Prof K.N. Trubetskoy, Member of the Russian Academy of Sciences Dr.Sc. (Eng.) I.A. Sidorenko, Dr.Sc. (Eng.) A.N. Dombrovskiy (URASIPKONRAS), Min.Eng, M.N. Kotrovskiy (NPKGemosLimited)
In the current international practice of mineral surface mining the major scope of work is performed by excavating machinery loading the mined material onto dump trucks, and the rest is provided by direct dumping methods, mainly in coal surface operations developing flat or gently inclined seams of limited thickness. Both in case of existing mines and in case of new deposits being involved in production mining operators are faced with a continuous growth of mining depths in quarries and opencast coal mines, and this is accompanied by the increasing hardness of rocks, which can be excavated only after loosening by blasting methods. In the Russian Federation the share of excavation with loading onto transport vehicles is increasing continually, and today it accounts for 75% in the coal sector, while in other mineral mining sectors, such as ferrous and non-ferrous metal, diamond and gold, as well construction materials mining it makes nearly 100%.
The natural increase of mining depths at surface operations and less favourable geological conditions of mineral deposits make this advanced and promising method of solid mineral deposit development less economically efficient thus dictating the necessity of new engineering approaches aimed at higher efficiency of mining, including such an important factor as higher benches excavated with the material dumping onto transport vehicles. Meanwhile, over the recent half-century the bucket capacity of power shovels has increased 5-fold, from 3…5 to 15-25 m3 and even more, while their digging height – less than two-fold, from 10 to 16-18 m. Power shovel with a longer boom for upward dumping are not used on a broad-scale because of insufficient bucket capacity and lower performance of such machines.
Therefore, such equipment as draglines becomes rather attractive for excavation and dumping processes, as these machines are able to downward dig high benches (up to and over 30 m), where continuous transport systems are usually used, however, with mined material disposal to inside dumps. Some mines for economic reasons use commercially available draglines for direct dumping to dump trucks and hopper wagons, which payload has increased significantly over recent time. For instance, this technology is used by Luchegorsky opencast coal mine, Severo-Onezhsky bauxite mine, a refractory clay mine of Voronezhskoe RU mining company and at a granite mine of OAO Pavlovskgranit. This technology was also tested at some surface coal operation of the Kuznetsk Basin, as well as at high-capacity Neryungrinsky opencast coal mine. These mines make use of commercially available draglines with 6 and 10 m3 buckets in spite of regular spillage of the material through standard bucket teeth during dumping and significant reduction of the machine performance because of aiming problems at a larger distance from an operator’s cab to a dumping point and a substantial swinging of a bucket over a truck body. As there is a risk of large rock lump hitting the operator’s cab, the personnel is withdrawn from hazardous areas during the discharge of a dragline bucket. At an iron ore mine of the Mikhailovsky GOK with 8 draglines in operation, for the improvement of the field of vision during the bucket discharge the booms of these draglines were shortened from 70 to 50 m.
A comprehensive solution for the problem of high bench mining with the mined material loading onto transport vehicles is proposed by the authors based on the new type of excavating machinery – the so called cranline, which is a combination of the advantages of conventional walking draglines (ability to mine high, up to and over 30 m, benches by downward digging, with a relatively small unit ground pressure) and mining power shovels (target and actually shock-free loading of the excavated material onto transport vehicles). The design of a cranline and its digging and loading equipment has no analog internationally, and it is protected by RF No 2196178 and No 2182971 Patents. Fig 1 and Fig, 2 show the design of a DShP 15.50 cranline and its operation pattern. The main distinctive features of a cranline design are in its additional third single-rope winch and a box-shaped bucket, which is discharged through a hinged back wall (similar to the bottom of a mining power shovel bucket); location of twin units for loaded bucket lifting in the middle part of the lower chord of the boom; application of a single head unit (together with an additional winch) only for the delivery of an empty bucket to the face.
To study the experts’ opinions about prospects for cranline application and demand in the surface mining segment, the IPKON RAS Institute has carried out written opinion polling among design institutes of all mining sectors and some mining companies of Russia. All respondents without exception have given favourable estimates of the prospects of cranline application at already operating surface mines and for the development of new mineral deposits.
However, the lack of funds in the mining sector for the manufacture and purchase of new equipment, as well as the lack of fairly detailed development work do not allow the investigation of the actual demand in such machines, though it may turn out to be significant. Nevertheless, as a result of the analysis of geological and mining conditions of surface operations in Russia, the CIS and some foreign countries a size spectrum of cranlines was identified with 6, 10, 15, 20, 30, 40 and 50 m3 buckets. Judging from the current mining practice and mine requirements the top priority will be given to a cranline with a 15 m3 bucket. Cranline application will allow a two-fold and even greater increase of a working bench height thus providing for a two- or three-fold reduction of the number of benches and length of transport levels, proportional decrease of the scope of work for the construction, maintenance and operational availability of the transport system with the respective decrease of the share of these expenditures in the total mineral production costs. Greater height of benches will allow a steeper slope angle (by 6 …10° and even more) of pit walls and some reduction of the current stripping ratio, and the scope of overburden removal within the boundaries of mining envelope, as well as land demand for outside dumps.
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Discharge onto a BelAZ 7512 dump truck
DPSh 15.50 cranline structural diagram
EKG 15 power shovel axis (4 раза по всему рисунку)
DPSh 15.50 dragline axis (2 раза)
Open-pit development pattern with the application of conventional EKG 15 power shovels and DPSh 15.50 cranlines
As the method of excavation with loading onto transport vehicles prevails in modern surface mining operations, cranlines open new promising opportunities for the increase of working bench height from 12…14 to 30 m that will result in the significant improvement of performance and economics (10-15% reduction of capital expenditures and 20-40% decrease of operation costs), enhancement of output per man and lower energy intensity of mining processes.
At the extended session of the Supreme Mining Council of the Russian Mining Operators Non-Profit Partnership discussing the aspects of the development and perfection of mining machinery and equipment as a determining factor of mining efficiency enhancement the authors made a presentation on the pressing issue of cranline development and operation as a novel competitive excavator with a broad application area in surface mining. The presentation was favourably met by the Council, and its recommendations were included in the resolution of the session. At the same time, great interest was expressed to this machine by Magnitogorsk Iron and Steel Works, the owner of the Prioskolsky GOK mining operations, for which an option is considered of using 15-20 m3 bucket cranlines for the removal of thick soft overburden by high benches and direct loading of the material onto dump trucks. The GIPROruda Planning and Design Institute (St. Petersburg) is expected to investigate at the early design stage an opportunity of cranline application in geological and mining conditions of the Prioskolsky iron-ore mine. Uralmashzavod Corporation agrees to perform the design work for the new machine with utmost possible application of parts and units of the ESh 14.75 dragline baseline model if the necessary funding is provided and a buyer is available for the first cranline prototype. For more precise delivery of the cranline bucket to the point of discharge of mined materials onto dump trucks and significant reduction of operator’s fatigability it is planned to furnish the cranline with a video control system.
This new type of excavating machinery will have a broad application area both at the Russian and foreign natural and technogenic mineral deposits.
Cranlines will have a potential of getting an access to a large market in foreign countries developing new large coal and ore deposits using excavation methods with direct dumping of mined materials to high and particularly high payload dump trucks.
Besides, commercial-scale manufacture of the cranline standard series in Russia will add to the country’s status of the world leading mineral exporter the one of a mining machinery manufacturer exporting its products to foreign markets.