Abstract: Respirable dust particles in air are reduced by spraying with water from high pressure spray nozzles. The removal of particles in the size range most likely to cause pathological damage is enhanced by addition of a surfactant to the spray water.

Abstract: Boreholes are drilled at an angle from gate roads to the working face in a longwall mining operation, and air is exhausted from the working face area through the boreholes. Additional boreholes, parallel to the first boreholes, are drilled from the gate roads into the longwall pillar, and as the face moves through the pillar it intersects the additional boreholes, and dust-laden air is exhausted through the additional boreholes.

Abstract: A variable diameter drill rod stabilizer including an inner piston having cam surfaces which bear against wall engaging segments. Movement of the piston axially within a drill rod section by differential pressure of a fluid flowing through a passage in the piston moves the wall engaging segments radially and controls the diameter of the stabilizer.

Abstract: Mineable coal seams which are in proximity to an overlying or underlying coal seam are degasified in advance of and during mining by drilling a generally horizontal borehole in the overlying or underlying coal seam and producing gas therefrom.

Abstract: A drilling fluid circulation system for containing drilling cuttings, gas and drilling fluid in a closed loop. The system includes a separator having two sealed compartments, one for settling out drilling cuttings and one for holding clean drilling fluid. A fine solids separator is provided between the two compartments, and a gas exhaust line for conducting gas released from the returning drilling fluid is provided to conduct the produced gas to a safe location away from the working area. A solids discharge device is provided for removing settled drilling cuttings.