A conveyor bridge is a piece of
mining equipment used in
strip mining for the removal of
overburden and for dumping it on the inner spoil bank of the open-cut mine. It is used together with multibucket excavators, frequently
bucket chain excavator
A bucket chain excavator (BCE) is a piece of heavy equipment used in surface mining and dredging. BCEs use buckets on a revolving chain to remove large quantities of material. They are similar to bucket-wheel excavators and trenchers. Bucket cha ...
s, that remove the overburden which is moved to the bridge by connecting conveyors. Conveyor bridges are used in working horizontally layered deposits with soft overburden rock in areas where mean annual temperatures are above freezing. They are frequently used in
lignite
Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...
mining.
Setup
A conveyor bridge consists of girders resting on two or three supports mounted on rails, or sometimes on crawler tracks. The bridge is set across the pit and moves along the mining face at a few metres per minute. If it runs on rails, the tracks are shifted in accordance with the progress of the mining. The rock is moved from the excavator to the bridge by connecting conveyors. The dumping support of a conveyor bridge may rest on the soil of the seam or on a dumping mound specially poured and packed by the bridge itself, depending on the stability of the rock.
History and examples
The first conveyor bridge was built in
Plessa
Plessa ( dsb, Plesow) is a municipality in the Elbe-Elster district, in Brandenburg, Germany.
Following a redrawing of local boundaries which took effect on 31 December 2001, the municipality includes two additional settlements, and therefore now ...
lignite mine ''Agnes'' according to plans of mine director
Friedrich von Delius Friedrich may refer to:
Names
*Friedrich (surname), people with the surname ''Friedrich''
*Friedrich (given name), people with the given name ''Friedrich''
Other
*Friedrich (board game), a board game about Frederick the Great and the Seven Years' ...
. It was scrapped in 1959 after exposure of clay beds made mining in the pit unsafe.
A large conveyor bridge with 200 m span and 50 m height, fed by a
bucket-wheel excavator, was completed in 1930 in the
Böhlen lignite mine. After it was toppled by a storm in 1937, a replacement went into service in 1939.
The conveyor bridge of
Espenhain lignite mine with a total length of 545 m, which started operation in 1944, could remove an overburden of 45 m thickness.
Between 1969 and 1991,
TAKRAF built five very large conveyor bridges of the type
F60 of which four are still in operation in lignite mines in
Lower Lusatia, and one has been preserved as a visitor attraction. These were constructed for removing overburden up to 60 m thick, are 502 m long and span 204 m.
They could move originally up to 23000 m
3/h, with additional excavators up to 34600 m
3/h.
References
{{Authority control
Mining equipment
Engineering vehicles
Surface mining