Oil seals, often called a rotary shaft seal or grease seal, closes the gap between stationary and moving components in mechanical equipment — most often rotating shafts — helping prevent lubricant escape and stopping harmful materials, such as dirt, from moving in through the clearance. Oil seals are most commonly used in gearboxes, hydraulic cylinders and related components.
Selecting the Right Oil Seal
Beyond selecting the correct size, the three primary selection criteria are Material, Lip and Case.
Material selection is important to the life of a radial shaft seal. The elastomer’s resistance to temperature, abrasion, chemicals, weather, sunlight and ozone can affect a profile’s longevity and performance. The two most prevalent materials are Nitrile and Viton. Other materials are also available to address specific applications.
Lip selection is driven by the media type, shaft speed, pressure, temperature and contamination parameters. The media used in the majority of applications is either oil and grease. Lip designs generally include a spring when the media is oil because of its higher viscosity as compared to Grease. There is also a double spring design when there is media on both sides of the Oil Seal. Lip designs can also include a secondary lip which purpose is to mitigate particulates from reaching the sealing lip.
‘S’ Lip – single lip with spring. The spring is to ensure sealing of oils versus grease. Used in more benign environments.
‘T’ Lip – dual lip with spring. The lip design includes a secondary dust lip to minimize particulates from entering the sealing region. This is the most common lip design.
‘V’ Lip – single lip without spring. This lip is designed for grease applications because the high viscosity of grease does not require a spring
‘K’ Lip – dual lip without a spring. This lip is designed for grease applications and include a secondary dust lip to minimize particulates from entering the sealing region.
‘D’ Lip – dual lip and dual spring lip. This lip is designed when there is media on both sides of the Oil Seal.
The most common and cost effective case materials are stamped from cold rolled carbon steel. The steel is then phosphate coated to aid in the molding process and to help eliminate corrosion during storage. A simply ‘L’ shaped geometry is the most cost effective case design but a number of case geometries are available to improve rigidity, positioning and removability. Oil Seal cases can also include rubber molded options which address such factors as corrosion, vibration and sealing characteristics.
B2 Case – The most economical design and popular design (simple ‘L’ shape). It has a metal outside diameter.
A2 Case– The A2 design also has a metal outside diameter but includes an inner case which provide structural rigidity. This case design is used when the diameter of the seal is larger and rigidity is required to maintain structural integrity during installation.
C Case– The outside of this case is rubber coated. This design is often used when a seal will be removed frequently or if sealing of bore and oil seal is of concern.
B Case– The B design is the same as the B2 except that a rubber inner coating is added to protect case from media.
BR Case– The BR design is same as B with additional rubber coating on the leading edge of the case. This additional rubber coating is to ensure sealing when the oil seal is seated in the groove.
The Oil Seal size is specified by three dimensions: the rotating shaft diameter, the housing bore diameter, and the width (thickness). Because an oil seal’s purpose, correct size is critical to performance. The inside diameter of Oil seal is sized slightly smaller than the shaft diameter in order to seal lubricants inside and prevent harmful contaminants from entering.
Oil Seals are offered in both metric and inch sizes to ensure the correct fit.
Additional Oil Seal Options:
In addition to the Material, Lip, and Case selections, you can select to have a Stainless Steel Case and a Stainless Steel Spring. In those cases you will find an additional indicator in the part number.
Oil Seal Style Cross Reference Table
Oil Seals are produced by a variety of manufacturers from around the globe. Part number vary greatly with manufacturers, so we have created a quick cross reference guide to cross Oil Seals Lip and Case designs. Sizing and material selection can be made on our ecommerce site or provide to an Inside Sales person when placing an order. See chart below: