Oil Seals (Part 1): The structure, functions, and types of oil ...

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

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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

&#;

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.)

&#;

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.

&#;

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.

&#;

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.

&#;

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.

&#;

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.

&#;

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.

&#;

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 -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

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)

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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

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 &#; 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

&#; Spring code

No code: without minor lip

A: with minor lip

&#; Lip type code

No code: without minor lip

A: with minor lip

&#; 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. &#; 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:

Introduction

Oil seals are an essential part of any engine, transmission, or other machinery that uses moving parts. They help to prevent oil from leaking out of the system, which can damage the components and lead to costly repairs.

Oil seals are typically made of a flexible material, such as rubber or synthetic rubber, and are designed to create a tight seal between two moving parts. They are typically installed in a groove in the shaft or housing, and are held in place by a snap ring or other type of retainer.

Oil seals work by creating a barrier between the moving parts and the oil. The oil is forced out of the seal by the pressure of the moving parts, and the seal prevents it from leaking back out. This helps to keep the components lubricated and prevents them from overheating.

Oil seals are an important part of maintaining the performance and longevity of your engine or other machinery. If you notice any leaks, it is important to have the seals replaced as soon as possible.

Types of Oil Seals

There are many different types of oil seals, each designed for a specific application. The most common types of oil seals include:

• Mechanical seals are used to prevent the leakage of fluids between two moving parts. They are typically made of a soft material, such as rubber or plastic, and are designed to conform to the surface of the parts they are sealing. Mechanical seals are often used in engines, transmissions, and other high-pressure applications.
• Radial lip seals are used to prevent the leakage of fluids from rotating shafts. They are typically made of a flexible material, such as rubber or plastic, and have a lip that conforms to the shaft. Radial lip seals are often used in bearings, pumps, and other rotating applications.
• Thrust washers are used to prevent the leakage of fluids from reciprocating shafts. They are typically made of a hard material, such as metal or plastic, and have a lip that conforms to the shaft. Thrust washers are often used in engines, compressors, and other reciprocating applications.
• O-rings are circular seals that are made of a flexible material, such as rubber or plastic. They are typically used to seal joints and connections. O-rings are often used in engines, transmissions, and other high-pressure applications.
• V-rings are similar to O-rings, but they have a V-shaped cross-section. They are typically used to seal joints and connections in applications where there is a high degree of vibration. V-rings are often used in engines, transmissions, and other high-pressure applications.

How to Choose an Oil Seals

Oil seals are used to prevent the leakage of fluids from a rotating shaft or housing. They are typically made of a soft material, such as rubber or plastic, and are designed to conform to the shaft or housing as it rotates.

There are a number of factors to consider when choosing an oil seal, including:

• The type of fluid being sealed. Oil seals are available for a variety of fluids, including water, oil, grease, and solvents. It is important to choose a seal that is compatible with the fluid being sealed.
• The size of the shaft or housing. Oil seals are available in a variety of sizes to fit different shafts and housings. It is important to choose a seal that is the correct size for the application.
• The operating temperature. Oil seals are available for a variety of operating temperatures. It is important to choose a seal that can withstand the temperature of the application.
• The operating environment. Oil seals are available for a variety of operating environments, including wet, dry, dusty, and corrosive environments. It is important to choose a seal that is suitable for the operating environment.

Oil Seals Maintenance

Oil seals should be inspected regularly for signs of wear or damage. If a seal is damaged, it should be replaced as soon as possible. To prevent oil seals from becoming damaged, it is important to keep the oil level in the system topped up and to change the oil according to the manufacturer's recommendations.

Conclusion

Oil seals are an essential part of any engine or other machinery that uses moving parts. They help to prevent oil from leaking out of the system, which can damage the components and lead to costly repairs. By choosing the right type of oil seal and maintaining it properly, you can help to keep your engine or other machinery running smoothly and efficiently.

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