Spiral Classifier

What is Spiral Classifier?

Sinking spiral classifier is a kind of equipment that utilizes the difference of settling speed of solid particles in liquid to carry out mechanical classification. The spiral blades at the overflow end of the spiral classifier are all immersed below the overflow surface, which is mainly suitable for grading ores with overflow particle size of 0.15～0.07mm.

The design features of the spiral classifier include that the whole spiral blade at the overflow end is immersed below the liquid surface of the settling zone, which can increase the area and depth of the settling zone and thus improve the grading efficiency.

In addition, the immersed spiral classifier adds an automatic lifting device for sand return and eliminates the configuration of the large scoop head of the ball mill in order to save operating costs and reduce the need for maintenance.

What Is Spiral Classifier Used For?

piral classifier is widely used in the production process of metal material beneficiation plant because of its smooth grading surface, high overflow yield and fine particle size.

For example: Southern Africa has a savannah climate with high humidity in the air, and many machines are often eliminated due to rust. A gold mining project in Tanzania, the demand for ore sorting is not particularly large, but the requirements for ore particle size are more stringent, Chunlei according to the customer’s geographic location and needs, for the customer to select a spiral classifier, grading overflow size ≤ 0.015mm, grading effect in line with the customer’s needs, beneficiation recovery rate increased by 15%.

Customer Cases

Chunlei Machinery has been engaged in mining machinery manufacturing for more than 30 years, with a wealth of experience in building websites and customer cases, served customers all over the world!

Technical Parameters

Typology	Model	Screw speed (r/min)	According to the return sand processing capacity (t/d)	According to overflow treatment capacity (t/d)	Screw diameter (mm)	Spiral length (mm)	Slope of flume	Transmission motor model	Transmission motor power (kW)	Lifting motor model	Lifting motor power (kW)	Weight (kg)
High Weir Type Single screw	FLG-300	7.7	30 ~80	10 ~30	φ300	3900	14 ~18	Y100L1-4	2.2	manually operated	—	668
	FLG-500	8	145~260	21 ~75	φ500	4390		Y112M-6				1600
	FLG-750	7.8	100~445	31~165	φ750	5500		Y132S-6	3			2716
	FLG-1000	6.7	473~1026	85	φ1000	6556		Y132M2-6	5.5			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
High Weir Double Screw	2FLG-1200	5,6,7	2290~3200	310	φ1200	6500		Y132M2-6	5.5X2	Y90L1-4	1.5X2	15840
	2FLG-1500	2.5,4,6	2240~5360	460	φ1500	8230		Y160M-6	7.5X2	Y100L1-4	2.2X2	22903
	2FLG-2000	3.6,5.5	6400~10800	750	φ2000	8400		Y160L-4	15X2	Y100L2-4	3.0X2	34621
	2FLG-2400	3.63	13600	1160	φ2400	9130		Y200L2-6	22X2	Y112M-4	4X2	42460
	2FLG-3000	3.2	23300	1785	φ3000	12500		Y200L-4	30X2	Y112M-4	4.0X2	73030

Working Principle of Spiral Classifier

Sinking spiral classifier is a kind of grading equipment to carry out mechanical grading with the help of the principle that the solid particles have different sizes and specific gravity, and thus different settling speeds in the liquid, the fine ore particles float in the water into the overflow, and the coarse ore particles are sunk in the bottom of the tank, and are pushed to the upper part of the tank by the spiral to be discharged. Through the low-speed rotation of the spiral, the slurry is stirred so that the fine particles are suspended to the top, flowing to the overflow weir overflow, the coarse particles sink to the bottom of the tank, and are transported by the spiral to the discharge port as the return sand discharge.

Generally, there are 4-5 spiral blades in the overflow weir end of the spiral classifier, all of which are submerged in the slurry. This kind of classifier has a large area of settling area, deep grading pool, and the stirring of the spiral has less influence on the surface of the slurry. So the grading surface is smooth and the overflow is large and fine.

Advantageous features of Spiral Classifier

• The whole spiral at the overflow end of the spiral classifier is submerged below the liquid surface of the settling zone, which has a large area and depth.
• Increase the automatic lifting device for sand return and cancel the configuration of large scoop head of ball mill，Saving 1-1.5 degrees of electricity per ton of ore
• Avoiding the frequent overhaul of the big spoon head.
• Slowing down the unbalanced impact on large and small gears.

FAQ

Q: What is the main function of a spiral classifier?
A: It is mainly used for particle size classification in grinding circuits. It accepts the discharge from a ball mill, sends qualified fine particles (typically <0.15mm) out through the overflow weir to the next process, and returns coarse particles (unqualified) back to the ball mill via the spiral blades for re-grinding. Simply put, it controls grinding fineness and prevents over-grinding.

Q: Which is better – a spiral classifier or a hydrocyclone?
A: Each has its advantages. Spiral classifier benefits: simple structure, lower investment, low operating cost, fewer failures – suitable for coarse grinding classification (overflow fineness 0.15-0.3mm). Hydrocyclone benefits: higher classification efficiency, smaller footprint – suitable for fine grinding classification (overflow fineness 0.074-0.15mm). Generally, use a spiral classifier for coarse grinding and a hydrocyclone for fine grinding.

Q: What is the sand return ratio (circulating load) of a spiral classifier?
A: Under normal operation, the circulating load is typically between 100% and 300%. For example: if the ball mill receives 100 tons/hour of new feed and returns 200 tons/hour of sand, the circulating load is 200%. A circulating load that is too low (<100%) indicates poor classification efficiency, while too high (>350%) may accelerate spiral blade wear.

Q: What can I do about rapid wear of the spiral classifier blades?
A: Blade wear is normal, but you can extend their life: ① Choose high-wear-resistant materials (e.g., wear-resistant cast iron or carbide overlay blades) – they last 2-3 times longer than ordinary cast iron; ② Control slurry density (recommended 35%-50%) – too high density accelerates wear; ③ Regularly inspect and flip blades (if designed with two usable sides); ④ Install bottom liners to protect the blade roots.

Q: How do I adjust the overflow fineness of a spiral classifier?
A: There are 4 simple methods: ① Adjust the spindle speed (faster speed = coarser overflow); ② Adjust the overflow weir height (higher weir = finer overflow); ③ Adjust the tank inclination angle (standard angle 14-18° – steeper = coarser overflow); ④ Adjust the slurry density (thinner = finer overflow). Start by adjusting the speed and weir height first – these have the most noticeable effect.