LOAD & HAUL
routing work for many years. In addition to the 2500 SM surface miner that the company has used in Ube since 2012, in 2018 the service provider decided to add a second miner – the Wirtgen 2500 SM Vario. T e surface miners allow Okumura
to create extremely stable and steep mining walls with narrow benches for Ube Industries, thus safely expanding the mining area. As a result, the open-cast deposit can be fully exploited. “Using Wirtgen surface miners allowed us to mine the southern side of the Maruyama region. T at would have been impossible with the blasting method,” says Shodai. By now the quarry’s outer boundary wall have been gradually extended by 10m in the direction of the residential area. According to Gaku Watanabe, general manager of Wirtgen Japan, this could increase the mine’s potential many times over. T e Wirtgen Group’s Japanese sales and service company has been supporting Okumura since the beginning of the partnership. Another advantage of surface mining is the central-drum concept. T e cylindrical cutting drum is located close to the machine’s centre of gravity, resulting in maximum cutting performance and exact cutting depths in hard rock. T e result is an ideal, uniform material and a fl at surface that, due to its stability, can easily be driven on by construction site vehicles.
In addition, theses surface miners
are extremely environmentally friendly compared to conventional drilling and blasting methods. Vibration-free mining without drilling and blasting signifi cantly reduces the amount of dust and noise produced. T e 2500 SM Vario used in Ube was specially modifi ed for the customer to meet these requirements. T e sealed cutting drum housing as well as the specially equipped sound attenuation and dust separation fi lter additionally reduce dust and noise in the immediate vicinity of the residential area.
THE SPECIALIST FOR ALL TYPES OF HARD ROCK In 2017, the 2500 SM equipped with a 2.5m cutting drum was used on 210 days and was able to extract almost 60,000 tons of limestone over an area of 4,000m². By adding a 2500 SM Vario, the company was able to mine a total of 32,000m³ of limestone in 2018 – a signifi cant increase from the 22,000m³ mined in 2017. T e 2500 SM Vario is particularly suitable for hard rock, as is the case in Ube. T anks to the central-drum concept, the drum is located very close to the centre of gravity of the 135-ton machine, which allows it to penetrate into harder rock layers. T e Vario miner gets its name from its variable control system. Its design allows the drum’s torque to be adapted to
Wirtgen surface miners allow limestone to be mined in Ube Isa quarry in an environmentally friendly way that doesn’t aff ect the surrounding area
The 2500 SM Vario surface miner guarantees stable and high-precision mining operations – and can create quarry faces at up to a 70° angle with extremely narrow benches
the properties of the rock. T is prevents excessive wear on the bits, extending their service life. In addition, the miner can be operated at diff erent milling drum speeds, which makes it highly versatile when used in diff erent external conditions. T e machine’s direct drive makes it particularly effi cient. And the turbo coupling mounted before the drive unit dampens vibrations, is extremely wear-resistant, and requires little maintenance.
ENHANCED MACHINE OPERATOR SAFETY T e 2500 SM Vario was also optimised for the quarry in Ube in terms of machine operator safety. Instead of controlling the miner from the cab on a steep slope, the operator can easily operate the machine with a remote control from outside the machine. T is is a huge advantage, particularly on slopes as steep as 70°, as the machine operator is not only in a safer location but also has an even better view of the area being mined. Okumura originally used standard picks with a shank diameter of 38mm for the surface mining operations in Ube. Due to the very hard limestone with a compressive strength of 40 to 80 MPa, however, the picks suff ered so much wear that they decided to use picks with a larger diameter shank. Naturally, Wirtgen off ers an appropriate solution for this as well. T e picks with a diameter of 42mm in combination with the HT15 tool-holder system are perfect for applications in hard rock and maximise pick utilisation. T e pick holder’s exchangeable base also dramatically reduces the holder’s changeover time and increases the availability of the machine for limestone mining operations.
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