Face Excavators: Power in the Raw

Used at the working face, in particular when the extraction is done directly without resorting to mining, these excavators are distinguished by their load capacity and their digging force. Two parameters which, together with the operator’s work environment, directly condition their performance and guarantee rapid cycles.

Face Excavators: Power in the Raw

The acquisition of a Kobelco SK 850 LC-10 excavator by Bellin TP, a company of the Spie batignolles group, illustrates this approach. The machine, which is positioned in the segment of 85 t shovels, delivers an ISO 14396 power of 380 kW @ 1850 rpm and can be equipped with a 5.4 m bucket3 of capacity. Specifications perfectly suited to quarry applications. The Charier Company’s approach proceeds from the same logic. In the fleet of quarry excavators, which include around ten units, the two Volvo EC 750 E constitute the top of the range. Initially acquired for discovery work in the Villeroy quarry (77), the two excavators have since been redispatched within the group. One at the face of the Mariais quarry, the other being used for major earthworks. The latter, in service since 2017, has worked more than 7,000 hours. These two excavators, operational since 2019 respectively, have been selected for their productivity and operational performance which contribute to maximizing the return on investment. The SAE J1149 breakout force, with 6.6 m boom, 2.9 m arm and 12.1 t counterweight, reaches 323 kN. Their reinforced and ultra-reinforced buckets supplied by the Swedish manufacturer have anti-wear plates that protect them from penetrating into compact materials. “We ensure the consistency of the working face and the transport equipmentcomments Arnault Peugniez, Equipment and Purchasing Director at Entreprise Charier. The production at the working face is conditioned by the transport capacity and the throughput of the crusher, which must never enter into saturation. » By moving upmarket, the carrier’s objective is to lower the cost per tonne produced. As such, the energy efficiency of the excavator is paramount. Consumption is one of the main purchasing criteria, as part of a structured approach based on the notion of total cost of ownership, integrating maintenance costs, consumption of fluids, after-sales service and resale value. Each investment is subject to consultation with the company’s four main suppliers (Caterpillar, Komatsu, Liebherr and Volvo CE).

Specifications

Demanding on the specifications of his machines, the operator is increasingly asking for modifications/adaptations to be made in the factory. The key is better integration and shorter lead times. The same rigor is applied to the selection and assembly of accessories, including buckets, which are systematically validated by the dealer. A response to problems of installation and good adequacy bucket/carrier, “the career trend is to add a lot of material to protect against abrasion”, a source of overweight, and therefore premature wear of the jib foot axles. At the face of the Mariais quarry, in the town of Donges (44), the excavator, operational since 2019, displays nearly 5,000 hours. It demonstrates optimal availability, which is essential to meet production targets, thanks to permanent technical monitoring provided by the company’s workshop. Consumption commitments are in line with projections, confirming the operator in its investment.

Productivity

Thanks to the renewal of its fleet of production equipment, Carrières Champenoises has acquired a Liebherr R 976 Litronic mining shovel from MTPS (Toufflin group), which provides all repair and repair work. ‘maintenance. By signing for a period of five years or 7,500 hours, the first of the two terms reached, which corresponds to his rate of replacement, the carrier frees himself from major technical interventions. The massive limestone rock quarry on which the excavator operates being equipped with a material processing installation without washing, the extraction at the working face always requires healthy materials to be sent to the crusher. “We are dependent on the weather conditions but also on the different geological layers and the demand of our customers which fluctuates throughout the year, explains Sébastien Derez, quarry manager at Jully-sur-Sarce (Aube) and operator at Carrières Champenoises. In this context, the face shovel conditions the activity of the site. » The quarryman opted for the Liebherr R 976 Litronic. With an operating weight of nearly 100 t, this model, which develops a power of 400 kW, is sized for quarry extraction. Thanks to an optimized hydraulic system and a Tier 4 Final engine, the machine delivers maximum productivity while guaranteeing the versatility expected by the operator. For this, the latter has a “large volume” recovery bucket with a capacity of 5,200 l, a ripper bucket specially designed to attack the hardest blocks of 3,750 l and a ripper tooth. Equipment designed and manufactured by Liebherr – such as the SW 90 hydraulic quick coupler – which allows you to work efficiently and achieve the expected daily tonnage. The operator assures him: 20 seconds are enough for him to change accessories. “The whole is efficient and well sized in relation to the site because it was studied with the teams from the Colmar plant’s design office following a visit to the quarry. I work in steps of 3.50 m in average height. To guarantee the cleanliness of the materials at the hopper, I can also work on landings of only 25 cm. Depending on the layer of material, I may have trouble ensuring the flow despite the power and nervousness of the shovel, the last meters at the bottom of the quarry being mined because they are too hard », reports Sébastien Derez. To have maximum breakout force, we started with a 7.20 m long boom and a 2.90 m arm, a “short” piece of equipment able to withstand stresses when working with a bucket or to the ripper tooth while exploiting the digging power and breakout force of the carrier.

Production cycles

Among the technical specificities that convinced the operator: the double cylinder of the dipperstick sized for intensive and difficult applications, the kinematic chain, the hydraulic power and the new cab. At the operator’s request, the hydraulic return is made directly to the tank, to avoid water hammer when working in shifting mode. Other selection criteria, the responsiveness of the distributor as soon as the operator requests it, the availability of spare parts and the speed of intervention of the after-sales service. Decisive parameters within the framework of the service contract taken out in order to guarantee optimal availability of the machine and to ensure daily production. A sustained yield which, on “good days”, can reach 2,800 t without the machine forcing it. On average, the daily consumption amounts to 550 l. The latter is impacted by the hardness of the geological layers encountered, the hourly average being around 80 l since its start-up in July 2021. Apart from the replacement of two injection pumps, there are no major concerns to report. The shovel, which is constantly monitored to keep it in working and safe condition, ensures production cycles in line with the operator’s expectations. With more than 1,400 hours worked, the operator experienced the comfort of the cabin and the pleasure of driving. In fact, the definition of the equipment and the design of the tools are decisive in the choice of operators. In consultation with the distributor and the manufacturer, the various arbitrations must be decided according to the carrier’s priorities. This is the sine qua non condition for arriving at a product definition that is well suited to the constraints of the site and the targeted production objectives.

Doosan DX 1000 LC-7: the excavator of all superlatives

With its operating weight of 97 t, its attack height of 12,425 mm and a digging reach of 12,430 mm, this model rises to the top of the range of the Korean manufacturer. Its bucket and arm breakout forces are measured at 48.2 t and 40.8 t respectively. The power developed by the 6-cylinder Perkins engine reaches 469 kW @1,800 rpm.

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Face Excavators: Power in the Raw


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