The majority of failures and leakage of oil seals are caused by damage on the sealing lip. Misalignment problem is another essential factor that will influence getting good results which also need strict attention. (A) Eccentricity on shaft and housing, (B) Insufficient concentricity of seal body, both factors will cause serious damages after shaft rotating.
A) ECCENTRICITY ON SHAFT AND HOUSING:
Eccentricity of the housing is not so serious as eccentricity of the shaft (shaft whip), since the latter involves alternating displacement of the sealing lip at a frequency determined by the shaft speed. There is a limit to the speed of recovery of the displaced sealing lip, so that the higher the shaft speed, the lesser the shaft eccentricity which can be accommodated without leakage.
B) INSUFFICIENT CONCENTRICITY OF SEAL BODY:
In many cases, shaft surface will be damaged due to uneven spring force of insufficient concentricity of seal body. Therefore, the permissible eccentricity of the seal O.D. is necessary. See Table 1-4 and Table 1-5.