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 recently assisted Zweifel Pomy-Chips as this well known Swiss potato chip manufacturer went through a modernization process. The PSS 4000 automation system implemented at the snack manufacturer’s Spreitenbach facility ensures efficient and transparent safety management.
The production plant is spread over two floors and uses five 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.
The Zweifel project involved modernizing nine packaging lines. 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 machinery safety regulations and standards come into play. Machinery must be constructed in such a way that man and the environment are sufficiently protected from harm. Manufacturers of machinery must give, in the form of a declaration of conformity, binding confirmation that their plant meets the minimum requirements. 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.
“It was clear to us that we needed support from a competent partner,” says Gerhard Meier, Team Leader of Technical Services at Zweifel. “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.”
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.
Transport to packaging
Conveyors transport the fried chips to the new packaging lines. A pneumatically controlled flap opens, allowing the chips to reach the fully automated 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 had been responsible for the plant’s safety management. However, as the modernization project made the plant bigger and the requirements more complex, a more efficient, economical, and modular system was needed. Thus the implementation of the PSS 4000, a system that also offers the option tomerge safety and automation. “We had been following the development and launch of the automation system PSS 4000 with interest for some time,” says Meier. “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.”
As the central component in the new packaging operations, 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.
“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 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 Meier.—Pat Reynolds
