Sealing in food and beverage applications is extremely challenging. Seals must not only withstand extreme temperatures, steam and wear in dynamic situations, but they must also meet regulatory requirements and be compatible with different types of foods and ingredients, such as fats, oils and acids. Furthermore, hygienic design, resistance to aggressive cleaning regimes and prevention of flavor residues are top priorities.
This article discusses sealing materials used in food and beverage processing applications, use cases for each, and common factors that can affect sealing performance, equipment uptime, and food and beverage product performance. , as well as the benefits of working with an experienced seal manufacturer to ensure the sealing solution best meets application requirements.
Sealing materials used in food and beverage applications
One of the keys to extending the life of seals used in food and beverage applications is to match the material to the processing system or processing system in which it is used. Seals must be resistant to processed foods and drinks, as well as chemicals used in cleaning regimes, often at high temperatures.
One of the most commonly used materials for o-rings and seals in food and beverage processing is ethylene propylene diene rubber (EPDM), a fully saturated non-polar hydrocarbon elastomer. Its polymer geometry provides superior compatibility with polar fluids, even at elevated temperatures. EPDM demonstrates high chemical resistance, is suitable for use with alkaline and acidic cleaning products, and is an excellent choice in most dairy applications except high-fat products. Its typical applications are filling, dispensing, pumps, pipe and flange seals, valves and quick connectors.
For applications using animal and vegetable fats and oils, acrylonitrile butadiene rubber (NBR) is a good choice when O-rings will not be exposed to harsh cleaning regimes, ozone or superheated steam. NBR is a copolymer of butadiene and acrylonitrile and the percentage of these in the NBR formulation determines the performance characteristics of the material.
Fluoroelastomer materials (FKM) are optimized for steam environments in the food and beverage industry. They demonstrate good suitability for use in contact with vegetable oils and fats, animal fats and high-fat dairy products. They also have good resistance to ozone and aging.
The gold standard for elastomer sealing, perfluoroelastomer (FFKM) is more expensive than other sealing materials but is compatible with virtually all fluids. It is ideal for extremely aggressive processes and cleaning regimes where seals can deteriorate very quickly. Although more expensive, FFKM seals can extend scheduled maintenance and therefore substantially reduce total cost of ownership.
Silicone materials are ideal for use in food and beverage manufacturing due to their inherent inertness to the growth of bacteria, mold and fungi. Silicone has excellent heat resistance, cold flexibility and dielectric properties and is the preferred choice in applications exposed to ozone and oxygen. Injection molded silicone components lend themselves to complex geometries that offer product designers more options, especially when combined with metals and plastics using multicomponent technology. Multicomponent technology allows multiple parts of an assembly to be combined into a single component, avoiding dead spaces where bacteria can grow.
Polytetrafluoroethylene (PTFE) seals offer a broader range of services than elastomeric seals with regard to temperature, pressure, dynamic sealing against the moving surface on shafts and the wide variety of fluids the seals encounter. PTFE is an inert material which makes it resistant to almost all chemicals and acids. In particular, it demonstrates exceptional low-friction characteristics, minimizing wear. This makes it ideal for dynamic applications such as mixers or block pumps.
Because PTFE has limited elasticity, PTFE seals are often energized with an elastomer o-ring or spring. In food and beverage applications, the elastomer must be compatible with the process and cleaning medium. Springs can, depending on their position within a processing system, be encapsulated to avoid dead spaces.
Plastic-based engineering materials such as polyetheretherketone (PEEK) and ultra-high molecular weight polyethylene (UHMWPE) are ideal for reciprocating and oscillating equipment that requires high wear resistance and may encounter abrasive media and supporting surfaces. These materials are ideal for a variety of food processing applications such as fillers, valves, pumps, mixers, separators, homogenizers, centrifuges, metering cylinders and sensors.
Seal service life extension
Selecting the correct seal material for the application is critical to ensuring seal life and extending the period between scheduled maintenance. Sealing failure can lead to potential contamination or even line breaks. Therefore, materials, whether elastomers or plastics, must handle a wide variety of food types, as well as clean-in-place (CIP) and sterilize-in-place (SIP) processes.
CIP and SIP automated processes are currently the best methods for cleaning computer systems. They guarantee safety and efficiency, prevent microbiological contamination of food and minimize recontamination of process equipment. However, harsh chemicals used in cleaning products can quickly cause serious damage to elastomeric seals, especially in high load and pressure applications. With high temperatures and steam sterilization, which now typically reaches 302°F, this deterioration is intensified.
When specifying seals, it is important to recognize the sealing conditions within the processing environment and select specialty seals that are tested and proven to be compatible with the system's operating parameters.
Combining sealing material with food or beverage ingredients and cleaning chemicals can maximize the time between scheduled maintenance and production yield. By detailing the specific requirements of a transformer, specialist seal manufacturers can propose cost-effective solutions that meet all major standards and are proven to withstand cleaning regimes, however rigorous.
Improved friction characteristics
Elastomers have a high coefficient of friction, which means they tend to stick to each other during automated assembly or to mating surfaces when inserted into a housing. Coating technology improves the friction characteristics of elastomer seals, increases wear resistance and reduces insertion forces.
For food and beverage processes, the coating must meet the same regulations and standards as the seal. It is also essential that the coating does not deteriorate or peel away from the joint. Specialized alternative treatments that improve friction characteristics avoid this problem.
Hygienic design
Seals, gaskets and rough surfaces of piping and equipment are potential havens for bacteria and create hygiene challenges for the food and beverage processing industry. The solution is hygienic design. Close collaboration between the food and beverage equipment manufacturer and seal supplier is required during the initial design phase to ensure hygienic design options are maximized. One of the best ways to achieve a hygienic design is to use multi-component technology, where multiple parts are combined into a single component to eliminate dead space. Working with experts in this area requires a holistic engineering approach that looks not just at the seal, but also at its housing and its counterparts.
An unpleasant situation
Flavor transfer, a vexing problem in food and beverage processing, has become even more challenging due to the beverage industry's trend toward increasingly intense flavors. Drinks with a high concentration of aromas naturally tend to leave noticeable traces of aroma in the bottling lines. Despite cleaning measures and adequate production plans, small traces of flavor may remain in the bottling machines, which can be absorbed by the next drink.
The elastomeric materials used in the sealing components of filling machines that come into contact with beverages have proven to be a significant factor. Flavors used in beverages, especially if used in high concentrations, diffuse into elastomeric materials. Seals can therefore release absorbed aromas even after thorough rinsing between beverage filling processes. The consequences of flavor transfer are useless transitions from one product to another, product waste, unintentional downtime, additional inspections and complaints.
Study topic
Beverage bottling specialist Krones worked with Trelleborg Sealing Solutions to analyze the reasons behind unintentional flavor transfer during the filling process. Companies have found that elastomer sealing components are a significant factor in flavor incorporation. They determined that selecting the ideal sealing material is critical to preventing flavor transfer from one filling process to another.
They also demonstrated that FKM and FFKM materials demonstrate effectiveness in preventing flavor and aroma transfer. FFKM materials do not absorb flavors and have virtually no detectable effect on the taste of subsequent beverages, even under unfavorable conditions. This makes these sealing materials ideal for use on bottling lines that process intensely flavored beverages. Analysis of the sealing materials showed that flavor absorption was greater for FPDM compared to FKM materials, which demonstrated significantly better performance, making it suitable for use with many beverages.
Sealed to standards
In addition to addressing the many factors that affect processing equipment, sealing materials must also meet regulatory requirements for food contact materials. These regulations are especially important for food and beverage equipment manufacturers who sell their products globally. In particular, the requirements of the international food industry are in focus. They include the well-established EU regulations on food contact and the US Food and Drug Administration (FDA) regulations, as well as the recent certification of Chinese food regulations on the Chinese food equipment market.
Looking to the future
More than ever, companies are looking to increase the security of their machines and applications, while also aiming to reduce maintenance and the cost of unexpected downtime. Numerous sensing solutions, along with the Internet of Things (IoT), are becoming cost-effective solutions in advanced seal management and enable remote device monitoring and data collection.
Because seals are often critical components in computing systems, artificial intelligence (AI) can offer real benefits to manufacturers. From sensor selection to data analysis, seal manufacturers can collaborate with equipment manufacturers to develop predictive failure models, create system health dashboards, and improve system operation.
Conclusion
Sealing solutions are essential to the performance of processing equipment and can have a significant impact on the commercial success of food and beverage products. Partnering with an experienced seal manufacturer can help ensure that the best seal material and design is selected to address the various factors that affect the performance of processing equipment, including the chemicals the seals come into contact with, the mechanical properties, CIP and SIP regimes, flavor entrainment, hygiene design and the need to comply with industry standards and regulations.
