Top-Quality Screening & Separating Equipment I Norstone Inc.

SCREENING & SEPARATING

Separation through screening, sieving, classifying and filtering has been around for thousands of years. There are many variations of “modern” screeners which are around 75 years old. However, in the last 10 years newer methods of screening have been developed. For this type of operation there are several considerations in order to determine the type of screen, sieve, filter or classifier that should be used.

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For more detailed information on this subject, please visit the Education & Information Section.

Screeners & Sieves:

Screeners (liquids) & Sieves (powders) are available in a wide variety of styles and shapes for all industries.

The standard types of machines will be rectangular, round or cylindrical with the ability to efficiently screen particles larger than 325 mesh/44 microns.

As particles become smaller they become more difficult to separate through screening/sieving. To aid in this separation, ultrasonic screen stimulators were developed in addition to tools such as balls, brushes, steam, air knives and sprayers.

The newer generation of screeners/sieves uses sound directed to the screen surface to surpass the ultrasonic performance. The sound wave can be captured at a high enough level so that, unlike ultrasonics, it can even be used to separate particles in liquids. The HiSifter is an excellent example of this type of screener which can separate particles as small as 10 microns. In addition to the horizontal and vertical motion created by weights, the acoustic action creates a vertical motion of the product which appears to be similar to a fluid bed. The particle sizes separate more easily as well as adding more velocity to the falling particle. The mesh open area is kept open by the energy emitted by the sound vibration. The limit for these types of screeners is the media and not the technology itself. In other words, the challenge is finding mesh material with small openings and large surface area to make this technology work for particles smaller than 10 microns.

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Classifiers:

The most common classifiers are designed for use with powders. Generally speaking, they contain a spinning cage in an air stream which is able to deflect larger particles and capture smaller particles. A classifer is expensive to operate due to the compressed air but it can separate particles well below 10 microns on a continuous basis. This style of classifier is challenged by abrasive products. While there are wheels tiled with alumina and tungsten carbide, a different style of classifier should be considered. An example would be the Elbow Jet which uses special shaped ceramic and tungsten carbide blocks to separate the particles. There is no spinning wheel which dramatically reduces the wear on the equipment.

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Magnetic Separators:

Another type of separation is removing metal from a product. This can be accomplished with magnets designed for capturing ferrous metal in powders such as a drawer magnet, bar magnet or rotary magnet. An Inline liquid trap magnet can be installed for removing ferrous metal from liquids. Rare earth or ceramic magnets are available with cleaning sleeves to make it easier to remove the captured metal. Another method from continuous cleaning would be an inline electro magnet or a metal detector which can remove both ferrous and non-ferrious metal. It is efficient at removal but also removes a lot of good material.

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Filters:

Filters are available for a wide range of particles sizes from microns to centimeters. Inexpensive filters would be a bag filter with or without a housing. Another style would be depth filters which can be placed in a housing using multiple filters at one time. A more dynamic style would be an inline filter or liquid/solid separator that runs continuously by continuous cleaning of the screen. More expensive options for larger operations would be a filter press, centrifuge or pressure filter.

If you would like more information for a specific application please complete the application questionnaire on Screening, Sieving, Filtering.

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SCREENING ACCESSORIES:

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MIXING

Mixing and Blending can be a process unto itself or a step prior to other processing steps. It is critical to ensure that the process be completed based on the desired results which could be partial blending, full blending or homogenization.

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DISPERSING

Dispersion is usually defined as the mixing of two or more non-miscible liquids, or solids and liquids, into a pseudo-homogeneous mass which is more or less stable as measured by its life before noticeable separation occurs.

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MILLING

Milling covers a wide range of processes for powders, liquids and pastes. The main goal of milling is to crush, de-lump, deagglomerate, cut, tear, grind, smash, granulate or reduce the particle size.

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