Spiral Classifier

Key Advantages

Reliable Closed-Circuit Classification, Stable Sand Return

The Spiral Classifier provides continuous, stable separation of oversize sand particles from correctly ground fines in closed-circuit ball mill grinding systems, returning a consistent volume of sand to the mill feed at a stable density and particle size distribution. This stable sand return maintains the mill at its optimum grinding load, preventing both underloading — which reduces grinding efficiency — and overloading — which causes mill spills and circuit instability — ensuring maximum grinding circuit throughput and energy efficiency throughout 24-hour continuous operation.

High-Weir & Submerged Type for Different Classification Duties

The high-weir type and submerged type configurations offer two distinct overflow fineness ranges from the same basic machine design, allowing XINGAONAI Spiral Classifiers to serve both primary coarse classification duties (high-weir, overflow d80 typically 0.15–0.5 mm) and secondary fine classification duties (submerged, overflow d80 typically 0.074–0.15 mm) across the full range of industrial grinding circuit requirements. Selecting the appropriate type eliminates the need for hydrocyclones in many standard grinding circuit applications, reducing capital cost and simplifying the process layout.

Continuous Ore Washing & Desliming Capability

In ore washing and desliming applications, the Spiral Classifier continuously scrubs and conveys coarse sand particles up the inclined trough while fine clay, slime, and ultrafine gangue minerals overflow with the wash water, producing a clean, deslimed coarse sand product at the upper discharge and a slime-laden overflow at the lower end. This continuous washing and classification action eliminates the batch processing limitations of static washing tanks and produces consistently cleaner coarse product than alternative washing equipment.

Heavy-Duty Spiral & Trough Construction for Abrasive Slurries

The spiral blades are cast from high-chrome alloy iron or fitted with replaceable polyurethane wear inserts on the leading edge and outer diameter — the highest wear zones — extending blade service life to 8,000–15,000 operating hours in normal ore processing applications. The trough lining is fabricated from wear-resistant rubber or polyurethane sheet bonded to the steel trough, replaceable in sections without replacing the entire trough, minimizing maintenance downtime and wear part cost per tonne of material processed.

Overload-Protected Drive with Automatic Spiral Lift

The drive head incorporates a heavy-duty worm gear reducer rated for continuous duty at maximum torque, with a motor overload protection circuit and an automatic spiral lifting device that raises the spiral out of the settled sand bed when the machine is shut down — preventing the spiral from being buried in solidified settled sand during a shutdown period and eliminating the mechanical strain and motor burnout risk associated with restarting a spiral buried in compacted sand. The lifting device operates automatically on shutdown and lowers the spiral back to the operating position when the machine restarts.

Simple Structure, Low Maintenance, Long Service Life

The Spiral Classifier has no complex internal mechanisms, sealed chambers, or pressurized systems — the rotating spiral, the trough, the drive head, and the overflow weir are the only major components. This mechanical simplicity results in low scheduled maintenance requirements, long intervals between major overhauls, and straightforward on-site repair using standard workshop equipment and locally available carbon steel plate and wear-resistant liner materials. Spiral blade replacement and trough relining are the primary maintenance tasks, both performable by plant maintenance crews without specialist contractor support.

Technical Parameters

Model	Spiral speed (r/min)	Return sand volume (t/d)	Overflow handling capacity (t/d)	Spiral diameter (mm)	Spiral length (mm)	Slope of sink	Drive motor model	Power (kw)	Lifting motor model	Power (kw)	Weight (kg)
FLG-300	7.7	30-80	10-30	Φ300	3900	14-18	Y100L1-4	2.2	manual	-	668
FLG-500	8	145-260	21-75	Φ500	4390		Y112M-6	2.2	manual	-	1600
FLG-750	7.8	100-455	31-165	Φ750	5500		Y132S-6	3	manual	-	2716
FLG-1000	6.7	473-1026	85	Φ1000	6556		Y132M2-6	5.5	manual	-	4000
FLG-1200	5,6,7	1145-1600	150	Φ1200	6500		Y132M2-6	5.5	Y90L-4	1.5	7943
FLG-1500	2.5,4,6	1140-2730	235	Φ1500	8265		Y160M-6	7.5	Y100L1-4	2.2	11827
FLG-2000	3.6,5.5	3240-5940	400	Φ2000	8700		Y160L-6/4	11,15	Y100L2-4	3	20814
FLG-2400	3.6	6800	580	Φ2400	9130		Y200L2-6	22	Y112M-4	4	24194
FLG-3000	3.2	11625	890	Φ3000	12500		Y200L-4	30	Y112M-4	4	42188

Model	Spiral speed (r/min)	Return sand volume (t/d)	Overflow handling capacity (t/d)	Spiral diameter (mm)	Spiral length (mm)	Slope of sink	Drive motor model	Power (kw)	Lifting motor model	Power (kw)	Weight (kg)
2FLG-1200	5,6,7	2290-3200	310	Φ1200	6500	14-18	Y132M2-6	5.5*2	Y90L1-4	1.5*2	15840
2FLG-1500	2.5,4,6	2240-5360	460	Φ1500	8230		Y160M-6	7.5*2	Y100L1-4	2.2*2	22903
2FLG-2000	3.6,5.5	6400-10800	750	Φ2000	8400		Y160L-4	15*2	Y100L2-4	3.0*2	34621
2FLG-2400	3.63	13600	1160	Φ2400	9130		Y200L2-6	22*2	Y112M-4	4*2	42460
2FLG-3000	3.2	23300	1785	Φ3000	12500		Y200L-4	30*2	Y112M-4	4*2	73030

Frequently Asked Questions

The key difference lies in the position of the overflow weir relative to the lower bearing of the spiral shaft. In a high-weir type, the overflow weir is set above the lower bearing center, creating a shallower classification pool that produces a relatively coarse overflow product — typically with a d80 of 0.15–0.5 mm — making it suitable for primary coarse classification duties in first-stage grinding circuits. In a submerged type, the entire lower spiral section is fully submerged below the overflow weir level, creating a deeper, longer classification pool with a lower upward current velocity that allows finer particles to settle, producing a finer overflow product with a d80 of 0.074–0.15 mm. The submerged type is preferred for secondary grinding circuits, fine particle desliming, and applications requiring a cleaner, finer overflow product.

Both devices perform the same closed-circuit classification function but suit different operating conditions. Spiral classifiers are preferred when the grinding circuit operates at relatively coarse cut sizes (above 0.15 mm), when slurry density fluctuations are frequent and a self-regulating overflow is needed, when the operation is remote with limited instrumentation and maintenance support, or when the circuit requires simultaneous ore washing and desliming alongside classification. Hydrocyclones are preferred for fine cut sizes below 0.15 mm, high-throughput circuits where floor space is limited, and circuits requiring precise cut point control via pressure adjustment. In many industrial grinding circuits, a spiral classifier handles primary classification while hydrocyclones handle secondary fine classification.

The classification cut size is primarily determined by four interrelated factors: the slurry feed density — higher density slurries produce coarser cut sizes due to hindered settling; the spiral rotation speed — faster rotation increases sand return rate and reduces pool residence time, producing a coarser overflow; the overflow weir height — higher weirs increase pool depth and residence time, allowing finer particles to settle and producing a coarser overflow; and the feed rate — higher feed rates increase upward slurry velocity in the pool, carrying coarser particles into the overflow and producing a coarser cut. For a given machine size, the cut size can be adjusted within a range by controlling feed density and feed rate without mechanical changes to the machine.

In a standard closed-circuit grinding system, the circulating load — the ratio of sand return mass to new feed mass — typically ranges from 200% to 400% by mass, meaning the spiral classifier returns two to four times the fresh ore feed rate back to the ball mill as coarse sand. Higher circulating loads generally indicate finer grinding and tighter cut size control but increase the volumetric slurry flow through both the mill and classifier. The optimum circulating load for a given ore and target grind size is determined during commissioning and process optimization, and is maintained by controlling feed rate, slurry density, and classifier speed.

Overflow becoming coarser than target is most commonly caused by one or more of the following: excessively high feed rate overloading the classification pool and increasing upward slurry velocity; feed slurry density too high, causing hindered settling that carries coarse particles into the overflow; spiral rotation speed too high, reducing pool residence time; or worn spiral blades that reduce sand agitation and transport efficiency, allowing coarse particles to accumulate in the pool and spill into the overflow. Corrective actions include reducing feed rate, diluting feed slurry with additional water to lower density, reducing spiral speed, and inspecting and replacing worn spiral blades.

Under normal ore processing conditions with moderately abrasive feed material, high-chrome alloy cast iron spiral blades typically achieve 8,000 to 15,000 operating hours before requiring replacement. In highly abrasive applications such as silica sand or quartz processing, blade life may be reduced to 3,000–6,000 hours. Key signs of blade wear requiring attention include a visible reduction in blade height on the outer diameter (measured against the original profile), increasing sand accumulation in the lower trough indicating reduced transport capacity, increasing overflow coarseness at unchanged operating conditions, and abnormal motor current draw due to uneven blade loading. Regular annual inspection of blade wear depth using a profile gauge is recommended to plan blade replacement before performance degradation affects grinding circuit efficiency.