Guide to oil seals for your application - ERIKs

Nitrile Butadiene Rubber (NBR, nitrile)

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NBR, also known as nitrile rubber or nitrile, is the most popular material for an oil seal because of its good resistance to many oils and greases, such as mineral grease and hydraulic oil. Depending on their composition, synthetic oils and greases, such as those based on glycol, can damage NBR rubber materials. Depending on the amount of glycol, a PTFE lip seal may be the best choice. NBR is also unable to cope with contact with acids and solvents. The rubber is suitable for oil and grease at temperatures from -35 °C to 100 °C.

Most ERIKS oil seals, such as the types M, MST, R and RST, are made of NBR as standard.

Fluorine rubber (FKM, Viton&#;)

FKM or FPM, which is in well-known brand Viton&#;, can withstand higher liquid temperatures of up to 180 ˚C. FKM is highly resistant to strong acids and bases, as well as to synthetic oils and greases. Glycol-based oil and grease, however, can also damage FKM.

Because of the higher temperature resistance of FKM, this material is also chosen for applications where higher speeds play a role, which raise the temperature at the sealing lip considerably. Usually, using FKM will result in a longer life than using NBR. This compensates the higher price of FKM compared to NBR, as an FKM does not have to be replaced as frequently. The low temperature resistance of standard FKM is limited to -15 ˚C.

Polytetrafluoroethylene (PTFE, Teflon®)

PTFE, which is used in the well-known brand Teflon®, is less commonly used, but it is the preferred material for specific rotating seals in the chemical, food and pharmaceutical industries. This material is notable for having a very low frictional resistance and the best chemical resistance. It can also withstand a very wide range of temperatures in these types of seals; -80 ˚C to 200 ˚C. The shafts on which oil seals with PTFE lips are used require a harder and finer finish. Something like an axle sleeve can also be used to meet this requirement.

EPDM

EPDM oil seals are less common. They are used in solvent, hot water and steam applications, EPDM resists low temperatures down to -50 °C and UV radiation well. Some types of EPDM are also suitable for higher temperatures up to +150 °C. EPDM oil seals are usually available upon request.

VMQ (silicone)

VMQ, also known as silicone, is also used for oil seals, but this is less common because the mechanical strength of VMQ is low and this material has poor wear-resistance This makes it less suitable for dynamic applications, but it can withstand fairly low and high temperatures from -60 °C to 200 °C. Many types of VMQ are also suitable for contact with pharmaceutical and food products, so VMQ is an option worth considering. VMQ oil seals are usually available on request.

The numbers on an oil seal, also known as a shaft seal or rotary seal, provide important information about its dimensions, material, and design specifications. Understanding these numbers is crucial when selecting the right oil seal for a specific application. Here's a breakdown of the typical numbering system used for oil seals:

Shaft Diameter (ID or Inner Diameter):

The first set of numbers usually represents the shaft diameter or the inner diameter (ID) of the oil seal. This measurement is critical because it indicates the size of the shaft around which the oil seal will be installed. For example, if the number is 25, it signifies that the oil seal is designed for a shaft with a 25-millimeter diameter.

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Housing Bore Diameter (OD or Outer Diameter):

The second set of numbers corresponds to the housing bore diameter or the outer diameter (OD) of the oil seal. This measurement is crucial as it indicates the size of the bore or cavity in the housing where the oil seal will be placed. For example, if the number is 40, it means the oil seal is designed to fit into a bore with a 40-millimeter diameter.

Rubber Skeleton Oil Seal

Width (W):

The third set of numbers or letter represents the width of the oil seal. It specifies the radial dimension of the seal, indicating how thick or wide the oil seal is. For example, if the number is 7, it means the oil seal has a width of 7 millimeters.

Lip Type or Designation:

Some oil seals may have additional letters or codes indicating the lip type or special design features. These codes specify the sealing lip material, configuration, or any special features that the oil seal may have. Common lip types include single lip (S), double lip (D), and triple lip (T).

Material Code:

In certain numbering systems, a letter or code may be used to indicate the material composition of the oil seal. Different materials may be chosen based on factors like temperature resistance, chemical compatibility, and application requirements.

For example, if you have an oil seal with the number "25-40-7," it can be interpreted as follows:

Inner Diameter (ID): 25 millimeters

Outer Diameter (OD): 40 millimeters

Width: 7 millimeters

Understanding these numbers is crucial when replacing or specifying oil seals for machinery or equipment. It ensures compatibility with the shaft and housing dimensions and helps maintain effective sealing performance. When in doubt, it's recommended to refer to the manufacturer's documentation or consult with a supplier to ensure the correct oil seal is selected for the intended application.

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