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Advanced and efficient vacuum supply in paper bag production

31 May 2018

GSD-Verpackungen - Gerhard Schürholz GmbH is specialized in the production of paper bags and paper shopping bags. The majority of the processing machines requires vacuum to hold, transport and finish the individual bags. GSD-Verpackungen has made energy savings of over 50% and reaped many other benefits for its advanced production systems by changing over from vacuum supply generated by individual vacuum pumps to the respective machines, to a centralized vacuum system from Busch.

GSD-Verpackungen was founded in Drolshagen in 1877 and has been owned by the Schürholz family since 1962. 60% of goods produced go to discounters, supermarket chains and wholesalers, which in turn supply bakeries or butcher’s shops, for example. Production is carried out with over 50 machines. The paper is delivered on rollers, and passes fully-automatically through all production steps from printing, to finishing, being formed (Fig. 1). The bags are stacked up ready to go at the end of the inline systems, and can be packaged immediately.

Vacuum is used to either hold or move paper, depending on the machine. In the past, a total of 22 rotary vane vacuum pumps of different sizes were in operation to generate vacuum. This was a thorn in the side of Production Manager Jörg Möller, because their heat emissions made the production hall hot and this worsened working conditions, particularly in summer months. It also meant high noise levels. The rotary vane vacuum pumps used were predominantly dry-running. This means they don’t use any oil for cooling and lubrication, but were equipped with self-lubricating carbon vanes. Their abrasion released a fine carbon dust into the air, which was deposited around the vacuum pump. Moreover, they need to be replaced regularly, which was associated with high costs. Jörg Möller was particularly aware of the issues with the aspect of energy consumption of the vacuum pumps.

Dr.-Ing. K. Busch GmbH then created a completely new concept for generating the vacuum for all production machines on all five inline systems. Production Manager Jörg Möller was so impressed by the concept that a centralised vacuum supply from Busch with five Mink claw vacuum pumps (Fig. 2) has been in operation since October 2016. These five vacuum pumps replaced the previous 22 rotary vane vacuum pumps, and still have enough power reserves to enable a sixth inline system to be connected. The centralized vacuum system is connected to all machines by means of one line, and guarantees the vacuum level can be maintained at 300 milibars throughout operation.

The benefits were clear even in the first few months after the centralized vacuum system was installed: no noise emissions or indoor air pollution from carbon dust around the workstations in the production areas.

There were also vast energy savings compared to the former decentralized vacuum supply. The Mink claw vacuum pumps are each driven by energy-efficient IE3 motors with 6 kilowatts of rated power, corresponding to energy consumption of 30 kilowatts for the five motors in total. In practice, the first few months of operation showed that demand-driven control of the new centralized vacuum system from Busch meant that only two or three Mink claw vacuum pumps at most need to be operational simultaneously. The actual power consumption is then 60,000 kilowatt hours a year, with a theoretical setup of 2.5 vacuum pumps and an operating time of 4,000 hours. The motor ratings of the rotary vane vacuum pumps used previously were 32.5 kilowatts in total, corresponding to an annual power consumption of 130,000 kilowatt hours. The result of changing from decentralized to centralized vacuum supply is a saving of 70,000 kilowatt hours, or 54% of the energy costs.

Mink claw vacuum pumps operate entirely contact-free (Fig. 3), meaning that none of the internal moving parts in the vacuum pump come in contact with each other. As a result, there is no wear, making this type of vacuum pump nearly maintenance-free. Busch recommends a preventive annual change of the gear oil when using the systems in 24-hour operation. This can be performed while the system is in operation, by switching off the relevant vacuum pump in the centralized vacuum system. Vacuum generation for production is still ensured by the four other vacuum pumps thanks to the cascade connection and the operation of one of the five Mink claw vacuum pumps with a frequency-controlled motor. For Jörg Möller, this means a significant reduction in the cost and time needed for maintenance work. The contact-free operating principle of the Mink claw vacuum technology is highly reliable, as it does not require wear parts. This means, for example, that carbon vanes breaking and causing a sudden and total vacuum pump failure are a thing of the past.

Industry Connections: Busch (UK) Ltd

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