The structure, functions, and types of oil seals

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

The company is the world’s best oil seal manufacturing process supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

 

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)

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

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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:

 

 

 

Do I need a thin or thick oil pan gasket?

 

Do I need a thin or thick oil pan gasket?

 

Explanation & Recommendations

 

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.

Which pans use which gaskets?

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

 

Why does it matter?

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.

Lip Seals - A Practical Guide

 

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

Purpose of Lip Seals

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.

 

Selecting a Lip Seal

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.

Lip Seal Construction

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.

Lip Seal Installation Checklist

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

Installation

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.

Lip Seal Inspection Checklist

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

Maintaining Lip Seals

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.

Failure Causes

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.

How to Inspect a Lip Seal

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.

About the Author

If you deal with rotatory shaft equipment, you would probably be having rubber seals in your mechanical assembly. For any manufacturing company, optimal functionality, efficiency, and long service life are essential to your success in the market. A component that is majorly underappreciated within a machine assembly, would be oil seal. 

Shaft seals are used to prevent lubricant leaks like oil or grease and protect machinery from dirt, dust, and water&#;which makes them invaluable to industrial operations. In this post, we will dive deeper into oil seals and discuss everything that one must know, such as what it is, how it works, types, applications, and what to keep in mind when buying oil seals. 

What are rubber oil seals? 

Rubber oil seals are placed between moving and static parts of mechanical equipment to prevent damage caused by moisture, contaminants, etc. Also known as rotatory shaft seals, grease seals, fluid seals, lip seals, and dirt seals; oil seals play an important role in closing the gaps between moving and stationary parts of machines. 

Their main purpose is to retain or separate fluids from mixing and escaping the gauge, as well as stop moisture, abrasives, corrosive materials, and foreign contaminants from entering the parts, thereby ensuring maximum machine efficiency. Moreover, shaft rubber seals help prevent lubricant leakage at high pressure, for instance, when the machine is working at an extremely high pace. 

How does rubber oil seal work? 

Oil seals work by retaining lubricant in a thin layer between the lip and the shaft. These seals are attached to the bearing, with their lip pressing against the rotating shaft and the casing resting against the housing to hold the seal in place. 

Oil seals perform some functions that ensure functionality at all costs and they do this by retaining lubricants at all costs and not making them escape no matter how high the pressure is.  Whenever an oil seal fails, it creates seal leakage allowing abrasives, corrosive moistures and sediments to enter machines. Oil seals are especially used in equipment that has rotating, oscillating, and reciprocating shafts &#; pumps, pistons, etc. 

Different types of seals offered by rubber products manufacturers in India include &#; Single and double lip oil seals, metal cased, external and internal oriented oil seals, and spring-energized oil seals and you can pick the one that best suits your industry requirements. 

Applications of Oil Seals 

Practically, all machine equipment including assembled machines, car engines, and PTFE machined parts use these oil seals to prevent harmful interactions that could possibly result in damaged parts. They are used in the assembly of Elevators, conveyor belts, engines, grinding mills, pipelines, wind turbines, and more. 

When equipment is under high pressure, lubricants tend to escape, and dry parts clash. Oil seals help prevent this by sealing holes where lubricants can leak out. rubber seals are designed to offer optimum sealing performance and extreme durability even under high-peripheral speed. They are lightweight, compact, and exhibit high self-lubricating properties. Oil seals are manufactured with high-grade materials and last long without showing any signs of hardening, softening, or aging. 

Moreover, oil seals are widely used throughout the aerospace industry in both space exploration and aviation applications. Sujan Industries manufactures all aircraft rubber items including O-rings, Gaskets, Seals, Pistons, Grommets, Washers, and Protective Boots & Bellows. In the aviation sector, pneumatics and hydraulics are used to operate components like landing gear and wing flaps. Rubber gaskets are needed in these systems to keep dust and air out while ensuring aircraft components run effectively.

How to Choose the Right Oil Seal 

Picking the right type of oil seals is crucial for the proper functioning of machines because in some situations not all types can fit to work on certain machines. 

There are quite a few factors to put into consideration when you&#;re choosing the right oil seal for your machine. Some of these factors include &#; dimensions, pressure, temperature, type of fluid, lubricant, shaft speed, shaft and bore tolerance, and more.

The capacity of oil seals to handle different intensities of pressure varies with their composition and application, so it is important to understand the compression set of your equipment. Just like the pressure, the temperature that your oil seal will be operating in must be known to be able to choose one that can withstand the working temperature. 

Likewise, different types of fluids like grease, water, oil, fuels, etc. will come into contact with oil seals. So, knowing what type of fluids will be in constant contact with oil seals will help you choose the one capable of withstanding the surrounding conditions. When we talk about lubricants, seals always perform well when lubricated, however, in some machines there are dry spells.  If you are a supplier of aftermarket parts in India or a user looking for oil seals in the aerospace industry, your search might end with Sujan Industries. 

Wrapping Up

Oil seals are critical to a machine&#;s functionality. A machine&#;s oil seals are critical to its functionality. Picking the right seal for your machine is vital as it not only guarantees the optimum performance of applications but also ensures a safe working environment for years to come. With so many rotary shaft seal options available, it can be hard to know which one to choose for your machine! Contact us today to speak to one of our experts and pick the best one for you.

If you want to learn more, please visit our website rubber oil seals manufacturers.