The main reasons for the aging of the reducer skeleton oil seal include material deterioration, high temperature environment, poor lubrication, shaft surface wear, improper installation, and the intrusion of impurities in the working environment. These factors will act alone or together, causing the oil seal to lose elasticity, crack the lip, reduce sealing performance, and eventually cause oil leakage failure.
1. Natural aging and chemical incompatibility of materials
Skeleton oil seals are mostly made of elastomeric materials such as nitrile rubber (NBR) and fluorine rubber (FKM). After long-term use, they will naturally age due to oxidation, thermal degradation and other reasons, with the rubber becoming hard, cracked, and losing elasticity.
If the lubricating oil contains amine additives, it may react chemically with the fluorine element in the fluorine rubber, causing the oil seal material to harden and crack.
The use of oil seal materials that are incompatible with the working medium (such as nitrile rubber used in high temperatures or corrosive environments) will also accelerate aging.
2. High temperature environment accelerates aging
Long-term operation under high-temperature conditions (such as over 80°C) will accelerate the aging of oil seal materials, especially ordinary nitrile rubber oil seals, which have poor temperature resistance and are prone to softening, swelling, and reduced elasticity.
The inside of the reducer generates heat due to friction. If the vent cap is blocked and the box pressure rises, the oil temperature will also rise, further aggravating the aging of the oil seal.
3. Poor lubrication leads to dry friction
Insufficient lubricating oil or blockage of the oil circuit will cause "dry friction" to form between the oil seal lip and the shaft, resulting in high temperature and abnormal wear, causing the lip to be seriously worn and the width to exceed 1/3, resulting in loss of sealing ability.
Lubricating oil contamination (such as metal chips and dust) can also scratch the oil seal lip and damage the sealing structure.
4. Poor journal surface condition
The shaft surface has insufficient smoothness (Ra>1.6μm) or has scratches or grooves, which will pierce the oil seal lip or cause local wear.
If the shaft journal rubs against the aging oil seal for a long time, annular grooves may be worn out, further damaging the seal, forming a vicious cycle of "aging of the oil seal → wear of the shaft → worse sealing".
5. Improper installation causes early failure
During installation, the oil seal is skewed, the lip is flipped, the spring falls off, or the use of inappropriate installation tools will cause structural damage to the oil seal.
If the lip is oriented incorrectly (not toward the oil chamber side), the oil will directly impact the back, causing leakage.
6. Intrusion of external impurities
In a dusty and humid environment, dust, sand, moisture, etc. enter the box through the oil seal gap, which not only pollutes the lubricating oil, but also acts as an abrasive between the oil seal and the shaft, aggravating wear.
The entry of moisture may also cause the lubricating oil to emulsify, reduce the lubrication performance, and accelerate component corrosion.
