UNEX has modernized the large mining equipment KU 800 in the Sokolov Region

The repair took 235 thousands of hours of labour within 14 months

After a complete overhaul and modernization, the engineering-metallurgical company UNEX passed the large-scale equipment KU 800/12 back into operation; this equipment is running in the Jiri Brown Coal Quarry in Vintirov, in the Sokolov Region. Using this large-scale machine, the mining company Sokolovská uhelná excavates here around 6,5 million tonnes of coal every year.

"In total, 21 units of large-scale equipment series KU 800 were produced in Uničov so far, while ten of them are still operating in the Czech Republic and in the Russia and Ukraine," says the designer, Petr Hlavac, who led the overhaul and modernization of KU 800/12. "These are very reliable machines, capable to accomplish a sound piece of work in the surface mining. A machine that went through 30 years of mining, and that we have modernised for Sokolovská uhelná, will continue in operation until 2035, i.e. during the entire extracting period anticipated for the Jiri Quarry."

The large-scale equipment KU 800/12 undergone the last overhaul in 1996, and the tip of the machine has been refurbished in 2003. Over the last 20 years, it removed 169,754,651 m³ of overburden.

The condition of the machine before the reconstruction corresponded to its past operation time: roller and slide rollers came to the end of their useful life and had to be replaced, together with other worn mechanical parts and the main cables. The replacement was required also at the machine wiring harness and the control system. Repair of the machine by the companies UNEX and Bohemia Müller (electro work) started on 9th September, 2016, and lasted longer than 14 months. The assembly work was completed on 27th November, 2017 and excavator was handed over to permanent use on Monday, 15th January 2018.

"The repair on KU 800/12 took about 235 thousand hours of work by specialists from both cooperating companies. Up to 108 workers were working on the machine together at one point. Among other things, 78,625 meters of new cables have been laid down, and 1,600 pcs of eyes for the rollers of the conveyor lines have been specially cast. Altogether, 45 companies were involved in the subcontracts for technologies and products," describes Petr Hlavac the scope of the project. "During those modifications, we often need to handle parts weighing dozens of tonnes. In addition to the maximum caution, we also use the knowledge of these machines as their historic manufacturer, as well as the experience with their servicing, repairs, and modernization; the company UNEX is the only one within the Czech Republic that has the experts with such skills."

In the course of the overhaul, the machine has been equipped with hydraulically controlled brakes of the bucket wheel, and these are also fitted with sensors for monitoring the wear at the brake pads. This type of brake system has been used in the Czech Republic for the first time.

The convenience for the operators increased; for example, thanks to the air-conditioned cabins with a new video system and communication devices. The exact location of the machine is determined by an accurate GPS device and a set of clinometers. KU 800/12 also has its own Wi-Fi Network, and the electronic fire alarm has also a new system.

The large-scale equipment KU 800 from Uničovské strojírny (re-named UNEX) is one of the largest self-propelled machines produced by man. The length of the axis is over 170 meters and height 52 meters. The wheel of the excavator has a diameter of 12.6 meters and is fitted with 15 buckets, each with volume of 1,000 litres. The weight is around 4,400 tonnes, which corresponds to, for example, 131 aircrafts of 737 Boeing size. Even with this weight, the machine is able to move independently: using special skids, it makes one step per minute with length three meters.