How do Magnetic Filters Compare to Other Filtration Methods?

Maintaining clean coolants and lubricating oil is vital in ensuring efficiency and quality output on processes such as grinding, lapping, wash systems, honing, drilling and other “super-finishing” operations.

There are many different types of filter and filtration systems available, and each can make distinct process improvements - but closer inspection may suggest that they are not performing to the optimum levels. You may think your filtration is working effectively, but is it?

Advanced Magnetic Filters

Our advanced magnetic filters have been developed to overcome some of the typical problems experienced when using traditional filters. They remove almost 100% of ferrous particles, including sub-micron size. As a result they extend fluid lifespan, save costs on consumable filters, minimize filter waste, and improve product quality. In addition, they offer 24/7 uninterrupted filtration.

Before choosing a new filtration system or upgrading an existing one, it's important to consider the positives and negatives of each:

Find out more about Magnetic Filtration 

Barrier or Media Filters

(e.g. Cartridge filters, sock filters, bag filters, paper bands)

Basic Concept: Fluid passes through some form of barrier usually in the form of a bag, cartridge or sheet made from paper, polyester or polypropylene. The barrier allows the fluid to pass through, but prevents contamination particles from circulating. When full, the barrier is either cleaned, or disposed of and replaced.

Positives +

In applications with low levels of contamination, which don’t require an ultra-precise surface finish, barrier filters provide an adequate and effective means of filtration, and do offer some positives.

• Ease of Control – Differential pressure gives the operator a clear indication when a filter is full and maintenance work is needed.
• Capital Cost – Barrier filters are relatively cheap to buy and install. In some cases, the fluid supplier may even subsidize the costs. However, because of the on-going spend on consumable filters media, the overall costs are high with a very long return on investment period.
• Non-magnetic Contamination - Barrier filters remove both magnetic and non-magnetic particles, but only to a certain size.

Negatives -

• Running Costs – Barrier filters are usually disposable items, and when they become blocked they are replaced. In medium to heavy contamination applications, the costs of replacement consumable filters can be enormous. In addition, there are downtime costs each time the machine is stopped to replace the filters.
• Environmental Costs – Using disposable filters not only results in significant disposal costs, but also environmental damage because used media is sent to landfill sites. With the advent of ISO14001 and more corporate focus on environmental responsibility, many companies are looking to reduce waste.
• Limited Filtration Capability – In order to maintain flow, barrier filters are often limited by the media pore size. To avoid restricting flow, the pore size may be typically set at 10-20 microns, which means that any contamination particles below this size continue to be circulated. As a result, components may be damaged, surface finish quality reduced, process accuracy may be reduced, and oil/coolant lifespan also reduced.
• Downtime – In medium to high contamination applications, barrier filters are susceptible to blinding or blocking, which causes a drop in pressure which in turns triggers the machine to stop. In certain applications this can result in hours of downtime and maintenance time.

Settlement Tanks

Basic Concept: During the cycle, fluids such as coolants,oils, cutting lubricants are often pumped into a holding tank where larger particles fall to the bottom of the tank through natural gravity settlement. In some cases they are removed by a drag conveyor, but more likely they accumulate to point where the tank has to be drained and manually cleaned.

Positives +

• Filter Media Costs -The main advantage of settlement is that there is no on-going investment in disposable filters.
• Primary Separation - Settlement provides adequate, cost effective means of primary separation of larger particles, typically 100 microns or larger. This does reduce the burden on secondary filters.

Negatives -

• Ineffective Filtration Capability - Settlement relies on the weight of the particle and the time the fluid remains in the tank in order to be effective. If the particles are small, low density, or pass through the tank quickly, natural settlement is largely ineffective. Generally, any particles below 100 micron size continue to circulate; damaging finished product, damaging process equipment, and reducing the quality/lifespan of the fluid.
• Downtime - Manually cleaning the holding tank can be an expensive process in terms of direct man hours and resultant process stoppages.
• Reduced Fluid Quality - The lifespan of coolants and oils can be significantly reduced as contamination is recirculated and gradually builds up in the fluid.
• Secondary Filtration Required - For effective filtration to be achieved, an additional secondary filter will usually be needed to work in conjunction with the tank.

Cyclonic Separation

Basic Concept: Cyclonic, centrifuge or hydro-cyclonic systems are widely used. The general principle relies on the different densities of the liquid and contaminant to accelerate natural settlement. Fluid flows in a cyclonic pattern around a vessel wall, and centrifugal force separates out contaminated particles which are forced downwards for collection, whilst clean fluid flows out.

Positives +

Filter Media Costs - After an initial capital investment there are no consumable filter costs or disposal costs.

Negatives -

• Filtration Capability - Generally, cyclonic systems can only extract medium to larger contamination, with low density or smaller particles still passing through. In many cases, anything smaller than 10 microns will continue to circulate causing on-going damage to finished parts and process equipment, as well as reducing fluid quality.
• High Maintenance - Many cyclonic systems need regular cleaning to remove contamination and prevent outlets from becoming blocked.
• High Capital Investment Costs - On larger machine tool applications, cyclonic systems can represent a high capital investment cost when compared to other filter systems.
• Flow Restrictions - Due to the nature of the process, cyclonic systems are often unable to handle higher flow rate applications.

Traditional Magnetic Systems

When magnetic filters or magnetic separation is mentioned, many people think of traditional methods such as a ferrite magnetic rod or bar mounted or suspended in a holding tank, or a low intensity magnetic roller such as a coolant roller. This is by far removed from the advanced magnetic filtration systems now available.

Basic Concept: Traditional magnetic filters rely on magnetism to attract ferrous particles as the device comes into contact with the fluid, thereby removing it from circulation.

Postives +

• Filter Media Costs - Magnetic filtration does not need any consumable items and has no on-going running costs.
• Primary Filtration - In applications which don't require a precision finish, contamination particles are large and the flow rates low, traditional magnetic filters or separators can be a cheap and effective solution.

Negatives -

• Ineffective Filtration Capability - Traditional magnetic systems can be used as primary filters to remove large particles. But if they are used as the sole means of filtration, they are ineffective in precision finishing applications. They are often limited by magnetic strength as low intensity magnets are often used. They are also limited by design; in most cases the fluid does not flow close enough or for long enough around the magnet to be effective. Large volumes of contamination continue to circulate resulting in the negative effects previously discussed.
• Downtime - Traditional magnetic filters or separators are often badly designed and not user friendly when being serviced. This can result in long periods of downtime and a laborious, dirty cleaning operation.

Vacuum Filters

Basic Concept: Vacuum filters use vacuum or suction to draw fluid through a filter media. Clean fluid flows into a “clean” tank, and contamination is held on the filter media which is periodically cleaned.

Positives +

• Automation - Such systems are often automated, which reduces downtime or manual intervention for cleaning.
• Higher Flow Rates – Vacuum filters are available for larger applications which handle high volumes of fluid and higher flow rates.

Negatives -

• High Capital Investment - Many vacuum filtration systems are hugely expensive investments. Whilst they are effective for some applications, the return on investment is over a very long period.
• Filter Media Costs - Vacuum filters rely on a filter media to capture the particles. In some cases this media can be cleaned and reused, however it will ultimately need replacing, resulting in costs and disposal issues.
• Filtration Capability – While vacuum filtration systems generally have an improved capability than standard barrier filters, they are not fully effective for high precision processes. The market leading vacuum filters can remove particles down to 1 micron size, but many other systems only operate at 5-10 microns. The problem with this is that smaller sub-micron particles remain in the process; damaging process equipment, reducing part quality, and reducing the fluid life.

See the comparison summary table below:

Note: This is general information for guidance purposes only. Please consult Eclipse Magnetics for application specific information.