Under the action of the skeleton oil seal, the rigidity of the oil film just makes the oil film and the air contact end form a crescent surface, which prevents the leakage of the working medium and realizes the sealing of the rotating shaft. The sealing ability of the oil seal depends on the thickness of the oil film on the sealing surface. If the thickness is too large, the oil seal will leak; if the thickness is too small, dry friction may occur, causing the oil seal and shaft to wear; if there is no oil film between the sealing lip and the shaft, it is easy to cause heat and wear. . Therefore, when installing, it is necessary to apply some oil on the sealing ring, and at the same time ensure that the skeleton oil seal is perpendicular to the axis line. If it is not perpendicular, the sealing lip of the oil seal will drain the lubricating oil from the shaft, which will also lead to excessive sealing of the lip. wear. During operation, the lubricant in the casing seeps out a little, so that it is ideal to form an oil film on the sealing surface.

Leather is probably the oldest of the lip materials still in common use, but the move towards mass production methods has seen a massive increase in the development of synthetic rubbers which lend themselves to accurate and repeatable injection and compression moulding. Nitrile (NBR) is still by far the most common elastomer for “normal” use, whilst Viton® (FKM/FPM) is rapidly replacing Polyacrylate (ACM) and Silicone (VMQ) for high-temperature applications. Viton® also has high resistance to abrasion and chemical attack making it a preferred elastomer. Recent developments in the use of PTFE for Rotary shaft seals has caused widespread interest particularly for high-speed shaft rotation or poor lubrication applications.

Selecting the right oil seal involves comprehensively evaluating your application’s needs and conditions. Below are the key factors to consider when choosing an oil seal:

a) The shaft on which the oil seal is to be mounted should be ground with the surface finish or surface roughness between 0.2 to 0.8 Microns. It is best for the shaft to be hardened atleast to 40 – 45 HRc in order to prevent groove formation on the shaft due to the pressure exerted by the spring.

The garter spring is located at the end of the primary sealing lip and used to apply pressure to the sealing lip against the shaft. Common garter spring material types are:

■Anti-wear agents: Anti-wear agents help protect parts of the engine that are especially susceptible to damage from high temperatures, like cylinder walls, lifters, cams, and piston rings. This additive acts as a protective layer around these components to limit friction in metal-on-metal situations.

HALOGEN

Table 2 b): Common types of oil seals (without spring)