Single Lip Oil Seals - Durus

What Is a Single Lip Oil Seal?

A single lip oil seal contains one elastomer sealing lip that contacts the rotating shaft, backed by a steel garter spring that maintains constant radial loading against the shaft. No additional dust lip extends outboard of the primary lip. The simpler design reduces total friction (less power loss) and is preferred where the seal's outboard side faces a clean environment.

Single lip seals are identified in Durus part numbers by codes like S (in SB, SC types), B (in standalone B types), or by the lip configuration metafield. The product description explicitly states "Single Lip" where it applies.

When to Choose Single Lip

• Inside a sealed gearbox - Multiple seals in series; outer seals exclude dust, inner seals only need to retain oil
• Clean operating environment - Indoor equipment with no airborne dust or moisture
• Low-friction requirement - Single lip generates less shaft drag than double lip
• High-speed shafts - Lower lip count reduces heat generation at high RPM
• Cost-sensitive applications - Single lip seals are typically slightly less expensive than equivalent double lip

Single Lip vs Double Lip

Browse double lip oil seals for applications requiring dust exclusion, or browse all Durus oil seals for the complete catalog.

Related Seal Types

Frequently Asked Questions

What is the difference between single lip and double lip oil seals?

A single lip oil seal has one primary sealing lip that contacts the rotating shaft. A double lip seal adds an auxiliary dust lip outboard of the primary lip, creating a small grease-packed cavity that excludes dust and dirt. Single lip is preferred for clean environments and reduces friction. Double lip is preferred for dirty environments where contamination must be kept out of the bearing or gearbox.

When should I use a single lip oil seal?

Use single lip when the outboard side of the seal faces a clean environment - typical examples include interior seals on multi-seal gearbox configurations, hydraulic motor output shafts inside closed housings, indoor process equipment without airborne dust, and applications where minimizing friction is more important than dust exclusion. For outdoor equipment, dirty industrial environments, or any application with potential contamination, choose double lip instead.

Do single lip oil seals leak more than double lip?

No - both single and double lip seals provide effective primary sealing through the lip-spring assembly. The difference is contamination exclusion, not oil retention. In a clean environment, a single lip seal retains oil just as well as a double lip seal. Single lip seals do generate less friction and heat than double lip, which can improve seal life in high-speed applications by reducing thermal degradation of the elastomer.

What Durus seal types are single lip?

Durus single lip configurations include SB (Type B case with S-style lip), SC (Type C rubber-coat case with S-style lip), TB (Type B with standard single sealing lip in some variants), and SA (Type A with spring-loaded single lip). The product description metafield explicitly identifies lip configuration. When in doubt, check the lip configuration field on the product page or call (888) 203-2358 for confirmation.