Food line reaches crunch time

Optimisation of individual machine components can significantly increase plant productivity, but alongside this, a risk analysis is often required, along with the production of a qualified safety concept.

Automation supplier Pilz was on hand to support Swiss crisp manufacturer Zweifel Pomy-Chips when it integrated a new packaging line.

It was clear to us that we needed support from a competent partner

Zweifel’s Gerhard Meier

The Swiss production plant is spread over two floors, is around 200m long and is operating flat out.

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 then bagged and on their way to market, packed in standard transport cartons.

Because the company had interconnected each of the individual plant sections, the interfaces and logic connections of the emergency stop functions had to be assessed and transferred into one overall case of compliance, to comply with the Machinery Directive 2006/42/EC.

Accordingly, machinery must be constructed in such a way that man and the environment are protected from harm.

“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 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.”

The company worked in close co-operation with Zweifel to produce a safety-related control concept, which involved the development of mechanical, electrical and other technical engineering solutions for machinery safety.

Essential elements of 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 highperformance safety control system to link and monitor the exchange of safety-related signals separately and in parallel with the plant control system.

The device had to be highly networkcapable, reliable and simple to program as well as easy to use in day-to-day operation.

The Pilz PNOZmulti modular configurable control system, used previously, had been responsible for the plant’s safety management.

However, for bigger plants with complex requirements, modular systems such as the Pilz’s PSS 4000 can offer better economies by allowing companies to combine and 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,” Meier says.

Simple control

The PSS 4000 monitors all the safetyrelated 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.

For its four autonomous safety circuits (safety zones), it must also 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, a wide range of projects can 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 standardises and simplifies handling.

A key factor in the decision was the ability of the PAS4000 software platform and its graphics editor to link into the existing structure of the PNOZmulti Configurator, the company says.