What's Blowback?

Airlocks isolate and dose solids sitting above a positive pressure convey line.
Air from the conveying system inevitably leaks past clearances in the rotors, as well as the pulses of air released as each empty 'pocket' is rotated upwards. This release of air is called blowback.

What's the problem?

Blowback causes a number of problems, ranging from minor nuisance, to bad, to very bad, to catastrophic:

• Reduced Feed Rates
  Blowback up into the feed hopper can so severely disrupt bin flow that throughput from the airlock can be be 30 - 70% below expectations
  
  
• Hammering of Silo or Bin Outlets
  Maintenance folks are known to damage outlets with hammers in an attempt to move powders hung-up or clogged by blowback.
  
  
• High Wear and Erosion
  Blowback , particularly with abrasive powders, can be responsible for rapid wear to airlock seals, bearings, and housings, causing sudden failures and requiring frequent maintenance.
  
  
• Fugitive Dust, Leakage, Waste
  Blowback results in dusty, dangerous work environments and when handling foods, housekeeping/pest problems.
  
  
• Degraded Effectiveness of Process Equipment
  Leaking airlocks cannot be placed under screeners and sifters, which often turn sieves into fluid beds.

How do Fox Rotary Valve Venting Eductors help?

Fox Rotary Valve Venting Eductors ( RVE's) are used to suck blowback air + suspended solids out of the airlock and pneumatically convey them to the destination of choice: bin above, convey line below, other.

What Results Can We Expect with a Retrofit?

It depends on how bad your blowback problem was in the first place. But over the last 25 years, we've seen the following widely varied results:

• Increase in Airlock Feed Rates
  We've seen airlock throughput jump a small amount to as much as 50 - 80% with the elimination of the blowback bubble stopping the flow of material into the airlock.
  
  
• Decreased Wear , Increased Service Life
  We've had customers who replaced airlocks every few months say they last many times longer after retrofit with Fox eductors.
  
  
• Leakage & Waste - Eliminated
  
  
• Fugitive Dust - Elilminated
  
  
• Blowback into Screeners - Eliminated