Jul. 28, 2025
Agriculture
NNK OIL SEAL Manufacturer
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What is a Skeleton Oil Seal?
A Skeleton Oil Seal, sometimes referred to simply as a skeleton seal, is a type of sealing device that is primarily used to prevent leakage of fluids in rotating shafts. Designed to endure harsh operating environments, these seals feature a unique structure that combines a flexible sealing lip with a rigid supporting structure. This ensures a perfect balance between functionality and structural integrity. Unlike traditional oil seals that rely solely on materials like rubber or elastomer, skeleton seals integrate a metal casing that provides additional support and resilience.
The skeleton seal consists of three main components: the outer rigid body (often made of metal or a composite material), a rubber or elastomeric sealing lip, and a spring mechanism. The rigid body is typically designed to be easily mounted into the housing or casing of the machinery, while the sealing lip comes into direct contact with the rotating shaft. The spring mechanism applies constant pressure to the sealing lip, ensuring a snug fit and minimizing wear over time.
Key Features and Advantages
1. Enhanced Durability: Skeleton Oil Seals are designed to withstand extreme conditions, including high temperatures and varying pressures. The combination of a metal casing and rubber lip gives it a longer lifespan compared to traditional seals, making it suitable for high-wear applications.
2. Leak Prevention: One of the primary functions of any oil seal is to prevent the leakage of lubricants and other fluids. The unique design of the skeleton oil seal, with its reliable spring-loaded sealing lip, effectively mitigates fluid loss, enhancing the overall efficiency of the machinery.
3. Versatility: These seals are applicable in a wide range of industries, from automotive to heavy machinery, agricultural equipment, and manufacturing processes. Their ability to adapt to various shaft sizes and configurations makes them an ideal choice for diverse applications.
4. Cost-Effective Solution: While the initial investment may be slightly higher than that of traditional seals, the longevity and reduced maintenance needs of skeleton oil seals often lead to lower overall operating costs. By minimizing downtime due to fluid leaks, businesses can save on both time and repair expenses.
5. Easy Installation: The structural design of skeleton oil seals allows for straightforward installation. They are engineered to fit various types of shafts and housings, enabling quick replacements without requiring specialized tools or extensive machinery downtime.
6. Low Friction Operation: The smooth contour and elastomeric materials used in skeleton seals help to ensure low friction when in operation. This not only reduces wear on the shaft and seals themselves but also contributes to more efficient machinery performance.
7. Resilience to Contaminants: Skeleton oil seals can also offer resistance to dirt, dust, and other contaminants, which may compromise the integrity of simpler seals. This feature is particularly advantageous in challenging environments where exposure to external elements is inevitable.
Functions of Car oil Seals：
Seals are integral parts of the automotive industry. They are used in a variety of different applications. Seals may be small but they serve an even bigger and greater purpose in the integrity of the vehicle. Below are the functions of the seals in cars.
• They enclose the gas and liquid within the chamber. The gas tank contains seals that allow the vehicle to use up the fuel without wasting it. Hydraulic seals are also important for the movement of vehicle parts. Systems within the vehicle that uses hydraulic seals include suspensions and brakes.
• Stave off contaminants from crucial parts of the vehicle components. Seals keep away dust and other debris away from the engine and other important components of the vehicle.
• They keep liquids and gases separated from one another. There are many car parts that use liquids and gases to function properly. Examples include: the engine which keeps the coolant and engine oil, brakes for the brake fluid, and the reservoir to keep the power steering fluid to name a few.
• To protect bearings. Bearings are often filled with lubricants that protect the parts from corrosion, wear, and tear. The bearings need to be spotless, thus a contamination within it may cause the housing elements to experience premature failure. The seals protect the bearing by preventing dust and powder from entering the assembly.
Shaft seals, also known as oil seals, are devices that prevent fluids from leaking out of machinery. They're typically made from a rubber or plastic material and are designed to fit around the shaft to create a barrier that keeps oil, grease and other fluids contained.
Shaft seals work by creating a fluid film barrier between the sealing lip and the rotating shaft, the addition of a wiper lip also helps to keep out the general environment. The shaft seals outer casing diameter is sealed via its interference fit in the recess within the machinery it operates.
Shaft seals play a critical role in the effective operation and maintenance of industrial machinery. They're designed to prevent fluids, such as oil, grease and other lubricants, from leaking out of equipment and causing damage to critical components. Benefits of shaft seals include:
What is a Wheel Hub Seal?
A wheel hub seal, sometimes referred to as a wheel bearing seal, is a circular, gasket-like component that is fitted in the wheel hub assembly. Its primary purpose is to protect and secure the wheel bearings, which are essential for allowing smooth rotation of the wheels. These seals act as a barrier, preventing the intrusion of dirt, dust, moisture, and other contaminants that could potentially cause damage to the bearings and other integral components of the wheel assembly.
Functionality
The wheel hub seal plays a twofold role in vehicle maintenance:
1. Protection: The first line of defense against environmental contaminants is provided by the wheel hub seal. It keeps harmful substances such as water, mud, and dirt from penetrating the wheel hub. This is crucial because any foreign particles that enter the hub can lead to accelerated wear and tear on the bearings, ultimately resulting in decreased vehicle performance and potentially costly repairs.
2. Lubrication Retention: The seal plays a pivotal role in keeping the wheel bearing grease contained within the hub assembly. Proper lubrication is necessary for reducing friction between moving parts, thereby enhancing the overall functionality and longevity of the wheel bearings. A well-functioning wheel hub seal ensures that the grease remains intact, facilitating a smoother rotational motion and extending the lifespan of the bearing assembly.
Company Profile:
Our advantages：
We are a professional Oil Seal Manufacturer
1. We cooperate with first-class raw material suppliers in China and abroad, using the best raw materials. High quality NBR, silicon and FKM materials are imported from Japan,USA, Germany and Southeast Asia.
2. Top quality custom rubber products that can completely meet your needs.
3. Fast production & in-time delivery that never delay your project and usage.
4. One-stop custom service and value-added service to save your time and cost.
5. OEM/ODM Services are available. We can design and produce various Non-standard
Rubber Parts according to your PDF,3D or STEP drawing files.
6. All of rubber finished products are 100% inspected before shipment.
We are an honest oil seal supplier.We have very good expertise, experienced technicians, new good equipment, strict inspection procedures, durability and performance seal testing, PPAP level IIl submission. Strict process control, international standard high-quality products and affordable prices. The strength factory has more than 150 workers, strong delivery capacity, we provide you with the best after-sales service.
FAQ
1.What is your packing?
a. Paper roller: 10pcs in one roller, 200 rollers in one carton b. PP bag: 50 or 100pcs in one bag,15 or 30 bags in one carton
C.Box:1pctoabox
d. According to customer's request.
2.Date of Delivery
a. 1-2 days if goods in stock.
b. 10-15 days if goods out of stock with molding.
c.25-30 days if goods out of stock without molding.
3.Payment Term:
a. 30% T/T in advance and 70% balance paid before shipment.
b. West union/Money Gram
C.Paypal
d.others for discussion
4.Can you produce according to the samples?
a. We accept ODM and OEM at the same time.We have the ability to provide the sample of the products of decomposition, develop the mould, for production.
5. How do you make our business long-term and good relationship?
a. We will continue to improve the process control, and improve the quality of our products and work to reduce operating costs and provide a competitive price for customers, to ensure that customers benefit
b. We seriously treat every customer, in good faith with them to do business, make friends, no matter how much volume, we will provide
Oil seals are widely used as sealing devices for machines.
JTEKT's oil seals are described in our catalog, Oil Seals & O-Rings.
However, the catalog uses a large number of technical terms and is very long, so many people seem to have trouble handling it.
Therefore, this series of columns will summarize the following in order:
• The structure, functions, and types of oil seals
• How to select the right oil seal
• Handling of seals, and causes and countermeasures for oil seal failure
A wide range of sealing devices are used in various machines.
Sealing devices serve the following functions:
As shown in Figure 1, sealing devices come in two types: contact and non-contact.
Oil seals are among the major contact type sealing devices.
Figure 1: Types of sealing devices
Please see the following for the types of sealing devices for bearings.
How to Select the Right Bearing (Part 7): Components surrounding the bearing
Oil seals come in various shapes to fit the machines and substances to be sealed.
Figure 2 shows the structure and the names of the various components of the most typical oil seal.
The functions of the various components are also indicated in Table 1.
Figure 2: Typically shaped oil seal and component nomenclature
* "KOYO" is a registered trademark of JTEKT.
Table 1: The functions of the various components
No.
Name
Functions
①
Main lip The main lip is the most critical component of the seal.
Its sealing edge comes in full contact with the shaft surface in order to provide excellent sealing performance.
(See Figure 3.)
②
Minor lip The minor lip prevents the entry of dust and contaminants from outside.
Lubricant can be retained in the space between the main lip and the minor lip.
③
Sealing edge This refers to the component of the oil seal that makes contact with the shaft.
It is wedge-shaped to be pressed against the shaft surface and makes contact with the shaft to ensure sufficient sealing performance and suitability for operation at high peripheral speed.
④
Spring The spring supplements the tightening force (i.e., the lip radial load) to ensure enhanced sealing performance and tight contact between the shaft and the sealing edge.The spring also prevents the deterioration of main lip sealing performance caused by high heat or other such factors.
⑤
Metal case The metal case provides rigidity to the seal, helping it settle on the housing securely. It also ensures easy seal handling and mounting.
⑥
O.D. (outside diameter) surface The O.D. surface affixes the oil seal to the housing and prevents leakage , through the fitting area, of substances to be sealed, while excluding contaminants.
⑦
Fluid side face The front-end face of the seal is called the nose. The nose is made of rubber and forms a gasket seal when compressed on the housing shoulder.
⑧
Air side face The oil seal surface vertical to the center line of the shaft on the side that does not come in contact with substances to be sealed is called the back face.
Figure 3: Sealing function of main lip radial load
* "KOYO" is a registered trademark of JTEKT.
Figure 4 shows the features of a JTEKT oil seal.
Figure 4: JTEKT oil seal features
For more detailed information, please see the following:
Names and functions of seal components
Seals are classified by O.D. wall material, lip type, and whether they have a spring or not.
Major oil seals are specified in ISO -1 and JIS B -1.
Table 2 shows the common types of oil seals, while Table 3 shows the features of each type of oil seal.
Table 4 lists the JTEKT oil seal type codes and corresponding ISO and JIS standards.
Table 2 a): Common types of oil seals (with spring)
With spring Rubber O.D. wall Metal O.D. wall
Metal O.D. wall
(with a reinforcing inner metal case)
Without minor lip
Type code
With minor lip
Type code
Table 2 b): Common types of oil seals (without spring)
Without spring Rubber O.D. wall Metal O.D. wall
Without minor lip
Type code
With minor lip
Type code
Table 3: Features of each seal type
No.
Type
Features
1
With spring type Secures stable sealing performance.
2
Rubber O.D. wall type Provides stable sealing performance around the seal O.D. surface.
3
Want more information on d type skeleton oil seal? Feel free to contact us.
Featured content:Metal O.D. wall type Ensures improved fitting retention between the seal O.D. and the housing bore.
4
Metal O.D. wall type (with a reinforcing inner metal case) Protects the main lip.
5
With minor lip type Used for applications where there are contaminants, such as dust and foreign matter, on the air side face of the oil seal.
Table 4: JTEKT oil seal type codes and corresponding ISO and JIS standards
JTEKT
ISO -1 1)
JIS B -1 2) MHS Type 1 HMS Type 2 HMSH Type 3 MH － HM － MHSA Type 4 HMSA Type 5 HMSAH Type 6 MHA － HMA －
Notes
1) ISO: International Organization for Standardization
2) 2) JIS: Japanese Industrial Standard
JTEKT provides special seals for use in a wide variety of machines and applications.
Table 5 lists the major special seals, their shapes, and their features.
Table 5: The major special seals, their shapes, and their features
Name Type
(type code) Shape Features
Helix Seal
The hydrodynamic ribsa) provided in one direction on the air side face of the lip ensure higher sealing performance. Perfect Seal The hydrodynamic ribsa) provided in two directions on the air side face of the lip ensure higher sealing performance (higher sealing performance in both rotational directions of the shaft).
Super Helix Seal
The hydrodynamic ribsa) have a two-stepped rib configuration provided in one direction on the air face of the lip. Even if the first rib is worn out, the second rib comes into contact with the shaft surface, meaning that this type of oil seal ensures higher sealing performance. Seal with Side Lip A large side lip ensures prevention of entry of dust/water.
a)
Function of hydrodynamic ribs
For more detailed information, please see the following:
Special seal types and their features
Figure 5 explains the JTEKT seal numbering system.
Seal numbers consist of
(1) the seal type code,
(2) the spring code,
(3) the lip type code,
(4) the dimensional numbers, and
(5) the special type code,
and Table 6 shows examples of each of these codes/numbers.
Figure 5: JTEKT seal numbering system
Table 6: Codes and numbers used in seal numbers
No. Code and number Example ① Seal type code (*)
MH: O.D. wall is a rubber material
HM: O.D. wall is a metal case
MH(S)H: O.D. wall is metal with a reinforced inner metal case
② Spring code
No code: without minor lip
A: with minor lip
③ Lip type code
No code: without minor lip
A: with minor lip
④ Dimensional numbers Shaft number 45: The seal suits the shaft diameter of ϕ45 mm. Housing bore number 70: The seal suits the housing bore diameter of ϕ70 mm. Width number 8: The seal width is 8 mm. ⑤ Special shape code
J: Additional code is added here as an identifier when two or more seals have exactly the same type codes and dimensional numbers.
Note: For seal type codes, see Table 2.
Oil seals are used in a great many machines.
Oil seals are used in many areas around the car.
Figure 6 shows the places where each seal type is used.
Figure 6: Oil seals for cars
For more detailed information, please see the following:
Oil seals for cars
Oil seals are used in a great many devices for steel production equipment.
Figure 7 shows the places where each seal type is used in a rolling mill.
Figure 7: Oil seals for steel production equipment (rolling mill)
For more detailed information, please see the following:
Oil seals for steel production equipment
Oil seals are one of the major contact type sealing devices.
• They prevent leakage of the lubricant or other sealed substance, and
• prevent entry of dust and foreign matter (dirt, water, metal powder, etc.) from outside.
Oil seals come in various shapes to fit the machine or substance for sealing.
For this reason, when designing a machine, it is important to select the oil seal that is right for that machine.
Next time, we will explain the key points to consider when selecting your oil seal.
If you have any technical questions regarding oil seals, or opinions/thoughts on these "Bearing Trivia" pages, please feel free to contact us using the following form:
Oil seals, also referred to as shaft seals, are widely used to prevent the leakage of medium (such as oils and grease) along a rotating shaft. This leak prevention is primarily achieved by the sealing element which can be made from a wide range of materials that are chosen according to each application. They are commonly used in gearboxes, hydraulic cylinders, and related components.
An oil seal is designed to perform three major functions: to prevent lubricants from leaking outside the seal even under high pressure, to act as a barrier to retain the lubricating oil, and to prevent dirt and other contaminants from entering the unit.
Shop for Oil Seals
Oil seals normally consist of three basic components: the sealing element, the metal case, and garter spring.
The sealing element makes up the interior of the oil seal, and the materials commonly used are:
The metal case is the exterior (or frame) of the oil seal, the principal function of which is to give rigidity and strength to the seal. The material of the case must be selected depending on the environment where the seals are to be used. Often the metal case is covered by the same rubber material used in the sealing element, which also helps seal the exterior of the oil seal in the housing bore. Common case material types are:
The garter spring is located at the end of the primary sealing lip and used to apply pressure to the sealing lip against the shaft. Common garter spring material types are:
What is Oil Seal | Purpose , Types of Oil Seal , Advantages
OIL SEAL
Oil seals, also known as shaft seals, are radial lip type seals which are primarily used for retaining lubricants in equipment having rotating, reciprocating or oscillating shafts. The rotating shaft application is most common.
An oil seal normally consists of three basic components: the sealing element, the metal case and the spring. The purpose of the sealing element is to stop the fluid from leaking between the shaft and housing. The metal case will give rigidity and strength to the seal while it is being held in the bore or recessed groove. The garter spring ensures constant pressure and maintains the radial force to the shaft, flattening the sealing edge to a defined width. The garter spring maintains the radial force exerted by the sealing lip around the shaft surface. All materials must be selected depending on the environment in which the oil seal will function.
The performance of these seals depends to a large extent on a suitable unit load being maintained at the seal-shaft interface. These seals withstand a pressure of 15PSI and their working depends on parameters like shaft diameter, shaft speed, working temperature, service conditions, etc
Oil seals or shaft seals are an integral part in any rotating and moving part assembly. Oil seals find great deal of usage in gearboxes, hydraulic cylinders, etc. The usage of the seals in areas concerned with motion also earns them a name of “Dynamic Oil Seals.”
The purpose of the oil seals is
To act as a physical barrier retaining the lubricating oil where it is bound to be.
To prevent thelubricating oil from leaking outside even under high pressure of the oil.
To act as a barrier and prevent dirt, contamination and other external entities from entering the system containing the lubricating oil.
Constructional Aspects of an Oil Seal:
1. The oil seal consists of a metal ring as the inner skeleton which provides the structural stability to the oil seal.
2. The outer skin is made of nitrile rubber and various other materials which are used based on the requirement.
3. The spring on the lip of the oil seal tends to provide support to the lip and prevents the lubricant from leaking outside and also prevents the entry of contaminants from outside.
TYPES OF OIL SEAL
Double Lip Oil Seals
In this an auxiliary lip is provided along with the regular sealing lip. The additional dust lip protects the main sealing lip against dust and other fine solid contaminants and therefore this type is recommended for use in polluted environments. To achieve a long lifetime a suitable lubricant between the two sealing lips should be applied.
Advantages:
– Good static sealing
– Compensation of different thermal expansion
– Reduced risk of fretting corrosion
– Effective protection against air side contaminants
– Higher bore surface roughness is allowed
– Installation in split-housings
– Modern lip design provides low radial forces
Duplex Oil Seals
Sometimes, two different kinds of fluids leak from one chamber to another and gets mixed up. Here, this type comes as a boon. This is a metal inserted duplex type oil seal recommended on such assembly where mix-up of two different fluids is to be prevented.
Oil Seals without Spring
This type of oil seal can withstand only low speed and friction. It is recommended in places where thick fluid or grease is to be sealed. This is not recommended for difficult applications.
Material:
Oil seals are made out of nitrile synthetic rubber with steel stiffener rings. Other rubbers such as viton, silicon, neoprene or poly acrylic can be used for specific applications. The stiffener rings may be stainless steel or brass where highly corrosive fluids are to be sealed. Springs are generally made of spring steel to IS: :Gr.ll or from stainless steel or bronze for corrosion resistance
Type A Oil Seals
Sealing of lip type seal is normally a result of an interference fit between the flexible sealing element, usually augmented by spring pressure and a shaft. Fluid retention is based on the precise amount of lip contact pressure. In most lip seals, increased fluid pressure in the sealed area causes lip contact pressure on the shaft to increase.
Advantages:
– Good static sealing
– Compensation of different thermal expansion
– Reduced risk of fretting corrosion
– Higher bore surface roughness is allowed
– Installation in split-housings
– Modern lip design provides low radial forces
Type B Oil seals
This is almost similar to that of ‘A’ type seal. But this has the metal case placed outside. When the housing is rough, temperature is high and working conditions are severe, this type is preferred.
Type C Oil seal
Type ‘C’ oil seal has an additional cup inserted into the outer cup of ‘B’ type. The supplementary metal inner ring provides a superior stiffness. This type is recommended for use in heavy polluted environments. As the static sealing between housing and metallic shell is limited, low viscosity media can “creep”.
Advantages:
– Very good fitting stability avoiding pop-out of the seal
– Modern lip design provides low radial forces
– Superior radial stiffness, especially for very large diameters
– Cost effective for expensive elastomer materials
– Suitable for use in combination with axial seal
Material used for Oil Seal :
Based on the application of the oil seal, the outer skin layer tends to differ. Here are some types of the materials used for the outer skin of the oil seal.
1. Nitrile rubber – The commonly used material for oil seals
2. Silicone – Used in specific applications where only light loads are applied.
3. Poly acrylate
4. Fluroelastomer also popularly known as Viton. – The high temperature resistant material used in places where temperature is more than 120 Degree Celcius.
5. PolytetraFluroEthylene (PTFE)
The oils seals require certain prerequisites to be maintained for their proper working. They are as follows:
a) The shaft on which the oil seal is to be mounted should be ground with the surface finish or surface roughness between 0.2 to 0.8 Microns. It is best for the shaft to be hardened atleast to 40 – 45 HRc in order to prevent groove formation on the shaft due to the pressure exerted by the spring.
b) The area where the oil seal is seated is to be plunge ground in order to prevent wear grooves that normally tend to wear out the lip of the oil seal at a faster rate.
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