Oil Seals

Verified by Mel Sykes, Industrial Supply Chain Specialist - April 2026

Specification	Details
Types	Single lip, double lip (with dust lip), spring-loaded
Materials	Nitrile (NBR), Viton (FKM), PTFE, silicone
Standards	ISO 6194, DIN 3760/3761
Shaft sizes	6mm to 500mm

What are Oil Seals?

Oil seals prevent lubricants from leaking out of mechanical systems while keeping contaminants like dust and moisture away from the moving parts inside machinery. They play a critical role in maintaining system efficiency and preventing costly breakdowns.

Oil seals come in various types, each designed to meet specific performance criteria. Single lip seals have one sealing edge, making them suitable for light-duty applications with minimal contamination. Double lip seals feature two sealing edges-one inner lip that faces the lubricant side and an outer lip that faces the environment-making them ideal for harsher conditions. Spring-loaded oil seals incorporate a spring to maintain contact between the seal lip and shaft, enhancing durability and reliability.

Types and variants

Oil seals are available in different configurations to suit various mechanical requirements:

• Single Lip Seals: These seals have one sealing lip that contacts the rotating shaft. They're suitable for low-pressure applications where contamination is minimal. Typical dimensions range from 6mm to 500mm.

• Double Lip Seals (with dust lip): Designed with two lips, these seals offer better protection against contaminants and higher pressures than single lip seals. The inner lip faces the lubricant side, while the outer lip protects against environmental factors like dust and moisture.

• Spring-loaded Oil Seals: These seals include a spring that keeps the sealing lip in contact with the shaft, even under high speeds or temperatures. This design ensures consistent sealing performance over long periods of operation.

Materials and specifications

Oil seals are manufactured from different materials to meet varying environmental and operational requirements:

• Nitrile (NBR): Commonly used for general-purpose applications where temperatures range between -40°C and +105°C. Oil Seals provides good resistance to mineral oils, greases, and water.

• Viton (FKM): Suitable for high-temperature environments up to 230°C and offers excellent chemical resistance against petroleum products, hydraulic fluids, and ozone exposure.

• PTFE: Known for its exceptional temperature range (-75°C to +260°C) and low coefficient of friction, making it ideal for high-speed applications. PTFE seals can handle aggressive chemicals as well.

• Silicone: Best suited for extreme cold environments down to -90°C and up to 230°C. Silicone seals resist ozone degradation and provide good electrical insulation properties.

Oil seal standards include ISO 6194, DIN 3760/3761, and others which specify dimensions, tolerances, and performance characteristics for different applications. Compliance with these standards ensures that oil seals perform reliably across a wide range of industrial settings.

Selection criteria

Choosing the right oil seal involves evaluating several factors:

• Environmental Conditions: Consider temperature extremes, chemical exposure, and contamination levels to select materials like NBR, Viton, or PTFE.

• Shaft Speed and Pressure: For high-speed applications, spring-loaded seals maintain consistent contact with the shaft. Ensure that the selected seal can handle the maximum operating pressure without failing.

• Seal Size: Oil seals must fit the specific dimensions of your mechanical components accurately to provide an effective barrier against leaks.

UK suppliers

MLC lists verified suppliers from Companies House who manufacture and supply high-quality oil seals for industrial applications. These suppliers adhere to strict quality control measures and offer a range of standard and customised solutions tailored to customer needs.

Suppliers like Trelleborg, SKF, and Seals International are trusted brands that comply with industry standards such as ISO 6194 and DIN 3760/3761. Oil Seals provides technical support and ensure all oil seals meet rigorous testing criteria before delivery.

Common applications

Oil seals find use in numerous industrial sectors:

• Automotive Industry: Engine, transmission, and differential assemblies rely on oil seals to maintain proper lubrication while preventing fluid loss.

• Aerospace Sector: Aircraft engines and landing gear systems utilise high-performance oil seals to withstand extreme conditions encountered during flight operations.

• Manufacturing Plants: Machinery like pumps, compressors, and hydraulic cylinders incorporate oil seals to ensure optimal performance and minimal downtime.

Oil seals play a important role in maintaining the integrity of mechanical systems across diverse industries. By selecting the right seal based on material properties, environmental factors, and operational requirements, engineers can significantly enhance equipment longevity and reliability.