TY - JOUR TI - Causes of coal degradation at working faces AB - Coal comminution by shearer loaders at working faces and factors influencing it are analyzed. Three groups of factors are evaluated: coal mechanical properties, design and specifications of shearer loaders and mining schemes. On the basis of analyses, recommendations for increasing proportion of coarse coal and reducing coal comminution in underground coal mines in Poland are made. Increasing output of coarse coal in coal seams with a high proportion of dull coal is most economic. Increasing power of drive systems for shearer loaders to 500 kW or more decisively influences grain size distribution of coal and increases proportion of coarse coal, especially in seams of dull coal. Gradually increasing cutting depth of a shearer loader negatively influences haulage speed and coarse coal output. Replacing gradual cutting depth increase by attack at the full cutting depth increases proportion of coarse coal. When medium or thick coal seams are mined a coal bench from 0.3 to 0.5 m thick should be left in the roof or between 2 benches cut by 2 cutting drums. The coal bench left in the face disintegrates under the influence of gravity and the proportion of coarse coal increases. Optimizing yield strength of powered supports at a working face is a further method for improving grain size distribution of coal and increasing proportion of coarse coal. 2 references. AU - "Sikora, W" KW - "01 COAL, LIGNITE, AND PEAT" KW - "COAL" KW - "COMMINUTION" KW - "POWERED SUPPORTS" KW - "YIELD STRENGTH" KW - "SHEARER LOADERS" KW - "DESIGN" KW - "OPERATION" KW - "COAL MINING" KW - "CORRELATIONS" KW - "CUTTING" KW - "LONGWALL MINING" KW - "OPTIMIZATION" KW - "PARTICLE SIZE" KW - "PHYSICAL PROPERTIES" KW - "RECOMMENDATIONS" KW - "UNDERGROUND MINING" KW - "CARBONACEOUS MATERIALS" KW - "CUTTER LOADERS" KW - "CUTTING MACHINES" KW - "ENERGY SOURCES" KW - "EQUIPMENT" KW - "FOSSIL FUELS" KW - "FUELS" KW - "HAULAGE EQUIPMENT" KW - "LOADERS" KW - "MACHINING" KW - "MATERIALS" KW - "MATERIALS HANDLING EQUIPMENT" KW - "MECHANICAL PROPERTIES" KW - "MECHANICAL STRUCTURES" KW - "MINING" KW - "MINING EQUIPMENT" KW - "SIZE" KW - "SUPPORTS" KW - "012000* - Coal, Lignite, & Peat- Mining" DO - https://doi.org/ UR - PB - CY - Poland PY - 1985 DA - 1985-01-01 LA - Polish J2 - [] VL - 130 C1 - C2 - C3 - C4 - C5 - L3 - Journal Name: Zesz. Nauk. Politech. Slask., Gorn.; (Poland); Journal Volume: 130 ER -