Decentralised pneumatics system offers production cost savings

07 March 2012

Ice-cream manufacturer, GB Glace, part of the Unilever Group, has reduced costs and boosted process quality thanks to the implementation of a decentralised pneumatics concept. The GB Glace site in Flen, Sweden is one of the company’s ten European ice-cream production sites. It produces around 45 million litres of ice cream every year.

Production at the site is subject to strict hygiene regulations, yet production cost reduction is also an important factor today. The use of Rexroth pneumatic valves, from the CL03 Clean Line series with integrated Profibus, have helepd the company to achieve significant savings in materials, energy, installation and labour costs as well as improving its process reliability.

Innovation over replacement
The small technical details are as important in ice-cream production as the company’s secrets involving quantities, ingredients, and mixture ratios. An example of this is the conversion from traditional pneumatics to modern valve technology with bus connections. “Since its installation in 1989, our previous technology served us well. However, we were forced to realise that maintenance-related spare parts were no longer available,” said Karleric Idegren, process project engineer at GB Glace in Flen. “Our initial idea was to search for adequate replacements for the existing components, but this ultimately led to use looking at a new pneumatic actuation concept.”

Rexroth valve terminal systems from the CL03 series are at the heart of the new system. The valves feature a consistent hygiene concept certified by the European Hygienic Engineering and Design Group, in addition to the high protection class IP69K and a bus connection directly integrated in the valve terminal system. “If we had merely replaced the components in the existing system, the investment for their installation alone would have cost five times more than our current, more modern and technologically advanced solution,” continues Idegren.

The valve terminal system presents convincing design details. The CL03 is easy to clean and maintain. It is made up of individual base plates with internal wiring and can be populated with up to 16 valves. The individual valves in turn can be set for two different pressure levels. This is necessary to drive the cylinders in a unit at differing pressures, corresponding to the power needed. The 16 valves in the system can therefore drive 16 different cylinders and offer the ideal pressure level for each unit served.

GB Glace replaced the previously installed pilot valves with new 2x3/2-way solenoid valves, which now provide more functions to actuate the 51 process valves on the mixing tanks. GB Glace’s overall system uses approximately 400 valve functions. With a total of 38 functions, two ramps actuate the valves at the cream tanks. The valve terminal system offers easy care, quick cleaning, and simple maintenance, thus reliably preventing microbial contamination.

Cutting costs to boost efficiency
Due to the decentralised configuration of the pneumatic system (all valves are close to the using units, such as cylinders, skid drives and grippers) both the valve cabinets and any additional PROFIBUS cabinets are now redundant.

“We have now also started the conversion of the pneumatic system on the mix storage tanks, where approximately 330 functions will be available for process valves on completion. In this area of the system alone, the new solution with integrated Profibus eliminates 14 control cabinets, including their wiring. This facilitates our work enormously. We have now eliminated 400m of air hoses and three ramps, so that 25% of cost reductions can be attributed to components that are no longer necessary, including their installation.”

These figures provide evidence of the savings potential of an intelligent solution. “This does not factor in the process improvements we have achieved,” said Idegren, pointing out the further advantage of greater system efficiency. Fewer cables mean less dead volume and pressure loss, and thus lower air consumption and far fewer expenditures for preventing the potential infiltration of bacteria.

“The new system demonstrates a clear functional improvement – it is simpler and more economical. The mixing tank system now operates more efficiently and reliably than it did before. In addition, the lower investment also shortens the amortization period.”

These advantages are based on a series of details including inductive sensors in the control unit which monitor the valves. Whereas the older pilot valves needed ten seconds from end stop to end stop, today’s solenoid valves accomplish this in just three seconds. The sensors verify whether the valves have closed in the allotted time and a notification alerts employees if that window is exceeded. Idegren says of the new features: “It increases safety, reliability and profitability since a defective component in the final manufacturing phase, for example, can spoil up to 5,000 litres of finished ice cream.”

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