How to use Industrial Rotary Airlock Valve Feeder Capacity& Motor Power Calculator
- Enter Displacement per revolution (L/rev) and adjust the options as needed.
- Run the tool and inspect its results, evidence and limitations.
- Copy or download the result, then verify it against the actual website, source data or business records.
Try a concrete example
In a pneumatic conveying feeding system for cement powder and grain handling, a 15 L/rev nominal rotary airlock valve is installed beneath a storage silo as an airlock feeder. Designed for 20 RPM rotor speed, 75% volumetric filling efficiency, 0.85 t/m³ bulk density, and 0.35 bar differential pressure between conveying line and hopper, with an open straight vane rotor: calculations indicate an actual volumetric displacement of 13.5 m³/h and mass throughput of 11.48 t/h. Across a 0.15 mm radial rotor-housing clearance under 0.35 bar delta P, seal air leakage is 1.24 Nm³/min. Overcoming granular shearing, packing gland friction, and bearing resistance, shaft brake power is 1.13 kW. Accounting for startup packing surges, a 2.2 kW helical gearmotor (85% drive efficiency, service factor fB >= 1.5) is recommended for continuous, stall-free feeding and reliable airlock isolation.
How to interpret results
Industrial rotary airlock valves (also known as rotary feeders, star valves, or rotary airlocks) serve as critical metering and isolation equipment in positive- and negative-pressure pneumatic conveying networks, dust collector hoppers, and storage silos. Their primary engineering function is to meter bulk solids continuously while maintaining a differential pressure barrier (airlock seal). Mechanically, the valve comprises a cylindrical rotor with multi-vane radial pockets, a cast housing, and bolted endplates. As the rotor turns, material entering the top pockets is carried to the bottom discharge port. Excessive rotational speed generates centrifugal force that impedes gravity pocket filling while accelerating blade tip erosion. Meanwhile, pressure differentials drive parasitic air leakage through radial and axial clearances (0.10 to 0.25 mm), which can disrupt dust collector vacuum or aerate the feed hopper. Correctly balancing rotor displacement, RPM, differential pressure, and motor torque is essential to prevent jamming and excessive air loss.
Frequently asked questions
In positive-pressure dilute-phase pneumatic systems, how do you prevent reverse air leakage through rotary airlocks from bridging the feed hopper?
First, maintain tight machining clearances: radial and axial gaps between rotor blade tips and the housing/endplates must remain within 0.10 to 0.20 mm to prevent high-pressure air blast into the feed hopper. Second, install a rotor vent hopper port: vent upward-returning empty pockets on the ascent side to exhaust trapped compressed air into a dust filter, relieving pocket air pressure before it reaches the feed throat. Third, select closed-pocket shrouded rotors or flexible polyurethane/rubber scraper tips to elongate the labyrinth seal path, eliminating pneumatic hold-up and material bridging in the silo cone.
How do you determine optimal rotor RPM for rotary feeders, and what engineering risks arise from excessive rotational speed?
Economical rotor speeds typically range between 10 and 25 RPM (rarely exceeding 35 RPM). Risks of excessive speed include: First, centrifugal repulsion drops pocket fill efficiency: bulk material falling by gravity cannot keep pace with rapidly passing vane pockets, truncating pocket loading and causing actual throughput to decline. Second, particle jamming trips motor overloads: higher RPM multiplies the shearing frequency of coarse particles against the inlet throat ledge, generating transient stall torque spikes that can snap drive shafts or trip motor breakers. Third, accelerated abrasive wear and leakage: abrasive erosion scales quadratically with linear vane velocity, rapidly blowing out mechanical clearances and destroying airlock isolation within months.
What are the suitable applications for open pocket, closed pocket shrouded, and beveled adjustable scraper rotors?
First, Open Pocket straight vane: open on both axial sides, inexpensive and simple, ideal for free-flowing, non-abrasive dry granules and powders (such as plastic pellets and grains). Second, Closed Pocket shrouded rotor: features solid circular side discs welded or cast onto the vanes, enclosing bulk solids inside pockets and preventing abrasive contact with stationary endplates, recommended for abrasive mineral powders, cement clinker, and fly ash. Third, Beveled Scalloped rotor with adjustable tips: features relieved blade edges fitted with tungsten carbide or polyurethane scraper blades that slice through fibrous solids and allow manual wear compensation, tailored for sticky, cohesive, or fibrous bulk solids.
Why must gearmotor sizing for rotary airlock valves include a generous service factor (fB >= 1.5 to 2.0)?
Rotary airlocks operate against dynamic, non-uniform resistance rather than smooth fluid drag, driven by three major surge factors: First, compacted head-load breakaway torque: tons of static material resting in the overhead silo create a breakaway starting torque 2 to 3 times running torque. Second, particulate pinching and shearing: tramp metal or oversize chunks lodging between rotor tips and the housing throat induce severe transient shear resistance. Third, thermal differential expansion: conveying hot bulk materials (150 to 250°C) causes the rotor core to expand faster than the externally cooled housing, tightening mechanical clearances and increasing friction. Thus, motor sizing requires high-starting-torque induction motors with mechanical torque limiters and fB >= 1.5 to 2.0.