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
You will get efficient and thoughtful service from NNK.
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
'
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.'
Sealing edge This refers to the component of the oil seal that makes contact with the shaft.'
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'
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. wallMetal 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 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
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
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
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
No code: without minor lip
A: with minor lip
' Lip type codeNo 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 codeJ: 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:
We offer quality sealing and cost-effective oil seal designs that help keep equipment running longer while reducing downtime. Through our comprehensive selection we provide oil seals with short lead times and with a variety of designs for use in many common and more challenging industry applications. When selecting an oil seal, it is important to know what sort of design is needed, and we have outlined a few of the more common elements below.
Shop for Oil Seals
Our oil seals have many different available lip designs, with some being simple and others complex, due to their special application. However, the most common industry lip standards are described below:
We offer oil seals in many various case designs from the most simple to the most challenging applications. Below are just a few of the most commonly used case designs for most sealing applications:
Oil seals with outer metal cases may include finishes or treatments that are applied to the outer edge to aid in rust protection, identification, and sealing of scratches or imperfections in the housing bore. Common finishes applied to the outside edge of metal O.D. oil seals include: Plain (a bonding agent that is usually a yellowish-green color), a Color Painted edge, and a grinded-polished edge.
Combining both the lip and case types explained above, it is easy to assemble the Global O-Ring and Seal (GOR) types as indicated in the following examples:
Type SC: Single lip w/spring, rubber covered O.D.
Type TC: Double lip w/spring, rubber covered O.D.
Type SB: Single lip with spring, metal O.D.
Type TB: Double lip with spring, metal O.D.
Type SA: Single lip w/spring, reinforced metal O.D.
Type TA: Double lip w/spring, reinforced metal O.D.
Our oil seals are available in both inch and metric sizes and are selected as follows:
Global O-Ring and Seal offers a full line of oil seal designs in all industry standard sizes. If you are a distributor or purchaser who may have need for our oil seal products, contact us today to speak with one of our technical sales associates, request a no-obligation quote, or place an order online from our extensive inventory.
Shop for Oil Seals
Did you miss the first part in our series? Be sure to click here to read part one.
PRESIDENT/OWNER:
Bill has served in the sealing industry for more than 25 years, and founded Global O-Ring and Seal nearly 10 years ago.
Oil seals work by squeezing and retaining lubricant in a thin layer between the lip and the shaft. Perfect sealing is ensured by the hydrodynamic action of the rotating shaft, which in turn produces a slight pump action.
As earlier said, oil seals perform some functions that ensure the functionality of mechanical equipment and extend their lifespan. And how they do this is by retaining lubricants at all cost and not making them escape no matter how high the pressure of the machine is.
The other way oil seals work is by stopping outboard materials that can damage the machine or contaminate its lubricant. The outboard materials that the oil seal will need to stop depend on the application. However, the most common kinds are dirt, moisture, and the particles produced during manufacturing.
Standard petroleum oil has a lifespan of 30 years at 86 degrees Fahrenheit if it's not
contaminated with moisture or any other particle. But the same oil will only last for a month at 212 degrees Fahrenheit if it's contaminated with little water. This is why the function of an oil seal is very evident whenever it's used.
Simple modifications to breathers and sight glasses can be beneficial, but shaft seals are just as important in this process. Labyrinth-type seals are common devices for contaminant exclusion, and when properly maintained, they can greatly influence the reliability of the components in which they are installed.
A comparison of various seal materials (Ref. Seal & Survive, Seal School Handbook)
Contact us to discuss your requirements of chinese engine oil seal. Our experienced sales team can help you identify the options that best suit your needs.
A seal's function is multifaceted. Not only is it attached to a machine to keep particles and outside contaminants from getting in, but it also must keep what is inside the machine - whether it is oil, process fluid or a barrier fluid - inside.
One study by Exxon Mobil showed that the amount of oil lost is four times the capacity of the machine. The need for minimizing leakage while prolonging the machine's operating life is more critical today, as the demands for reliability and the penalties for failure continue to rise.
Standard lip seals will limit certain contaminants from entering and restrict some leakage, but they are subject to failure, especially in systems with high pressure or extreme ambient conditions. One limiting factor of these types of seals is the construction material, with each elastomer having its own strengths and weaknesses.
The basic concept of labyrinth seals is to reduce contaminant ingression not only by restricting the clearance through which particles enter but also by creating areas of turbulent flow to exclude contaminants. These types of systems provide better particle exclusion and less lubricant leakage than standard lip seals, which contact the shaft and rub the surface during operation.
Shaft seals must be properly selected and maintained. Some seals do a good job of retaining oil or grease but do a lousy job of excluding contamination. Lip seals are a prime example, particularly the ones that are only directed inward. These types of seals tend to wear after a period of time because they make rubbing contact with the shaft. Eventually, the seals no longer function well from the standpoint of both oil retention and contaminant exclusion.
Lip Seal Labyrinth Seal
On the other hand, a labyrinth seal is non-contacting, so it will not have the wear-out condition. These seals are excellent for excluding particle contamination and moisture, even if there's a spray of water nearby. So both oil retention and contaminant exclusion are at a much higher level of performance compared to contacting mechanical seals and lip seals.
Of course, the disadvantage of using labyrinth seals is that they are more expensive. Generally, you will need to retrofit these on the equipment and will incur the cost of their installation. However, labyrinth seals will last longer and perform better.
Labyrinth seals are constructed in multiple pieces. One piece, known as the stator, is affixed to the machine and remains stationary. The other piece, called the rotor, is attached to the shaft and rotates with the motion of the system. The two pieces interlock to effectively seal out the majority of contaminants while holding in the lubricant or process fluid.
These types of seals are non-contacting, which means that the two opposing faces do not touch each other. They are also considered frictionless, as the rotor and stator are separated by a very small gap. In many instances, this gap can be as small as 0.003 inches, which equates to roughly 76 microns. This may sound like a large opening in comparison to the 1-micron lubricant film inside a rolling-element bearing, but because of the path that the contaminant must take to actually reach the bearing, this gap is more than adequate.
All contaminants trying to enter the bearing housing must go through the seal's maze (labyrinth) of turns and angles in order to reach the bearing. On the path through all of these turns, particles are constantly subjected to centrifugal forces due to the rotational motion of the shaft, and only a very small number make it through the entire length of the seal.
A variety of different labyrinth seals are available, from bronze and stainless steel to plastic. The construction of the seals may even change between brands, with some employing magnets and others simply using O-rings to provide the necessary seat for the housing and shaft. However, they all operate on the same principle and must be properly installed to work correctly.
When looking for options to boost reliability and minimize bearing failures, consider the seals that are in use. In areas of high airborne particulate matter or heavy washdown areas, a labyrinth-style seal can help limit the ingress of contaminants and prolong machine life. With proper lubrication and contaminant-exclusion devices, many bearings can come close to achieving their design life.
Spray shaft extensions with a suitable dry film or similar preservative.
For gearboxes with non-contact labyrinth seals, use internal vapor-phase rust protective coating instead of complete oil fill. Both oil wet and non-oil wet surfaces are protected by vapor-phase rust inhibitors.
Commercial vapor phase rust inhibitors include products such as Ashland Oil, Tectyl 859A or Cortec VP corrosion inhibitor. Typically, add 5 percent of the oil volume. Some inhibitors require the oil/inhibitor mixture to be heated and agitated in order to perform effectively.
This method may only be good for about six months and should be renewed if the storage period is longer. Another disadvantage is that it may cause incompatibility and foaming problems when filled with the service oil. Flushing is recommended before putting the gearbox into service.
EG&G Sealol, 'Seal & Survive,' Seal School Handbook, Revision 3.
Fitch, J.C., Scott, R., & Leugner, L. (), 'The Practical Handbook of Machinery Lubrication - Fourth Edition.'
Inpro/Seal, 'Bearing Isolators.'
Maintenance Technology (), 'Beyond Predictive Maintenance.'
Neale, M.J., 'Drives & Seals: A Tribology Handbook.'
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
'
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.'
Sealing edge This refers to the component of the oil seal that makes contact with the shaft.'
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'
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. wallMetal 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 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
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
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
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
No code: without minor lip
A: with minor lip
' Lip type codeNo 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 codeJ: 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:
If you are looking for more details, kindly visit high speed rotary shaft seals.