Main area of application for Double Flap Valves is as a Rotary Valve replacement when they are used on the conveying system for fines/filler from the bag filter. The bag filter is situated downstream from the aggregate drier and dust loads can be quite high.
Not all plants use pneumatic conveying systems for moving the filler from the bag filter to the storage silos. Where they are used the problems of leakage and environmental spillage can be severe. Plants have been threatened with action from the environmental agency for such discharges.
Typical wear rates on Rotaries can result in valve change out between 2 months and a year depending on the nature of the material from the bag filter. Double Flap Valve replacement of internals vary from 3 years to about 8 years. The benefit costs can therefore be considerable.