For the descending gradient of more than 5%, the end connected to the inlet of the oil pump should be high and the oil should not be flat. If it inclines upward, air will remain in the oil inlet pipe, which will reduce the vacuum degree in the oil inlet pipe and oil pump and affect oil absorption. 3. The packing of the oil pump has been worn or pressed too loosely due to long-term use, resulting in a large amount of oil spraying from the gap between the packing and the shaft sleeve of the pump. Therefore, outside air will enter the oil pump from these gaps, which will affect the oil extraction.
4. Due to the long-term potential oil leakage, holes appear in the wall of the oil inlet pipe due to corrosion, and the oil level continues to drop after the oil pump works. When these holes are exposed to the oil level, air enters the civil oil intake pipe from these holes. 5. Cracks appear at the elbow of the oil inlet pipe of Jinhai screw pump, and there is a slight gap between the oil inlet pipe and the oil pump, which may make air enter the oil inlet pipe.