Rotary valves, even when new, leak a certain amount of air from a pneumatic conveying line up past the valve blades and into the baghouse/cyclone.  The amount of air leaked is significant as the inherent design of a rotary valve means it must have a tolerance between the blades and housing in order  to operate.  As the rotary valve wears the tolerance between the blades and housing increases and with that the amount of air leaked up into the baghouse/cyclone increases too.  

The selected sequentially operated short series double flap valves allow the two environments to be isolated from each other but allow material to travel between them.   European Gate Valves concedes that double flap valves cannot entirely eliminate some leakage of air between the two environments but the tiny amount of air leaked will remain constant over the life time of the valve.  This is due to the seats and flaps having a metal-to-metal seal.  The company points out that, unlike rotary valves, double flap valves have no wiping action causing internal parts to wear and therefore increase air leakage. www.egatevalves.co.uk 

 

 

 

 

 

Double flap valves from European Gate Valves at the sintering plant