Guide: Understanding the Principles of Hygienic Design
The design principles and ratings used when developing systems for harsh production environments
Hygienic design is one of the most important aspects of good product inspection equipment, particularly when that equipment is designed for quality inspection in the food industry. It is important to understand the fundamental philosophies and requirements that go into this design in order to know what questions to ask - and what to look for - when choosing a system for use in a hygienic environment.
This guide covers the various factors that go into the hygienic design of METTLER TOLEDO product inspection equipment, including:
- IP rating
- NEMA rating
- Material used in construction
- Accessibility
- System geometry
Choosing a product inspection equipment provider is an important decision, and choosing a provider who knows the principles of hygienic design is always the right call. Learn more about hygienic design principles in this guide.
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What is a hygienic environment in food production, and how is it maintained?
Many production environments have an expectation of cleanliness that exist to protect consumers from the spread of harmful bacteria and disease, or to guard against allergens. For example, an environment manufacturing a gluten-free food would have similar elements of hygienic design as a dairy production environment protecting against listeria contamination.
Some hygienic environments manage this by keeping areas separated into clean rooms, or by strict control of entry into an area. Other hygienic environments involve aggressive washdown routines using high-pressure rinsing and caustic detergents. Generally, these routines involve rinsing the production environment, cleaning the system to remove soil, rinsing the system down again, sanitizing the system to reduce microbial contaminants to acceptable levels and then rinsing the system off again if the sanitizing agent does not need to remain on the system surface.
Food production often involves these harsher cleaning regimens, particularly in the meat and dairy production segments where microbial contamination can have disastrous consequences for consumers. It is no surprise, then, that regulations such as the Food Safety Modernization Act include guidance to help manufacturers develop regular cleaning routines to minimize the risk of bacterial infection (as well as produce comprehensive documentation of their cleaning process, of course). This includes dividing production areas and equipment into low risk and high-risk zones. This guide is concerned with high-risk zones and equipment, where more thorough cleaning routines are required.
Naturally, these cleaning routines require systems and equipment able to stand up to high-pressure washdown and caustic detergents – equipment manufacturers refer to such systems as being washdown capable. This is, however, where the problem comes in. Every manufacturer may have their own definition of what "washdown capable" means – their own sets of priorities based on their own internal risk assessments or based on the industries in which they operate. The purpose of this guide is to provide you with the tools to evaluate the washdown capabilities of a given piece of production equipment.
What is an overview of considerations for making washdown-ready production equipment?
When considering the construction of a system for a washdown environment, there are three basic things which need to be taken into consideration: Ingress protection for electrical or mechanical devices, the materials used in construction, and the design considerations of the system itself from a hygienic standpoint.
The factors that should be considered for any system designed for use in a hygienic environment are:
- The materials used in construction
- The way in which the system is constructed
- Surface finishes
- Ease of assembly/disassembly
Each of these considerations comes with their own set of standards, but the ones this guide is primarily concerned with are the standards for ingress protection for electrical enclosures. The most commonly used standard (or at least the most well-known one outside of manufacturing) is the Ingress Protection rating, or IP rating.
How is an IP rating determined?
What is a NEMA rating?
While the Ingress Protection rating is the most well-known, it is far from the only standard that exists. The National Electrical Manufacturers Association (NEMA) has a similar set of standards for electrical enclosures, but with far more focus on environmental hazards above and beyond water and dust. In terms of washdown, the ratings which commonly come into play are the NEMA 4 and NEMA 4X ratings. NEMA 4 indicates that an enclosure is watertight, while NEMA 4X enclosures must be resistant to corrosive elements as well as watertight.
For a washdown routine which would be found in a hygienic production environment, systems should be NEMA 4X as it maps most closely to an IP66 rating. It is important to note, however, that NEMA ratings are best used in concert with an IP rating, as the requirements for the two standards do not map directly to one another. IP ratings are solely concerned with protection against dust and water, whereas NEMA takes environmental suitability into account; ratings indicate whether the materials are resistant to corrosion, whether the enclosure can contain an explosion, and other features of the design such as thickness of material.
What design considerations apart from IP rating go into hygienic design?
The IP rating of a system is an important factor to consider when discussing washdown capabilities – but IP ratings are just one part of the bigger picture. Industries which require washdown – food production in particular – have far more factors to consider than the level of protection against water and foreign object intrusion. It is not enough that production equipment stands up to a washdown routine, it needs to be designed in such a way as to make performing that routine easy. Any time wasted struggling with a piece of equipment to get it clean is lost efficiency (and by extension, lost profit).
Thus, the design considerations for a system which touts itself as being washdown-capable should reflect the desire to make the cleaning process as easy as possible. There are, of course, a large number of standards that manufacturers refer to when designing a system for use in hygienic environments, both in terms of the construction and materials, but a complete discussion of these standards is beyond the scope of this guide. Two standards to look at, particularly from the standpoint of food production, are the ANSI standard 3A 14159-3-2019 and ISO 14159:2008. These deal with the design of mechanical conveyors used in meat and poultry production and hygiene requirements for design of machinery in general, respectively, and the primary resource METTLER TOLEDO utilizes when considering hygienic design.
How does component accessibility factor into hygienic design?
Some elements of a given piece of equipment will need to be removed in order to be cleaned more effectively – like a conveyor belt, for example. This takes time, but that time can be reduced with a system that makes it easy to remove parts. In the case of a conveyor belt, belts could even be rotated out to spend more time cleaning them without having to pause production.
"Easily accessible" also refers to the surface of the equipment in general. An open frame design makes it easier to reach every part of the system that contacts the product and thoroughly clean it. An open frame also makes it far easier to clean or retrieve any product that has spilled on the floor; on a system where this is not the case, it gives bacteria, mold or other contaminants a place to cultivate out-of-sight.
How does system geometry influence hygienic design?
The concept of an open frame design leads to another, broader point: the shape of the frame and enclosure is also crucial for washdown capable production equipment. From a material standpoint, the structure needs to be made of material that is resistant to corrosion and nonporous. Stainless steel is the most cost-effective option in this case, as it is smooth, nonporous, nonreactive, nontoxic and durable – ideal for equipment that is meant to function in a washdown environment.
This also applies to the way in which the equipment is assembled. Weld points on the frame need to be smoothed and finished in order to discourage accumulation of dirt and other materials at welding point. When and wherever possible, surfaces should be angled – using rounded supports for the frame, for example – in order to discourage accumulation of solid and liquid materials. The same care needs to be taken when placing the Human Machine Interface (HMI) for the equipment – consideration as to whether or not the HMI can be cleaned in the same manner as the rest of the equipment, or whether it needs to be covered or removed from the production area during cleaning, for example, are important questions that require an answer. Ideally, the HMI would have the same IP rating as the rest of the equipment; this makes the cleaning process faster and easier by eliminating the need to cover or move the HMI during the process.
What questions should I ask when buying washdown capable equipment?
Every manufacturer has their own definition of what constitutes "suitable for washdown." When asking for details about how a manufacturer quantifies washdown suitability, the first move should be to find the IP rating of the system, followed by the evaluation of the system geometry.
Ask questions about the system such as:
- Have they made an attempt to incorporate angled surfaces?
- Does the HMI have the same IP rating as the rest of the system?
- How much of the system is in direct contact with the floor?
Pay attention to how a provider speaks about their washdown systems – if they only give the IP rating and do not go into further detail, it may be because they do not consider anything beyond the ability of the system to stand up to caustic detergents and high-pressure water important.
METTLER TOLEDO has long worked to develop equipment that not only stands up to the rigors of a strict cleaning routine but makes execution of that cleaning routine as efficient and easy as possible through the design of the system itself. Our washdown line of checkweighers is built with this philosophy in mind. They feature open frames, easily removable conveyor belts, and a rounded frame with sloped surfaces to prevent liquid collection and discourage bacterial growth. Combined with an IP69 certified rating also applicable for the HMI, resistance to high pressure cleaning and most caustic detergents, the washdown checkweighers are a prime example of a system designed for washdown environments. Importantly, washdown checkweighers from METTLER TOLEDO do not sacrifice their accuracy. They are MID certified and have over 150 customization options including numerous product handling features for increased product stability supporting additional accuracy.