KREBS Coal Spirals Efficient separation, simpler circuits and better control. We know these are goals you strive to achieve in your coal preparation plants. Our spirals are simple in theory and work efficiently Spiral coal concentrators use the specific gravity of materials with different densities to separate coal, and produce a low-ash coal product at high efficiency. Our high-performance Coal Spirals deliver a feed capacity of 2 STPH to 3 STPH (1.8 mtph to 2.7 mtph) per start, dependent on raw coal quality and refuse amount to be discarded. Optimum spiral feed size is -1 mm to 0.15 mm (14 M x 100 M) Constructed of wear- and corrosion-resistant materials, choose from single-, double- and triple-start configurations. Our comprehensive range of spiral units also include single-pass or rougher/cleaner compound designs that allow rewashing of coal in a second-stage spiral helix that is immediately following the primary spiral.