Metso Full portfolio Spiral dewaterers
Spiral dewaterers are optimal for dewatering of solids such as slag and mill scales. They are often used in mill scale treatment in continuous casting, hot rolling and scarfing, as well as in any other coarse material dewatering applications.
Decreased water consumption

Water is cleaned and recycled to plant

Reduced energy consumption

The simple, reliable design is able to handle large flows of effluents

Lower maintenance costs

Robust design has low service requirements and less wear on equipment

Easy to install and maintain

Delivered as a prefabricated unit with easy-to-replace parts

spiral dewaterer
Dewatering of slag and mill scales

Metso spiral dewaterer consists of an open trough with arrangements for collection of the products. 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 and the discharge launder for the dewatered material is easily adjusted between two positions, allowing alternative discharge into two separate bins.

The spiral dewaterers are able to handle large flows of effluents, offering a well dewatered mill scale product and a clear overflow (typically 100 ppm).

High flows and a low to moderate content of well defined solids like mill scales and slag are have proven to be optimal for the spiral dewaterers.

Robust design and reliable operation

The spiral dewaterer consists of an open tank for sedimentation of solids and a transportation spiral for removal and dewatering of the settled product.

The screw comes in two sizes depending on machine size and has optional single or double pitch depending on process requirements.

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 the bearing pack can be disassembled and replaced without lifting the spiral out of the tank.

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.

spiral dewaterer
spiral dewaterer
Easy to install and maintain

The spiral dewaterer is generally delivered as a prefabricated unit complete with stairs, handrails and platforms. The larger units may in some cases be delivered in parts for erection on site. 

Large pool area – for high flow applications

The large tank area enables taking high flows with limited solids content, applications very common for different industrial washing effluents.

With the addition of inclined plate packs in the tank this gives settling areas from 8 up to 100 m2 and flow rates up to 1600 m3/h.

Oil skimmer as option

In some applications the feed contains oil and grease. These are floating products reporting to the clear water overflow. A special designed oil skimmer can be supplied for removal of these floating products.

Service platforms

Optional service platforms and stairs can be provided to suit local conditions.

Inclined plate packs

In order to increase the sedimentation area of the tank, the spiral dewaterer can be supplied with plate packs. The plates are arranged in two steel frames, easy to remove if required.

Hydraulic spiral lifting device

If discharge of solids is intermittent whilst the feed is continuous, a hydraulic spiral lifting device can be supplied as an option.


The lower end bearing pack can be disassembled and replaced without lifting the spiral out of the tank. The upper end of the spiral is provided with lower end bearing pack can be disassembled and replaced without lifting the spiral out of the tank.

spiral dewaterer
spiral dewaterer

Metso SDC spiral dewaterers technical specifications

Spiral dewaterer series
Spiral dewaterer series
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