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Whirlwind® Air Classifier


The Whirlwind® Air Classifier incorporates a self-contained fan and rejecter blade classification system. Its internal fan design does not require cyclones, air locks or dedicated baghouse for product collection of particles in the range of 100 to 400 mesh. Completely self-contained, requires no process dust-collection equipment.

Learn more about the Whirlwind® air classifier by clicking on the links below. If you have any questions, please contact us.


Models & Specs
SizeHPAir Flow Vent (CFM)Feed Rate TPHWeight (lbs)Overall Dimensions (ft.)
H x W
20″5 – 7.525 – 5016503′ 9″ x 2′ 5″
3′7.5 – 1065 – 12531,5006′ 7″ x 3′ 3″
4.5′10 – 1575 – 15082,4008′ 8″ x 4′ 10″
6′15 – 2590 – 175146,80010′ 9″ x 6′ 4″
8′20 – 30150 – 300259,50013′ 0″ x 8′ 4″
10′30 – 40190 – 3754013,00015′ 8″ x 10′ 4″
12′40 – 50275 – 5505618,50019′ 1″ x 12′ 4″
14′50 – 75400 – 8007721,50021′ 1″ x 14′ 5″
16′100 – 150675 – 1,35012531,00024′ 5″ x 16′ 5″
18′250 – 3001,000 – 2,00020050,00027′ 7″ x 18′ 5″
20′350 – 4001,500 – 3,00030068,00030′ 9″ x 20′ 5″
22′450 – 5002,000 – 4,00045087,00033′ 0″ x 22′ 5″
24′600 – 7002,500 – 5,000600117,00035′ 10″ x 24′ 5″
26′600 – 8003,000 – 6,000800125,00038′ 9″ x 26′ 5″
Features & Benefits
  • Lowest capital cost: no auxiliary equipment such as cyclones, process dust collectors, air locks or system fans are needed
  • Consistent, high-quality product with some external adjustment
  • Processes abrasive materials: long-wearing ceramic liners and inexpensive steel replaceable liners
  • Low energy consumption
  • Easy access for cleaning and low maintenance


Watch the illustrated demonstration of how our product works by clicking the image to the right.

When do you use air classifiers?

Air Classifiers are normally used when the particle size that needs to separate is too fine for a screen. The air classified product can be the Coarse without Fines/Dust or the Fines without Coarse/Grit

How dry does the feed need to be?

In order to effectively remove the fine powders, the surface moisture must be very low, less than 1 – 2% is best but some fines can be removed even at 2.5-3%.

Can air classifiers be used for abrasive materials?

Yes. Air Classifiers do not operate at the high speeds that pulverizers do and with adequate wear protection can economically be used to process even abrasive ceramic powders.

How fine can the air classifiers cut?

Air Classifiers can separate powders as coarse as 80 mesh or as fine as 2-3 microns.

Can air classifiers separate by density?

Yes density plays a role in Air Classifier separation, but the internal air currents are actually affecting the overall mass/weight of the particles in the feed. Lighter & Smaller particles are removed by the airflow, while Heavier & Larger particles are not entrained in the airflow. It must be noted that an air current will view the mass/weight of any Large/Low density particles as being similar to the mass/weight of any Small/High Density particles. Therefore, when different density particles are present throughout the feed distribution, it becomes much more difficult to segregate them using an air classifier.

How do you control the fineness of the classified products?

The fineness of Air Classified products is controlled by the quantity of rejector blades, the speed of the rejector blades, the velocity of the airflow and the feed rate

Do air classifiers require cyclones or baghouses?

Air classifiers are categorized as Internal Fan models and External Fan Models. Internal Fan models re-cycle the air and do not require cyclones or baghouses to collect the separated fines. External Fan Models require cyclones or baghouses to collect the separated fines.

Do air classifiers fracture materials and generate fines?

In most cases Air Classifiers do not fracture the powders because Air Classifiers do not operate at high speeds as do the pulverisers. However, in cases where the feed powder consists of very soft agglomerates, some fracture can occur.

Can air classifiers be used with mills?

Yes, in fact, Air Classifiers commonly operate in closed-circuit with a mill. This maximizes the capacity of the mill and reduces the mill’s energy cost because it does not have to be the sizing device.

Can air classifiers be fed pneumatically?

Yes. Air Classifiers can be fed pneumatically and, in many cases, offers the opportunity to install the unit in a pneumatic conveying line. However, it should be noted that the particles in a pneumatic fed process enter the Air Classifier at much higher velocity than gravity fed particles. Particles that approach the rejector blades at higher velocities are more likely to pass through, which requires a higher rejector speed to stop the oversize particles. Generally, this results in higher wear and lower fines removal efficiency.


Sturtevant is more than an equipment manufacturer, we stand behind every product we sell.

Not only do we strive to provide the best product for each and every application, but we also test, evaluate and maintain our products to assure our clients’ needs.

Sturtevant offers a variety of services to assist with the development, maintenance and testing of products.

  • Lab Sample Testing
  • Field Services
  • Reconditioning
  • Replacement Parts