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Learn more about Sifters
Dry separators are sometimes called sieves or sifters. They are used to separate oversized and undersized (fines) particles from a powder or blend of powder. The end result is a powder or granulation with only the desired size particles.
In some cases, there may be multiple particle sizes which need to be classified. A separator can be used to do this but the design may be slightly different.
A simple separator will have 2 screens with different mesh sizes. The upper screen will be sized slightly larger than the desired particle size. Oversized particles cannot pass and are discarded. The lower screen will be slightly smaller than the desired size. Fines and small particles will fall through.
In larger and continuous process separators there will usually be a discharge on each screen to remove product and prevent buildup in the pan. Smaller and batch separators may omit this.
Where more size classification is desired multiple screens may be stacked in decreasing mesh sizes.
Screens may be round, square or rectangular depending on requirements and available space.
The stack of sizing screens is fastened together to make a rigid assembly and mounted on a vibrating base. The base drives the screens in a swirling and bouncing motion to agitate the powder on the screens. Some rectangular separators mount the screens on a slight angle and instead of vibration, use a motor to shake the screens in a reciprocating motion.
The amplitude and frequency of the vibration is normally variable and is an important parameter. Too much vibration, especially in the vertical plane may cause particles to break up or wear against each other. This can cause excessive fines, normally discarded. Too little vibration may permit properly sized particles to remain mixed with the larger ones preventing them from reaching the screen and being separated.
In addition to the screen mesh size, screen design is important for proper handling of the powder. Different weaves, even of the same mesh opening, can provide different results. In some instances perforated plates are used in place of mesh screens/
Discuss your application directly with our qualified engineers.
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