Trickle valves, also known as vacuum valves, are commonly used in

industrial Industrial may refer to: Industry * Industrial archaeology, the study of the history of the industry * Industrial engineering, engineering dealing with the optimization of complex industrial processes or systems * Industrial city, a city dominate ...

dust collection applications to maintain an

airlock An airlock, air-lock or air lock, often abbreviated to just lock, is a compartment with doors which can be sealed against pressure which permits the passage of people and objects between environments of differing pressure or atmospheric compo ...

seal on a dust collector

hopper Hopper or hoppers may refer to: Places *Hopper, Illinois *Hopper, West Virginia * Hopper, a mountain and valley in the Hunza–Nagar District of Pakistan * Hopper (crater), a crater on Mercury People with the name * Hopper (surname) * Grace Ho ...

while allowing bulk solid material to be automatically discharged. These valves are typically a less expensive alternative to more commonly used rotary airlocks. Unlike rotary airlock valves which are driven by either an

electric motor An electric motor is an 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 wire winding to generate forc ...

or a gas or air-powered motor, trickle valves require no external power source and are therefore well-suited for use in mechanical trenchers, where a dust-free environment in the pinnacle truss and axle bore is required for smooth operation. Trickle values were originally developed for this purpose.

Operation

Trickle valves can be used only on systems operating under

negative pressure Negative pressure may refer to: * Negative value of a pressure variable * Negative room pressure, a ventilation technique used to avoid contaminating outside areas * Negative pressure ventilator A negative pressure ventilator (NPV) is a type of m ...

. The

vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...

created inside the dust collector holds the valve closed, allowing a head of material to build up above the trickle valve. Once the pressure of the material equals the negative pressure of the system, the valve is forced open and a trickle of material will begin flowing from the valve at the same rate it is collected. The magnitude of the vacuum of the system and the bulk

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematicall ...

of the material being handled determine how much material will build up before the valve begins to discharge. Because trickle valves work automatically and require no power source or controls, they have very low initial cost and virtually no operating cost.

Design

A well designed trickle valve has few or no moving parts. Most trickle valves are also adjustable as to how much vacuum pressure it takes to operate. Adjustments are typically made with a weighted counterbalance or an adjustable

leaf spring A leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicles. Originally called a ''laminated'' or ''carriage spring'', and sometimes referred to as a semi-elliptical spring, elliptical spring, or cart spring, ...

. Because these valves have no way to force clogs through, they are only recommended for use with dry and relatively dense, free-flowing materials such as

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a soil texture, textur ...

fly ash Fly ash, flue ash, coal ash, or pulverised fuel ash (in the UK) plurale tantum: coal combustion residuals (CCRs)is a coal combustion product that is composed of the particulates (fine particles of burned fuel) that are driven out of coal-fired ...

, and

cement A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together. Cement m ...

Types

Duckbill sleeve type

This type of trickle valve utilizes a specially designed duckbill rubber sleeve. The negative pressure of the dust collection system collapses the sleeve on itself, creating an airtight seal. Adjustable leaf springs are inserted into the sides of the sleeve which help to resist the vacuum. The weight of collected material above the valve forces the sleeve open to allow a steady discharge. Duckbill sleeve trickle valves have no moving parts.

Trap door type

Trap door trickle valves have one moving part, a hinged flap plate to maintain a seal between the hopper and the discharge. This type of valve is adjusted with an external weighted counterbalance or it is not adjustable. Greased bearings are required for smooth operation of the flap plate’s hinge.

References

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External links

Trickle Valve
Valves Bulk material handling