Also known as a Rotary Shaft Seal, Shaft Seal, Lip Seal, Elastomeric Lip Seal or any variation of these. It is a simple device for excluding dust, dirt, water or any other contaminant whilst retaining lubricant in rotary shaft equipment. Generally, it has been developed as a means of protecting the bearings of rotating shafts.


b) The area where the oil seal is seated is to be plunge ground in order to prevent wear grooves that normally tend to wear out the lip of the oil seal at a faster rate.
An overview of the different standard types of oil seals and their main characteristics is shown below.



They are generally utilised for the following purposes:
From this kind of standard immersion testing, one would expect that bisphenol-cured VDF/HFP/TFE fluoroelastomers would not give good service life as oil seals. Similar tests with other elastomers, such as HNBR, silicone, and acrylic rubbers, show less loss of elongation. However, it is found that, in actual service, FKM shaft seals6 have much longer service life than seals of the other elastomers. In a Japanese study of FKM lip seals, rear crankshaft seals from high-mileage automobiles (70,000–280,000 mi ie, 110,000–450,000 km) were collected and examined. No serious oil leakage was found when the seals were removed from the engines. Some deposits were found around the seal lip and on the garter spring holding the lip against the shaft. No surface cracks were found on the seal lip, and only minor crazing on the crankcase side of the flexure portion of the seal in some samples. The seal compositions were not noted, but most were probably VDF/HFP/TFE elastomers with 68–69% fluorine content.
One of the key benefits of using a square rubber gasket is its flexibility and compressibility, allowing it to conform to irregular surfaces and provide a secure seal. This flexibility also makes it easy to install and remove, making maintenance and repairs more efficient.
Materials Used to Make Oil Seals
Aspects to consider when selecting oil seals
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You may need to take off the air cleaner (See Air filter change ), which may also have pipe connections.
<Seal selection example>
Based on the above flowcharts, the oil seal type that meets the requirements shown in Table 3 would be the type code MHSA or HMSA shown in Table 4.

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