Successful retrofit with MVK Metal
Electrical designers at Alfred Ritter GmbH use the relocation of a plant to thoroughly refurbish the electrical system
Chocolates from Ritter Sport are enjoyed all over the world. Their square shape is an unmistakable trademark. Every child knows: Quality. Chocolate. Squared. is Ritter Sport’s slogan. One popular best-seller of the company is the rum bar made with real Jamaican rum. Recently, the system that produces crispy bars was subjected to a retrofit. Field bus modules from Murrelektronik are now used for the communication.
Alfred Ritter GmbH & Co. KG has its headquarters in Waldenbuch, a town located south of Stuttgart on the northern edge of the Schönbuch national park. The company uses sustainable electricity and energy production and has constructed a new building with a modern co-generation plant. This required the relocation of the existing plant for production of the popular Ritter Sport Rum chocolate bars.
The electrical construction team led by Peter Schetter saw this as an opportunity. “We decided to use this opportunity to thoroughly refurbish the mechanics and control systems of the plant,” says the construction manager. The focus was on safety. For the Ritter Sport electrical designers, it was clear “that the solution should not only comply with the standards in every respect, but also should achieve a maximum cost-benefit effect.”
The chocolate bar production plant extends over three floors. The processes are precisely coordinated and everything is intermeshed. First, the components are mixed to form a basic mass. After this, pieces of wafers and California raisins, which have been previously immersed in genuine Jamaican rum for more than 20 hours, are added. In the next step, the bars are shaped, covered with delicious whole milk chocolate and – right at the end of the process – they are packed in the distinctive blue wrappers.
While the many sensors and actuators of the individual plant components were connected with single conductor wiring at their previous installation location, the extensive installation was now implemented with MVK series field bus modules from Murrelektronik. These consist of a robust die-cast zinc housing with a coated surface, and the full encapsulation makes them ideally suited for use in harsh industrial environments.
“With a plant which extends over three floors, the field bus solution saves a considerable amount of wiring,” says Peter Schetter. The field bus modules are installed in the immediate vicinity of the processes and from there, the sensors and actuators are connected with very short connection cables. If a cable wears out, it can be replaced in a very short time. In the MVK Metal field bus module, all channels are individually monitored for errors such as overload, short circuits or cable breaks. If an error occurs, this is indicated by an LED at the relevant port. In addition, a message is sent to the control unit. “We utilize these diagnostic facilities to the fullest extent,” says Peter Schetter. Errors are quickly detected and can be quickly remedied, which prevents downtimes. The head of the electrical design department explains why a high availability of the plant is economically important: “We produce just-in-time without large inventories, so as to be as fresh as possible in the shops.” Moreover, in the sensitive food industry, even a small problem can add up to a time-consuming failure if the plant has to be thoroughly cleaned before restarting operation.
M12 cables from Murrelektronik that were pre-assembled on one side are used in many places throughout the installation. At many of the ports, the Ritter Sport electrical designers use T-adapters in order to be able to use both channels for transferring signals, so that more sensors and actuators can be connected to each module. The cables are tightened with a torque wrench from Murrelektronik: “With this, we can easily access the hexagonal nuts, even in confined situations,” says Peter Schetter. The correct torque is important because machines are affected by strong vibrations, and connections may come loose if not tightened accurately.
Industrial safety is also highly relevant in the Ritter Sport Rum bars production plant. Because of this, there are protective devices in all areas of the plant to ensure the safety of humans and machines. For example, the agitator cannot start unless the covers are closed. For the first time, the Ritter electrical designers have installed distributed safety-relevant sensors and actuators. To accomplish this, they have integrated the MVK Metal Safety field bus module from Murrelektronik into the plant, which enables safety-relevant data to be transferred directly via PROFIsafe, a safety-specific extension of PROFINET. This eliminated the need for passive wiring in the control cabinet and still satisfied the very highest safety standards (SIL3 and PLe).
Author: Alexander Hornauer