{{unreferenced, date=April 2011 Double dump valves, also known as double flap valves or double flap gates, are a type of

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valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...

commonly used in industrial applications as a component in

bulk material handling Bulk material handling is an engineering field that is centered on the design of equipment used for the handling of dry materials. Bulk materials are those dry materials which are powdery, granular or lumpy in nature, and are stored in heaps.http: ...

applications. Double dump valves are primarily used to discharge chunky or fibrous, bulk materials from

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s, bins, and

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operating under positive or negative pressure. Double dump valves are used to discharge a flow of material while at the same time serving as an airlock transition point to preserve the pressure differential above and below the valve. This type of material handling valve is ideal for use with bulky or abrasive materials that would tend to jam or damage a rotary feeder.

Operation

Double dump valves have two trap-door flap plates which open and close on an alternating cycle. The top gate opens to allow collected material to drop through onto the bottom gate. The top gate then re-closes to prevent air leakage above the valve. The bottom gate then opens to allow material to pass completely through the valve. The bottom gate then re-closes to prevent air leakage below the valve. This cycle is continuously repeated in order to maintain a steady discharge of material from the valve, while maintaining a positive seal on the system.

Design

Timing of the flap plates is critical in order to make sure a double dump valve operates properly. There are several designs that have been employed in order to maintain a consistently operating valve.

Control systems

Pneumatic

Each flap plate has its own

pneumatically Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A centrally located and e ...

operated cylinder and

solenoid valve A solenoid valve is an electromechanically operated valve. Solenoid valves differ in the characteristics of the electric current they use, the strength of the magnetic field they generate, the mechanism they use to regulate the fluid, and the ty ...

. The timing of the valve is controlled by an electronic signal sent to the solenoid valves. This method of operation is the most expensive and allows for accurate timing of the valve.

Counterbalance

This type of double dump valve works essentially, like a stacked pair of trickle valves. Each flap plate is held closed with a

counterweight A counterweight is a weight that, by applying an opposite force, provides balance and stability of a mechanical system. The purpose of a counterweight is to make lifting the load faster and more efficient, which saves energy and causes less wear ...

ed arm. As material builds up on the top plate the weight of the head of material pushes it open where it dumps onto the bottom plate. This type of double dump valve has no electrical or pneumatic controls and is the least expensive method of operation. However, it is difficult to sustain a properly timed cycle.

Cam-operated

A motor-driven

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rotates and alternately opens the top gate and the bottom plate. A spring attached to the gate’s shaft re-closes the gates. This type of double dump valve is generally the most reliable and can be operated with an

electric motor An electric motor is an Electric machine, electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a Electromagneti ...

or a

pneumatic motor A pneumatic motor (air motor), or compressed air engine, is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed air energy to mechanical work through either linear or rotary m ...

. The speed of the cycle can be selected through the gear reducer ratio or by adjusting the motor speed.

References

Valves Bulk material handling de:Doppelpendelklappe