1. For new or overhauled agricultural machinery, the running in operation and maintenance after running in were not carried out in strict accordance with the technical specifications, so that the metal scraps grinded down inside the machine entered the oil seal, resulting in abrasive wear and early damage of the oil seal.

2. When installing the oil seal, do not pay attention to cleaning, so that impurities and dust into the oil seal, causing accidental wear of the shaft seal.

3. During the installation, the operator knows that there are obvious scratches and burr on the shaft, but still put it into the machine, causing the oil seal to be pulled; or the oil and the shaft are not tightly matched, resulting in oil seal leakage.

4. The quality of oil seal is poor, even the oil seal with obvious defect, aging and crack is installed on the machine, resulting in oil seal leakage.

5. Improper operation during assembly may distort and deform the oil seal, and even the self tightening spring of the oil seal will fall off and lose, resulting in oil leakage.

6. The elastic force of self tightening spring of oil seal is not enough, which makes the sealing performance of oil seal poor and causes oil leakage.

7. Agricultural machinery often overspeed, so that the rotation speed of the oil seal installation of the rotary shaft exceeds the oil seal adaptive speed, resulting in oil seal leakage.