What is a dosing system?

Q: What is the difference between gravimetric and volumetric dosing systems, and which is better for GMP applications?

Gravimetric dosing (LIW — loss-in-weight) continuously measures the weight change of the feeder hopper to calculate instantaneous mass flow rate — achieving RSD <0.5% regardless of powder density variations. Volumetric dosing measures rotations or frequency, which can drift if bulk density fluctuates (common with hygroscopic APIs). For GMP Annex 1 and ICH Q7 applications — especially HPAPI at OEB 4-5 — gravimetric LIW is preferred because it delivers OIML R76-traceable records, supports ALCOA+ data integrity, and is validated per GAMP 5. HECHT's LBK-EC and CFE-K-EC systems include integrated OIML R76 loadcells as standard.

Q: How do ATEX requirements affect dosing system design in pharmaceutical and chemical plants?

ATEX 2014/34/EU requires all electrical components in zone 21 (combustible dust) to be certified category 2D — including dosing motors, sensors, control panels and HMIs. For powder dosing, this means Ex-rated drives (IEC 60079-0), ESD-bonded contact parts (NEN-EN 60079-32, resistance <10⁶ Ω), ATEX-certified loadcell transmitters, and dust-tight IP65/IP67 enclosures. HECHT designs all dosing systems with a zone-indeling P&ID, ATEX equipment schedule and NEN 3140 electrical inspection dossier — directly supporting customer ATEX risk assessment (ARBO directive 1999/92/EG).

Q: What validation documentation is needed for a dosing system in a GMP Annex 1 environment?

A complete dosing system validation package for GMP Annex 1 includes: URS (User Requirements Specification), FDS (Functional Design Specification), FAT (Factory Acceptance Test) and SAT protocols, IQ (Installation Qualification) verifying ATEX compliance, OIML R76 calibration and EHEDG surface finish (Ra ≤0.8 µm), OQ (Operational Qualification) with dosing accuracy tests at min/max throughput (RSD <0.5%), and PQ (Performance Qualification) in production conditions including SMEPAC containment test for OEB dosing. HECHT delivers complete GAMP 5-aligned IQ/OQ/PQ documentation.

Q: What are dosing systems for the food industry?

Dosing systems for the food industry are precision apparatus that measure and deliver exact quantities of powders, granulates, liquids or ingredients into food production processes. They use gravimetric (loss-in-weight, OIML R76 ±0.1% accuracy) or volumetric (screw, rotary valve, vibratory feeder) technology to meet food-safety standards such as EHEDG hygienic design, HACCP and FDA/EU food-contact requirements. HECHT dosing systems handle ingredients ranging from fine powders and spices to granulates and battery-grade materials, with hygienic, easy-to-clean designs suited to food and beverage manufacturing.

Q: What is an ingredient dosing system?

An ingredient dosing system precisely measures and adds individual ingredients (e.g. spices, additives, flavourings, powders) into a food or beverage batch, ensuring consistent recipe accuracy and traceability. HECHT ingredient dosing solutions combine LIW (loss-in-weight) gravimetric dosing with RSD <0.5% repeatability, supporting recipe management, batch traceability and hygienic, tool-free cleaning for frequent ingredient changeovers.

A dosing system delivers a controlled amount of powder or liquid into a process at a set rate. Gravimetric systems weigh the material and are the most accurate. Volumetric systems measure by volume and are simpler and cheaper. Batch dosing fills set quantities; continuous dosing feeds a steady flow.

Key Points

Gravimetric dosing (LIW): OIML R76-certified loadcells ±0.1% accuracy, RSD <0.5% — required for GMP Annex 1 blend uniformity (USP <905>) and ICH Q7 API dispensing
ATEX certification: dosing screw motors (category 2D, zone 21), ESD-safe contact parts (NEN-EN 60079-32), PTFE/RVS 316L construction for REACH-compliant CMR substances
HECHT dosing products: LBK-EC (big bag dosing OEB 1-5, SMEPAC-validated), CFE-K-EC (drum dosing OEB 3-4), screw feeders (EHEDG class I/II for food), vibratory feeders (FSMA, ATEX)
Integration: ISA-88 batch, OPC-UA MES/ERP, GAMP 5 IQ/OQ/PQ, 21 CFR Part 11 audit trail, PAT feedback loop (NIR/Raman inline) for continuous manufacturing (ICH Q13)
TCO benefit: automated LIW dosing reduces giveaway by 1-3% of product value and cuts operator exposure below OEL via closed-loop OEB containment

Explore HECHT's complete dosing portfolio via our powder processing solutions, validate dosing performance at our Test & Trial Centre in Pörnbach, or review pharma-specific dosing and containment systems.

Types of dosing systems: gravimetric vs volumetric compared

Choosing the right dosing principle depends on product behaviour, required accuracy and hygiene demands. The table below compares the most common industrial dosing systems for powders and granulates:

Dosing system	Principle	Typical accuracy	Best suited for
Loss-in-weight (LIW) feeder	Gravimetric	RSD <0.5%	APIs, food additives, continuous processes with fluctuating bulk density
Screw feeder	Volumetric	±1–2%	Free-flowing, density-stable powders
Vibratory feeder	Volumetric	±1–3%	Fragile or abrasive granulates
Rotary valve	Volumetric	±2–5%	High-throughput, dust-tight discharge from silos and filters
Flexible dosing system (FDS)	Gravimetric	±0.1% loadcell	Multi-ingredient batching and frequent recipe changes
Dosing valves	Volumetric	±1–3%	Compact dosing into mixers, reactors and packaging lines

In the food industry, gravimetric loss-in-weight dosing combined with EHEDG-certified contact parts is the standard for allergen-safe, label-compliant production. For potent compounds (OEB 3–5), dosing is integrated into a closed containment system — see our powder processing and transport solutions.

Dosing techniques for powders and granules

The dosing element determines how the product is discharged in a controlled way. The right choice depends on flow behaviour, required throughput and how often you change product.

Screw feeder: suits a wide range of flow properties, from fine powders to granules. Works volumetrically, or gravimetrically when the feeder sits on load cells (loss-in-weight).
Vibratory feeder: moves product evenly and gently; suited to fragile or abrasive granules.
Dosing valve and dosing gate: for batch-wise metering via a controlled opening time or stroke, for example above a mixer, reactor or packaging line.
Vacuum dosing: combines conveying and dosing in one closed step, useful where dust-free operation comes first.

Ingredient dosing systems: macro, minor and micro ingredients

Food and feed plants usually split a recipe into three groups, each with its own dosing approach:

Macro ingredients (such as sugar, flour, starch, milk powder) come from big bags or silos and are dosed with screw feeders or loss-in-weight feeders directly into the mixer.
Minor ingredients (such as salt, cocoa, seasoning blends) are dosed from smaller hoppers or drums, often gain-in-weight into a weighing hopper.
Micro ingredients (vitamins, enzymes, flavourings, premixes) are weighed in small quantities, often at a separate weighing station, and added via a bag dump station.

The more components and recipe changes, the faster an automated batch dosing system with recipe management pays for itself: fewer weighing errors, full lot traceability and shorter changeovers.

Continuous dosing

Continuous dosing delivers a constant mass flow, for example into an extruder, a continuous mixer or a continuous production line. This requires a gravimetric loss-in-weight feeder with feedback control that corrects the throughput in real time.

Dosing difficult powders

Not every powder doses equally well. Poorly flowing, sticky or bridging products cause fluctuations or downtime if the system is not designed for them.

Poor flow: discharge aids such as aeration, vibration or an agitator in the supply hopper.
Bridging: a mass-flow hopper geometry keeps the supply to the dosing element constant.
Sticky powders: smooth surfaces and a suitable screw geometry prevent build-up.
Segregation: short, controlled discharge prevents fractions from separating.

HECHT matches the dosing principle to the actual flow properties, established through product analysis and trials with your own product at the Test & Trial Centre in Pörnbach.

Dust-free and containment dosing

Dosing is a transfer point and therefore a potential source of dust. For pharmaceutical actives or toxic chemicals, HECHT integrates dosing into a closed chain: endless liners, containment filling heads or split butterfly valves on the supply side and vacuum conveying to the process. Containment performance is demonstrated with a SMEPAC measurement; for combustible powders the system is earthed and built ATEX-compliant.

Integration and process control

Recipe management: storage and automatic execution of dosing recipes.
Data logging: every dose is recorded for traceability and validation.
Feedback control: automatic correction based on actual weight values.
Connectivity: link to PLC, MES or ERP for batch reporting.

Batch dosing systems: when do you need them?

A batch dosing system weighs or meters a defined quantity of each ingredient per batch before it goes into a mixer, reactor or packaging line. It is the standard choice when recipes change often, when every batch must be traceable, or when small amounts of additives are added to a large main component.

Gain-in-weight (GIW): ingredients are dosed one after another into a weighing hopper until the target weight is reached. Simple, accurate and suited to recipes with several components.
Loss-in-weight (LIW): the feeder itself is weighed and doses by measuring the weight it loses. Used when a batch must be filled at a controlled rate, or when the same feeder also runs continuously.
Volumetric batch dosing: a screw or rotary valve doses by volume. Lower cost, but only accurate for powders with a stable bulk density.

Chemical weighing and dosing systems

In the chemical industry, weighing and dosing systems often handle toxic, corrosive or combustible powders. That adds three requirements on top of accuracy:

Containment: closed transfer from big bag, drum or sack to the weighing vessel, so operators are not exposed.
ATEX: equipment and weighing electronics suitable for the dust explosion zone (often zone 20, 21 or 22).
Materials: 316L stainless steel or Hastelloy for corrosive products, with seals that resist the chemicals used.

See our dosing systems for powders and granules for HECHT solutions for batch and continuous dosing.

Dosing systems in the food industry

In food production, dosing accuracy directly determines product consistency, label compliance and allergen safety. Typical applications include dosing of spices and seasoning blends, milk and whey powders, functional additives (vitamins, minerals, enzymes), starches and hydrocolloids into mixers, extruders and packaging lines.

Food-grade dosing systems must meet requirements that go beyond accuracy:

Hygienic design: EHEDG class I/II components, crevice-free product contact parts (Ra ≤0.8 µm), tool-free disassembly for wet cleaning and CIP.
Allergen management: quick-change contact parts and validated cleaning procedures prevent cross-contact between allergen and allergen-free runs.
ATEX compliance: many food powders (starch, milk powder, sugar) are combustible dusts — zone 20/21/22 rated equipment is mandatory.
Traceability: batch reporting and lot tracking per FSMA and EU 178/2002.

HECHT dosing systems for the food industry combine EHEDG-certified screw feeders with gravimetric loss-in-weight control (RSD <0.5%), so recipe accuracy is maintained even with fluctuating bulk densities. Test your own product at our Test & Trial Centre in Pörnbach.

Which dosing system is best for the food industry?

For dry food ingredients, a gravimetric loss-in-weight screw feeder with EHEDG-certified contact parts is the standard choice: it holds ±0.5% accuracy despite density variations, supports allergen changeovers via quick-release parts, and meets ATEX requirements for combustible food dusts. Volumetric dosing is acceptable only for free-flowing, density-stable products.

Frequently asked questions (FAQ)

What is a dosing system?
A dosing system meters a set quantity or mass flow of powder, granulate or liquid into a process step such as a mixer, reactor or packaging line.

How does a dosing system work?
It measures the material either by volume (screw, valve or vibratory feeder) or by weight (load cells), and controls the discharge until the set quantity or mass flow is reached.

Why is a dosing system important?
A good dosing system ensures consistent dosages, minimizes product waste, and enhances overall production quality.

What are the types of dosing systems?
Dosing systems vary from gravimetric to volumetric dosing methods, each suitable for specific applications based on accuracy and precision requirements.

How to maintain a dosing system?
Regular maintenance, calibration checks, and component inspections are vital to ensure the dosing system operates accurately and efficiently over time.

What is the difference between gravimetric and volumetric dosing systems, and which is better for GMP applications?

Gravimetric dosing (LIW — loss-in-weight) continuously measures the weight change of the feeder hopper to calculate instantaneous mass flow rate — achieving RSD <0.5% regardless of powder density variations. Volumetric dosing measures rotations or frequency, which can drift if bulk density fluctuates (common with hygroscopic APIs). For GMP Annex 1 and ICH Q7 applications — especially HPAPI at OEB 4-5 — gravimetric LIW is preferred because it delivers OIML R76-traceable records, supports ALCOA+ data integrity, and is validated per GAMP 5. HECHT's LBK-EC and CFE-K-EC systems include integrated OIML R76 loadcells as standard.

How do ATEX requirements affect dosing system design in pharmaceutical and chemical plants?

ATEX 2014/34/EU requires all electrical components in zone 21 (combustible dust) to be certified category 2D — including dosing motors, sensors, control panels and HMIs. For powder dosing, this means Ex-rated drives (IEC 60079-0), ESD-bonded contact parts (NEN-EN 60079-32, resistance <10⁶ Ω), ATEX-certified loadcell transmitters, and dust-tight IP65/IP67 enclosures. HECHT designs all dosing systems with a zone-indeling P&ID, ATEX equipment schedule and NEN 3140 electrical inspection dossier — directly supporting customer ATEX risk assessment (ARBO directive 1999/92/EG).

What validation documentation is needed for a dosing system in a GMP Annex 1 environment?

A complete dosing system validation package for GMP Annex 1 includes: URS (User Requirements Specification), FDS (Functional Design Specification), FAT (Factory Acceptance Test) and SAT protocols, IQ (Installation Qualification) verifying ATEX compliance, OIML R76 calibration and EHEDG surface finish (Ra ≤0.8 µm), OQ (Operational Qualification) with dosing accuracy tests at min/max throughput (RSD <0.5%), and PQ (Performance Qualification) in production conditions including SMEPAC containment test for OEB dosing. HECHT delivers complete GAMP 5-aligned IQ/OQ/PQ documentation.

What are dosing systems for the food industry?

Dosing systems for the food industry are precision apparatus that measure and deliver exact quantities of powders, granulates, liquids or ingredients into food production processes. They use gravimetric (loss-in-weight, OIML R76 ±0.1% accuracy) or volumetric (screw, rotary valve, vibratory feeder) technology to meet food-safety standards such as EHEDG hygienic design, HACCP and FDA/EU food-contact requirements. HECHT dosing systems handle ingredients ranging from fine powders and spices to granulates and battery-grade materials, with hygienic, easy-to-clean designs suited to food and beverage manufacturing.

What is an ingredient dosing system?