Metso's spiral dewaterer consists basically of an open trough with arrangements for collection of the products. The inlet flow is evenly spread out by means of a feed distributor. Coarse material settles and is continuously removed by means of the transport spiral. The material will be dewatered by drainage in the upper part of the spiral before discharge. The discharge launder for the dewatered material is easily adjusted between two positions, allowing alternative discharge into two separate bins. The clarified water passes an overflow weir which is adjusted at start-up to give even distribution of flow over the full width of the trough. A baffle plate will prevent floating materials from being drawn by the clarified water discharge.