Feeder or Conveyor- Which is It?

 

In any bulk material handling system, it is critical to be able to convey material from point A to point B as well as feed material out of a bin or hopper.  Often times, the terms feeder and conveyor are used interchangeably without much thought given to their function and design requirements.

A feeder is the means by which the rate of material from a bin¹ or hopper² is controlled.  When a feeder stops, material flow should stop as well.  When a feeder is turned on, there should be a close correlation between its speed of operation and the rate of discharge of the bulk material.  Examples of feeders include a belt feeder for coal, a vibratory pan feeder for applying seasoning to chips, and an apron feeder for ore under a stockpile.

Mechanical conveyors are used to transport bulk materials but, unlike feeders, they are incapable of modulating the rate of material flow.  Examples of conveyors include a drag-chain conveyor for hot clinker, a screw conveyor for limestone, and a belt conveyor to take ore from a primary to a secondary crusher.

The main difference between a feeder and a conveyor is that feeders are flood-loaded while conveyors are not.  Also, while conveyors typically operate at a constant speed, feeders are always capable of varying the speed of operation.  As a result, feeders are capable of modulating the discharge rate from the vessel that is flood loading it. 

These differences are summarized in Table 1 below.

Table 1: Summary of differences between feeders and conveyors

Attribute

Feeder

Conveyor

Mode of operation

100% full

Partially full

Speed of operation

Variable, relatively low speeds

Fixed, relatively high speeds

Capable of rate control

Yes

No

Dischargers are sometimes used to encourage material to flow out of a bin and, like feeders, they are flood-loaded.  However, a discharger is neither a feeder nor a conveyor since it cannot modulate the discharge rate from the vessel that is flood loading it.  An example of a discharger is a vibratory bin activator used for powdered soap.

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¹ General term used to describe a storage vessel. Other terms include silo, bunker, etc.
² Lower portion of a bin, which is usually converging in cross-section from top to bottom.

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