Power Consumption Cut in Half Thanks to Vacuum

Energy savings of up to 50 percent and effortless maintenance: These are the benefits that Klinkerdachziegelwerk KDW, a producer of clinker roof tiles, has experienced since starting to use a COBRA screw vacuum pump from Busch Vacuum Solutions for clay degassing.

The clay is piled high in the entrance hall of the KDW clinker roof tile factory in Natrup-Hagen, near Osnabrück. A conveyor belt carries the material to a circular screen feeder. This is a powerful, cylindrical machine that optimally mixes, humidifies and homogenizes various clays until the perfect starting material for the high-quality KDW roof tiles is ready. Later in the course of production, the clay mass prepared in this way is compacted using vacuum, so that the finished tiles have a particularly homogeneous appearance. This process is carried out by a clay degassing system from Busch Vacuum Solutions, the core of which is a COBRA NX dry screw vacuum pump.

KDW is the smallest roof tile factory in Germany. In single-shift operation, the workforce works around nine hours on weekdays and half a shift on Saturdays, producing between 125,000 and 130,000 tiles per week. KDW obtains its clays, which are usually slate clays, from several pits in the surrounding area. The factory was founded in 1990 and has 25 employees. It is part of ABC-Klinkergruppe, an owner-managed manufacturer of high-quality ceramics for roofing, facades, veneering and flooring with a total of 250 employees at six production sites. The group has around 135 years of experience.

Reduced energy consumption and easy maintenance

KDW operations manager Ingo Hofmeister examined the dry screw vacuum technology from Busch in another brickworks facility and was convinced of its benefits. He therefore decided to test a COBRA NX for clay degassing. Initially, it was only planned as a backup for the liquid ring vacuum pump previously used at KDW for this purpose. But even after a short test phase, the plant manager was so convinced by the COBRA that he decided to use it permanently. “I quickly realized that holding back the COBRA as a replacement pump for emergencies did not make sense, because it is really low-maintenance and we don't have to top up operating fluids,” says Ingo Hofmeister enthusiastically. "Its energy consumption is also much lower. That’s why it’s now doing the clay degassing work. We still keep the liquid ring vacuum pump as a spare. However, it hasn't been needed at all so far."

The COBRA NX degasses the clay and dries the plaster molds. First, it extracts trapped air bubbles and gases from the material as it passes through the vacuum chamber between the double-shaft mixer and the extrusion press. If air and gas bubbles are not removed from the clay, they could cause cracks to form during firing, or shorten the lifetime of the tiles. The clay columns are then cut into individual clay blanks at what is known as the cutter. From here, they are carried via four parallel conveyors to a revolver press, where they are pressed into their final shape between two gypsum molds. There, the COBRA NX extracts the water that is pressed out of the material during the pressing process through the molds. This prevents water stains and marks on the tiles. This avoids unnecessary waste during the production process and increases productivity. Degassing the clay and drying the plaster molds also ensures the homogeneous appearance and high, frost-resistant quality of KDW roof tiles.

Energy-efficient degassing with VSD

The COBRA NX, which Hofmeister uses in the clay degassing system, is equipped with a variable speed drive (VSD). This adjusts the rotational speed of the motor and maintains a constant vacuum level. If the vacuum demand decreases during the production process, this results in a reduced rotational speed and thus lower energy consumption. This may be the case, for example, if the clay is less moist and therefore less humidity must be extracted in the air from the vacuum chamber. Thanks to the highly efficient COBRA with its variable speed drive unit, KDW benefits from considerable energy savings compared to the unregulated liquid ring vacuum pumps, which were continuously running at full power. Energy savings of up to 50% can be achieved by adjusting the rotational speed to the actual demand. "The liquid ring vacuum pumps always drew full power. The COBRA, on the other hand, easily regulates itself, even in a damp, dirty environment," explains Ingo Hofmeister.

In fact, it’s no problem for the COBRA NX to degas masses that contain moisture. It has an anti-corrosion coating, which gives it a particularly long service life even in damp and dirty environments. The Busch specialists also installed a standing filter upstream of the COBRA at KDW for the separation of dust and particles. This saves space, is easy to clean and also protects the vacuum pump from damage due to contamination. A control cabinet, inlet filter and cooling water circulation unit complete the COBRA clay degassing system.

A good supply of spare parts

For KDW’s operations manager, it is particularly important ensure smooth production. That is why he is pleased with the fast service provided by the vacuum specialists from Busch: "So far, we have not needed any spare parts for the COBRA. But it’s good to know that they’ll be available immediately in case of an emergency. We sometimes had to wait weeks for spare parts for the liquid ring vacuum pumps." The operations manager is also very satisfied with the minimal maintenance effort for the COBRA: "We only need to service the COBRA once a year. Otherwise, we occasionally change the filter. But even filter replacement is very straightforward. The vacuum pump tells us when it’s needed."

Ingo Hofmeister is sure that he chose the technically optimal solution when he selected the COBRA NX: "Because the vacuum pump from Busch runs so well, we are even considering replacing all of our liquid ring vacuum pumps with COBRAs," he explains with satisfaction.