Effective processing is vital to ensure our food and drink is safe and palatable. This includes selecting the right sealing material for the application. Not only must seals stand up to extreme temperatures, steam and wear in dynamic situations, but they also need to be compatible with the processing of a broad variety of food types and ingredients, such as fats, oils and acids.
The sealing environment within food and beverage processing is one of the most demanding, and incorrect seal specification and seal failure can lead to potential contamination or line stoppages resulting in costly unscheduled delays.
Materials, whether elastomer or plastics, must withstand cleaning in place (CIP) and sterilization in place (SIP) regimes that can quickly destroy incorrectly specified seals. Regulation compliance, hygienic design, resistance to aggressive cleaning regimes and avoidance of flavor carryover are top priorities.
Compliance with food contact regulations is a necessity. Selecting the right material for the processing environment is critical, as is ensuring chosen materials comply with multiple regulations and industry standards around the globe, including:
- U.S. Food and Drug Administration (FDA) regulations
- European Food Contact Regulations including Reg. (EC) 1935/2004
- Chinese food safety standards
- Japanese Positive List released in 2020
- 3-A Sanitary Standards
- NSF International Standards
The challenge of flavor carryover
A major challenge in beverage processing is flavor carryover, which can occur, for example, when bottling water after the use of equipment to process a flavored energy drink. A trend for increasingly intense flavors makes this issue even more challenging.
Beverages with high concentrations of flavors naturally tend to leave perceptible traces of aroma in bottling lines. Despite cleaning measures and adapted production plans, small traces of aroma can remain in bottling machines, which are then absorbed by the next beverage.
The elastomer materials used in filling machine sealing components that come into contact with beverages have proven to be a significant factor. The aromas used for beverages, especially when used in high concentrations, diffuse into elastomer materials. The seals can then release the absorbed aromas even after thorough rinsing between beverage filling processes.
The consequences of flavor carryover are wasteful transitions from one product to another, product rejects, unintentional downtime, additional inspections and complaints. The solution lies in selecting the right specifically developed material to avoid the flavor carryover issue.
Multicomponent design for improved hygiene
Gaskets, seals and rough pipe and equipment surfaces are potential bacteria havens and create hygienic challenges for the food and beverage processing industry. Prevention of this is achieved through hygienic design.
Close collaboration between the food and beverage equipment manufacturer and the seal supplier during the initial design stage will ensure maximization of hygienic design options. One of the best ways to achieve hygienic design is by utilizing multicomponent technology, in which multiple separate elements that are assembled together can instead be manufactured as a single component to eradicate dead space where bacteria can grow.
Multicomponent-designed seals and components can include plastic-to-rubber, rubber-to-plastic and rubber-to-metal in a variety of geometries that ensure a solid bond.
A focus on eliminating the need for secondary component assembly is important to achieve a higher integrity product. Working with experts in this field requires a holistic engineering approach that not only looks at the seal but also its housing and counterparts.
Selecting the right material
Matching the seal material to the processing system is key to prolonging the life of seals in food and beverage applications. The seals must be resistant to the foods and beverages being processed, as well as the chemicals used in cleaning regimes, often at elevated temperatures.
One of the most common materials for O-Rings and gaskets in food and beverage processing is Ethylene Propylene Diene Rubber (EPDM), a fully saturated, non-polar hydrocarbon-based elastomer. Its polymer geometry gives it superior compatibility with polar fluids even at elevated temperatures. EPDM demonstrates high chemical resistance, is suited for use with alkaline and acidic cleaners, and is an excellent choice in most dairy applications — except for products with high fat content. Its typical applications are filling, dispensing, pumps, pipe and flange gaskets, valves and quick connectors.
For applications using animal and vegetable fats and oils, Acrylonitrile-Butadiene Rubber (NBR) is a good choice for O-Rings not 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 (FKM) materials are optimized for steam environments in the food and beverage industry. They demonstrate good suitability for use in contact with vegetable oil and fat, animal fat and high-fat dairy products. They also have good resistance to ozone and aging. Specially formulated high-performance FKM seals address the challenge of flavor carryover, preventing the release of flavor molecules, which can migrate into the material and be released and absorbed by beverages in subsequent filling processes.
The gold standard for elastomer sealing, Perfluoroelastomer (FFKM) is more expensive than other sealing materials but is compatible with virtually all media. It can withstand extremely aggressive CIP and SIP regimes in which seals can deteriorate very quickly. FFKM seals can reduce unscheduled downtime, extend planned maintenance and, therefore, lower the total cost of ownership substantially.
Silicone materials are ideal for use in food and beverage production due to their inherent inertness to growth of bacteria, mold and fungi. Silicone has excellent heat resistance, cold flexibility and dielectric properties. It 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, as previously discussed.
Polytetrafluoroethylene (PTFE) seals offer a wider service range than elastomeric seals when it comes to temperature, pressure, dynamic sealing against moving surfaces in shafts and the vast array of media that seals encounter. An inert material, PTFE is resistant to many different cleaning solutions, including caustics, acids and disinfectants. In particular, it demonstrates outstanding low-friction characteristics, minimizing wear. This makes it ideal for dynamic applications such as mixers or dosing pumps.
As PTFE has limited elasticity, an elastomer O-Ring or a spring usually energizes PTFE seals. In food and beverage applications, the elastomer must be compatible with process and cleaning media. Encapsulated springs can, depending on their position within a processing system, avoid dead space.
Engineered plastic-based materials, such as Polyether Ether Ketone (PEEK) and Ultra High Molecular Weight Polyethylene (UHMWPE), are suitable for reciprocating, slow rotating and oscillating equipment that requires high wear-resistance and may encounter abrasive media and countersurfaces. These materials are ideal for a variety of food processing applications, such as filling machines, valves, pumps, mixers, separators, homogenizers, centrifuges, dosage cylinders and sensors, and are also suitable with ceramic surfaces.
Extending seal life
Selecting the right seal material for the application is critical to ensure achievement of optimum seal life, extend the period between planned maintenance and prevent unwanted downtime. Seal failure can also lead to potential contamination or even line stoppages. Therefore, materials, whether elastomers or plastics, must cope with a broad variety of food types, as well CIP and SIP processes.
Automated CIP and SIP processes are currently the best methods for cleaning processing systems. They ensure safety and efficiency, prevent microbiological contamination of food and minimize recontamination of process equipment. However, aggressive chemicals used during cleaning can rapidly cause severe damage to elastomeric seals, especially in applications with load and pressures. High temperatures and steam sterilization, which is now commonly up to +150°C, intensify this deterioration.
When specifying seals, it is therefore important to recognize the sealing conditions within the processing environment and to select specialty seals that are tested and proven to be compatible with the system’s operating parameters.
Matching the seal material to the food or beverage ingredients and the cleaning chemicals can maximize the interval between planned maintenance and production yield. With the details of a processor’s specific requirements, specialized seal manufacturers can propose cost-effective solutions that are compliant with all major standards and proven to stand up to cleaning regimes, however stringent.
Improving friction characteristics
Elastomers have a high coefficient of friction, meaning they tend to stick either to each other during automated assembly or to mating surfaces when inserted into a housing. Coating technology improves the friction characteristics of elastomer seals, enhances wear resistance and lowers insertion forces.
For food and beverage processes, the coating must meet the same regulations and standards as the seal. It is also critical that the coating does not deteriorate and flake off the seal. Specialized alternative treatments that improve friction characteristics avoid this issue.
Looking to the future
More than ever, companies are looking to increase the safety of their machines and applications, while at the same time aiming to reduce maintenance and the cost of unexpected downtime. Numerous sensing solutions, coupled with the Internet of Things (IoT), are becoming economically viable solutions in advanced seal management and allow for the remote monitoring of devices and data collection.
As seals are often critical components within processing systems, artificial intelligence (AI) can offer real benefits to manufacturers. From sensor selection to data analytics, seal manufacturers can collaborate with equipment manufacturers to develop predictive failure models, build system health dashboards and increase system efficiencies.
Selecting the right sealing solution and material for the application is critical to the performance of processing equipment and can significantly impact the commercial success of food and beverage products. Partnering with an experienced seal manufacturer can help ensure the best sealing material and design is chosen for the application in order to address the many factors impacting processing equipment performance, including CIP and SIP regimes, chemicals compatibility, mechanical properties, aroma carryover, hygienic design and the need to comply with a wide range of industry standards and regulations.
David Kaley has more than 20 years of experience working with food and beverage manufacturers, supporting them to solve their equipment challenges. At Trelleborg Sealing Solutions, Kaley is the business development manager for the Americas, and is responsible for helping customers.
Trelleborg Sealing Solutions