This review looks at the basic concepts of Headframes, including design considerations and different types of headframes used in mining industry along with the further recommended articles.
Headframes or headgears are structures present over the mine-shafts and are used to house the skips. It supports the hoists and is used to transport the workers and materials in and out of the underground mine. The headframes should be high enough to accommodate the sheaves and the skips comfortably. A canopy for the underground mines, headframes often provides a visual variety to the mine. It gives the distinctive look to the mine and thus is used as a symbolism for mines. Headframes are also known by different names like gallows frame, winding tower, hoist frame, pit frame, shaft-head frame, or headgear.
TYPES OF HEADFRAMES
Headframes are usually made of steel or concrete and are usually of two types:
- Headframes with back-legs: Usually made of steel, these structures can be A-frame, four post, six post, etc. A-frames headframes are supported by A-shaped backlegs, and four posts headframes are supported by four truss/backlegs. These types of headframes are very common in China, India and Africa.
- Headframes with Towers: This is one of the most common type of headframe used in North America and Australia. It basically consists of a tower which houses the sheave wheel. The towers are both made up of steel or concrete or both and are usually supported by a backleg truss.
A tower type headframe, McArthur River, Cameco
The selection of steel or concrete should be done prior to the headframe design based on the advantages and disadvantages of each. They can be compared on the basis of the foundations, construction, accommodation of shaft sinker, appurtenances, structural stiffness and damping effects, plant layout, adaptability to future changes and additions, reclamation, corrosion, durability and maintenance, aesthetics, and cost.
- Faster construction time
- Flexible design (Long spans of unsupported beams possible)
- Construction mostly unaffected by the weather condition
- The overall structure weighs much less than concrete
- Generally less expensive than concrete structures
- Better suited for temporary mines as steel headframes have resale value
- Prone to corrosion
- Open structures and hence needs covering if the headframes have to be used for material storage or habitation.
Steel headframe of Ottiliae shaft; Clausthal-Zellerfeld, Lower Saxony, Germany. This is the oldest still existing headframe in Germany, build in 1876 (Source: Wikipedia)
- More stable than steel under mechanical vibrations
- The structures can be used for storing materials or habitation
- Visually more appealing than the steel structures
- Not prone to corrosion
- Longer construction time
- Construction mostly affected by the weather condition as adequate time is required for curing
- Generally more expensive than steel structures
- Doesn't have resale value
Concrete Headgear at the Finsch Diamond Mine
One of the tallest concrete headgear is at 16 shaft at Impala Platinum Mine in South Africa. This 1900 t structure is 87 m high.
Both steel and concrete headframes have associated advantages and disadvantages to their use. A comparison between the two is mentioned below:
|Less expensive than concrete head frame
|More adaptable to modifications on any constructional errors
|Lighter and require less substantial foundations
|Construction of steel headframe can easily be interrupted and restarted if necessary for statutory holidays or bad weather
|Easy to demolish in case of mine closure and may have scrap value
||Difficult to demolish and will give no scrap values
||Require lesser maintenance than steel headframe
||Less susceptible to corrosion
|It requires cladding and insulation to protect from weather
||It provides an enclosure upon construction
||Less susceptible to vibrations and sway less in high winds
|Use: Traditionally used when a drum hoist is employed
||Use: traditionally used when a friction hoist is employed
The headframes should be designed to withstand the overall loading of the hoisting frame with suitable safety margin. Various factors affect the design of the headframe such as the type of hoist used, the ground conditions, the estimated lifespan of the mine (temporary or permanent headframe), geographical limitations, etc.
The support design and structural engineering of a headframe are based on mine capacity, product, material weight, the depth of the shaft, speed of production and volume produced and several other determining factors.
The specific final design of the headframe needs to involve (SME) consideration of the hoisting system, including:
- Mine Services
- Sinking Provisions
- Equipment Monitoring Facilities
- Heating and Ventilation
- Additional Mining Regulations
(Edwards, Hoisting Systems, 1992)
G. L. Tiley & Associates Ltd. lists the following tasks involved in headframe layout & design:
- Hoisting plant general arrangements are produced for feasibility and final designs
- Headframes are modeled with a finite element analysis program and designed for working and rope breaking loads
- Hydraulic dumps or scroll plate supports are designed
- Rope changing procedures and handling equipment are provided
Interested readers are advised to read Hoisting Systems for more details
The structural engineer designs the headgear. Here is a typical ad for such a person:
Wardrop is seeking an extremely experienced structural engineer. The ideal individual would have 20+ years of experience in the design of heavy industrial structures (steel, concrete, wood, masonry), preferably in the mining and mineral processing industry. Experience with process plant, headframe structures, shaft steel and underground steel and concrete structures, is required. This role is envisioned to be a senior technical position, providing technical leadership, mentoring, guidance and design review / peer review of the structural work of the department.
InfoMine has job listings for positions as a Structural Engineer & Shaft Engineer.
Siemag Iceberg: They are involved in the planning, design and construction of complete systems in the areas of shaft hoisting systems.
G. L. Tiley & Associates Ltd. : They perform all tasks involved in the process of headframe construction starting from the engineering and feasibility study to final construction and future maintenance.
Ocean Steel & Construction Limited: They are involved in construction of headframes and other structural engineering and construction work. An example is the concrete headframe built at Picadilly Mine.
Leedem Mine Services: They are involved in making Shaft sinking structures.
Dynatec: Much information about their services including contract mining from shaft sinking to operations. I like this picture of a headgear from their site.
Redpath: A deep black and red overwhelms the screen of this website. Pretty appropriate to the statement that Redpath is "recognized the world over as a leader in shaft sinking." Found nothing about headgears though so I will have to trust my colleague.
Shaft Sinkers: located in South Africa
SNC Lavalin: Involved in headgears construction in Canada
The books and magazines with information on hoists are the main source for the information about headframes. Please see the list of books and magazines in the Hoists technology review
Here are some other publications which provide some information regarding headframes:
- 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 Most Modern Shafts : A 97m tall (approx. 31-storey) reinforced concrete headframe built at Oyu Tolgi's mine.
- Service Hoist system: Frontier-Kemper Constructors
- Design guidelines for construction of friction winders
- Record-breaking steel headgear at Gold Fields' South Deep
There is no recent development in the field of headframes. The construction and the material used are all the same (no change). The International Conference on Hoisting and Hauling organized by SME will be the most probable stage for the discussion on the recent developments.
- A Pictorial Walk Through the 20th Century, Mine Safety and Health Administration.
- D. W. Butler, and A. C. Schneyderberg, "Headframe selection - steel vs. concrete", Mining Congress Journal, Ref 7, 15-9, Jan 1982.
- F. A. Edwards, "Hoisting systems", SME Mining engineering handbook, Society for Mining, Metallurgy, and Exploration, Volume 2, 1992.
- G. L. Tiley & Associates Ltd
- Hoisting Systems
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