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Technology Product 05.12.2016

Hygienic design principles for production systems in the food industry

In the food industry, product safety and product quality are crucial factors. After all, in negative cases, affected companies are subject to far-reaching consequences: These range from the costs associated with a potential product recall up to a catastrophic loss of image.

In addition, a number of different guidelines and standards, such as DIN EN ISO 14159, exactly stipulate the hygiene requirements for the design of machinery used in food production. For example, the machines must be designed and constructed so that the materials can be cleaned before each use.

Against this backdrop, hygienic design is increasingly establishing itself as a key component of modern production processes. The focus of hygienic design is the cleanability of the entire machine, individual materials, surfaces and constructive elements.

Clearly defined surface quality requirements

The principles of hygienic design are primarily orientated towards dangers in the product area, i.e. on circumstances that favour soiling and impede cleaning. One example is the surface topography: This largely determines the cleaning performance, the formation of biofilm and bacterial contamination as well as the accumulation and release of particles.

Risks include, for example, microscopic recesses and cracks on the product side that allow dirt and microorganisms to adhere to surfaces. Dirt can also become trapped faster and more strongly entrenched in macroscopic recesses and cracks.

Additional risks also lurk in hard-to-reach vertical surfaces, in unfavourable flow areas (dead water, backflow) and where the flow of liquid is hindered. Finally, there are exacerbating external risks: Microorganisms can penetrate through macroscopic and microscopic pores on the product side.

The task for the engineers developing machinery, systems and components is thus clear: They must avoid macroscopic, non-cleanable recesses and cracks – while preventing excessively rough surfaces, microscopic pores, pits and crevices.

Decisive interplay between myriad elements and connections

That means from the outset that the choice of materials is an important aspect in hygienic design. Due to its outstanding physical properties, manufacturers usually opt for stainless steel. The type of surface treatment and the surface morphology, however, also have a massive influence on the corrosion behaviour of the stainless steel.

Especially surfaces ground with a 240-grain or finer finish provide ideal conditions for optimised corrosion behaviour and targeted cleaning – surfaces ground accordingly are used, for example, in sheet metal claddings or tube frames.

When designing the morphology, it is thus important to first consider the interplay between myriad elements and connections on as well as in the immediate vicinity of the surface. Annealing colours from welding, for example, are relevant from a macroscopic perspective, and abrasive grain residues from a microscopic perspective.

Welded seams always represent a microbiological weak point. Therefore, the first and most important rule is to avoid welded seams, wherever possible. Otherwise, tungsten inert gas (TIG) welding should be used on stainless steels, as this guarantees high-quality welded seams.

In the optimal interplay of various elements and connections, both stationary and movable contact surfaces such as gaskets also play a crucial role: Metallic contact surfaces should be avoided, because bacteria can otherwise penetrate through the metal-metal bonds.

Increased efficiency in project realisation

Hygienic design considers all of these points – but won’t such a comprehensive design process make machines far too expensive? The experts all agree: Although the initial investment is higher, the savings thereafter are significant. Stefanie Dahmen, Product Manager of Sartorius Intec: "Machines that follow hygienic design principles require considerably less time to clean, are easier to maintain and also ensure greater safety by virtue of constructive elements such as smooth surfaces and few edges."

Hygienic design's innovative approach and its wealth of special design features increase efficiency during project realisation, help avoid costs and produce a sustainable production process.