Lifting electromagnet

When they say “lifting electromagnet,” many immediately imagine just a powerful piece of hardware with a coil that turns on and attracts a crowbar. But this is superficial. In fact, this is a whole system where the magnet itself is only an executive organ. And the main mistake of beginners in the workshop or when choosing equipment is precisely underestimating this. They think that the greater the tearing force according to the passport, the better. And then they are faced with the fact that the plate comes off, but sways along the way, or the winding on the old MP-42 overheats after two hours of operation, although according to the schedule it should last longer. I went through this myself when ten years ago I took over a site with a fleet of such electromagnets. The certificates for the part were lost, and it was necessary to determine experimentally, almost by touch, at what thickness of rolled products and with what cycle they could work without risk to the crane and people.

From passport data to a real site

Look here. We take a typical round lifting electromagnet for rolled steel. The documentation indicates the lifting force, say, for slabs of a certain thickness. But this is under ideal conditions: dry, smooth, clean metal. But in reality? Rolled products may have a layer of scale, rust, and may become warped. And this is where the fun begins. The adhesion force drops sharply. I remember an incident at one of the transshipment bases where they complained that the magnet “doesn’t pull?” declared weight. We arrive and look - and there is a layer of ice frozen between the sheets of rolled metal. The magnetic field passes through the ice, but the contact is broken. I had to explain that the problem was not with the equipment.LONGI Corporation, but in storage technology. This is to the question that exploitation is not just about pressing a button.

Or another nuance - temperature conditions. Standard models are designed to operate up to +60°C (for some manufacturers - up to +80°C). But if you load hot workpieces, say, at a temperature of +200°C, then the magnet will very quickly fail. The winding will overheat and the insulation will float. For such tasks, special heat-resistant designs are needed, with forced cooling or special materials. At the sameLONGIThere are such solutions in the range, but they are naturally more expensive and require more complex connections. Not every customer is ready to understand this right away; they often try to save money, and then incur much greater losses on downtime and repairs.

Another practical point is the shape of the poles and the configuration of the magnetic system. For long products, such as rails or beams, not round, but rectangular or even U-shaped magnets are often used. So that the distribution of force is uniform along the length of the load and there is no distortion when lifting. We once experimented with a custom order fromLJMagnetfor gripping large steel drums. There they had to make a system of two independent electromagnets with a common frame and separate controls. To be able to compensate for possible load distortion. The work is painstaking, calculations, drawings, testing on a bench. But in the end, the system worked flawlessly for several years.

?Brain? systems: control units and safety

The magnet itself is a rather primitive thing. All the most important things happen in the control cabinet. It is from there that the current for magnetization is supplied, and protection against load dumping in the event of an emergency power outage is also implemented there. Previously, on old Soviet systems, there were often just contactors and capacitor banks for energy storage. Now, of course, everything is based on thyristors and microprocessor control. But the essence of the task has not changed: to ensure smooth magnetization and, what is critically important,demagnetization.

The problem of residual magnetism is a separate pain. If you simply cut off the power, the load may not fall off, but “stick?” to the poles. Or, worse, not completely fall off and break off when transferred. Therefore, in modern blocks, the same ones that supplyLONGI, an algorithm is laid down for supplying damped alternating current to remove residual magnetization. But there are nuances here too. The settings of this algorithm may depend on the mass and geometry of the load. There are no universal meanings. At a new facility, adjustments are always required, sometimes by trial. It happened that the default parameters were set, but the steel sheet was still removed with a crowbar after shutdown. I had to “play around”? with the frequency and amplitude of damped pulses.

And of course, diagnostics. A good control unit should not only work, but also report problems. Overheating of the winding according to the temperature sensor, voltage drop in the network, insulation failure - all this should be recorded and displayed either by a light alarm, or, better yet, on a display or in a higher-level system. Large metallurgical plants are now striving to integrate such equipment into a common SCADA. So that the dispatcher can see the status of everyonelifting electromagnetson the site. This is not just a question of lifting a load, but of building a technological chain.

When the service life comes to an end: maintainability and spare parts logistics

Nothing lasts forever. Even the most reliable electromagnet will require attention over time. Most often ?sick? winding - interturn short circuit due to vibration and temperature changes, insulation failure. The case, if it is not sealed, can collect moisture, especially when working in open areas. Renovation is always a story. You can rewind the coil on site, but this is handicraft, and the quality of the insulation will be worse than the factory one. Better - replacement with a new one or major repairs from the manufacturer.

This is where the reputation and presence of the manufacturer is important. If a company likeShenyang Scientific Electromagnetic Company LONGJI, has been on the market since 1993 and has its own serious production (with an area of 140,000 m2 and more than 1,200 employees, the majority of whom are engineers and technicians, talking about the scale), then spare parts and repairs are usually easier. They have accumulated a database and have standard solutions for restoring even quite old models. This is critically important for enterprises where the equipment fleet has been in use for decades and suddenly changing everything to a new one is unaffordable.

I came across the opposite situation, when it was impossible to find even a drawing of a coil for an electromagnet from some little-known manufacturer. I had to take measurements, calculate the wire cross-section and number of turns myself. Risky. Because an error in calculating the current strength or thermal conditions could lead to failure of the new control unit. Therefore, now when purchasing new equipment, one of the key factors for me is the availability of service support and a guarantee that in 5-10 years I will be able to obtain adequate components for it.

Specific application in the mining industry

Mention thatLONGIdevelops and produces mainly mining equipment - these are not just words in the company description. This imposes specifics on theirlifting electromagnets. In mines and processing plants, conditions are harsher than in a regular metal warehouse. Dust (often abrasive and conductive), humidity, vibration, limited space for crane maneuvering.

For such applications, explosion-proof versions (Ex marking) are often required. The design of the housing must prevent sparking, and the materials must be resistant to aggressive environments. In addition, in the mining industry one often has to deal not with neat slabs, but with large pieces of scrap, scrap buckets, and worn-out equipment elements. The shape of the load is unpredictable. Therefore, sometimes they use not standard electromagnets, but so-called magnetic washers or grips with a combined action (magnet + mechanical hook).

The productivity of 4,000 units of equipment per year, which the company claims, suggests that they work not on piece orders, but on serial orders. But at the same time, knowing the specifics of the industry, they most likely retain the opportunity for individual projects. For example, a magnet for extracting metal inclusions from ore on a conveyor or a special electromagnet for installing heavy equipment in cramped mine conditions. This is engineering, not just selling hardware.

Thoughts out loud about the future of such equipment

Where is everything going? In my opinion, the trend is towards intellectualization and energy efficiency. Systems are already appearing that use current and voltage sensors to estimate in real time the mass of the lifted load and its position relative to the poles. This allows you to optimize the work cycle and prevent crane overload. Another trend is the use of electrically controlled permanent magnets (hybrid systems). They consume energy only at the moment of state switching (?on?/?off?), and not the entire holding time, like classical electromagnets. This gives huge savings on electricity in continuous cycles.

But implementing something like this is always a question of cost and payback. For a small scrap yard, purchasing a state-of-the-art system may not be justified. But for a large metallurgical plant with a continuous cycle - quite. Manufacturers such asLONGI Corporation, you need to balance between offering cutting-edge solutions and supporting a reliable, time-tested fleet of equipment for your clients. Judging by their history and scale, they are up to this task.

In the end, back to the beginning.Lifting electromagnet- it really is a system. From choosing a model and control unit, from correct installation and configuration to proper operation and timely maintenance. And experience here is an irreplaceable thing. It cannot be replaced by a beautiful passport with numbers. It is this experience, often accumulated through mistakes and emergency situations, that allows a seemingly simple piece of hardware with a wire to work for years, safely and effectively lifting tons of metal. And companies that understand this practical side and can support the client not only with equipment, but also with knowledge, remain in the market for a long time.