Flow-through magnetic separators

Ferromagnetic contaminants can enter liquid material during production, transport, storage or through wear of processing equipment. They may take the form of metal shavings, chips, scale, fragments, wires or extremely fine particles created by equipment abrasion.

A flow-type separator is installed directly into the pipeline. The material flows through an arrangement of magnetic tubes, where ferromagnetic particles are captured on their surface. The cleaned material then continues to the next stage of the process.

What is a flow-type magnetic separator?

A flow-type magnetic separator is an enclosed stainless-steel device containing several magnetic cores housed inside protective tubes. The tubes are arranged to create a flow labyrinth that brings the processed medium close to a strong magnetic field.

Depending on its design and operating conditions, the separator can be used for:

• free-flowing liquid mixtures,
• pressurised piping systems,
• liquid and semi-liquid products,
• horizontal pipelines,
• vertical pipelines,
• protecting pumps, nozzles, filters and other equipment,
• improving the purity of the final product.

How does a flow-type magnetic separator work?

Inside the separator body are stainless-steel protective tubes containing powerful neodymium magnetic cores. The medium must flow between the individual tubes, bringing it into close proximity to the magnetic field.

1. The liquid or semi-liquid mixture enters the separator body.
2. The flow labyrinth divides and directs the medium between the magnetic tubes.
3. Ferromagnetic particles become magnetised within the magnetic field.
4. The particles are attracted to the surface of the protective tubes.
5. The captured contaminants remain on the tubes until cleaning.
6. The cleaned medium exits the separator and returns to the piping system.

Contaminants often accumulate on the side of the tube facing away from the direction of flow. This makes it more difficult for the flowing material to dislodge them again.

Why is the flow labyrinth important?

High magnetic flux density alone does not guarantee effective separation. A ferromagnetic particle must pass sufficiently close to the surface of the magnetic tube.

A correctly designed labyrinth:

• distributes the medium between the magnetic tubes,
• reduces areas where material could flow through without effective magnetic exposure,
• makes use of the working length of the magnetic tubes,
• ensures sufficient contact between the medium and the magnetic field,
• maintains the required flow capacity of the pipeline.

What can a flow-type magnetic separator capture?

The separator is primarily designed for ferromagnetic contaminants, meaning materials that can be attracted by a permanent magnet.

Typical captured contaminants

• iron shavings and chips,
• particles of ordinary magnetic steel,
• scale,
• fragments of wires and fasteners,
• particles caused by wear of pumps and pipelines,
• fine ferromagnetic dust,
• weakly magnetic particles created during mechanical processing.

What will a standard magnetic separator not capture?

A standard permanent magnet does not attract materials such as aluminium, copper, brass, plastic, glass or other non-magnetic materials. Some grades of stainless steel may be only weakly magnetic or completely non-magnetic.

If non-magnetic particles also need to be removed, magnetic separation must be supplemented with another filtration or separation system.

Which liquid materials can be separated?

Flow-type separators can be used for a wide range of liquid and semi-liquid materials. However, the suitability of a specific device always depends on the viscosity, temperature, pressure, chemical composition, flow rate and abrasiveness of the medium.

Examples of applications

• oils and cooling emulsions,
• rinsing baths,
• syrups and sugar solutions,
• yoghurts and other liquid food products,
• ketchups, sauces and semi-liquid mixtures,
• vegetable oils,
• ceramic compounds and glazes,
• chemical mixtures,
• technical fluids,
• liquid intermediate products in manufacturing.

Two main objectives of magnetic separation

1. Protecting production equipment

The separator is installed upstream of equipment that could be damaged or excessively worn by metal contaminants.

It most commonly protects:

• pumps,
• valves,
• nozzles,
• heat exchangers,
• mechanical filters,
• measuring equipment,
• dosing systems,
• other sensitive parts of the production line.

In this case, the separator is installed before the protected equipment. The aim is primarily to capture particles that could cause mechanical damage, blockages or equipment downtime.

2. Improving product purity

The second objective is to remove as many ferromagnetic particles as possible directly from the final product.

The separator can be installed:

• at the end of the production process,
• before filling or packaging,
• at several points along the production line,
• before a sensitive inspection or finishing operation.

Achieving a high level of purity often requires stronger magnetic equipment, a suitable labyrinth and correctly adjusted flow velocity.

Magnetic flux density and pull-off force

When comparing separators, two values are commonly stated – magnetic flux density in gauss and pull-off force in newtons.

Magnetic flux density in Gs

Magnetic flux density describes the intensity of the magnetic field at a specific measurement point. A higher value can help capture fine particles, but on its own it does not describe the overall efficiency of the separator.

Pull-off force in N

Pull-off force indicates the force with which a defined steel test piece is held against the surface of the tube or magnetic core.

A higher pull-off force helps keep captured particles attached to the tube even while material is flowing past them.

Which value is more important?

Both values must be assessed together with the separator design. The number of tubes, their spacing, length and diameter, the thickness of the protective casing and the properties of the flowing medium are also important.

Can very fine metal particles also be captured?

Under suitable conditions, powerful neodymium separators can also capture very fine ferromagnetic particles. However, it is not possible to guarantee one universal minimum particle size for all materials and applications.

The result is influenced mainly by:

• the magnetic properties of the contaminant,
• particle size, shape and weight,
• viscosity of the medium,
• flow velocity,
• distance of the particle from the tube,
• the build-up of previously captured contaminants,
• the magnetic performance of the separator.

Flow-type separators for gravity and pressurised flow

Flow-type separators can operate in systems where material moves by gravity or in pressurised pipelines.

Gravity flow

The medium flows through the separator under its own weight or without significant overpressure. Correct orientation, sufficient flow capacity and prevention of thick material build-up are important.

Pressurised pipelines

The separator must be structurally designed for the specific operating pressure. Standard flow-type separators are commonly manufactured for conventional pressurised systems, while special versions can also be designed for higher pressures.

Types of flow-type magnetic separators

MAGSY flow-type separators are available in several design ranges. They differ in size, magnetic equipment, flow labyrinth, cleaning system, operator safety and price level.

MF Classic flow-type magnetic separator

The Classic range is a proven universal solution for manually cleaned flow-type separators. The magnetic cores are housed inside protective tubes and move vertically during cleaning.

Main advantages of the Classic range

• proven flow labyrinth,
• powerful neodymium magnets,
• sliding magnetic cores,
• easier manual cleaning,
• protection of magnetic cores from direct contact with the medium,
• several magnetic performance levels,
• wide range of pipeline sizes,
• option of manufacturing from different stainless-steel grades.

The Classic range is normally manufactured for round pipelines in several sizes, approximately from DN 50 to DN 250.

MF UP flow-type magnetic separator

The UP range is designed for more demanding applications where high magnetic performance, efficient use of the magnetic tubes and more convenient operation are important.

Main advantages of the UP range

• cascade flow arrangement,
• efficient use of the working length of the magnetic tubes,
• magnetic flux density of selected versions up to 17,000 Gs,
• magnetic tubes with a diameter of approximately 30 mm,
• replaceable protective tubes,
• vertically sliding magnetic cores,
• option to lock the handling mechanism,
• option to use a cleaning fixture,
• suitability for more demanding operating conditions.

Replaceable protective tubes are advantageous, for example, when processing more abrasive media. However, faster wear must be expected and the tubes need to be inspected regularly.

MF EKO flow-type magnetic separator

The EKO range is a more economical version of the flow-type separator. It is based on the proven principle of magnetic cores housed in stainless-steel tubes, but uses a simpler cleaning system.

Main advantages of the EKO range

• lower purchase price,
• simpler construction,
• powerful neodymium magnets,
• effective flow labyrinth,
• stainless-steel construction,
• choice of magnetic performance level,
• standard pipeline connections.

What should you be aware of?

Cleaning the EKO range is less convenient and requires more careful handling of the magnetic cores. It is therefore best suited to applications where simpler manual cleaning is acceptable.

What is the difference between Classic, UP and EKO?

Flow-type separator design

The basic construction consists of the separator body, a removable magnetic component and pipeline connection elements.

Separator body

The body is permanently installed in the piping system. Its dimensions and material thickness must correspond to the pipe diameter, pressure and operating conditions.

Magnetic component

The removable component contains:

• stainless-steel protective tubes,
• magnetic cores,
• a sliding or pull-out mechanism,
• a handling rod,
• a flange or another element for connection to the separator body.

Connection elements

Depending on the design, the separator can be connected using, for example:

• fixed flanges,
• loose flanges,
• food-grade couplings,
• CLAMP connections,
• custom-designed pipeline connections.

What materials are the separators made from?

The standard material is typically stainless steel 1.4301, also known as AISI 304.

For acidic, more chemically aggressive or hygienically demanding environments, depending on the specific application, the following can be used:

• stainless steel 1.4404 / AISI 316L,
• stainless steel 1.4571 / AISI 316Ti,
• special seals compatible with the processed medium,
• customised surface finishes.

The choice of material must be based on the chemical composition of the medium, temperature, cleaning method and hygiene requirements of the operation.

Magnetic cores and protective tubes

The magnetic cores consist of permanent magnetic rings and pole washers. Their precise arrangement determines the resulting magnetic flux density and pull-off force.

The cores are positioned inside stainless-steel protective tubes, which:

• separate the magnets from the processed medium,
• protect the magnets from moisture and chemical exposure,
• allow hygienic and mechanical cleaning,
• partially protect the cores against abrasive wear,
• provide a smooth surface for the flowing medium.

The tubes have thin walls so that the distance between the magnet and the captured particle is as small as possible. Damage or wear to the tube can therefore significantly affect the safety and service life of the equipment.

How is a flow-type separator cleaned?

A manually cleaned flow-type separator must first be safely shut down, depressurised and isolated from the flowing medium.

1. Stop the material flow.
2. Close the relevant sections of the pipeline.
3. Release the pressure and check the equipment temperature.
4. Disconnect or remove the magnetic component from the separator body.
5. Move the component to a safe location or cleaning fixture.
6. Move the magnetic cores away from the separation section of the protective tubes.
7. Once the magnetic field has weakened, remove the captured contaminants.
8. Clean the tubes using a suitable brush or according to the operating procedure.
9. Inspect the condition of the tubes, seals and connecting parts.
10. Return the magnetic cores to the operating position.
11. Reinstall the component into the separator body.
12. Before restarting, check that the system is correctly closed and leak-tight.

How often should the separator be cleaned?

There is no universal cleaning interval. The required frequency depends on the quantity of metal contaminants in the medium, the flow rate, operating time and the required level of cleanliness.

The separator should be cleaned before the layer of captured material begins to:

• cover the active surface of the tubes,
• reduce the available magnetic field,
• restrict the flow of the medium,
• increase pressure loss,
• cause previously captured particles to be released again.

When commissioning the equipment, it is advisable to inspect the separator more frequently and then establish a suitable operating interval based on the actual amount of captured contamination.

Why does an overloaded separator lose efficiency?

Captured ferromagnetic particles form a layer on the surface of the tube. Newly arriving particles are then located farther from the magnetic core and can be more easily carried away by the flowing medium.

Regular cleaning is therefore an essential part of proper operation. Even a very powerful separator may not deliver the expected result without suitable maintenance.

How do you choose the right flow-type separator?

When selecting a separator, you need to assess the pipeline, material, operating pressure, temperature, required separation level and available cleaning options.

Pipe diameter

The size of the separator body must match the piping system. An incorrectly selected size can restrict flow, increase pressure loss or complicate installation.

Medium flow rate

Excessively high flow velocity can reduce the time during which particles are exposed to the magnetic field and increase the force exerted by the flow on captured particles.

Viscosity

Thick and sticky media may require a different labyrinth, larger flow gaps or a specially designed solution.

Temperature

The magnetic cores, seals and structural components must be designed for the highest actual operating temperature. Standard magnetic equipment is often designed for temperatures up to 80 °C, while more temperature-resistant versions may be available on request.

Pressure

The maximum operating pressure cannot be determined solely from the separator diameter. The design of the body, connections, welds, seals and the pressure specification of the particular product are decisive.

Abrasiveness

Abrasive material can gradually wear down the protective tubes. Regular inspection of their wall thickness and the option of easy replacement are therefore important in such applications.

Can the separator be used in the food industry?

Yes, but the specific design must meet the food-processing and hygiene requirements of the operation.

In particular, check:

• the material of all parts in contact with the product,
• the stainless-steel grade,
• the material and certification of the seals,
• surface roughness and finish,
• weld design,
• the possibility of thorough cleaning,
• resistance to the cleaning agents used,
• internal hygiene and process requirements.

How can the efficiency of a magnetic separator be verified?

Efficiency can be monitored in several ways:

• regular inspection of the amount of captured particles,
• analysis of material before and after the separator,
• measurement of magnetic flux density on the tubes,
• measurement of pull-off force using a suitable test piece,
• monitoring flow rate and pressure loss,
• monitoring wear of the protected equipment,
• implementing testing and validation procedures.

Measurements must always be performed using the same method and under comparable conditions. Values measured with different instruments, test pieces or at different locations cannot be directly compared.

Flow-type separator maintenance

In addition to regular cleaning, the mechanical and hygienic condition of the entire device must also be inspected.

• check the protective tubes for wear,
• look for dents, grooves or corrosion,
• inspect the seals and their flexibility,
• verify correct operation of the sliding mechanism,
• inspect flanges, couplings and welds,
• regularly verify magnetic performance,
• keep records of cleaning and inspections,
• replace damaged parts in good time.

Safety when working with a flow-type separator

Recommended flow-type magnetic separators

The selected products represent three different solutions: a compact CIS version with manual cleaning, the UP range with replaceable tubes and a high-performance separator with a semi-automatic cleaning system.

Frequently asked questions about flow-type magnetic separators

Summary

A flow-type magnetic separator captures ferromagnetic contaminants from liquid and semi-liquid materials directly as they pass through a pipeline. It can protect production equipment or improve the purity of the final product.

Efficiency is not determined by magnetic flux density alone. Pull-off force, the number and arrangement of tubes, the flow labyrinth, flow velocity, medium viscosity and regular cleaning are also important.

The Classic range provides a universal and proven solution, the UP range offers higher performance and a more convenient design, while the EKO range provides a simpler and more affordable option.

Before selecting a separator, you need to know the type of medium, flow rate, temperature, pressure, pipe diameter, connection type, contaminant size and required level of separation. For industrial applications, it is advisable to consult the specific solution with a specialist.