Longwall shearers mount over an armored face conveyor (AFC) to cut away the face of a coal seam in longwall mining operations. They are an essential piece of mining equipment in longwall mining, a type of mining where aggregate is extracted in approximate sections of 1 m x 200 m x 3-4 km.
Longwall shearers consist of large cutting drums mounted to a slim body. The cutting drums are used to cut a predetermined height of coal across the face of the coal seam on each pass. The shearer loader can be divided into three basic types.
- Double-ended ranging drum shearers (DERS) are the largest and most efficient type of shearer loader. The double-ended machine includes two cutting drums mounted on ranging arms that can be positioned to accommodate a range of seam thicknesses.
- Single-ended ranging drum shearers (SERS) consist of a single cutting drum mounted to a single raging arm. Typically two SERS are used simultaneously to cut away the face of a coal seam.
- Single-ended fixed drum shearer (SEFS) like SERS are also typically used in pairs but lack a ranging arm and are used to extract thin coal seams approximately 48 inches thick.
A pass from the shearer results in a cavernous void below the overburden known as a goaf. The hydraulic supports temporarily uphold the coalface ceiling until it can safely collapse.
(Image credit: Kopex)