Aheadframe[1] (gallows frame,[2]winding tower,[3]hoist frame,[3]pit frame,[3]shafthead frame,[3]headgear,[3]headstock,poppethead) is the structure above an undergroundmine shaft, built for hoisting machines, people, and materials.[2]
Modern headframes are made of steel, concrete, or a combination of both. Timber headframes are no longer used inindustrialized countries, but are still used indeveloping countries. Conventionally, steel headframes are used fordrum hoists, and concrete headframes are built forfriction hoists; but a steel headframe can be used with a friction hoist for a shaft of smaller capacity and depth.[1]
A steel headframe is less expensive than a concrete headframe; the tallest steel headframe measures 87 m.[4] Steel headframes are more adaptable to modifications (making any construction errors easier to remedy), and are considerably lighter, requiring less substantial foundations. As steel headframes are easier to design, they have the potential to utilize "off the shelf" design tools. Construction of a steel headframe can be easily interrupted and restarted if necessary for statutory holidays or bad weather, whereslip forming concrete is not. Upon mine closure andmine reclamation a steel headframe is easier to demolish and may have value asscrap metal.[1]
A recently erected steel headgear in the Zambian copper belt town ofChililabombwe at the Konkola number 4 shaft has a total height of 81 metres to the top of the maintenance crane rail, with the centre-line of the head sheaves at 71 metres above the collar, making it the highest steel headgear in Africa.
Concrete headframes require less maintenance and are less susceptible to corrosion than steel headframes. There is much less waste of concrete during construction of a concrete headframe than there is of steel in construction of a steel headframe. Concrete headframes provide an enclosure upon construction, whereas steel headframes requirecladding and insulation to protect from weather. Concrete headframes are less susceptible to vibrations and sway less during high winds. Concrete is usually more readily available than steel (except in remote locations), and the price is predictable, whereas fabricated steel prices can be volatile.[1]
Headframes have become prominent features in historic mining regions. TheRuhr district of Germany and theSouth Wales Valleys in Britain are both examples of areas which are now associated with headframes due to the large number constructed tomine coal during theIndustrial Revolution. Most of these headframes have now been removed although both regions have turned non-operating mines with headframes into national museums; theGerman Mining Museum inBochum andBig Pit National Coal Museum inBlaenavon. Sporting teams from former coal mining regions such asLlanharan RFC andCilfynydd RFC have headframes included in their club badges.
In theUnited States, over a dozen headframes can still be seen around the town ofButte, Montana. Some of those headframes are illuminated at night with redLED lighting to commemorate Butte'scopper mining heritage, and the headframe is easily the town's most iconic image.
InYellowknife, Canada, the demolition of theCon Mine headframe has met significant public opposition.[5] The headframe was the tallest structure in the Northwest Territories[6] and is regarded by many in the town to be an important symbol of the region's mining heritage.
