Once the ore has been blasted and hauled from the mine, it is sent through the milling process. At the beginning of each major stage of processing there is a holding area where the ore is stockpiled to ensure that the next phase of the process has enough material for continuous operation.
The ore must then be guided through each of these different phases at a controlled even pace. This is accomplished by the use of variable speed conveyors or adjustable feeders. Considering that variable speed conveyors are discussed in the following sessions on conveying, I won’t go into them here. What I will be doing is explaining how the feeders work and their part in the milling process.
There are two factors apparent within the operation of coarse ore feeders. The first is that the ore itself is moving. This is to say that in other forms of material handling, the ore is being carried as in a truck or on a conveyor. The ore itself is stationary but the vehicle that it is on or in, is moving. With a feeder however it is the equipment that is stationary while the rock moves. The second fact, is that the feeder usually is a restriction to that ore movement.
These two pieces of information are important to the operator since they will dictate the amount of supervision that the feeders will require. This is because the ore movement across and through the equipment causes wear that will require steady maintenance. Also the restriction of the
feeder provides an area where plug ups have a chance of developing.
Coarse Ore Feeders can roughly he classified into two groups, those that handle coarse ore, rock that is destined to become feed for the crushing department. And those that handle the fine ore, material that is finished being processed by the crushing plant.
The different types of feeders that handle the coarse ore are, Ross feeder, pan feeder, vibratory feeder, apron feeder, and finally a simple sliding gate. These are the main types, there are others but most are similar to these.
One of the controls that an operator has over these feeders regardless of the kind, is the speed at which the ore enters the feeder at. The speed that the ore is moving as it comes into the feeder will greatly affect its speed as it leaves therefore it must be controlled. To do this lengths of chain are hung in front of the feeder. If the ore is moving slowly the chains are lifted up out of the way to provide a clear passage in which the ore will move. If on the other hand the speed of the rock is excessive then more chain will be hung into the flow to slow it. The amount of chain that is used will vary depending upon speed and the size of the ore.