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Wet Classification Equipment for Grinding Circuits
LIPU spiral classifiers are wet classification equipment used in mineral processing plants to separate fine particles from coarse particles according to their settling behavior in slurry.
They are commonly installed after a ball mill to form a closed grinding circuit. Fine particles leave with the overflow, while coarse particles settle to the bottom of the tank and are returned by the rotating spiral for further grinding.
LIPU spiral classifiers are available in high-weir and submerged designs, with single-spiral or double-spiral configurations for different capacities and classification requirements.
A spiral classifier separates solid particles in slurry according to differences in particle size, density and settling velocity.
After ground ore pulp enters the inclined tank:
This makes the spiral classifier especially useful for controlling particle size in grinding circuits.
Typical duties include:
The main classification types are high-weir and submerged spiral classifiers.
In a high-weir classifier, the overflow weir is positioned above the lower bearing center of the spiral shaft.
This configuration provides a relatively shallower classification zone and is generally used for coarser classification duties.
Typical applications include:
High-weir classifiers are widely used because of their simple structure and suitability for conventional grinding circuits.
In a submerged classifier, a larger portion of the spiral at the overflow end remains below the slurry surface.
This creates a deeper classification zone and provides more settling area for finer particle separation.
It is generally selected when:
The correct type should be selected according to the target overflow size, pulp conditions and grinding circuit requirements.
Spiral classifiers can also be divided into single-spiral and double-spiral configurations.
A single spiral is suitable for lower to medium processing capacities and applications where one spiral provides sufficient sand-return capacity.
Typical advantages include:
A double spiral uses two parallel spirals in a wider tank.
It is generally selected for:
The double-spiral design increases the effective solids conveying capacity without relying on a single larger spiral.
Spiral classifiers are mainly used for mineral slurry rather than directly processing large lump material.
Typical ores and mineral-processing applications include:
Typical application areas include:
In a typical beneficiation plant, the classifier is installed after the Ball Mill and before downstream separation equipment such as a Flotation Machine or Magnetic Separator.
A spiral classifier works by combining gravity settling with slow mechanical conveying.
The basic process is:
Stable operation depends on maintaining suitable slurry density, feed rate, spiral speed and overflow conditions.
A typical spiral classifier includes:
The spiral rotates slowly enough to transport settled solids without excessively disturbing the classification zone.
The lifting mechanism allows the spiral to be raised during shutdown or maintenance, helping prevent settled solids from locking the spiral.
One of the most important applications of a spiral classifier is forming a closed grinding circuit with a ball mill.
A typical process is:
Ball Mill → Spiral Classifier → Fine Overflow → Next Separation Stage
At the same time:
Spiral Classifier Coarse Sand → Return to Ball Mill
The classifier therefore performs two functions:
This prevents material that has not reached the target size from entering downstream beneficiation stages too early.
For example, in a flotation plant:
Ball Mill → Spiral Classifier → Flotation
In an iron ore magnetic separation plant:
Ball Mill → Spiral Classifier → Magnetic Separation
The efficiency of the classifier directly affects circulating load, grinding stability and downstream feed size.
| Model | Spiral Diameter | Spiral Speed (r/min) | Tank Length (mm) | Tank Width (mm) | Slope | Overflow Capacity (t/24h) | Returned Sand Capacity (t/24h) | Drive Motor (kW) | Lift Motor (kW) |
|---|---|---|---|---|---|---|---|---|---|
| FG-5 | Φ500 | 9.2 | 3900 | 560 | 10.5°–14° | 21–75 | 145–260 | 3 | — |
| FG-7 | Φ750 | 7.8 | 5367 | 830 | 10.5°–14° | 65–154 | 255–564 | 3 | — |
| FG-10 | Φ1000 | 7 | 6500 | 1110 | 10.5°–14° | 85 | 473–1026 | 5.5 | — |
| FG-12 | Φ1200 | 5 / 6 / 7 | 6500 | 1372 | 10.5°–14° | 150 | 1145–1600 | 5.5 | 2.2 |
| FG-15 | Φ1500 | 2.5 / 4 / 6 | 8265 | 1664 | 14°–18.5° | 235 | 1140–2740 | 7.5 | 2.2 |
| FG-20 | Φ2000 | 5.4 | 8400 | 2396 | 14.5°–18.5° | 400 | 5940 | 15 | 2.2 |
| FG-24 | Φ2400 | 3.6 / 5.4 / 6.3 | 9160 | 2600 | 14°–18.5° | 580 | 6800 | 11 / 15 | 2.2 |
| FG-30 | Φ3000 | 3.17 | 12500 | 3200 | 14°–18.5° | 890 | 11650 | 22 | 4 |
| 2FG-12 | Φ1200 | 5 / 6 / 7 | 6500 | 2620 | 10.5°–14° | 300 | 2290–3200 | 5.5 × 2 | 2.2 × 2 |
| 2FG-15 | Φ1500 | 2.5 / 4 / 6 | 8265 | 3200 | 14°–18.5° | 460 | 2240–5360 | 7.5 × 2 | 2.2 × 2 |
| 2FG-20 | Φ2000 | 5.4 | 8400 | 4296 | 14.5°–18.5° | 800 | 11880 | 15 × 2 | 2.2 × 2 |
| 2FG-24 | Φ2400 | 3.6 / 5.4 / 6.3 | 9160 | 5040 | 14°–18.5° | 1160 | 13600 | 11 × 2 / 15 × 2 | 2.2 × 2 |
| 2FG-30 | Φ3000 | 3.17 | 12500 | 6300 | 14°–18.5° | 1785 | 23300 | 22 × 2 | 4 × 2 |
Actual classification performance depends on ore characteristics, slurry density, feed particle-size distribution, spiral speed and operating conditions.
Overflow capacity and returned-sand capacity should be considered separately when selecting a classifier for a grinding circuit.
The classifier should be selected together with the grinding circuit rather than as an independent piece of equipment.
Important project information includes:
A high-weir classifier is generally preferred when the circuit requires relatively coarser classification and conventional sand return.
A submerged classifier is more suitable when finer classification and a deeper settling zone are required.
A double-spiral classifier should be considered when a single spiral does not provide enough processing or sand-return capacity.
For an existing grinding plant, classifier selection should also consider the ball mill discharge rate and the amount of circulating coarse material.
LIPU Heavy Industry provides grinding, classification and mineral separation equipment for complete beneficiation plants.
For spiral classifier projects, LIPU can assist with:
LIPU can also configure spiral classifiers as part of complete gold, iron ore, copper, lead-zinc and other mineral processing systems.
What is a spiral classifier mainly used for?
A spiral classifier is mainly used for wet particle classification in mineral processing plants. One of its most common applications is separating fine overflow from coarse return sand in a ball mill closed grinding circuit.
What is the difference between a high-weir and submerged spiral classifier?
A high-weir classifier is generally used for relatively coarser classification, while a submerged classifier provides a deeper classification zone and is better suited to finer classification requirements.
What is the difference between single and double spiral classifiers?
A single spiral uses one spiral shaft and is suitable for lower to medium capacities. A double spiral uses two parallel spirals and provides greater processing and sand-return capacity.
Can a spiral classifier work with a ball mill?
Yes. This is one of its main applications. Fine particles leave through the overflow, while coarse settled particles are returned to the ball mill for further grinding.
What information is required to select a spiral classifier?
Provide the ore type, ball mill model, grinding capacity, target particle size, slurry conditions and required sand-return capacity. These factors determine the classifier type, spiral diameter and single- or double-spiral configuration.
We provide a variety of mining and processing equipment, including feeders, rock crushers, grinders, classifying and screening machines, washing machines, gravity separators, flotation machines, magnetic separators, electric separators, dewatering equipment and laboratory mineral processing equipment.
