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A: with minor lip
Fundamental things and its importance
No matter the PTFE machining techniques and other processes used in making mechanical parts, they tend to fail due to some reasons. The same thing applies to oil seals. When they are exposed to some factors, they fail. The factors are stated below alongside the solutions.
The hydrodynamic ribsa) have a two-stepped rib configuration provided in one direction on the air face of the lip. Even if the first rib is worn out, the second rib comes into contact with the shaft surface, meaning that this type of oil seal ensures higher sealing performance. Seal with Side Lip A large side lip ensures prevention of entry of dust/water.
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.
Use the right assembly tools

(2) When the ambient temperature is high, polyacrylate or silicon, fluorine, and silicon fluorine rubber should be selected. And should try to lower the oil temperature in the tank. When the operating temperature is too low, cold-resistant rubber should be used.
PTFE is special in that a pre-tensioned spring is not required. This is because the material returns to its original shape when heated, also known as the shape-memory polymers (SMPs) effect. These oil seals are also supplied as integrated parts, where it only needs to be installed as one component.
Several variables must be considered when selecting oil seals. The physical dimensions and materials will vary depending on the environment of use. In addition, oil seals must remain lightweight, compact, and exhibit high self-lubrication performance.