Silo feed is a central topic wherever bulk materials are received, conveyed, metered, and introduced into silos in a controlled way. In the context of concrete demolition, special deconstruction, rock excavation, and tunnel construction as well as natural stone extraction, material flows arise that must be reliably transferred into silos, bunkers, or hoppers—whether as intermediate buffers, for dust extraction, for further processing, or for logistical bundling. Fragment geometry and particle size distribution, as produced for example by Combi-Shears HCS8 for demolition or hydraulic rock and concrete splitters, influence the design of the entire silo feed.
Definition: What is meant by silo feed
Silo feed refers to the entirety of all technical and organizational measures to introduce bulk materials—e.g., crushed aggregates, concrete debris, muck, or additives—into a silo, bunker, or hopper in a controlled manner. This includes receiving, pre-screening, metering, conveying (mechanical or pneumatic), dust separation, level measurement, and safe, uniform distribution inside the silo. The goal is a steady, controlled material flow without bridging, segregation, or overfilling, while ensuring high occupational safety and dust reduction.
Operating principles and systems of silo feed
Depending on the material, throughput, and operating environment, different feeding systems are used. In practice, several principles are often combined to optimally connect receiving, metering, and entry into the silo.
Gravity feeding
The simplest form is free fall via chutes or hoppers. It is suitable for well-flowing, low-fines bulk materials and short distances. To reduce dust development, dust filters and loading skirts are used. For coarse concrete rubble—e.g., after the use of concrete demolition shears—impact plates and energy-absorbing liners reduce wear and impact loads.
Mechanical conveying technology
Mechanical systems enable controlled throughput rates and gentle transport over longer distances and elevations:
- Screw conveyors: suitable for fine to medium size ranges, also for dosing tasks. For abrasive recyclates, wear-resistant liners are important.
- Belt and chain conveyors: flexible routing, suitable for coarse material from rock or concrete demolition. Enclosures/hoods reduce dust.
- Bucket elevators: vertical transport to great heights, a common choice for direct silo charging with screened fractions.
Pneumatic conveying
Pneumatic pressure or vacuum conveying is used especially for fine, dry powders and sands. Airtightness, filtration, and ATEX zone considerations are the focus here. For mixed gradations from crushing and shear processes it is only conditionally suitable, unless fine fractions have been separated beforehand.
Metering and shut-off devices
Rotary airlocks, dosing screws, gates, and flaps are used for uniform feeding into the conveyor and for controlled silo filling. With dusting materials, soft seals improve emissions control; with coarse materials, robust shut-off devices with generous clearances are important to prevent jamming.
Material properties and their impact on silo feed
Proper design begins with assessing bulk material properties. Decisive factors are flow behavior, particle shape, particle size distribution, moisture, temperature, and abrasiveness. Tools such as hydraulic wedge splitters often produce cubic, low-crack chunks with moderate fines—favorable for gravity feeding and belt conveyors. Concrete demolition shears effectively separate reinforcement, making the bulk material rebar-free and conveyable; at the same time, fines are generated that can promote dust and bridging. In that case, dust-tight transfers, larger hopper openings, flow-aid activators, and—if necessary—pre-screening help.
Particle shape and size distribution
Rounded, uniform materials flow more easily than platy, elongated mixes. A broad size spectrum reduces segregation but can increase the risk of wedging. Targeted pre-crushing and sorting support stable silo feed.
Moisture and fines content
Elevated moisture and high fines promote build-up. Countermeasures include steep hopper angles, smooth liners, vibration or air fluidization systems, and heated components in freezing conditions.
Avoiding flow disturbances: From hopper to mass flow
Typical disturbances are bridging, ratholing, and segregation. The goal is preferably mass flow instead of core flow. Contributing measures include:
- optimized hopper geometries with sufficiently large outlets,
- low-adhesion, wear-resistant liners,
- metered vibration or hammering systems, air cannons, fluidization for fine powders,
- smooth, centered filling and controlled drop heights,
- coordinated start-up and shutdown of conveyors to avoid plug formation.
Dust, occupational safety, and environmental protection in silo feed
Dust emissions arise primarily at transfer points and during free fall. Enclosures, dust filters, loading spouts, and low drop heights provide relief. In explosive dust atmospheres, appropriate technical and organizational measures must be assessed. Notes on labeling requirements and zone classification are to be understood generally and do not replace a case-specific assessment. Additionally, noise reduction measures, fall protection at silo tops, and clear exclusion zones should be considered.
Instrumentation and automation
Level indicators, pressure probes, radar, and load cells secure process control. Conveying flow monitoring, standstill, and blockage detection protect equipment. Coordinated control links receiving, pre-screening, metering, conveying, and dust extraction. In tunnel construction or special deconstruction, remotely operated sequences support safety—especially when feeding and crushing take place in separate locations.
Silo feed in the context of application areas
Concrete demolition and special deconstruction
Reinforced concrete is opened with concrete demolition shears, reinforcement is separated, and the concrete debris is brought to suitable piece sizes. For silo feed this means reduced metal content and conveyable chunks. Fines from crushing require effective dust extraction and, if necessary, pre-screening before the silo.
Strip-out and cutting
Heterogeneous material streams arise during strip-out. Clean separation before silo charging stabilizes the material flow. Cutting work on steel components is handled separately; mineral fractions are routed in a defined manner into silos for intermediate storage or dosing into processing units.
Rock excavation and tunnel construction
During rock removal, hydraulic wedge splitters produce large blocks with low fines generation. For silo feed, pre-crushing or screening is often placed upstream so that bucket elevators and hoppers remain feedable. In rock demolition and tunnel construction, low-dust transfers, pressure-shock-resistant filters, and redundant level switches play a central role.
Natural stone extraction
In quarries, silo feed is part of processing: coarse crushing, screening, intermediate storage in the silo, metering to subsequent stages. Particle shape and edge length from splitting processes facilitate controlled loading onto belt conveyors and bucket elevators.
Special operations
In sensitive areas with tight logistics (e.g., inner-city, on existing slabs), compact, low-dust feeding concepts with low dead weight are preferred. Mobile hoppers, closable loading points, and flexible metering devices ensure silo feed without overloading load-bearing structures.
Selection criteria for a suitable silo feed
- Throughput range and load spectrum (continuous/partial, peak flows)
- Particle size distribution, particle shape, density, moisture, abrasiveness
- Conveying distance, height differences, installation space, mobility needs
- Dust and noise emissions, dust extraction requirements
- Required dosing accuracy and controllability
- Safety, accessibility, cleaning, maintenance
- Weather influences and temperature ranges
- Explosion protection assessment for dusty, ignitable mixtures (general, not case-specific)
- Interfaces to upstream and downstream processes (crushing, screening, processing)
Operation, servicing, and maintenance
Regular inspections of chutes, conveyors, seals, and filters prevent disturbances. Pay attention to liners in highly stressed zones, adjustment of metering devices, and function checks of level indicators. Cleaning and empty runs prevent material build-up. In freezing conditions, minimize moisture ingress and use heating where necessary. Shut-off devices must be secured against unauthorized operation; work on the silo feed is carried out with systems isolated, depressurized, and lockout-secured.
Interfaces with hydraulic tools and power units
The quality of silo feed begins at the point of material generation. Early separation of reinforcement—e.g., by concrete demolition shears—and defined piece sizes achieved with hydraulic wedge splitters reduce disturbances in hoppers, transfers, and conveyors. Even feeding, mono-material streams, and matched throughput rates stabilize the entire process from crushing to silo filling.
Example process chains for silo feed
- Material generation by demolition or splitting; coarse separation (e.g., reinforcement, wood, plastics).
- Pre-crushing and shaping of chunks; optional screening to remove fine fractions.
- Metered loading onto belt or chain conveyors; dust extraction at transfer points.
- Vertical transport by bucket elevator or screw; controlled entry into the silo.
- Level monitoring, pressure relief, and filter operation; mass flow via appropriate hopper geometry.
- Controlled discharge from the silo to further processing or outbound transport.
Planning notes for a robust silo feed
Early trials with representative material samples, conservative sizing of outlet openings, maintenance-friendly accessibility, and modular expandability increase operational reliability. Process data such as throughput, moisture, and fines content should be continuously evaluated and control logic adjusted accordingly. This keeps silo feed stable and reliable even with varying material from demolition, deconstruction, rock, and natural stone processing.