Potato | Potahto? Tomato | Tomahto? Rotary Airlocks, Feeders & Valves

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Craig Rattos



If you are handling materials, there's a good chance you've got a rotary valve in your processing line.

And there are just so many different ways to refer to these valves.  Airlocks, rotary airlocks, rotary feeders, rotary airlock feeders - and more! Very confusing!

Although the job of each of these valves is to transfer bulk materials from storage/holding into a conveying system, there are differences.  They are all basically rotary valves but - with other components added - they can become airlocks or feeders. 

Rotary Airlocks maintain a pressure differential between separately pressured atmospheres.  Feeders transfer materials from one compartment in your process - to another and often at a controlled rate.

So how do you choose?  It completely depends on your application, the demands of your process and the nature of your industry.  

So what's a Rotary Valve?

  • Rotary valves are composed of a shaft, housing, rotor, seals, bearings, end plates and a drive.
  • When combined with other components, rotary valves can become an airlock or feeder - or both!

How do Rotary Airlocks function?

  • Displace bulk solids from one container or atmosphere to another, whilst minimizing the loss of air pressure. 
  • Rotary airlocks function in pneumatic conveying systems by sending materials into the conveying system OR by removing materials from dust collectors or cyclones at the end of a conveying system.
  • High pressure fans or blowers move materials through the system.

How do Rotary Feeders function?

  • Rotary feeders control flow rates of bulk solid material, typically controlling the rate of displacement from a bulk storage vessel to processing equipment that requires a controlled and consistent flow. 

When a rotary valve needs to both function as an airlock and a feeder, they are most often referred to as Rotary Airlock Feeders.  The rotary valve prevents air loss while simultaneously feeding bulk solids into downstream processing equipment.

With tens of thousands of installations throughout the world, the Schenck Process MD Airlock is a highly universal airlock used to meter dry bulk materials under feeding devices, such as bins, hoppers, mixers, screw conveyors and sifters. Providing rugged service, the MD is suitable for use in dilute phase vacuum, pressure or combination vacuum/pressure pneumatic conveying systems. Low mounting height is ideal for space restricted applications. With a low profile and a wide flange width, the MD airlock is able to match drill hole patterns of many competitor’s valves for easy replacement.

  • Versatile airlock can be connected to many different types of storage and conveying devices
  • Square flanged inlet and outlet
  • Highly reliable, rugged design delivers low maintenance service
  • Sealed bearings require no lubrication and provide years of service
  • Available in a wide range of sizes
  • Special options extend service life in challenging applications



The Schenck collection of valves are highly efficient, rugged and reliable and are suitable for vacuum dense phase, dilute phase, and gravity discharge systems. They are precision-crafted at extremely close tolerances to:

  • Eliminate dusting
  • Reduce maintenance costs
  • Avoid process shutdowns

Valve performance depends directly on the material being handled. We’ll help you properly size the correct valve for your applications, and select appropriate housing and rotor options to manage your desired rate and the estimated fill efficiency. Our state-of-the-art pneumatic TestCenter can test your material and prove systems before any steel is cut or equipment is installed. You can count on us to properly size valves and blowers to reduce air leaks, decrease energy costs, and ensure proper convey pressures and rates — guaranteed.

Multi Duty (MD) Valves
A highly universal valve designed for rugged service. Suitable for use in dilute phase vacuum, pressure or combination vacuum/pressure pneumatic conveying systems with a maximum differential pressure of 15 psi. High temperature (up to 450˚ F) and wear resistant designs also available. Flange patterns of many competitive valves can be matched providing easy field replacement. The MD40 through MD260 features a class 40 gray iron housing with 217 Brinell hardness for greater strength and wear resistance.

Round Valve Multi-Duty (RAM)
The Mac Process RAM Valve uses many of the same design features as the MD Valve, but includes round, flanged inlet and outlet connections with 150# drilling. The basic valve is designed for 15 psi differential pressure service and comes complete with a fabricated, machined, eight-vane open end rotor. The RAM is available in six sizes with a broad range of options and accessories to fit most any application including: closed end rotors, adjustable tip rotors, abrasion resistant coatings and elevated temperature service.

Heavy Duty (HD) Valves
Mac Process Heavy Duty Valves are used in pneumatic conveying systems and gravity discharge of filters, cyclones, storage tanks, and as volumetric feeders. HD Valves are available in 8 standard sizes, ranging from .175 CFR to 16.6 CFR. They are available in cast iron construction (HD8x6 through HD24x24) or fabricated carbon steel (HD30x30 and HD36x36). HD Valves are ruggedly built, and offer a practical solution to many general material handling applications.



Have questions?  Need information? 

Just give us a shout.  We're always happy to chat.


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