Dorr-Oliver HydroSizers & MonoSizers

High efficiency classification, desliming and separation of impurities with Dorr-Oliver technology

Dorr-Oliver Type Hydrosizer
  • Overview

Hydrosizer - Multi-pocket classifier

  • Consistent product particle size distributions
  • Low space requirements
  • Low noise levels
  • Low energy costs
  • Ability to cope with feed flow variations below maximum
  • Easy adjustment when changing the feed particle size or when altering or cut-size to meet market requirements
  • Continuous operation and automatic control

FLSmidth offers the Dorr-Oliver® HydroSizer, a vertical current classifier for processing of screened raw sand in particles size ranges from 0 - 2mm. The HydroSizer is the heart of modern silica sand grading systems. The quality of the various particle size fractions is of paramount importance in glass, foundry, filter and other industrial sands. The Dorr-Oliver HydroSIzer meets these stringent quality criteria. High and consistent spearation efficiency, flexibility, and low operational and maintenance costs are among the major features of this unit.

The standard version of the HydroSizer has eight pockets for precisely grading the raw sand into eight particle size fractions in a single operation. Units with a greater or smaller number of pockets are used for special sand-grading tasks. In addition to classification, this system also provides intensive desliming. Clay, soil and organic impurities are drained off together with the HydroSizer overflow water.


Monosizer - Single-pocket classifier

  • Continuous, automatic operation
  • Low operating costs
  • High efficiency classification
  • High specific capacity

FLSmidth's Dorr-Oliver® MonoSizer is used for the separation of coal or of organic impurities, desliming, and classification in processing sand and other minerals.

The reason why the sysetm is so successful is that vertical upflow classification is systemetically effected using a hydraulically suspended fluid sand bed, created by the up-flow water. By employing this technique, the Dorr-Oliver MonoSizer achieves high troughput combined with high separation efficiency for classification and desliming.

Mode of operation

The Dorr-Oliver MonoSizer is a single-pocket system for high separation efficiency, resulitng in classification of the feed into two fractions. It is also used for the effective separation of organic impurities (coal, wood) from fine sand.

The raw material to be classified can be fed to the MOnoSizer either as wet slurry straight from the pit, or in the form of a thickened suspension. The optimum feed concentration is about 1000 g/l. The MonoSizer feed system ensures that the material is evenly distributed over the surface area of the pocket and is therefore entrained by the vertical water flow.