Posted by on 31st May 2019
Oil seals are often called grease, fluid, or dirt seals. These seals close spaces between stationary and moving components in mechanical equipment. Oil seals are designed to prevent the escape of lubricant. They also block contaminants from entering machinery. This is especially important in severe environments where heat and foreign objects may be frequently present. They also prevent the mixing of different mediums like lubricating oil and water.
Oil seals come cataloged as metric oil seals or imperial sized oil seals. The seals can also be custom-made to match the bearings in new types of machinery. They are installed in practically every type of machine including vehicles, protecting all kinds of precision, precisely-fitted ball bearings, sleeve bearings, and roller bearings.
The oil seal gets its structural stability from an interior metal ring which serves as an inner skeleton. The outer skin is made of a more flexible material like nitrile rubber or other materials based on the physical environment of the seal. A spring on the lip of the seal supports the lip and keeps the lubricant from leaking. The lip construction is what blocks contaminants from outside.
Where loads are light, the outer skin layer can be made of silicone. It can be made of Fluroelastomer (orViton) to protect under high temperatures (more than 120 degrees Celcius). The skin can also be made of Poly Acrylate or Polytetra-FluroEthylene.
The shaft on which the oil seal is mounted has to be ground to a rough surface finish. The shaft also should be hardened to prevent grooves forming on the shaft when the pressure is exerted by the spring on the seal. The area where the seal is fitted also has to be ground to prevent grooves that tend to wear out the lip of the oil seal faster than normal.
Oil seals have a flexible lip that actually rubs against the rotating shaft or housing to prevent leakage. The spring keeps the lip in contact with the shaft. Bearing isolator oil seals are dynamic seals that incorporate a rotor or rotating member and a stator or stationary member. The rotor actually turns with the shaft. Some oil shafts are bearing isolators with a "labyrinth" construction. Others incorporate simpler O-rings.
A patent for an oil seal was filed by Nelson Thomas Edward on August 12, 1937, and published a year later. There were two purposes described. The device was to provide an oil seal between a fixed housing and a rotating part. The seal is described as
made of a yieldable resilient material having flat sealing faces and comprising two ring portions connected together by an annular portion substantially v-shaped in cross-section which may yield or expand as the mounting requires.
The oil seal would seal one face against a rotating member and the other face to a stationary housing. It would prevent dirt from coming between the hub or shaft and the seal.
Early engines used O-rings (also called packing rings or toric joints) as seals (first patented in 1896). These are just mechanical gaskets in the shape of a torus (a circular ring--like a lifesaver), seated in a groove and compressed during assembly between two or more parts. It creates a seal at the interface. However, O-rings require a fluid film to lubricate them. They have limited usefulness in vacuum application and at extremes of temperature. The modern oil seal represents a significant improvement over the simple O-ring because it effectively seals in lubrication and prevents contamination from outside under a wide range of pressures and temperatures.
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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.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.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.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.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.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.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.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.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 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. wallWith 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.With spring type Secures stable sealing performance.
2
Rubber O.D. wall type Provides stable sealing performance around the seal O.D. surface.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.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.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.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 －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
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).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.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 code③ 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 code④ 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:
The development history of oil seals ? The interactive sealing encyclopedia oil seal, commonly known as SIMMERRING in English, was invented by a German sealing company, Dr. Froydenbeck Simmer, in 1929. Dongsheng Oil Seal tells you that oil seals are usually used in conjunction with rotating bearings, and are set between the stationary part and the rotating shaft. In the state of shaft rotation, the oil film on the sliding surface of the sealing pair established between the sealing lip and the rotating shaft surface prevents the leakage of lubricating oil. At the same time, relying on the oil seal of the sealing pair established between the sealing lip and the rotating sliding, it prevents external dust and debris from entering the mechanical interior, ensures that the lubricating medium is not contaminated and reduces bearing wear. Therefore, oil seal is one of the important sealing components for maintaining bearing life and ensuring the normal operation of mechanical equipment, and it is also the oil seal for sealing oil!
in the early stages of World War II, oil seal materials were shaped and manufactured using leather. After the war, the use of synthetic rubber oil seals gradually increased, especially in the past 20 to 30 years. Due to the rapid development of industries such as mechanical manufacturing, vehicles, aviation, and aerospace, oil seals were required to be resistant to high and low temperatures, high pressure, special working media, and more suitable for high-speed, vibration, and extended service life, This has promoted extensive and in-depth research on sealing materials, structures, performance tests, quality control methods, and sealing mechanisms of oil seals, greatly improving the sealing performance and service life of oil seals. The successful development of fluid powered oil seals with reflux effect in foreign countries from the 12th century to the early 1960s further advanced the technology of oil seals and solved some very difficult sealing problems.
Polytetrafluoroethylene oil seals have been in use since 1980. They are not only more suitable for ultra high speeds, but also more resistant to high and low temperatures, various corrosive working media, and are suitable for working environments with dry friction. In the 1980s, oil seals began to be imported and exported, and the country began to implement international standards.
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Post time: Aug-17-2023Post time: Aug-17-2023
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