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Magnetic filtering

Removal of metal contaminants

Magnetic separators filter and remove metal contamination from your product streams. They guarantee the product quality and prevent damage to machines.

Metal contaminants – also called foreign bodies – can enter your production line in all sorts of ways. Pieces of iron or steel in the raw material, staples, nails and screws from packaging, bolts and nuts that have vibrated loose, wear of the moving parts, rust or corrosion, etc. These foreign bodies can 'contaminate' your finished product, and they can also cause severe damage to your machinery. Rejection of batches is costly, but it can be even more costly if the contamination is not detected and removed, making it necessary to conduct a product recall. You will then be faced with enormous costs and damage to your reputation.

 magnetic bars with iron particles
Filtered out iron particles

Film Detection & Separation
 plate magnet separators with iron particles
Plate magnet separators
 bar magnets with iron particles
Bar magnet inline separators

Magnet separator or metal detector?

A magnetic separator filters (and later disposes of) or immediately removes the metal contaminants from the product stream. Magnetic separators result in practically no product loss and are suitable for removal of regularly occurring and larger quantities of metal contamination.

A metal detector is mainly used as a means of inspection for sporadically occurring metal contamination. A metal detector only detects. If you want the detected metal particle to be removed, you must also stop the production line or have a rejection mechanism eject the metal particle – resulting in the loss of a large quantity of product.

Three good reasons to install a magnet separator

1. Magnets improve your product quality/purity

Contamination or foreign bodies in food products can lead to claims, very costly product recalls and reputational damage. And not just in food: even the smallest foreign bodies are undesirable in pharmaceutical, chemical or mineral bulk streams and lower the quality of the finished product.

magnetical filtering of iron contamination

2. Magnets prevent damage to your production machinery

By placing a magnetic separator before the inlet of your production machinery – such as grinders, ball mills, pin mills, calenders and crushers – you prevent damage to your machinery and production standstill. A magnetic separator very effectively filters metal contaminants from your bulk stream; they function continuously and provide a high level of operational reliability.

 machine damage caused by metal contamination

3. Magnets prevent dust explosions

Fine dust in combination with oxygen and a source of ignition can result in dust explosions. By filtering metal particles out of the process in advance, magnets remove an important ignition source: the impact of metal on metal. This prevents serious injuries (or worse) and high costs from damage to your machines.

Many of our magnetic separators are suitable for use in ATEX zone 20/21. As a certified manufacturer of ATEX equipment, Goudsmit has an externally certified quality assurance system that guarantees the explosion safety of our magnetic separators.

Use of magnets to prevent dust explosions

Main groups of magnet separators

We make use of three types of magnetic separators, each with its own specific characteristics and applications:

  1. Magnet separators with plate or block magnets (suspension magnets) have a deeply penetrating magnetic field for capturing ferromagnetic metal particles as small as 1 mm. Plate magnets, chute magnets and external pole magnets are used in pipeline transport (inline magnetic separators). These systems are permanently magnetic. Suspension magnets (large block magnets) with and without a conveyor system (overbelt magnets) pull pieces of metal out of a material stream on a passing belt; these types can be found in the main group Recycling & Sorting.
 plate- / block magnets

  1. Magnetic separators with bar magnets have an extremely powerful yet less deeply penetrating magnetic field. They are therefore best suited for filtering small ferrous contaminants and even weakly magnetic (e.g. cold-worked stainless steel) contaminants as small as 30 µm. Our grid/grate magnets, Cleanflow magnets and filter magnets make use of bar magnets.
 bar magnets
  1. Magnetic separators with cylindrical magnets are used in our bullet magnets, drum magnets, head roller magnets and Eddy Current non-ferro separator. With the exception of the bullet magnet, these magnets do not hold the captured metal particles (for periodic disposal) but rather dispose of them continuously. They are therefore capable of handling large quantities of metal particle contamination. The extra robust types of drum magnets, head roller magnets and Eddy Current separators can be found in the main group Recycling & Sorting.
 cylindrically shaped magnets

What versions and options can I choose from?

Within the large standard series of magnetic separators there are many available options. This way we are always able to find a suitable product for your metal problem. If we are nevertheless unable to find the right solution from among our standard products, our engineers are happy to develop a special custom solution.

Food/Pharma versions

  • Magnetic filters that meet the strict European foodstuffs directive EC 1935/2004 and the EHEDG guidelines.
  • Magnetic filters that are suitable for Cleaning in Place (CIP).
EHEDG member logo

Dust explosion-proof versions

For dust explosion risk areas we supply ATEX-certified magnetic separators.

Ex ATEX logo


  • Painting (only for products that are not made entirely of stainless steel)
  • Abrasive grit blasting – Ra 3 µm (standard non-food/pharma finish)
  • Drum polishing / hand polishing – Ra ≤ 0.4 µm (standard food/pharma finish)
  • Electrolytic polishing – Ra ≤ 0.6 µm (not attractive and not always possible in connection with the shape)
  • Wet blasting – Ra ≤ 0.6 µm (new – better resistance to powder adhesion than polishing)
Goudsmit magnetic filter surface finish

Cleaning of filtered metal particles

  • Bar and plate magnet systems:
    • Manual cleaning (manually wiping off iron)
    • Manual quick cleaning (with extractor – iron falls off after extractor is pulled out)

  • Bar magnet systems
    • Easy-Clean cleaning = semi-automatic cleaning
    • Automatic cleaning with production stop / filters with CIP
    • Automatic cleaning without production stop

  • Drum magnets and belt separators (see also Recycling & Sorting)
    • Automatic, continuous cleaning without production stop

Magnet choice: strength and high-temperature resistance

We usually use very powerful neodymium magnets as standard in our separators. But in some cases separation with ferrite magnets, or a combination of neodymium and ferrite, can be an adequately strong, money-saving solution.

Neodymium magnets are currently the strongest magnets on the market. Furthermore, increasingly powerful versions of this material continue to become available, making it possible to filter ever smaller and weaker magnetic particles.

The downside of neodymium is that the standard versions can only withstand temperatures of up to 60 °C.

Ferrite magnets are around 10x less powerful than neodymium magnets but are less expensive and also suitable for high temperatures (up to around 200 °C).

For high-temperature applications where high magnetic holding power is also required you can opt for:

  • high-temperature-resistant magnets – up to 150 °C or even up to 200 °C
  • samarium-cobalt magnets – up to 250 °C or even up to 350 °C

Whereas neodymium magnets lose strength as their high-temperature resistance increases, this is not the case for samarium-cobalt magnets; the magnets of this type that are resistant to the highest temperatures are also the most powerful. For this reason samarium-cobalt is always used for temperatures above 200 °C.

Goudsmit Magnetics - super strong magnets
Goudsmit Magnetics - all magnet types

Coating or hardening – for abrasive product streams

For applications in abrasive bulk steams, the magnets – and other parts if necessary – can be protected with a wear-resistant coating such as tungsten carbide or a hardening method such as hard inchromizing.

Goudsmit Magnetics – Tungsten Carbide coating


  • Most magnetic separators can be fitted with safety sensors to detect whether they are closed. We can also build-in detection with which you can check whether the magnets are in the product channel during production start-up.
  • Automatic cleaning systems include a simple control system as standard. You can integrate these in the overall control system for your process so you can control the cleaning from your control room.

Goudsmit Magnetics - EHEDG Magnetic filter magnet sensor control

Can I use magnetic separators for any product, with any transport system?

Yes. Magnetic filters and separators can be used for virtually all product streams, production systems and types of product transport:

For every type of product transport

  • Free-fall chutes
  • Pneumatic chutes
  • Belt conveyors
Goudsmit Magnetics - magnetic separator for free fall chutes
Goudsmit Magnetics - magnetic separator for pneumatic chutes
Goudsmit Magnetics - overband magnetic separator

Throughout the production chain

Magnetic separators are used throughout the production chain, from raw material receiving to finished product processing. For example, they are placed in, after, alongside or above:

  • conveyor belts
  • metering units
  • fans
  • filter units
  • inlet and outlet of silos
  • cyclones
  • blenders
  • inlet and outlet of sieves
  • rotating valves
  • sifters
  • vibration units & shaking sieves
  • etc.

In every type of product stream

Magnetic separators are used in practically all imaginable types of product streams:


Type of product stream

Type of magnetic separator

granular / coarse products

Granular product stream

Such as plastics, minerals and food products.
Examples: chamotte, quartz sand, glass, silica, corundum, plastic injection moulding pellets, cocoa beans, grains, sugar
Cleanflow magnets
External pole magnets
Chute magnets
Cascade magnets
Bullet magnets
Drum magnets
Magnetic head pulleys (see Recycling & Sorting)
 powder products

Powder product streams

Such as food products, ceramics, minerals, pharma and chemical products.
Examples: sugar, cocoa or milk powder, flour, starch, tobacco, tea, coffee, spices, salt, lactose, baby food, talcum powder, lithium, aluminium oxide, titanium oxide, carbon black, animal feed, zinc oxide, calcium carbonate, drug powders
External pole magnets
 chocolate products

Viscous product streams

Such as greases and pastes.
Examples: butter, oil, melted chocolate
Double-walled filter magnets
(with heated housing)

Liquids – flowing under pressure

Filter magnets

Our goal? To ensure that your finished product is 100% free of harmful metal contaminants.

All Goudsmit magnetic separators are designed primarily for deferrization: optimal removal/filtering of metal contamination. Moreover, all our magnetic separators are simple to install and require little installation space due to their compact design.

Our expansive knowledge and many years of experience, impressive modern test centre and large selection of magnetic separators and options enable us to find the best solution for your metal contamination. We also have solutions available that are fully compliant with your industry-specific criteria, standards and certifications.

Is it possible to magnetically filter or separate ALL metal contamination?

No. Not all metals can be magnetically attracted or repelled. Fortunately, most metal contaminants can be.

There are three types of metal contaminants:

  1. The iron and steel particles (the ferrous metals). These have a ferritic or martensitic structure and therefore a high relative magnetic permeability, so they are strongly magnetic. These particles are powerfully drawn to magnets.
  2. The stainless steel contaminants. These are often particles resulting from wear of your production line. Stainless steel has an austenitic structure and therefore, in principle, is not attracted by magnets. Stainless steel does, however, become magnetic once it has been subjected to mechanical working or deformation, such as in the case of particles resulting from wear. This is because the mechanical working or deformation causes the austenitic structure to become ferritic or martensitic. With our most powerful magnets we can also often filter these weakly magnetic stainless steel particles from your product stream.
  3. The non-ferrous metals. These are non-magnetic and thus are not attracted by a magnet. Nevertheless, these metals can often be magnetically separated through the use of 'Eddy Current' separators: see Recycling & Sorting – Separation/recovery of non-ferrous metals.
 magnetic vs non-magnetic

You can find more information about magnetism in our knowledge base.

Why GOUDSMIT magnetic separators?

Years of knowledge and experience

Goudsmit Magnetics offers you a wealth of experience and knowledge concerning magnetic filtration and separation techniques. We analyse your product and use our experience and 2D/3D FEM calculations to propose the most suitable magnetic technique.

And if we are uncertain? Then we test the product in our test centre first to determine whether the intended result will be achieved.

Goudsmit Magnetics - specialists in magnetism

Continuous development

Your questions, wishes and ideas, combined with our years of experience, have led to the development of a large range of magnetic filters and separators.

We can say with conviction that new developments, along with our years of experience, in combination with ever stronger magnetic material and better modelling software will make our magnetic filters and separators even more sophisticated and powerful in the future.

Goudsmit Magnetics - new development magnetic separator
Your process
Particles/pieces to be separated


Magnetic bars

Magnetic bars are the building blocks of many magnetic systems and are used to filter product streams for the removal of very fine ferromagnetic and weakly magnetic particles (from machined stainless steel or iron oxides, for example).

More information

Magnetic grids/grates

Magnetic grids are placed at a pouring point or funnel. They provide an indication of whether ferrous contamination is present and have a control function. For free flowing powders and granulates.

More information

Cleanflow magnets

Cleanflow magnets filter very fine ferromagnetic (and even weakly ferromagnetic) contamination out of powders and granulates in free-fall processes. Many types and options; continuous, automatic cleaning possible.

More information

Magnetic filters

Magnetic filters capture very fine magnetic, and even weakly magnetic, ferrous contamination or powders in pressurised pipes. Many types and options; automatic cleaning possible.

More information

Bullet magnets

Permanent and electromagnetic bullet magnets have one large magnetic core and are capable of high capacity filtering of ferromagnetic contamination from coarse raw materials. Automatic cleaning possible.

More information

Plate magnets

Magnetic plates can hang above a conveyor belt, be built-in against the wall of a product chute or against a sheet that the product flows over.

More information

Chute magnets

Chute magnets are used for powder streams in free-fall or chute applications; a simple solution for removal of ferromagnetic contamination.

More information

External pole magnets

External pole magnets filter ferromagnetic contamination from poorly flowing products. Large solids can also pass, because the passage is completely unobstructed. Continuous automatic cleaning possible.

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Cascade magnets

Cascade magnets filter ferromagnetic contamination from coarse raw materials and permit optimal flow. The cascade arrangement forces the product to closely pass three plate magnets. Automatic cleaning possible.

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Magnetic drum separators

Magnetic drum separators automatically and continuously separate large quantities of ferrous particles from granular products. Several new types of drum even separate weakly magnetic particles.

More information

Magnetic sweepers/brooms

Magnetic brooms 'sweep up' iron particles from clean or rough floors or sandy surfaces; they are mainly used areas where iron is difficult or impossible to sweep up or is not visible, such as in sand.

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