Optimization of individual machine components can significantly increase the productivity of a whole plant. However, in accordance with machinery safety regulations and standards, in many cases a risk analysis is involved, along with the production of a qualified safety concept. Pilz, the complete safe automation supplier, supported a well-known Swiss potato chip manufacturer as it integrated a new packaging line. The automation system PSS 4000 ensures efficient, transparent safety management at Zweifel Pomy-Chips AG.
There's a delicate aroma of fried potatoes in the air. The production plant is spread over two floors, is around 660 ft. long and is working flat-out. Zweifel Pomy-Chips AG is based in Spreitenbach near Zürich and uses 5 tons of potatoes an hour to make chips in a variety of flavors. With almost 400 employees, the company manufactures chips as well as numerous other snacks and nibbles. Zweifel has always placed the greatest importance on innovative production processes, which guarantees a consistently high quality product.
Change entails a risk assessment
Zweifel is in the process of modernizing nine packaging lines. The company traditionally has a marked expertise when it comes to building work equipment. As a result it prefers to undertake the planning and expansion of production equipment and plant programming itself.
The interconnection between the individual plant sections meant that the interfaces and logic connections of the E-STOP functions had to be assessed and transferred into one overall case of compliance. This is where the machinery safety regulations and standards comes into play. Machinery must be constructed in such a way that man and the environment are sufficiently protected from harm. Manufacturers of machinery, and those that place it on the market, must give binding confirmation that their plant meets the minimum requirements, in the form of a declaration of conformity. In view of the large number of safety regulations and standards to be considered, some degree of expertise is required in order to be on the safe side, literally.
Support
"It was clear to us that we needed support from a competent partner. As we have enjoyed a long-standing partnership with Pilz, we were aware of their expertise in matters regarding risk assessment and development of reliable safety concepts, right through to CE marking," says Gerhard Meier, Team Leader of Technical Services at Zweifel. Pilz worked in close cooperation with the company to produce a safety-related control concept, which involved the development of mechanical, electrical and other technical engineering solutions for machinery safety. Essential components in this concept are the application of regulations and standards in accordance with safety integrity levels (SIL) or performance levels (PL) and the consideration of machine availability and productivity, including safety aspects. Zweifel was looking for a high-performance safety control system to link and monitor the exchange of safety-related signals, separately and in parallel to the plant control system. Essentially the requirement was that the device had to be highly network-capable, reliable, simple to program and easy to use in day-to-day operation.
Automation system PSS 4000
Conveyor grooves transport the fried chips to the new packaging lines. A pneumatically controlled flap opens, allowing the chips to access the fully automatic packaging machines. The chips are soon packaged in the bag and on their way to market, packed in standard transport cartons. The Pilz configurable control system PNOZmulti, which had been used previously, had been responsible for the plant's safety management. However, the bigger the plant and the more complex the requirements, the more efficient and economical complete, modular systems, such as the PSS 4000, are needed. That's because this system also offers the option to merge safety and automation. "We had been following the development and launch of the automation system PSS 4000 with interest for some time. Following an internal cost/benefit analysis of both systems we came to the conclusion that now was the right time to use the PSS 4000," says Gerhard Meier.
Overall safety management
As the central component in the new packaging line, the automation system PSS 4000 for safety and automation monitors all the safety-related functions. The packaging line includes safety gates as well as an intelligent access concept. The gates are fitted with magnetic safety switches PSENmag and the coded safety switches PSENcode from Pilz. The latter are used to monitor the position of guards in accordance with safety regulations and standards and also for simple position monitoring. The pneumatic cylinders are also monitored safely. The flaps must be safely locked during cleaning; otherwise there is an increased risk of injury. The E-STOP pushbuttons positioned along the packaging line are also monitored using the automation system. The company required four autonomous safety circuits. Ultimately it must be possible to clean one section of the plant without having to bring the whole plant to a standstill.
The automation system PSS 4000 generally stands for optimum interaction between hardware and software components, network devices and the real-time Ethernet. As it is possible to distribute and transfer control functions consistently to the periphery, this system enables a wide range of projects to be implemented more easily and with greater flexibility than with conventional solutions. Rather than having a centralized control system, a modular user program is made available within a centralized project. This enables standardized, as well as simple, handling. With its ability to undertake safety and automation tasks, the automation system has already proven itself in numerous applications in the widest range of industry sectors.
Simple, transparent parameter setting
"When selecting the automation system PSS 4000, the deciding factors for us were the simplicity, the drastically reduced cabling work, clear communication, clear responsibilities and, ultimately, the excellent price-performance ratio," says Gerhard Meier. Communication between the plant control system and the existing Modbus TCP bus system is running smoothly. Another key factor in the decision to choose the automation system was the ability of the software platform PAS4000 and its graphics Editor to link into the existing structure of the PNOZmulti Configurator. So parameter setting remains transparent and simple in the future.
"As usual, co-operation with Pilz was conducted in a spirit of partnership. Pilz not only supplied us with outstanding products, but also provided competent support in word and deed before, during and after commissioning," says Gerhard Meier, summing up.
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