Hygenic Design
Use case
Hygienic Design (HD) is the essential prerequisite for the following aspects of food pro-duction, which are becoming increasingly important:
process and product safety
resource-efficient cleaning/production
increase in the degree of automation
Without consistent implementation of hygienic design principles, especially in areas close to or in contact with the product, it will not be possible to achieve these goals. If, for example, there are unsealed gaps or metal-to-metal contact points in these areas, or if spray shadow areas are difficult to reach, product residues can continuously pene-trate which will lead to microbiological problems in the long term. This not only en-dangers process, product and ultimately consumer safety, but also partially prevents fully automated food processing. This is mainly due to the fact that such geometries are simply not accessible by common spraying or rinsing systems. As a result, these areas have to be disassembled manually and cleaned separately. This not only requires qualified personnel, which is becoming increasingly difficult to obtain, but reproducibil-ity naturally suffers as well. Even if such non-cleanable surfaces represent the worst case, even less hygienic solutions have a massive impact on cleaning time and thus efficiency. With cleaning time accounting for an average of 10-20% of the total pro-duction time, we are talking about enormous savings potential. The aspects described at the beginning are gaining importance in the food industry at a dramatic rate and can thus also be transferred to the incipient change in the agricultur-al sector. Particularly in the context of the significant spread of farm-to-fork concepts, it is useful to consider the transfer and implementation of proven concepts for hygienic production in the agricultural sector at an early stage. Using the food industry as an example, the case study therefore aims to derive how the topic can best be opened up for the various stakeholders along the value chain and integrated into their own planning and/or design process.
Approach
Organisations and Guidelines
In the food industry, there are already several established organizations that offer an enormous range of guidelines for almost every conceivable area. This includes both design and planning guidelines for complete production environments, right down to hygienic screw connections. Examples include the European Hygienic Engineering and Design Group (EHEDG), Global Food Safety Initiative (GFSI) and 3A. Especially in Eu-rope, the EHEDG plays a major role in the food sector. It already has 55 comprehensive guidelines, which cover topics ranging from factory planning and design information to its own testing and certification procedures in the context of hygienic design. These associations thus address the entire value chain, i.e. operators of production facilities as well as machinery and plant manufacturers. The design fundamentals with regard to a hygienic production environment and construction methods can thus also be trans-ferred to the agricultural sector. Membership and thus access to the guidelines there-fore also seems worthwhile for stakeholders from the agricultural sector. In the follow-ing, the two primary phases of the hygienic design integration and development pro-cess will be examined using an example from the food industry.
Phase 1 – Constructive Design and Development Process
Phase 1 includes the planning/design or construction phase. As a general rule, good hygienic design always represents a target-oriented trade-off between function, safety and costs. A perfect, holistic implementation of hygienic design in the entire produc-tion environment is not technically feasible for anyone in terms of costs. The produc-tion and machinery area should therefore be divided into different safety/hazard zones or areas. A reasonable division is for example into direct, indirect or non-product con-tact surfaces. For more detailed information, please refer to the guidelines of the or-ganizations mentioned. If this is taken into account, Hygienic Design can be imple-mented in a targeted and cost-efficient manner and subsequently also leads to greater acceptance. It is crucial that companies consider hygienic concepts and hygienic design solutions at an early stage in the planning and design phase. In most cases, Hygienic Design can only be “installed” or created as a condition at a later date in a rudimentary and not very effective manner. Good hygienic design is always an inherent part of the machine design and must therefore be taken into account right from the start. The good thing about hygienic design is that it is relatively easy to verify by means of cleaning and cleanability tests. So if no clear preferred solution has emerged in the company’s design development process, the different variants can be checked by means of cleaning tests and a preferred solution can thus be determined. The open spray cleaning of machines and systems is a complex matter. Fluid-dynamic interactions, for example, which may lead to congestion zones with reduced cleaning performance, cannot always be esti-mated on the basis of experience by simply “looking at and thinking about it”. Validat-ing cleaning tests are therefore an enormously powerful tool for machine and plant manufacturers, which are offered by independent institutes. This case study is intended to illustrate a design development process with a holistic view of hygienic design aspects. The example used is a manufacturer of standard parts who has developed a new generation of a machine positioning foot. Relevant guide-lines of corresponding organizations were already consulted during the design process. At the end of the process, a further developed hygienic design version of the machine. foot was created, so that a complete series with different degrees of hy-gienic design implementation was available for the subsequent hygienic design evaluation.
2.3 Phase 2 – Cleanability Tests
Phase 2 should be an elementary part of every development process. As already de-scribed in 2.2, some fluid dynamic effects, which sometimes drastically impair cleaning, cannot be definitively evaluated and estimated on the basis of experience, especially as the complexity of the components increases. Thus, components that are supposedly hygienically designed may nevertheless have areas that are difficult to clean. This is where industry-oriented, comparative cleaning tests can help, which work with a typi-cal cleaning regime (nozzle type, nozzle spacing, chemistry, etc.) as used by the indus-try. The cleaning regime is usually designed to be relatively mild, since the cleaning tests must of course primarily demonstrate the hygienic design through easy cleanabil-ity. With sufficient chemicals and cleaning time, all components will eventually be more or less clean. An aggressive cleaning regime would not be very suitable in terms of demonstrating hygienic design. The variants shown in Fig. 2-1 have now been subjected to such comparative cleaning tests. The cleaning process can be recorded time and spatially resolved using inline contamination sensors based on the fluorescence method.
In principle, any customer- and process-specific test soiling can be used for the cleaning tests. In this way, realistic test conditions can be created, since the cleaning behavior of a wide variety of product categories differs, sometimes dramatically. From the analyzed image data of the inline contamination sensor, a quantifiable cleaning process can be derived, as shown in Fig. 2-3. A clearly faster cleaning of the Hygienic Design machine foot is recognizable, which leads in this case to approximately 28% faster cleaning. This also quantifiably highlights the advantages of Hygienic Design components and makes them easier to communicate to customers. Hygienic Design components have higher purchase costs, but these are usually quickly recouped through higher cleaning efficiency.
In addition, combined cleaning and penetration tests can also be used to check the tightness of sealing points, because only with sufficiently high pressure is a truly hy-gienic component produced under these conditions. Fig. 2-4 shows the comparison of a pure metal-to-metal contact point (minimal gap between set screw and shaft) versus a solution with an elastomer seal. The machine foot with partial hygienic design im-plementation (bottom) and the machine foot constructed in full hygienic design (top) are shown. It can be clearly seen that the seal of the Hygienic Design variant has withstood the cleaning conditions and that no contamination or tracer particles have penetrated into the interior. Without the seal, even a very small metal-to-metal gap allows large amounts of contamination into zones that are then inaccessible for cleaning. Microbio-logically problematic sources of contamination can develop here and endanger the process and product and ultimately the consumer.
Standardization needs and Lessons learned
In summary, Hygienic Design evaluation needs to become a standardized and crucial part of the constructive design and development process. If this is not considered from the beginning, it is usually not easy to retrofit or adapt afterwards, as a good and effi-cient Hygienic Design is an inherent part of the machine or component designs. Espe-cially in the agricultural sector, there is still a lot of room for improvement when it comes to implementing hygienic design solutions. Since one usually does not work directly on the end product and further processing steps (e.g. peeling/washing process-es, etc.) follow, there is a perceived lower level of requirements with regard to hygienic storage and processing conditions. However, since problems can easily propagate here and the equipment must also be cleaned/maintained at some point either way, the implementation of Hygienic Design is also worthwhile for efficiency reasons alone. The cleaning effort is reduced and, as already described in Chapter 1, this is also the neces-sary basis for any automation efforts as cleaning is a crucial part of the production process in total. Finally, it is advisable to strive for Hygienic Design certification of the developed com-ponents and assemblies, which is offered by some organizations (as independent bod-ies). The generally easy cleanability has then been proven and certified by means of design evaluation (based on CAD and drawing data) in combination with defined test procedures. This enables buyers to see at a glance whether the component meets im-portant hygienic design requirements and increases sales potential.