Sign up for the Coperion newsletter to receive the latest updates

Simple, residue-free cleaning of bulk material components

Wet or dry? – A question of philosophy

Production systems must be cleaned regularly to satisfy the stringent requirements of the food industry. The cleaning method – whether dry or wet – is often a question of philosophy. Both have advantages and disadvantages and each must be customized to suit the individual product requirements.

Dry cleaning is a suitable process for products with low internal moisture content. These are products that normally do not become contaminated with micro-organisms or mold or which are soon thermally treated after conveying. Dry cleaning is also used if the same product is always produced in the same plant or line and cross-contamination with other products is not possible. For the advocates of dry cleaning the advantages are obvious - if a plant is kept completely dry, as a consequence the microbiological risks are low. The decision as to whether frequent or only occasional dry cleaning is necessary depends on the product characteristics. The design of the component can be simpler than for wet cleaning. However, in all cases the bulk material components must be easily accessible, quick to dismantle and suitable for manual dry cleaning. In response to these requirements Coperion developed the WYK bulk material diverter valve, the ZRD Hygienic Plus rotary valve and the ZXD Hygienic Plus blow-through valve. All three have now been certified by the European Hygienic Engineering & Design Group (EHEDG), especially for dry cleaning (ED certificate).

Coperion's ZRD Hygienic Plus rotary valve - best access from both sides

With wet cleaning the use of liquid cleaning media makes it possible to clean components so thoroughly that they are absolutely free from residues. This is particularly important, for example, when producing flavors. Wet cleaning requires the use of materials that are resistant to the cleaning media. In addition, all areas in which liquid could be retained (such as seals) must be designed without dead zones or are at least freely accessible and easy to dismantle (COP = Cleaning Out of Place). Coperion supplies special components for wet cleaning that do meet all these requirements and feature a particularly smooth inner surface.

Since many components such as bulk material diverter valves are often installed in locations that are not easily accessible and where manual cleaning would be complicated and expensive, the trend is moving towards fully-automatic CIP wet cleaning (CIP = Cleaning In Place) so that the equipment can be cleaned without having to dismantle and open the components after every washing process. System operators are urgently advised to only use CIP components that have been certified, as this ensures that they can be cleaned fully automatically and are completely free from contamination. Coperion was the first manufacturer to launch rotary valves and diverter valves for CIP cleaning on the market several years ago that were certified by the EHEDG to "EL Class I". The ZRD-CIP discharge and conveying rotary valve, the ZFD-CIP blow-through valve and the WYK-CIP bulk material diverter valve are made of high-quality materials and have an outstanding, smooth-surface design without recesses and dead zones. The advantages of fully-automatic CIP wet cleaning will ensure that this method will gradually win through in the industry. For a long time CIP was still in its initial stages, as there were hardly any suitable components available. In the meantime, however, important key components are available in the form of Coperion's range of CIP rotary valves and diverter valves.

  • Jochen Sprung

    Head of Sales and Business Development, Coperion

Subscribe to the Coperion Newsletter