Introduction — What a rotary valve is and when to use it
A rotary valve is a process component used for handling powders and granules: the lobe rotor transfers product from one point to another while controlling the flow rate. In pharmaceutical lines it is used in stages such as silo/IBC discharge, feeding of mills and mixers, pneumatic conveying, feeding of tablet presses, sachet machines, capsule fillers, and other packaging machines.
When to use it:
• For controlled discharge (gravimetric or assisted by pneumatic conveying) of powders/granules.
• For repeatable feeding, ensuring rotor speed control and stable product flow.
In the pharmaceutical industry, selection requires attention to cleanability, sanitary design and documentation (cGMP), compliant materials and finishes (FDA, USP Class VI), quick disassembly for cleaning, and the possibility of CIP/SIP where applicable.
How it works — principles (rotor, sealing, flow rate)
The valve consists of a body with an inlet and outlet, and a rotor with cavities (pockets). The product, by gravity, fills the pockets on the upper side and is discharged at the bottom as the rotor turns.
Key principles:
Flow rate: proportional to the volume per revolution (pocket geometry) × rotation speed.
Cleaning and disassembly: in pharma applications, sanitary and fully cleanable designs are essential to avoid dead zones and to enable easy cleaning/inspection.
Materials and surface finish:
• AISI 316L (pharma standard) with electropolishing; typical roughness Ra ≤ 0.8 μm (many applications require Ra ≤ 0.5/0.4 μm).
• Hastelloy (C-22/C-276) for more corrosive environments.
• Rotors in 316L or engineered polymers (e.g., PEEK) to reduce friction/adhesion; seals in FDA/USP Class VI–compliant materials (PTFE, EPDM, FKM, silicone).
Selection criteria — from powder to process
To specify a valve correctly, consider product properties and process conditions:
Particle size & morphology
• Fine cohesive powders (e.g., micronized API) pack/adhere: prioritize polished surfaces, rounded rotors, optional anti-stick coatings, and flow aids on the hopper.
• Larger, free-flowing granules: focus on volumetric capacity.
Hygroscopicity and static electricity
• Hygroscopic materials tend to adhere; evaluate environmental control.
• Electrostatic charges require appropriate grounding and sometimes antistatic materials.
Abrasiveness
• Hard particles require robust materials (316L with treatments/hardness, or Hastelloy) and proper tolerances and seals to prevent premature wear.
Bulk density and required flow rate
• Size the valve diameter according to the required product throughput.
ATEX / dust explosion risk
• Identify area classification and require execution with components certified for that zone.
Cleaning and validation (cGMP)
• Need for quick disassembly and/or CIP/SIP; material traceability, certifications (FDA/USP), IQ/OQ and documentation.
Mechanical interfaces
• Sanitary connections (Tri-Clamp, compensators, BFM® connectors/sleeves), spigots, flanges, etc.
Sanitary and compliance requirements
In the pharmaceutical industry, rotary valves must comply with cGMP and applicable regulations, including:
• Contact materials: AISI 316L as standard; gaskets/seals compliant with FDA (21 CFR) and, when required, USP Class VI; Hastelloy for higher corrosion.
• Surface finish: Ra ≤ 0.8 μm (common) or better according to retention/cleaning risk. Electropolishing recommended.
• Sanitary design: continuous surfaces, internal radiusing, no exposed crevices/threads in the product zone, quick removal of rotor/housing.
• Cleaning: compatibility with CIP/SIP where applicable (geometries and seals must support it) or tool-less disassembly for validated manual cleaning.
• Documentation: DQ/IQ/OQ, material certificates, full traceability, cleaning/maintenance manuals, and spare parts list.
• Safety: ATEX/zone compliance for explosive powders, grounding, and mechanical protections.
• Food contact: where nutraceutical/food interfaces exist, compliance with EU Reg. 1935/2004.
Integration in the line — typical connections and layouts
With pneumatic conveying:
When horizontal feeding is required due to height constraints, the valve with rotor discharges directly into the pipeline or a booster hopper connected to the pneumatic conveying system, optimizing available space.
For gravity feed:
With silos/IBCs, mills, mixers, tablet presses, and discharge stations.
• In IBC/silo/sack tipper/Big Bag discharge, the valve acts as a feeder. Pair with bin activators, vibrators, or fluidizing cones for cohesive powders.
• When feeding mills/mixers or other machines: the flow becomes stable and the valve helps break potential product bridging.
• Upstream of tablet presses/capsule fillers: if fine dosing is needed, consider solutions like Rotodoser (microdosing) with speed control and optionally connected to a check-weighing system.
Automation & control
• Variable frequency drive (VFD) for flow regulation.
• Rotation/torque sensors for protection and diagnostics.
• Interlocks with upstream/downstream equipment (pressure switches, level sensors).
• Product recipes (RPM, setpoints, permissives).
Common problems and how to solve them
Packing/bridging in the hopper
Causes: cohesive powder, humidity, low energy in hopper.
Solutions: flow aids (vibrator, massager), proper hopper angle, anti-stick coatings, dry air purge, rounded rotor/paddles.
Abrasion and wear
Causes: hard particles; improper clearances.
Solutions: resistant materials/treatments (high-hardness 316L, Hastelloy), correct clearances, replaceable tips (e.g., PTFE) where applicable.
Loss of airlock / air leakage
Causes: rotor/seal wear; excessive clearance.
Solutions: preventive maintenance, flexible tips, check ΔP and hopper venting.
Product degradation / fines generation
Causes: aggressive blades; high RPM.
Solutions: rounded rotor, lower RPM, greater volume per rotation (same throughput at lower speed).
Carry-over / retention
Causes: sharp edges; poor finish.
Solutions: polishing/electropolishing, radiused edges, sanitary design without dead zones.
Practical cases (illustrative examples)
Case 1 — Stable feeding of a tablet press (API + excipient)
Challenge: sensitive, partially cohesive blend caused variability in tablet mass.
Solution: sanitary rotary valve with rounded rotor, Ra ≤ 0.5 μm, VFD control, and air bypass to stabilize hopper pressure.
Result: reduced feeding variability, improved tablet uniformity, and less rework.
Case 2 — Blow-through pneumatic conveying with hygroscopic granule
Challenge: build-up at outlet with drop-through configuration and moisture uptake in hopper.
Solution: switch to blow-through, dry air purge at loading area, USP Class VI seals compatible with SIP.
Result: elimination of buildup, fewer cleaning stops, and better flowability retention.
Comparative table — materials & seals (technical summary)
| Contact Element | Typical Options | When to Prefer It | Pharma Notes |
|---|
| Body/covers | AISI 316L | Pharma standard | Electropolished; Ra ≤ 0.8/0.5/0.4 µm depending on risk |
| Body/covers | Hastelloy C-22/C-276 | Aggressive/corrosive environment | Higher cost; evaluate only if needed |
| Rotor | Polished 316L | Versatile and robust | Lower adhesion with high polish |
| Rotor | PEEK (engineered polymer) | Reduces friction/adhesion | Check thermal/SIP compatibility |
| Tips/seals | PTFE (FDA/USP VI) | Low friction, chemical inertness | Optional spring-loaded lip versions |
| Seal | EPDM (FDA/USP VI) | Water/alkaline CIP | Check compatibility with solvents/aromas |
| Seal | FKM/Viton® (FDA/USP VI) | Solvents/oils | Temperature limits by grade |
| Seal | Silicone (FDA/USP VI) | Broad compatibility | Good thermal range; check solvent resistance |
Note: final selection depends on product, cleaning method, temperature, ΔP, CIP/SIP, and validation requirements.
Technical checklist for RFQ (for gated PDF)
Use this checklist to request a targeted technical proposal:
Product (powder/granule)
• Name/composition (indicate API/excipients that affect compatibility)
• Particle size distribution (D10/D50/D90) and bulk density
• Cohesion/hygroscopicity (e.g., angle of repose, compressibility index)
• Abrasiveness and degradation sensitivity
• Operating temperature/humidity
Process
• Valve function: airlock, feeder, or doser (microdosing?)
• Min/max flow rate (kg/h) and required stability
• Position (drop-through / blow-through), available space, orientation
• ΔP between upstream/downstream and operating pressure/temperature
• Upstream/downstream equipment: silo/IBC, mixer, mill, press, pneumatic conveying (phase, airflow)
Mechanical & sanitary execution
• Body/rotor materials (316L, Hastelloy, PEEK rotor?)
• Required internal finish (target Ra) and electropolishing
• Gaskets/seals (PTFE, EPDM, FKM, silicone; require FDA/USP VI)
• Quick-release/cantilever design; CIP/SIP (yes/no)
• Connections (Tri-Clamp, SMS, BFM®/sleeve), radius requirements, no crevices
Automation & control
• RPM range; motor + VFD; sensors (speed/torque)
• Interlocks and safety permissives
• Dosing accuracy/repeatability (if in closed loop)
Documentation & validation
• Material and seal certificates (FDA, USP VI)
• DQ/IQ/OQ, FAT/SAT, cleaning/maintenance manuals
• Critical spare parts list (seals, tips, rotor)
Technical FAQ
1) Can a rotary valve dose accurately?
Yes, for volumetric dosing where throughput depends on volume per revolution and RPM. For higher precision/repeatability, use closed-loop control (weighing) or dedicated microdosing solutions (e.g., Rotodoser).
2) How to choose between drop-through and blow-through?
Blow-through is preferable when downstream pneumatic conveying is present and when there is risk of buildup/moisture at discharge. Drop-through is simple and robust for gravity feeding.
3) Is CIP/SIP possible?
It depends on the design. Some sanitary executions support CIP/SIP; others use validated quick-disassembly. Specify this in the RFQ.
4) What determines the surface finish (Ra)?
Retention risk and cleaning method. Cohesive products and manual cleaning require lower Ra (≤ 0.5/0.4 μm). Electropolishing helps.
5) How to avoid particle degradation?
Use rounded rotor, lower RPM, and larger volume per revolution; minimize aggressive clearances.
6) Which seals should I choose?
Depends on chemistry/temperature/CIP. PTFE is inert and low-friction; EPDM/FKM/silicone vary depending on solvents and temperature. Require FDA/USP VI.
7) Is the valve ATEX compliant?
Yes, when specified and built for the relevant zone. Include area classification in the RFQ and ensure grounding and suitable components.
8) When to consider Hastelloy?
Only when there is significant corrosion risk making 316L unsuitable — evaluate cost/benefit.
Call-to-Action
Want to validate the application with your product?
→ Request an In-House Test / Demo Unit (fill out the technical form).
Suggested internal links on the page: Rotovalve (feeding/airlock), Rotodoser (microdosing), Test Room.
(Visual Attachment) Suggested diagrams
Prepare two simple diagrams (clean lines, clear legend):
Drop-through: hopper → rotary valve (rotor cross-section) → gravity discharge; flow arrows; hopper vent indication.
Blow-through: hopper → valve discharging directly into pneumatic pipeline; air/product flow arrows; ΔP indication.
Best practices for installation & maintenance
• Allow frontal space for rotor extraction (in cantilever models) and inspection access.
• Insert bypass/vent to stabilize hopper pressure.
• Ground all sections to avoid electrostatic charges.
• Maintenance plan with periodic check of clearances, seals, and rotor wear.
• Validated cleaning procedures with steps and post-reassembly checks.
• Minimum spare kit: seals set, tips (if applicable), and rotor (if critical for uptime).
