Plow-Ram Unit, Coal

a variant of a coal plow unit, which breaks up the coal seam by means of a ram that is held rigidly while striking the seam. The unit is used for the mining of very thin (usually 0.4–0.6 m), steeply inclined seams with fairly stable ground and overburden. The symmetrical ram moves up and down as it breaks up the coal. The plow-ram unit consists of the drive gear, terminal block, enclosed drive chain, and the ram itself. The coal separated from the body of the seam by the ram rolls into a haulage drift under the force of gravity.

Excavation of coal with a plow-ram unit may be carried out without erecting timbering if the rock of the roof descends evenly, or props may be set up periodically by hand after the face of the longwall has advanced 1–1.5 m. The best way for the ram to press against the coal, and the method usually used with a plow-ram unit, is to have the face set diagonally, leading the upper part of the longwall. Plow-ram mining is not widely used.