This review looks at the basic concepts of hoists, including their types, principle, and usage. It also tells the safety regulation in different countries, applications in Mines, suppliers and further recommended articles.
Hoist by definition means to haul or to raise an object to higher altitudes. Hoists are mechanical or electromechanical devices used to move an object from one point to another, which would be otherwise physically challenging. The object can be raised, lowered or moved depending on the necessity. The hoist work on the basic principle of balance of forces where an equal and opposite force is applied on the load force. The applied force can be reduced by using a pulley system.
The hoist technology is believed to originate from the lever system where a large force can be countered using small force by proper placement of the fulcrum. The block and tackle pulley invented by Archimedes allowed sailors to move heavy objects with ease that would otherwise be very difficult. This invention is considered as a precursor to the modern hoist technology.
TYPES OF HOIST
The hoists can be classified based on the lifting medium, and the source of powering the hoist.
- Manual: The load is hoisted using manual operation. It is the oldest type of hoist where humans, and animals where used to haul the loads. Such schemes where used during ancient period for the construction of buildings. Nowadays these hoists are used to lift light loads.
- Electric: Electric power is used to hoist the load. This technology overtook the manual operation during the industrial development. Such hoists are faster and more powerful and thus forms a huge percentage of the hoists used in the industries.
- Pneumatic: The powering of these hoists is through pneumatic medium. Compressed air is used to run the motor or the engine to deliver a lifting torque. These hoists have an advantage of being lighter, safer and use less energy to do the same task.
- Chain: Utilizes link or roller chain as its lifting medium.
- Wire rope: Utilizes wire rope as the lifting medium
- Strap: Utilizes polyester or nylon straps as the lifting medium
The hoist can be further classified into drum, friction, and Blair multi-rope type.
Drum type: In Drum type hoisting devices, the lifting medium is continuously wrapped around a drum. Unlike the friction type where the load is directly hoisted from the top, in drum type hoist the pulling mechanism is connected to a drum, which is to the other side of load across the headframe and sheaves. The headframe and sheaves are required to center the hoisting medium in the shaft compartment. Drum hoists are the most common hoists used in North America, South Africa and South America. They also require the least amount of maintenance among all hoist types.
a. Single drum: In a single drum hoist, a rope is attached to a drum and wound and is used to hoist the load through an overhead pulley. Single drum hoists are found to be more efficient than double drum hoists for most of the applications.
b. Double drum hoist: In a double drum hoist, a rope is wound around two drums instead of one. Double drum hoists are preferred for lift systems with multiple hoists.
You can find more information about drum hoists at this link
Friction (Koepe) type: Unlike drum hoists, friction hoists are economic options for shallow shafts. They are mounted right above the mine shaft or at the top of headframe, thus requiring less space than drum hoists. The lifting medium is passed over a pulley with the load connected to the one end of the lifting medium. The friction between the pulley and the lifting medium aids the hoisting. The friction between the pulley and the lifting medium prevents the load from sliding in the opposite direction when the weight is pulled up using gears and pulleys. Developed by Frederick Koepe in 1877, the lifting medium is not wound on a drum, and hence multiple hoists can be used near to each other. Friction hoists require more routine maintenance than drum hoists and are not suitable for hoisting from multiple loading pockets on different horizons within a shaft.
Blair multi-rope type: The Blair multi-rope hoist system is used for accessing much deeper mines and can be found in many of the world's deeper mines, such as in South Africa. One of the mines that uses this type is the Moab Khotsong Mine where it is used up to 3,150m. It has a capacity to access a depth of up to 5,000m.
For more illustrations of hoist types, see http://en.wikipedia.org/wiki/Hoist_(mining).
Different options are available for the hoists based on various combinations of the lifting medium and the powering source.
- Air hoist: Powered by pneumatically driven motors and uses chain or wire rope as its lifting medium.
- Air chain hoist: Powered by pneumatically driven machinery unit that utilizes a chain as its lifting medium.
- Air wire rope hoist: Powered by pneumatically driven machinery unit that utilizes wire rope as its lifting medium.
- Lever hoist: Manually powered using a lever hoist to lift, lower, or pull a load and works on the principle of ratchet and pawl mechanism.
- Ratchet and pawl hoist: A mechanical device that permits motion in one direction only and is usually a wheel with slanting teeth.
- Ratchet lever hoist: Manual device utilizing lever to lift, lower, or pull a load and to apply or release tension based on ratchet and pawl mechanism.
- Trolley hoist: A trolley hoist is a hoist suspended from a trolley. A hoist can be connected to a trolley by hook or clevis, or a hoist can be integral with the trolley.
STANDARDS AND SAFETY REGULATIONS
There are many different standards regulating the hoist technology. These standards depend on which country the hoist is used in. These standards set guidelines to be followed for a safe operation of the hoist. Some of the societies that sets the standards for the hoist operation are listed here, however the readers are welcomed to check the standards relevant to them before using the hoist.
- American Society of Mechanical Engineers
- International Organization for Standardization
- British Standards Institution
- Deutsches Institut für Normung
- European Committee for Standardization
- Federation Europeenne de la Manutention
The best site for information on mine hoist safety is MSHA's. See their papers on Mine Hoist and Elevator Safety
USAGE IN MINES
In mines hoist are generally used in transportation to and from the underground mines. As very high power hoist controlled operation is required, generally electric hoist driven by frequency controller are used for precise movement of the hoist. The hoist can be either drum type or friction type. There are various arrangements for drum type hoists.
1. Single Drum Unbalanced hoisting: These types of hoists are generally used for single hoists. These hoists can be expensive if the hoists are to be used for greater depths as high torque motors and high tension lifting mediums will have to be used.
2. Single Drum Balanced hoisting: These hoists provide a cheaper option by reducing the need of high torque motors and high tension lifting mediums. In balanced hoisting, the hoisted load is balanced by counterweight. It is mostly used for single level hoisting.
3. Divided Single Drum: This can be used for multi-level hoisting with multiple hoists.
4. Split Differential Diameter Drum: Split differential diameter drums are used for reducing the problems of rope adjustment, which is often faced in the divided single drum. Here one drum with smaller diameter than the main drum is used to balance the hoist.
5. Double Drum, One Drum Clutched: This type of hoists helps in making quick adjustments to the lifting medium. These hoists can be efficiently used for multilevel operation.
6. Double Drum, One Drum Clutched: This type of has all the advantages of one drum clutched with an extra capability of having an uninterrupted hoisting even is the counter apartment is under repairs.
7. Multiple Drum, Blair Type: The conveyances are attached with two lifting medium instead of one which is coiled on a drum. The advantage of this type of hoist is that much thinner lifting medium and smaller drums can be used.
Based on Material Handling Society of America some of the hoist suppliers can be listed as:
- Acco Material Handling Solutions
- Columbus McKinnon Corporation
- Chester Hoist
- Demag Cranes & Components Corporation
- Electrolift Inc.
- Ingersoll Rand Company
- Harrington Hoists Inc.
- J.D. Neuhaus
- R&M Materials Handling, Inc.
- STAHL CraneSystems, Inc.
For a wider list of hoist suppliers around the globe click here.
A hoist system serves as the chief part of an underground mine and safety is the top priority here. Opportunities directly associated with hoists include hoistman, hoist mechanic, electrician and hoist engineer. A hoistman at McArthur River mine not only monitors the hoisting system but also handles any emergency calls at the location.
Here is the job description for a mine hoist installer, repairman, operator, and/or mechanic in Canada.
Perform some or all of the following duties:
- Read blueprints, diagrams and schematic drawings to determine work procedures
- Install, align, dismantle and move stationary industrial machinery and mechanical equipment, such as pumps, fans, tanks, conveyors, furnaces and generators according to layout plans using hand and power tools
- Operate hoisting and lifting devices such as cranes, jacks and tractors to position machinery and parts during the installation, set-up and repair of machinery
- Inspect and examine machinery and equipment to detect and investigate irregularities and malfunctions
- Install, troubleshoot and maintain power transmission, vacuum, hydraulic and pneumatic systems, and programmable logic controls
- Adjust machinery and repair or replace defective parts
- Operate machine tools such as lathes and grinders to fabricate parts required during overhaul, maintenance or set-up of machinery
- Clean, lubricate and perform other routine maintenance work on machinery
- Construct foundations for machinery or direct other workers to construct foundations
- Assemble machinery and equipment prior to installation using hand and power tools and welding equipment.
- Completion of secondary school is usually required.
- Completion of a three- to four-year apprenticeship program
A combination of over five years of work experience in the trade and some high school, college or industry courses in industrial machinery repair or millwrighting is usually required to be eligible for trade certification.
- Industrial mechanic trade certification is compulsory in Quebec and available, but voluntary, in all other provinces and territories.
- Construction millwright trade certification is available, but voluntary, in Ontario.
- Interprovincial trade certification (Red Seal) is also available to qualified industrial mechanics or millwrights.
BOOKS AND MAGAZINES
Here are some publications with more information about hoists;
- Hoist and Haul 2010: Proceedings of the International Conference on Hoisting and Hauling
- Machine design: Hoists, Derricks and Cranes by H D Hess
- Hoists, Cranes and Derricks by H S Zim
The following books also provide some information regarding hoist technology:
- H. L. Hartman, and J. M. Mutmansky, "Introductory mining engineering", John Wiley and Sons.
- H. L. Hartman, S. G. Britton, J. M. Mutmansky, "SME Mining engineering handbook", Society for Mining, Metallurgy, and Exploration
The International Conference on Hoisting and Hauling
organized by the SME is very informative regarding the recent developments and major research areas.
- H. L. Hartman, S. G. Britton, J. M. Mutmansky, SME Mining engineering handbook, Society for Mining, Metallurgy, and Exploration, Vol. 2, 1992.
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