Food & Beverages
We offer sealing solutions with the specific needs of the food and beverage markets at the forefront. Our food-grade products with FDA approved material are built with high-quality, safe materials that are designed to minimize process leakage, protecting products while they’re being made, and also reducing costly repairs and downtime. Featuring exceptional wear resistance, our food-grade gasket and sealing products also withstand extreme temperatures, aggressive materials and vigorous cleaning methods. Our vast product line has the entire packaging process covered, from beverage and food pumps to brewing and bottling pipes and fillers.
Key considerations for hygienic sealing in food & beverage processing
Food and beverage processing industries represent some of the most rigorous operating environments for sealing elements. Seals in these applications are frequently faced with temperature and pressure extremes, with no margin for error when it comes to long-term hygienic sealing performance. The impact of process media and chemicals used in cleaning and sterilization can also have a significant effect on seal lifetime and reliability. In food and beverage processing, hygiene is the most critically important factor above all else. Compromised sealing systems must be diagnosed and isolated quickly and efficiently before risk translates to the end consumers.
Steps can be taken to minimize any risk factors associated with the failure of hygienic sealing. Below article explores some of these steps in more detail, helping equipment operators, engineers and maintenance teams get more from their process lines and keep consumers safer.
What are the biggest sealing challenges around process contamination?
The purpose of elastomeric sealing elements in food & beverage processing equipment is to handle aggressive thermal and chemical conditions while ensuring that unwanted contaminants are not released into the process line. Some of the most significant threats to seal degradation are process media, clean-in-place (CIP) or sterilization-in-place (SIP) procedures, and faults with installation.
From oils and acids through to salts and sugars, a hygienic seal in a food or beverage process application needs to be able to withstand a diverse range of challenges with chemical compatibility. Continuous contact with the food or beverage product itself – or its constituent ingredients – can be a source of seal damage, and subsequent process contamination. Alongside the chemical nature of the process media, there may also be considerations on the temperature and pressure of the process lines. If an engineer has confidence in a sealing component to handle several different chemical challenges without damage or compromised sealing performance, the process lines can run uninterrupted for longer periods, improving productivity and efficiency.
Some types of seal material can be significantly damaged by the aggressive chemicals used in CIP and SIP cleaning procedures. While the use of these powerful chemicals is vitally important in killing sources of microbial contamination after process runs, the chemicals are at risk of clashing with the sealing components with irreparable damage to the structural integrity of the seal. The chemicals used in CIP attack many elastomeric seals, causing swelling, leaching, loss of mechanical strength, embrittlement and ultimately failure. The potential exists for fragments of the seal to break away into the process media.
Exposure to steam (typically 120°C to 135°C) in SIP causes many elastomers to soften and lose mechanical strength, extruding into the pipeline. This thinning of the gasket reduces the compressive load and potentially can result in leaks, as well as bug traps where the seal protrudes into the pipeline.
By taking the time to select a sealing material with the properties to resist the thermal and chemical demands of the cleaning method, the risk of seal failure and subsequent product contamination can be kept as low as possible.
Oversights during the original installation of the sealing component can impact the resilience of the seal, and cause proneness to damage. If the seal has been positioned inaccurately, or if the seal has been superficially damaged during installation – however imperceptibly – this leaves sealing weaknesses, which might be exposed through the thermal and chemical pressures of the application. A simpler sealing system, or more comprehensive training, can help to negate these effects.
Research has shown that short-term sealing problems mostly resulted from improper installation. For further information you can get in contact with Alfa Sealing, our dedicated experts with years of experience will support you with solutions that are specific to your application.
Standards & regulations
Standards are important for consistency in all industries, but for ensuring the safety of products intended for human consumption, it is imperative that every required guideline and certification is followed meticulously. Many industrial material grades are well suited to sealing oil, gas, seawater and other notably aggressive media, but would not be appropriate for the food or beverage processing industries. There are some key internationally recognized standards in place concerning leachable and potentially harmful constituents, which if not in place could put consumer health at risk.
The Food and Drug Administration (FDA) is the U.S. federal agency responsible for ensuring that foods and beverages are safe, wholesome and sanitary; human and veterinary drugs, biological products and medical devices are safe, and effective and cosmetics are safe.
CFR21.177.2600 describes the relevant regulations for “rubber articles intended for repeated use.” Paragraphs A – D detail the requirements for dry foods, paragraphs E and F detail the requirements for aqueous and fatty foods.
3-A Sanitary Standards Inc. is an organization in the United States that formulates sanitary standards and practices for the design, fabrication, installation and cleaning of equipment in the food and pharmaceutical process industries.
Standard 18-03 (“Multiple-Use Rubber and Rubber-Like Materials Used as Product Contact Surfaces in Dairy Equipment”) describes requirements for food quality materials that are suitable for steam sterilization, acid and alkali cleaning solutions and chlorine sanitizing agents.
European Parliamentary Council
The European Parliament has installed a series of regulatory guidelines concerning food contact materials, which apply across all European Union member states. The principle of the directive is that materials should be sufficiently inert to prevent transfer of substances into food in quantities that might be large enough to endanger human health.
Annex I of EC1935-2004 lists 17 groups of materials, which may be covered, including rubbers and silicones, while instructing on proper tracking and labeling systems for any food contact components. EC 2023/2006 concerns general good manufacturing practice for materials and articles intended to come into contact with food.
Materials approved for drinking water applications must satisfy the requirement of BS 6920 for the Water Regulations Advisory Scheme (WRAS).
The testing regime for WRAS approval is different than FDA testing, in that it tests the “Suitability of non-metallic products for use in contact with water intended for human consumption with regard to their effect on the quality of the water.” The test ensures sealing materials do not promote the propagation of bacteria or affect the color, appearance and taste of drinking water.
Importance of material choice
The choice of sealing materials for use in direct contact with the products has to be made carefully. The materials are required to fulfil multiple requirements. The seal material must comply with all applicable legal regulations and should at a minimum conform to FDA (Food and Drug Administration) CFR §177.2600, EG 1935/2004, and EU 2002/72/EG, depending on where the machinery is to be used. This ensures that no substances that are known to have negative effects on the product quality or the health of the consumers are used in the production of the seal’s raw material.
For example, for certain elastomeric mixtures, which must conform to the food and drug administration (FDA) CFR § 177.2600, only substances that are on an approved list defined by the FDA can be used. Then, the cured rubber has to pass extraction tests with water and vegetable oil, which represent aqueous or fat based products. For water, the extraction limit for the first seven hour test is 20 mg/inch2. Then, the specimen is exposed to the water for an additional two hours where the extraction should not exceed 2 mg/inch2. For hexane, the corresponding extraction limits are 175 mg/inch2 for the first seven hours and 4 mg/inch2 for the additional two hours.
The sealing material has to be resistant to all processed media. Therefore, an EPDM material would be best for use with aqueous media. High quality EPDM materials have proven to be resistant to acid and basic CIP cleaning agents, to withstand steam sterilisation of up to 180°C, and work in low fat-containing media at lower temperatures. With rising fat content and elevated temperatures limiting the use of EPDM materials, the use of FKM should be investigated as an alternative material. FKM shows fairly good properties in high fat contents, but often fails during the cleaning process when exposed to alkaline cleaning agents. If resistance to aqueous media, fat, and CIP/SIP cleaning agents is required, the best choice would be a special highly fluorinated FKM (Fluoroprene). These FKMs show excellent properties in all relevant media used in the food and beverage industry, even at temperatures of up to 200°C, without having the economical disadvantages of Perfluoroelastomers (FFKM).
A recent concern is the impact of flavouring agents on the sealing material. The problem is widely known in the beverage industry. For example, after the processing of orange lemonade, an extended rinse cycle is required before the filling line can be used again for processing pure water products. If the rinsing process is not done properly, flavouring agents like limonene will migrate from the seals and add consumer detectable taste impurities to the next production batch. Beverages with a higher content of flavouring agents, such as energy drinks, have an even stronger impact on seals. The flavouring agents have a strong impact on the sealing material, which leads to swelling of the seal’s material and mechanical weak – ening of the seal. Seal failure is only a matter of time. Highly fluorinated FKMs can be used in limited applications. Only FFKM materials will work as standard sealing materials in con – centrated flavouring agent-containing products.
Alfa Sealing offers one of the widest ranges of products and materials specific to the food and beverage processing sector. Together with you, our customer, we develop the optimum sealing solution for your application.
Basic design principles
For the design or choice of seals used in food and beverage equipments, there are some basic principles that should be followed. Due to hygienic design, a seal should fulfil the following requirements: the seal itself should have a clean and even surface without defects, the seal should be flush with the equipment’s components to prevent dead spaces and a metal stop ensures that the seal is not over or under compressed and that the joints are centred.
A large temperature range of the processing equipment can have a severe impact on the seal and the sealing function. At higher temperatures, the elastomer expands, which might lead to protrusion of the seal material into the equipment. This is critical in terms of dead space with respect to cleaning processes and the fact that product flow might tear off sealing material, which then contaminates the product. Upon cooling, the seal material will retract into the groove. This leads to free space in the groove, where product contamination and bacteria growth can occur.
Seals for food couplings and clamp connections are standardised products with which pipes for liquid media can be easily connected and sealed. Seals for food fittings have been standardised in accordance with DIN 11851 regulations. Their extraordinarily fast and uncomplicated installation of these clamps, thanks to the ease of separating them from the flange, has made them an extremely popular choice. Clamp connections, manu – factured per International Standards Organisation (ISO) 2852 (for inch measure – ments) and (DIN) 32676 (for metric measurements), are easy-to-install solutions as well. Both options are highly economical and easy to acquire.
However, since seals for food couplings have been designed without metallic stops, seal compression can vary once the seal is installed and gaps and dead spaces can appear. A similar problem arises with clamp connections, which also fail to provide consistent compression. Further, field experience has shown that major stresses can affect the seal landings, which can cause sealing material to shear off, con – taminating the product.
A good example of a standardised accepted solution to this problem is the aseptic clamp connection per DIN EN 11864 Part 3. The European Hygienic Engineering & Design Group (EHEDG) provided their expertise to avoid the problems associated with previous connection designs and develop a reliable hygienic solution. The result: two seals, one an O-ring that has already proven its effectiveness in practice, and one a moulded part for effectively connecting pipes with operating pressures of up to 40 bar. The metallic stop provides the seal with consistent compression, and a sufficient gap is created between the seal and the product space to allow rinsing during the cleaning processes. This gap also serves as space that can accommodate volume expansion due to exposure to heat or the influence of media without producing forces that can result in material shearing. To the left and right, the sealing surfaces are directly in contact with the product space, preventing product leakage and the corresponding risk of contamination
Special considerations for shaft sealing in food process equipment
Many food production processes depend heavily on large mixing and blending equipment. Applications are varied, from powder blenders for protein shakes to steam mixers for cooking ready meals. There is a huge range of rotary blade, plough and paddle mixers and blenders available to blend, dry, cook and homogenize.
The size of the plant and processing duties alter the magnitude of issues experienced but there are several typical issues that they have in common.
Unlike high-speed rotary pumps, which are typically well balanced with minimal shaft run-out, many mixing and blending process equipment types inherently suffer from run-out and eccentric shaft movement.
Furthermore, the length of the shaft means that span between the supporting bearings can often be significant – leading to shaft deflection.
Also, due to thermal cycling and subsequent thermal expansion and contraction during operation, the seal and bearing arrangement must be able to allow and compensate for this. The process media needn’t be heated for this to occur. The shearing motion of the mixing and blending process can create sufficient heat as to cause thermal expansion of the shaft.
These characteristics can be exacerbated with the addition of powders, solids, liquids and slurries creating additional torsional and shock loads on the shaft.
The use of shaft contact seals can further complicate matters, whereby the seal running surface is in contact with, and runs against the shaft, causing friction. The friction generated has several potentially detrimental effects, including:
- The seal can wear down the shaft, leading to shaft damage requiring expensive repair or replacement
- The seal contact face experiences wear, leading to seal failure and replacement
- Worn sealing materials can migrate into the process media, resulting in process contamination
- The frictional heat generated can damage the process media
Some solutions could involve the application of a wear sleeve to the shaft, using seals with a lower friction coefficient or adding a cooling lubricant to the seal area. However, these solutions can add layers of cost and complexity, and the use of cooling media is not always advisable in a hygienic production environment.
Particularly with larger mixers and blenders, seal maintenance and replacement can be challenging. The decoupling, removal and reassembly of the shaft, bearings and drive after takes valuable time and resources. Therefore, what can be done to optimize the performance of sealing solutions on food process shafts?
Select a seal that can handle shaft runout – Many seals can be compacted and deformed by eccentric shaft motion, creating a potential leak path. Some split mechanical shaft seals can allow up to 6 mm shaft runout as standard.
Take away the dynamic contact with the shaft to prevent friction and heating in the sealing area and wearing of the shaft. Choosing a dynamic face seal, in which the sealing face (the stator) remains static and a dynamic sealing face (the rotor) rotates with the shaft, can help to achieve this.
Simplify the seal repair and replacement process by choosing a split seal design requiring no major machine disassembly, saving time and resources and getting your process line operational much more quickly.