Massive cost reduction thanks to modern vacuum technology

Manufacture of paper valve bags by dy-pack
Massive cost reduction thanks to modern vacuum technology

dy-pack Verpackungen GmbH, located in Wenden (North Rhine-Westphalia), manufactures high-quality paper bags. Each year, around 250 million paper bags are produced 24 hours a day on six production lines, in the widest variety of designs and sizes. State-of-the-art manufacturing technology guarantees the products' high quality standard as well as reliable and effective production. dy-pack relies on vacuum technology from Dr.-Ing. K. Busch GmbH for handling the bags on the production lines and exclusively uses Mink claw vacuum pumps. In recent years, these pumps have gradually replaced the rotary vane vacuum technology that was used previously.

dy-pack Verpackungen GmbH is a family-owned business founded by Gustav Dyckerhof in 1950. Today, the company is managed by the third generation of the family. The company employs 190 of its 250-strong workforce at its main plant in Wenden. Since May 2009, dy-pack has been operating a further production plant in Mexico that caters primarily to the North American market. The company's product portfolio encompasses all types of paper bags, with a clear focus on open bags with volumes of 2 to 160 litres. dy-pack views itself as a partner their clients and strives to work together with the client to find the optimal technical solution. The company aims to incorporate all parameters, such as the material to be filled, the filling machinery to be used and the technical requirements for the paper bag, for example integrity, robustness and size. dy-pack's clients come primarily from the building materials, chemical and food industries. The company is a global market leader in the field of paper bags designed specifically for cocoa, for which hermetically sealed bags are supplied that fully protect the product.

The manufacturing process for the various paper bags is completely automated. In the first step, the paper bags are manufactured as an endless hose, which is subsequently cut to size. In the next step (fig. 1), the hose sections are folded up by vacuum suction devices. A base is glued to one side and the base with the valve is attached on the other side. The valve functions as a filler device when the client later fills the bag and is closed once the material has been filled. Up to 330 bags per minute pass through the individual production lines. Originally, dry-sealed rotary vane vacuum pumps were used on these lines to handle the bag hoses. The challenge with these vacuum pumps was the wear on the inside of the pumps, which continuously worsened the suction performance and the vacuum during operation. This wear also meant that the vanes in the vacuum pumps had to be replaced more frequently, inevitably leading to the shutdown of the entire production line if the vanes needed to be replaced unexpectedly. dy-pack views this scenario as the ‘absolute worst-case scenario’: "When investing five to seven million euros per production line, production must continue around the clock to achieve the quickest amortisation possible." As such, each interruption to the series production and the subsequent restart incurs extremely high costs.
One further disadvantage of the dry vane pumps was the noise produced by these vacuum generators, which made it necessary to install an acoustic to all vacuum pumps.

A new bottoming unit purchased in 2004 was already fitted with Mink claw vacuum pumps by the supplier. This unit marked dy-pack's first experience with the new vacuum technology from Busch. Management responsible for technology and repair work were surprised by the low noise emissions produced by these vacuum pumps, which eliminated the need for an acoustic enclosure. In fact, the new Mink vacuum pump was quieter without noise insulation measures than the previously used rotary vane vacuum pumps had been with an acosustic enclosure. One other evident benefit was the Mink claw vacuum pumps' compact design. dy-pack management focused more intensely on this new vacuum technology: the Mink from Busch is a claw vacuum pump with non-touching moving parts inside the pump (fig. 2). This means there is no wear. Effectively, the vacuum pump can operate with very little maintenance. There is no need to replace wear parts. The non-contact operating principle also does not require any operating fluids in the compression chamber, such as oil or water. All maintenance work connected with fluids is eliminated. A small amount of gear oil can be found only in the gear unit chamber of the Mink claw vacuum pump, which Busch states should be replaced every 20,000 operating hours. A comparison of the motor data from the rotary vane vacuum pumps used previously and the new claw vacuum pumps revealed a surprising fact: a Mink claw vacuum pump can operate with substantially less energy than a dry-sealed rotary vane vacuum pump. Thanks to its wear-free compression principle, no loss of performance during operation due to wear has to be taken into account when determining the pump size. In practice, this means that smaller sizes can be used. Costs for acoustic enclosures are also eliminated, which were generally fitted with additional fans requiring yet more energy.

In 2004, a rotary vane vacuum pump of 11 kW was replaced by a Mink claw vacuum pump of 5.5 kW at the bottoming unit on a production line. Since then, this pump has been operating in three-shift operation without a single fault or any repair work or necessary replacement of wear parts. Only the gear oil is replaced annually as a preventative measure. Please see table "Energy cost comparison" (fig. 3) to compare the technical parameters of both vacuum pumps as well as the energy costs. The annual recorded energy cost saving of €3,316.50 does not take into account the energy saving from the fans on the acoustic enclosure. Further operating costs are saved through the elimination of maintenance work, wear parts and shutdown times. Following this experience with the Mink claw vacuum pump, production management at dy-pack decided to successively replace all existing rotary vane vacuum pumps. Six Mink claw vacuum pumps are now in fault-free, three-shift operation on the production lines and are multiplying the cost savings accordingly.


Uli Merkle • 18 June 2010