Hygienic design for the food and processing industries

Tags: maintenance and reliability

Jürgen Hofmann unlocks a glass cabinet.

Look at this,” he says. It is a length of stainless steel piping, which has a short branch at 90 degrees with a bolted-on cover. “There used to be a sensor in here or a similar device, but it was removed and the tube was blocked off. This means that cleaning liquid cannot enter this dead end, and the finish here is so coarse that it is easier for the bacteria to adhere to the surface.”

This is what Hofmann is working to solve. Cleanability is his watchword. He wants the design of machines involved in hygiene-critical operations to facilitate easy and efficient cleaning.

Hoffman 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 specializes 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 of 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 Hoffman. “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.”

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 percent over the lifetime of the equipment by using hygienic design – particularly if there is a case of contamination, which can involve colossal costs,” he says.

Not all food products are equally sensitive. For example, beer is less critical than dairy products because alcohol kills pathogenic bacteria (however, this 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 center that conducts a cleanability test developed for the European Hygienic Engineering & Design Group (EHEDG). Trelleborg is a sponsoring member of this. The center runs a standardized contaminant through the part to be tested and through a reference pipe. A standardized cleaning process is subsequently performed using 1 percent 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.”

Trelleborg Sealing Solutions works closely with the University of Munich’s Department of Process Engineering and has focused research on sealing designs to meet Hofmann’s hygienic principles.

“We can recommend the optimum seal configurations for food, beverage and pharmaceutical processing,” says Burkhard Ledig, technical manager CPI Development Europe. “An example of developments in this field is the recently launched Turcon Variseal Ultra-Clean.”

Variseal is ideal for use in processing systems as it is compatible with virtually all chemical media, has superior wear resistance, unrivaled friction characteristics and can withstand extreme operating temperatures. PTFE, though, has no elasticity. This means that Turcon Variseal needs a spring fitted into the seal profile to energize it. The open spring created an area of dead space where bacteria could potentially be caught.

“We, therefore, focused on an alternative,” says Ledig. “The resulting Turcon Variseal Ultra-Clean is unique. The spring required to activate the seal is fully enclosed within a Turcon case. This for manufacturers of food, beverage and pharmaceutical products ensures there is no dead space within the seal, guaranteeing that bacteria cannot accumulate, avoiding the risk of contamination.”


This article was provided by Trelleborg Sealing Solutions. For more information, visit www.trelleborg.com.