I'm fitting an oil seal to an 8mm shaft with internal pressure seals. The internal pressure seals need the lubrication. However There are occasions where the internal pressure will change creating a pressure differential across the oil seal in excess of of its pressure rating. I figure that the seal will leak a bit as the shaft rotates and eventually normalise. The shaft is run on bearings with minimal runout so I have a few options. I'm assuming that overpressure from either side is likely to be bad. First option is to let thinks take there coarse and hope any overpressure is not excessively damaging and natural leakage around the shaft will equalise it. Alternately, I can arrange for a valve to bleed off the excess pressure, but as this may occur in both directions this could be complex - and possibly unnecessary. I could easily make a metal support either side of the seal lip to prevent excessive deflection - but whether this would exacerbate any damage I have no idea. I could drill a small hole to equalise the pressure but if the pressure differential was sufficient and in the right direction it would cause oil to be pumped out of the sealed area. Another alternative is to fit a membrane to equalise the pressure whilst still maintaining the integrity of the lubricated area. Really the seal is just there to ensure that the lubrication is always present for the main pressure seal so I'm undecided about what precautions to taker if any.
Many thanks for your time
Best Regards
picclock
