Oil seals are essential components used broadly in machinery as sealing devices.

JTEKT's oil seals are featured in our catalog, Oil Seals & O-Rings. However, due to the extensive use of technical terms and the catalog's length, users often find it challenging to navigate.

This series aims to simplify the following topics:

• The structure, functions, and types of oil seals
• How to select the appropriate oil seal
• Handling seals, and identifying and addressing oil seal failures

Contact us to discuss your requirements of oil seal companies. Our experienced sales team can help you identify the options that best suit your needs.

1. What are oil seals?

Oil seals are crucial for preventing leakage of lubricants from within machinery, and stopping dust and contaminants from entering.

• Prevent leakage of sealed lubricant from inside
• Prevent entry of dust and foreign matter (dirt, water, metal powder, etc.) from outside

Sealing devices are categorized into two types: contact and non-contact. Oil seals are a predominant kind among 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 tailored to match specific machines and substances. The figure below illustrates the structure and the names of various components of a typical oil seal:

Figure 2: Typically shaped oil seal and component nomenclature

Table 1: The functions of the various components

No.

Name

Functions

1. Main lip – This component comes in full contact with the shaft surface ensuring excellent sealing performance.

2. Minor lip – Prevents entry of dust and contaminants. It retains lubrication between the primary and minor lips.

3. Sealing edge – Wedge-shaped to ensure a secure seal at the shaft surface.

4. Spring – Enhances the sealing performance by applying force to the main lip, ensuring a tight grip on the shaft.

5. Metal case – Provides rigidity, securing the seal on the housing and simplifying handling and installation.

6. O.D. surface – Secures the oil seal to the housing, preventing leakage and excluding contaminants.

7. Fluid side face – Forms a gasket seal when compressed.

8. Air side face – The back face, vertical to the shaft's centerline, that doesn’t contact the sealed substance.

* "KOYO" is a registered trademark of JTEKT.

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

Oil seals are categorized by O.D. wall material, lip type, and whether they include a spring. ISO 6194-1 and JIS B 2402-1 standards specify major oil seals. Below are tables that detail the common types and their features.

Table 2 a): Common types of oil seals (with spring)

Table 2 b): Common types of oil seals (without spring)

Table 3: Features of each seal type

1. With spring type – Provides stable sealing performance.

2. Rubber O.D. wall type – Stable sealing around the O.D. surface.

3. Metal O.D. wall type – Improved fitting retention between the seal O.D. and housing bore.

4. Metal O.D. wall type (with reinforcing inner metal case) – Protects the main lip.

5. With minor lip type – Shields against contaminants like dust on the air side face. Table 4: JTEKT oil seal type codes and corresponding ISO and JIS standards

40169330 - Gaskets, washers and other seals: Rubber ...

2) Special seal types and their features

JTEKT provides specialized seals for diverse applications. Below table lists major special seals along with their shapes and features.

Table 5: The major special seals, their shapes, and their features

Helix Seal – Improved sealing due to hydrodynamic ribs on the air side face of the lip.

Perfect Seal – Dual-direction hydrodynamic ribs, excellent in both rotational directions.

Super Helix Seal – Two-step rib configuration ensuring enhanced sealing even if the first rib wears out.

Seal with Side Lip – Large side lip that prevents dust and water entry.

3) Seal numbering system

Figure 5 explains the JTEKT seal numbering system. Seal numbers combine:

• (1) Seal type code
• (2) Spring code
• (3) Lip type code
• (4) Dimensional numbers
• (5) Special type code

Figure 5: JTEKT seal numbering system

Table 6: Codes and numbers used in seal numbers

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, suitable for shaft diameter of ϕ45 mm.
Housing bore number: 70, suitable for housing bore diameter of ϕ70 mm.
Width number: 8, the seal width is 8 mm.

5. Special shape code
J: Additional code when two or more seals share the same basic codes/dimensions.

4. Example of the applications of seals

Oil seals are employed in numerous machines.

1) Oil seals for cars

Oil seals are extensively used in cars, with specific seals employed in various parts. See figure below for details.

Figure 6: Oil seals for cars

2) Oil seals for steel production equipment

These seals find significant use in steel production equipment, particularly in rolling mills. See below:

Figure 7: Oil seals for steel production equipment (rolling mill)

5. Conclusion

Oil seals are key contact sealing devices. They have two main functions:

• Prevent leakage of lubricants or other sealed substances
• Block the entry of dust and foreign matter from outside

Oil seals come in diverse shapes to match different machines or substances they are sealing. Proper selection is critical for optimal design and function of machinery. In the next part, we will explore the key criteria to consider when selecting your oil seal.

If you have any technical questions about oil seals or feedback on our "Bearing Trivia" pages, don't hesitate to contact us using the provided form.

Summary

• Oil seals consist of three core components: the sealing element (lip), the metal case, and the optional garter spring, each playing a crucial role.
• Selecting an oil seal requires assessing design, application needs, shaft diameter, bore diameter, sealing material, and environmental conditions.
• Regular maintenance, such as proper lubrication, inspections, and replacements, ensures prolonged oil seal longevity and efficiency, enhancing overall machine performance.

Introduction

In the world of machinery, where equipment is in constant motion, oil seals play a vital role. Known as shaft seals, they are essential components in various industrial equipment, preventing lubricant leaks and blocking contaminants. This detailed guide will help you understand the importance of oil seals, their construction, different designs, and key considerations for selecting the right seal for your application.

Purpose of an Oil Seal

Oil seals serve three critical roles in machinery:

• Prevent leaks of lubricants or fluids, ensuring smooth equipment operation.
• Maintain lubricants within the machinery, reducing maintenance frequency.
• Act as a barrier against contaminants, protecting internal components from damage.

Construction of an Oil Seal

Oil seals are meticulously engineered and consist of two main parts: the sealing element and the metal case, along with an optional garter spring for additional support.

Sealing Element

The sealing lip forms the oil seal's interior. It's made from various materials based on application needs:

• Nitrile Rubber (NBR): Commonly used for its heat resistance and compatibility with oils and hydraulic fluids. Suitable for temperatures between -40 to 248°F (-40 to 120°C).
• Polyacrylate Rubber (PA): Better heat resistance, suitable for high-speed environments, performing well between -4 to 302°F (-20 to 150°C).
• Silicone Rubber (SI): Handles extreme temperatures (-58 to 356°F, -50 to 180°C), excellent for crankshaft seals. However, it's not ideal for oxidized or hypnoid oils.
• Fluorocarbon Rubber (FKM): Known as Viton®, it offers exceptional chemical resistance and high-temperature performance.

Metal Case

The metal case provides structural support. Material choice depends on the operational environment:

• Carbon Steel: Commonly used with standard lubricants.
• Stainless Steel: Ideal for applications requiring water, chemical, or corrosion resistance.

Outer metal cases may have protective finishes to prevent rust and aid in identification.

Garter Spring

Included in some designs, it applies pressure to the sealing lip, ensuring a tight seal. The spring material must withstand environmental factors.

Standard Sealing Lip Designs

Lip designs vary to suit different applications:

• Single Lip: Includes a garter spring, suitable for low-pressure environments.
• Double Lip: Additional lip for extra protection against dust and dirt, suitable for low-pressure environments.
• Dual/Twin Lip: Two identical lips for separating liquids, requires lubrication between lips.
• Single Lip, No Spring: Used for sealing non-pressure media like grease.
• Double Lip, No Spring: Springless design protecting against internal and external contaminants.

Standard Sealing Case Designs

Common case designs include:

• Type A: Metal case with reinforced plate, ideal for larger shafts or special rubber compounds.
• Type B: Metal case for use with smaller shafts and steel/cast iron housings.
• Type C: Rubber-covered case preventing rust and suitable for damaged or soft material housings.

Factors in Oil Seal Selection

Consider the following when selecting an oil seal:

1. Type: Combination of lip and case design.
2. Shaft Diameter: Diameter where the seal will operate (I.D.).
3. Bore Diameter: Diameter of the bore housing (O.D.).
4. Width: Thickness of the oil seal.
5. Sealing Material: Must withstand operating conditions.
6. Environmental Factors: Include dirt, water, temperature, and shaft speed.
7. Lubrication: Compatibility with the seal material.
8. Spring Material: Must resist environmental factors.
9. Application Requirements: Specific needs, like FDA standards for food processing.

Failure Modes of Oil Seals

Recognizing oil seal failure modes is essential:

• Excessive Wear: Due to inadequate lubrication or rough shaft surface.
• Hardening or Cracking: Caused by prolonged exposure to high temperatures.
• Chemical Erosion: Incompatible chemicals or lubricants causing material degradation.
• Improper Installation: Leading to premature failure or misalignment.
• Excessive Pressure: Leading to seal deformation.

Maintenance and Inspection of Oil Seals

Regular maintenance prolongs oil seal life:

• Regular Lubrication: Minimizes friction and wear.
• Routine Inspections: Identify early signs of failure.
• Proper Cleaning: Prevents dirt from damaging the seal.