Hygienic sensor solutions: Immune to germs and bacteria

Stainless-steel sensors from SICK deliver exceptional performance combined with compact dimensions, chemical and thermal material resistance, and lasting impermeability. Furthermore, all of the opto-sensory device types in the photoelectric sensor product families, for example, are also available in stainless-steel versions — energetic photoelectric proximity sensors, photoelectric proximity sensors with background suppression, through-beam photoelectric sensors, and photoelectric retro-reflective sensors.

The stainless-steel sensor portfolio from SICK also offers suitable solutions for safety technology tasks, the identification of products and containers, position monitoring and path measurement, pressure, temperature and level measurement, and the inspection of packaging and its contents. These solutions offer the highest level of process reliability for the manufacturer and maximum product safety for the consumer. At the same time, they ensure reliable functioning and consistently high levels of availability even under the harshest application conditions — because the automation tasks must not impact negatively on the hygienic design.

Product contamination: Three hazard zones in practical applications

Hygiene-compliant sensors ‘shine’ not only on account of their stainless-steel housing but also as a result of numerous other measures that guarantee the best possible chemical and thermal resistance as well as impermeability. These reasons — and the lower quantities compared to standard sensors — justify a correspondingly higher price level. It is therefore worth taking a look at practical examples such as a cutting and processing machine in the meat industry, a dairy machine for cheese production, and a filling and capping line in a beverage bottling plant. Each case involves typical plants that have to be cleaned and disinfected regularly to prevent hygiene risks resulting from intermediate or end products becoming contaminated with microorganisms, spores or inorganic residues. In terms of possible contamination risks, the machines and plants can be divided into three hazard zones, with corresponding consequences for the components that are to be used there.

Zone C is the non-food area of a machine where sensors can be protected by covers, for example, or mounted in such a way that they cannot come into contact with food. Standard sensors can, therefore, be used in this zone to enable economically efficient automation solutions.

Zone B is the area of a machine where external surfaces and plant components are cleaned with cleaning agents and disinfectants. In this area, standard sensors cannot withstand the required cleaning and disinfection, for example with a surfactant, acidic, chlorinated and chlorine–alkaline foam cleaners, or neutral disinfecting agents or those containing hypochlorite or peracetic acid, as well as the use of high-pressure cleaners with pressures between 80 bar and 100 bar. Stainless-steel sensors and components in a washdown design are the ideal solutions in this case. They offer the required robustness and are designed (eg, with bevelled surfaces or rounded edges) so that cleaning and disinfection media can run off leaving an as little residue as possible.

Sensors used in Zone A — where they are near the product — also undergo extremely demanding cleaning and disinfection processes. Also, however, they must meet special hygiene requirements and comply with recommendations, standards, ordinances and regulations relating to hygiene. These situations call for stainless-steel sensors with a hygienic design, which offer maximum protection against germs and contamination risks.

Hygiene as a chain of competency: Safe sensor solutions with no weakest link

The portfolio of stainless-steel sensors and accessories from SICK offers hygienic solutions for flexible automation, protecting machines and processes, for quality control and identification applications. To ensure the continuous and long-term safety of products and processes, it is necessary to meet a variety of requirements concerning the chemical resistance, thermal resistance, impermeability and structural design of the stainless-steel sensors while adhering to market standards. These are interrelated like the links of a chain, where the weakest link will determine the suitability of the sensor or system solution for hygienic applications.

*Christian Freudig is Product Manager Business Unit Photoelectric Sensors & Fibers, Global Business Center Presence Detection and Marco Kaiser is Strategic Industry Manager for Consumer Goods – Packaging, Global Industry Center Factory Automation, both at SICK AG, Waldkirch, Germany.