Restoring the drum to new condition

When the acting chief designer of the Foundry and Mechanical Plant, Oleksiy Usach, talked about repairing the magnetic separator drum for the mining department of ArcelorMittal Kryvyi Rih, I remembered the toothpaste advertisement, where a young man from the future points to a young smiling beauty and says that this is his grandmother, and her teeth are all that she has left of her own. The same goes for the drum. It received more than 90 percent of new components. That is, in fact, we have a new product at the output. The drum was made for the ore processing plant No. 1. I found it installed on the test stand. It passed the test well. In appearance, it is an ordinary cylinder that rotates around its axis. But the specialists of the LMZ explained that the product is very difficult to manufacture, and the main difficulty lies in the filling.

“Thanks to the separator drums, iron ore is enriched. The task of the drum is to select metal particles from the pulp, that is, a mixture of water and iron ore crushed to a very fine fraction,” explains Oleksandr Usach. “For this, magnets are installed inside the drum. It rotates in a bath with pulp, the particles are attracted and stick to the magnetic side of the drum, and are removed with a special comb. We performed such a repair for the first time, in fact, by making a new drum. And it was not easy. Of the old components, only the yoke remained - a metal structure that holds the magnets. It was overhauled.” Initially, the LMZ design bureau developed detailed drawings of the drum components and the product as a whole. Stanislav Garsh, Yevgeny Kalabin, Volodymyr Tyshchenko and others worked on this together with Usach. Then, together with the service of the chief technologist Yevgeny Konovalov and the department of the chief technologist, the technology was developed. And then the LMZ workshops got down to work. The shell was made of sheet metal by specialists from the metal construction workshop. They cut the metal, bent it on rollers, and welded it. “We received a blank for the shell and gave it the correct cylindrical shape, because it is impossible to make a correct cylinder on rollers from thin metal,” says the acting head of RMC-1 Igor Kormakov. “To do this, a device with rollers was made for the boring machine, with the help of which the surface of the shell was rolled out from the inside, obtaining a correct cylinder. This work was performed by machine operators of a wide profile, Volodymyr Kovbaskin and Vyacheslav Kildyushov, our great optimist who always inspires colleagues, even when everything does not work out. The pins, that is, the supports with which the drum is attached, were made from blanks forged in the forging section of our workshop. Our specialists also made the side covers and gears. And when everything was ready, the repairmen Viktor Glavny, Yegor Malyugin, Igor Serdyuk, Igor Komakha, welders Valentin Karmanov, Oleksandr Grisha and others got down to business.” Assembling the elements into a single unit is perhaps the most difficult part of this project. Connecting everything, maintaining distances, angles, gaps, centering and many other difficulties. For example, the side covers must close the drum hermetically, and the distance between the magnets and the shell must not exceed 3 mm. During testing, it turned out that one of the magnets was rubbing against the housing. We had to disassemble and reassemble it, because the main thing is quality. And in general, installing the magnets is a separate story. “This was our first time dealing with magnets,” continued Igor Kormakov. “First, we checked the old magnets for the strength of the magnetic field, for this we purchased a device called a magnetometer. The rejected magnets were replaced. We determined the poles of each magnet, because they need to be installed in a certain sequence of “pluses” and “minuses”. Our specialists worked hard to install them, because in doing so they had to overcome the repulsive force of the magnetic field. And when the magnetic force of attraction began to act, on the contrary, the magnets, which rushed headlong to meet other magnets, had to be held down so that they stood correctly. This is just a quick story, and the process was long and laborious, but we managed it! ” Currently, the drum has successfully passed the tests and is waiting to be sent to the customers - ore processing plant No. 1. The head of the factory, Oleksandr Denisko, has high hopes for such repairs. “In general, the drums are repaired by a contractor for us. We hope that the drum will work well, and that this is only the first such repair. This will help us reduce the cost of equipment repairs,” Oleksandr Denisko concluded.