Insufficient depth of 1. suction pipe into oil surface
There is air in the 2. duct or in the pump casing
Intense production of foam by 3. oil return vortex
4. the air dissolved in the oil, the bubbles generated during the working process
Solution:
1. Lend the oil suction pipe and fill the oil tank to raise the liquid level
2. No-load operation
3. Distance between oil suction pipe and oil return pipe
4. Add a partition in the mailbox, defoam the return oil after defoaming through the partition, and add defoaming agent to the oil.