Understanding Valve Options for Abrasive Materials

Different types of valves serve specific purposes in material handling systems, and selecting the right one depends on the nature of the material being processed. Rotary valves are commonly used for handling free-flowing, low-abrasive materials. Their rotating blades move material through the system continuously. However, when dealing with abrasive materials, the rotating blades and housing experience rapid wear, leading to increased maintenance, reduced efficiency, and eventual failure. While rotary valves are ideal for light-duty applications, they are not suitable for handling large, abrasive particles over extended periods.

Why Double-Dump Valves Are the Superior Choice

In contrast, double-dump valves are specifically engineered to handle tough, abrasive materials without the drawbacks of rotary valves. Double-dump valves use two tandem gates that open and close alternately to discharge material, avoiding the friction and erosion associated with rotary valves. This design ensures that system pressure is maintained, preventing air seepage in both positive and negative pressure systems, which is crucial for maintaining efficiency in dust collection and bulk material handling. Furthermore, the robust design of double-dump valves allows them to handle chunky, fibrous, and coarse materials that could otherwise damage or jam a rotary valve. Since there are no rotating parts subject to constant abrasion, double-dump valves experience significantly less wear, leading to lower maintenance costs and a longer operational life.

The Consequences of Choosing the Wrong Valve

Selecting the wrong valve for handling abrasive materials can lead to serious consequences. First, a rotary valve subjected to abrasive materials will require frequent repairs due to blade erosion, resulting in unexpected maintenance costs and downtime. Frequent breakdowns and maintenance interruptions can halt production, impacting workflow and efficiency. In industries where time is money, these delays can add up quickly. Additionally, if the sealing components of a valve wear out, air leaks can compromise system performance, causing material loss, inconsistent flow rates, and higher operational costs. Constantly replacing worn-out parts or an entire rotary valve due to excessive wear can also be expensive. Choosing a more durable solution like a double-dump valve can help prevent these recurring expenses.

Why a Double-Dump Valve is the Best Investment

Investing in a double-dump valve is the most cost-effective solution for facilities processing large, coarse, or abrasive materials. Double-dump valves are designed to handle rough materials without significant wear and tear. They ensure proper air sealing to maintain system pressure and prevent leakage, reducing the need for frequent repairs and replacements. This leads to long-term savings by minimizing downtime, repair costs, and the need for constant part replacements.

Bottom Line: Choose the Right Valve for Your Application

For facilities handling abrasive materials, selecting the right valve is a crucial decision that directly impacts efficiency, cost, and operational longevity. A double-dump valve offers a reliable, long-term solution that minimizes wear, maintains system integrity, and reduces downtime. Choosing a valve specifically designed for tough material handling conditions can save time, money, and frustration in the long run. For large and abrasive materials, settling for a solution that wears out quickly is not advisable. A double-dump valve ensures smooth and efficient operations.

If it’s time to start exploring new material handling valves for your application, our engineering team is available for recommendations, products, and installation support. To speak directly with our applications engineer, Dan, dial 440-543-7400 x 235, or send us an email at dc@dustcollectorhq.com. For all other inquiries, click here. 

The post Why a Double-Dump Valve is the Best Choice for Abrasive Materials | Aerodyne first appeared on Aerodyne Environmental.]]> https://www.dustcollectorhq.com/optimizing-dust-collection-efficiency-exploring-airlock-alternatives/ Mon, 28 Apr 2025 23:45:00 +0000 https://www.dustcollectorhq.com/optimizing-dust-collection-efficiency-exploring-airlock-alternatives/ Selecting the appropriate airlock for your dust collection system is crucial for ensuring optimal performance and efficiency. While the rotary valve is a common choice, exploring alternative airlock options can lead to better results tailored to your specific application needs. In this article, we’ll delve deeper into the various airlock alternatives available, highlighting their features, […]

Rotary valves will occasionally jam. This can happen when material gets between the rotor and the housing or when oversized material cannot fit into the rotary valve pockets.   Depending on the type of jamming that is happening you handle the situation differently.

Space Between Rotor and Housing

Rotary valves have a space between the rotor and the housing. This space allows the rotors to rotate freely but it can also allow air to leak across the valve. When materials falls on the rotor edge it can buildup and jam the rotary valve. So for existing rotary valves, you might have to replace or modify the existing rotor. Beveling or chamfering the rotor edges help the material to fall off the edge and into the valve pockets.

When Jams Caused by …

For jams caused by oversized material, a valve with larger pockets is required. This could mean a larger rotary valve or replacing the rotor with a rotor containing one less pocket. Please note if the rotary valve is on an explosive application, NFPA requires a minimum of six vanes on the rotor. If these options aren’t possible, looking into a double dump valve might provide larger clearance for oversized material to pass through.

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To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click here to connect with our applications engineer about your application.

Motorized Double Dump Valve

A motorized double dump valve uses a cam rotated by a motor and gearbox to open and close each of the dump valves in series. The cam is designed so that at least one valve is closed at all time, thereby providing an airlock. The cam also provides a certain amount of cycles each minute, which controls the amount of material that is available to pass through the valve.

Pneumatic Double Dump Valve

A pneumatic double dump valve uses one pneumatic cylinder on each dump valve to control the operation of it. A timer is used to control the cylinders. The timer cycles cylinders so that one valve is closed at all times.

Differences Between Pneumatic and Motorized Double Dump Valve

Pressure – Motorized double dump valves are limited in the amount of pressure they can handle. The cam drive doesn’t provide direct force on the flap plates. This means that higher pressures and weights will push the flap plate open. The pneumatic valve, however, provides direct pressure on the flap plate so it can handle higher pressures and weights.

Temperature – A motorized double dump valve has a gearbox and motor located next to the housing of the valve. At higher temperatures, this can cause issues with the grease in the gearbox and motor. Also, the cam drive uses wear plates that might degrade faster at higher temperatures. The pneumatic valve, however, can be supplied with high temperature seals on the pneumatic cylinder.

Material Flow Rates – Unlike a rotary valve, which is continuously passing material through, double dump valves fill one chamber while emptying the other. This significantly cuts down on the flow rate through the valve. A motorized double dump valve size is limited due to the cam design. A spool piece cannot easily be installed to increase the volumetric flow through each chamber. While with a pneumatic design, each flap plate is controlled by its own pneumatic cylinder, a spool piece can easily be installed to allow additional material to flow through.

Area Classifications – The electrical classification of the area the valve is being installed can also effect the valve selection. A pneumatic valve has very few electric parts and can be designed to be intrinsically safe. A motorized unit has an electric motor, so the motor must be selected to for the area classification.

When selecting the best double dump valve for your application, look at the pressure, temperature, material flow rate, and area classification.

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To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click here to speak with a member of our engineering team about your application, anytime. 

Some dust collection system issues that could come with air leakage include:

1. Decrease airflow at pickup points – If an airlock leaks too much air into a system, it could decrease the airflow at the pickup point, thereby causing less dust to be collected.
2. Blowing dust out of the airlock – If too much air leaks out of the system through the airlock, the collected dust might be blown out of the airlock, causing the collected dust scatter on the ground around the dust collector.
3. Dust that reacts with water – Humidity from outside the process can cause dust to become sticky, bridge, or even explosive in special circumstances.
4. Systems that are oxygen deficient for reaction or explosive prevention – Outside air can introduce oxygen to the system which could feed a reaction or move the process into the explosive zone.
5. Systems that have a high pressure or low vacuum – Leaking airlocks can bleed pressure or allow outside air into a high vacuum, requiring the pressure control system to work harder.

If you have an issue like this, you might want to look at your airlock.  While rotary valves are the industry standard, and currently the only valve approved for explosion isolation in the NFPA, they do constantly leak air into or out of the system.  The reason is the rotor has a small clearance between it and the valves housing.  This allows a path for air to travel.  So while this path is small you will always get some leakage into or out of the system with a rotary valve.

Other valves that will minimize leakage include

• Double dump / knife valve – This valve uses what is essentially two valves in series. And while one of the valves is open, the other is closed.  This prevents air from leaking in or out since there is no direct opening through the valve.  The major drawback of this valve is that the capacity of the valve is severely restricted.  A rotary valve will have a higher flowrate through the same diameter valve.  The other advantages include that these are better with chunky or fibrous materials.
• Trickle valve – A trickle valve (like the Vacu-Valve®) uses the vacuum of the system to seal a sleeve. This prevents air from leaking into the system.  Gravity will then pull the dust through the sleeve once enough material is built up above the valve.  This valve can be used if: the system has negative pressure; the dust is free-flowing dust and won’t bridge; and the dust is not explosive.  The advantages of a trickle valve include no moving parts, low cost, low maintenance, and no power is needed.

In summary, when designing your dust collection system, don’t just pick a rotary valve, make sure that air leakage will not cause an issue.  And if it does, then look for an alternative that will minimize the leak leakage.

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While rotary valves are the industry standard airlock, they constantly allow air leakage. A low-leakage valve is required. Double dump valves, however, are very low leakage since there is no direct connection to the outside atmosphere. The valve always isolates the conditions above it from the conditions below it. This minimizes air leakage, thereby reducing humidity from affecting the dust and improving the performance of your industrial dust collection system.

So, if you have a non-explosive application that is hygroscopic, look into a double dump valve (flap valve) for your dust collector.

Find out more information now.

If you are having operational issues with your dust collection system, contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com.

The following will help you figure out which is the best solution:

1. Rotary valve – Use this if you have combustible dust. However, you will have constant air leakage across the valve.
2. Double dump valve – Use this if you want to minimize air leakage. The Double Dump works great with big, chunky material or if you’re worried the material may wrap around a rotary valve rotor.
3. Trickle valve – Use to save money and time. Requires a vacuum and usually a fine, free-flowing particle to work effectively.  It’s low cost and easy maintenance makes it very attractive when suitable.
4. Knife Gates – Used for periodic emptying of the dust collector hopper into another container. Knife gates come in a variety of design (knife gate, slide gate, orifice type, etc.).  Depending on the design, they can provide an airtight seal or not.  However when open, the airlock is lost.
5. Direct couple to a hopper – Used with low dust loading and could require the dust collector to be turned off during changing of the hopper. Also be-careful to take into account the lower hopper when used on a combustible dust application.

When you are looking for an airlock, don’t just automatically use a rotary valve.  Doing so may cause operational and maintenance issues in the future.  It could also cost you more money.  If you would like help in picking the best airlock, don’t hesitate to contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com. He is available to help you to solve your dust collection issues.

3) Choose the Right Material Handling Valve for Your Material

What’s up with your dust? Probably the most important consideration for any material handling valve application is the material itself. The characteristics of the material being handled will determine which type of valve should be selected. Extremely fine material typically requires a valve with tight tolerances and seals to prevent dust from escaping into the atmosphere. Coarse or chunky materials often require a valve with larger clearances to prevent plugging or jamming of the valve mechanism. A common problem some rotary valves experience is large chunks of material becoming jammed between the rotor vanes and valve housing. While some design innovations help prevent this issue, the best solution may simply be selecting a different material handling valve that is better suited to the material.

Double dump valves, also known as double flap gate valves, are designed to allow large, chunky, and abrasive materials to pass through with minimal chance of blockage. Pairing the proper material handling valve with the material being handled is crucial for a successful installation and improved dust collection efficiency.

2) Will The Valve Meet Your Operational Parameters?

Not all material handling valves are created equally, and the environments they are expected to operate in vary as well. In many cases, material handling valves are installed on systems with some degree of atmospheric pressure differential. Most are intended to function as an air lock valve for dust collector applications, allowing solid material to pass through the system without significant pressure losses. Be sure to select a material handling valve with a pressure rating that matches the conditions in which it will operate.

Temperature is another operational condition that should be taken into account. Any gaskets or synthetic seals should be rated to handle the expected process temperatures. High-temperature bearings or bearing stand-offs should be utilized in order to maintain functionality in extreme conditions. Abrasive or corrosive materials may require special material construction. So again, it is imperative that you really know and understand your dust!

In addition to atmospheric conditions, it is also important to consider the type of work demanded of the material handling valve. A rotary valve intended for use as a material feeder may have far different requirements than a rotary valve intended for use as a dust collector rotary airlock. Likewise, an industrial knife gate valve intended to meter material flow will have a very different service life than one used strictly as a maintenance valve to shut off material flow during periodic system maintenance. Always consider the duty cycle and performance expectations placed on the valve.

3) Powering Your Material Handling Valve

All too often, plant maintenance personnel accept the “standard” valve control type listed by the manufacturer rather than choosing the best actuation method for the job. Pneumatic cylinders are the most widely used actuators for knife gate valves and many other process valves due to their continuous-duty rating and readily available shop air supplies. While pneumatic controls may appear to be an easy and convenient method to operate a knife gate valve, a manually operated unit may be more suitable and cost-effective for maintenance valves which are operated very infrequently. Many double dump valves use pneumatic cylinders to provide a precisely timed open-close sequence.

In some cases however, a specific timing sequence is not as crucial as consistent and reliable operation. A mechanically operated double dump valve using an electric motor-driven cam offers lower cost and fewer components to fail or replace. A trend in powering rotary valves is the use of electric gear motors which combine an electric motor and gear reduction box into one compact unit. While this method of operation has its advantages, it lacks the flexibility of a traditional chain drive assembly.

One type of material handling valve gaining popularity in dust collection systems is the non-powered automatic trickle valve. These valves utilize the negative pressure of a cyclone or baghouse to hold a rubber sleeve closed and create an airlock seal. As material builds up on top of the valve, it automatically opens to discharge collected dust. Trickle valves work best with dense, free-flowing materials and are typically a fraction of the cost of many other dust discharge valves.

Click here to watch an animated demo of a trickle valve system

4) Material Handling Valve Maintenance

Regular maintenance is a must for any material handling valve. As valve parts wear or material build-up occurs, the need for replacement, repair, and cleaning of the valve is inevitable. When choosing a material handling valve, one needs to pay close attention to how easy (or not easy) the valve is to maintain. Quick-release access panels, change-in-place parts, and easily accessed wear parts all make the job of performing regular service on a valve much easier.

Another aspect that will affect the maintenance of a valve is the valve’s overall reliability. Even a valve with easily accessed or easily replaced parts can still become a maintenance nightmare if those parts frequently break or wear out. Choosing a valve for reliability and ease of maintenance will help to save time and money over the life of the valve.

5) How Much Will it Cost?

While the initial investment for a material handling valve is important, it is only part of the equation. Frequent repairs or labor-intensive repairs to a valve can easily eat into any initial savings in cost. The cost of process downtime due to maintenance needs can become magnified if the valve cannot be repaired in place or replacement parts are not readily available. For dust collection systems it is often recommend to install a knife gate valve above the primary material discharge valve to be used as a service valve. The knife gate can be used to temporarily seal the system while maintenance is performed on the primary valve. Although the addition of a knife gate valve to the system adds to the overall cost, the benefit of avoiding a system shutdown during maintenance can far outweigh this cost.

Doing the proper due-diligence also goes a long way in selecting the best material handling valve for a given application. Just because a rotary airlock is the most familiar type of valve does not mean it is the right type of valve for the job. There may be a less expensive type of valve that can easily handle the same task or a more expensive valve that is more appropriate for the application. Realistically, the success of a material handling valve comes down to the careful consideration of application parameters and how much time and effort is given to make sure the appropriate valve is selected.

A customer in Mexico has a process that involves adding plastics to a shredding device. The facility operates a cartridge collector and a knockout box. The plastic materials that come out of the shredder gets vented to the dust collectors above. The plastic is then fed via a screw conveyor to a rotary valve and into storage bags.

The company was having issues with the dropout box not getting enough removal and plastic particles were causing issues for the rotary valves. The company reached out to Aerodyne for a solution.

Aerodyne offered using a GPC to replace the dropout box and adding the GatorGate double dump valve to better handle the oversized plastic pieces. The GPC dust collector is a compact high efficiency cyclone dust collector. It has several distinct advantages over common high-efficiency cyclone dust collectors. The spiral inlet of the GPC directs the dirty gas stream toward the ground plate and hopper of the collector. Coupled with the compact size of the collectors, this gives the GPC the ability to be installed horizontally with virtually no effect on the collection efficiency. This cyclonic dust collector can improve any dust collection system. The GPC will remove around 99% of 20-25 micron and larger dust while the large chambers on the double dump valve will pass the over sized particulate.

The GatorGate is an efficient and reliable double dump valve available for the discharge of chunky, fibrous, and abrasive materials from dust collection systems. The unique cam operated drive mechanism provides reliable service without the use of expensive and problematic pneumatic controls. As the motor driven cam rotates, it actuates the upper and lower flap gates in sequence, allowing material to discharge while ensuring minimal leakage. Quick removing inspection doors provide easy access to internal components for regular maintenance and can be configured to operate using air or electricity. The GatorGate Double Dump Valve is available in a variety of sizes and is a great alternative for applications not suited for rotary air lock valves.

To learn more about Aerodyne’s dust collection equipment, click the photo below.