The self priming of the self priming pump means that the suction pipe does not need to be filled with water (but there must be enough water in the pump body) to start, and the function of automatically removing the gas in the suction pipe is performed, and the normal operation is performed after a short time operation.
1、Determination of the storage volume and liquid storage height of the self priming pump:
The liquid storage volume refers to the volume of the liquid part that can be stored in the pump body after the pump is stopped, that is, the volume of the pump body below the lowest point of the pump suction port. This part of the volume is mainly a part of the extrusion chamber and the gas-liquid separation chamber. The storage volume should be no less than half of the pump design flow in seconds [for example, the design flow of the pump, the storage volume is not less, the storage volume is too small [that is, the liquid stored in the pump is too less], so that self priming time grows, even cannot suction too much, making the pump bulky. In addition to having a sufficient liquid storage volume, there must be a certain liquid storage height. The liquid storage height is the height from the lowest point of the pump suction to the center of the impeller, and is usually taken to be approximately equal to the impeller radius.
2、Determination of the volume of the gas-liquid separation chamber and the height of the pump outlet:
Gas-liquid separation refers to the part of the pump body that is pressed out of the chamber. The larger the volume, the better the separation effect of gas and liquid, and the faster the separation, but the volume of the gas-liquid separation chamber is large to a certain extent, and then the effect is inapparent. the reverse side will make the pump body bulky, so the gas-liquid separation chamber has a maximum volume value. According to the experience, its value is equal to or slightly larger than the storage volume. Under the condition of ensuring the volume of the gas-liquid separation chamber, The height of the pump body outlet to the centerline of the impeller can be determined at the time of drawing based on the volume of the reservoir and the volume of the gas-liquid separation chamber.
3、Determine the clearance between the chamber tongue and the impeller:
For the self priming centrifugal pump, the gap between the tongue and the impeller has a great influence on the self priming performance. The smaller the gap between the tongue of the upper pressing chamber and the impeller is, the shorter the self priming time is. If the design is a double worm chamber, the gap between the lower part of the chamber and the impeller can be determined by the method of determining the gap between the chamber tongue and the impeller by a general centrifugal pump.
4、Determination of the liquid flow rate in the extrusion chamber:
The flow rate of the liquid in the chamber of the centrifugal pump type self priming pump is lower than that of the general centrifugal pump, which is about 80-90% of the liquid flow rate in the chamber of the general centrifugal pump.
5、Area of the 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 the liquid returning to the impeller inlet through the return hole is large, so the self priming time is short, but the maximum vacuum of self priming is lowered. The area of the return hole is small and the self priming time is long, and the self priming maximum vacuum height is high. In summary, when determining the area of the return hole, the requirements of self priming time and self priming height should be considered comprehensively.
6、Turning of the impeller rear cover:
For the external mixing centrifugal self priming pump, when the outer diameter speed of the impeller is smaller than the self priming effect, the self priming ability can be improved by turning the rear cover of the impeller, which is convenient for mixing liquid and gas in the self-priming process. The amount of turning should not be too large, otherwise, the pump head and efficiency will be significantly reduced. At that time, the diameter of the rear cover of the impeller was cut, the upper tongue was reinforced to avoid the circulation of the bubbled liquid at the cut back cover, which affected the self priming effect.
Therefore, the user should have a certain understanding of the transport medium, the actual installation situation and the performance technical indicators and structure of the self priming pump when selecting the self priming pump. Properly and rationally choose the applicable self priming pump. The self priming sewage pump is an energy-saving and environmentally friendly product for sewage treatment.