Everyone probably knows "Dove". Unilever produces 800 million of these wash items in Mannheim every year, and the trend is rising. "Just don't write the word with an 'S' at the beginning," asks Tobias Bernhardt, head of maintenance here, right at the start of our visit. "What we produce are wash pieces!" The formula of the "Dove" syndet cares for the skin and is therefore of higher quality. "That's right, soap dries out the skin," agrees the photographer.

Unilever produces its synthetic wash pieces ("Syndete" = synthetic detergents) in four factories worldwide: in Germany, the USA, Brazil and Indonesia. The pieces look the same everywhere and bear the same characteristic lettering and the dove. Different sizes are produced, from 50 to 135 grams, in around two handfuls of fragrances. There are 160 different end packs for "singles", packs of two, packs of six and other quantities.

To convey the semi-finished product to the packaging lines, Unilever now uses four ZS 30 VSD screw blowers from Atlas Copco. The machines are all speed-controlled and each supplies one packaging line with compressed air at around 0.4 to 0.5 bar (operating overpressure). "Nobody in the team wanted centralized piping," explains Tobias Bernhardt, "partly because the regulation would have been too complex." The semi-finished product leaves the extruder in the form of tough, cylindrical sticks, so-called "noodles", which are very short and thick. In order to convey these from the extruder to the buffer silos and the subsequent packaging lines, the air flow must be as constant as possible. "The product must be constantly kept in suspension," explains the maintenance manager. There is no standstill in the process, and if the pasta pieces come to a standstill in the conveyor pipes, more energy and therefore higher pressure would be required to get them moving again.

At the start of each packaging machine, fragrances and colorants are added for the variant to be produced. © Atlas Copco

Perfume and color are added on the packaging line
The "noodles" fall from the extruders into the connected hopper and from there via a rotary valve vertically into the transport pipes, which are located in the floor. Compressed air is present in these pipes, which is generated by the screw blowers to pneumatically convey the powdery intermediate product into the packaging area. The "noodles" are distributed to seven silos via distribution diverters in front of the five final packaging lines. The wash pieces are given their final specification on the lines themselves: perfume and color are added here, the semi-finished product is mixed homogeneously and extruded under high pressure into an endless strand. This is cut into rods about 50 centimeters long, from which ten to 14 wash pieces are then punched. The punching waste is transported straight back and reprocessed. "So we don't have any rejects here," says Tobias Bernhardt happily. The die-cutters emboss the gliding dove into each individual wash piece before it is packed in a folding box.

Unilever purchased the first Atlas Copco screw blower in Mannheim in 2016 to replace an old rotary lobe blower from a competitor. "We also had four of these machines," says Bernhardt. "They were around 20 years old, were too loud for us - and there was no longer a replacement for the sound insulation."

Oil-free compression and efficient operation
Bernhardt and project engineer Ulrich Kahnert scoured the market and found the oil-free compressing ZS blowers at Atlas Copco. "In addition to being oil-free and quiet in operation, we were primarily looking for a more energy-efficient solution," explains Ulrich Kahnert, who was the chief maintenance engineer before Tobias Bernhardt and had the idea for the further development of the compressed air station. "The result was so convincing that, following the successful introduction of the first ZS screw blower, we launched an energy-saving project to replace the other three old machines as well."

Over the course of the following year, 2017, these three positive displacement blowers were replaced. "The project was a complete success," summarizes Tobias Bernhardt. "We previously needed 3,130 kilowatt hours per week and system, and now it's only 2043 kilowatt hours." Almost 35 percent less. "We can say that very precisely, as our lines here run practically around the clock, including Christmas and New Year's Eve." In addition to the far better energy efficiency, Bernhardt cites the better price, the maintenance-free direct drive and the already installed frequency converter as reasons why the decision was made in favor of Atlas Copco. He also rates the cooperation during maintenance appointments - Unilever has booked a full service package with extended warranty - and the seminar on compressed air accessories, hoses and more held by Atlas Copco as positive. "On the first machine, the intake side had to be adjusted a little, but this small challenge was resolved very quickly. Now the four screw blowers run extremely reliably 24 hours a day." as