FG & FC Series Spiral Classifier for Grinding Circuit Classification

The FG & FC Series Spiral Classifier is a mechanical classification device based on the principle of differential settling velocity of solid particles in liquid. It classifies materials by gravity sedimentation and continuously returns coarse particles through a rotating spiral mechanism. This equipment is widely used in mineral processing plants, where it forms a closed grinding circuit together with ball mills.

Known for its reliable structure, stable operation, low return sand moisture content, and convenient gravity connection with ball mills, the FG & FC Series Spiral Classifier remains an indispensable classification solution in many mineral processing flows. Through continuous spiral rotation, the classifier agitates and washes the slurry, mechanically lifts settled coarse particles (return sand) back to the mill, and allows fine particles (overflow) to discharge with the water flow.

In applications involving coarse particle classification, stable return sand concentration, and gravity separation processes, spiral classifiers still play an irreplaceable role. They remain a key classification device in mineral beneficiation systems where process stability and simplicity are prioritized.

According to spiral configuration and working conditions, the FG & FC Series can be classified as follows:

Single Spiral and Double Spiral Classifier
Selected based on required processing capacity and plant layout.

High Weir Spiral Classifier
Suitable for materials with overflow particle size typically between 0.83 mm and 0.15 mm. Commonly used for ore classification and sand washing applications.

Submerged Spiral Classifier
Designed for finer materials with particle sizes ranging from 0.15 mm to 0.07 mm. Widely used for fine ore and powder classification.

The spiral classifier mainly consists of an inclined tank and an internal spiral mechanism.

Tank (Water Trough)

The tank is a long, inclined trough with a semi-cylindrical bottom. The high end is equipped with an overflow weir, while the low end serves as the return sand discharge outlet. The inclination angle of the tank can be adjusted to meet different classification size requirements.

Spiral Assembly

This is the core working component of the classifier. It consists of a main shaft, support structure, and spiral blades. The spiral blades are continuously welded onto the support and are responsible for slurry agitation and mechanical lifting of the return sand.

Drive System

Usually installed at the high end of the tank, the drive system includes an electric motor and gearbox, driving the spiral shaft at low rotational speed to ensure stable classification performance.

Lifting Mechanism

An electric or manual lifting mechanism is installed at the high end of the classifier. It allows the spiral to be lifted during shutdown, facilitating equipment startup and maintenance operations.

Lower Support and Bearing Assembly

A support base and lower bearing are installed at the low end of the tank to support the lower end of the spiral shaft and ensure smooth operation.

Metallic Mineral Processing

Used in primary grinding-classification circuits where coarse particle size (typically overflow fineness >0.15 mm) and stable return sand are required.

Gravity Separation Plants (e.g. Tungsten, Tin)

Installed upstream of shaking tables and other gravity separation equipment. Stable overflow concentration and particle size are critical for gravity separation efficiency.

Ore Washing and Desliming

Utilized for washing sticky ores and removing fine slimes by taking advantage of the agitation and overflow characteristics.

Non-Metallic Mineral Processing

Applied in wet classification and washing of materials such as quartz sand and feldspar.

Building Materials Industry

Used for wet classification of certain cement raw materials and fillers.

Applicable Materials

Suitable for ores and raw materials that require classification in slurry form. The equipment demonstrates good adaptability to fluctuations in feed concentration and particle size.

Low Return Sand Moisture Content

Mechanically lifted return sand undergoes natural dewatering, achieving high solid concentration (typically 70%–80%). This allows direct return to the ball mill, stabilizing grinding concentration and improving grinding efficiency.

Stable and Reliable Classification

Compared with hydrocyclones, spiral classifiers are less sensitive to fluctuations in feed rate and slurry concentration. Operation and control are straightforward, without the need for complex pressure control systems.

Easy Gravity Connection with Ball Mills

The return sand outlet is located at the lower end of the classifier, enabling gravity flow back to the mill. This simplifies process layout, reduces energy consumption, and eliminates the need for slurry pumps.

Combined Agitation and Washing Function

The rotating spiral provides agitation, allowing washing and desliming during classification. This is especially beneficial in high weir and submerged classifiers for removing fine clay or soluble salts.

Durable Structure and Low Maintenance Cost

With a simple mechanical structure, the main wear parts are concentrated in the lower spiral blades. Maintenance workload is relatively low, and overall operating costs are economical.