Have you ever tried baking a cake without using exact measurements? Some people, like grandmas and professional bakers, can do it using only vibes and intuition. The rest of us will probably get better results by following a recipe.
When your bulk material handling system requires metering or feeding, you need an even greater level of precision to ensure both the quality of your product and a consistent rate of production. No one wants to eat a lumpy cake, and processors don’t want to deal with bottlenecks in their system.
Rotary airlock valves are some of the best tools you can use to meter and feed material at a controlled rate. As long as they’re properly designed and configured, valves excel at keeping material flow consistent.
Two common challenges in metering
Factors like conveying air pressure, aeration, and the valve’s rotor pocket size all impact your material’s rate of flow. Some fine-grained bulk powders are light and tend to over-aerate, while heavier materials may be prone to sticking together or agglomerating.
We generally see over-aerated powders in traditional blow-through valves using high-pressure settings. Too much air reduces rotor pocket capacity, which leads to inefficient material release and sometimes creates a sandblasting effect that wears down your equipment.
On the flipside, those sticky materials can build up in your system and cause blockages or issues with flow. That can happen when the conveying air pressure is too low.
Some materials are prone to both sticking and over-aerating. Each ingredient behaves differently, so your rotary airlock should be sized and configured based on the specific characteristics of your bulk material.
Rotary airlock choices for metering
Metering is all about precision and consistency. Rotary airlocks maintain a specific discharge volume by controlling the rotor’s speed of rotation. The choice of valve depends on your application, but they should be designed to minimize pressure loss throughout the system.
Blow-Through (BT Series) rotary valves
Blow-through valves are designed with an integrated connection on the housing for pressure conveying lines. The design optimizes the flow path of air through the rotor pockets, improving material release and reducing your total consumption of compressed air.
Testing and small batches
If you need to test a pilot system or meter small batches, you might need a very tiny valve — this one is smaller than a football. It can drop in to help you model processing parameters, dosages, and equipment compatibility within a larger system, or simply meter small, controlled amounts of fine material into larger batches.
More common applications
You may not need a specialized valve for your application, in which case more standard models like our CI Series and MD Series can be customized to offer a balance of performance and precision. Stainless-steel works well for keeping material flowing smoothly, but these models can also be equipped with special coatings, like a food-grade coating that prevents corrosion. Other variations, like a quick-cleaning valve with a rail system, can help you speed up maintenance time and prevent buildup.
Further fine-tuning with rotors
In addition to vent ports, rotary valve rotors for metering should come with eight or more vanes to help maximize the airflow path and improve material release. With their small grooves, metering rotors are a solid choice for maintaining an extremely controlled flow in test systems and small batches. They excel at moving powdery materials like flour.
If your material is prone to flowing too quickly, you can control it by reducing the valve’s cubic foot per revolution (CFR). Reduced-volume rotors prevent material from clogging downstream equipment by maintaining a lower CFR.
Meet your metering goals
In short, you want to choose a rotary valve that will give you the most control and consistency (with as few headaches as possible). That’s what our experts are here for. Give us a call to start configuring a valve that fits your metering application to a T.
