High Quality Skeleton Oil Seal for Automotive and Machinery Applications

In sealing applications, skeleton oil seals are widely used in automobiles,
industrial equipment, and various transmission systems. Practical experience
shows that sealing performance depends not only on rubber materials and
structural design, but more critically on a clear understanding of the lip
sealing mechanism and a well-calculated interference fit.

This article provides a systematic explanation of the sealing principles and
lip interference design of skeleton oil seals from an engineering
perspective, offering guidance for selection and design.

Structure and Key Parameters of skeleton oil seals

Sealing Structure Parameters

Structurally, skeleton oil seals achieve sealing primarily through the
interaction between the lip and the rotating shaft. Key design parameters
include:

Lip Type:

Single lip: Suitable for general sealing needs

Double lip (with dust lip): Designed for environments with external
contaminants such as dirt, moisture, or mud

Spring Configuration:

With spring (e.g., TC, TB types): Provides continuous radial preload, ideal
for high-speed or high-pressure conditions

Without spring: Used in low-speed, low-pressure, or static sealing scenarios

Lip Angle and Thickness: These directly affect the oil film’s ability to
form and return, and are critical for achieving dynamic sealing performance.

Together, these structural parameters determine the seal’s adaptability to
various operating conditions.

Definition of Lip Interference

Lip interference refers to the dimensional difference between the oil
seal’s inner diameter in its free state and the actual operating shaft
diameter.

Once installed, the lip undergoes elastic deformation due to interference,
generating continuous radial contact pressure on the shaft surface—this is
the foundation of effective sealing.

For standard rotary sealing applications, the following reference ranges are
commonly used:

Radial interference (single side): approximately 0.2 to 0.4 mm

Corresponding diameter interference: approximately 0.4 to 0.8 mm

Exact values should be adjusted based on shaft diameter and operating
conditions.

Fit Parameters and Operating Influences

Beyond the seal itself, shaft and system conditions also significantly
affect sealing performance. Key factors include:

Shaft Surface Roughness: Typically controlled within Ra 0.2 to 0.8 μm

Shaft Diameter Tolerance and Concentricity

Operating Speed and Temperature Range

Typical Application Scenarios

skeleton oil seals are commonly used in rotary sealing environments such as:

Automotive engines, transmissions, and electric drive systems

Industrial motors, pumps, and fans

Gearboxes, drive shafts, and mechanical shaft ends

In these applications, the seal must not only prevent lubricant leakage but
also allow a stable micro oil film to form between the lip and shaft. This
reduces friction and wear, ensuring long-term reliability.

Sealing Mechanism and Common Issues

Sealing Principle of skeleton oil seals

skeleton oil seals do not achieve sealing by simply compressing the lip
tightly. Instead, sealing is accomplished through the coordinated action of
several mechanisms:

Lip interference generates initial contact pressure

Shaft rotation forms a thin lubricating oil film between the lip and shaft

The oil film reduces friction and creates an inward pumping effect

Spring-loaded designs provide continuous compensation, maintaining stable
contact

This oil-film-based dynamic sealing mechanism is the key to long-term,
stable operation.

Typical Problems Caused by Improper Interference

In practice, incorrect interference selection can lead to a range of issues:

Excessive Interference:

Increased friction and operating temperature

Accelerated lip wear

Early failure under high-speed conditions

Insufficient Interference:

Inadequate contact pressure

Unstable oil film

Leakage or oil flinging

Therefore, interference must be carefully balanced to ensure both sealing
performance and service life.

Key Factors Affecting Interference Selection

During engineering design and selection, interference should be determined
based on a combination of the following factors:

Shaft Speed: Higher speeds typically require reduced interference to
minimize friction and heat

Operating Temperature: High temperatures soften rubber, so interference may
need to be increased

Sealing Medium: Low-viscosity fluids demand more stable contact pressure

Rubber Material:

NBR (Nitrile Rubber): Suitable for standard interference designs

FKM (Fluororubber): Offers higher hardness and temperature resistance,
requiring more precise interference control

Spring Inclusion: Seals with springs are less dependent on the rubber
body’s interference and offer greater adaptability

Through a combination of well-designed lip interference, stable dynamic oil
film formation, and appropriate spring compensation, skeleton oil seals
achieve reliable sealing on rotating shafts. Lip interference is not a fixed
value—it must be determined based on shaft dimensions, operating
conditions, and material properties.

A scientifically grounded and well-balanced interference design is essential
for achieving both sealing reliability and optimal service life.

Minimum Order: 1000 pieces

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