How Do Diverter Valves Work in Pneumatic Conveying?

When there are multiple pick-up points in a pneumatic conveying system, diverter valves are essential. They ensure materials are directed smoothly, continuously, and hygienically. Continue reading to understand the role of diverter valves in pneumatic conveying systems, how they work, what the different types are, and factors you should consider before making a selection. 

What Are Diverter Valves?

In pneumatic conveying systems, diverter valves are used to direct materials towards multiple destinations, or “pick-up points”. They can also be used to direct the material from multiple locations to a single location. 

Diverter valves allow for the smooth, continuous flow of materials, thus minimizing clogging, product contamination, and pressure drops. Appearing in many different robust designs, they’re suitable for a range of pneumatic conveying systems, whether they’re indoor or outdoor, dilute or dense phase, and so on.

How Do Diverter Valves Work in Pneumatic Conveying Systems?

In pneumatic conveying systems, diverter valves are installed along the conveying line. The way diverter valves work in pneumatic conveying systems will vary from design to design, but in general there are four key things going on:

  • An oscillating tube is fitted onto the diverter to allow it to move automatically in any direction or position
  • A limit switch ensures the positioning of the oscillating tube is correct
  • Electric valves control the movement of the oscillating tube, using a manometer to measure and indicate pressure
  • An inflatable seal is installed on the head of the oscillating tube to provide a tight seal between the inner rotating pipe and the outer fixed ends

What Are the Applications of Diverter Valves?

Diverter valves have many applications in pneumatic conveying because of the hygienic and smooth passage they facilitate for materials.

For instance, diverter valves are particularly useful in the pneumatic conveying of food and beverages because they avoid product retention, thus providing hygienic transportation and mitigating the risk of food contamination. 

Diverter valves can also be used in dense phase pneumatic conveying systems to safely transport fragile, and even abrasive materials. By having a tight seal, diverter valves are also ideal for materials that have a tendency to clog or become easily contaminated.

Finally, since their primary purpose is to direct material flow to multiple outlets, diverter valves are not only ideal, but necessary for applications where multiple product pick-up points are required.

Different Types of Diverter Valves

There is a huge range of diverter valves designed for different pneumatic conveying systems and their unique needs. Even still, there are some common characteristics that can be seen across the board: they must provide a tight seal, maintain hygienic conditions, minimize pressure drops and pipe blockages, and preserve the integrity of the material particles.

Here are some of the different types of diverter valves out there:

  • Drum diverters: Also known as rotating plug diverters, these are among the best designs for hygienic applications. This is because their design allows them to provide a tight seal up to a 6-bar operating pressure, thus avoiding any kind of product retention. 
  • Rotary tube selector valves: These can be used in both dilute phase, dense phase, and vacuum pneumatic conveying systems to direct the flow of material to one or multiple locations. They’re particularly useful in high pressure applications for transporting fragile or abrasive powders.
  • Rotating pipes: This diverter valve system has the advantage of being cheap, compact, and offering up to twelve outlets. Its drawback, however, is that it doesn’t provide as tight a seal as other diverter valve designs, meaning it’s only really suitable for dilute phase conveying.
  • Y-type diverter valves: These are also useful for dilute phase pressure systems, as well as vacuum pneumatic conveying systems. However, they’re not ideal for abrasive materials and should only be used to convey non-abrasive powders.
  • Ball valves: As the name suggests, this design uses ball valves to allow the diverter to change position. This isn’t ideal for food transportation, or for applications where product contamination must be avoided, because the design doesn’t safeguard against product retention. 
  • Fill vent valves: Also known as “scale divert valves”, fill vent valves are exclusively used to direct the flow of powders into hoppers. When a predetermined weight has been reached in the hopper, the remaining material is quickly directed away from the hopper and back to the source silo.

How to Choose the Right Diverter Valves

While many different types of diverter valves exist, each one fulfilling a variety of needs, it can still be challenging when it comes to choosing the right one for your pneumatic conveying system. 

There are several factors you should consider:

  • Cost: Perhaps the biggest driver behind which diverter valve you should choose is the initial cost of it. But you should also bear the long-term expenses in mind. Weigh the purchase price against the installation cost, estimated maintenance costs, and how it will affect your system long term. For example, if it has a low purchase price, but poor sealing, the cost of product contamination due to leakage could end up costing you more in the long run.
  • The system: It’s crucial that you determine what type of pneumatic conveying system a diverter valve is designed for so that you can assess whether it will perform optimally in your own. Diverter valves for dilute phase systems may not be suitable for dense phase systems, for example.
  • What material are you conveying? While some diverter valves are excellent for applications involving frangible or abrasive materials, others may only be designed for things like non-abrasive powders or liquids. You must take into account the characteristics of the specific material you’re conveying so that you can choose a design that will successfully handle and protect your product.
  • Overall design: What material is the diverter valve and its components made from? From cast aluminum and cast iron, to stainless steel or a specialty alloy, you should make your selection based on the needs of the material you’re conveying. You should also use your system’s specifications and power availability to inform your choice of actuators, which can either be manual, air actuated, or involve the use of an electric motor. 

Even with all this knowledge, it can still be difficult selecting the right diverter valves for your pneumatic conveying system. If you’d like to speak to an expert about your specific needs, contact us today.

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