Ekato, a manufacturer of customised industrial agitators, has scaled up the largest model in its Unimix line to more than double the original size. Two mixers, each with an effective volume of 10,000 litres, produce up to 11,000 kg of toothpaste per hour. Drive specialist Nord Drivesystems supported the development of these new record-sized systems.
The authors: Alexander Lukas Head of Research & Development, Ekato Systems Peter Dittmers Managing Director Germany, Nord Drivesystems
Many manufacturers with a global reach are keen to concentrate their production capacities in just a few places. The hygiene and personal care industries certainly follow this trend. There is accordingly a demand for ever larger batch sizes for products such as toothpaste. Furthermore, a wider range of variants is manufactured at each site. Modern plants must therefore be capable of producing large volumes while at the same time providing maximum versatility. With its sights set on this complex task, Ekato Systems of Schopfheim, on the southern fringe of the Black Forest, recently constructed a new batch production plant for toothpaste.
The maximum capacity of toothpaste production plants used to be between 4000 and 5000 l, with outputs of approximately 2000 to 3000 l/h. Continuous or batch production is possible. Continuous systems enable high throughputs but are not very versatile with regard to product changes; since different ingredients sometimes require their own dispensing and blending technology, modified recipes often necessitate conversions and readjustments. Another aspect is that toothpaste cannot be reworked easily if it is not sufficiently homogeneous. The biggest challenge with continuous plants is ensuring that active ingredients such as sodium fluoride are dispersed uniformly, for instance after changes to the dispensing systems. On the other hand, the production rate of existing batch plants cannot be significantly increased without major modifications to the equipment. In order to meet the demands of a toothpaste manufacturer, Ekato therefore had to build larger plants.
Production mixer design
Toothpaste production lines basically consist of an evacuable vessel with an agitator, a homogeniser and various dispensing systems for introducing the ingredients into the process. Liquid ingredients are either measured and then inserted into the vessel under vac-uum or dispensed by gravimetric methods. Powders and thickeners to increase the viscosity can be added via the integrated homogeniser or drawn into the vessel through a valve at its base.
For larger mixer dimensions, Ekato had to determine the components’ dosage, dispersion, blending and homogenisation times, the vac-uum values and the necessary agitator and homogeniser capacities. The agitator and homogeniser were configured according to the following two equations for mixing capacity:
P = Ne·r·n3·d5 for turbulent flow
P = Ne·r·n2·d3·h for laminar flow
Ekato determined the power coefficient “Ne” (or Newton number) for each respective impeller and the product’s specific viscosity curve based on its longstanding experience. In addition to the product concentration r, the equations also include the speed and diameter; these values are especially important with an exponent of 2, 3 or possibly 5. Correctly configured agitator and homogeniser drives are therefore crucial. Nord, the drive supplier, was required to configure motors and gear units with the outputs calculated by Ekato and make them as efficient and durable as possible. Since the agitator drive is installed on top of the production mixer, it needed to be very compact despite the high performance demanded.
Agitator drives as large as a city car
This application, which depends on homogeneous product quality, called for speed and continuity. The radial and axial loads on the agitator shaft, which are very high due to the high product viscosity, had to be taken into account when configuring the drive. Nord Drivesystems configured and supplied two 250 kW motors with industrial gear units that provide a nominal output torque of 242,000 Nm. Nord is the only manufacturer worldwide to make such enormous industrial gear units in this power range in the proven one-piece unicase housing. The type SK 15407 3-stage helical bevel gear units, although impressive in size, are thus still relatively compact as the unicase design allows larger rolling bearings that can accommodate higher forces.
Conclusion
With an effective volume of 10,000 l each, the two new production mixers achieve a maximum of 12,000 to 16,000 kg of toothpaste per batch, depending on the product density. This equates to a product output of between 6000 and 11,000 kg per hour. Compared to the 2000 or 3000 litres from what was previously the biggest plant, this means a three- or fourfold increase in productivity. In other words, the customer’s target was not only realised but surpassed. An additional advantage is that the compact design enables the available production space to be optimally utilised. The drive systems have to meet the same requirements as the mixing technology, namely combine maximum reliability with minimal mainte-nance.
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