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

If you are looking for more details, kindly visit agricultural machinery and equipment oil seals.

1. What are oil seals?

A wide range of sealing devices are used in various machines.
Sealing devices serve the following functions:

• Prevent leakage of sealed lubricant from inside
• Prevent entry of dust and foreign matter (dirt, water, metal powder, etc.) from outside

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

2. Oil seal structure and functions

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　

3. Seal types and numbering system

1) Common seal types and their features

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 6194-1 and JIS B 2402-1.
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

Additional reading:
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If you want to learn more, please visit our website Industrial Oil Seal Manufacturing Company.

1

With spring type Secures stable sealing performance.
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2

Rubber O.D. wall type Provides stable sealing performance around the seal O.D. surface.

3

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 6194-1 1)

JIS B 2402-1 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

2) Special seal types and their features

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

3) Seal numbering system

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.

4. Example of the applications of seals

Oil seals are used in a great many machines.

1) Oil seals for cars

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

2) Oil seals for steel production equipment

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

5. Conclusion

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:

Explore All About Industrial Oil Seals

Oil seals, also known as oil lip seals, dirt seals, grease seals, shaft seals, or rotary seals, are used to fill the gaps between stationary and revolving parts of the equipment. They are designed to prevent the leakage of fluids from the machinery and inhibit contaminants from reaching these fluids. They contribute to the longevity and reliability of the equipment like engines and gearboxes in industrial equipment. This post discusses the importance of oil seals, the different types of materials that are used in the manufacturing of

Oil seals, also known as oil lip seals, dirt seals, grease seals, shaft seals, or rotary seals, are used to fill the gaps between stationary and revolving parts of the equipment. They are designed to prevent the leakage of fluids from the machinery and inhibit contaminants from reaching these fluids. They contribute to the longevity and reliability of the equipment like engines and gearboxes in industrial equipment. This post discusses the importance of oil seals, the different types of materials that are used in the manufacturing of oil seals and many more.

Overview of Oil Lip Seals

Oil seals are used to fill gaps between stationary and revolving parts of equipment, often known as radial shaft seals or rotary seals. These seals are frequently employed to keep impurities out and prevent lubricating oils, hydraulic fluids, or other liquids from escaping out of the system. An oil seal features:

• Outside Metal Ring: The seal's outside metal casing helps in maintaining its shape and offers structural support.
• Rubber or Elastomeric Sealing Lip: The sealing lip typically encloses the shaft in a tight seal formed of rubber or elastomeric material.
• Spring: Some oil lip seals incorporate a spring to apply constant pressure against the shaft, ensuring a secure seal.

Types of Materials Used for Manufacturing Oil Seals

Oil lip seals play a significant role in several industrial applications to avoid intermixing fluids and prevent contaminants and moisture from affecting the bearings. With such a vital role to play, it is essential to choose the right material for these seals. The choice of the material will depend on factors like the type of fluid being sealed, operating temperature, pressure, and compatibility with the operating environment. The following list of materials is typical for making oil lip seals:

• Nitrile (NBR): The nitrile rubber or nitrile provides excellent resistance to numerous oils and greases, including mineral grease and hydraulic oil. There are several synthetic lubricants and greases in the market based on glycol which may cause harm to NBR rubber compounds depending on their composition. Due to their excellent durability and cost-effectiveness, these seals are used in a wide range of operating conditions. However, NBR is unable to withstand exposure to acids and solvents.
• Polytetrafluoroethylene (PTFE): This fluoropolymer is known by the brand name Teflon and is known to assure the best chemical resistance and exceptionally little frictional resistance. It is the material of choice for several types of rotating seals used in the chemical, food, and pharmaceutical industries.
• Polyurethane (PU): Polyurethane seals offer excellent abrasion resistance and durability. They are suitable for high-pressure applications and provide good resistance to hydraulic oils. Polyurethane oil seals are often used in hydraulic and pneumatic systems.
• Viton: The exceptional resilience of Viton against chemicals, strong fluids, and high temperatures is well recognized and makes this a great material for creating seals for demanding applications. This material is known to maintain its flexibility, strength, and shape even in the harshest situations. When designers and engineers use oil lip seals for industry made of Viton material, their durability and dependability guarantee reduced downtime, improved performance, and a competitive advantage. It works effectively in applications involving severe chemicals, synthetic oils, and fuels.
• Ethylene Propylene Diene Rubber: This elastomer is used for creating oil lip seals for industry and other sealing elements such as U-cups. The oil lip seals made of this material would exhibit excellent resistance to steam, hot water, washing agents, and polar organic solvents. They are used to seal phosphate ester hydraulic fluids, such as Skydrol. These seals are not recommended for petroleum-based fluids, and can be effectively used with acetone, steam, alkalies, and dilute acids.

Although oil seals have been around for a while, choosing the right one still needs careful planning. If you are sure about the type of seal needed for your application or looking to replace your current seals with custom oil seals that meet your application requirements, then do not hesitate to contact the experts at SSP Seals – a leading industrial seal manufacturer in the USA. The company offers one of the most comprehensive selections of oil seals in the USA in a wide range of materials and profiles such as Type A Single Lip, Type ADL Double Lip, Type AO Single Lip, Type AODL Double Lip, Type B Single Lip Metal Case w/Spring, Type BDL Double Lip, and many more. You can visit the website for more information.

The company is the world’s best nbr rubber parts for sealing supplier china supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

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