Spiral Classifier: Importance & Types

Published time:27 September 2023

The spiral classifier is a commonly used equipment for mineral processing (sand washing). It is often paired with a ball mill to form a closed-circuit circulation to divert ore. It is also used in gravity concentrators to classify ore and fine mud, ore slurry in metal mineral processing processes, particle size classification, desliming, dehydration, and other operations in mineral washing operations. It has a long longitudinal axis installed in an inclined semicircular groove. Rotating blades are installed on the axis. The upper transmission mechanism drives the rotation. There is a spiral lifting device at the lower part.

The spiral classifier relies on the principle that the solid particles have different sizes and specific gravity and have different settling speeds in the liquid. The fine ore particles float in the water and overflow, while the coarse ore particles sink to the bottom of the tank and are pushed to the upper part by the spiral and discharged. A device for mechanical grading. It can filter the powder ground out of the mill, screw the coarse material into the feed port using a spiral blade and discharge the filtered fine material from the overflow pipe.

spiral classifier

Importance of Spiral Classifier in Mineral Dressing

The spiral classifiers are a fundamental component of mineral dressing operations, and they help in achieving the desired product quality and recovery rates. Their ability to classify and separate particles based on size and density is crucial for the efficient and cost-effective extraction and processing of valuable minerals from ore. The importance of spiral classifiers in mineral processing is shown in the following:

  • Particle Size Classification: Separating particles of different sizes is often necessary in mineral processing. Spiral classifiers classify particles based on their size, ensuring that the desired particle size range is achieved in downstream processes. It is essential in ore grinding and beneficiation processes, where the particle size distribution can significantly impact the efficiency of subsequent operations.
  • Dewatering: Spiral classifiers dewater or remove excess water from mineral slurries. Settling and separating particles, help concentrate the valuable minerals and reduce the final product’s water content. It is essential for efficient transportation and further processing.
  • Desliming: In some mineral processing applications, especially when dealing with fine-grained ores, removing fine particles or “slimes” from the ore slurry is essential. Spiral classifiers are used for desliming, ensuring that these fine particles do not interfere with subsequent processes like flotation or gravity separation.
  • Density Separation: Spiral classifiers can also separate particles based on their density. It is essential in processes like gravity concentration, where denser minerals are separated from lighter gangue materials.
  • Process Efficiency: Proper classification and separation of particles using spiral classifiers improve the overall efficiency of mineral processing operations. By optimizing particle size and concentration, it can maximize the yield of valuable minerals while minimizing waste and energy consumption.


Spiral Classifier Types

A spiral classifier is referred to as a classifier. There are four main classifiers: high dam single spiral and double spiral classifiers and submerged single spiral and double spiral classifiers. We will introduce it from the spiral position and the number of spirals.

  • Spiral Position

The main component of the spiral classifier is the spiral. According to its position in the tank and the level of the slurry surface, it can be divided into three types: low dam, high dam, and submerged spiral classifiers. The low dam spiral classifier is rarely used now; the high dam and submerged spiral classifiers are mainly used.

1. Low Dam Spiral Classifier

Since there are few applications now, here is a brief introduction. The low dam type is that the overflow dam is lower than the screw axis of the screw. Due to the small area of the settling area, it can only be used for washing sand ores with little mud and dewatering of coarse particles in actual production, but it is rarely used in grinding cycles.

2. High Dam Spiral Classifier

The high dam type spiral classifier means that the overflow dam is higher than the spiral axis of the spiral but lower than the upper edge of the spiral at the overflow end. There are high dam type single spiral and double spiral classifications. This kind of classifier has a lower settlement area and a larger dam type, and its dam height can be adjusted within a certain range. That is, the area of the settlement area can be adjusted and changed within a certain range so that the particle size of classification can be adjusted, which is an important part and a commonly used device of the grinding cycle. It is mainly used for ore classification with overflow particle size of 0.83mm to 0.15mm.

3. Submerged Spiral Classifier

The submerged type is 4-5 spiral blades at the end of the overflow dam, all submerged in the pulp. There are also two types of single spiral and double spiral. The classifier has a large settlement area, and a deep classification pool, and the spiral agitation has little effect on the surface of the pulp. Hence, the classification surface is stable, and the overflow is large and fine. It is used for ore classification with an overflow particle size of 0.15mm to 0.07mm. The submerged spiral classifier is often used as classification equipment for fine or secondary grinding in mineral processing plants.


  • Number of Spirals

It divides spiral classifiers into single-spiral and Duplex Spiral classifiers according to the number of spirals. The classification performance of the two is the same, but the double screw classifier has a larger processing capacity and is suitable for use with large grinding machines. The specifications of the spiral classifier are expressed in terms of spiral diameter.


duplex spiral classifier


The spiral classifier is a commonly used solid particle classification equipment to classify and separate materials according to particle size. It has a simple structure, reliable operation, and convenient function. You can contact us for parameters and quotations if you need a spiral classifier.

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