Factors affecting the performance of self-priming pump

1) Determination of liquid storage volume and liquid storage height:

Liquid storage volume refers to the volume of the liquid part of the pump body after the pump stops, that is, the volume of the pump body below the lower point of the pump inlet, which is mainly a part of the extrusion chamber and the gas-liquid separation chamber. The liquid storage volume should not be less than half of the design flow rate of the pump in seconds. In addition to sufficient liquid storage volume, there must be a certain liquid storage height, which is the height of the pump suction lower to the center of the impeller, usually taken as approximately equal to the impeller radius.

2) Determine the volume of the gas-liquid separation chamber and the outlet height of the pump body:

Gas-liquid separation refers to the part of the pump body outside the pressure chamber, the larger its volume, the better the separation effect of gas and liquid, the faster the separation, but when the volume of the gas-liquid separation chamber is large to a certain extent, the effect will not be significant, and the reverse will make the pump body bulky, so the gas-liquid separation chamber has a better volume value, according to existing experience, its value is equal to or slightly greater than the liquid storage volume. Under the condition that the capacity of the gas-liquid separation chamber is guaranteed, the height of the outlet of the pump body to the center line of the impeller can be determined by the volume of the liquid storage and the volume of the gas-liquid separation chamber in the drawing.

3) Determination of liquid flow rate in the extrusion chamber:

The flow rate of the liquid in the centrifugal self-priming pump is lower than that of the general centrifugal pump, which is about 80-90% of the liquid flow rate in the general centrifugal pump.

4) Determination of the clearance between the diaphragm tongue and the impeller of the extrusion chamber:

For centrifugal self-priming pump, the gap between the tongue and impeller has a great influence on the self-priming performance. The smaller the gap between the tongue and impeller in the upper press chamber, the shorter the self-priming time. If the design is double cochlear chamber, the gap between the lower compartment tongue and the impeller can be determined according to the method of determining the gap between the compartment tongue and the impeller by the general centrifugal pump, that is, the lower compartment tongue is located on the base circle of the cochlear chamber.

5) Turning of impeller rear cover plate:

For external mixing centrifugal self-priming pump, when the impeller cylindrical speed is less than, the self-priming effect is poor, and the self-priming ability can be improved by turning the impeller rear cover plate, which is convenient for the mixing of liquid and gas in the self-priming process. The amount of turning can not be too large, otherwise it will significantly reduce the pump head and efficiency. When the diameter of the impeller back cover is cut, it is reinforced at the upper septum tongue to avoid the circulation of the liquid with bubbles at the cut back cover and affect the self-suction effect.

6) Area of return hole:

For the internal mixing centrifugal self-priming pump, the area of the return hole has a great influence on the self-priming performance, and the area is large, so that more liquid is returned to the impeller through the return hole, so the self-priming time is short, but the vacuum degree is lower. The self-priming time is long when the return hole area is small, and the self-priming is large and the vacuum height is high. In the pump industry, when determining the area of the return hole, the requirements of self-priming time and self-priming height should be considered comprehensively.