Description of Main Components: Bucket Wheel
In the course of the design meetings we had to decide on the design of the bucket wheel. A single-disk type bucket wheel or an open spooked wheel was up for discussion. After all pros and cons had been weighed up, we decided in favour of the single-disk wheel. Among other things, the main reasons for this decision were higher fatigue strength, better stress distribution in the bucket wheel body with lower stress peaks, a more defined and improved connection to the bucket wheel shaft, less danger of spillage and easier access for inspections. In addition, the calculations showed that about the same weights and deformation of the wheels are to be expected for both designs, so that they were not crucial in making the decisions. In view of its primary deployment in abrasive overburden material, tiles were cemented into the discharge chute as wear protection. The Bükkábrány opencast mine has gathered vary positive operating experience with this kind of wear protection in the past.
The bucket wheel is fitted with sixteen 1.83 cubic metre buckets. A striking feature is the design of the buckets with open backs/rubber strip lining. This design is particularly suitable for the extraction of the material to be worked in the planned mining field, which in places is cohesive to strongly cohesive. The buckets are equipped with eight cutting teeth each that ensure the required high cutting force of at least 1000 Newton per centimetre. To ensure the high capacity of the compact bucket wheel excavator, the bucket wheel drive was designed with a rating of 1100 kilowatts and a variable speed range of between 600 and 1000 rounds per minute. The resulting high static and dynamic loads were a special challenge.
Against this background, we performed extensive calculations and FEM modelling of the gearbox casing including torque bracket during the design phase. The drive train consists of a motor, a safety clutch (multiple-disc slip clutch), a planetary gearing with bevel gear stage and a planetary stage, including load diversion. The wheel of the bucket wheel gearing is connected to the bucket wheel shaft by an overhung coupling flange. The bearings of the bucket wheel shaft are arranged directly next to the bucket wheel on both sides if the bucket wheel boom. The bucket wheel bearings are designed such that either split or un-split bearings can be used.
Description of Main Components: Travel Gears
The dimensioning of the travel components posed a special challenge due to the overall weight of the compact bucket wheel excavator of approx. 1650 tonnes, the two-crawler design and the resulting travel gear load. The substructures of the excavator and belt wagon are supported by two crawler frames with one pendulum bogie each. The travel gear of the excavator consists of two crawlers with two eight-wheel bogies, four four-wheel bogies, eight twin-wheel bogies and 16 track wheels each. We also used a finite element model for all crawler travel gear calculations. The load case combinations on which the model is based cover all static load situations required by DIN 22261 part 2.
The travel gears of the excavator are equipped with two drives each that act on a drive sprocket. The motors have an installed capacity of 2 × 132 kilowatts per travel gear. We use three-phase squirrel care rotors driven by frequency converters. Braking is accomplished electrically by braking resistors. Due to the site-specific requirements regarding an admissible soil pressure of 12.1 Newton per square centimetres maximum, the crawler pads were designed taking operating weight, crawler length and travel gear design into account. Thus, the excavator crawler pads were designed with a width of 4300 millimetres.
Description of Main Components: Hoisting Gear – Hydraulic System
On the excavator, both the bucket wheel boom and the discharge boom are lifted into the desired hoisting position hydraulically by cylinders. Two synchronized cylinders working in parallel are mounted on the bucket wheel boom. Two axial piston pumps, each driven by 132 kilowatt electric motor, are installed on the bucked wheel boom to generate the required hydraulic pressure. The discharge boom is fitted with a separate axial piston pump equipped with 30 kilowatt motor. Should one of the hydraulic systems of the bucket wheel boom break down, the boom can still be operated by the other system at a lower speed. If the smaller system of the discharge boom fails, it can be operated with the aid of the large systems of the bucket wheel boom.
The hydraulic system is supplied by an oil tank with a nominal volume 5000 litres. The belt wagon is also fitted with two hydraulic systems for the adjustment movements of the receiving boom and the discharge boom. To ensure emergency operation in case one of the systems fails, both are equipped with a separate motor/axial piston pump unit. Each system has a motor rating of 45 kilowatts. The oil storage tank on the belt wagon has a volume of 1200 litres. Redundantly designed pressure sensors serve as safety devices to allow the booms to be set down and prevent overloading.
Details about other Assemblies
The main slewing gear of the excavator has a slewing angle of +290 to -110 degrees. The ball bearing slewing rim, which is equipped with a lifting protector, has a diameter of 7200 millimetres. The slewing gear has an installed capacity of 2 × 110 kilowatts and enabled a maximum slewing speed of 45 metres per minute, measured at the middle of the bucket wheel. Independent of this, the discharge boom of the excavator can be slewed at an angle of ±95 degrees, measured at the excavator’s superstructure. Both boom of the belt wagon are mounted on the superstructure of the belt wagon and cannot be slewed separately. The superstructure may be slewed at a ±270 degree angle to the substructure.
The superstructure of the excavator consists of a frame with a firmly attached counterweight boom. The bucket wheel boom is linked directly to the C-frame and discharge boom in connected to it via a revolving platform. The C-frame is designed as a closed case and most parts of it are accessible from the inside for inspection purposes. The main control station of the excavator is connected to the upper part of the C-frame by a jib. Each piece of equipment has two standardized conveyor belts. The belts are metres wide (St 1600) and each belt has a motor rating of 500 kilowatts and speed of 5.0 metres per second.
Three-phase slip ring motors, which are started dependent on time and load, are used as drives. The equipment unit is supplied by a 6 kilovolt trailing cable, which in normal operation is wound on the cable drum of the belt wagon. The maximum cable length is 475 metres at a cross-section of 3 × 240 square millimetres. The excavator has a separate small cable drum with a winding length of 150 metres. The drives for the bucket wheel, the travel gears and the slewing gears are activated by frequency converters. The design of the electrical equipment focused on standardizing it. The excavator and the belt wagon are linked and controlled by a redundant wireless LAN connection.
The PE100-1600/1.5×20 Bucket Wheel Excavator made by Sandvik with an overall weight of 1650 tonnes is designed to handle lm3/h or an annual capacity of 12 million bm3+t. This project was of great significance to Sandvik. It has enabled the company to take another important step into the European open pit mining sector and once again demonstrated its competence as one of the world's leading suppliers of open pit mining equipment.
References Hinterholzer, St.: Weltweit größter Kompakt-Schaufelradbagger von Sandvik, 16. Fachtagung Schüttgutfördertechnik 2011, Magdeburg 2011. Hinterholzer, St.: SandvikK PE100-1600/1.5x2.0 – Largest Compact Bucket Wheel Excavator in the world, 8th International Symposia Maren 2010. Körber, T., Look, A., and Friebe, J.: The world’s largest compact bucket wheel excavator. World of Mining, Surface & Underground 61(2009) No. 1.
* Dr. Stefan Hinterholzer, Manager Sales Central and South Europe of Sandvik Mining Systems, Austria