Sealing Rotary Airlocks.
Rotary airlocks (sometimes called rotary valves) sit at the bottom of bins and silos to meter solids out into pneumatic conveying systems. The rotor shaft penetrates the housing under positive pressure differential — typically 5 to 15 psig in dilute-phase pneumatic transfer — making it a unique sealing problem.
01The equipment
What an rotary airlocks actually is.
A rotary airlock is a rotor with vanes turning inside a tightly-clearance housing, used to meter bulk solids while maintaining a pressure seal. The rotor shaft penetrates each end of the housing through bearings; sealing both shaft penetrations is critical because the airlock's job is to maintain pressure differential.
02Failure modes
Why sealing this equipment is hard.
- 01
Positive-pressure service across the seal
Unlike most rotary seal applications, an airlock seal must hold against positive process pressure (5 to 15 psig). The 7500 and 7800 are rated for this; lip seals are not.
- 02
Continuous solids flow at the seal face
Solids continuously cycle past the seal face — there's no quiet period. Air-purged contact seals are the standard; outside-mounted (7600-style) designs typically don't fit the airlock geometry.
- 03
Abrasion from product entrained at clearances
Even a tightly-built airlock has small clearances between rotor and housing. Product caught in those clearances acts as an abrasive at the seal face — tungsten faces are recommended for hard products.
- 04
Air-purge management to avoid product blowback
Too much air purge into the airlock interferes with the conveying flow downstream. We tune the air purge to the lowest reliable rate — typically 1 to 2 SCFH on airlock service.
03Recommended series
What we ship for rotary airlocks.
04Industries that use this equipment
Where you'll find rotary airlocks in production.
05Engineering FAQ
What plant engineers ask before specifying.
Rotary Airlocks · sized in 24 hours
Get a sized seal recommendation for your rotary airlocks.
Send shaft size, OEM make and model, and the operating envelope. We respond with a sized series, materials, and pricing — typically within one business day.