The self-priming performance of fluoroplastic alloy chemical centrifugal pump can be said to be the main function that is different from other pumps, but sometimes the self-priming performance of fluoroplastic alloy chemical centrifugal pump is not very good, so why?

1. Determination of storage volume and storage height

The 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 low point of the pump suction port. This part of the volume mainly comes from the extrusion chamber and part of the gas-liquid separation chamber. The storage volume should be not less than half of the pump design flow in seconds [for example, the design flow of the pump, the storage volume is not less than, and the storage volume is too small [that is, the liquid stored in the pump is too small], so that the automatic The suction time becomes longer, and even self-priming is not possible; the disadvantage is that the pump is bulky. In addition to sufficient liquid storage volume, there must also be a certain liquid storage height. The liquid storage height is a height from the suction point of the pump to the center of the impeller, which is usually approximately equal to the radius of the impeller.

2. Determination of 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 separation effect of gas and liquid, and the faster the separation. However, if the volume of the gas-liquid separation chamber is large to a certain extent, increase The effect is not significant, and the reverse side will make the pump body more bulky, so the gas-liquid separation chamber has a volume value, which is equal to or slightly larger than the volume of the liquid storage according to existing experience. , the height from the pump body outlet to the centerline of the impeller can be determined when drawing according to the liquid storage volume and the volume of the gas-liquid separation chamber.

3. Determination of the liquid flow rate in the extrusion chamber

The flow rate of the liquid in the extrusion chamber of the centrifugal pump type fluoroplastic alloy chemical centrifugal pump is lower than that of the general centrifugal pump, which is about 80%~90% of the liquid flow rate in the extrusion chamber of the ordinary centrifugal pump.

4. Determination of the clearance between the separation tongue of the extrusion chamber and the impeller

For centrifugal fluoroplastic alloy chemical centrifugal pumps, the gap between the separator tongue and the impeller still has a great influence on the self-priming performance. It is taken by external mixing; internal mixing is taken. If it is designed as a double volute chamber, the gap between the lower part of the press-out chamber and the impeller can usually be determined according to the general method for determining the gap between the press-out chamber and the impeller of a centrifugal pump, that is, the lower part of the tongue is located at the base circle of the volute chamber. above.

5. Turning of the back cover of the impeller

For the external mixing centrifugal fluoroplastic alloy chemical centrifugal pump, when the outer speed of the impeller is less than the inner speed, the self-priming effect is poor. The method of turning the back cover of the impeller can be used to improve the self-priming capacity of the pump. The reason is that Mixing of liquid and gas during self-priming. The turning amount should not be too large, otherwise it will significantly reduce the head and efficiency of the fluoroplastic alloy chemical centrifugal pump. At the same time as the diameter of the impeller rear cover plate is cut, the upper separation tongue is reinforced to avoid the circulation of the liquid with bubbles at the cut rear cover plate, which will affect the self-priming effect.

6. The area of ​​the return hole

For the internal mixing centrifugal type fluoroplastic alloy chemical centrifugal pump, the area of ​​the recirculation hole has a great influence on the self-priming performance. When the area of ​​the recirculation hole becomes larger, more liquid returns to the impeller through the recirculation hole, so the self-priming time is short. However, the vacuum degree of self-priming and large capacity is reduced; the self-priming time is longer when the area of ​​the return hole is small, and the vacuum height is high when the self-priming capacity is large. In summary, when determining the area of ​​the return hole, it is necessary to comprehensively consider the requirements of the self-priming time and the self-priming height.

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