What is a Rotary Airlock?
Rotary airlocks can go by many names: rotary locks, rotary valves, rotary feeders, or even just “airlock.” But regardless of what they’re called, they all transfer dry, free-flowing bulk solids like powders, granules, pellets, nuggets, dust, shavings, cuttings, and crystals from a bin, silo, hopper, cyclone, or receiver through a pneumatic conveying system to an adjacent operation in the manufacturing process.
Venturi’s, knife gates, butterfly valves, rotary valves, and double dump valves are other components that can also be considered airlocks. The key is that they are all precision built to dispense material at a controlled rate within the pneumatic system without losing pressure.
How Does a Rotary Airlock Work?
A rotary airlock is made from several components, typically an outer metal housing, multi-vane rotor and shaft, endplates, a drive, shaft packing seals, and bearings.
When the airlock is turned on, the vanes rotate in the housing, much like a revolving door. And like a revolving door, its purpose is to facilitate the rapid movement of people (materials) in a controlled manner while preventing cold air (pressure loss) from entering the building (system).
The space between the rotating vanes (or doors in the case of the revolving door) is known as the rotor pocket. This is where the material that comes in from the opening at the top of the housing goes and stays before being pushed out through the airlock’s lower opening, as it continues through the pneumatic lines.
Because the clearance between the vanes and housing is so tight, it limits the loss of pressure throughout the system, which is especially important since the pressures between bin, silos, and hoppers tend to be different than those found in the adjacent operation. This is why airlocks must be placed either at the beginning of a pressure system or at the end of a vacuum system.
Rotary Feeders vs Rotary Airlock Feeders
While all rotary airlocks prevent pressure loss in their systems, not all rotary feeders are in fact, airlocks. Some rotary feeders lack the valve necessary to maintain the air pressure differentials between two different atmospheres and instead function solely as a device to control the transfer of bulk solids from one chamber to another. This is why it’s important to pay special attention to the type of rotary feeder you’re buying to ensure it functions properly within your pneumatic conveying system.
Though relatively simple devices, rotary airlocks are integral to the operation of pneumatic conveyance systems and have been used in multiple industries. They prove integral in agricultural industries where they can be used as pollution control devices for processing wood, paper, grain, food, tobacco, rubber, textile, and paint products. They are also used within the industrial industry, helping to regulate the movement of food, chemicals, pharmaceuticals, plastics, sanitation, and abrasive materials.
As you can see, rotary airlocks, or airlocks, while being fairly simple devices, are an important part of any pneumatic conveyance system. They help move materials throughout the system without losing pressure and balancing the various atmospheres throughout. They can be used in a variety of industries, from agricultural to industrial, and have the ability to move almost any free-flowing bulk solid available.
If you need help in selecting the right airlocks for your pneumatic conveying system, it’s best to talk with an expert to ensure that you get the correct product for your needs.
At Progressive Products, we won’t sell you anything you don’t need – contact us today to find the right solution for you.
Progressive Products, Inc is a full service provider of pneumatic conveying components specializing in abrasion resistant products such as ceramic backed fittings and wear resistant hoppers, chutes, cyclones, and target boxes.
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