Answer: The air compressor oil seal is installed at the inlet end of the air compressor. When the air compressor is running, the seal ring does not bear much pressure, so there will be no leakage. If the outlet check valve is not closed tightly after the air compressor stops, the entire air compressor system will be under high pressure, including the seal ring. Long-term pressure will cause the seal ring to deform and even damage the lip, causing the oil seal to leak.
