Skipping Ore to the Surface

The most common conveyance for carrying the ore to the surface is the skip. The skip is a self-dumping bucket and is usually operated in counter-balance in two separate shaft compartments to reduce the amount of power needed for hoisting. In other words, the weight of the empty skip descending will compensate in part for the weight of the other skip which is being hoisted.

Skips are of lightweight alloy construction and carry loads of three to greater than twenty tonnes. They are filled from the loading pockets at the base of the ore pass.

In some mining situations, hoisting by conveyor belts can be less expensive, and in mines developed by a decline instead of a shaft, it is very common to tram the ore directly to the surface by rail car or truck. The ore goes to the mill for crushing, grinding and beneficiation whatever way it gets to the surface. In some mining situations, the orebody at depth can be a long distance from the principal shaft. When this happens, an internal shaft might be needed for further development at depth. Such an underground shaft goes by the name of winze, and it has its own hoist with cages and skips.

A sump is at the bottom of every shaft or winze. It holds the groundwater that seeps into the mine so that it may be pumped either to the surface or to the water circuit of the mine.

Shafts are divided into separate compartments: one for the cage; one for the skips; one for the manway (a series of ladders for emergency access); and one for the service equipment such as compressed air, electric power cables, water discharge lines, data and communication highways for carrying electronic information. It is also very usual to have one or more raises to the surface for ventilation.