Hygienic design in process technology


Saving energy, time and cleaning agents: technical solutions for efficient cleaning

With machines and systems in hygienic design and optimised cleaning processes, resources can be saved for cleaning, and system availability can be improved. The mixing and dispersion technology specialist ystral has developed different technical solutions for effective cleaning.

Process system from ystral with tank cleaning machine TRM100 (1), rinsing quiver for cleaning suction hoses (2) and the YSTRAL Conti-TDS disperser (3).
(picture credits: ystral)

The rules of hygienic design aim for complete cleaning and emptying of a machine or plant with the lowest possible use of cleaning agents. ystral machines and plants are increasingly designed according to these rules: Every flange, every seal of a mixer or disperser has been designed in a way to enable easy and complete cleaning – without gaps, threads or hidden zones. Even areas such as the underside of a mixer flange can be cleaned without shadows by means of special cleaning heads.

Disperser used as CIP pump

In order to render cleaning processes as easily as possible and limit the time needed for cleaning, ystral integrates CIP technology directly into the system, and the conveyor effect of the available machines is used for cleaning whenever possible – a separate pump is then no longer needed. An YSTRAL Conti-TDS dispersing machine operated in the circuit can thus not only be used for processes such as induction, wetting and dispersing of powders as well as pumping the complete product, but also for circulation of the cleaning medium. For GMP-suitable cleaning, the flow rate of the cleaning medium must be at least 1.5 m/s to prevent the formation of sediments and create sufficient turbulences. With ystral, independent of the size of the system, the flow rate is usually even 2 m/s.

ystral also uses the conveyor effect of the YSTRAL Conti-TDS disperser for its tank cleaning machine TRM100, which compared to other cleaning systems enables a significantly higher liquid throughput – up to more than 50 m³/h. The system has proven itself in practice, above all for circulation of cleaning liquid in vessel sizes between 5 m³ and 50 m³ as well as for users requiring high jet pressure for effective cleaning.

Cleaning with recipe components

ystral installed a process system for a manufacturer of printing inks specifically designed for paint changes, on which paint changes from black to yellow can be realised within measurable contamination limits of 100 ppm.
(picture credits: ystral)

So far, vessels have often been cleaned with cleaning agents at the end of a process. This takes time, and the cleaning waste generated must be processed or disposed of. An efficient alternative with technologies from ystral is cleaning with recipe components: One option here is the saving of liquid raw materials during the production of the batch, with which the system is rinsed into a letdown tank subsequent to pumping out. For example, pigments are left in the process directly and must not be separated from the cleaning agent.

In case of subsequent batches with similar raw materials, cleaning is integrated into the process and does not occur at the end in this case, but at the start of the following process. Residues of the previously produced product are utilised here in the subsequent batch. During filling, they are rinsed out under high pressure – not with cleaning agents, but recipe components of the subsequent batch. Cleaning waste, which must be disposed of and processed, is not generated here. 

No surface drying of the product in the vessel

When powder is induced from the top into an open vessel, dust above the liquid on damp surfaces results in adhesions, powder crusts and contaminations on the vessel wall, cover, agitator shaft and all fittings in the vessel, the removal of which is time- and energy-intensive. However, in closed systems with powder induction below the liquid level, the cover space of the vessel can be kept largely clean.

Depending on the application, ystral also uses spray nozzles, for example to prevent water-based paints from drying when pumping out the product. Such a nozzle is used to finely nebulise the main liquid component in the vessel, thus creating a humid atmosphere above the product to reliably prevent drying. This is not possible with an open process.

Cleaning concepts for the periphery

ystral also developed cleaning concepts for the system periphery with the powder and liquid handling and the cleaning of pump-out lines. For example, a specially designed rinsing quiver is used for cleaning suction hoses. This quiver enables the suction hose, which is contaminated with the raw material internally and externally, to be integrated into the CIP cleaning of the system in a connected state and thus be cleaned simply and quickly, secured by a clamping clip.

The YSTRAL Conti-TDS disperser. (picture credits: ystral)

Experiences from the food and pharmaceutical sector applied to other industries

In terms of cleaning processes, ystral uses experiences from industries with very high hygiene requirements, such as the pharmaceutical or food industry, for applications in very different industries. Therefore, an ystral machine, which is used for the production of paints and varnishes, can be cleaned just as well and quickly as a machine for the production of baby food or pharmaceuticals. For example, ystral installed a process system for a manufacturer of printing inks specifically designed for paint changes, on which paint changes from black to yellow can be realised within measurable contamination limits of 100 ppm.

In the production of varnishes and paints, systems with hygienic design also enable the production of water-based products with a significantly lower use of biocides. The consistent prevention of zones without or with low flow ensures that no germ nests can form.

Development of individual cleaning concepts

ystral solutions for the implementation of cleaning processes are always tailored to the specific system design and the respective application. For a manufacturer of fragrances, whose objective it is to implement cleaning processes energy-efficiently and with low use of cleaning water, ystral has integrated a flush water tank for example between two process systems, which is used by both systems. For cleaning an ystral system, the around 60 °C hot water is used from this tank for a pre-rinsing step, pumped out and the system is then cleaned in a second rinsing step using 80 °C hot water. After completion of fine cleaning, this water is pumped into the flush water tank, where it can be used for pre-cleaning in the next cleaning process. This way, the user could significantly reduce the water and energy requirement during cleaning.

What is also important for the fragrance manufacturer is that after hot water cleaning, the system can be fully dried within a short period. For this purpose, different valves are activated to blow out the residue of the cleaning medium in the system by means of compressed air. With hygienic design, a system can be dried automatically within a few minutes, only the manhole cover must still be dried manually.

Hygienic design as competitive advantage

Flexibility is vital today in many areas of the process industry: Manufacturers must be able to produce a large number of product versions and newly developed products order- and user-oriented, i.e. to realise frequent product changes. With an optimised system design and simple, fast and resource-saving cleaning, users from industries such as the coating, inks or chemical industry in particular, in which systems have so far often not yet been designed according to the rules of hygienic design, can achieve a competitive edge.


Denis Hunn
Process and Application Engineering
ystral gmbh maschinenbau + processtechnik