Zweifel Pomy-Chips AG has used Pilz PSS 4000 automation systems to monitor and control the automation and safety functions on nine upgraded packaging lines for potato crisps, benefiting from simplicity, a drastic reduction in cabling, clear communications, clear responsibilities and, ultimately, an excellent price-performance ratio.
Optimisation of individual machine components can significantly increase the productivity of a whole plant. However, in accordance with the Machinery Directive 2006/42/EC, 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 crisp manufacturer as it integrated a new packaging line: the PSS 4000 automation system ensures efficient, transparent safety management on the plant at Zweifel Pomy-Chips AG.
There is a delicate aroma of fried potatoes in the air: the production plant is spread over two floors, is around 200m long and is working flat out. Zweifel Pomy-Chips AG is based in Spreitenbach near Zürich and uses five tonnes of potatoes per hour to make crisps in a variety of flavours. With almost 400 staff, the company manufactures crisps as well as numerous other snacks. Zweifel has always placed great importance on innovative production processes to ensure consistently high product quality.
Zweifel is in the process of modernising nine packaging lines. The company traditionally has a marked expertise when it comes to building processing equipment. As a result, it prefers to undertake the planning and expansion of production equipment and plant programming itself. Zweifel put the necessary packaging and conveyor systems out to tender; the plant control system was specified.
Compliance with the Machinery Directive 2006/42/EC
The interconnection between the individual plant sections meant that the interfaces and logic connections of the emergency stop functions had to be assessed and transferred into one overall case of compliance. So the Machinery Directive 2006/42/EC comes into play: accordingly, machinery must be constructed in such a way that man and the environment are sufficiently protected from harm. Under bilateral agreements, Switzerland has also undertaken to comply with this directive. 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 standards to be considered, some degree of expertise is required in order to be on the safe side, quite literally.
Gerhard Meier, Team Leader of Technical Services at Zweifel, comments: "It was clear to us that we needed support from a competent partner. As we have enjoyed a longstanding 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 co-operation 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 elements in this concept are the application of standards and directives in accordance with the state of the art, the definition of 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 with the plant control system. Essentially the requirement was this: the device was to be highly network-capable, reliable and simple to program as well as easy to use in day-to-day operation.
Conveyors transport the baked crisps to the new packaging lines. A pneumatically controlled flap opens, allowing the crisps to access the fully automatic packaging machines; the crisps are soon bagged and on their way to market, packed in standard transport cartons. The Pilz PNOZmulti modular configurable control system, 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 become. That is because this system also offers the option to combine and practically merge safety and automation. Gerhard Meier states: "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."
One control system for safety and automation
As the central component in the new packaging line, the PSS 4000 automation system 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 Pilz PSENmag magnetic safety switches and PSENcode coded safety switches. The latter are used to monitor the position of guards in accordance with EN 60947-5-3 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 emergency stop pushbuttons positioned along the packaging line are also monitored using the PSS 4000 automation system. The company attached great importance to the formation of four autonomous safety circuits (safety zones). Ultimately it must be possible to clean one section of the plant without having to bring the whole plant to a standstill.
The PSS 4000 automation system optimises the interactions 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 centralised control system, a modular user program is made available within a centralised project. This enables standardised and therefore simple handling. With its ability to undertake safety and automation tasks, the automation system has already proven itself in numerous applications in a wide range of industry sectors.
Benefits of the PSS 4000
Gerhard Meier concludes: "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." 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 PAS4000 software platform and its graphics editor to link into the existing structure of the PNOZmulti Configurator. Parameter setting therefore remains transparent and simple in case of the need to make changes in the future.
Zweifel started the joint packaging line project in the Autumn of 2012; the plant has been in operation since the end of 2013. Gerhard Meier says: "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." Given the success of this project, the prospects are excellent for further projects that will no doubt arise at Zweifel.