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Innovative packaging production calls for oil-free compressed air – in an efficient and reliable manner

Author: Othmar Hauser, Gardner Denver Schweiz AG, Division CompAir, CH-Winterthur

At its site in Weinfelden, Switzerland, Model AG runs an integrated paper and packaging production facility - where time and time again it is awarded for its innovative display and packaging solutions. The company is gradually converting its compressed air generation to oil-free, speed-regulated screw compressors and, in doing so, places a great deal of importance on the efficiency and reliability of supply.

From recycled paper, to high-quality corrugated cardboard, through to ready printed and assembled packaging with an innovative, promotional design: at its headquarters in Weinfelden, Switzerland, the Model Group covers the entire process chain of packaging production. This calls for an extensive range of machines and systems.

From recycled paper, to high-quality corrugated cardboard, through to ready printed and assembled packaging with an innovative, promotional design: at its headquarters in Weinfelden, Switzerland, the Model Group covers the entire process chain of packaging production. This calls for an extensive range of machines and systems.

Excellent ideas for innovative packaging and displays

On an annual basis, two paper machines each with a 250 cm working width produce 177,000 tonnes of paper in grammages from 100 to 230g/m 2 .

At one of the most productive corrugated cardboard plants in the world, with a capacity of 180 million m 2 /a, the paper is processed into corrugated cardboard. In the third process stage - the packaging production, the widest range of procedures are used, such as cutting, printing with a diverse range of printing methods, folding, stamping, glueing and palletising. With a high degree of flexibility, Model is able to operate in an extremely dynamic (packaging) market, which is characterised by online purchases and increasing design variety.


Evian Trolley
The Evian display developed by Model AG was awarded the German packaging prize. Despite the fact the display shelves appear to float above Wimbledon tennis court, they each have a lifting capacity of 10 kg. A total of 108 500 ml bottles fit into the display.

Demanded (virtually) everywhere: compressed air as a source of energy and process medium

The question as to where compressed air is used in these processes is rather easy to answer explains Ernst Herzog, Technical Manager at Model AG: "They can be found any time, anywhere. We can't produce any products without compressed air." In paper systems and the corrugated cardboard system, numerous control valves are installed which are virtually all controlled pneumatically. In addition to this, process steps are involved such as blowing or feeding the paper through the dryer section, where compressed air comes into direct contact with the paper or corrugated cardboard as a process medium. What's more, the cameras and image-processing systems of the production-integrated quality assurance system are cooled using vortex nozzles, i. e. with compressed air.

In packaging production, a wide variety of pneumatic components and actuators are also used. Here, grippers, cylinders, and compressed air-operated handling units dominate the field.

CompAir Compressed Air Operated Handling
In packaging production, a wide variety of pneumatic components and actuators are also used. Here, grippers, cylinders, and compressed air-operated handling units dominate the field.

Gradual compressor replacement

The necessary compressed air was originally generated by four oil-lubricated piston compressors from the "Champion" range by CompAir. These machines - two in each station - generate 8.8 or 17.6 m 3 /min of compressed air at half or full load and, in doing so, work in an extremely energy-efficient manner, thanks to low gap losses, minimal off-load times and sophisticated technology.

There were two reasons why the team at Model AG wanted to replace the compressed air stations. Ernst Herzog: "The piston machines were approaching the end of their service life. As supply reliability is paramount to us, the machines needed to be replaced in a timely fashion. Furthermore, a large number of our customers operate in the food industry, which is becoming increasingly sensitive and demanding, particularly where potential ingress of foreign bodies in packaging is concerned. The solution for us was clear, a gradual conversion to oil-free compressed air generation."

Within 18 months, three of the four oil-lubricated piston compressors had each been replaced by an oil-free screw compressor. Graduation was used in order to be able to generate all the consumption profiles, which had been previously determined by CompAir based on measurements, as efficiently as possible: a large machine with a 300 kW

drive was used, which provides a maximum of 42 m 3 /min of compressed air to the 6.8 bar network. With 150 kW motor power and a maximum output of 23 m 3 /min, the other two compressors are considerably smaller.


Paper Systems Factory Photo

In paper systems and the corrugated cardboard system, numerous control valves are installed which are virtually all controlled pneumatically. In addition to this, process steps are involved such as blowing or feeding the paper through the dryer section, where compressed air comes into direct contact with the paper or corrugated cardboard as a process medium.

Three Oil Free Screw Compressors
The piston compressors were gradually replaced by three oil-free screw compressors with regulated speed. Image shows: the large screw compressor with a 300 kW drive provides a maximum of 42 m3 / min of compressed air to the 6.8 bar network.

Three speed-regulated compressors - one higher-level controller

The D series compressors can be relied upon in any application where users need an efficient and reliable supply with oilfree, high-quality compressed air. The profiles of the coated rotors ensure low gap losses, with a contactless and therefore wear-free labyrinth seal preventing ingress of foreign bodies into the compression chamber. All moving parts, such as roller bearings and the cooling system, are generously dimensioned so that the compressors can achieve long service lives. At the HMI, a modern microprocessor controller with touch panel ensures transparency. Alarm messages and service-related data are forwarded to higher-level control systems via an interface.

All three compressors are speed-regulated and are therefore able to precisely adjust the generated compressed air volume to the specific requirement. In practice, this saves up to 40 % of energy. A higher-level controller ensures that the most economical compressor combination is used to generate the volume flow currently required. In spite of the continuous operation of the main consumers, greater fluctuations are possible: in paper production and processing, there are process steps which temporarily require an extremely large amount of compressed air.


The next step: utilisation of waste heat

Even though the fourth oil-lubricated piston compressor has not yet been replaced, the aim of oil-free compressed air generation has (almost) been achieved, as this machine is kept as a back-up system. Nevertheless, this machine will soon also be replaced. In conjunction with this investment, one of the two compressed air stations is to be refitted so that the waste heat from the compressors can be utilised. Ernst Herzog: "We would have loved to have done this a long time ago and in paper production there is a need for heat all year round, for example, in spray water heating. However, the heat consumers are located quite a away from the station.

We will therefore wait until all our new systems are installed and then see where heat recovery would bring the most benefit in terms of energy."

Energy saving comprises various "key parts"

In parallel to the investments in the new compressors, Model AG has been working intensively - once again with support from CompAir - to optimise the compressed air network. The pipe diameters of the main cables have been increased and each machine now features an isolating valve. Ernst Herzog: "When the operator shuts down the machine using the mainswitch, the valve will automatically close. As a result of this and the new cables, we were able to significantly reduce leakages." Furthermore, the pressure loss in the compressed air network was noticeably reduced, thereby increasing the efficiency.


Microprocessor Controller with Touch
The four compressors are divided into two stations which supply the same network. A modern microprocessor controller with touch panel ensures transparency for the HMI.

Furthermore, a great deal of our customers operate in the food industry, which is becoming increasingly sensitive and demanding, particularly where potential ingress of foreign bodies in packaging is concerned. The solution for us was clear, a gradual."

Ernst Herzog, Technical Manager at Model AG

 

"Availability is the name of the game" 

Alongside the efficiency of the compressed air supply and the compressed air quality, supply reliability is paramount for Model AG. Ernst Herzog: "Availability is the name of the game for us." With this in mind, we have also set up a maintenance plan. The operations technicians and CompAir Service hold a monthly telephone conversation: "A conversation is more effective than an electronic report or data transfer, as the discussion can be more in depth." If a wearing part is required, it is readily available as CompAir has set up an on-site spare parts store. Furthermore, maintenance personnel and managers in the energy control room are trained by CompAir.

Integrated into the energy management 

For its paper factory in Weinfelden, Switzerland, Model AG has implemented a certified energy management system in accordance with ISO 50001: 2011 and is therefore obligated to continually optimise all production systems in terms of energy consumption. The managers take this task rather seriously - even during the planning phase and during operation of the compressed air supply. Not least because the investment in the new oil-free screw compressors was funded by the Swiss "Pro EDA" program (energy-efficient compressed air system program).

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