buildings, in hospitals, or laboratories. Where additional vibration reduction is required, the process can be prepared with rock and concrete splitters to lower the load for the concrete demolition shear. Instrumented monitoring can help document compliance when building vibrations must be limited.
Standards, guidelines, and documentation
For planning, operation, and documentation, generally accepted rules of technology apply. Depending on the application, these include, for example, machine safety requirements, operational training, evidence of dust and noise mitigation, and permits for work in special areas. Binding assessments must be made on a project-specific basis; the information provided here is general in nature.
Typical mistakes and how to avoid them
- Unsuitable shear selected: Jaw opening, cutting force, or tooth geometry does not match the component. Remedy: determine requirements in advance; consider combining with rock splitting cylinders.
- Undersized hydraulic power pack: Flow rate too low, leading to longer cycle times. Remedy: size the power pack appropriately for pressure and flow.
- Unfavorable attack points: Cutting into solid sections instead of pre-weakened zones. Remedy: pre-break or pre-split the component and plan cut lines.
- Neglected maintenance: Dull blades increase force demand and degrade cut quality. Remedy: regular inspection and rework.
- Safety distances not observed: People within the slew or drop zone. Remedy: barriers, spotters, clear communication.
Practical application examples
When deconstructing a reinforced concrete slab, a controlled crack line can first be created with rock and concrete splitters. The concrete demolition shear then downsizes the segments and separates the reinforcement. In strip-out, Multi Cutters are used for cable trays and pipes, and steel shears for sections. In facilities with heightened ignition-control requirements, the cold cutting of tank plates with tank cutters can be planned, provided operational clearances are in place and the hazard analysis supports it.