Rotary airlock valves are also called rotary feeders, rotary valves, or just rotary airlocks. Used in both pressure style and vacuum style pneumatic conveying systems, these valves serve as a “lock” to prevent air loss while simultaneously performing vital material handling functions. Though simple, the rotary airlock valve is a critical component to the efficiency of a conveying system. It’s important to remember that not all rotary valves are necessarily rotary airlock valves – but virtually all rotary airlocks are rotary valves.
What Happens Inside a Rotary Airlock Valve
The vanes, or metal blades, of a rotary airlock valve turn (rotate) during operation. As they do, pockets form between them. The material being handled enters the pockets through the inlet port before rotating around inside the valve and then exiting through the outlet port. In an airlock valve, air is sealed (locked) between the inlet and outlet ports. This allows the materials to travel downward through the valve from the inlet to the outlet port while restricting the airflow. Material is moved continuously through the presence of a constant air pressure between the ports. This pressure or vacuum difference must be maintained within the valve for proper function.
A Few Words About the Rotor Assembly
The rotor assembly in a rotary airlock valve consists of a set of blades welded to a rotary shaft. The rotor assembly in a rotary airlock valve is sometimes referred to as a the paddle wheel, impeller, or flipper. A six-vane rotor has six metal blades attached to the shaft, an eight-vane rotor has eight, and so on. A valve with more vanes tends to have greater sealing ability than one with less. As the number of blades increases, however, the size of the pockets between them decreases. Larger pocket size is ideal for processing larger materials or materials that tend to stick or pack together when compressed. Heavier materials and materials that flow quickly are not as greatly affected by the number of vanes and subsequent pocket size. It’s important to talk with a professional to figure out the optimal setup for the specific materials you’ll be handling. Another thing to discuss is whether you will need an open-end or closed-end rotor. In general, open-ended units are better suited for easy-flowing non-abrasive materials and closed-ended setups work best for materials that may have issues with flowing smoothly.
The Effects of Improperly Applied and Worn Airlocks
Airlocks, while simple, are an indispensable part of certain material conveying and processing operations. Using one incorrectly can cause machinery to suffer undue wear and operate less efficiently. It can also lead to increased costs due to extra maintenance and operator working hours. In the worst case, it can cause equipment to break or malfunction to the point that downtime is necessary.
Common Causes of Airlock Valve Wear
Wear-and-tear to the rotor, housing, or both is one of the leading causes of airlock valve failure. Processing abrasive materials causes cumulative damage to the surfaces inside the valve. Surface drag abrasion occurs when materials are trapped between two surfaces moving in different directions. It can also be the result of any kind of surface-on-surface contact where abrasive materials are between the two planes. Pneumatic assisted abrasion occurs when turbulent air, or “blow-by,” develops at the outlet port when using a pneumatic conveying system. This misdirected air can cause significant loss of efficiency and issues with material flow. This wayward air can also carry with it abrasive particles that can cause unnecessary damage to valve components.
Selecting the rotary airlock valve that will help your operations achieve optimum efficiency is highly important, so don’t leave it up to chance. The experts at Streamline Industries can find or fabricate the perfect valve for your needs. They also perform repairs on existing valves, and will give you honest answers about whether repair or replacement is the better option in your situation.