Guide to oil seals for your application - ERIKs

The Ultimate Guide to Oil Seals

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Oil seals play a crucial role across numerous industries by preventing leaks and maintaining the efficiency of machinery. Selecting the ideal oil seal is paramount to ensure smooth and leak-free operations. This guide will help you navigate the key factors in choosing the appropriate oil seal for your specific needs.

Understanding Oil Seal Specifications

The dynamic group of oil seals primarily includes radial shaft seals that enclose a rotating shaft around its circumference. These are commonly referred to as lip seals, but for the scope of this guide, we’ll stick with oil seals.

These oil seals are essential for keeping lubricating oils or greases within machinery, ensuring continuous lubrication of components such as bearings. Oil seals can also secure other substances including liquids, gases, and powdered materials.

An oil seal comprises:

• A metal outer case or one that has a rubber coating
• A sealing lip made from rubber or PTFE
• A spring that varies depending on the type
   

The specially designed lip aids in the effective functioning of the oil seal under forces generated during rotation. Various designs and materials are available to suit different applications—from pumps to gearboxes and wheels. These are prevalent in industries like chemical processing, manufacturing, automotive, food production, and power generation.

Factors in Selecting the Right Oil Seal

Choosing an oil seal requires considering various types and materials available, each tailored for specific applications. The correct size of the oil seal is crucial for optimal performance. Thus, understanding the specific application is key when selecting the right seal.

Standard Shapes and Types of Oil Seals

Standard oil seals must comply with DIN 3760 and ISO 6194 standards. Common standard types include the ERIKS R, RST, M, and MST types, which align with the A, AS, B, and BS types in these standards.

All standard types come equipped with a spring to preload the sealing lip and are suitable for low-pressure applications. For diameters of 500 mm or more, the maximum permissible pressure drops to 0.1 bar.

ERIKS type M (DIN type B) features a single metal casing with a rubber sealing lip. These are often used in original equipment due to cost advantages, although rubber-covered types like R and RST are easier to install as replacements. The MST variant includes a dust lip to prevent contamination, extending its service life.

ERIKS type GV (DIN type C) is a robust version with a double metal casing, ideal for larger diameters in demanding applications. The GVST version also incorporates a dust lip for additional protection.

ERIKS type R (DIN type A) has a rubber outer case which compensates for minor housing damage. The RST version includes a dust lip for extra protection. For environments with acid exposure, types GR and GRST, made with FKM rubber, are preferred.

Special Oil Seal Types

• Rubber fabric outer case: Comparable to types R and RST but lacking a metal reinforcement ring. Often produced from NBR or FKM.

• PTFE Lip seals: Suitable for temperatures from -90 °C to 260 °C and pressures up to 10 bar. Essential in pharmaceutical and food applications, requiring precise shaft finishes.

• Cassette Seals: Ideal for applications needing superior grease or oil retention, commonly used in agricultural machinery and trucks.

The Floating Seal supplier offers a range of specialized sealing solutions.

Materials of Oil Seals

Outer case

• Metal: Typically made from carbon steel but can be upgraded on request.

• Rubber or rubber fabric: The same quality as the sealing lip, reinforced for durability.

Spring

Standard springs are carbon steel, while FKM rubber seals use stainless-steel springs. In rare cases, an O-ring serves as a spring.

Sealing lip

Made of rubber or synthetic materials, the lip material is chosen based on the fluid type and rotational speed. NBR is suitable for speeds up to 12 m/s, while FKM can handle 38 m/s.

Nitrile Butadiene Rubber (NBR)

NBR is widely used due to its resistance to many oils and greases, although not suitable for certain synthetic oils and acids. NBR operates between -35°C and 100°C.

Fluorine rubber (FKM)

Known by the brand Viton™, FKM withstands temperatures up to 180 °C and is more resistant to synthetic oils and acids, making it ideal for high-speed applications.

Oil Seal Sizes

Oil seals cover a wide size range, suitable for shafts from a few millimeters to several meters. Knowing the shaft diameter, housing diameter, and groove width simplifies the selection process. An example dimension might be 6x15x4, indicating compatibility with a 6-mm shaft, 15-mm housing diameter, and 4-mm groove width.

Correct Installation of Oil Seals

After selecting the appropriate oil seal, the next step is to install it properly to avoid damage.

Preparation

Ensure the oil seal, shaft, and bore are clean and free from damage. Smooth surfaces help prevent leaks and damage to the fragile sealing lip.

Installation Steps

Prepare the Shaft

A damage-free shaft is essential for effective oil seal function. Lubricate the shaft, sealing lip, and bore with grease to ease installation and prevent dry running. Cover sharp edges or grooves with oiled paper to safeguard the sealing lip during installation.

Fitting the Oil Seal

Align the oil seal correctly, with the spring facing the medium to be sealed. Press the oil seal into the bore evenly using appropriate tools, avoiding unnecessary force. Proper installation extends the seal's service life and ensures its efficacy.

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