FFKM O-rings in Cleaning Machines

Application of FFKM O-rings in cleaning machines

• Perfluoroelastomers (FFKM) are a class of synthetic rubber materials characterized by a high fluorine content that provides exceptional inertness and excellent resistance to degradation. Their fully fluorinated structure gives them enhanced thermal, oxidative and chemical stability that exceeds that of other fluorinated polymers, such as fluoroelastomers (FKM). This high level of fluorination is the defining characteristic of FFKM as a high-performance material for demanding sealing applications. The enhanced features of FFKM make it particularly well suited for environments where standard elastomers would fail prematurely due to harsh conditions.

• FFKM O-Rings are recognized as the highest performing O-Rings, designed for critical applications where continued uptime and reliability under extreme conditions justifies their cost. These seals are used in a wide variety of industries that need to handle severe chemical exposure and high temperatures, including aerospace, chemical processing, pharmaceuticals, oil and gas, and semiconductor manufacturing. In these areas, FFKM O-Rings are critical to the reliable operation of pumps, valves, mechanical seals, reactors, and other important equipment, and seal failure could result in serious operational interruptions, safety hazards, or product contamination. FFKM materials are sold under a variety of trade names, such as Kalrez®, Chemraz®, PERFREZ®, and Simriz®, indicating that while the basic material composition is consistent, different manufacturers offer specialized formulations tailored to meet the specific requirements of different industrial applications. This shows that when considering FFKM, it is important to look beyond the general material classification and evaluate the specific properties of the available compounds.

• Cleaning machines, especially those designed for industrial and sanitary environments, often encounter a wide variety of aggressive cleaning agents. These include strong acids, bases, and strong oxidizers, which are essential for effective disinfection and removal of stubborn residues. In addition, many cleaning procedures involve high temperatures, such as hot water rinses or steam sterilization (CIP/SIP), which can cause seals made of standard elastomeric materials to degrade and fail. In these situations, the need for reliable and durable seals is critical. Leakage of aggressive cleaning chemicals poses a safety risk and compromises the integrity of the cleaning process, while frequent seal failures can result in costly downtime for maintenance and repairs. Therefore, the unique combination of chemical and thermal challenges presented by cleaning machine applications makes investigation of the suitability of FFKM O-rings particularly important.

2. Material properties of FFKM

FFKM stands out for its excellent resistance to a wide range of chemicals. It resists attack by more than 1,800 different chemicals, solvents, and plasmas. This near-universal chemical resistance includes the ability to remain stable when exposed to highly corrosive substances such as concentrated nitric acid, sodium hydroxide, ethylenediamine, and steam, which often degrade other elastomeric materials. In general, FFKM is highly resistant to oxygenated organic compounds (aliphatic and aromatic hydrocarbons), chlorinated solvents, as well as strong acids and bases, high-temperature steam, and water. This broad compatibility stems from its fully fluorinated structure, which provides a high degree of inertness. However, it is worth noting that certain FFKM grades can be specially formulated to enhance resistance to specific chemicals (such as amines or hot organic acids), indicating that material selection should be aligned with the specific chemical environment of the application.

In terms of thermal stability, FFKM O-Rings are able to withstand continuous operating temperatures from -15°C (5°F) to over 300°C (572°F). Some special formulations can even withstand temperatures as high as 327°C (620°F) or 340°C (644°F). This exceptional thermal stability is primarily due to the strong intermolecular forces created by the high fluorine content and the strong carbon-fluorine bonds that form the backbone of the polymer chain. Certain FFKM grades are specially designed to maintain sealing performance even after prolonged exposure to high-temperature steam, a key requirement for sterilization-in-place (SIP) processes often used in hygienic cleaning applications. The ability to reliably operate over such a wide temperature range, including the high temperatures used in many industrial cleaning procedures, highlights a key advantage of FFKM.

From a mechanical properties perspective, FFKM materials generally have good tensile strength (usually in the 15-20 MPa range) and a high elastic modulus, which enables them to effectively withstand pressure and maintain a secure seal. They also have excellent resistance to compression set, which means they can maintain their original shape and sealing force even after being compressed for a long time. This property is critical to ensuring the long-term performance of O-rings in sealing applications that are constantly under pressure. However, a significant limitation of FFKM is that it generally has poor wear resistance. This can pose a challenge in dynamic sealing applications where there is significant friction between the O-ring and other surfaces, or abrasive particles may be present in the process fluid.

In addition to its chemical, thermal, and mechanical properties, FFKM has several other properties that make it suitable for demanding applications. Its low permeability to gases makes it a viable choice for equipment that requires a hermetic seal, such as certain specialized cleaning machines or vacuum systems. FFKM also has low outgassing and extraction levels, a particularly important property for industries such as pharmaceuticals and semiconductors, which must maintain a clean environment and may use cleaning machines in these sensitive areas. In addition, FFKM has good hermeticity, excellent weathering and aging stability, and very good resistance to oxygen and ozone, all of which contribute to its long-term reliability under a wide range of operating conditions. Its non-flammability in air also improves safety in environments where flammable materials may be present.

3. Advantages of FFKM O-rings in cleaning machines

• The excellent chemical resistance of FFKM O-Rings is a major advantage when used in cleaning machines. These machines often use a wide variety of cleaning agents, from mild detergents to highly corrosive chemicals, and FFKM's broad compatibility ensures that the seals can withstand extended exposure without degradation. This includes resistance to strong acids such as hydrochloric and sulfuric acids, strong bases such as sodium and potassium hydroxide, and strong oxidizing agents such as hydrogen peroxide and peracetic acid, which are common in industrial and sanitary cleaning solutions. This resistance prevents swelling, cracking, or other forms of chemical attack that can cause seal failure and leakage.

• Many industrial and sanitary cleaning processes require high temperatures for effective cleaning or sterilization. FFKM O-Rings excel in these environments due to their excellent thermal stability. They can reliably operate at temperatures significantly higher than standard elastomers can withstand, making them suitable for steam sterilization (SIP) procedures, which can reach temperatures of 260°C (500°F) or higher, depending on the specific FFKM compound. This capability ensures that the seal maintains integrity and prevents leakage even during high-temperature cleaning cycles, facilitating more thorough and reliable cleaning processes.

• FFKM's superior resistance to chemical degradation and high temperatures directly results in longer life for O-rings in cleaning machines. Unlike seals made from less resistant materials, which may require frequent replacement due to chemical attack or thermal decomposition, FFKM O-rings maintain their sealing properties over time. This extended service life reduces maintenance frequency, lowers seal replacement costs and minimizes downtime of cleaning equipment, ultimately improving the overall efficiency and cost-effectiveness of cleaning operations.

• In highly regulated industries such as food and beverage or pharmaceuticals, using the right materials in cleaning equipment is critical. Certain grades of FFKM are specially formulated to comply with industry standards such as FDA (Food and Drug Administration) regulations and USP Class VI (United States Pharmacopeia) certification, as well as 3A sanitary standards. This compliance ensures that cleaning machines using these FFKM O-rings meet the safety and sanitation standards required by these strictly regulated industries, thereby ensuring product purity and consumer safety.

4. Disadvantages and limitations of FFKM O-rings

• One of the most significant disadvantages of FFKM O-Rings is their high cost. They are typically the most expensive elastomeric sealing solution, often costing significantly more than standard materials such as FKM, EPDM and Nitrile. This high price tag often limits their use to applications where superior performance characteristics are absolutely necessary and the cost can be justified by the critical nature of the sealing application, or where significant savings can be achieved in extremely demanding environments through reduced downtime and maintenance.
• FFKM generally performs poorly at very low temperatures compared to some other elastomers. While certain specialized FFKM compounds have been developed to improve flexibility at low temperatures, the general low temperature performance of standard FFKM grades is not a major advantage. This can be a limitation for clean machines that are operated or stored in extremely cold environments, as FFKM O-rings may become brittle or lose the ability to seal effectively below their typical operating range.
• Another significant limitation of FFKM is its poor wear resistance. In applications where the O-ring is subject to significant friction from moving parts or where abrasive particles are present in the cleaning media, FFKM seals may wear faster than more wear-resistant materials. This is a particularly important consideration for dynamic seals in cleaning machines that involve reciprocating or rotary motion, or where the cleaning process involves abrasive slurries or particulate matter.
• Although FFKM is known for its broad chemical resistance, it can swell significantly when exposed to certain highly fluorinated solvents. If the machine's cleaning process involves the use of these specific fluorinated solvents, the potential for this incompatibility needs to be carefully evaluated to avoid seal failure due to excessive swelling.
• Finally, FFKM may exhibit lower mechanical strength in some areas, such as tensile strength or tear resistance, than some other high-performance elastomers. While generally good mechanical properties, this may be a factor in applications involving unusually high pressures or significant mechanical stresses on seals within clean machines.

5. Comparison with other O-ring materials used in cleaning machines

• Viton (FKM) offers excellent chemical and temperature resistance, with a typical operating temperature range of -15°C to 205°C (5°F to 401°F). It is generally more cost-effective than FFKM, making it a popular choice for a variety of industrial sealing needs. However, Viton's chemical resistance is not as comprehensive as FFKM, especially with respect to strong bases, ketones, and certain aggressive cleaning agents that may be used in specialized cleaning machines. Therefore, while Viton can be a suitable choice for many cleaning applications, it may not be as durable as FFKM in the harshest chemical environments.

• EPDM is widely regarded for its excellent resistance to water, steam, ozone, and weathering, and its typical operating temperature range is -50°C to 150°C (-58°F to 302°F). It also exhibits good resistance to certain dilute acids, ketones, and bases, which makes it suitable for certain cleaning processes. A significant advantage of EPDM is its lower cost compared to FFKM, which makes it an attractive alternative for budget-conscious applications. However, EPDM is not recommended for use with oils, fuels, and non-polar solvents, as these solvents may be encountered in certain industrial cleaning scenarios. In addition, it has lower temperature limits compared to FFKM, limiting its use in high-temperature cleaning or sterilization processes.

• Nitrile rubber (NBR), also known as Buna-N, is a widely used and affordable elastomer known for its good oil and fuel resistance and a typical temperature range of -40°C to 120°C (-40°F to 248°F). However, nitrile rubber has limited resistance to ozone, sunlight, weathering, and many solvents, acids, and bases commonly found in cleaning agents. While it is the most cost-effective choice of these materials, its chemical limitations generally make it unsuitable for most industrial and sanitary cleaning machines that use aggressive cleaning solutions.

Table 1: Comparison of O-ring materials for cleaning machines Refers

6. Potential failure modes of O-rings in cleaning machines and how FFKM can mitigate these failures

• Chemical degradation is a significant concern for O-Rings in cleaning machines due to the wide variety of cleaning agents and their often corrosive nature. This can manifest as swelling, shrinking, hardening or cracking of the seal material, ultimately leading to failure. FFKM's nearly universal chemical resistance effectively prevents this failure mode as it is inert to most chemicals encountered during cleaning, significantly reducing the risk of degradation compared to other elastomers.

• Thermal degradation is another potential problem in cleaning machines using hot water or steam, and involves the O-Ring becoming hard and brittle due to exposure to excessive temperatures. FFKM's high thermal stability enables it to withstand these high temperatures without losing elasticity or structural integrity, reducing the risk of thermal degradation and ensuring reliable sealing even during high temperature cleaning cycles.

• Compression set is the permanent deformation of an O-Ring when it is under compression, which can lead to a loss of sealing force over time. FFKM exhibits excellent resistance to compression set even in the presence of high temperatures and chemicals, allowing it to maintain its sealing ability over a longer period of time and reduce the frequency of replacement due to such failures.

• Extrusion and galling occur when high pressure forces an O-ring into the gap between mating parts, causing damage. While FFKM's inherent strength helps resist this, selecting an FFKM compound with the appropriate hardness for the cleaning machine pressure requirements and proper gland design are critical to preventing extrusion failures.

• Galling, i.e. wear of O-rings due to friction, is a potential failure mode in dynamic seals or cleaning machines handling abrasive media. This remains a limitation as FFKMs are generally less wear resistant. In applications where heavy wear is expected, alternative seal materials or designs may be required for specific parts of the cleaning machine.

7. Selection criteria for FFKM O-rings in cleaning machines

• When selecting FFKM O-Rings for clean machines, a thorough evaluation of the chemical environment is critical. All cleaning agents, process fluids, and lubricants to which the O-Ring will be exposed must be identified. Contact us for a TDS to ensure the selected compound is suitable for the specific concentrations and operating temperatures of all of these substances. The duration and frequency of exposure should also be considered.
• The entire operating temperature range must be accurately determined, including any temperature peaks during cleaning or sterilization. A FFKM grade should be selected that can withstand the entire temperature range with sufficient safety margins.
• The maximum pressure at which the O-ring will need to seal during washer operation must be determined. The appropriate hardness (durometer) of the FFKM should be selected to prevent extrusion at this operating pressure, and the use of backup rings should be considered for very high pressure applications.
• The type of application, whether static or dynamic, will influence the selection criteria. For dynamic seals, the potential for wear should be evaluated and if it is severe, alternative materials may need to be considered for these particular seals, as FFKM generally has poorer wear resistance.
• Finally, ensure that the O-ring dimensions (ID and cross-sectional area) match the gland dimensions per relevant standards such as AS568 or ISO 3601. If the cleaner is used in regulated industries such as food and beverage or pharmaceutical, verify that the selected FFKM grade meets all necessary compliance requirements (e.g., FDA, NSF).

8. Similar industry cases and applications

• The pharmaceutical and biotech industries use FFKM O-rings extensively in their equipment due to the material's excellent resistance to harsh chemicals used during sterilization and production, as well as its high purity and low outgassing properties. FFKM seals are critical in Water for Injection (WFI) systems and Sterilization-in-Place (SIP) clean equipment to ensure seal integrity in harsh conditions and maintain the sterile environment necessary for drug manufacturing.

• In the food and beverage processing industry, FFKM O-rings that meet FDA and 3A sanitary standards are widely used in equipment that requires frequent and rigorous cleaning. These seals can withstand the harsh chemicals and high temperatures involved in the cleaning-in-place (CIP) procedures, ensuring the hygiene and safety of food and beverage production. They are used in pumps, valves, mixers and filling machines, playing a vital role in maintaining product quality and preventing contamination.

• The chemical processing industry relies heavily on FFKM O-rings for their ability to resist a wide range of aggressive chemicals, including strong acids, bases, and solvents. These seals are critical for reactors, pumps, and valves that come in direct contact with aggressive chemicals, ensuring safe and reliable operation. FFKM seals are also used in heavy-duty cleaning processes within chemical plants, highlighting their suitability for harsh chemical environments.

9. Cleaning and maintenance of FFKM O-rings

• While FFKM is highly resistant, proper cleaning and maintenance are essential to maximize its service life and ensure optimal performance of your cleaning machine. Regular cleaning helps remove any accumulated residue or contaminants that may affect seal integrity or system cleanliness. Cleaning methods that use a mild, non-abrasive soap solution or wipe with isopropyl alcohol are generally recommended. For more stubborn residues, ultrasonic cleaning with a compatible solution can be used. Please contact us in advance if cleaning and maintenance are a problem.

• It is also vital to inspect FFKM O-rings regularly. O-rings should be checked for signs of wear, chemical attack (such as swelling or discoloration), or physical damage (such as cracks, cuts, or abrasions). Using adequate lighting and a magnifying glass will aid in a thorough inspection. Any changes in the elasticity or dimensions of the O-ring should also be noted, as they may indicate material degradation.

• Proper storage of FFKM O-Rings is important to prevent premature degradation. They should be stored in a cool, dry, and clean environment away from direct sunlight, sources of ozone, and incompatible chemicals. Keeping them in their original packaging and avoiding storage under tension or compression will help maintain their integrity until they are needed.

10. Conclusion

• FFKM O-Rings are the sealing solution of choice for clean machines operating in harsh chemical and thermal environments. Their excellent resistance to a wide range of aggressive cleaning agents and their ability to perform reliably at elevated temperatures, including steam sterilization, make them an excellent choice for demanding applications. While the initial cost of FFKM O-Rings is higher than other elastomers, their extended service life and potential for reduced maintenance and downtime can provide significant long-term cost benefits, especially in critical cleaning processes where seal failure can have serious consequences.
• FFKM O-Rings offer compelling advantages for clean machine applications where seal reliability and service life are critical, particularly in industries with stringent hygiene requirements or where aggressive cleaning chemicals and high temperatures are used. However, the appropriate FFKM grade must be carefully selected based on a thorough analysis of the specific chemicals, temperatures and pressures involved to maximize performance and ensure compatibility.

You can contact us as it is usually a custom size.

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