Excerpts:
Surface roughness
The surface roughness values of the counterface for radial shaft seals, calculated according to methods described in ISO 4288 (DIN 4768), should be kept within the limits specified in RMA OS-1-1 (table).
The lower value for Ra is a minimum value. Using a lower value will adversely affect the lubricant supply to the sealing lip. The temperature rise caused by inadequate lubrication, particularly at high circumferential speeds, can lead to hardening and cracking of the sealing lip which will eventually lead to premature seal failure. If the counterface is too rough, there will be excessive sealing lip wear and seal service life will be shortened. If the value Rpm is exceeded, the seal will leak or excessive sealing lip wear may occur.
The seal counterface surface should be free of any damage, scratches, cracks, rust or burrs and should be properly protected until final installation.
Replacement
The lip of the replacement seal should not run on the same path as the lip of the old seal. There are several ways to achieve this:
– Rework or replace the counterface (this may entail removing the shaft).
– Install a wear sleeve.
– use a Speedi-Sleeve
– Install a spacing ring in the housing bore between the housing shoulder and the seal (fig).
– Press the new seal to a different depth in a cylindrical opening in the housing, i.e. toward the medium to be sealed.
When choosing a replacement seal, be sure that its design and material correspond to the original seal. In case of doubt, select a seal that meets the operating conditions of the application, and that the seal materials are compatible with the lubricant.
Seals made from a different material should only be used when absolutely necessary. In these cases, the recommendations provided in the table should be followed. The order in which the materials are listed is an indication of their suitability.
If a seal of the same design is not available in the same width as the original, then a somewhat narrower seal can be used, or if the depth of the housing bore allows, a somewhat wider seal can be selected as the replacement.
Another excerpt:
I had A happen on a John Deere grader transmission pump, for no reason it started popping the seals...The problem was excessive wear in the pump bearings causing pressure oil to bear against the seals, which were not high pressure seals..
