Hoist (mining)
Encyclopedia
Shaft mining
Shaft mining or shaft sinking refers to the method of excavating a vertical or near-vertical tunnel from the top down, where there is initially no access to the bottom....
. Modern hoists are normally powered using electric motors, historically with direct current
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
drives utilizing solid-state converters (thyristors), however modern large hoists utilize alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
drives that are variable frequency controlled. There are three principal types of hoists used in mining applications:
Drum hoist
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. When using a drum hoist the hoisting cable
Wire rope
thumb|Steel wire rope Wire rope is a type of rope which consists of several strands of metal wire laid into a helix. Initially wrought iron wires were used, but today steel is the main material used for wire ropes....
is wound around the drum when the conveyance is lifted. Single-drum hoists can be used in smaller applications, however double-drum hoists easily allow the hoisting of two conveyances in balance (i.e. one skip being lifted while a second skip is being lowered). Drum hoists are mounted on concrete within a hoistroom, the hoisting ropes run from the drum, up to the top of the headframe
Headframe
A headframe is the structural frame above an underground mine shaft. Modern headframes are built out of steel, concrete or a combination of both...
, over a sheave
Sheave
A sheave is a wheel or roller with a groove along its edge for holding a belt, rope or cable. When hung between two supports and equipped with a belt, rope or cable, one or more sheaves make up a pulley. The words sheave and pulley are sometimes used interchangeably.A sheave can also refer to a...
wheel and down where they connect to the conveyance (cage or skip).
Advantages
Drum hoists require less routine maintenance than a friction hoist, because the haulage cable is fixed to the drum, and therefore have less downtimeDowntime
The term downtime is used to refer to periods when a system is unavailable.Downtime or outage duration refers to a period of time that a system fails to provide or perform its primary function...
, and the maintenance regime is less sophisticated. Drum hoists can continue to operate if the shaft bottom gets flooded and less shaft depth is required below the loading pocket, unlike friction hoists where such flooding could cover the tail ropes etc. Because drum hoists do not have tail ropes, the hoisting system is more suited to sling
Sling
The word sling may refer to:* Sling , a device used to hurl projectiles* Sling is an item of climbing equipment consisting of a sewn loop of webbing that can be wrapped around sections of rock or tied to other pieces of equipment.* Sling * Ski jumping sling is an item of sports training...
ing beneath a conveyance.
Disadvantages
Drum hoists take up more space than a friction hoist for the same service as all of the haulage cable must be accommodated on the drum when the hoist is fully raised. Drum hoists require rapid fluctuations in power demand, which can pose a problem if power is generated on site rather than provided through the main power gridElectric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
.
Friction hoist
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. The friction hoist was invented in 1877 by Frederick Kope. Friction hoists are mounted on the ground above the mine shaft, or at the top of the headframe. Friction hoists utilize tail ropes and counterweight
Counterweight
A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides...
s and do not have the haulage rope fixed to the wheel, but instead passed around it. The tailropes and weights offset the need for the motor to overcome the weight of the conveyance and hoisting rope, thereby reducing the required horsepower
Horsepower
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...
of the hoisting motor by up to 30%, with the overall power consumption remaining the same. Friction hoists, unlike drum hoists, can and normally do use multiple ropes giving them a larger payload capacity, however since they require a larger safety factor, they are impractical for very deep shafts.
Advantages
New friction hoists are less expensive than new drum hoists, and the lead timeLead time
A lead time is the latency between the initiation and execution of a process. For example, the lead time between the placement of an order and delivery of a new car from a manufacturer may be anywhere from 2 weeks to 6 months...
for delivery may be shorter as there is more competition for manufacturing. Multi-rope friction hoists have a larger lift capacity than a drum hoist. A friction hoist is smaller in diameter than a drum hoist for the same service, making it easier to ship and install than a drum hoist.