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Obtaining adequate adhesion of fluoroelastomer compounds to metal inserts is a major consideration in fabrication of shaft seals. Adhesive systems worked out for bisphenol-cured VDF/HFP/TFE elastomers often do not perform adequately for peroxide-curable fluoroelastomers and more base-resistant polymers that contain little or no VDF. The trend toward use of more resistant fluoroelastomers in shaft seals has necessitated considerable effort on compounding and adhesive system development to get adequate bonding of the new materials. Silane-type primers are often used to coat metal inserts; these contain residual active groups such as amine functions that interact with the fluoroelastomer compound to attain good adhesion, especially for VDF/HFP/TFE elastomers. Other adhesive systems, using epoxy compounds or tie-coats, may be necessary for difficult bonding situations.³

The metal case is the exterior (or frame) of the oil seal, the principal function of which is to give rigidity and strength to the seal. The material of the case must be selected depending on the environment where the seals are to be used. Often the metal case is covered by the same rubber material used in the sealing element, which also helps seal the exterior of the oil seal in the housing bore. Common case material types are:

Some gaskets are in two or three pieces dove-tailed together. Make sure the pieces join up properly.

However, when you actually select the oil seal to use, the most important factors are past success history and points of improvement, so it is not necessary to follow this order to the letter.

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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.

Unthinkable in the list of seals are oil seals, which provide a seal against splashing oil. The most important oil seals are used for rotating shafts and valve stem seals. Oil seals are intentionally never completely sealed to lubricate the seals and prevent wear.

Oil seal installation

Oil seals, also known as rotary shaft seals or lip seals, are a specific type of gasket designed to prevent the leakage of oil or other fluids in rotating shafts. 

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What are rotary shaft seals?