magnetic separator device

When you hear “magnetic separator device?”, the first thing that comes to mind is a rotating drum with a magnet inside, and that’s it. But this is just the tip of the iceberg, and this is where the main mistake of beginners or those who order equipment based only on the price tag lies. In fact, if you take it apartmagnetic separator deviceBasically, this is a whole system of interconnected units, where a problem in one seemingly minor element - for example, in the unloading system or compaction - can negate all the work. I myself have encountered many times when a client at a site complains about low extraction, and the reason turns out to be not the strength of the magnetic field, but an incorrectly calculated gap between the drum and the casing or worn out seals that suck in the pulp. It’s these nuances that you rarely see in catalogs, but which are critical in practice, that I would like to talk about.

Structural basis: what is hidden behind the steel body

Let's take a classic drum separator for wet enrichment. Yes, the heart is a magnetic system. But which one? Previously, there were ferrite magnets all over the place, and they are still installed in many places. But if we are talking about permanent magnets, then now it is almost always NdFeB - neodymium. The strength is different, the stability is higher. But here's a key point that is often missed: how is this system secured inside the drum? It's not just bolted on. There must be an absolutely rigid, unchangeable structure, because any vibration or displacement will lead to a change in the magnetic field on the surface. And this will directly affect the quality of separation. I once saw a separator in an old factory that was “spitting”. magnetite. They opened it and it turned out that the fastenings of the magnetic blocks had weakened due to constant vibration, the blocks sank a couple of millimeters. The field was distorted, the separation boundary floated.

The drum itself. It looks like just a hollow cylinder. But the material, wall thickness, method of connecting the shell to the end caps are all important. If you use a drum with too thin a wall to work with abrasive materials (for example, iron ore), it will quickly wear out. And replacement means stopping the line for at least a day. Therefore, in normal devices, like those that makeLONGI Corporation, special attention is paid to this. On their website (https://www.ljmagnet.ru) you can look, but in the technical descriptions this ?kitchen? not always revealed. The thickness, grade of steel, sometimes even with an internal protective coating, is a matter of experience and understanding of operating conditions.

And the casing. This is not just a tank where everything flows. Its geometry, especially in the area where products are unloaded—concentrate and tailings—is critical. Angle of inclination, shape, location of drain thresholds. If done somehow, a reverse flow occurs, turbulences that carry the already separated particles back to the tailings. I had to modify these components on site with my own eyes, install additional reflectors or adjust the dampers. A casing that is designed perfectly the first time is very rare; it usually requires adjustment to a specific pulp.

Drive and seal system: where problems most often occur

Many manufacturers save money here, but in vain. Drive - gear motor. It would seem like a standard node. But it is important that there is a power reserve and, most importantly, the correct way of connecting to the drum shaft. A rigid coupling means that all vibrations from the motor are transferred to the drum. A flexible coupling or drive through a pulley and belt is better, it dampens vibrations. Vibration for a magnetic system is death. In one of our early projects, back in the 2000s, we installed a separator with a rigid drive from a cheap gearbox. Six months later, increased noise began, and then a drop in extraction. They disassembled it - wear appeared in the bearing units due to constant vibration, the shaft began to beat.

And now about seals, or oil seals. The most painful spot of any rotating apparatus working with suspension. They install ordinary stuffing box packings - they require constant tightening, they leak, and they get filled with abrasive. A modern solution is mechanical mechanical seals. But they are also different: according to the material of the friction pairs (silicon carbide, aluminum oxide), according to the design (single, double). For severe conditions where there is a lot of sand in the pulp, a double seal with flushing fluid is better.LONGI Corporation, as a manufacturer with a history dating back to 1993 and a huge fleet of manufactured equipment (more than 4,000 units per year - a figure that speaks for itself), usually offers different options to order. But the client often chooses the basic one to save money. And then he suffers with leaks on the spot. It is necessary to immediately install a better seal; it will pay for itself in the absence of downtime.

Bearing units. Must be protected from the ingress of pulp, like the doors of a bank vault. Often they are placed outside the body, on separate stands, connected to the drum through an intermediate shaft. This makes the design more expensive, but increases the service life significantly. If the bearing is located close to the drum, inside the casing, then even with a good seal, sooner or later moisture and dirt will get there. Replacing such a bearing requires almost complete disassembly of the cage. Inconvenient, long, expensive.

Magnetic system: from permanent magnets to electromagnets

Let's return to the main thing - the magnetic system. Rare earth permanent magnets are the standard for most applications. But there are subtleties here too. Pole location, configuration of magnetic blocks (radial, alternating pole). Not only the magnitude of the magnetic field depends on this, but also its gradient—how quickly it decreases with distance. To capture small and weakly magnetic particles, a high gradient is needed. Sometimes for this purpose a special “comb” is made inside the drum. from pole pieces.

But there are times when you can’t do without an electromagnet. For example, when you need to smoothly and within a wide range regulate the field strength directly during operation. Or when you need to create a very strong field to extract weakly magnetic minerals. The electromagnetic system is a different story: coils, cooling system (air or water), power source. Reliability is lower than that of permanent magnets, more difficult to operate, and more expensive. But for specific tasks it is indispensable. I remember a project for the enrichment of red mud, where only a powerful electromagnetic separator could cope. The problem was that the coils overheated; the airflow system had to be modified.

Another nuance is demagnetization. Permanent magnets, especially older ferrite ones, can lose strength over time, especially from overheating or heavy shock loads. Modern neodymium ones are more stable, but also not eternal. Therefore, in critical applications it would be nice to be able to check the field on the surface of the drum with a Teslameter. This is rarely done preventatively, but in vain. A drop in induction of 5-10% may not be visible to the eye, but the extraction is already saggy.

Installation, adjustment and typical operating errors

Here is the field for the most annoying mistakes. Even perfectly mademagnetic separator devicecan be damaged by incorrect installation. The base must be rigid, level, and level. A common mistake is installation on metal frames without a rigid connection to the foundation. The device is “walking?” When starting and stopping, the drive alignment is disrupted. It’s even worse if the separator is skewed relative to the overall pulp flow. Then the loading does not proceed evenly along the entire length of the drum, but from one edge, the sector is overloaded, the material does not have time to be separated and goes into the tailings.

Setup. The most important thing is to adjust the gap between the drum and the bottom edge of the loading tray or between the drum and the bottom of the casing. This gap determines the thickness of the pulp layer on the drum. Too small - the separator will “choke”, the material will not have time to pass through, overflowing. Too large - the layer will be thick, the magnetic field will not be able to pull particles out from the depths of the layer, they will go into dumps. Adjustment is made on the spot, experimentally, for a specific size and density of nutrition. No instruction here will give exact numbers.

Operational errors. The most common is nutritional overload. Technologists, in order to increase the productivity of the site, feed more pulp into the separator than it is designed for. That's it, efficiency drops catastrophically. The second is untimely inspection and replacement of seals. They are waiting for the stream to flow. The third is ignoring extraneous noise and vibration. All this ultimately results in serious repairs. Equipment fromLONGI, judging by their experience since 1993 and the scale of production, is designed for long work, but it also requires a competent approach. Their website has sections with products, but you often learn the real nuances of operation only from their engineers or from experience.

A look towards specific designs and the future

The drum separator is a classic, but far from the only optionmagnetic separator devices. There are roller, pulley (for dry separation), and there are high-gradient separators with a matrix of ferromagnetic wire or mesh for ultra-fine materials. Each has its own area of ​​application and its own design features. For example, in matrix separators, the main headache is counter-current flushing to remove concentrate and prevent matrix clogging.

Where is everything going? The trend is intellectualization. Sensors for monitoring pulp level, bearing temperature, even online magnetic field sensors. This allows you to move from scheduled preventative maintenance to condition-based maintenance. The risks of sudden breakdowns are reduced. The second direction is materials. More wear-resistant coatings for drums, new composite materials for casings, even more powerful and stable permanent magnets.

In the end, back to the beginning.Magnetic separator device- This is far from a primitive unit. This is the result of a trade-off between magnetic efficiency, mechanical reliability, maintainability and cost. An experienced engineer, looking at the design, will immediately see where the manufacturer saved money and where he included a margin of safety. And it is these details, hidden from first glance, that ultimately determine whether the device will work stably at the site for years or will become a headache for enrichers. Like in that old, time-testedLONGI Corporationfrom Fushun, where more than 1,200 people work on the development and production of such equipment, most of whom are educated professionals. Their experience, by the way, often materializes precisely in these non-obvious, but critical nodes and decisions.