Putting hygienic design into practice

12 October 2020

Food manufacturers must adopt the principles of hygienic design, right down to component level, in order to minimise the risk of contamination.

Failing to meet food safety standards and regulations can have serious consequences for food manufacturers, including product recalls, fines and a loss of brand reputation.

To avoid these scenarios, manufacturers apply hygienic design principles to the production environment to minimise the risk of bacterial growth and contamination. However, applying such hygienic design principles at component level, to stop bearings acting as traps for food, for instance, is far more challenging.

First principles

Hygienic design insists that plant and machinery is easy to clean, does not harbour germs and reduces the risk of cross-contamination (such as through cleaning fluids or other contaminants). It is also vital that applying the rules helps to make production easier, boost profitability and efficiency.

The principles of hygienic design are set by the European Hygienic Engineering and Design Group (EHEDG), with clear guidelines for food manufacturing machinery and factories. Some of the key principles include: cleanability, preventing ingress and growth of bacteria, avoiding contamination and choosing suitable materials of construction.

Ease of cleaning helps to maintain high levels of food safety. Environments that are hard to clean will need more rigorous, time-consuming procedures and aggressive chemicals. This can mean higher costs, reduced machine availability and shorter equipment lifetime.

Designs should look to prevent ingress of bacteria, which is especially pertinent in small components such as bearing housings. Where possible, machinery and production environments should avoid traps, such as dead areas, gaps and crevices, where micro-organisms can grow.

It is not just micro-organisms that need to be repelled; food particles and cleaning chemicals can also cause contamination. Components that wear down can generate tiny particles, for example, while detergents can work their way into bearings and into food. Some of these problems can be overcome by choosing appropriate long-life materials and servicing key components such as seals and gaskets regularly. With this in mind, stainless steel, polymers and elastomers are often specified as construction materials.

Food Line range

Preventing small components such as bearings from acting as traps for pathogens and allergens can be a challenge.

SKF has used hygienic design principles to develop its Food Line range of bearing units, called Blue Range. The units combine smooth, inert surfaces with a self-draining geometry, to prevent ingress of chemicals plus superior sealing.

Several innovative design elements combine to prevent typical food safety problems, such as trapped microbes, leaking lubricant and detergent damage.

The housing is injection moulded from polypropylene (PP), an inert material with superior chemical resistance. Glass fibre reinforcement helps to enhance its mechanical properties. The housing is co-injected with a rubber seal, sealing the interface between the frame and housing to avoid crevices and empty spaces for bacterial growth.

The bearing grease used is allergen-free, and the sealed design ensures that relubrication is not required. In addition, components are coloured blue for easy optical detection.

The bearing seal gutter concept is a new way of protecting against detergent ingress, which is a major challenge. SKF’s gutter concept allows detergent through but guides it towards non-hazardous areas. So, if a cleaning solution enters the top lip of the seal during washdown, it is automatically guided around and out of the other side of the seal.

Successful results

The Research Institutes of Sweden (RISE) performed a washdown test to compare the performance of the new units with SKF’s existing food and beverage bearing units. One key result was that, because the new units were more resistant to contamination, they required one-third less water to clean them.

In addition, several customers also reported positive results, especially in terms of avoiding relubrication. One food manufacturer, for instance, was using bearings that needed frequent relubrication. Installing SKF’s Blue Range units eliminated this on both conveyors and elevators. Within the same plant, heavy contamination in processing machinery was made worse by an aggressive cleaning regime which was destroying the bearing grease. A year-long trial of sealed Blue Range units solved the problem. Units have since been fitted more extensively, saving cost and improving compliance with food regulations.

Adopting hygienic design principles is well established within the food sector. Applying them all the way down to component level, as SKF did with its Blue Range of sealed bearings, will help to realise the full benefits of this approach.

https://www.skf.com/uk/products/mounted-bearings/ball-bearing-units/skf-food-line-ball-bearing-units