How Skeleton Oil Seal Types are Classified and How to Determine the Proper Size?

The model designation and selection of skeleton oil seals are not as complicated as they may seem. Most naming conventions follow GB/T 9877, ISO 6194, and common industry practices.
A typical model format is: Type – (Inner Diameter × Outer Diameter × Width) – Material.

Common Structural Types (Compatible with most major brands such as Shanfeng (NQKSF), CFW, SKF, etc.)

Meaning of Letter Codes
TC Type: Double‑lip seal with a primary lip for oil retention and a secondary lip for dust exclusion. Suitable for general machinery.

TB Type: Enhanced dust protection; ideal for construction machinery or dusty environments.

TA Type: High‑pressure design for hydraulic systems and other high‑pressure applications.

SC Type: Single‑lip rubber‑covered seal for clean environments.

SB Type: Single‑lip seal with a metal outer case, offering high dimensional accuracy and stable press‑fit installation.

TCV Type: Double‑lip seal with reinforced dust protection for dusty or muddy conditions.

TCN Type: Double‑lip, low‑friction design suitable for high‑speed and low‑energy‑consumption applications.

Meaning of Numbers
Numbers indicate the seal’s dimensional parameters, typically:

70 × 90 × 10 = Inner diameter 70 mm, outer diameter 90 mm, width 10 mm.

Selecting the Correct Seal Based on Shaft and Housing Dimensions
Seal selection begins with determining the correct inner and outer diameters based on the shaft and housing, followed by choosing the appropriate material and type for the operating environment.

Accurate Measurement
Precise measurement is essential. Use calipers or other accurate tools.

Shaft diameter (d): The seal’s inner diameter should be slightly smaller than the shaft diameter to ensure proper interference and sealing.

Housing bore diameter (D): The seal’s outer diameter should match the housing bore, typically with slight interference.

Housing depth (H): Choose a seal width that fits the available installation space and meets sealing requirements.

Choosing the Material
NBR (Nitrile Rubber): Good wear and oil resistance; suitable for general applications (–40 to 125°C).

HNBR (Hydrogenated Nitrile Rubber): Improved heat and aging resistance; suitable for high‑temperature environments (–50 to 150°C).

FKM (Fluorocarbon Rubber): Excellent resistance to chemicals and oil; suitable for corrosive or high‑temperature environments (–20 to 250°C).

Choosing the Seal Type
TC: General‑purpose double‑lip design.

TB: Enhanced dust protection for dusty environments.

TA: High‑pressure applications such as hydraulic systems.

SC: Single‑lip design for clean environments.

SB: Metal outer case for precise press‑fit installation.

TCV: Suitable for dusty or muddy conditions.

TCN: Ideal for high‑speed, low‑friction applications.

Key Considerations During Selection
Operating environment: Consider temperature, pressure, medium, and contamination level when choosing material and type.

Installation requirements: Ensure proper fit between the seal and shaft/housing to prevent leakage caused by incorrect installation.

Maintenance cost: Selecting durable materials and structures reduces maintenance frequency and long‑term cost.

Selecting a skeleton oil seal requires a balanced consideration of dimensions, materials, and operating conditions. Start by confirming the shaft and housing dimensions, then choose the appropriate material and structural type based on the environment and performance requirements. Proper installation and maintenance are equally important to ensure long‑term sealing performance.

If you have specific application parameters, I can help you refine the selection further.