When a single - screw pump fails to draw liquids, it can be investigated and resolved from the following aspects:

1. Installation and Startup Issues

Reasons

• The installation height exceeds the self - priming height of the pump. If the installation is too high, the liquid has difficulty overcoming gravity.
• The inlet pipeline has air leakage, which disrupts the vacuum environment inside the pump.
• The pump is started without priming, resulting in insufficient suction force inside the pump.

Solutions

• Re - evaluate the installation location to ensure that the height complies with the regulations.
• Check and seal the interfaces of the inlet pipeline.
• Prime the pump fully in accordance with the operating procedures before startup.

2. Pump - related Malfunctions

Reasons

• Wear and tear between the screw and the bushing deteriorates the sealing performance of the pump chamber, causing liquid backflow.
• Improper matching between the rotor and the stator affects the volume change of the pump chamber.
• The pump shaft is bent or the sealing device is damaged, leading to vibration and leakage.

Solutions

• Replace the screw and the bushing when the wear is severe.
• Check and adjust the assembly of the rotor and the stator.
• Straighten or replace the pump shaft, and replace the damaged sealing parts.

3. Medium and Process - related Problems

Reasons

• Changes in the characteristics of the medium, such as viscosity, density, and temperature, exceed the applicable range of the pump.
• The inlet pressure or flow rate is insufficient to meet the operating requirements of the pump.

Solutions

• Adjust parameters such as the pump speed and pressure according to the medium characteristics, or replace the pump with a more suitable type.
• Increase the inlet pressure by adding pre - conveyance equipment, etc., and stabilize the flow rate.