Selbstansaugen

Selbstansaugen refers to the ability of a pump to draw fluid into its suction line without external priming. This means the pump can operate even if the suction line is initially filled with air. This capability is crucial in applications where it is difficult or impossible to pre-fill the suction line with the liquid being pumped, such as in dewatering operations or when dealing with volatile liquids that might evaporate if left standing in the suction pipe.

Self-priming pumps achieve this by creating a partial vacuum within the pump casing. When the pump is started, the impeller rotates, pushing any liquid already in the casing outwards. This action draws air from the suction line into the casing. The pump then separates this air from the liquid. The air is typically discharged through a separate port or expelled into the atmosphere, while the liquid is recirculated within the pump casing until sufficient vacuum is generated to lift the fluid from the source. Once the suction line is filled with liquid, the pump operates as a conventional centrifugal pump.

Various designs exist for self-priming pumps. Some utilize an internal air-water separator, while others employ a different configuration where the impeller is only partially submerged in liquid during the priming process. The efficiency and speed of self-priming can depend on factors like the pump's design, the length and diameter of the suction line, and the viscosity and temperature of the fluid being pumped. Despite the term, many "self-priming" pumps require an initial small amount of liquid in the casing to initiate the priming cycle.