MISUMI is proud to welcome Bosch Rexroth to their expanding brand portfolio. They shared with us their knowledge on the requirements for different types of industry zones for food applications and linear motion technology. Read more below.
Different requirements apply to different processing areas. For Linear Motion Technology components, this means a variety of specific requirements that products must meet.
Components used in the food production process must be easy to maintain in order for precautions to be taken against microbiological contamination. This means the components must be easy to clean and must be protected against contamination.
In general, it is unusual for Linear Motion Technology components to come into contact with food. If they do, however, the surfaces must be resistant to the foodstuff. In addition, these surfaces must be easily accessible to allow both visual inspection and manual cleaning.
The EN 1672-2 standard from the European Union defines three different zones which pose different requirements for selecting Linear Motion Technology components.
This zone includes all surfaces that come or could come into contact with food where there is a risk of food splash returning into the food process. In addition to the general requirements, the materials used must be corrosion-resistant and non-absorbent. The design must permit thorough and complete cleaning, with a surface finish which will prevent particles from remaining in small cavities. The use of bolts, screws, etc. should be avoided.
The surfaces should be self-draining and without dead spaces. Food grade lubricants should be used. These requirements also apply to other areas if there is a risk of cross-contamination.
This includes surfaces where the food may splash or flow along, but where there is no risk of it remaining in the food process. The requirements on materials and design are similar to those for the food zone but somewhat less stringent. Non-edible lubricants may be used, provided that this has no adverse effect on the food product.
All zones that are not food zones or splash zones. General requirements apply here. Any exposed surfaces should be made of corrosion-resistant or corrosion-protected materials. The surfaces should be easy to clean and self-draining wherever possible.
Wet working zones
Zones in which liquid, moist or sticky food flows around the machine parts, or areas which are wet-cleaned or disinfected. Linear Motion Technology components must be selected having regard to their exposure under known conditions of pressure and time.
Dry working zones
Zones in which no water or wet media can come into contact with machine parts and where the relative humidity is equal to that of the normal area (up to 70%).
Whether dry or wet cleaning is used, the cleaning process is a basic requirement for hygiene in the food industry.
The choice of materials for machinery and equipment in the food processing and packaging industry depends on the detergents and cleaning methods used. Looking at the matter another way, good hygienic design enables cleaning to be done in a shorter time, at lower temperatures and with less aggressive detergents, thus saving time and expense.
To select the right components for a specific application so that they will withstand the cleaning process, the components should be judged by their corrosion resistance, hygienic suitability and their electrical protection rating.
Cleaning of food machinery and equipment must take place in accordance with the manufacturer’s instructions. Detergents, too, must be used as directed by the manufacturer. It is important that materials, detergents and cleaning methods are compatible with each other.
The rankings given on the following page are based partly on information from leading detergent suppliers and partly on our own practical experience. The most important exceptions to the above in our experience over the years are as follows:
If POM plastic (polyoxymethylene) is not properly dried after cleaning with acid, there is a risk of formaldehyde being formed. In general, the characteristics of plastics differ from case to case and from grade to grade. The risk of absorption must therefore be considered. Our own experience with plastics in the food industry is better than the tables normally indicate.
Carbon steel is resistant to alkaline cleaning. The difference between corrosion-resistant steel and carbon steels becomes very noticeable in strongly acidic environments. However, phosphoric acid is commonly used in detergents, and low-grade steels such as AISI 420 can withstand this for short periods. It must be remembered that detergents usually contain inhibitors which protect the material.
One of the biggest risks is galvanic corrosion. This occurs, for example, when corrosion-resistant steel is placed in contact with aluminum in a wet environment. Aluminum cannot withstand either strongly alkaline or strongly acidic conditions. Its resistance can be improved by anodizing or coating, but improvement will depend on the quality of the surface treatment.
Generally, surface treatment is good, as long as the coating remains intact. If it is damaged, this can increase the rate of corrosion.