Dust Collection and Valves Blog

Pneumatic vs Motorized Double Dump Valves | Aerodyne

Posted by Tom Hobson on Jan 29, 2021 9:45:00 AM

Double dump valves are available in both motorized and pneumatic actuation. To figure out which would be better for you we need to consider your application. A double dump valve is really two (2) valves with flapper plates in series controlled by the same mechanism. At least one of the flapper plates is closed at all time. The main things we need to know are the pressure, temperature, and flow rates along with the area classification the double dump valve will go in.

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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Topics: dust collector, double dump valve, Dust Efficiency Clinic, compact cyclones, Dust Collector filters, Cyclones pre-filter, Dust Re-Entrainment

Reduce Air Leakage with the Aerodyne Double Dump Valve

Posted by Tom Hobson on Jan 30, 2018 9:01:19 AM

When your dust collectors are having issues, one of the first places to look is the airlock valve.  Often times, dust is hygroscopic and when outside air leaks into the system, humidity follows.  This can cause the dust to absorb the humidity and become sticky or harden like cement.  This can lead to plugged filters, hoppers and damage to rotary valves.  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 minimizing humidity from affecting the dust.

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

Find out more information now.

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If you are having operational issues on your dust collection system, contact Aerodyne at 440-543-7400 or dc@dustcollectorhq.com.
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Topics: double dump valve, airlocks, airlocks valve, air leakage

Dust Collection Systems: 5 Best Solutions of Dust Collection Airlocks

Posted by Tom Hobson on Apr 24, 2017 8:30:00 AM

When you are specifying your dust collector, don’t just settle on a rotary valve.  There are other airlocks that might be better suited for your application.  Other airlocks include the double dump (flap) valve, trickle valve, and knife gate.  Not to mention just bypassing an airlock totally and connecting a hopper directly to the bottom of the dust collector.

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.

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Topics: knife gate valve, rotary valves, double dump valve, trickle valve, direct couple to hopper

Aerodyne Environmental: Home of the Horizontal Cyclone and  Vacu-Valve® Airlock Valve

Inspired To Be Different.

At Aerodyne, we choose to take a different approach to collecting dust and handling materials. Our cyclones are unique in design to address common issues such as problematic dusts and space constraints. Our airlocks are chosen to fit your specific application instead of hastily installing traditional equipment options. We believe that when we see things differently, we can solve problems effectively. That's why so many people turn to us for help in solving their tough dust problems.

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