Ways to Measure and Choose Oil Seals for Industrial Applications

Oil seals are used in several industrial applications to protect shafts and bearings from oil, grease, contamination, and dirt. They comprise an outer and an inner circular rings. The outer ring or disk is made of metal, while the inner one is made of rubber and hence is flexible. It is stuck onto the outer ring with the help of a chemical adhesive. There are oil seals with single lip as well double lips. The sizes of these seals depend on application requirement, and hence it is measure the inner and outer diameters, width, and so on. Also, it is crucial to choose the right type of oil seal for every application. This post discusses the way to measure and choose the oil seal for your application.

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How to Choose the Right Oil Seal Type?

You may have to choose or identify the oil seal type in case of either a new equipment fitment or as a replacement for the damaged one. Here are a few pointers to identify the right seal type.

• Primarily, there are single lip and double lip oil seals. The single lip is the immersed at the bottom for which the inner diameter needs to be considered.
• Double lip oil seals have an extra lip at the top which protects from external contamination, dirt, and so on.
• Pressing along the line of the inner diameter at the top may help determine whether the oil seal is single lip or double lip.
• Check the code of the lip seal given by the manufacturer or look for a reference guide for further information regarding the oil seal type. This is because there are several types of single lip as well as double lip seals with varied configurations such as type A, B, or C single lip and type BO, ADL, double lip, and so on.
• Type B seals have their outer diameter made of metal, while in case of type A it is made of rubber. In type C, there is reinforced metal added for structural stability. Likewise, there are several types of materials and their permutations and combinations.
• All of these oil seals based on their materials have specific physical and chemical properties, and accordingly find applications in diverse industries. For instance, type C single lip offers structural stability and hence finds use in heavy engineering. Type A made of rubber has amazing resistance to heat, chemicals, and so on. Hence, they find application in industries where there is exposure to chemicals, abrasion, and elevated temperatures.
• Before you choose the type of oil seal, it is essential to measure it, which is discussed in the next section.

 

How to Measure Oil Seals?

Oil seals are typically used as seals in moving parts that prevent friction as well as mixing of liquids or other elements. The oil seeps between the lip and shaft and that lifts up the lip. This creates the required gap between the lip and shaft as they should never come in contact with each other. This is basic working mechanism of oil seals. When replacing these oil seals, it is essential to measure them since they have different dimensions based on the application they are fitted in. Here are some pointers regarding their measurement.

• While visual inspection may offer some clue, it may not be accurate. Hence, measuring the inner and outer diameter with the help of calipers is important.
• Their measurement is much like O-rings, wherein, height, lip, type, inner and outer diameter are important factors. Material is also a factor to be considered although it cannot be measured.
• Take at least three readings, preferably with a Vernier caliper. Consider the average reading if there is negligible difference among the values.
• Measure the bearings and also consider the gaps.

If you want to buy

Related Post

If you want to buy automotive oil seals or industrial oil seals these identification pointers may be useful. However, ensure you source them from reliable manufacturers and suppliers that can ensure leak proof seals. If you are looking for food or pharmaceutical applications, ensure the industrial oil seals are FDA approved. SSP Manufacturing Inc. has a market presence of more than three decades and offer premium quality custom oil seals for a number of industrial applications.

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

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

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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

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:

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