commercial coal as well as to crush down existing coal lumps to acceptable sizes. The Roller Screen Crusher includes dust encapsulation, pre-screen, two crusher drums and after-screen. A pre-crusher might be necessary to put on top of the pre-screen if many lumps are present (e.g. frozen coal). The crusher drums have a releasing mechanism to HDS Hammer Crusher. Double-shaft hammer crushers are mainly used in the cement industry for the comminution of soft to medium-hard, but also moist and tough materials Limestone, gypsum, chalk, clay and marl, as well as lignite and pit coal. The crushing of the feed material is effected by percussion, impact and shear forces. Equipment. Equipment.