Open-pit dump truck
OPEN-PIT DUMP TRUCK (EN: open-pit dump truck, haulage truck; DE: Tagebaukipper, Tagebauselbstkipper; FR: camion- benne de carriere; ES: camion basculante de mina; RU: автосамосвал карьерный) is used for the transportation of the overburden rock and minerals at the open pit mining works.
The BelAZ dump truck:
- the steerable front wheel with the drum brake;
- the hydromechanical assembly of the independent suspension of the front wheels;
- the assembly of the diesel engine with the electrical generator;
- the fuel tank;
- the longitudinal lever of the independent pneumo-hydraulical suspension of the rear wheels;
- the rear driving axle with the traction motors which are integrated into the hubs;
- the dump body.
The production of the open-pit dump trucks (the MAZ-525 of 25 tonnes load carrying capacity) in the USSR has started for the first time in 1950-51 at the Minsk Automobile Plant. Since 1961-65, the BelAZ open-pit dump trucks (Fig. 1) with the large load carrying capacity are created at the Belarusian Automobile Plant (table). The main elements of the design of the open-pit dump trucks are: the engine, the chassis, and the dump body. There are mainly used on the open-pit dump trucks the four stroke 6-, 8-, and 12-cylinder diesel engines with the power from 184 to 1690 kilowatt and the high frequency of the rotation. The chassis of the open-pit dump trucks comprises the transmission (hydraulic or electromechanical), the running gear, and the mechanism of the control. The hydromechanical transmission is used in the open-pit dump trucks with the load carrying capacity of 20-70 tonnes. The main assembly of the transmission is the torque converter, with the help of which the traction force at the driving wheels is adjusted automatically because of the step-less conversion of the torque. There is also the hydrodynamic retarder in the hydromechanical transmission of the BelAZ open-pit dump trucks, which allows to maintain the constant speed of the open-pit dump trucks on the downhill slopes, thus enhancing the safety of the traffic in the conditions of the complex profile of the open pit roads. The electromechanical transmission is used in the open-pit dump trucks with the load carrying capacity of 75 tonnes or more. It comprises the generator, the shaft of which gets the rotation from the diesel engine, the traction motors, which drive the wheels, and the system of the regulation. The usage of such transmission allows to implement the individual drive of the wheels, and to use several axles as the driving ones. The motor-wheel is the element of the transmission, in the hub of which the planetary gear assembly is mounted.
The running gear comprises the frame, suspension, wheels and tires. The frames of the open-pit dump trucks are welded with the increased strength. The most widely used suspension is the pneumo-hydraulic, with nitrogen serving as the elastic working body of its cylinders, and the spindle oil serving as the hydraulic fluid. There are two wheels installed at the front axle of the open-pit dump trucks, and the two paired wheels at the every side of the rear axle. The usage of the tubeless tires is promising good results for the open-pit dump trucks with the large load carrying capacity.
|The cost of the transportation, kopeks per tonne per kilometre|
|Power, horse powers|
|The cost of the transportation, kopeks|
|The load carrying capacity, tonnes|
The dump body of the open-pit dump trucks is made of the sheet metal, which is welded together, mainly V-shaped. The dump body is unloaded most often by the tilting backward, the lifting of the platform is performed by the hydraulic mechanism with the remote control. The dump body is equipped with the buttresses of the box cross section, which are heated by the exhaust gases in order to prevent the freezing and sticking of the rock mass. They distinguish the open-pit dump trucks depending on the type of the carried load, the design, and the method of the supply of the power: the coal carrying dump trucks, the tractors for the semi-trailers and trailers, the dump trolley trucks. The coal carrying dump trucks are distinguished by the increased volume of the dump body. They are using the tractors with the semi-trailers (the unloading is backward, through the bottom, and by the tilting of the dump body to the side) for the moving of the significant volumes of the minerals. If there is the possibility to implement the electrical power supply in the open pit from the contact wire network, then they use the dump trolley trucks.
The main parameters of the open-pit dump trucks are: the load carrying capacity (the main indicator), the power of the engine, the wheel formula, and the volume of the dump body. The optimal level of the power of the open-pit dump trucks of the various load carrying capacities is determined on the basis of the technical-economic analysis (Fig. 2).
The specific value of the power (the power, which is divided by the total mass of the dump truck with the load) is 5.1-5.9 kilowatt per tonne for the automobiles with the carrying capacity of 27-110 tonnes. The most widely used wheel formula of the open-pit dump trucks is 4x2 (the first number is the total number of the wheels, the second number is the number of the driving wheels), less often 4x4; the wheel formulae for the automobile trains with the semi-trailers are 6x2 and 6x4. The volume of the dump body (with the defined load) depends on the density of the transported material. For the open-pit dump trucks with the rear unloading, the ratio of the load carrying capacity to the geometric volume of the dump body is 1.7-2 (or 1.4-1.6 while including the volume of the (heap) so-called cap); for the coal carrying dump trucks this indicator is 1.15-1.35 (the value of this ratio increases with the increase of the load carrying capacity).
The most presentable foreign companies, which are producing the open-pit dump trucks with the extra large load carrying capacity, are the "Unit Rig" and "Wabco" (USA). The range of the load carrying capacities is from 77 to 200 tonnes. The open-pit dump trucks of the "Unit Rig" company with the load carrying capacity of 180 tonnes have the power of 1810 kilowatt and the wheel formula 4x2. The open-pit dump truck with the greatest load carrying capacity of 317 tonnes has been created by the "Terex" company, with the 2200 kilowatt power of the engine, and the 6x4 wheel formula (1981). The directions of the improvement of the open-pit dump trucks are the increase of the load carrying capacity, the improvement of the maneuverability and the speed qualities, the creation of the specialized automobile transport for the transportation of the various rocks and for the work according to the specific technological plans.
|Characteristics||The type of the dump truck|
|Load carrying capacity, tonnes||27||40||75||110||180|
|The mass in the ready to work condition, tonnes||21||28||65||85||120|
|The radius of the turn according to the track of the external front wheel, metres||8.5||10||9.0||12||15|
|The greatest allowed speed, kilometres per hour||55||55||60||50-52||52.5|
|The power of the engine, kilowatt||265||368||700||956||1540-1680|
|The volume of the dump body, cubic metres||15||21||41||45||90|
|The type of the transmission||Hydromechanical||Electromechanical|
|A a||B b||C c||D d||E e||F f|
|G g||H h||I i||J j||K k||L l|
|M m||N n||O o||P p||Q q||R r|
|S s||T t||U u||V v||W w||X x|
|Y y||Z z|