Seals for the Food Industry: Materials, Cleaning and Operational Continuity
In food industry plants, a seal must maintain its sealing performance in an environment where operating conditions can change repeatedly throughout the day. Contact with the product, temperature variations, detergents, disinfectants, water, steam, cleaning cycles and production periods expose the material to different types of stress.
Selection therefore cannot be limited to identifying an elastomer generically described as “food grade”.
When the seal may come into contact with the product, the requirements applicable to materials and articles intended to come into contact with food must also be considered. At the same time, documentary compliance alone does not guarantee that the component is suitable for the temperature, cleaning products, groove geometry or cycle frequency.
For Tecnonext, the selection of sealing solutions for the food industry begins precisely with this combination of conditions: process, use, application compatibility, cleaning and long-term stability.
A seal in a food processing plant does not operate under a single condition
During production, a seal may come into contact with products containing water, fats, oils, sugars, salts or other substances typical of the process.
Once production has ended, the same component may be exposed to completely different conditions during cleaning.
Temperature may increase, the product is replaced by detergent or disinfectant solutions, and the seal may be subjected to repeated heating and cooling cycles.
At least two environments must therefore be considered:
the process condition and the cleaning condition.
A material compatible with the food product may in fact react differently to a concentrated detergent or to the temperatures used during the cleaning cycle.
Selection must therefore be based on the most demanding combination of conditions that the component will actually encounter.
A material suitable for food contact and a material
suitable for the application are not the same thing
When a seal is intended for food contact, verifying regulatory requirements is essential.
Within the European Union, Regulation (EC) No 1935/2004 establishes the general framework for materials and articles intended to come into contact with food. Under normal or foreseeable conditions of use, these materials must not transfer components to food in quantities that could endanger human health, cause unacceptable changes in the composition of the food or cause deterioration in its organoleptic characteristics.
Regulation (EC) No 2023/2006 also governs good manufacturing practice for materials intended to come into contact with food.
This regulatory framework must, however, be distinguished from the technical assessment of the application.
A compound may have the documentation required for a specific food application and, at the same time, not be the most suitable choice for a particular temperature, a specific detergent or a groove subjected to demanding mechanical cycles.
The question must therefore be considered from two perspectives:
does the material meet the applicable food-contact requirements?
and, at the same time:
can it maintain its characteristics under the actual operating conditions of the plant?
In the food industry, compliance must be assessed case by case
Referring generically to a “food grade material” can be misleading.
The European framework for food-contact materials includes harmonised general legislation, but not every material family is covered by a specific European measure. The European Commission clarifies that, where no specific EU measures exist, national provisions may also apply.
This is particularly important for rubber and elastomers.
Consequently, documentation, composition, intended use, target market, food product, temperature and contact duration must be assessed in relation to the specific application.
Tecnonext, for example, indicates the possibility of supplying O-Rings according to requirements and certifications intended for the food industry or drinking-water applications, including MOCA and other specific references.
Selecting an elastomer family and automatically considering it suitable for every food application is therefore not sufficient.
Compound selection starts with the product and the process
EPDM, FKM, silicone, NBR and other elastomers can be used in different industrial environments, but the material family alone is not enough to determine whether a seal is suitable.
Compound formulation, additives, hardness and applicable specifications can significantly affect component behaviour.
For this reason, selection requires knowledge of both the product with which the seal will come into contact and the expected operating conditions.
A predominantly water-based process has different requirements from an application involving fats or oils. Likewise, a line operating at moderate temperatures may require different characteristics from a system subjected to frequent thermal treatments.
The objective is not to identify the highest-performing material in absolute terms, but the one that provides the most appropriate balance between compatibility, temperature, cleanability, mechanical performance and expected service life.
Cleaning cycles can be more demanding than production
One of the most important aspects of food-industry applications is that the most critical phase for the seal does not necessarily coincide with production.
During cleaning, the material may be exposed to higher temperatures, rapid temperature changes, alkaline or acidic detergents and disinfectants.
The duration and frequency of the cycle also play an important role.
A component that comes into contact with a given solution for a few minutes once a month is not subjected to the same stress as a seal cleaned several times a day.
Chemical compatibility must therefore be assessed by considering:
the product used, concentration, temperature, contact time and number of cycles.
Nominal compatibility with the detergent alone does not necessarily describe how the material will behave after hundreds or thousands of cleaning cycles.
CIP and frequent cleaning: repetition changes the problem
In plants equipped with CIP – Cleaning in Place systems, cleaning is carried out without completely dismantling the equipment.
This makes it even more important for seals, grooves and surfaces to be compatible with the intended cleaning process.
EHEDG provides specific guidelines both for the hygienic design of CIP systems and for elastomeric seals used in food processing equipment. Guideline 48 on elastomeric seals considers, among other factors, material, compression, hardness, ageing, temperature, thermal cycling, pressure, contact media and possible failure modes.
The issue is therefore not simply whether the seal can withstand a single cleaning cycle.
The seal must retain sufficiently stable characteristics after repeated cycles over time.
Temperature and thermal cycles affect service life
The transition between production, cleaning and restart can generate frequent temperature variations.
The elastomer expands and contracts, while the metal components of the groove also undergo dimensional changes. If the materials respond differently to temperature, the actual compression of the seal may vary during the cycle.
At higher temperatures, ageing and permanent deformation may also increase.
At lower temperatures, some elastomers may instead become stiffer and temporarily reduce their ability to conform to surfaces.
EHEDG specifically highlights temperature, ageing, thermal expansion and thermal cycling as relevant factors in the design and analysis of elastomeric seals for food applications.
For this reason, checking only the maximum temperature specified for the material is not enough.
The entire operating cycle must be considered.
Swelling, shrinkage and changes in hardness
Repeated contact with the product, detergents and other fluids can progressively change the properties of an elastomer.
Phenomena to be evaluated include:
swelling;
shrinkage;
increases or decreases in hardness;
loss of elasticity;
permanent deformation;
cracking or surface deterioration.
Excessive swelling can increase pressure inside the groove or alter friction in dynamic applications.
Shrinkage, on the other hand, can reduce contact with the surfaces and create conditions that favour leakage.
Changes in hardness can also alter the behaviour of the seal during operation.
The final effect always depends on the combination of material, fluid, temperature and exposure time.
The groove must also be designed for cleanability
In the food industry, seal geometry is not only about containing a fluid.
It is also important to avoid configurations that are difficult to clean or create spaces in which residues can accumulate.
EHEDG emphasises that seals in contact with the product must be designed and used in accordance with material specifications; wear, corrosion, degradation, shrinkage and swelling can in fact alter the hygienic integrity of the seal over time.
Guideline 48 also addresses the relationship between the seal and the contact surface, considering aspects such as compression, groove fill, alignment and the prevention of gaps.
A suitable compound installed in an unsuitable groove can therefore still represent a critical point.
Compression and permanent deformation affect continuity
The seal must maintain sufficient contact pressure throughout the entire operating cycle.
If the elastomer develops a high compression set, it may progressively lose its ability to recover its original shape after prolonged compression.
In a food processing plant, this phenomenon may be promoted by the interaction between time, temperature and repeated cycles.
A seal may therefore still appear intact while no longer exerting the same force against the surfaces.
When leakage appears only after a certain number of production and cleaning cycles, permanent deformation is one of the factors that should be considered together with chemical compatibility, groove geometry and thermal conditions.
Hygiene and operational continuity are connected
A deteriorated seal does not only represent a potential leakage problem.
In food processing systems, changes in geometry or surface condition can also make hygienic management of the sealing point more difficult.
For this reason, maintenance and replacement should not be based exclusively on the presence of visible leakage.
EHEDG itself highlights that the hygienic integrity of seals can change over time due to wear, degradation, shrinkage and swelling, and therefore requires a maintenance programme consistent with operating experience or qualification testing.
From a production perspective, a seal that maintains more stable performance can also help reduce unexpected interventions and unplanned replacements.
Operational continuity therefore also depends on the ability to understand and anticipate how the component will behave over time.
When a seal is replaced too frequently
Replacement frequency can itself become useful technical information.
If a seal has to be systematically replaced after a certain number of cycles, this does not necessarily mean that the issue is simply a normal consequence of use.
It may be useful to determine whether deterioration occurs mainly during production or after cleaning, whether the material changes hardness, increases in volume, loses elasticity or shows damage concentrated in specific areas.
Comparing failure intervals can also provide useful information.
If different components show the same issue after similar periods, the analysis should focus on the conditions of the system rather than only on the individual seal.
This approach is consistent with problem solving applied more generally to sealing failures: replacing a component with an identical one does not necessarily eliminate the technical cause of the problem.
A “more resistant” seal is not automatically a better solution
When a seal has a short service life, one of the most common reactions is to look for a material considered to offer higher performance.
Switching to a compound with greater thermal or chemical resistance may be appropriate, but only if it addresses the actual cause of deterioration.
A more expensive material may be unnecessary if the problem originates from groove geometry.
A harder compound may change sealing behaviour without resolving an incompatibility with the detergent.
Likewise, a material with excellent chemical resistance may not be the best solution if the main issue concerns friction, movement or deformation.
The comparison must therefore start from the observed failure mode.
The role of hygienic design
In machinery intended for food production, the seal forms part of a system that must be capable of being cleaned effectively.
The latest EHEDG guidelines on hygienic design principles reaffirm that inadequate design makes equipment more difficult to clean and that design, construction and installation must be considered with contamination prevention in mind.
For seals, this means evaluating the following factors together:
material, surface, groove, compression, cleanability and operating conditions.
The aim is therefore not to add a hygiene requirement to a seal that has already been selected, but to include cleanability among the selection criteria from the outset.
O-Rings, custom-designed seals and specific solutions
The requirements of a food processing plant can vary considerably depending on the installation point.
In some applications, a correctly selected standard O-Ring is sufficient. In others, particular geometries, available space or process conditions may require a custom-designed seal.
For the food industry, Tecnonext supplies O-Rings, custom-designed seals, LSR components, die-cut and punched parts, and other product families selected or developed according to the application.
Custom-designed seals intended for food applications are evaluated by considering materials, geometries, finishes, cleaning requirements and long-term durability.
Here too, a special geometry only makes sense when it addresses a genuine technical requirement.
What information is required to select a seal for food applications
A request formulated simply as “we need a food-grade seal” leaves too many variables unresolved.
To select a suitable solution, it is useful to know the product or fluid in contact with the seal, production temperatures, any pressure involved, the type of movement and the groove configuration.
The cleaning cycles must then be described: detergents and disinfectants used, concentrations, temperature, duration and frequency.
Finally, the documentary requirements for the application and the destination market must be defined.
This information makes it possible to evaluate compliance, compatibility and service life together.
Tecnonext’s approach to food-industry applications
Tecnonext supports food-industry companies, machine manufacturers and plant engineers in selecting seals and sealing components for processes where reliability,
compatibility and operational continuity must be considered together.
The analysis begins with actual operating conditions: product in contact, required materials, temperature, pressure, movement, groove geometry, cleaning frequency, detergents used and expected service life.
Where necessary, the documentary requirements applicable to food contact are also evaluated.
The objective is not to identify a generic “food-grade seal”, but to select a solution consistent with the production process, cleaning procedures, applicable requirements and long-term behaviour.
Visit the dedicated page: Food Industry | Tecnonext
For a technical assessment or the selection of a seal for a food processing plant, contact Tecnonext:
035 059 0010
Via Rudello, 11, 24067 Sarnico BG
FAQ – Seals for the food industry
Is there one best material for food-industry seals?
No. The material must be selected according to the product in contact, temperature, detergents, disinfectants, pressure, movement and expected service life. The applicable food-contact requirements must also be verified.
Does a seal compliant for food contact automatically withstand cleaning cycles?
No. Food-contact compliance and compatibility with cleaning conditions are separate aspects. Detergent, concentration, temperature, duration and cycle frequency must be evaluated separately.
Why can a seal deteriorate particularly during CIP?
CIP cycles can combine temperature, chemicals and repeated thermal variations. These conditions can change the hardness, volume, elasticity and long-term behaviour of the material.
What should be checked if a seal is replaced frequently?
It is useful to assess the form of the damage, when it occurs, compatibility with the product and detergents, temperature, cleaning cycles, compression set, groove geometry and surface conditions.
Is European legislation the same for all food-contact materials?
There is a general European framework, particularly Regulation (EC) No 1935/2004 and the GMP requirements of Regulation (EC) No 2023/2006. However, not all materials are covered by a specific harmonised EU measure; where such measures do not exist, national provisions may also be relevant.
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