self-emptying iron separator

When you hear “self-discharging iron separator,” many people immediately imagine a standard electromagnet above a conveyor. But the point is not in the magnet itself, but in the system for cleaning it - this is where the main mistakes in selection and operation lie. People often think that since it is “self-unloading”, they set it and forget it. In practice, the majority of breakdowns and downtime are associated with this unit, if selected without taking into account real conditions. For example, for a processing plant with wet ore and for a coal warehouse with seasonal humidity, these will be different devices, although the principle is the same.

Design: what is hidden behind the name

Essentially, this is an electromagnetic separator, where a magnetic system (usually a horseshoe or segment) is automatically removed from the material flow area for cleaning after metal has been selected. The key word is “automatically”. The mechanism can be chain, rack and pinion, or based on hydraulic cylinders. For example, at one of the old facilities we tried to adapt the drive from a decommissioned unit - it seemed to save money, but in cold weather the chain began to “walk”, and unloading was incomplete. I had to redo it with a normal gear motor.

An important nuance is the metal discharge system. There is belt self-unloading, when the magnet moves over a separate short belt, and there is vibration or scraping. For large ferromagnetic pieces (bolts, pieces of reinforcement), tape is better. For small chips, especially sticky ones, a scraper is sometimes more effective, but it wears out more. This is often not written in the specifications; you have to look at the experience of similar productions.

Products worth mentioning hereLONGI Corporation. On their websiteljmagnet.ruit is clear that they are focusing on mining equipment. They have such separators in their assortment, and judging by the descriptions, the design takes into account harsh operating conditions - protected bearing units, abrasion-resistant elements. Company since 1993, and their engineers have probably encountered the same problems with freezing or sticking clay that we do in the field.

Operating experience: where theory diverges from practice

The main lesson is that you cannot install an iron separator “according to the catalogue”. Once we ordered a device with a standard degree of protection for a crushing shop. They did not take into account the constant vibration from crushers and dust, which was not just abrasive, but highly electrically conductive due to its moisture and salt content. Six months later, problems began with position sensors and contacts in the control cabinet. I had to order a box with increased protection and seal the connectors - additional costs and downtime.

Another point is current performance.Self-discharging iron separatorat the moment the electromagnet is turned off to dump the metal, it creates voltage surges. If the power supply network at the facility is rather weak (old substations), this may trigger the protection of neighboring equipment. We now always request a load diagram from the power engineers and, if necessary, install stabilizers or matched power supplies. This is a small thing, but it prevents conflicts with the chief mechanic.

The operating mode is also important. If the separator operates in a continuous cycle (for example, during coal loading), then self-cleaning intervals must be strictly tied to the presence of metal. Metal detector sensors help, but they also fail. Sometimes it is easier and more reliable to set up timed unloading based on experience, say, every 20 minutes, even if there is visually little metal. Otherwise, the magnetic system gets clogged. and ceases to effectively capture new particles.

Integration into the production line

This is not an independent unit, but an element of the system. Its installation is not only about mounting it on a frame above a conveyor. It is necessary to provide a place for the dumped metal (trolley, bunker) so that it does not accumulate and create a danger. On one of the conveyors with a steep slope, we made an oversight - a discarded piece bounced off and damaged the return branch of the belt. I had to install a protective reflector cover.

The height of the suspension and the distance to the tape are parameters that are often taken as ideal in a project. But the tape sags, sometimes it “pops”, and the material piles up. If the gap is too small, snagging may occur. If it is large, the magnetic field and efficiency decrease. After installation, we usually carry out a test with control ferromagnetic samples of different sizes and at different points along the width of the tape to find the optimal height. Sometimes you have to raise or lower it a centimeter or two, and this affects the design of the portal.

Interaction with a metal detector. Ideally, the detector gives a signal to stop the belt when a large metal is detected, andiron separatorextracts it. But on high-speed conveyors, stopping is a loss of productivity. More often they use a scheme where the detector only marks the area with metal, and the separator operates in enhanced mode or performs extraordinary unloading precisely at the moment of passing this area. Setting up such a link takes time and patience.

Maintenance: to avoid becoming an ?iron collector?

The most common mistake is the lack of regulations. The device seems to be self-service. But you need to regularly check the tension of the chains or drive racks, the wear of the contact groups (if any), and the insulation condition of the electromagnet windings. Once a quarter, we definitely measure the insulation resistance - a drop may be the first sign of moisture penetration and a future interturn short circuit.

Lubrication. Bearings in the drive and on the shafts are often exposed to dust. The grease picks up the abrasive. We switched to a lubricant with solid lubricating additives (such as graphite) and increased the service intervals. But this required consultations, including with manufacturers. On the websiteLONGI CorporationIn the product section you can see that they offer different versions according to climatic conditions. I think their service engineers could make specific recommendations on lubricants for their equipment, because as a large manufacturer producing 4,000 units of equipment per year, they probably have well-established protocols.

Maintainability. Once we came across a device where in order to replace the brushes (on the old model with a sliding contact) it was necessary to dismantle half of the structure. The downtime amounted to almost a shift. Now, when purchasing, one of the key issues is access to key components for quick replacement. It’s good when the casing is bolted and not welded, and there are installation hatches.

Choice and economics: more expensive is not always more reliable

The price depends not only on the power of the magnet. Expensive imported models may have complex electronics that are not adapted to our voltage and temperature changes. Sometimes a domestic or, say, Chinese analogue from a trusted manufacturer with a simple relay control circuit is more reliable and cheaper. As is the case withLONGI- an enterprise with its own developments and a production site of 140,000 m2, most likely, can offer equipment adapted to the realities of the post-Soviet space, and at a more competitive price than European brands.

It is believed thatself-discharging iron separatorpays for itself by reducing damage to crushers, shredders and conveyor belts. This is true, but you need to count accurately. Not only the cost of repairs, but also the downtime of the line. One incident of large metal entering a medium crusher can put it out of action for several days. The cost of downtime is tens of times higher than the price of a good separator.

In the end, the choice is always a compromise between initial costs, maintenance costs, reliability and maintainability. There is no universal solution. You need to clearly understand what material you are working with (size, humidity, abrasiveness), what the intensity of the flow is and what the real conditions in the workshop are. And the main thing is to take the time to commission and adapt the equipment to your specific task. Then this device will become a truly working link, and not a source of headaches.