What are the main causes of oil pump leakage?

What are the main causes of oil pump leakage? Oil pump seal manufacturers for you to introduce it:

(1) hydraulic pump spindle oil seal damage or shaft defects, scratches;

(2) excessive internal leakage will increase the pressure at the oil seal and damage or flush out the oil seal;

(3) the drain pipe is too thin and too long, causing oil leakage at the seal;

(4) the external oil pipe of the hydraulic pump is loose, the pipe joint is damaged, and the sealing pad is aging or cracks occur;

(5) the bolt of the variable regulating mechanism becomes loose and the seal is damaged;

(6) cast iron hydraulic pump shell has sand holes or poor welding.