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15

Apr

Main factors affecting the performance of self-priming non-blocking sewage pump
Main factors affecting the performance of self-priming non-blocking sewage pump:

1.Determination of storage volume and height
Liquid storage volume refers to the volume of liquid 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 press-out chamber and the gas-liquid separation chamber. The storage volume should not be less than half of the pump's design flow in seconds. For example, the pump's design flow is not less than the storage volume. The storage volume is too small (that is, too little liquid is stored in the pump), which makes self-priming time increases, and even cannot self-priming; Too much liquid makes the pump bulky. In addition to a sufficient liquid storage volume, there must also 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, which is usually taken to be approximately equal to the radius of the impeller.

2.Determining the volume of the gas-liquid separation chamber and the height of the pump body outlet
Gas-liquid separation refers to the part of the pump body outside the pressure chamber. The larger the volume, the better the gas-liquid separation effect and the faster the separation,
but when the volume of the gas-liquid separation chamber get larger. It will make the pump bulky, so the gas-liquid separation chamber has an optimal volume value, which is equal to or slightly larger than the liquid storage volume according to existing experience. Under the condition of ensuring the gas-liquid separation chamber capacity, The height from the outlet to the centerline of the impeller can be determined according to the storage volume and the volume of the gas-liquid separation chamber when drawing.
3.Determining the liquid flow velocity in the extruding chamber
The flow rate of liquid in the centrifugal self-priming pump is lower than that of ordinary centrifugal pumps, which is about 80-90% of the liquid velocity in the centrifugal pumps.
4.Determining the clearance between the septum tongue and impeller
For centrifugal self-priming pumps, the gap between the tongue and the impeller has a great impact on the self-priming performance. The smaller the gap between the tongue and the impeller in the upper extruding chamber, the shorter the self-priming time. This gap is usually mixed from the outside; the inside mixed take. If the design is a double volute, the lower part of the gap between the tongue and the impeller can usually be determined according to the determination method of the gap between the tongue and the impeller of the centrifugal pump, that is, the lower tongue is located on the base circle of the volute.

5.Turning of the impeller rear cover
For external mixing centrifugal self-priming pumps, when the impeller outer speed is slow, the self-priming effect is poor. The method of turning the rear cover of the impeller can be used to improve the self-priming ability. The reason is to facilitate the mixing of liquid and gas during the self-priming. The amount of turning should not be too large, otherwise the head and efficiency of the pump will be significantly reduced. At that time, the diameter of the rear cover of the impeller was cut; at that time, the upper tongue was reinforced to prevent the liquid with bubbles from circulating in the cut back cover and affecting the self-priming effect.

6.Area of return hole
For the internal mixing centrifugal self-priming pump, the area of the return hole has a great impact on the self-priming performance. The large area makes the liquid return to the impeller inlet through the return hole, so the self-priming time is short, but the maximum vacuum of the self-priming is reduced; The area of the return hole is small, the self-priming time is long, and the maximum vacuum height of the self-priming is high. Based on the above, when determining the area of the return hole, the requirements of self-priming time and self-priming height must be considered comprehensively.