Hygienic design

Hygienic design means constructing equipment so that product residues, moisture and micro-organisms cannot lodge, and so that it can be cleaned completely and verifiably. It is not a matter of cleaning but of design: what is not built to be cleanable does not become clean with more detergent.

The basis is the specific requirements of EU machinery law for foodstuffs machinery, the standards EN 1672-2 and EN ISO 14159 and the guidelines of the European Hygienic Engineering and Design Group (EHEDG).

EN 1672-2 distinguishes three areas, and the requirements follow from them. In the food area the surface touches the product, or product can return from it to the main flow. In the splash area product may land but does not return. The non-food area comprises everything else.

A hoist rarely touches the product. But it often hangs above open product – and then what counts is what can fall: abraded particles, lubricant, condensation, paint flakes.

The rules all follow the same idea: no place where anything remains or escapes cleaning.

Austenitic stainless steels such as 1.4301 (AISI 304) and, where chlorides are present, 1.4404 (AISI 316L) are customary. For product-contact surfaces a roughness of no more than 0.8 µm Ra is often required. Plastics and elastomers in contact with food must comply with Regulation (EC) No 1935/2004.

Where lubricant may technically unavoidably come into contact with the product, lubricants with H1 registration are used. A design in which lubrication points are enclosed, or are not above the product at all, is better.

A lubricated load chain above open product is the classic conflict. Remedies are stainless steel chains, belts or ropes with suitable guidance, enclosed drives with drip protection, smooth stainless housings without horizontal ledges, and lines routed internally or laid so that they can be hosed down.

The IP rating comes on top: a device that is wet-cleaned daily needs suitably protected drives and operating elements, and materials that withstand the cleaning agents.