Double flap valves, also known as double dump valve, are a type of airtight valve. It is commonly used for bulk material handling in the industry to discharge solid, granular, powder or compact bulk materials from silo, bin, cyclone, and hopper operating under positive or negative pressure. It is used for discharging the material while in airlock mode to maintain differential pressure above and below the valve. It is also used for bulky and abrasive material that tend to jam or damage rotary air lock valve.
Double flap valves have two flap plates which open and close on an alternating cycle. The top plate opens to allow collected material to discharge into the bottom plate. The top plate then re-closes to prevent air leakage above the valve. The bottom plate then opens to allow material to discharge. The bottom plate then re-close to prevent air leakage below the valve. This cycle is continuously repeated to maintain continue discharge and airlock. For abrasive material flap and body liner MOC can be provided with Hardox.
Types of Double Flap Valve
1. Electro Pneumatic :The valve is operated electro pneumatically. The accuracy of valve is extremely high. The flaps have individual pneumatic cylinder along with solenoid valve and the sequential timer to-control the flaps movement properly.
2. Motorised : It is operated with an electric motor or pneumatic motor. The top and bottom flap alternately opens and close through cam arrangement. The speed of the cycle can be selected through the gear motor or geared box by adjusting the motor speed.
3. Counterbalance : This is counterbalance or dead load type valve. The top and bottom flap alternately opens and closes through dead weight attached to the individual flap.