Why is it necessary to prime a screw pump before startup? When can priming be omitted?

2026-03-17 09:51:52

The primary purpose of priming a screw pump before startup is to ensure that the pump and pipeline are fully filled with medium, preventing dry running and cavitation during startup. This protects the pump and seals, extends pump life, and improves pump efficiency. Specifically, priming allows the pump to immediately form a sealed chamber after startup, effectively transferring fluid and generating the required pressure.

However, in certain situations, priming a screw pump may not be necessary. These situations include, but are not limited to:

Self-priming screw pumps: Some screw pumps are designed to be self-priming and have strong self-priming capabilities. These pumps can automatically pump the medium during startup, eliminating the need for pre-priming. However, it should be noted that the self-priming height and time of a self-priming screw pump may be affected by factors such as the medium properties, pipeline layout, and pump performance.

Constantly filled pipelines: In certain applications, such as continuous chemical processes, the medium may remain fully filled in the pipeline and pump. In this case, the screw pump does not require additional priming during startup because the pump and piping are already filled with medium.

Using auxiliary equipment: Sometimes, auxiliary equipment (such as a vacuum pump or ejector) can be used to assist the self-priming of the screw pump. These auxiliary equipment create a negative pressure environment, helping the screw pump to extract the medium. When using such auxiliary equipment, traditional priming may not be necessary.

It is important to note that while priming is not necessary in some cases, it is generally recommended to ensure proper operation and extend the life of the screw pump. Priming is particularly important when using complex media, complex piping layouts, or high performance requirements.

In addition, when priming, the following points should be observed:

Ensure that the medium meets the pump's requirements and avoid using incompatible media.

When priming, open the inlet valve slowly to prevent the medium from impacting the pump.

After priming, check the connections between the pump and piping for leaks and ensure they are properly sealed. Before starting the pump, you should also check whether the direction of rotation of the motor and the pump are consistent to avoid damage caused by reverse rotation.