Automation of a gravel plant

Challenge

In the past, the operation of the crushing plant was based on conventional contactor technology. A PLC was never used. In the course of a comprehensive upgrade of the facility, the plant operator decided to implement a state-of-the-art automation and drive concept that would also increase productivity. It hired Baden-Baden based Weingärtner GmbH (Weingärtner) for the project, which specialises in electrical installations, panel building and automation and drive technology.

“We were faced with the challenge of creating a cost-effective solution that would enable the plant operator to get a detailed overview of the installation, and to adjust operations based on actual utilisation,” explains Philipp Fels, the Weingärtner manager responsible for this project. “In addition, there were significant time constraints, since we only had about four weeks during the annual winter repairs to completely refurbish the electrical system.” This meant that the control room and the control panels had to be pre-installed and delivered inside a container. As a solution partner in Eaton’s EMEA-wide network of application specialists, Weingärtner was familiar with the capabilities and strengths of the intelligent SmartWire-DT connection and communication system. Given the conditions on the ground, the Baden-Baden-based company decided to tackle the project using Eaton technology. 

Solution

The Weingärtner-designed control centre for the system is based on the XP500 touch panel, a user-friendly HMI with capacitive multi-touch technology that is not only thin and ventilation-free, but also comes with a small footprint. The 21.5 inch version of the XP500 handles the visualisation of the system’s higher-level processes. A network of XC202 PLCs, which Weingärtner programmed using Codesys 3.5, is used to manage the processes. According to Fels, implementing the complete visualisation of the facility was extremely fast and easy, thanks to the latest version of the Eaton software.

Weingärtner devoted special attention to the drive technology in the crushing operation, which has a significant impact on the overall efficiency and productivity of the plant. Eaton’s Power XL DE1 variable frequency drives control the conveyor and metering belt motors. They are easy to operate and are as reliable as a motor starter, whilst at the same time offering variable speed control. This makes them ideal for applications that don’t need extensive functionalities, but do require variable speed. For more demanding applications, such as screening machines, water pumps, sand screws and screw conveyors, the DA1 variable frequency drives are used, which offer both a high degree of modularity and advanced motor control capabilities.

In addition, the facility was also equipped with around 70 PKE motor-protective circuit breakers with electronic overload protection, which enable safe and reliable DOL starting. The intelligent SmartWire-DT connection system facilitates fast and effective wiring of all important components, without any need for control wiring, remote I/O levels or complicated addressing. Fels estimates that “compared to conventional control panel wiring, we were able to achieve time savings of around 30 %.” Moreover, if used together with the PKE motor-starter combinations, SmartWire-DT offers another decisive advantage: All switching states and status reports, which previously required the time-consuming installation of additional devices, can be transmitted directly to the controller. This includes information on the switching position of the contactor and the motor-protective circuit breaker, the selected rated current and degree of inertia, as well as the motor current and the thermal motor load. In addition, diagnostic functions for overcurrents, short circuits, overloads and phase failure are also available.

Results

This enables the crushing plant to monitor, evaluate and analyse the loads on the motors in real time, without any additional equipment. If a motor-protective circuit breaker trips, for example, the staff will immediately be notified that it has tripped due to an overload. Instead of taking the risk of turning the system back on, this enables operators to check whether any material is jammed on the conveyor belt. The monitoring function also enables predictive maintenance, since gradual current increases over time may indicate wear on the protective switch. It may thus be possible to prevent the breaker from tripping, thereby also preventing the failure of the affected drive.

“Every drive at the Iffezheim plant is now monitored by SmartWire-DT, which gives us valuable information about real-time utilisation based on the thermal motor model,” says Fels. For example, the new system enables the plant to start with smaller production quantities as it is warming up, and to switch to full capacity only once it has reached its normal operating temperature. “I am not aware of any other technology that provides this level of transparency in such an efficient and compact manner," emphasises Fels.

The feedstock in crushing plants consists of naturally fluctuating raw material with a composition that is constantly changing. Therefore, the exact load on the system will also be in constant flux. For example, if coarser material is fed into the first crusher, the end product will also be significantly coarser. The machines downstream of the crusher, which classify and discharge the coarse components, will thus be subject to greater loads, while the machines that handle the finer particles will be less affected. However, should the feedstock change, this will also change the load on the downstream machines. This system therefore needs to be able to adapt to the load in real time. By continuously analysing the load on each machine, the control system identifies if a bottleneck is present and then adjusts the output of the entire facility accordingly. Yet within minutes, the bottleneck may shift to another component of the facility, in which case the system will readjust the output in line with the optimum load capacity of that component. Despite the load fluctuations, the new control system thus ensures that the crushing plant is always running at its optimum operating point.

Thanks to the enhanced functionality of the new system, including load-adaptive control, the intuitive operating concept and integrated diagnostics and monitoring, the crushing plant was able to reduce unplanned downtime, which has also resulted in a significant increase in productivity.