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 a V-notched 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.

The spiral dewaterer is suitable for:

• Mill scale treatment in continuous casting, hot rolling and scarfing

Main benefits of Metso's spiral dewaterers are:

• Washing effluents coming from the steel industry with high flows and a low to moderate content of well defined solids like mill scales and slag has been proven optimal for the spiral dewaterer
• In the sedimentation tank the wash water is reclaimed and sent back to the washing operation again
• The solids are removed by and dewatered in the discharge spiral and can be sent to recycling if this is considered of value

Main features of Metso's spiral dewaterers are:

• Like the spiral classifier the spiral dewaterer consists basically of an open tank for sedimentation of solids and a transportation spiral for removal and dewatering of the settled product.
• All machines have equal spiral diameter, 600 mm.
• The spiral flights are welded directly to the spiral shaft. The flight wear shoes are made of high chrome iron and are bolted to the flights.
• The submerged bearing assembly is of grease purged type and is lubricated every second week.
• The bearing pack can be disassembled and replaced without lifting the spiral out of the tank.
• Hydraulic spiral lifting device can be supplied as an option.
• The drive consists of an electric motor, V-rope drive and speed reducer for reliable operation at low spiral speeds needed for low wear and improved dewatering.