Silo Scraper Systems

Let production continue without interruption to raw material flow.

Powder, granular or mixed raw materials can bridge at the silo outlet due to moisture, static electricity, compaction, density difference and surface adhesion. The silo scraper system mechanically agitates the caked material, supporting continuity of feeding in injection, extrusion and compounding processes.

Key message: Inconsistent raw material flow affects not only the feeding stage but the stability of the entire production line. The silo scraper system helps flow continue without interruption.

Let's Determine the Right Solution for Your Silo

Why Does Raw Material Flow Stop?

Material inside a silo does not always flow downward freely and uniformly. Fine-grained, moisture-retaining, sticky or raw materials that compact over time can form stable structures at the silo outlet. As a result, feeding can decrease, become irregular, or stop completely.

• Bridging — the material forms a load-bearing arch over the silo outlet, stopping the flow.
• Rat-holing — only the material in the center flows; stagnant zones remain along the silo walls.
• Wall sticking — fine, moist particles adhere to the surface, causing buildup and residue.
• Compaction and caking — residence time, pressure, moisture and static electricity reduce the flowability of the material.

What Is a Silo Scraper?

A silo scraper is a mechanical flow-assist system integrated at the outlet of a silo or bunker. Low-speed scraper blades provide controlled movement in the zone where bridging occurs, breaking up caked material, reducing buildup around the walls and helping the raw material advance toward the outlet.

The system can be supplied with a carbon steel or stainless steel body option depending on the application.

PTFE-coated scraper blades and PTFE-spray-coated inner ring

Unlike classic vibration-based solutions, the mechanical blades make direct contact with the material. This allows for quiet, controlled operation without transmitting unnecessary vibration to the silo body.

Which Production Processes Is It Used In?

Injection

It helps deliver powder additives, regrind and low-flowability raw materials to central feeding or dosing systems in a consistent manner. Reducing fluctuation in feeding supports the maintenance of cycle stability.

Extrusion

It contributes to uninterrupted feeding of the extruder with PVC dry blends, calcium-carbonate-containing formulations, and powder or granular raw materials prone to compaction in the silo. This can reduce flow-rate variation and unplanned production stoppages.

Compound

It supports a more balanced delivery of filler, pigment, mineral and additive mixes to the main or side feeders. Consistent feeding is important for preserving the formulation, keeping capacity stable and reducing fluctuations in product quality.

Suitability note: every raw material has different flow behavior. Blade geometry, surface coating, motor power, speed and connection size should be determined according to the properties of the material and the silo structure.

How Does It Work?

• The scraper system activates when the raw material in the silo outlet zone begins to compact or bridge.
• The motor-gearbox or selected drive system moves the scraper blades at low speed and high torque.
• The blades mechanically break the material arch, loosen buildup around the walls and keep the outlet zone open.
• The raw material is delivered more consistently to the screw conveyor, doser, feeder or process machine.

Motor-gearbox and scraper arm structure — real production example

Benefits for Production

• Uninterrupted feeding — reduces the risk of raw material flow stopping or becoming irregular.
• Stable production — helps limit the impact of feeding fluctuations on the process.
• Less manual intervention — reduces the need to manually open silos or bunkers and physically intervene with the material.
• A cleaner silo interior — helps reduce the amount of material that sticks to the walls and remains stagnant.
• Controlled operation — the low-speed mechanical motion does not create unnecessary structural vibration.
• Process-specific design — connection size, blade length, angle, material and coating options can be determined according to the application.

Technical Structure and Options

• Drive system — motor-gearbox, worm gear drive, precision gear drive or pneumatic motor options
• Body material — carbon steel or stainless steel options; determined according to the raw material, corrosion, hygiene and operating conditions
• Surface treatments — PTFE coating, tungsten carbide spraying, ceramic coating or full PTFE coating options
• Blade structure — removable, project-specific angled blades for easy cleaning, maintenance and replacement
• Sealing — air and oil seal combinations to separate the material from the drive unit
• Speed control — adjustable operation according to the application via frequency inverter or pneumatic pressure control
• Connection — special flange and mounting options suited to the silo outlet, butterfly valve, screw conveyor or feeder structure
• Warranty — 12 months from the delivery date; damage arising from misuse, incorrect installation or adjustment, or improper operating conditions is not covered by the warranty

Standard Connection Sizes

Silo scraper systems can be supplied with connection sizes suited to the silo outlet and existing feed line. The standard nominal diameter range is between DN50 and DN800: DN50 • DN100 • DN125 • DN150 • DN200 • DN250 • DN300 • DN350 • DN400 • DN450 • DN500 • DN600 • DN700 • DN800.

Sizing note: the DN value indicates the nominal connection diameter. The final flange size, bolt holes, mounting height and blade geometry are verified based on the technical drawing of the existing silo and feed system. Non-standard sizes can be evaluated on a project basis.

Information Needed to Determine the Right System

• Silo or bunker outlet connection diameter and flange dimensions
• Silo capacity, lower conical section geometry and existing layout
• Name, grain structure, density, moisture and stickiness of the raw material used
• Existing feed system: screw conveyor, doser, butterfly valve or other equipment
• Target feeding capacity and the flow problem experienced
• Silo photographs, technical drawings and connection details, if available
• Hygienic, wear-resistant, corrosive or explosive-atmosphere requirements

Frequently Asked Questions

Is a silo scraper suitable for every raw material?

The system's structure is determined according to the material used. A standard model should not be selected without evaluating moisture, grain size, density, stickiness and abrasiveness.

Can it be retrofitted onto an existing silo?

In most applications, a suitable connection can be designed for the existing silo outlet, butterfly valve, screw conveyor or feeder. Final suitability is verified based on the silo dimensions and layout.

How is it different from vibration-based systems?

Mechanical scraper blades act directly on the bridging zone. This allows controlled flow assistance to be provided without transmitting continuous vibration to the silo body.

Can it be used with sticky materials?

Low-adhesion surface treatments such as PTFE and project-specific blade geometries can be preferred.

Is technical support provided after delivery?

Technical support needed during installation, commissioning, adjustment and use is provided according to the scope of the product and the project.

What is the warranty period?

The silo scraper system is under warranty for 12 months from the delivery date. User-caused damage such as misuse, incorrect installation or adjustment, unauthorized intervention, improper operating conditions, impact, overload and failure to follow maintenance instructions is not covered by the warranty.

Let's evaluate your raw material flow problem together. Share your silo dimensions, the material used and photographs of the existing system; let's determine the right scraper structure for your application.

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