What is the function of an oil seal？

Oil seals are a common term for sealing components, often used in bearings or hydraulic cylinders of various machines. Simply put, they are seals for lubricating oil. Their function is to isolate oil from the external environment, sealing the oil internally and preventing dust from entering externally. They are divided into static seals and dynamic seals.

Static seals

The oil seal sealing interface is a narrow ring band with a width of 0.1-0.2mm. Under the action of preload (usually a spring), there is generally an average radial contact pressure of about 1N/mm2 between the oil seal and the shaft. When the lubricating oil pressure is lower than this pressure value, the oil seal prevents it from leaking to the outside.

Dynamic seals

During normal operation, oil enters the narrow band where the oil seal contacts the shaft through the action of the pump. When the oil enters this contact surface, a hydrodynamic pressure balance is achieved. Now, the oil seal is operating while maintaining a sealing state; this operating state is the lubrication state.

Early oil seal materials were generally leather; soft, elastic, oil-resistant, and widely used. Now the oil seal material is mainly various rubbers. Such as: NBR、ACM、PU、 SILICONE (VMQ / PVMQ), FKM and PTFE，etc…