By Alexander Franklin, Director – Ranheat Engineering Ltd
In any modern biomass boiler or industrial wood burner system, the humble rotary valve plays a crucial role. It looks like a simple component, but in reality, it’s a finely tuned part of the machine that controls air, fuel, safety, and performance.
At Ranheat, we’ve been manufacturing our own rotary valves in Northampton for over 25 years. Here’s what we’ve learned—and what you need to know—about selecting and using rotary valves in your biomass system.
A rotary valve is typically used when pneumatically conveying wood dust or biomass fuel from storage to a burner, stoker, or transfer duct.
It serves two critical functions:
Airlock – It holds back the positive or negative pressure between silo and ductwork.
Fuel dosing – It delivers a steady, controllable amount of material into the airstream or feed system.
Without a rotary valve, you’d risk:
Drawing air from the silo (disrupting combustion control)
Dumping too much fuel into the duct (leading to blockages)
Exposure to burn-back from the fire into the fuel store
The correct rotary valve depends on:
Airflow velocity (determines suspension and transport in ducts)
Particle size (must fit between the valve’s vanes)
Bulk density of material (e.g. fluffy shavings vs dense chips)
Desired feed rate (kg/hr throughput)
For light materials like wood shavings, lower air velocity is needed. Dense, wet chips require more power and tighter control. Our RV300 series rotary valves are built with this variability in mind.
Rotary valves use either:
Cast iron vanes (for durability with abrasive material)
Nitrile rubber blades (for dust sealing, common in wood systems)
Ranheat’s default RV300 valves use nitrile paddles. They need to be replaced every 12 months in typical 40-hour/week industrial usage. This is essential for maintaining:
Air sealing
Pressure control
Compliance with ATEX safety standards
Wood is chaotic. No two chip piles are the same. That’s why:
We recommend 25–30 mm max chip size for RV300s
Some customers succeed with larger screen sizes (up to 50 mm)
Others have issues even with 25 mm if fuel is stringy or sticky
Long thin strands, straw, or moist chips can jam the valve or cause build-up. When in doubt—reduce your chip screen size, or consult us.
Many rotary valves on the market are generic. Ours are engineered specifically for biomass boiler systems, with focus on:
Pressure control (for stoker isolation)
Airflow regulation (especially in negative pressure systems)
Preventing burn-back (stopping fire from creeping back into feed system)
We’ve also supplied variants for food-grade, pharmaceutical, and ATEX-rated environments—each with different seals, bearings, and materials.
Speed – Faster rotation = more throughput (not recommended with rubber blades)
Diameter – Wider rotor allows larger volume per revolution
Length – Longer vanes = more material per rotation
In large systems, we may combine diameter and length to hit required throughput while maintaining seal integrity.
Rotary valves are typically mounted under:
Dust extraction bag filters
Cyclones
Chipper-fed silos
Filter design and duct pressure affect how well the valve performs. For large extraction setups (3–8 bag filters or more), our larger RV units are ideal.
We also support systems where screw conveyors feed into rotary valves, which then meter material into stokers or pneumatic ducts.
For explosive dusts, food production, and pharmaceutical applications, we offer:
Food-grade blades and seals
ATEX-certified housings and motors
Ingress-rated bearings and explosion-resistant bodies
These options are custom-configured based on application—so it’s always best to speak to us if you’re unsure.
Rotary valves may be small—but they can make or break your biomass system. From:
Burn-back prevention
Fuel delivery and control
Air management
System safety
…they’re a critical link in the chain.
If you’re planning or maintaining a biomass boiler or wood burner, and need advice on rotary valves—talk to the manufacturer, not just the catalogue.
📞 01604 750005
✉️ [email protected]
🌐 www.ranheat.com
