Rotary valves for powder processing: operation, types and applications 2026
Anyone transporting powders, granulates or pellets via pneumatic systems will sooner or later encounter the dosing gate — also known as a rotary valve, rotary airlock or rotating valve. This compact device plays a crucial role in every powder processing installation: it provides controlled transfer of bulk goods between spaces of different pressure, without losing the airflow.
For process engineers and production managers in pharma, fine chemicals, food and battery production, choosing the right dosing gate directly affects process stability, production loss and installation safety.
How does a dosing gate work?
A dosing gate consists of a rotor with cells (vanes) that rotates within a cylindrical housing. The principle is simple but effective:
- Filling — material drops through the inlet into the rotor's cells
- Transport — the rotor turns and carries the material to the outlet
- Discharge — the material drops or is blown into the receiving system
Rotation speed determines dosing accuracy: slower = less material per unit of time. This makes the dosing gate suitable for both continuous processes and precise batch dosing.
Because the rotor seals off the space between the high- and low-pressure sides, the pressure difference remains intact. This is essential in pneumatic transport, where the transport air would otherwise escape via the material stream.
Types of dosing gates
Not every dosing gate is suitable for every application. The main variants:
Standard dosing gate (open rotor)
For dry, free-flowing materials without high hygiene requirements. Suitable for granulates, pellets and non-sticky powders in the chemical industry.
GMP dosing gate (hygienic design)
Fully cleanable (CIP/SIP), polished surfaces, no dead zones. Required for pharma, food and nutraceuticals. Complies with FDA and EHEDG standards.
ATEX dosing gate
For explosion-sensitive powders (St1–St3) in zones 20, 21 or 22. Fitted with an explosion-proof motor, grounding and spark-free materials. Mandatory for flammable powders such as fine metal dust, pigments or certain food products.
Containment dosing gate (closed system)
For products with a low exposure limit (OEL < 1 µg/m³). Equipped with a mechanical seal to fully prevent dust emission. Applicable to APIs, cytostatics and hormones.
High-temperature dosing gate
For hot gases, drying processes or high-temperature pneumatic transport. Housing and rotor are made of heat-resistant steel.
Applications by sector
Pharma and API production: Dosing gates are used for transferring active substances between dryer, mill and packaging. Containment versions with SMEPAC validation are standard for OEB 3–5 products.
Fine chemicals and ATEX environments: Pigments, catalysts and fine chemicals require ATEX compliance. The dosing gate acts as a pressure-resistant transition in the pneumatic transport system.
Food and nutraceuticals: Sugars, proteins, herbs and vitamins are hygienically transferred via GMP dosing gates with CIP capability. The installation complies with EHEDG and FDA standards.
Battery production: Lithium salts (LiPF6) and cathode material (NMC, LFP) are moisture- and oxygen-sensitive. The dosing gate is fitted with an inert gas seal and ATEX Zone 21 certification.
Plastics and polymer processing: Granulates and pellets are precisely dosed into extruders and mixing installations via dosing gates, with minimal particle damage.
What to consider when choosing a dosing gate?
Several parameters play a role in selecting a dosing gate: bulk density and flow properties of the material, desired throughput capacity (kg/h or m³/h), pressure difference across the gate (bar), ATEX requirement (zone and dust class), hygienic design (CIP/SIP), wear resistance for abrasive material and the required containment level (OEL class).
An incorrectly chosen dosing gate leads to wear, leakage, product loss or — in the worst case — a safety incident. Hecht Technology always advises based on product analysis and process parameters.
Hecht Technology: integrated dosing gate solutions
Hecht Technology supplies and integrates dosing gates as part of a complete powder handling system. From pneumatic transport to containment filtration: the dosing gate is matched to the product, the pressure difference and the safety requirements of your installation.
More information about dosing gates and rotary valves is available at hecht-technology.nl and hecht.eu.
Conclusion
A dosing gate is an indispensable link in every powder processing installation with pneumatic transport. The right version — GMP, ATEX or containment — determines the safety, accuracy and cleanability of your process. Choose based on product characteristics and process parameters, not on price alone.
Want to know more? Visit hecht-technology.nl or get in touch directly.