magnetic mechanical filter

When you hear “magnetic-mechanical filter?”, the first thing that comes to mind is some kind of hybrid system, where the magnet is simply screwed to the mesh. In reality, everything is more complicated and interesting. They are often confused with conventional magnetic traps, but there the principle is different - pure attraction, but here it is a combination of forces. In practice, especially at processing plants, this difference becomes critical. For a long time I believed that the main thing was the power of the magnet, until I encountered a situation where a powerful neodymium magnet became clogged with sludge in two shifts, and a simple mechanical compartment without a “smart” one. flushing turned into a mud plug. That's when we really had to figure it out.

Design: what is hidden behind the name

If we take a typical circuit, then the base is a drum or tape with permanent magnets, often fromLONGI Corporation, plus a mechanical separation system - vibrating grids, flushing channels. The key is interaction. The magnetic field traps ferromagnetic particles, and the mechanical part is responsible for discharging the non-magnetic fraction and cleaning the working body itself. The problem is that many manufacturers, especially in the budget segment, save money on the reset unit. They install a weak vibrator or do a conditional flush - with water from a common pipeline under low pressure. As a result, everything sticks to the magnet, and the efficiency drops catastrophically.

ULONGIin some models that we tested for processing iron ore concentrate, there was an interesting move - a combined discharge system: a short strong vibration pulse + a counter jet of water under a pressure of 4-5 atm. It's not perfect, but it worked more stable than its analogues. True, it required a separate pump module, which complicated insertion into the line. On their website,https://www.ljmagnet.ru, you can find diagrams, but from experience, real nuances often emerge only in the field. For example, the same water: if it is of high hardness, the nozzles become clogged within a month, and the whole calculation goes down the drain.

Here it is worth making a digression about magnets. Rare earths, of course, give high induction, but in an aggressive environment, say, during wet enrichment, their protective coating is a weak point. I have seen cases where, during a season of active work, chips appeared on the magnets, corrosion began, and the field “floated”. Therefore, recently, for difficult conditions, they have sometimes returned to ferrite systems, albeit less powerful, but more durable. This solution is not for all problems, but it shows that there should not be a blind race for parameters.

Application and typical installation errors

The main niche is pre-cleaning of pulp before fine screening or flotation. The goal is to remove large ferromagnetic inclusions that wear out equipment further down the chain. A common mistake is installing a filter in a gap in a gravity pipeline without taking hydraulics into account. If the flow is too fast, the particles simply skip the magnet's range of action. If it is too slow, silting occurs. The optimal speed has to be selected practically, often by trial. Once we set up a line where the customer required to installmagnetic-mechanical filterdirectly after the crusher, at the exit of the coarse fraction. It would seem logical to catch the metal immediately. But vibration from the crusher was transmitted to the filter housing, loosened the vibrator mounts, and the system failed every few weeks. I had to move it a meter further, to a shock-absorbing support, and add a flexible insert.

Another point is staff training. The device seems simple, but if the operator does not understand the principle of the joint operation of the magnet and mechanical cleaning, “optimizations” begin. They turn off the vibrator so that it does not make noise, or turn off the water for rinsing, saving resources. As a result, in a couple of days the drum turns into a monolithic lump, which then has to be beaten manually. Therefore, in the instructions, especially for models fromLONGI, it is worth focusing not on technical characteristics, but on the consequences of such “optimizations”. It is better to show photographs of clogged nodes - this works more clearly than any graphs.

From practice: at one of the slag processing enterprises they tried to use a filter for purposes other than its intended purpose - to extract finely dispersed magnetite from dump tailings. The device, designed for large particles, quickly became clogged with finely dispersed sludge, and mechanical flushing could not cope. I had to stop the process and clean it manually every few hours. It was a failed experiment that showed that there are no universal solutions. Everyonemagnetic-mechanical filterdesigned for a specific particle size range and feed rate. Ignoring this is a direct path to downtime.

Maintenance: what is not written in the passport

The documentation usually indicates periods for replacing consumables and checking components. But life makes adjustments. For example, wear of rubber seals in the washing area. Manufacturer, sameLONGI Corporation, may give a guarantee for 5000 hours, but if there are abrasive suspensions in the water, the rubber wears out much faster. The first sign is leaks at the joints. If they are not noticed in time, water begins to get on the bearing units of the vibrator, and then repairs become expensive.

Another hidden aspect is magnetic field control. Over time, especially with temperature changes and shock loads, permanent magnets can lose strength. This is not an overnight disaster, but a gradual process. Large plants have teslameters for testing, but many medium-sized plants do without it. As a result, the capture efficiency drops by 10-15%, and this is attributed to “deterioration in the quality of raw materials”. I recommend taking measurements at least once a year, especially if the filter operates around the clock. On the websiteljmagnet.ruThere are sometimes technical bulletins on this topic in the support section, it's worth keeping an eye on.

Separately - lubricant. The vibration mechanism requires specific compounds, often with high adhesion, so that they do not wash out. Using the wrong lubricant (just “any kind of grease?”) will cause the eccentrics to jam. I remember an incident in a coal mine where a mechanic, with the best of intentions, filled the knots with grease. A month later, the vibrator stood up like a stake; when disassembled, there was a dense, frozen mass inside, mixed with coal dust. Cleaning and replacement took three days.

Choosing equipment: what to look for besides price

Price, of course, is an important factor, but if you take a cheap device, then the savings can result in constant costs for repairs and downtime. When evaluating a proposal, for example, fromLONGI, you need to request not only general catalogs, but also test reports on a specific type of raw material. The company, established back in 1993 and specializing in mining equipment, usually provides such data when it comes to a serious supply. Their Fushun facility, with an area of ​​140,000 m2 and a staff of engineers, is not just words, it means they have their own production and testing facilities.

Key parameters for the request: actual pulp performance (not water), maximum permissible particle size, material of contact parts (usually wear-resistant steel or polyurethane) and, very importantly, the method of discharging the captured product. There are systems with manual discharge, and others with automatic discharge into the bunker. For continuous processes, the second option is preferable, but it is more complex and expensive. You need to consider what is more profitable: paying more for automation or maintaining an additional worker for cleaning.

Don't neglect the issue of spare parts. Find out how accessible key components are - drums with magnets, vibration motors, nozzles. If you have to wait a month for delivery of a simple gasket from abroad, this is a serious risk. From local manufacturers who have both?Shenyang Scientific Electromagnetic Co., Ltd. LONGJI?, a developed network, this is usually easier - the spare parts warehouse is often located in the region.

Perspectives and personal conclusions

Technology does not stand still. Systems with electromagnets are emerging, where the field can be adjusted, or combinations with metal sensors for more selective selection. But classicmagnetic-mechanical filteron permanent magnets will be in demand for a long time for its simplicity and reliability in basic tasks. Its evolution is moving more towards materials (more resistant coatings, composite gratings) and control systems (the simplest PLC for monitoring washing cycles and blockage signaling).

The main conclusion that can be drawn from experience: this device is not “set it and forget it”. It requires understanding, attention and proper integration into the technological chain. Its effectiveness is determined by 30% by the manufacturer, and 70% by operating conditions and proper maintenance. Blindly copying someone else's successful experience without taking into account the specifics of your own raw materials and water almost always leads to disappointment.

In the end, any equipment, even the most advanced, is just a tool. And just as you can hammer in a nail or knock off a finger with a hammer, so withmagnetic-mechanical filter. Knowledge of its strengths and weaknesses, attentive attention to detail in the process of work - this is what turns it from a piece of hardware in a box into a stably working production element that lasts for decades, like some devices from the sameLONGI, regularly performs its simple but vital task.