Silo installations and bulk storage for powder and granulate: complete guide

Silo installations and bulk storage for powder and granulate — definition: A silo installation is an integrated system for storing, conditioning and controlled discharge of bulk goods in powder or granulate form. The installation comprises at minimum a silo tank (steel or stainless steel), a discharge system (rotary valve, screw feeder or pneumatic), level measurement and structural support. For industrial applications in food, chemistry, pharma and the battery industry, HECHT supplies complete silo installations from 1 m³ to >500 m³, including engineering, assembly and commissioning.

Key points

Silo type selection: steel silos (painted or galvanised) for dry, non-aggressive bulk goods in outdoor placement; stainless steel silos (304 or 316L) for food ingredients, pharma, chemically aggressive products; polyester/GRP silos for corrosive substances; concrete silos for large volumes (grain, cement, limestone) — material choice determined by product, cleaning requirements and environmental class
Silo sizing parameters: fill weight (ton/m³), bulk density, flow character (free-flowing, cohesive, thixotropic), bridging tendency, maximum storage duration, temperature and moisture sensitivity, ATEX classification of the product dust; fill volume = (batch interval × consumption) × safety margin 1.2–1.5; cone angle: free-flowing product ≥30°; cohesive ≥45°, sometimes mass-flow design required
Silo accessories: level measurement (radar, ultrasonic, load cells), air filter (HEPA or bag filter on top for dust emission during pneumatic filling), moisture control flap, cone heating/cooling, ATEX earth connection, overpressure protection (explosion safety flap or suppression system), inspection hatch with safety catch
Process integration: silo coupling to receiving (big bag station, pneumatic transport, tanker truck discharge) and to production (dosing unit, mixer, reactor via rotary valve or screw feeder); gravimetric or volumetric dosing; automation via PLC/SCADA with integrated alarms (empty, full, bridging)
HECHT silo park experience: 500+ silo installations delivered in the Benelux and surrounding countries; sectors: pharma, food, chemistry, battery industry, construction materials; in-house engineering, prefabrication and assembly teams; FAT and SAT included

HECHT silo installations: Test & Trial Centre in Pörnbach, silo installations bulk storage powder granulate steel silos stainless steel engineering and silo park bulk storage food pharma chemistry complete engineering assembly.

FAQ — Silo installations and bulk storage

How do I calculate the required silo capacity for my production process?

Silo capacity calculation: step-by-step method. (1) Determine consumption: daily or weekly raw material consumption in tons/day; (2) Determine supply frequency: delivery by tanker truck (20–25 tons), big bag (500–1500 kg), or daily small deliveries; (3) Target stock buffer: at least 1 full delivery as reserve + safety margin; (4) Net volume calculation: gross tonnage / bulk density (ton/m³) = m³ net; (5) Calculate gross silo volume: net / fill degree (max 85–90% for powder = space for filter, dust cloud) = m³ gross; (6) Choose a standard size or custom design. Example: consumption 5 tons/day, weekly delivery 20 tons, bulk density 0.6 ton/m³, buffer 1 delivery = 20 tons / 0.6 = 33 m³ net / 0.85 = ~39 m³ gross → rounded to 40 or 50 m³ standard silo. HECHT provides silo capacity calculation as a free engineering service for customers.

What are the GMP requirements for pharmaceutical silos?

GMP requirements for pharmaceutical silos (EU GMP Part II / ICH Q7): (1) Material: 316L stainless steel, Ra ≤1.6µm internal (preferably ≤0.8µm for API contact); FDA-compliant seals (PTFE, food-grade EPDM); (2) Cleanability: inspection hatch >600mm diameter for manual inspection; spray nozzles for WIP/CIP; drain connection at the lowest point; (3) Level measurement: without product contact (radar or ultrasonic) or hygienic (membrane pressure sensor); (4) Ventilation: HEPA filter on air inlet/outlet, integrity testable; (5) IQ/OQ/PQ: installation qualification (IQ), operational qualification (OQ) including calibration certificates, process qualification (PQ) including cleaning validation; (6) Documentation: material certificates (EN 10204 3.1), welding certificates, pressure test. HECHT supplies pharmaceutical silos including a complete qualification package.

Which discharge systems are suitable for a silo with cohesive or poorly flowing powder?

Discharge systems for cohesive powder silos: cohesive or poorly flowing powder (e.g. silica, talc, clay powder, sugar powder) requires active discharge assistance to prevent bridging and ratholing. Options: (1) Fluidisation plates (air cushions in the cone): air injection temporarily fluidises the powder — cheap, effective for lightly cohesive material; (2) Vibrators (vibration motors on the cone or walls): mechanical shock breaks the bridge — effective but can cause compaction with prolonged use; (3) Mass-flow silo (steep cone >70°, smooth internal surface): flows homogeneously without bridging — more expensive but most reliable; (4) Discharge cone / discharge bridge: combined system of cone + rotating discharge cone centrally in the material; (5) Pneumatic assist dosing: air injection nozzles at multiple points. HECHT designs cone and silo profiles based on Jenike shear-cell analysis for worst-case discharge behaviour.

Author: Joost van Velzen, Managing Director Hecht Technology B.V.

Hecht Technology: storage solutions for bulk goods

In addition to silo installations, Hecht Technology supplies pressure vessels and storage tanks for smaller to medium storage volumes of powders and granulates, including GMP and ATEX versions. For process integration between storage and processing, our systems offer the same hygienic connection standards as our filling and dosing installations.

Our products

Pressure vessels and storage tanks