Cherry
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2 min read
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Dec 13, 2024
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Combination oil seals have come to the forefront of sealing components due to their durability and longevity. It is often used to seal agricultural machinery such as tractors. (Honglei(KDIK) shows you various COMBI oil seals and await in your inquiry.)
An oil seal consisting of two or more loose parts can be called a combination oil seal. Most common and simple combination oil seals are made of steel and oil resistant rubber. The two loose parts can complement or work together to make the most of the material’s own characteristics and improve sealing efficiency.
1. The COMBI oil seal consists of a common oil seal and a secondary seal, which mainly prevents the entry of external contaminants.
2. The COMBI oil seal has a spring at the lip of the seal.
3. COMBI oil seals have a dustproof lip.
4. COMBI oil seals are mainly used in environments with high contamination.
5. When subjected to large rotational or translational movements, it is preferable to use it instead of a cassette type combination seal.
6. COMBI oil seals have the distinctive features of combination oil seals: long life and resistance to wear.
7. COMBI oil seals are optimised in terms of the position of the sealing lips and dust lips, and are particularly resistant to contaminant ingress.
8. COMBI oil seals are often used in the driving part of moving parts of agricultural and industrial machinery.
Xingtai Honglei Seal Manufacturing Co., Ltd. registered trademark “KDIK” is senior manufacturer for global markets. We are professional oil seals factory with more than 18 years experience. Our main product lines include kinds of Automobile oil seal, Agricultural & Construction machinery oil seal, Precision Rubber Parts, O-rings and so on. Besides, we accept customer’s own designs and OEM design orders, always focus on Top quality products with competitive price and best service.
Modify: Mar. 22, 2024
Oil seal is the customary name of general seals, which is simply the seal of lubricating oil. It is used to seal grease (oil is a common liquid substance in the transmission system, also refers to the general meaning of liquid substances) mechanical components, it will drive parts in need of lubrication and output parts of isolation, so as not to let lubricant leakage. Static and dynamic seals (general reciprocating motion) are called oil seals with seals. The representative form of oil seal is TC oil seal, which is a double lip oil seal with self-tightening spring completely covered by rubber. Generally speaking, oil seal often refers to this TC skeleton oil seal.
Common materials for oil seals are: Nitrile rubber (NBR), fluorine rubber(FKM), silicone rubber, acrylic rubber, polyurethane, polytetrafluoroethylene and so on.
It has good heat resistance, wear resistance, resistance to various lubricants, greases, oil and gas mixtures, suitable for temperature - 30 - 120 degrees Celsius, but can no longer be used in phosphate hydraulic oil and gear oil containing extreme pressure additives, stable performance in gasoline and mineral oil with low aniline point.
Excellent oil and heat resistance, abrasion resistance, ozone resistance, ultraviolet radiation resistance, especially extreme pressure fluid containing lubricants, gear oil, motor oil, oil series hydraulic oil, etc., suitable for - 30 - 150 degrees Celsius range of work.
Aging resistance, heat resistance, oil resistance, almost applicable to all lubricants, fuel oils, gasoline, oil containing extreme pressure additives is not easy to harden, but cold resistance, high temperature wear resistance is poor, compression deformation is large, suitable for temperature - 20 ~ 250 degrees Celsius.
It has outstanding resistance to high and low temperatures, can be used at 150 degrees Celsius for a long time without performance change, can be used at 200 degrees Celsius for 10,000 hours continuously, and can maintain its unique use flexibility, ozone resistance and weather resistance in the operating temperature range of - 70-260.
It has outstanding chemical stability, thermal stability, friction reduction and self-lubrication. Its pyrolysis temperature is over 400. Therefore, it can work normally in the temperature range of - 200 - 300 degrees Celsius. Except for free fluorine and alkali metals, it has excellent corrosion resistance to chemicals, solvents, hydroxides and acids.
Nitrile butadiene rubber (NBR) and fluorine rubber (FBR) are widely used oil seals. The former has low cost, but its temperature resistance and sealing performance have been improved obviously, but the cost is higher, and it still has some bad common characteristics of ordinary rubber materials, such as poor wear resistance, short service life, especially sensitive to the eccentricity of the shaft, etc. Leakage phenomenon is still widespread. PTFE oil seal is a product with high technology content, which is the direction of oil seal development in the future.
Attention:
When choosing the material of oil seal, the compatibility of material to working medium, the adaptability to working temperature range and the ability of lip edge to follow the rotating axis at high speed must be considered. Generally, the temperature of lip edge is higher than that of working medium at 20-50 C. Attention should be paid to the selection of oil seal materials. The working range of oil seals is related to the materials used in oil seals: NBR, ACM, FPM and NBR.
Anywhere you look on the farm you will find seals of different designs. The purpose of any seal is to keep a fluid or semi-fluid such as grease from leaking out and equally as important, foreign material from entering.
Goto xtnbk to know more.
The ability to isolate the component from external influences is just as imperative and possibly in some uses more so, than keeping the fluid inside.
This needs to be understood since most of us only consider a seal failed when there are visible signs of leakage.
A seal employed in a vacuum pump if weakened will introduce dirt and decrease the pump’s operation and useful life without any visible signs.
Many vacuum planters fall prey to a degraded seal that will impact the unit’s performance in the field since dust is highly abrasive.
Though commonly identified as a lip seal, it also goes by the name rotary or shaft seal. On an engine you will find lip seals in use at the front and rear of the crankshaft (one-piece rear main seal), in hydraulic pumps such as for the power steering, in a water pump and other areas.
On a vehicle or machine lip seals are used on the wheel bearings, drive axle bearings, transmission, air conditioner compressor, to name a few.
A lip seal is employed when there is a need to isolate two sides of a component within a rotating member.
Up until around the 1930s leather seals were common but since then lip seals have replaced that style. They have added reliability and improved protection from internal and external leakage.
The lip seal works by having an edge that rides on the rotating part while allowing a film of the fluid to reside between the lip and the shaft.
The confluence of the fluid film and the sealing material (usually some family of rubber or hybrid material such as PTFE) cause a hydrodynamic action.
In addition, a weak but effective pumping action takes place that further enhances the seal’s ability.
As the seal ages not only does the lip that contacts the shaft wears but the material it is made from becomes less pliable, brittle and from thermal excursions, may have the tendency to bow away from the rotating member. When any of this occurs, the seal becomes challenged and can leak both ways.
When changing a lip seal, it is imperative that it is made from the proper material for the fluid that is going to be isolated along with the rpm of the shaft; the higher the speed the greater the heat generated at the contact point.
Also, many lip seals are directional in nature, especially with but not limited to those used in engines. The seal will usually have a small arrow on it to identify the rotation required for the lip to make contact on the shaft. If installed in the wrong rotation the seal will leak immediately.
The cavity the seal resides in needs to be extremely clean and free of any rust or corrosion. If the seal is even minutely cocked it will not function.
The shaft that runs through it must also be clean and smooth and possess no axial grooves. If there are any grooves they have the ability to work like an auger and pull fluid past the lip.
It is important that when the lip seal is being pressed or tapped into place that it is not damaged. Though there are dedicated seal installers that should be used, many improvise and use a socket from a ratchet set. If common sense is employed and the seal and socket can interface properly, it is an acceptable procedure.
If you are careless or the fit is compromised, then the repair may be for naught.
A lip seal installation kit with a variety of proper sizes may be a worthwhile investment.
Always lightly lubricate the cavity the seal will fit into before attempting installation.
The common mistakes made when servicing any lip seal are not lubricating the shaft so that the lip does not run dry on the rotating member before it can pull a film of liquid; reusing even a fairly new lip seal; buying a cheap imported seal that has the proper O.D. but is made from the wrong material.
Most lip seals are designed that once removed not to be put back into service. This is especially true on a component that spins at high speed and is exposed to high temperatures. You may get lucky every now and then, but do not make it a habit.
If you follow these simple steps and invest in the proper name brand lip seals, you will be rewarded with a job well done and an effective and long-lasting repair.
by Stefano Miletto, Product Marketing Director for the Global Lead Center Heavy Duty, Freudenberg Sealing Technologies
In the agricultural and construction segments, today’s expanding global population challenges farmers to produce higher yields on the same or fewer acres and builders to establish construction sites in difficult and often extreme locations. Mobile machinery must be able to handle extreme temperature variations and higher operating pressures while offering longer service life, improved fuel economy, lower emissions and protection against harsh contaminants. These cost of ownership issues are central to every buying decision.
Today’s mobile machinery customers are focused on technologies that allow their equipment to run longer, more efficiently and trouble-free. High-performance sealing systems in these machines can help address these issues. From a sealing perspective, this means an emphasis on superior dirt and dust protection and reduced mechanical friction.
Seals are used when it is necessary to separate two different media that must not come into contact with one another. As durability and performance requirements increase, manufacturers are moving away from the use of traditional radial shaft seals (RSS) to more robust combi and cassette seals.
Combi and cassette seals are dynamic seals that are concentrically positioned to close the hole created between a shaft and a bore. Combi and cassette seals keep lubricants in and contaminants out, and can be designed to address three different scenarios: a rotating shaft and stationary bore, a stationary shaft and rotating bore, a rotating shaft and rotating bore.
The seals integrate multiple components into one product. Combi seals, for example, typically consist of a sealing ring (single or double), a polyurethane washer and an external wiper, all integrated in one single product. Similarly, cassette seals combine multiple components, including radial shaft seals, into one closed product.
Advantages of combi and cassette seals
Compared to standard radial shaft seals, combi and cassette seals offer multiple advantages to customers, such as fewer inventory and handling accidents, faster and easier assembly, operation cycle time savings that exceed 50%, a reduction in repair costs and more overall system efficiency and durability. Significantly, combi and cassette seals facilitate the transfer of the entire sealing system responsibility to the seal supplier and can reduce the customer’s final manufacturing complexity and costs. A large variety of combi and cassette seal designs have been developed to meet the complete sealing needs of mobile machinery drivelines from engine crankshaft to axle pinions, propeller shafts, wheel hubs and undercarriage.
Combi seals are designed as the best sealing solution for applications where shaft rotation and axial displacement (end play) must be addressed. These seals do not necessarily need axial play to work, but they allow axial movement and provide reliable dynamic sealing together with a higher level of protection from external pollution compared to standard seals. Combi seals work directly on the shaft surface or on an additional sleeve fitted on the shaft. During the axial stroke, combi dust lips remove the dirt wiping the shaft surface.
Cassette seals combine, in one single product, an RSS coupled with its proper working surface and multiple dust lips to offer contamination protection, as required by specific applications. Compared to traditional RSS, the cassette seal design offers several advantages: it eliminates shaft influence on the sealing lip performances, reduces the number of components to be managed and failures caused by assembly damages, and increases dirt protection.
Next-generation cassette & combi seal designs
Freudenberg Sealing Technologies participated in the 2017 International Fluid Power Expo (IFPE) in Las Vegas and introduced a number of cassette and combi seal innovations that set new durability and technology benchmarks in the mobile machinery sector.
The Cassette-S4 – Freudenberg’s most advanced solution for mobile machinery wheel hubs and undercarriage applications – sets durability benchmarks with its superior dirt protection. Additionally, since cassette seals only deal with the running sleeve, a more precise running surface can be produced and a burden on the shaft manufacturer is reduced.
The development of the seal was aimed at exceeding the current sealing performance in extremely harsh operating conditions: resistance to dirt ingress has been significantly increased compared to the other designs. Comparative mud bench testing demonstrates the Cassette-S4’s outstanding longevity to be up to four times longer than its Cassette-S3 predecessor (see figure 2). Field validation performance for the Cassette-S4 was equally significant, with major customers already switching to the optimized design.
A robust and exclusionary labyrinth (while minimizing friction), combines the advantages of a standard cassette design with additional benefits: As the sealing function and tailored contamination protection are combined in one single part, all functional parts of the seal are protected inside an enclosed component, with reduced numbers of components to be managed compared to standard solutions, and reduced risk of accidental damages during handling and installation.
Shaft machining and surface finishing requirements are designed to be much lower than standard sealing solutions. Since no wear traces are on the shaft during operation, a rework/repositioning is not needed during service. The new design provides a plug-and-play concept and is easy to install and to replace.
The dynamic sealing function is supported by a lip design with proprietary Freudenberg material according to different application conditions, with an optimized seal working surface. The seal can stand the same application parameters as previous designs (speed, temperature and pressure range have not to be modified).
Dirt exclusion efficiency has been improved for the worst conditions possible due to design improvements including: five internal dust lips; a robust steel external cover; and a lifetime internal lubrication. The Cassette-S4 allows wider applicability on the field, given by increased capacity to work in highly contaminated environment (dry mud, abrasive sand and water).
The Cassette-S4 lifetime improvement was so impressive that Freudenberg is now benchmarking the design against Mechanical Face Seals (MFS) for the first time ever. Preliminary bench results confirm MFS well-known speed limits and show that Cassette-S4 exceeds the performance of MFS, extending the allowed application speed range up to 6 m/s.
Cassette seals for high speed
The purpose of high-speed cassette seals is to bring the cassette seal design advantages into critical applications like pinion or power take-off units for on- and off-road vehicles.
The key feature for the high-speed cassette seal design is the metal-rubber inner diameter, where the inner diameter metal part is located under the sealing edge to allow a higher heat flow from the sealing edge toward the shaft. It can stand bidirectional or mono-directional shaft rotation, offering from low to medium dirt protection.
Following the market requirement to have products allowing increasing rotational speeds without compromising dirt protection, Freudenberg has also developed the Cassette-HS-EVO. As shown by successfully completed benchmark mud tests and field validation testing, Cassette-HS-EVO reaches the equivalent dirt protection of the current best-in-class cassette seal design, but allows 50% max speeds also in combination with axial play. This unique combination of robustness and flexibility re-defines the traditional seal selection criteria.
Designed specifically for today’s challenges, one combi seal is designed to withstand the harshest operating conditions. As shown by successfully completed benchmark mud tests and field validation testing (see figure 4), the Combi-SF22 design improves the dirt protection extending longevity up to +75 percent compared to current best-in-class design. The Combi-SF22’s external wiper in hardened nitrile butadiene rubber (NBR) demonstrates improved wiping effect, while the premium polyurethane washer with optimized design improves abrasion resistance and is now less sensitive to shaft eccentricity (better for shaft follow ability). The back-to-back seal design allows higher shaft axial stroke, increasing steering potential for axles.
The agriculture and construction sectors have weathered several years of economic downturn that is only now beginning to dissipate. As such, technology innovations that prolong the life of existing machinery, while improving its efficiency, are vital to continued industry growth. At the same time, new regulations and environmental challenges drive the need to make mobile machinery more reliable, comfortable, fuel efficient and clean. Cassette and combi seals are small systems that offer significant advantages and value to customers. Future product optimization is being driven by advances in materials, technologies and design but cassette and combi seals also remain within reach of manufacturers’ current application needs.
Cherry
·
Follow
2 min read
·
Dec 13, 2024
--
Combination oil seals have come to the forefront of sealing components due to their durability and longevity. It is often used to seal agricultural machinery such as tractors. (Honglei(KDIK) shows you various COMBI oil seals and await in your inquiry.)
An oil seal consisting of two or more loose parts can be called a combination oil seal. Most common and simple combination oil seals are made of steel and oil resistant rubber. The two loose parts can complement or work together to make the most of the material’s own characteristics and improve sealing efficiency.
1. The COMBI oil seal consists of a common oil seal and a secondary seal, which mainly prevents the entry of external contaminants.
2. The COMBI oil seal has a spring at the lip of the seal.
3. COMBI oil seals have a dustproof lip.
4. COMBI oil seals are mainly used in environments with high contamination.
5. When subjected to large rotational or translational movements, it is preferable to use it instead of a cassette type combination seal.
6. COMBI oil seals have the distinctive features of combination oil seals: long life and resistance to wear.
7. COMBI oil seals are optimised in terms of the position of the sealing lips and dust lips, and are particularly resistant to contaminant ingress.
8. COMBI oil seals are often used in the driving part of moving parts of agricultural and industrial machinery.
Xingtai Honglei Seal Manufacturing Co., Ltd. registered trademark “KDIK” is senior manufacturer for global markets. We are professional oil seals factory with more than 18 years experience. Our main product lines include kinds of Automobile oil seal, Agricultural & Construction machinery oil seal, Precision Rubber Parts, O-rings and so on. Besides, we accept customer’s own designs and OEM design orders, always focus on Top quality products with competitive price and best service.
Modify: Mar. 22, 2024
Oil seal is the customary name of general seals, which is simply the seal of lubricating oil. It is used to seal grease (oil is a common liquid substance in the transmission system, also refers to the general meaning of liquid substances) mechanical components, it will drive parts in need of lubrication and output parts of isolation, so as not to let lubricant leakage. Static and dynamic seals (general reciprocating motion) are called oil seals with seals. The representative form of oil seal is TC oil seal, which is a double lip oil seal with self-tightening spring completely covered by rubber. Generally speaking, oil seal often refers to this TC skeleton oil seal.
Common materials for oil seals are: Nitrile rubber (NBR), fluorine rubber(FKM), silicone rubber, acrylic rubber, polyurethane, polytetrafluoroethylene and so on.
It has good heat resistance, wear resistance, resistance to various lubricants, greases, oil and gas mixtures, suitable for temperature - 30 - 120 degrees Celsius, but can no longer be used in phosphate hydraulic oil and gear oil containing extreme pressure additives, stable performance in gasoline and mineral oil with low aniline point.
Excellent oil and heat resistance, abrasion resistance, ozone resistance, ultraviolet radiation resistance, especially extreme pressure fluid containing lubricants, gear oil, motor oil, oil series hydraulic oil, etc., suitable for - 30 - 150 degrees Celsius range of work.
Aging resistance, heat resistance, oil resistance, almost applicable to all lubricants, fuel oils, gasoline, oil containing extreme pressure additives is not easy to harden, but cold resistance, high temperature wear resistance is poor, compression deformation is large, suitable for temperature - 20 ~ 250 degrees Celsius.
It has outstanding resistance to high and low temperatures, can be used at 150 degrees Celsius for a long time without performance change, can be used at 200 degrees Celsius for 10,000 hours continuously, and can maintain its unique use flexibility, ozone resistance and weather resistance in the operating temperature range of - 70-260.
It has outstanding chemical stability, thermal stability, friction reduction and self-lubrication. Its pyrolysis temperature is over 400. Therefore, it can work normally in the temperature range of - 200 - 300 degrees Celsius. Except for free fluorine and alkali metals, it has excellent corrosion resistance to chemicals, solvents, hydroxides and acids.
Nitrile butadiene rubber (NBR) and fluorine rubber (FBR) are widely used oil seals. The former has low cost, but its temperature resistance and sealing performance have been improved obviously, but the cost is higher, and it still has some bad common characteristics of ordinary rubber materials, such as poor wear resistance, short service life, especially sensitive to the eccentricity of the shaft, etc. Leakage phenomenon is still widespread. PTFE oil seal is a product with high technology content, which is the direction of oil seal development in the future.
Attention:
When choosing the material of oil seal, the compatibility of material to working medium, the adaptability to working temperature range and the ability of lip edge to follow the rotating axis at high speed must be considered. Generally, the temperature of lip edge is higher than that of working medium at 20-50 C. Attention should be paid to the selection of oil seal materials. The working range of oil seals is related to the materials used in oil seals: NBR, ACM, FPM and NBR.
Anywhere you look on the farm you will find seals of different designs. The purpose of any seal is to keep a fluid or semi-fluid such as grease from leaking out and equally as important, foreign material from entering.
The ability to isolate the component from external influences is just as imperative and possibly in some uses more so, than keeping the fluid inside.
This needs to be understood since most of us only consider a seal failed when there are visible signs of leakage.
A seal employed in a vacuum pump if weakened will introduce dirt and decrease the pump’s operation and useful life without any visible signs.
Many vacuum planters fall prey to a degraded seal that will impact the unit’s performance in the field since dust is highly abrasive.
Though commonly identified as a lip seal, it also goes by the name rotary or shaft seal. On an engine you will find lip seals in use at the front and rear of the crankshaft (one-piece rear main seal), in hydraulic pumps such as for the power steering, in a water pump and other areas.
On a vehicle or machine lip seals are used on the wheel bearings, drive axle bearings, transmission, air conditioner compressor, to name a few.
A lip seal is employed when there is a need to isolate two sides of a component within a rotating member.
Up until around the 1930s leather seals were common but since then lip seals have replaced that style. They have added reliability and improved protection from internal and external leakage.
The lip seal works by having an edge that rides on the rotating part while allowing a film of the fluid to reside between the lip and the shaft.
The confluence of the fluid film and the sealing material (usually some family of rubber or hybrid material such as PTFE) cause a hydrodynamic action.
In addition, a weak but effective pumping action takes place that further enhances the seal’s ability.
As the seal ages not only does the lip that contacts the shaft wears but the material it is made from becomes less pliable, brittle and from thermal excursions, may have the tendency to bow away from the rotating member. When any of this occurs, the seal becomes challenged and can leak both ways.
When changing a lip seal, it is imperative that it is made from the proper material for the fluid that is going to be isolated along with the rpm of the shaft; the higher the speed the greater the heat generated at the contact point.
Also, many lip seals are directional in nature, especially with but not limited to those used in engines. The seal will usually have a small arrow on it to identify the rotation required for the lip to make contact on the shaft. If installed in the wrong rotation the seal will leak immediately.
The cavity the seal resides in needs to be extremely clean and free of any rust or corrosion. If the seal is even minutely cocked it will not function.
The shaft that runs through it must also be clean and smooth and possess no axial grooves. If there are any grooves they have the ability to work like an auger and pull fluid past the lip.
It is important that when the lip seal is being pressed or tapped into place that it is not damaged. Though there are dedicated seal installers that should be used, many improvise and use a socket from a ratchet set. If common sense is employed and the seal and socket can interface properly, it is an acceptable procedure.
If you are careless or the fit is compromised, then the repair may be for naught.
A lip seal installation kit with a variety of proper sizes may be a worthwhile investment.
Always lightly lubricate the cavity the seal will fit into before attempting installation.
The common mistakes made when servicing any lip seal are not lubricating the shaft so that the lip does not run dry on the rotating member before it can pull a film of liquid; reusing even a fairly new lip seal; buying a cheap imported seal that has the proper O.D. but is made from the wrong material.
Most lip seals are designed that once removed not to be put back into service. This is especially true on a component that spins at high speed and is exposed to high temperatures. You may get lucky every now and then, but do not make it a habit.
If you follow these simple steps and invest in the proper name brand lip seals, you will be rewarded with a job well done and an effective and long-lasting repair.
by Stefano Miletto, Product Marketing Director for the Global Lead Center Heavy Duty, Freudenberg Sealing Technologies
In the agricultural and construction segments, today’s expanding global population challenges farmers to produce higher yields on the same or fewer acres and builders to establish construction sites in difficult and often extreme locations. Mobile machinery must be able to handle extreme temperature variations and higher operating pressures while offering longer service life, improved fuel economy, lower emissions and protection against harsh contaminants. These cost of ownership issues are central to every buying decision.
Today’s mobile machinery customers are focused on technologies that allow their equipment to run longer, more efficiently and trouble-free. High-performance sealing systems in these machines can help address these issues. From a sealing perspective, this means an emphasis on superior dirt and dust protection and reduced mechanical friction.
Seals are used when it is necessary to separate two different media that must not come into contact with one another. As durability and performance requirements increase, manufacturers are moving away from the use of traditional radial shaft seals (RSS) to more robust combi and cassette seals.
Combi and cassette seals are dynamic seals that are concentrically positioned to close the hole created between a shaft and a bore. Combi and cassette seals keep lubricants in and contaminants out, and can be designed to address three different scenarios: a rotating shaft and stationary bore, a stationary shaft and rotating bore, a rotating shaft and rotating bore.
The seals integrate multiple components into one product. Combi seals, for example, typically consist of a sealing ring (single or double), a polyurethane washer and an external wiper, all integrated in one single product. Similarly, cassette seals combine multiple components, including radial shaft seals, into one closed product.
Advantages of combi and cassette seals
Compared to standard radial shaft seals, combi and cassette seals offer multiple advantages to customers, such as fewer inventory and handling accidents, faster and easier assembly, operation cycle time savings that exceed 50%, a reduction in repair costs and more overall system efficiency and durability. Significantly, combi and cassette seals facilitate the transfer of the entire sealing system responsibility to the seal supplier and can reduce the customer’s final manufacturing complexity and costs. A large variety of combi and cassette seal designs have been developed to meet the complete sealing needs of mobile machinery drivelines from engine crankshaft to axle pinions, propeller shafts, wheel hubs and undercarriage.
Combi seals are designed as the best sealing solution for applications where shaft rotation and axial displacement (end play) must be addressed. These seals do not necessarily need axial play to work, but they allow axial movement and provide reliable dynamic sealing together with a higher level of protection from external pollution compared to standard seals. Combi seals work directly on the shaft surface or on an additional sleeve fitted on the shaft. During the axial stroke, combi dust lips remove the dirt wiping the shaft surface.
Cassette seals combine, in one single product, an RSS coupled with its proper working surface and multiple dust lips to offer contamination protection, as required by specific applications. Compared to traditional RSS, the cassette seal design offers several advantages: it eliminates shaft influence on the sealing lip performances, reduces the number of components to be managed and failures caused by assembly damages, and increases dirt protection.
Next-generation cassette & combi sealcombi seal designs
Freudenberg Sealing Technologies participated in the 2017 International Fluid Power Expo (IFPE) in Las Vegas and introduced a number of cassette and combi seal innovations that set new durability and technology benchmarks in the mobile machinery sector.
The Cassette-S4 – Freudenberg’s most advanced solution for mobile machinery wheel hubs and undercarriage applications – sets durability benchmarks with its superior dirt protection. Additionally, since cassette seals only deal with the running sleeve, a more precise running surface can be produced and a burden on the shaft manufacturer is reduced.
The development of the seal was aimed at exceeding the current sealing performance in extremely harsh operating conditions: resistance to dirt ingress has been significantly increased compared to the other designs. Comparative mud bench testing demonstrates the Cassette-S4’s outstanding longevity to be up to four times longer than its Cassette-S3 predecessor (see figure 2). Field validation performance for the Cassette-S4 was equally significant, with major customers already switching to the optimized design.
A robust and exclusionary labyrinth (while minimizing friction), combines the advantages of a standard cassette design with additional benefits: As the sealing function and tailored contamination protection are combined in one single part, all functional parts of the seal are protected inside an enclosed component, with reduced numbers of components to be managed compared to standard solutions, and reduced risk of accidental damages during handling and installation.
Shaft machining and surface finishing requirements are designed to be much lower than standard sealing solutions. Since no wear traces are on the shaft during operation, a rework/repositioning is not needed during service. The new design provides a plug-and-play concept and is easy to install and to replace.
The dynamic sealing function is supported by a lip design with proprietary Freudenberg material according to different application conditions, with an optimized seal working surface. The seal can stand the same application parameters as previous designs (speed, temperature and pressure range have not to be modified).
Dirt exclusion efficiency has been improved for the worst conditions possible due to design improvements including: five internal dust lips; a robust steel external cover; and a lifetime internal lubrication. The Cassette-S4 allows wider applicability on the field, given by increased capacity to work in highly contaminated environment (dry mud, abrasive sand and water).
The Cassette-S4 lifetime improvement was so impressive that Freudenberg is now benchmarking the design against Mechanical Face Seals (MFS) for the first time ever. Preliminary bench results confirm MFS well-known speed limits and show that Cassette-S4 exceeds the performance of MFS, extending the allowed application speed range up to 6 m/s.
Cassette seals for high speed
The purpose of high-speed cassette seals is to bring the cassette seal design advantages into critical applications like pinion or power take-off units for on- and off-road vehicles.
The key feature for the high-speed cassette seal design is the metal-rubber inner diameter, where the inner diameter metal part is located under the sealing edge to allow a higher heat flow from the sealing edge toward the shaft. It can stand bidirectional or mono-directional shaft rotation, offering from low to medium dirt protection.
Following the market requirement to have products allowing increasing rotational speeds without compromising dirt protection, Freudenberg has also developed the Cassette-HS-EVO. As shown by successfully completed benchmark mud tests and field validation testing, Cassette-HS-EVO reaches the equivalent dirt protection of the current best-in-class cassette seal design, but allows 50% max speeds also in combination with axial play. This unique combination of robustness and flexibility re-defines the traditional seal selection criteria.
Designed specifically for today’s challenges, one combi seal is designed to withstand the harshest operating conditions. As shown by successfully completed benchmark mud tests and field validation testing (see figure 4), the Combi-SF22 design improves the dirt protection extending longevity up to +75 percent compared to current best-in-class design. The Combi-SF22’s external wiper in hardened nitrile butadiene rubber (NBR) demonstrates improved wiping effect, while the premium polyurethane washer with optimized design improves abrasion resistance and is now less sensitive to shaft eccentricity (better for shaft follow ability). The back-to-back seal design allows higher shaft axial stroke, increasing steering potential for axles.
The agriculture and construction sectors have weathered several years of economic downturn that is only now beginning to dissipate. As such, technology innovations that prolong the life of existing machinery, while improving its efficiency, are vital to continued industry growth. At the same time, new regulations and environmental challenges drive the need to make mobile machinery more reliable, comfortable, fuel efficient and clean. Cassette and combi seals are small systems that offer significant advantages and value to customers. Future product optimization is being driven by advances in materials, technologies and design but cassette and combi seals also remain within reach of manufacturers’ current application needs.