Lesson 1/Learning Event 2
Two types of mechanical feeders are used. These are apron feeders and reciprocating plate feeders. Apron
feeders are of heavy duty construction and are used to regulate the feed of quarry run rock into the jaw crusher for
the initial stage of reduction. The reciprocating plate feeder is a smaller feeder and is normally used to regulate
the flow of material which has already been reduced in size. It is commonly used to control the rate of flow to
secondary crushers, screens and washing
Production Considerations. Methods of Charging Feeders.
Criteria: Materials to be introduced into feeders have to meet certain criteria of size and cleanliness. Certain
precautions have to be taken to ensure this.
Selective loading: Selective loading is the loading of select material for transportation to the crushing plant. Its
basic purpose is twofold. First, it prevents oversize materials from being sent to the primary crusher with a
resultant stoppage of that unit. Second, when the material is to be used for concrete or asphalt aggregate,
cleanliness is important to avoid the need for washing the material. In this method, the shovel operator wastes to
one side all material that contains extra large pieces of material that is extremely damp and dirty which the
screening process cannot handle.
Prescreening of materials: When selective loading is impractical another method called prescreening is used. In
many operations prescreening is chosen primarily because of the inherent flexibility it provides. The most
common prescreening device is the grizzly. This screen is made of heavy bars or rails to eliminate oversized
rocks.
Truck Feed: Two levels are normally used for the crushing operation. The quarry run rock is dumped directly
onto the apron feeder or into a loading chute by trucks on the upper level. The rock is then processed through the
plant and discharged on the lower level via inclined conveyor belt. Alternatives to dual-level operation involve
double handling the material. These are acceptable for operations of short duration but are far less efficient for
longer operations.
Lifting and Loading Equipment Feed: Where jobs are of a short duration, the use of lifting and loading
equipment has become popular. Draglines, clam-shells, and shovels are used for this purpose
CONVEYORS
Function and Operation. Conveyors are used to move material being processed from one component to another
and to convey the finished product
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