On average, 195 t limestone is transported from the loading point to the tipping point. The material is transported by three new Cat 775G off-road trucks in single-shift operation at Wiesenhofen Quarry. The Max Bögl group of companies and its Raw Materials and Construction Materials Unit put the construction machinery from Zeppelin and its Corporate Customer Division into operation at the site in Beilngries in Upper Bavaria. Since the early 1980s, the quarry has been operated by Max Bögl. By the end of 2018, the three new off-road dump trucks have to clear around 800 000 t overburden. In addition, the transport equipment has to move the volume of pre-screened material that is unsuitable for further production of, for example, high-performance concretes as spoil.
In the limestone quarry, high-grade concrete and asphalt aggregates as well as road construction materials are produced. Especially the chippings used in precast concrete have to meet very high quality requirements. For this reason, the ballast plant was modernized extensively in the years 2013 to 2016 and an innovative integrated concept implemented to achieve the high quality requirements for the processed limestone grades and comprehensively utilize the raw material resources.
For loading the new 124 t dumper truck, a Cat 988K wheel loader is used. Blasted material from the partly karstified areas of the deposit material is loaded on the upper working level of the quarry. The overburden has a thickness of around 10 to 20 m. For removal of the blasted material, the capacity and availability of the off-road trucks are crucially important. Four loading cycles of the wheel loader are needed to fill the just under 42 m³ body volume of the Cat 775G and reach its 65 t payload. With regard to the transport volume, material and the geological conditions at the deposit, the suitable transport equipment was selected in the run-up based on an extensive operations analysis.
For precise control of the loading process and an efficient utilization of the payload, the VIMS onboard weighing system is used. VIMS stands for Vital Information Management System and includes the hard- and software behind the machine and payload information, which is provided via the display in the 775 G dump truck. In combination with the production management system, for every loading and transport cycle, optimum unloading is ensured.
To use the features like these in the new off-road trucks, the 13 drivers in the total of 21 employees working at the site underwent training by Zeppelin, the construction machinery supplier. The machine operatives found out that the indicator lamps show when the last loading cycle has been completed and the fully loaded trucks can drive off. One vehicle generally travels around 1.1 km and negotiates slopes up to 8 % on average before it can tip out its load. With the truck‘s production management system, up to 2 400 payload cycles can be stored. The company management at Wiesenhofen Quarry receives logs with date and time on weights, transport cycle times and transport distances. Moreover, the truck tyres can be monitored.
Payload data and tyre condition are, however, not the only values that can be used to keep an eye on the efficiency of the fleet of construction machines. Other parameters can be called up continuously to record performance. These include GPS data, fuel consumption, kilometres driven, load and idle times, engine speed and especially the temperature of the Cat Acert diesel engine C27 with a gross power of 615 kW or 825 hp. Fuelling and logging of the hours and reading of the engine data via CAN-Bus are realized with the proprietary telematic system developed within the Max Bögl group for fleet management.
“In future we are relying on intelligent, digital networking and direct communication between people, machines, plant, logistics and product,“ explains Katharina Himsel, Head of Quality Management and Quality Assurance in the group‘s Raw and Construction Materials Department. The construction machines have already reached the digital age, Innumerable sensors on the three Cat off-road trucks register even the slightest deviation. In concrete terms, it is all about utilizing the construction machine data acquired and evaluated with the SAP maintenance software. These data are used by the employees at Max Bögl to aid their decision making in order to determine the perfect time for maintenance and to document operating states.
The limestone is processed in several stages. The blasted material is gently pre-comminuted in a track-mounted mobile double-roller crusher. With a mobile belt link at the bottom of the quarry and stationary belt conveyors, the material is fed to the outside stockpile. Further cleaning of the material is performed on a roller screen. The now concentrated carbonate rock is processed in two newly installed HSI 400 impact mills to finished products. On two parallel screens, the individual fractions are sized into the finished grades.
The raw material operations in the Max Bögl group are currently in the process of change. The focus is on efficient and sustainable raw materials extraction on the one hand and increasing the utilization rate on the other. The modern plant equipment is to contribute to this in order to assure a consistently high quality level of the construction materials produced.