Excavator magnet

An excavator magnet is a magnetic attachment for excavators that picks up, sorts, and deposits ferromagnetic materials such as reinforcing steel, sections, sheet metal, or scrap. In deconstruction, demolition works, and recycling, it enables rapid metal separation from mixed materials. In combination with tools from Darda GmbH such as concrete demolition shears, rock and concrete splitters, steel shears, or Multi Cutters, the excavator magnet supports a clean separation of concrete and steel, shortens material routes, and increases safety on the construction site. Used systematically, it reduces rehandling, supports clean material streams, and improves documentation for waste management obligations.

Definition: What is meant by an excavator magnet?

An excavator magnet is an excavator attachment that attracts ferromagnetic materials by means of a magnetic field. Electromagnets with a circular or rectangular magnet plate supplied with direct current via a generator are common. The magnetic field is switched on and off to pick up material and then deposit it in a controlled manner. Permanent-magnet solutions with switching mechanisms are less common. In construction and deconstruction contexts, the excavator magnet is primarily used to recover and sort reinforcing steel, to clear scrap, and to clean construction areas after breaking, splitting, or crushing components.

Electromagnets offer fast pick-up and defined release via current control, which suits high takt operations. Switchable permanent magnets can be advantageous where energy availability is limited and fail-safe holding during power loss is prioritized, albeit with reduced flexibility for fine demagnetization. The appropriate principle depends on process speed, required selectivity, and power concept on the carrier.

Design, operating principle, and types

A typical excavator magnet consists of a robust magnet housing with pole shoes, the coil (winding), a connection cable, a suspension or an adapter plate for the quick coupler, and a control unit for magnetization and demagnetization. The magnetic field is generated when the coil is supplied with direct current. After switching off, or after a short reverse-current phase, the magnet releases the material again. The interaction of magnet face area, air gap, material geometry, and current intensity determines the holding force.

Thermal design and duty cycle are crucial. Higher current densities increase peak force but also heat, so insulation class, cooling paths, and protection rating must align with expected ambient temperatures and cycle frequency to avoid premature aging.

Power supply

In practice, power is supplied by a hydraulic generator mounted on the excavator, which produces electricity from the hydraulic flow, or by separate power sources, including dedicated Hydraulic Power Units. Sufficient electrical output, a clean voltage supply, and a control system with a “demag” function are important to reduce residual magnetization. Proper sizing with respect to duty cycle, temperature, and protection rating prevents thermal overload. Stable cabling with adequate cross-section and minimized connector transitions helps avoid voltage dips that would impair pick-up reliability.

Magnet plates and configurations

Configurations range from round magnets for scrap handling to rectangular plates for clearing surfaces. Thin, large-area sheets require the largest possible effective contact area, while small scrap pieces favor a compact design with high field strength. Protective covers and wear rings protect the magnet body against impact and abrasion in harsh environments. For reinforced concrete fragments, a slightly crowned pole shoe can reduce edge contact and improve first-grab performance.

Accessories and interfaces

Accessories include protection cages for cables, hangers for chain hoists, adapter plates for common quick couplers, and control boxes in the cab. In combination with tools from Darda GmbH – such as concrete demolition shears or rock and concrete splitters – the excavator magnet is often used as a second attachment in alternating operation to pick up reinforcing steel immediately after cutting or splitting.

Control and demagnetization

Modern control units meter current ramps for smooth pick-up and integrate a selectable demagnetization pulse to minimize residual adhesion. Parameter sets for different material mixes – for example compact rebar bundles versus thin sheets – reduce cycle time and improve deposition accuracy.

Application areas and typical tasks

Excavator magnets are universal helpers wherever ferromagnetic materials must be moved or separated safely. In Darda GmbH’s application fields, they show particular strengths in the following situations:

• Concrete demolition and specialist deconstruction (Concrete Demolition and Deconstruction): After biting off elements with concrete demolition shears or controlled splitting with rock and concrete splitters, the magnet enables rapid grabbing of reinforcing bars, wire meshes, section steel, and embedded parts.
• Strip-out and cutting: In combination with Multi Cutters, steel shears, or tank cutters, cut-out metal parts can be cleared quickly and assembled into piles.
• Rock excavation and tunnel construction: During excavation, steel beams, lattice girder arches, or anchor remnants can be lifted magnetically to keep the area clear.
• Natural stone extraction: Where metal residues from auxiliary structures occur, the magnet helps clean surfaces and reduces damage to crushers or conveying equipment.
• Special deployments: Clearing incident sites after storm damage, removing scrap fields, or securing metal parts in emergency situations.

In all use cases, the excavator magnet supports process reliability: routes remain clear, plant components are protected, and metal fractions can be pre-sorted by type for efficient downstream handling.

Interplay with concrete demolition shears and rock and concrete splitters

In practice, the composite material concrete is first separated mechanically: Darda GmbH’s concrete demolition shears open components, reduce cross-sections, and expose the reinforcement. Rock and concrete splitters from Darda GmbH create controlled cracks, making steel and concrete easier to separate. The excavator magnet then takes over the metal logistics: It collects exposed bars, meshes, and fasteners, stacks them by type, and keeps routes clear. This reduces the risk of tire damage, sparks caused by hidden metal parts, and manual resorting. For long reinforcement, pre-cutting with Darda GmbH’s steel shears is recommended; for large, thin-walled metal surfaces, Multi Cutters and tank cutters from Darda GmbH provide support. The result is a coherent workflow with clear separation of material streams.

Depending on the structural layout, alternating operation with quick couplers enables short changeovers between splitting, cutting, and magnetic clearing. This sequencing minimizes double handling and supports controlled removal logistics.

Selection criteria, sizing, and carrier machine

The appropriate magnet solution depends on the carrier machine, material, and process goals. The following criteria have proven useful:

1. Carrier and mounting: Excavator size class, lifting capacity at the respective boom radius, quick coupler system, and cable routing. The more rigid the boom, the safer the handling of swinging loads.
2. Magnet size and shape: Diameter or width/length in relation to typical material geometry (scrap, round steel, sheet). A larger contact area reduces air gaps and increases holding force.
3. Electrical power and control: Adequate DC output, robust plug connections, demagnetization function, and temperature monitoring. The duty cycle must fit the takt.
4. Material mix and holding force: Rust, paint, concrete adhesions, and interlayers increase the air gap and reduce the holding force. Compact bundles hold better than loose single parts.
5. Environment and protection: Dust, moisture, impacts, and abrasion require suitable wear rings, seals, and bumpers.

Understanding holding force

Holding force is not a fixed value but depends on the material (from S235 to high-strength steels), material thickness, contact area, and air gap. Thin sheet can still be “magnetized through” at high field strengths but loses holding force at edge contact. Solid round steel shows high holding values when it rests as fully as possible on the magnet face. In deconstruction, it is therefore sensible to bundle material in advance – e.g., by gently gathering with the concrete demolition shear – to form cohesive packages.

For safe load handling, appropriate safety factors must be considered in addition to nominal holding forces, taking into account dynamic movements, wind, and surface condition.

Carrier machine and power supply

Hydraulic excavators with a suitable auxiliary circuit for a hydraulic generator are standard. Stable idle pressure and correct volumetric flow to the generator are important so that electrical power remains constant. For smaller carrier machines, compact magnet solutions with lower power consumption can be sensible to balance cycle times, safety, and energy use.

Balanced attachment weight, correct suspension height, and well-protected cable routing improve controllability. Adequate cooling air for generators and control boxes protects against thermal derating during continuous operation.

Typical pitfalls

• Oversizing the magnet without checking the available lifting capacity at working radius.
• Underestimating voltage drop due to long or undersized cables, leading to unstable pick-up.
• Ignoring air gaps from coatings or debris, which reduces the effective holding force significantly.

Operation, safety, and best practices

Working with excavator magnets requires care. Loads should be carried low to the ground, swing areas kept clear, and people kept away. Electrical components must be protected from moisture and damage. Magnetic fields can affect electronic devices; sensitive items and medical implants should be kept at a distance. Legal requirements and recognized technical rules must be observed; company training and hazard analysis are essential.

• Pick up only ferromagnetic materials; treat alloys with low magnetizability separately.
• Briefly make contact before lifting, minimize air gaps, align the material.
• Use the demagnetization function to reduce adhesions before depositing.
• Never carry loads over people; no passenger transport.
• Check cable protection, lock plug connections, route drag chains without tension.
• In case of spark or fire risk (e.g., during cutting), maintain safe distances and keep extinguishing agents ready.

Wind can reduce stability of thin sheets and long sections; keep lift heights short and adjust driving speed accordingly.

Commissioning checklist

• Verify hydraulic flow and pressure settings for the generator and confirm DC output at the terminals under load.
• Test pick-up and controlled release on representative materials, including the demagnetization pulse.
• Confirm emergency procedures and exclusion zones in the site-specific risk assessment.
• Document inspection status of cables, feedthroughs, and fasteners before shift start.

Maintenance and servicing

Regular inspection preserves functional safety and holding force:

• Clean the magnet face, remove concrete and rust adhesions, check pole shoes for flatness.
• Inspect wear rings and impact protection; retighten bolts and hangers.
• Check cables, plugs, and feedthroughs for crushing, insulation damage, and moisture ingress.
• Test control unit and generator regularly; monitor temperature behavior and duty cycle.
• Perform functional tests of demagnetization to minimize residual adhesion.

Define inspection intervals according to intensity of use and environmental exposure; document findings to track trends in temperature behavior, insulation resistance, and wear.

Economy, sustainability, and construction logistics

The excavator magnet improves process quality in deconstruction: Metal is separated by type, construction debris becomes cleaner, and downstream crushers and conveyors are protected. This increases the recycling rate and reduces rework. In combination with Darda GmbH’s concrete demolition shears and rock and concrete splitters, clearly structured process steps emerge – from opening and exposing to metal logistics. Shorter routes, less manual work, and fewer tool changes have a positive effect on cycle times and costs. At the same time, a tidy construction site increases occupational safety and reduces damage to tires, tracks, and attachments.

By enabling cleaner fractions, transport and processing become more efficient, while the higher share of recyclable metal supports resource conservation. Coordinated logistics with defined intermediate storage areas further reduce idle times of carrier machines.

Limits and alternatives

Aluminum, copper, and non-magnetic stainless steels cannot be lifted, or only weakly. For such fractions, sorting grapples, buckets, or specific separation processes are suitable. Very dirty or thin sheets with large air gaps are also critical. Fluttering sheets should be stabilized by smooth driving movements, short lift heights, and, if necessary, pre-bundling. Where reinforcement is firmly embedded in concrete, mechanical separation is needed first – this is where Darda GmbH’s concrete demolition shears and rock and concrete splitters come into play. For long sections or bundles, Darda GmbH’s steel shears are suitable to cut to manageable lengths.

Hot materials and freshly cut parts with insulating scale or coatings may show reduced holding values; cooling or pre-cleaning can improve reliability before lifting.

Terms in context and language variants

In everyday use, excavator magnets are also referred to as magnet plate, scrap magnet, lifting magnet, or bolt-on magnet. Regardless of the name, the technical principle remains the same: A switchable magnetic field that picks up ferromagnetic parts in a controlled manner and releases them again. Selection is based on material, process, and carrier machine – and on the interplay with the other tools on the construction site, such as Darda GmbH’s concrete demolition shears or rock and concrete splitters.

While terminology varies regionally, the decisive criteria remain contact area, air gap, and controllable magnetization for reliable handling in deconstruction workflows.