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
Dingtong Product Page
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
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
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.
Want more information on s type oil seal manufacturer? Feel free to contact us.
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:
Over it's lifetime, the SBC used 2 different Oil Pan Gaskets. The difference between them is the thickness of the gasket in the area that meets the timing cover:
A "thin seal" is about 1/4 in. thick.
A "thick seal" is about 3/8 in. thick.
The OEM oil pans made between and used the "thin seal."
The OEM oil pans made in and later used the "thick seal."
Most aftermarket oil pans use the "thick seal."
Even though there is a clean break in the year ranges, it's best to double check by measuring. Measure the height and width of the area of the oil pan shown below.
Height
Width
Gasket Type Required
2 1/4 in. 5 1/2 in. Thin Seal 2 3/8 in. 5 3/4 in. Thick Seal
Either way, if you use the wrong type of gasket, it will cause an oil leak.
If you use a thin seal when a thick seal is required, it will leave a gap around the timing cover.
If you use a thick seal when a thin seal is required, it will pull up on the corners of the front of the oil pan.
Anyone in the maintenance field who has repaired a pump or gearbox knows the one component that always seems to get replaced during a rebuild is the lip seal. It usually is damaged when being extracted or during disassembly. Perhaps the lip seal is the reason the piece of equipment was pulled from service due to leakage. Regardless, the fact remains that lip seals are vital machine components. They keep oil or grease in and help keep contaminants out. Lip seals seem to be on almost every piece of plant equipment, so why not take the time to learn how to correctly select and install them.
70%
of lubrication professionals say their plant uses lip seals to control contaminant ingression, based on a recent survey at MachineryLubrication.com
The primary purpose of a lip seal is to exclude contaminants while retaining lubricants. By nature, lip seals function by maintaining friction. They can be used in a variety of applications from slow-moving equipment to high-speed rotation and in temperatures from below freezing to more than 500 degrees F.
To be effective, a lip seal must maintain proper contact with its rotating counterpart. This will be influenced by proper selection, installation and care of the seal once it is installed. I’ve often seen a new lip seal start to leak as soon as it was put into service. This typically is due to improper installation. Other seals will leak initially but then stop leaking once the seal material has seated to the shaft.
Maintaining functional lip seals begins with the selection process. When choosing a material, you must consider the operating temperature, the lubricant in use and the application. The most common lip seal material is nitrile (Buna-N). This material functions well at temperatures of minus 40 degrees F up to 275 degrees F. Nitrile lip seals cover most applications in industry from new equipment to replacement seals. They have excellent resistance to petroleum oils, water and hydraulic oils, but what really sets these seals apart is their low cost.
Another affordable option is Viton. Its temperature range is minus 40 degrees F to 400 degrees F, depending on the specific compound. Viton seals provide good resistance to petroleum oils and can be employed with gasoline and transmission fluid.
Other seal materials that can be used with petroleum oils include Aflas, Simiriz, carboxilated nitrile, fluorosilicone, highly saturated nitrile (HSN), polyurethane, polyacrylate, FEP and silicone. All of these materials have specific applications and precise temperature ranges. Be sure to take into account the process and environment before selecting a seal material or making a switch, as the correct material can prevent a costly failure.
Once the seal material has been selected, the next step is to consider the seal’s construction. In the past, a simple lip seal consisted of a leather strap on a wheel axle. Today’s lip seals have multiple parts that affect how the seal performs. There are various contacting patterns as well as non-spring and spring-loaded seals. A non-spring seal generally will be less expensive and be able to retain viscous materials like grease at slow shaft speeds. Typical applications include conveyors, vehicle wheels and greased components. Spring-loaded seals are typically used with oils and can be found on a wide range of equipment.
The elastomer is not damaged (no nicks, scratches, cuts, etc.)
The case is not damaged (no nicks, cuts, dents, etc.)
The garter spring is properly placed (if used)
Wipe the seal and shaft of any debris
The assembly lube is compatible with the lubricant in operation
The case is of the proper specification
The elastomer is of the proper specification
The lip seal is pointing in the correct direction
The shaft is free of defects (no nicks, scratches, grooves, etc.)
The bore is free of defects (no nicks, debris, roundness, etc.)
There is adequate ventilation of equipment when stored or in operation
Proper installation tools are used to avoid damaging seals
Equal pressure is applied during installation to ensure the seal is not cocked
After the seal material and construction have been chosen, the lip seal must be installed correctly for it to perform. There are a number of products on the market dedicated to this single task. Most look like a socket set that will position the seal squarely into its bore. These tools can work well if selected carefully, but most off-the-shelf versions aren’t as effective, especially when a shaft is already installed.
For these instances, I prefer to use a pipe that is large enough to slip over the shaft and makes good contact with the lip seal’s outer shell. If you can find something that catches the outer casing, you can prevent damaging the inner metal ring that attaches to the lip seal material. Just be sure to set the seal in straight and at the correct depth. Failure to properly set the seal perpendicular to the shaft can cause immediate leakage.
If you have a used shaft, it likely has developed a wear ring where the old lip seal was placed. You should never set the contact patch to a previous contact point. If this is unavoidable, there are products that you can slip over the shaft to help with the damaged surfaces. This is usually quicker and more cost effective than replacing a shaft. Keep in mind that the lip seal will need to be resized for the added sleeve.
When installing lip seals, make certain the job is done correctly. I’ve seen guys install seals with a punch so they wouldn’t have to take the extra time to locate the right tool. One wrong thump from a hammer can tear sealing material, puncture the seal casing or push the seal through the housing.
Always take time when installing lip seals, and lubricate the shaft and seal adequately to prevent tearing or sticking. Also, verify that the lip seal is the correct size. There must be an interference fit in the bore and on the shaft. Not having the proper size can result in the seal rotating on the shaft or becoming dislodged from the equipment.
Check for cracked or deteriorated elastomer
Check for case damage
Check to see if the breather is plugged
Check equipment for excessive temperatures
Check for oil leaks around the lip seal
To help your lip seals stay as healthy as possible, you must keep your oil clean, cool and dry. Any contamination in the oil will get into the contact patch and deteriorate the shaft and elastomer. Likewise, the hotter the oil becomes, the more wear and tear will be exerted on the seal. Lip seals should also be kept as clean as possible. Painting over a seal or having dirt built up around it can create excessive heat and quickly degrade the elastomer.
If you’ve ever pulled out a lip seal and seen a groove cut into your shaft, this is probably due to particle contamination. Without good breathers, all the dust and dirt that gets into your equipment can destroy not only your bearings and gears but also your shafts and lip seals. Of course, it is always better to exclude contaminants than to try to remove them. Too tight of a fit between the lip seal and the shaft can also create a groove.
Excessive temperature is the leading cause of seal failures. As temperatures rise, the lubricating film becomes thinner, resulting in dry running conditions. Elevated temperatures can also lead to the elastomer cracking or blistering. Nitrile seal life decreases by a factor of two for every increase in temperature of 57 degrees F.
The oil level can be another factor in a lip seal’s lifespan if it is too low. In this situation, the seal will eventually become hard and not be able to follow the shaft, resulting in leakage.
Cold temperatures can cause seal embrittlement. Selecting the proper lubricant and seal material can help in these colder environments.
Seals may also fail due to shaft runout. This can be caused by misalignment, shaft imbalance and manufacturing inaccuracies, to name a few. Different elastomers will tolerate varying amounts of runout. Adding a garter spring will help with any runout that can be measured.
Excessive pressure is another potential cause of lip seal failure. If you’ve ever walked past a pump or gearbox and noticed oil leaking out the seal, the sump has somehow overpressurized and leaked to the point of least resistance. This can be attributed to clogged breathers or non-vented sumps. Applications with higher pressures should employ a special seal design.
Among the things to look for when inspecting lip seals include deteriorated or cracked elastomer. This is a telltale sign that heat is an issue. Also, verify that the lip seal is still in place. I’ve seen a few pumps that had the wrong seal installed. Upon startup, the vibration and movement caused the seal to come out of the bore and spin on the shaft.
Any oil leaks around the seal should be a red flag to investigate further. Worn seals can cause leakage, plugged breathers or damaged bearings that allow radial motion.
When analyzing any lip seal failure, look at the seal, shaft and bore. While inspecting the shaft, you typically will see a contact or wear zone where the lip seal was riding. This will appear as a black scuffmark where the elastomer has transferred to the shaft.
Remember, in order to keep your lip seals in good operating order, you must maintain the sump. Cover all seals before painting, keep the oil at the proper level, make sure oil coolers are functioning correctly, and select the right seal design and material. If you are proactive in your approach to rebuilding and installing equipment, you can give your lip seals and machinery a fighting chance at survival.
Skeleton oil seals, also known as radial shaft seals or lip seals, are crucial components used to prevent leakage of lubricants and protect mechanical systems from contaminants like dust, dirt, and moisture. These seals are widely used in industries like automotive, machinery, and manufacturing, and choosing the right oil seal is essential for optimal performance and longevity. Here's a detailed guide to help you choose the correct skeleton oil seal for your specific application.
The first step in choosing a skeleton oil seal is to fully understand the specific application for which it will be used. Factors like operational speed, temperature, pressure, and the type of fluid being sealed are important considerations.
- Operating Conditions: Determine the environment in which the oil seal will operate. Consider exposure to extreme temperatures, the presence of chemicals, and whether it will be used indoors or outdoors.
- Fluid Type: Identify the type of fluid the seal will be in contact with. This could include oils, grease, or other types of lubricants. Ensure the seal material is compatible with the fluid.
- Pressure and Speed: Know the maximum operating pressure and rotational speed of the shaft. Some seals are designed to handle high-pressure environments, while others are suitable for low-pressure applications.
Rubber Skeleton Oil Seal
Skeleton oil seals are available in various materials, each with specific properties that make them suitable for different applications. The choice of material is critical as it affects the seal's resistance to heat, chemicals, and wear.
- Nitrile Rubber (NBR): The most common material for oil seals, NBR offers excellent resistance to oil and abrasion. It is suitable for temperatures ranging from -40°C to +120°C and is ideal for general-purpose sealing in industrial and automotive applications.
- Fluorocarbon (Viton): Viton seals offer higher resistance to heat and chemicals, making them suitable for high-temperature applications (up to 200°C). They are also resistant to a broader range of chemicals and are ideal for use in environments with aggressive fluids.
- Silicone Rubber: Silicone seals offer good flexibility at both high and low temperatures, but they are not as resistant to oil as NBR or Viton. Silicone is often used in applications where temperature resistance is more important than oil resistance.
- Polyurethane (PU): Known for its exceptional wear and abrasion resistance, polyurethane is often used in applications where the seal is exposed to high levels of friction and stress.
- PTFE (Teflon): PTFE oil seals offer excellent chemical resistance and operate well in a wide temperature range. They are commonly used in applications involving aggressive fluids or extremely high temperatures.
Rubber Skeleton Oil Seal
The lip design of the oil seal plays a crucial role in how well it prevents leakage and withstands pressure. Skeleton oil seals are available in different lip designs to suit varying applications.
- Single Lip (SL): Single-lip oil seals are designed to prevent leakage from the inside of the system. These are commonly used in general sealing applications where there is low pressure and no external contaminants.
- Double Lip (DL): Double-lip oil seals have an additional lip that provides extra protection against external contaminants like dust and dirt. These seals are ideal for outdoor applications or where the system is exposed to debris.
- Triple Lip (TL): These seals are used in heavy-duty applications where both high pressure and exposure to contaminants are concerns. The additional lips provide a more secure seal and extended durability.
Getting the correct size is essential to ensure a proper fit and effective sealing. Skeleton oil seals are typically specified by their inner diameter (ID), outer diameter (OD), and thickness or width.
- Inner Diameter (ID): This is the diameter of the shaft on which the seal will be installed. Measure the shaft accurately to avoid leakage or seal damage.
- Outer Diameter (OD): This is the diameter of the bore or housing where the seal will be installed. The outer diameter should be slightly larger than the bore to create a tight fit.
- Width: The width of the oil seal should match the depth of the groove or housing where it will be seated. An incorrect width can lead to misalignment and inadequate sealing.
It's important to follow the manufacturer’s specifications for the proper size. Using calipers or other precise measuring tools can help ensure an accurate fit.
Rubber Skeleton Oil Seal
The temperature range that the oil seal will be exposed to is another key factor. If the temperature exceeds the seal's capacity, it can lead to degradation, hardening, or softening of the seal material, leading to premature failure.
- Low Temperatures: For cold environments, choose materials like silicone that remain flexible even at low temperatures. NBR seals can handle cold temperatures but are not as effective in extreme cold.
- High Temperatures: For high-temperature applications, consider materials like Viton or PTFE that can withstand heat without losing their sealing properties.
Always ensure the material and design you select are capable of operating at the upper and lower limits of your application’s temperature range.
While most skeleton oil seals are designed for low-pressure applications, some seals are specifically designed to handle moderate to high pressure. If your application involves significant pressure levels, be sure to choose an oil seal that can withstand the force without failing.
- Low-Pressure Seals: For most general-purpose applications, standard skeleton oil seals can handle low pressures effectively.
- High-Pressure Seals: For higher-pressure environments, choose seals with reinforced lips or specialized designs that can handle the extra force.
The condition and speed of the shaft on which the oil seal will be mounted directly impact the seal’s performance. A worn or rough shaft surface can quickly damage the seal, leading to leakage.
- Shaft Surface: Ensure the shaft surface is smooth and free from grooves, scratches, or other imperfections that can compromise the seal. A polished shaft is ideal for maximizing the lifespan of the oil seal.
- Rotational Speed: Oil seals are designed to handle certain speeds. High-speed shafts require seals that can withstand the friction generated by rapid rotations without overheating or wearing out quickly.
If your application is exposed to harsh environmental conditions, dust, or debris, consider using double-lip or triple-lip skeleton oil seals. The extra lips provide additional protection, preventing contaminants from entering the system and compromising the lubrication.
For heavy-duty applications, seals with dust flingers or wipers may also be an option to keep contaminants at bay.
Some skeleton oil seals come with extra features designed to enhance performance and durability, especially in demanding applications. These include:
- Spring-Loaded Seals: Some seals feature a spring that helps maintain a tight fit around the shaft, ensuring consistent pressure and preventing leaks, even as the seal wears down over time.
- Labyrinth Seals: These seals have a unique design that provides extra resistance to contaminants, making them ideal for applications involving extreme dirt or dust exposure.
Finally, when choosing a skeleton oil seal, consider both the cost and the availability of spare parts. While it’s important not to compromise on quality, balance your budget with the specific needs of your application. Additionally, ensure that replacement seals are readily available for maintenance purposes.
Choosing the right skeleton oil seal involves understanding your application’s specific requirements, including the environment, shaft speed, pressure, and type of fluid being sealed. Consider the material, lip design, and seal size carefully, and ensure that the seal you select is suitable for the operating conditions. A high-quality, well-chosen skeleton oil seal will ensure efficient operation, extend the lifespan of your machinery, and reduce downtime due to leaks or failures.
Find premium O-rings in all sizes and materials. Perfect for industrial sealing. High-quality Seals for various industries.
Are you interested in learning more about s type oil seal? Contact us today to secure an expert consultation!