WORLD PROSPECTS
Simulation enhances mining engineering
Thanks to digitalisation in engineering, ore grinding mills can be made more powerful and belt conveyor systems can be optimised. System components and operations can be simulated, faults can be diagnosed before commissioning, and technical limits can be explored on a virtual system, the so-called digital twin of the real system.“ The simulation results benefit engineering and thus also developers and operators of systems,” says Torsten Hellmuth, who is responsible at Siemens for belt conveyor systems used in open-pit mining.“ As a result, we can shorten development times, reduce costs and the fault rate during commissioning while increasing safety for the company and the operator.”
The technical requirements involved in developing systems and system components for the mining industry are constantly growing. When developing their systems, mechanical engineers must increasingly take completely dissimilar topics into account such as machine and component automation, the provision of production data, and network communication issues. At the same time, they are expected to combine increasingly complex mechatronic solutions with various automation tasks. According to Helmut Liepold, a sales representative for Gearless Mill Drives at Siemens, this new engineering world involves more than designing systems on CAD screens; work is now done using digital twins, which are digital models of systems or components that either already exist or still need to be built. Liepold stated:“ Product lifecycles for the machines are growing ever shorter worldwide, and the machines must be more and more variable and flexible in manufacturing processes. The pressure on engineers to get a system ready for market within a short period is rising.” Starting with the earliest production stages, engineers must likewise deliver a level of quality and efficiency so high that readjustments must kept to a minimum.“ The time for commissioning in particular is extremely expensive,” Liepold emphasises.“ We barely have time anymore for testing the individual components or mechanics at the construction site. The machine has to be delivered, assembled, and commissioned, and then it must immediately operate in the user’ s production process.”
Siemens offers its Digital Enterprise Suite, a comprehensive portfolio of software- and hardware-based systems that provide a solid foundation for integrated engineering. It is based on the creation of a digital representation – the digital twin – of a system or machine. Mechanical engineers can thus
Structure and stress analysis of a GMD installation to comply with the stringent Chilean seismic standards
design, simulate, test, and optimise their products in a purely virtual world, even before any resources are used in the real world. Siemens’ comprehensive approach offers mechanical engineers mechanical, thermal, and electronic engineering as well as the integration of automation solutions, all on a single platform.“ This allows testing of system behaviour in operation or in various fault scenarios for the most part before prototypes are built,” explains Hellmuth. Above all, the software allows him to work with the time factor in system simulation.“ I can run through a simulation considerably faster in the software and test cycle times and output in a much shorter time.”
In contrast to performance simulation of belt conveyor systems, Siemens uses system simulation with the hardware-in-the-loop( HiL) method, especially for Gearless Mill Drives and Mine Winder applications. The HiL replaces the drive and the grinding mill or mine cage and provides real-time feedback to the higher-level controller as in the real drive. The functionality of a project and new developments are tested effectively in this way.
A third simulation of Gearless Mill Drives that is especially indispensable today is the structure and stress analysis using the finite element( FE) method. It serves as proof that foundations, mills, and ring motors meet the requirements, such as those of the Chilean seismic standard( NCH 2369), and that the system will withstand even extreme earthquakes.
Today, ore-grinding mills of 42 ft and up to 35 MW are part of a normal discussion. Systems of this size cannot be tested in a laboratory, yet nevertheless must function faultlessly from the start. FE simulation and stress analysis with verified motor models as well as function tests with HiL are the only way to protect customers’ investments.
For system builders, simulation makes it possible to analyse the operational performance of a complex system and particular components under a wide range of operating conditions with no need to conduct expensive field tests.“ I ' m
particularly interested in exploring critical or worst-case situations and their consequences without damaging a system.” Using the digital twin, he analyses the behaviour, interaction, and reciprocal influence of various components, such as in the event of an emergency stop, three-phase short circuit, brake failure, or belt tear.
Hellmuth uses simulation tools not only to develop new systems but to study the behaviour and interaction of the belt conveyor mechanics and drive solution in existing systems. By means of simulation, he investigates changes and consequences in system performance. In the course of modernisation, for example, if capacity is increased, the topology is changed, or components are replaced.
Sufficient calculation methods are also available today for dimensioning belt conveyor systems. These normally determine the maximum load for components, the motor rating, the belt tension, or the bearing load. In contrast, simulation allows engineers to test the dynamic behaviour of the complex system as well as to explore and improve how the individual components work together.“ This aspect is why we want to perform simulations,” says Hellmuth.“ Knowledge about and experience with the behaviour of a belt conveyor allow us to select the suitable drive solution and controller in order to optimise the operational and productivity ratios. Simulation of belt conveyors for greenfield projects thus helps with the decision as to whether a drive solution with a hydraulic coupling is sufficient or a drive solution with a frequency converter is more suitable. Simulation also allows us to improve system operation and minimise idle time.”
The results are used internally for planning and commissioning the drive solutions or provided to potential operators or system builders.“ For us as a provider of digital solutions for belt conveyor systems, the drive unit and the corresponding controller or control system always have priority,” Hellmuth emphasises.“ Our expertise allows us to map the mechanical part of the belt conveyor, which is either delivered by third parties or already available, in the model and to analyse the interaction with the drive solution.”
The results from simulating how the mechanical part and electrical part of a drive unit work together are then incorporated into the requirements that serve as the basis for further development of motors and converters and possibly control concepts. In addition, the linking of digital models of a belt conveyor’ s mechanical and electrical components enables virtual commissioning of the belt conveyor. www. siemens. com
6 International Mining | MARCH 2017