Ensuring Operational Hygiene

Open areas are part and parcel of processing and packaging. So the danger of contamination by foreign bodies, cleaning agents, or microorganisms is a constant threat. As HMIs (Human Interface Devices) are used on or near machines, their hygienic design is essential. Europe has a very high quality standard based on several regulations.

Regulatory requirements

The standards for HMIs in food-and-beverage production are very specific. For instance, the DIN EN 1672-2 (Hygienic Design) standard set by the German Institute for Standardization maintains that the product area, spray area and non-product area all impact the HMI; and therefore, must be properly considered in the hygiene equation. While the HMI is not specifically part of the product area, it still must meet all conditions of that area as stipulated by the rules of the EHEDG (European Hygienic Engineering & Design Group). The EHEDG states that surfaces which come directly into contact with the product and components which could indirectly contaminate the product must satisfy the stricter regulation.

According to the Food and Hygiene Act put into effect by the EU, objects and equipment which come into contact with food and beverage must be made in such a way that they can be cleaned, maintained, and disinfected without any negative influence on the product. They must also be installed in the immediate vicinity so they can be reasonably cleaned. Likewise, guideline 98/37/EWG regulates the hygiene requirements for food-processing machines. It asserts that machines must be designed and built to exclude the danger of infection, illness or contagion, and so that they can be cleaned prior to use.

These requirements are numerous and may not be fulfilled by devices meant for general industrial applications. So some manufacturers have been forced to resort to auxiliary solutions or to improvise their own constructions. For instance, HMIs have been incorrectly installed in separate spaces or covered with cleaning hoods (a strategy with significant drawbacks, since microorganisms can easily settle into hollow spaces). So Siemens developed the SIMATIC HMI—sector-specific panels and panel PCs for the food-and-beverage industry. Based on standard hardware, it can be used at the machine level.

Hygiene-oriented design

Since consumer sensitivity to food quality is at an all-time high, there is this need for more hygiene-oriented components. Here are a few factors that you should consider when choosing a HMI. First, pick one that easy to clean and robust enough to tolerate being handled roughly. (Remember that chain-mail gloves, for instance, are often worn during meat processing.) And chemicals and disinfecting agents may erode aluminum. Look instead for one constructed from stainless steel. A finished surface can also prevent the adhesion of dirt and microorganisms.

Second, find a HMI that can handle rough ambient conditions like the high humidity and changing temperatures found in the everyday environment of the food-processing industry. Look for certified seals. Make certain that liquids can quickly run off the HMI’s frame. Pick a surface that is completely smooth, without grooves or gaps; this ensures it is easy to clean and does not house microorganisms from the outset.

Thirdly, consider a HMI that has IP 66 or IP 66k protection. This means that it can withstand higher-pressure water jets up to 10 bars. Careful cleaning can take up to 25 percent of the production time. (Following pre-cleaning, the components are sprayed with foam or gel, which is then washed off after a soaking period with low-pressure or high-pressure cleaners. A clear rinse follows.)

Fit for validation

There is also the issue of traceability. In the food-processing industry, EU guideline 178/2002 of January 2005 requires complete traceability for foodstuffs—from input and output materials and products all the way to the grocer's shelves.

Siemens supplemented its Simatic HMI with a scalable HMI software called Simatic WinCC flexible, in an effort to create a first step towards a uniform software platform for all HMI tasks. During processing, it records all GMP-relevant (Good Manufacturing Practice) changes. With option “Audit” electronic signature it is easy to attribute the responsibility of a recipe change or the correct production of a batch to a specific person. Therefore, it is possible to automatically record the full and complete history of a plant. In addition, a higher-order PC for editing FDA-relevant data in the audit trail can be omitted in many plants.