Tuesday, May 2, 2017

The Difference Between a Feeder and Conveyor

In a bulk material handling system, feeders and conveyors are very important. Feeders and conveyors not only function much differently, but their design requirements are also very different. If a conveyor is misused for a feeder, increased power requirements as well as stagnant regions within the bin could occur. The decision must be made of which will be used when designing a bulk material handling system.

A feeder controls the rate of material from either a bin or a hopper. When the feeder stops, the material slow should also stop. Feeders are flood-loaded and are capable of rate control. Feeders are able to modulate the discharge rate from the vessel that is flood loading it. They also have a relatively slow speed of operation, but the speeds are not fixed. At times, more than one feeder may be needed for a particular application. Feeders are to operate when they are one hundred percent full. Belt feeders for coal, vibratory pan feeders for applying seasoning to chips, and apron feeders for ore under a stockpile are all examples of feeders.

Mechanical conveyors are used to transport bulk materials, but are not able to modulate the rate of material flow. Conveyors, unlike feeders, are not flood-loaded and are running at a constant speed. The constant speed for a conveyor is much different than a feeder; it runs at relatively higher speeds. Conveyors are to operate when they are partially full. Drag-chain conveyors for hot clinker, screw conveyors for limestone, and belt conveyors are all examples of conveyors.

A general rule in a bulk material handling system is that conveyors should not be used as feeders and vice versa. A feeder should always be used if modulation of flow rate is needed and if mass flow in the bin above is required. A combination of a feeder and conveyor should be used if the horizontal distance between the hopper outlet and discharge point is two to three times the length of the outlet. Selecting and designing a specific feeder for particular jobs is not a huge deal. On the other hand, conveyors have much stricter design rules.