Hygiene-critical design

Machines involved in hygiene-critical operations need to have a design that facilitates easy and efficient cleaning.

Gaskets, seals and rough pipe surfaces are potential bacteria havens and hygienic challenges for the food and processing industry. The solution? Hygienic design.

Cleanability is Jürgen Hofmann’s watchword. Hofmann is about to take over a project run by the Fraunhofer Institute for Process Engineering and Packaging in Germany. It comprises an internet portal called hygienicprocessing.com, which will be a complete information source with regard to hygienic design, with tips, links, a database of literature and a network of experts.

Hofmann is one of the experts involved in this. For the past nine years, he has been teaching as an academic assistant with the Department of Process Engineering at the Technical University of Munich’s Weihenstephan campus, which specialises in all food-related matters.

“Hygienic design is relevant in all areas where it is important to keep equipment clean. This includes pharmaceuticals and cosmetics, and even paint,” he says.

In a way, the aim is simple — cleaning is carried out with liquids. These must be able to flow smoothly through all the piping, valves, taps and pumps of a machine. Hofmann’s job is to ensure that there are no gaps, holes, grooves or 'dead areas' that the liquid cannot reach. This requires smooth surfaces, curves that direct liquids in the right direction, and seals and gaskets that fit perfectly.

“In the milk industry, it was standard for seals to be set back from the inner surface of the pipes,” says Hofmann. “This created a gap where microorganisms could flourish. The problem is that much effort is needed to clean this kind of equipment. For example, it is necessary to leave cleaning liquids in the pipes for a long time. Such pipes are still used today, but we have helped to design a version where the seal and the inner surface are flush,” explains Hofmann. However, according to Hofmann, it is too often the case that investment decisions are made separately.

“There is one budget for investment, and another for maintenance, but you can probably save between 25 and 50% over the lifetime of the equipment by using hygienic design — particularly if there is a case of contamination, which can involve colossal costs.”

Not all food products are equally sensitive. For example, beer is less critical than dairy products, because alcohol kills pathogenic bacteria (which makes alcohol-free beer a bigger challenge). The contamination that may be found in beer makes it taste bad, but it is not life threatening. In dairy products, contamination can be more serious and cleaning is crucial. Moreover, some food trends, such as the move away from artificial preservatives, have made hygiene increasingly important.

For Hofmann, it does not matter what the machinery is processing, the cleaning substance must enter all areas and do its job. The university has a testing centre that conducts a cleanability test developed for the European Hygienic Engineering & Design Group (EHEDG). The centre runs a standardised contaminant through the part to be tested and through a reference pipe. A standardised cleaning process is subsequently performed using 1% alkaline detergent. Following this, Agar is used as a culture medium to detect how much contamination remains.

“I enjoy this work, because we can really make a difference,” says Hofmann. “We can influence processes and initiate trends. It’s wonderful when a company designs a new machine using concepts that we have developed.”