Sensors in hygienic conditions

Achieving reliable results, even in harsh conditions, is particularly important in food production and processing. Supplying contaminated or inedible food can result in considerable financial losses and a damaged reputation.

One method of fulfilling the strict hygiene standards that apply in this context is to clean the systems using high pressure every day; however, this means that the individual components are exposed to strong thermal and mechanical loads as well as aggressive chemical cleaning agents, which presents a real challenge to sensors.

Organisations such as the EHEDG (European Hygienic Engineering & Design Group) and the American 3-A Sanitary Standards are developing guidelines for hygienic machine and system construction — including the components used in the systems. In an age of globalisation, we rely more and more on harmonisation between these guidelines and the certification criteria.

Washdown and hygienic design

Machines and systems which process foodstuffs are arranged in different zones in accordance with the relevant hygiene requirements:

Zone B

Splash zone (cleaning zone, washdown): Washdown indicates that the splash zone of a machine can be wet-cleaned well and quickly. With this type of cleaning, there will be very few or no residues (foodstuffs, cleaning agents, water) left on the surfaces. Sensors in the splash zone must therefore be rugged when exposed to cleaning agents and high-pressure cleaning.

Zone A

Foodstuff zone (hygiene zone): For ‘hygienically designed’ machines and the sensors used in these machines, certain additional standards apply. A machine is considered to be hygienically designed if it remains free from product residues during use, as this forms an ideal breeding ground for germs. Consequently, it is important to avoid dead space and open joints when designing components.

Sensors that are designed in accordance with hygiene standards are constructed in such a way that they can be used directly in the foodstuff zone (hygiene zone) of a machine. Fewer build-ups of product deposits means less cleaning, in turn reducing the amount of detergent, water and energy required. The system throughput increases thanks to shorter cleaning intervals — this can be an economic benefit, particularly if products are changed frequently.

The material makes all the difference

To ensure the reliability within the particular requirements of the food industry, sensors are manufactured in a range of housing materials:

Stainless steel (Inox)

Sensors enclosed in stainless-steel housing are chemically resistant, rustproof and durable. They guarantee chemical material resistance and absolute tightness during intensive cleaning and disinfection.

VISTAL

A high-strength plastic, reinforced with glass fibre, boasting mechanical properties which exceed those of conventional plastics. A VISTAL housing can reach a level of mechanical strength and tightness sufficient to receive a rating of IP69K.

PTFE

A PTFE coating ensures all-round protection for the sensors and cables. The PTFE plastic is not affected by solvents or other aggressive chemicals. Its surface is so smooth and slippery that hardly any external substance can stick to it, making it suitable for use in hygienic and wet areas.

Housing with the enclosure rating IP69K

Housing with the enclosure rating IP69K guarantees that the sensors and their accessories will stand up to intensive cleaning processes, regardless of whether these involve a high-pressure jet of up to 100 bar or water temperatures of up to 80°C.

Hygienic accessories

What use are hygienic sensors if the mounting components provide a breeding ground for germs? Mounting systems should also fully comply with EHEDG recommendations; connecting cables can be made of PVC with M12 plug connectors for use in the food and beverage industry. With Ecolab certification and enclosure rating IP69K, users can be sure that connecting cables are resistant to the cleaning agents and disinfectants for which they have been tested.