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Hygienic load cells - frequently asked questions

21 June 2016

Founded in 1950, HBM has been manufacturing test and measurement equipment for over 60 years now and has built up expert knowledge in all areas of this field. Here, we take the time out to answer some of the more frequently asked questions that we have received recently on hygienic load cells and food production – questions that you may well be familiar with!

Founded in 1989, the European Hygienic Engineering and Design Group (EHEDG) is made up of a consortium of manufacturers, food producers, research institutes and public health authorities.  With a principle aim to promote hygiene during the processing and packing of food products, the EHEDG mission is clearly defined as:

“EHEDG enables safe food production by providing guidance as an authority on hygienic engineering and design”.  

Replacing the focus of reactive hygiene measures after processing, for example by the application of heat, or the control of oxygen and carbon dioxide concentrations, and the removal of the nutrients needed for microbial growth, a visible shift towards preventative measures has now become common practise within the food and pharmaceutical production and packaging arena.

Setting aside the actual surfaces that are used in the food production process, these measures are relevant to all systems and components, such as weighing systems used in filling and packaging systems, which are commonly used in the production process.  As systems and components are often used in areas where contamination or cross contamination is highly probably due to the direct or indirect contact with other products, the requirements for a hygienic weighing system design are particularly strict according to the guidelines set out by the EHEDG.

Up until recently, the development of load cells has been clearly focused on meeting the technical specifications such as quality and precision.  However as load cells continue to be used in environments which demand a higher level of hygiene, such as the pharmaceutical and food industry, the design of equipment is an important aspect in terms of it being easy to clean.

In order to comply with EHEDG guidelines and to avoid potential contamination, the housing of a load cell would be made completely of stainless steel alloy 1.4404 in accordance with AIS131L, which meets the requirements for corrosion resistance, mechanical stability and non-toxicity of components in contact with this product.

In addition to this, the material used must also demonstrate particularly high corrosion resistance, even in the case of exposure to solutions containing chloride, dependent on concentration and temperature.  Lastly, the complete housing should have smooth, stainless steel surfaces that are non-absorbent and free from imperfection such as grooves and gaps, to avoid gathering, and an even surface structure with low surface roughness of less than 1µ, which is necessary to provide optimum cleaning.

Other features which also need to be considered when developing a hygienic load cell include:

• Welded joints – the micro-plasma welding process used should produce clean, smooth, welded joints with no roughness on which dirt may collect or become engrained.  This would ensure the welded joints do not impair cleaning.
• Rounded corners – all corners should be rounded and not feature sharp edges.  The adjustment chamber, for example, should be welded at the corners to ensure that sharp edges are avoided.
• Self draining – there should be no horizontal surfaces on any part of the housing.  The upper section of the housing should have an inclined surface to enable water to flow freely away.  The adjustment chamber should also be rounded to prevent water from remaining on the surface.

Setting aside the obvious advantages of component cleaning to one side, there are also numerous other advantages to implementing a hygienically designed system namely, the ability to keep up with continuously tightening standards and also, the ability to create a product with greater quality and purity.  And, not least, Hygiene has become a competitive factor.  Clever developments, combined with hygienic systems, means that businesses can now gain greater productivity due to the reduced cleaning times required. 

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